feat: add parsing for new links format (#3665)

* feat(share-links): Add protobuf and encode/decode url data methods

* feat(new-links-format): Adds generators for new links format

* feat: add parsing for new links format

* feat: add messenger-level pubkey serialization and tests

* feat: fix and test CreateCommunityURLWithChatKey

* feat: impl and test parseCommunityURLWithChatKey

* feat: fix and test CreateCommunityURLWithData

* feat:  impl and test parseCommunityURLWithData (not working)

* feat: UrlDataResponse as response share urls api

* feat: impl& tested ShareCommunityChannelURLWithChatKey

* feat: impl & tested ParseCommunityChannelURLWithChatKey

* fix: bring urls to new format

* feat: add regexp for community channel urls

* feat: impl & test contact urls with chatKey, Ens and data

* fix: encodeDataURL/encodeDataURL patch from Samyoul

* fix: fix unmarshalling protobufs

* fix: fix minor issues, temporary comment TestParseUserURLWithENS

* fix: allow url to contain extra `#` in the signature

* fix: check signatures with SigToPub

* chore: lint fixes

* fix: encode the signature

* feat: Check provided channelID is Uuid

* fix(share-community-url): Remove if community encrypted scope

* fix: review fixes

* fix: use proto.Unmarshal instead of json.Marshal

* feat(share-urls): Adds TagsIndices to community data

* feat: support tag indices to community url data

---------

Co-authored-by: Boris Melnik <borismelnik@status.im>

go.mod

@@ -75,6 +75,7 @@ require github.com/fogleman/gg v1.3.0
 
 require (
 	github.com/afex/hystrix-go v0.0.0-20180502004556-fa1af6a1f4f5
+	github.com/andybalholm/brotli v1.0.5
 	github.com/gorilla/sessions v1.2.1
 	github.com/ipfs/go-log/v2 v2.5.1
 	github.com/ladydascalie/currency v1.6.0

go.sum

@@ -327,6 +327,8 @@ github.com/anacrolix/utp v0.0.0-20180219060659-9e0e1d1d0572/go.mod h1:MDwc+vsGEq
 github.com/anacrolix/utp v0.1.0 h1:FOpQOmIwYsnENnz7tAGohA+r6iXpRjrq8ssKSre2Cp4=
 github.com/anacrolix/utp v0.1.0/go.mod h1:MDwc+vsGEq7RMw6lr2GKOEqjWny5hO5OZXRVNaBJ2Dk=
 github.com/andreyvit/diff v0.0.0-20170406064948-c7f18ee00883/go.mod h1:rCTlJbsFo29Kk6CurOXKm700vrz8f0KW0JNfpkRJY/8=
+github.com/andybalholm/brotli v1.0.5 h1:8uQZIdzKmjc/iuPu7O2ioW48L81FgatrcpfFmiq/cCs=
+github.com/andybalholm/brotli v1.0.5/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
 github.com/andybalholm/cascadia v1.1.0/go.mod h1:GsXiBklL0woXo1j/WYWtSYYC4ouU9PqHO0sqidkEA4Y=
 github.com/andybalholm/cascadia v1.2.0 h1:vuRCkM5Ozh/BfmsaTm26kbjm0mIOM3yS5Ek/F5h18aE=
 github.com/andybalholm/cascadia v1.2.0/go.mod h1:YCyR8vOZT9aZ1CHEd8ap0gMVm2aFgxBp0T0eFw1RUQY=

protocol/communities/community.go

@@ -374,6 +374,21 @@ func (o *Community) TagsRaw() []string {
 	return o.config.CommunityDescription.Tags
 }
 
+func (o *Community) TagsIndices() []uint32 {
+	var indices []uint32
+	for _, t := range o.config.CommunityDescription.Tags {
+		i := uint32(0)
+		for k := range requests.TagsEmojies {
+			if k == t {
+				indices = append(indices, i)
+			}
+			i++
+		}
+	}
+
+	return indices
+}
+
 func (o *Community) OutroMessage() string {
 	if o != nil &&
 		o.config != nil &&

protocol/errors.go

@@ -5,8 +5,9 @@ import (
 )
 
 var (
-	ErrChatIDEmpty     = errors.New("chat ID is empty")
-	ErrChatNotFound    = errors.New("can't find chat")
-	ErrNotImplemented  = errors.New("not implemented")
-	ErrContactNotFound = errors.New("contact not found")
+	ErrChatIDEmpty      = errors.New("chat ID is empty")
+	ErrChatNotFound     = errors.New("can't find chat")
+	ErrNotImplemented   = errors.New("not implemented")
+	ErrContactNotFound  = errors.New("contact not found")
+	ErrCommunityIDEmpty = errors.New("community ID is empty")
 )

protocol/messenger_share_urls.go

@@ -0,0 +1,522 @@
+package protocol
+
+import (
+	"crypto/ecdsa"
+	"fmt"
+	"regexp"
+	"strings"
+
+	"github.com/golang/protobuf/proto"
+
+	"github.com/status-im/status-go/api/multiformat"
+	"github.com/status-im/status-go/eth-node/crypto"
+	"github.com/status-im/status-go/eth-node/types"
+	"github.com/status-im/status-go/protocol/common"
+	"github.com/status-im/status-go/protocol/communities"
+	"github.com/status-im/status-go/protocol/protobuf"
+	"github.com/status-im/status-go/protocol/requests"
+	"github.com/status-im/status-go/protocol/urls"
+)
+
+type CommunityURLData struct {
+	DisplayName  string   `json:"displayName"`
+	Description  string   `json:"description"`
+	MembersCount uint32   `json:"membersCount"`
+	Color        string   `json:"color"`
+	TagIndices   []uint32 `json:"tagIndices"`
+}
+
+type CommunityChannelURLData struct {
+	Emoji       string `json:"emoji"`
+	DisplayName string `json:"displayName"`
+	Description string `json:"description"`
+	Color       string `json:"color"`
+}
+
+type ContactURLData struct {
+	DisplayName string `json:"displayName"`
+	Description string `json:"description"`
+}
+
+type URLDataResponse struct {
+	Community CommunityURLData        `json:"community"`
+	Channel   CommunityChannelURLData `json:"channel"`
+	Contact   ContactURLData          `json:"contact"`
+}
+
+const baseShareURL = "https://status.app"
+const channelUUIDRegExp = "^[0-9a-f]{8}-[0-9a-f]{4}-[0-5][0-9a-f]{3}-[089ab][0-9a-f]{3}-[0-9a-f]{12}$"
+
+func (m *Messenger) SerializePublicKey(compressedKey types.HexBytes) (string, error) {
+	rawKey, err := crypto.DecompressPubkey(compressedKey)
+	if err != nil {
+		return "", err
+	}
+	pubKey := types.EncodeHex(crypto.FromECDSAPub(rawKey))
+
+	secp256k1Code := "0xe701"
+	base58btc := "z"
+	multiCodecKey := secp256k1Code + strings.TrimPrefix(pubKey, "0x")
+	cpk, err := multiformat.SerializePublicKey(multiCodecKey, base58btc)
+	if err != nil {
+		return "", err
+	}
+	return cpk, nil
+}
+
+func (m *Messenger) DeserializePublicKey(compressedKey string) (types.HexBytes, error) {
+	rawKey, err := multiformat.DeserializePublicKey(compressedKey, "f")
+	if err != nil {
+		return nil, err
+	}
+
+	secp256k1Code := "fe701"
+	pubKeyBytes := "0x" + strings.TrimPrefix(rawKey, secp256k1Code)
+
+	pubKey, err := common.HexToPubkey(pubKeyBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	return crypto.CompressPubkey(pubKey), nil
+}
+
+func (m *Messenger) ShareCommunityURLWithChatKey(communityID types.HexBytes) (string, error) {
+	shortKey, err := m.SerializePublicKey(communityID)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s/c#%s", baseShareURL, shortKey), nil
+}
+
+func (m *Messenger) prepareCommunityData(community *communities.Community) CommunityURLData {
+	return CommunityURLData{
+		DisplayName:  community.Identity().DisplayName,
+		Description:  community.DescriptionText(),
+		MembersCount: uint32(community.MembersCount()),
+		Color:        community.Identity().GetColor(),
+		TagIndices:   community.TagsIndices(),
+	}
+}
+
+func (m *Messenger) parseCommunityURLWithChatKey(urlData string) (*URLDataResponse, error) {
+	communityID, err := m.DeserializePublicKey(urlData)
+	if err != nil {
+		return nil, err
+	}
+
+	community, err := m.GetCommunityByID(communityID)
+	if err != nil {
+		return nil, err
+	}
+
+	if community == nil {
+		return nil, fmt.Errorf("community with communityID %s not found", communityID)
+	}
+
+	return &URLDataResponse{
+		Community: m.prepareCommunityData(community),
+	}, nil
+}
+
+func (m *Messenger) prepareEncodedRawData(rawData []byte, privateKey *ecdsa.PrivateKey) (string, string, error) {
+	encodedData, err := urls.EncodeDataURL(rawData)
+	if err != nil {
+		return "", "", err
+	}
+
+	signature, err := crypto.SignBytes([]byte(encodedData), privateKey)
+	if err != nil {
+		return "", "", err
+	}
+
+	encodedSignature, err := urls.EncodeDataURL(signature)
+	if err != nil {
+		return "", "", err
+	}
+
+	return encodedData, encodedSignature, nil
+}
+
+func (m *Messenger) prepareEncodedCommunityData(community *communities.Community) (string, string, error) {
+	communityProto := &protobuf.Community{
+		DisplayName:  community.Identity().DisplayName,
+		Description:  community.DescriptionText(),
+		MembersCount: uint32(community.MembersCount()),
+		Color:        community.Identity().GetColor(),
+		TagIndices:   community.TagsIndices(),
+	}
+
+	communityData, err := proto.Marshal(communityProto)
+	if err != nil {
+		return "", "", err
+	}
+
+	return m.prepareEncodedRawData(communityData, community.PrivateKey())
+}
+
+func (m *Messenger) ShareCommunityURLWithData(communityID types.HexBytes) (string, error) {
+	community, err := m.GetCommunityByID(communityID)
+	if err != nil {
+		return "", err
+	}
+
+	if community == nil {
+		return "", fmt.Errorf("community with communityID %s not found", communityID)
+	}
+
+	data, signature, err := m.prepareEncodedCommunityData(community)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s/c/%s#%s", baseShareURL, data, signature), nil
+}
+
+func (m *Messenger) verifySignature(data string, rawSignature string) (*ecdsa.PublicKey, error) {
+	signature, err := urls.DecodeDataURL(rawSignature)
+	if err != nil {
+		return nil, err
+	}
+
+	return crypto.SigToPub(crypto.Keccak256([]byte(data)), signature)
+}
+
+func (m *Messenger) parseCommunityURLWithData(data string, signature string) (*URLDataResponse, error) {
+	_, err := m.verifySignature(data, signature)
+	if err != nil {
+		return nil, err
+	}
+
+	communityData, err := urls.DecodeDataURL(data)
+	if err != nil {
+		return nil, err
+	}
+
+	var communityProto protobuf.Community
+	err = proto.Unmarshal(communityData, &communityProto)
+	if err != nil {
+		return nil, err
+	}
+
+	return &URLDataResponse{
+		Community: CommunityURLData{
+			DisplayName:  communityProto.DisplayName,
+			Description:  communityProto.Description,
+			MembersCount: communityProto.MembersCount,
+			Color:        communityProto.Color,
+			TagIndices:   communityProto.TagIndices,
+		},
+	}, nil
+}
+
+func (m *Messenger) ShareCommunityChannelURLWithChatKey(request *requests.CommunityChannelShareURL) (string, error) {
+	if err := request.Validate(); err != nil {
+		return "", err
+	}
+
+	shortKey, err := m.SerializePublicKey(request.CommunityID)
+	if err != nil {
+		return "", err
+	}
+
+	valid, err := regexp.MatchString(channelUUIDRegExp, request.ChannelID)
+	if err != nil {
+		return "", err
+	}
+
+	if !valid {
+		return "", fmt.Errorf("channelID should be UUID, got %s", request.ChannelID)
+	}
+
+	return fmt.Sprintf("%s/cc/%s#%s", baseShareURL, request.ChannelID, shortKey), nil
+}
+
+func (m *Messenger) prepareCommunityChannelData(channel *protobuf.CommunityChat) CommunityChannelURLData {
+	return CommunityChannelURLData{
+		Emoji:       channel.Identity.Emoji,
+		DisplayName: channel.Identity.DisplayName,
+		Description: channel.Identity.Description,
+		Color:       channel.Identity.Color,
+	}
+}
+
+func (m *Messenger) parseCommunityChannelURLWithChatKey(channelID string, publickKey string) (*URLDataResponse, error) {
+	valid, err := regexp.MatchString(channelUUIDRegExp, channelID)
+	if err != nil {
+		return nil, err
+	}
+
+	if !valid {
+		return nil, fmt.Errorf("channelID should be UUID, got %s", channelID)
+	}
+
+	communityID, err := m.DeserializePublicKey(publickKey)
+	if err != nil {
+		return nil, err
+	}
+
+	community, err := m.GetCommunityByID(communityID)
+	if err != nil {
+		return nil, err
+	}
+
+	if community == nil {
+		return nil, fmt.Errorf("community with communityID %s not found", communityID)
+	}
+
+	channel, ok := community.Chats()[channelID]
+	if !ok {
+		return nil, fmt.Errorf("channel with channelID %s not found", channelID)
+	}
+
+	return &URLDataResponse{
+		Community: m.prepareCommunityData(community),
+		Channel:   m.prepareCommunityChannelData(channel),
+	}, nil
+}
+
+func (m *Messenger) prepareEncodedCommunityChannelData(community *communities.Community, channel *protobuf.CommunityChat, channelID string) (string, string, error) {
+	communityProto := &protobuf.Community{
+		DisplayName:  community.Identity().DisplayName,
+		Description:  community.DescriptionText(),
+		MembersCount: uint32(community.MembersCount()),
+		Color:        community.Identity().GetColor(),
+		TagIndices:   community.TagsIndices(),
+	}
+
+	channelProto := &protobuf.Channel{
+		DisplayName: channel.Identity.DisplayName,
+		Description: channel.Identity.Description,
+		Emoji:       channel.Identity.Emoji,
+		Color:       channel.GetIdentity().Color,
+		Community:   communityProto,
+		Uuid:        channelID,
+	}
+
+	channelData, err := proto.Marshal(channelProto)
+	if err != nil {
+		return "", "", err
+	}
+
+	return m.prepareEncodedRawData(channelData, community.PrivateKey())
+}
+
+func (m *Messenger) ShareCommunityChannelURLWithData(request *requests.CommunityChannelShareURL) (string, error) {
+	if err := request.Validate(); err != nil {
+		return "", err
+	}
+
+	valid, err := regexp.MatchString(channelUUIDRegExp, request.ChannelID)
+	if err != nil {
+		return "", err
+	}
+
+	if !valid {
+		return "nil", fmt.Errorf("channelID should be UUID, got %s", request.ChannelID)
+	}
+
+	community, err := m.GetCommunityByID(request.CommunityID)
+	if err != nil {
+		return "", err
+	}
+
+	channel := community.Chats()[request.ChannelID]
+	if channel == nil {
+		return "", fmt.Errorf("channel with channelID %s not found", request.ChannelID)
+	}
+
+	data, signature, err := m.prepareEncodedCommunityChannelData(community, channel, request.ChannelID)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s/cc/%s#%s", baseShareURL, data, signature), nil
+}
+
+func (m *Messenger) parseCommunityChannelURLWithData(data string, signature string) (*URLDataResponse, error) {
+	_, err := m.verifySignature(data, signature)
+	if err != nil {
+		return nil, err
+	}
+
+	channelData, err := urls.DecodeDataURL(data)
+	if err != nil {
+		return nil, err
+	}
+
+	var channelProto protobuf.Channel
+	err = proto.Unmarshal(channelData, &channelProto)
+	if err != nil {
+		return nil, err
+	}
+
+	return &URLDataResponse{
+		Community: CommunityURLData{
+			DisplayName:  channelProto.Community.DisplayName,
+			Description:  channelProto.Community.Description,
+			MembersCount: channelProto.Community.MembersCount,
+			Color:        channelProto.Community.Color,
+			TagIndices:   channelProto.Community.TagIndices,
+		},
+		Channel: CommunityChannelURLData{
+			Emoji:       channelProto.Emoji,
+			DisplayName: channelProto.DisplayName,
+			Description: channelProto.Description,
+			Color:       channelProto.Color,
+		},
+	}, nil
+}
+
+func (m *Messenger) ShareUserURLWithChatKey(contactID string) (string, error) {
+	publicKey, err := common.HexToPubkey(contactID)
+	if err != nil {
+		return "", err
+	}
+
+	shortKey, err := m.SerializePublicKey(crypto.CompressPubkey(publicKey))
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s/u#%s", baseShareURL, shortKey), nil
+}
+
+func (m *Messenger) prepareContactData(contact *Contact) ContactURLData {
+	return ContactURLData{
+		DisplayName: contact.DisplayName,
+	}
+}
+
+func (m *Messenger) parseUserURLWithChatKey(urlData string) (*URLDataResponse, error) {
+	pubKeyBytes, err := m.DeserializePublicKey(urlData)
+	if err != nil {
+		return nil, err
+	}
+
+	pubKey, err := crypto.DecompressPubkey(pubKeyBytes)
+	if err != nil {
+		return nil, err
+	}
+
+	contactID := common.PubkeyToHex(pubKey)
+
+	contact, ok := m.allContacts.Load(contactID)
+	if !ok {
+		return nil, ErrContactNotFound
+	}
+
+	return &URLDataResponse{
+		Contact: m.prepareContactData(contact),
+	}, nil
+}
+
+func (m *Messenger) ShareUserURLWithENS(contactID string) (string, error) {
+	contact, ok := m.allContacts.Load(contactID)
+	if !ok {
+		return "", ErrContactNotFound
+	}
+	return fmt.Sprintf("%s/u#%s", baseShareURL, contact.EnsName), nil
+}
+
+func (m *Messenger) parseUserURLWithENS(ensName string) (*URLDataResponse, error) {
+	// TODO: fetch contact by ens name
+	return nil, fmt.Errorf("not implemented yet")
+}
+
+func (m *Messenger) prepareEncodedUserData(contact *Contact) (string, string, error) {
+	userProto := &protobuf.User{
+		DisplayName: contact.DisplayName,
+	}
+
+	userData, err := proto.Marshal(userProto)
+	if err != nil {
+		return "", "", err
+	}
+
+	return m.prepareEncodedRawData(userData, m.identity)
+}
+
+func (m *Messenger) ShareUserURLWithData(contactID string) (string, error) {
+	contact, ok := m.allContacts.Load(contactID)
+	if !ok {
+		return "", ErrContactNotFound
+	}
+
+	data, signature, err := m.prepareEncodedUserData(contact)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%s/u/%s#%s", baseShareURL, data, signature), nil
+}
+
+func (m *Messenger) parseUserURLWithData(data string, signature string) (*URLDataResponse, error) {
+	_, err := m.verifySignature(data, signature)
+	if err != nil {
+		return nil, err
+	}
+
+	userData, err := urls.DecodeDataURL(data)
+	if err != nil {
+		return nil, err
+	}
+
+	var userProto protobuf.User
+	err = proto.Unmarshal(userData, &userProto)
+	if err != nil {
+		return nil, err
+	}
+
+	return &URLDataResponse{
+		Contact: ContactURLData{
+			DisplayName: userProto.DisplayName,
+			Description: userProto.Description,
+		},
+	}, nil
+}
+
+func (m *Messenger) ParseSharedURL(url string) (*URLDataResponse, error) {
+	if !strings.HasPrefix(url, baseShareURL) {
+		return nil, fmt.Errorf("url should start with '%s'", baseShareURL)
+	}
+
+	urlContents := regexp.MustCompile(`\#`).Split(strings.TrimPrefix(url, baseShareURL+"/"), 2)
+	if len(urlContents) != 2 {
+		return nil, fmt.Errorf("url should contain at least one `#` separator")
+	}
+
+	if urlContents[0] == "c" {
+		return m.parseCommunityURLWithChatKey(urlContents[1])
+	}
+
+	if strings.HasPrefix(urlContents[0], "c/") {
+		return m.parseCommunityURLWithData(strings.TrimPrefix(urlContents[0], "c/"), urlContents[1])
+	}
+
+	if strings.HasPrefix(urlContents[0], "cc/") {
+		first := strings.TrimPrefix(urlContents[0], "cc/")
+
+		isChannel, err := regexp.MatchString(channelUUIDRegExp, first)
+		if err != nil {
+			return nil, err
+		}
+		if isChannel {
+			return m.parseCommunityChannelURLWithChatKey(first, urlContents[1])
+		}
+		return m.parseCommunityChannelURLWithData(first, urlContents[1])
+	}
+
+	if urlContents[0] == "u" {
+		if strings.HasPrefix(urlContents[1], "zQ3sh") {
+			return m.parseUserURLWithChatKey(urlContents[1])
+		}
+		return m.parseUserURLWithENS(urlContents[1])
+	}
+
+	if strings.HasPrefix(urlContents[0], "u/") {
+		return m.parseUserURLWithData(strings.TrimPrefix(urlContents[0], "u/"), urlContents[1])
+	}
+
+	return nil, fmt.Errorf("unhandled shared url: %s", url)
+}

protocol/messenger_share_urls_test.go

@@ -0,0 +1,433 @@
+package protocol
+
+import (
+	"context"
+	"crypto/ecdsa"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+	"go.uber.org/zap"
+
+	gethbridge "github.com/status-im/status-go/eth-node/bridge/geth"
+	"github.com/status-im/status-go/eth-node/crypto"
+	"github.com/status-im/status-go/eth-node/types"
+	"github.com/status-im/status-go/protocol/common"
+	"github.com/status-im/status-go/protocol/communities"
+	"github.com/status-im/status-go/protocol/protobuf"
+	"github.com/status-im/status-go/protocol/requests"
+	"github.com/status-im/status-go/protocol/tt"
+	"github.com/status-im/status-go/protocol/urls"
+	"github.com/status-im/status-go/waku"
+)
+
+func TestMessengerShareUrlsSuite(t *testing.T) {
+	suite.Run(t, new(MessengerShareUrlsSuite))
+}
+
+type MessengerShareUrlsSuite struct {
+	suite.Suite
+	m          *Messenger        // main instance of Messenger
+	privateKey *ecdsa.PrivateKey // private key for the main instance of Messenger
+	// If one wants to send messages between different instances of Messenger,
+	// a single waku service should be shared.
+	shh    types.Waku
+	logger *zap.Logger
+}
+
+func (s *MessengerShareUrlsSuite) SetupTest() {
+	s.logger = tt.MustCreateTestLogger()
+
+	config := waku.DefaultConfig
+	config.MinimumAcceptedPoW = 0
+	shh := waku.New(&config, s.logger)
+	s.shh = gethbridge.NewGethWakuWrapper(shh)
+	s.Require().NoError(shh.Start())
+
+	s.m = s.newMessenger()
+	s.privateKey = s.m.identity
+	_, err := s.m.Start()
+	s.Require().NoError(err)
+}
+
+func (s *MessengerShareUrlsSuite) TearDownTest() {
+	s.Require().NoError(s.m.Shutdown())
+}
+
+func (s *MessengerShareUrlsSuite) newMessenger() *Messenger {
+	privateKey, err := crypto.GenerateKey()
+	s.Require().NoError(err)
+
+	messenger, err := newMessengerWithKey(s.shh, privateKey, s.logger, nil)
+	s.Require().NoError(err)
+	return messenger
+}
+
+func (s *MessengerShareUrlsSuite) createCommunity() *communities.Community {
+	description := &requests.CreateCommunity{
+		Membership:  protobuf.CommunityPermissions_NO_MEMBERSHIP,
+		Name:        "status",
+		Color:       "#ffffff",
+		Description: "status community description",
+	}
+
+	// Create an community chat
+	response, err := s.m.CreateCommunity(description, false)
+	s.Require().NoError(err)
+	s.Require().NotNil(response)
+	return response.Communities()[0]
+}
+
+func (s *MessengerShareUrlsSuite) createContact() (*Messenger, *Contact) {
+	theirMessenger := s.newMessenger()
+	_, err := theirMessenger.Start()
+	s.Require().NoError(err)
+
+	contactID := types.EncodeHex(crypto.FromECDSAPub(&theirMessenger.identity.PublicKey))
+	ensName := "blah.stateofus.eth"
+
+	s.Require().NoError(s.m.ENSVerified(contactID, ensName))
+
+	response, err := s.m.AddContact(context.Background(), &requests.AddContact{ID: contactID})
+	s.Require().NoError(err)
+	s.Require().NotNil(response)
+	s.Require().Len(response.Contacts, 1)
+
+	contact := response.Contacts[0]
+	s.Require().Equal(ensName, contact.EnsName)
+	s.Require().True(contact.ENSVerified)
+
+	return theirMessenger, contact
+}
+
+func (s *MessengerShareUrlsSuite) createCommunityWithChannel() (*communities.Community, *protobuf.CommunityChat, string) {
+	community := s.createCommunity()
+
+	chat := &protobuf.CommunityChat{
+		Permissions: &protobuf.CommunityPermissions{
+			Access: protobuf.CommunityPermissions_NO_MEMBERSHIP,
+		},
+		Identity: &protobuf.ChatIdentity{
+			DisplayName: "status-core",
+			Emoji:       "😎",
+			Description: "status-core community chat",
+		},
+	}
+	response, err := s.m.CreateCommunityChat(community.ID(), chat)
+	s.Require().NoError(err)
+	s.Require().NotNil(response)
+	s.Require().Len(response.Communities(), 1)
+	s.Require().Len(response.Chats(), 1)
+
+	community = response.Communities()[0]
+	s.Require().Len(community.Chats(), 1)
+
+	var channelID string
+	var channel *protobuf.CommunityChat
+
+	for key, value := range community.Chats() {
+		channelID = key
+		channel = value
+		break
+	}
+	s.Require().NotNil(channel)
+	return community, channel, channelID
+}
+
+func (s *MessengerShareUrlsSuite) TestDecodeEncodeDataURL() {
+	ts := [][]byte{
+		[]byte("test data 123"),
+		[]byte("test data 123test data 123test data 123test data 123test data 123"),
+	}
+
+	for i := range ts {
+		encodedData, err := urls.EncodeDataURL(ts[i])
+		s.Require().NoError(err)
+
+		decodedData, err := urls.DecodeDataURL(encodedData)
+		s.Require().NoError(err)
+		s.Require().Equal(ts[i], decodedData)
+	}
+}
+
+func (s *MessengerShareUrlsSuite) TestSerializePublicKey() {
+	key, err := crypto.GenerateKey()
+	s.Require().NoError(err)
+
+	serializedKey, err := s.m.SerializePublicKey(crypto.CompressPubkey(&key.PublicKey))
+
+	s.Require().NoError(err)
+	s.Require().Len(serializedKey, 49)
+	s.Require().True(strings.HasPrefix(serializedKey, "zQ3sh"))
+}
+
+func (s *MessengerShareUrlsSuite) TestDeserializePublicKey() {
+	serializedKey := "zQ3shPyZJnxZK4Bwyx9QsaksNKDYTPmpwPvGSjMYVHoXHeEgB"
+
+	shortKey, err := s.m.DeserializePublicKey(serializedKey)
+
+	s.Require().NoError(err)
+	s.Require().Len(shortKey, 33)
+	s.Require().True(strings.HasPrefix(shortKey.String(), "0x"))
+}
+
+func (s *MessengerShareUrlsSuite) TestParseWrongUrls() {
+	urls := map[string]string{
+		"https://status.appc/#zQ3shYSHp7GoiXaauJMnDcjwU2yNjdzpXLosAWapPS4CFxc11":  "unhandled shared url",
+		"https://status.app/cc#zQ3shYSHp7GoiXaauJMnDcjwU2yNjdzpXLosAWapPS4CFxc11": "unhandled shared url",
+		"https://status.app/a#zQ3shYSHp7GoiXaauJMnDcjwU2yNjdzpXLosAWapPS4CFxc11":  "unhandled shared url",
+		"https://status.app/u/": "url should contain at least one `#` separator",
+		"https://status.im/u#zQ3shYSHp7GoiXaauJMnDcjwU2yNjdzpXLosAWapPS4CFxc11": "url should start with 'https://status.app'",
+	}
+
+	for url, expectedError := range urls {
+		urlData, err := s.m.ParseSharedURL(url)
+		s.Require().Error(err)
+
+		s.Require().True(strings.HasPrefix(err.Error(), expectedError))
+		s.Require().Nil(urlData)
+	}
+}
+
+func (s *MessengerShareUrlsSuite) TestShareCommunityURLWithChatKey() {
+	community := s.createCommunity()
+
+	url, err := s.m.ShareCommunityURLWithChatKey(community.ID())
+	s.Require().NoError(err)
+
+	shortKey, err := s.m.SerializePublicKey(community.ID())
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/c#%s", baseShareURL, shortKey)
+	s.Require().Equal(expectedURL, url)
+}
+
+func (s *MessengerShareUrlsSuite) TestParseCommunityURLWithChatKey() {
+	community := s.createCommunity()
+
+	shortKey, err := s.m.SerializePublicKey(community.ID())
+	s.Require().NoError(err)
+
+	url := fmt.Sprintf("%s/c#%s", baseShareURL, shortKey)
+
+	urlData, err := s.m.ParseSharedURL(url)
+	s.Require().NoError(err)
+	s.Require().NotNil(urlData)
+
+	s.Require().NotNil(urlData.Community)
+	s.Require().Equal(community.Identity().DisplayName, urlData.Community.DisplayName)
+	s.Require().Equal(community.DescriptionText(), urlData.Community.Description)
+	s.Require().Equal(uint32(community.MembersCount()), urlData.Community.MembersCount)
+	s.Require().Equal(community.Identity().GetColor(), urlData.Community.Color)
+	s.Require().Equal(community.TagsIndices(), urlData.Community.TagIndices)
+}
+
+func (s *MessengerShareUrlsSuite) TestShareCommunityURLWithData() {
+	community := s.createCommunity()
+
+	url, err := s.m.ShareCommunityURLWithData(community.ID())
+	s.Require().NoError(err)
+
+	communityData, signature, err := s.m.prepareEncodedCommunityData(community)
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/c/%s#%s", baseShareURL, communityData, signature)
+	s.Require().Equal(expectedURL, url)
+}
+
+func (s *MessengerShareUrlsSuite) TestParseCommunityURLWithData() {
+	community := s.createCommunity()
+
+	communityData, signature, err := s.m.prepareEncodedCommunityData(community)
+	s.Require().NoError(err)
+
+	url := fmt.Sprintf("%s/c/%s#%s", baseShareURL, communityData, signature)
+
+	urlData, err := s.m.ParseSharedURL(url)
+	s.Require().NoError(err)
+	s.Require().NotNil(urlData)
+
+	s.Require().NotNil(urlData.Community)
+	s.Require().Equal(community.Identity().DisplayName, urlData.Community.DisplayName)
+	s.Require().Equal(community.DescriptionText(), urlData.Community.Description)
+	s.Require().Equal(uint32(community.MembersCount()), urlData.Community.MembersCount)
+	s.Require().Equal(community.Identity().GetColor(), urlData.Community.Color)
+	s.Require().Equal(community.TagsIndices(), urlData.Community.TagIndices)
+}
+
+func (s *MessengerShareUrlsSuite) TestShareCommunityChannelURLWithChatKey() {
+	community := s.createCommunity()
+	channelID := "003cdcd5-e065-48f9-b166-b1a94ac75a11"
+
+	request := &requests.CommunityChannelShareURL{
+		CommunityID: community.ID(),
+		ChannelID:   channelID,
+	}
+	url, err := s.m.ShareCommunityChannelURLWithChatKey(request)
+	s.Require().NoError(err)
+
+	shortKey, err := s.m.SerializePublicKey(community.ID())
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/cc/%s#%s", baseShareURL, channelID, shortKey)
+	s.Require().Equal(expectedURL, url)
+}
+
+func (s *MessengerShareUrlsSuite) TestParseCommunityChannelURLWithChatKey() {
+	community, channel, channelID := s.createCommunityWithChannel()
+
+	shortKey, err := s.m.SerializePublicKey(community.ID())
+	s.Require().NoError(err)
+
+	url := fmt.Sprintf("%s/cc/%s#%s", baseShareURL, channelID, shortKey)
+
+	urlData, err := s.m.ParseSharedURL(url)
+	s.Require().NoError(err)
+	s.Require().NotNil(urlData)
+
+	s.Require().NotNil(urlData.Community)
+	s.Require().Equal(community.Identity().DisplayName, urlData.Community.DisplayName)
+	s.Require().Equal(community.DescriptionText(), urlData.Community.Description)
+	s.Require().Equal(uint32(community.MembersCount()), urlData.Community.MembersCount)
+	s.Require().Equal(community.Identity().GetColor(), urlData.Community.Color)
+	s.Require().Equal(community.TagsIndices(), urlData.Community.TagIndices)
+
+	s.Require().NotNil(urlData.Channel)
+	s.Require().Equal(channel.Identity.Emoji, urlData.Channel.Emoji)
+	s.Require().Equal(channel.Identity.DisplayName, urlData.Channel.DisplayName)
+	s.Require().Equal(channel.Identity.Color, urlData.Channel.Color)
+}
+
+func (s *MessengerShareUrlsSuite) TestShareCommunityChannelURLWithData() {
+	community, channel, channelID := s.createCommunityWithChannel()
+
+	request := &requests.CommunityChannelShareURL{
+		CommunityID: community.ID(),
+		ChannelID:   channelID,
+	}
+	url, err := s.m.ShareCommunityChannelURLWithData(request)
+	s.Require().NoError(err)
+
+	communityData, signature, err := s.m.prepareEncodedCommunityChannelData(community, channel, channelID)
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/cc/%s#%s", baseShareURL, communityData, signature)
+	s.Require().Equal(expectedURL, url)
+}
+
+func (s *MessengerShareUrlsSuite) TestParseCommunityChannelURLWithData() {
+	community, channel, channelID := s.createCommunityWithChannel()
+
+	communityChannelData, signature, err := s.m.prepareEncodedCommunityChannelData(community, channel, channelID)
+	s.Require().NoError(err)
+
+	url := fmt.Sprintf("%s/cc/%s#%s", baseShareURL, communityChannelData, signature)
+
+	urlData, err := s.m.ParseSharedURL(url)
+	s.Require().NoError(err)
+	s.Require().NotNil(urlData)
+
+	s.Require().NotNil(urlData.Community)
+	s.Require().Equal(community.Identity().DisplayName, urlData.Community.DisplayName)
+	s.Require().Equal(community.DescriptionText(), urlData.Community.Description)
+	s.Require().Equal(uint32(community.MembersCount()), urlData.Community.MembersCount)
+	s.Require().Equal(community.Identity().GetColor(), urlData.Community.Color)
+	s.Require().Equal(community.TagsIndices(), urlData.Community.TagIndices)
+
+	s.Require().NotNil(urlData.Channel)
+	s.Require().Equal(channel.Identity.Emoji, urlData.Channel.Emoji)
+	s.Require().Equal(channel.Identity.DisplayName, urlData.Channel.DisplayName)
+	s.Require().Equal(channel.Identity.Color, urlData.Channel.Color)
+}
+
+func (s *MessengerShareUrlsSuite) TestShareUserURLWithChatKey() {
+	_, contact := s.createContact()
+
+	url, err := s.m.ShareUserURLWithChatKey(contact.ID)
+	s.Require().NoError(err)
+
+	publicKey, err := common.HexToPubkey(contact.ID)
+	s.Require().NoError(err)
+
+	shortKey, err := s.m.SerializePublicKey(crypto.CompressPubkey(publicKey))
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/u#%s", baseShareURL, shortKey)
+	s.Require().Equal(expectedURL, url)
+}
+
+func (s *MessengerShareUrlsSuite) TestParseUserURLWithChatKey() {
+	_, contact := s.createContact()
+
+	publicKey, err := common.HexToPubkey(contact.ID)
+	s.Require().NoError(err)
+
+	shortKey, err := s.m.SerializePublicKey(crypto.CompressPubkey(publicKey))
+	s.Require().NoError(err)
+
+	url := fmt.Sprintf("%s/u#%s", baseShareURL, shortKey)
+
+	urlData, err := s.m.ParseSharedURL(url)
+	s.Require().NoError(err)
+	s.Require().NotNil(urlData)
+
+	s.Require().NotNil(urlData.Contact)
+	s.Require().Equal(contact.DisplayName, urlData.Contact.DisplayName)
+	s.Require().Equal(contact.Bio, urlData.Contact.DisplayName)
+}
+
+func (s *MessengerShareUrlsSuite) TestShareUserURLWithENS() {
+	_, contact := s.createContact()
+
+	url, err := s.m.ShareUserURLWithENS(contact.ID)
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/u#%s", baseShareURL, contact.EnsName)
+	s.Require().Equal(expectedURL, url)
+}
+
+// TODO: ens in the next ticket
+// func (s *MessengerShareUrlsSuite) TestParseUserURLWithENS() {
+// 	_, contact := s.createContact()
+
+// 	url := fmt.Sprintf("%s/u#%s", baseShareURL, contact.EnsName)
+
+// 	urlData, err := s.m.ParseSharedURL(url)
+// 	s.Require().NoError(err)
+// 	s.Require().NotNil(urlData)
+
+// 	s.Require().NotNil(urlData.Contact)
+// 	s.Require().Equal(contact.DisplayName, urlData.Contact.DisplayName)
+//  s.Require().Equal(contact.Bio, urlData.Contact.DisplayName)
+// }
+
+func (s *MessengerShareUrlsSuite) TestShareUserURLWithData() {
+	_, contact := s.createContact()
+
+	url, err := s.m.ShareUserURLWithData(contact.ID)
+	s.Require().NoError(err)
+
+	userData, signature, err := s.m.prepareEncodedUserData(contact)
+	s.Require().NoError(err)
+
+	expectedURL := fmt.Sprintf("%s/u/%s#%s", baseShareURL, userData, signature)
+	s.Require().Equal(expectedURL, url)
+}
+
+func (s *MessengerShareUrlsSuite) TestParseUserURLWithData() {
+	_, contact := s.createContact()
+
+	userData, signature, err := s.m.prepareEncodedUserData(contact)
+	s.Require().NoError(err)
+
+	url := fmt.Sprintf("%s/u/%s#%s", baseShareURL, userData, signature)
+
+	urlData, err := s.m.ParseSharedURL(url)
+	s.Require().NoError(err)
+	s.Require().NotNil(urlData)
+
+	s.Require().NotNil(urlData.Contact)
+	s.Require().Equal(contact.DisplayName, urlData.Contact.DisplayName)
+	s.Require().Equal(contact.Bio, urlData.Contact.Description)
+}

protocol/protobuf/service.go

@@ -4,7 +4,7 @@ import (
 	"github.com/golang/protobuf/proto"
 )
 
-//go:generate protoc --go_out=. ./chat_message.proto ./application_metadata_message.proto ./membership_update_message.proto ./command.proto ./contact.proto ./pairing.proto ./push_notifications.proto ./emoji_reaction.proto ./enums.proto ./group_chat_invitation.proto ./chat_identity.proto ./communities.proto ./pin_message.proto ./anon_metrics.proto ./status_update.proto ./sync_settings.proto ./contact_verification.proto ./community_admin_update.proto
+//go:generate protoc --go_out=. ./chat_message.proto ./application_metadata_message.proto ./membership_update_message.proto ./command.proto ./contact.proto ./pairing.proto ./push_notifications.proto ./emoji_reaction.proto ./enums.proto ./group_chat_invitation.proto ./chat_identity.proto ./communities.proto ./pin_message.proto ./anon_metrics.proto ./status_update.proto ./sync_settings.proto ./contact_verification.proto ./community_admin_update.proto ./url_data.proto
 
 func Unmarshal(payload []byte) (*ApplicationMetadataMessage, error) {
 	var message ApplicationMetadataMessage

protocol/protobuf/url_data.pb.go

@@ -0,0 +1,353 @@
+// Code generated by protoc-gen-go. DO NOT EDIT.
+// source: url_data.proto
+
+package protobuf
+
+import (
+	fmt "fmt"
+	proto "github.com/golang/protobuf/proto"
+	math "math"
+)
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+// A compilation error at this line likely means your copy of the
+// proto package needs to be updated.
+const _ = proto.ProtoPackageIsVersion3 // please upgrade the proto package
+
+type Community struct {
+	DisplayName          string   `protobuf:"bytes,1,opt,name=display_name,json=displayName,proto3" json:"display_name,omitempty"`
+	Description          string   `protobuf:"bytes,2,opt,name=description,proto3" json:"description,omitempty"`
+	MembersCount         uint32   `protobuf:"varint,3,opt,name=members_count,json=membersCount,proto3" json:"members_count,omitempty"`
+	Color                string   `protobuf:"bytes,4,opt,name=color,proto3" json:"color,omitempty"`
+	TagIndices           []uint32 `protobuf:"varint,5,rep,packed,name=tag_indices,json=tagIndices,proto3" json:"tag_indices,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *Community) Reset()         { *m = Community{} }
+func (m *Community) String() string { return proto.CompactTextString(m) }
+func (*Community) ProtoMessage()    {}
+func (*Community) Descriptor() ([]byte, []int) {
+	return fileDescriptor_5f1e15b5f0115710, []int{0}
+}
+
+func (m *Community) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Community.Unmarshal(m, b)
+}
+func (m *Community) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Community.Marshal(b, m, deterministic)
+}
+func (m *Community) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Community.Merge(m, src)
+}
+func (m *Community) XXX_Size() int {
+	return xxx_messageInfo_Community.Size(m)
+}
+func (m *Community) XXX_DiscardUnknown() {
+	xxx_messageInfo_Community.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Community proto.InternalMessageInfo
+
+func (m *Community) GetDisplayName() string {
+	if m != nil {
+		return m.DisplayName
+	}
+	return ""
+}
+
+func (m *Community) GetDescription() string {
+	if m != nil {
+		return m.Description
+	}
+	return ""
+}
+
+func (m *Community) GetMembersCount() uint32 {
+	if m != nil {
+		return m.MembersCount
+	}
+	return 0
+}
+
+func (m *Community) GetColor() string {
+	if m != nil {
+		return m.Color
+	}
+	return ""
+}
+
+func (m *Community) GetTagIndices() []uint32 {
+	if m != nil {
+		return m.TagIndices
+	}
+	return nil
+}
+
+type Channel struct {
+	DisplayName          string     `protobuf:"bytes,1,opt,name=display_name,json=displayName,proto3" json:"display_name,omitempty"`
+	Description          string     `protobuf:"bytes,2,opt,name=description,proto3" json:"description,omitempty"`
+	Emoji                string     `protobuf:"bytes,3,opt,name=emoji,proto3" json:"emoji,omitempty"`
+	Color                string     `protobuf:"bytes,4,opt,name=color,proto3" json:"color,omitempty"`
+	Community            *Community `protobuf:"bytes,5,opt,name=community,proto3" json:"community,omitempty"`
+	Uuid                 string     `protobuf:"bytes,6,opt,name=uuid,proto3" json:"uuid,omitempty"`
+	XXX_NoUnkeyedLiteral struct{}   `json:"-"`
+	XXX_unrecognized     []byte     `json:"-"`
+	XXX_sizecache        int32      `json:"-"`
+}
+
+func (m *Channel) Reset()         { *m = Channel{} }
+func (m *Channel) String() string { return proto.CompactTextString(m) }
+func (*Channel) ProtoMessage()    {}
+func (*Channel) Descriptor() ([]byte, []int) {
+	return fileDescriptor_5f1e15b5f0115710, []int{1}
+}
+
+func (m *Channel) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_Channel.Unmarshal(m, b)
+}
+func (m *Channel) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_Channel.Marshal(b, m, deterministic)
+}
+func (m *Channel) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_Channel.Merge(m, src)
+}
+func (m *Channel) XXX_Size() int {
+	return xxx_messageInfo_Channel.Size(m)
+}
+func (m *Channel) XXX_DiscardUnknown() {
+	xxx_messageInfo_Channel.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_Channel proto.InternalMessageInfo
+
+func (m *Channel) GetDisplayName() string {
+	if m != nil {
+		return m.DisplayName
+	}
+	return ""
+}
+
+func (m *Channel) GetDescription() string {
+	if m != nil {
+		return m.Description
+	}
+	return ""
+}
+
+func (m *Channel) GetEmoji() string {
+	if m != nil {
+		return m.Emoji
+	}
+	return ""
+}
+
+func (m *Channel) GetColor() string {
+	if m != nil {
+		return m.Color
+	}
+	return ""
+}
+
+func (m *Channel) GetCommunity() *Community {
+	if m != nil {
+		return m.Community
+	}
+	return nil
+}
+
+func (m *Channel) GetUuid() string {
+	if m != nil {
+		return m.Uuid
+	}
+	return ""
+}
+
+type User struct {
+	DisplayName          string   `protobuf:"bytes,1,opt,name=display_name,json=displayName,proto3" json:"display_name,omitempty"`
+	Description          string   `protobuf:"bytes,2,opt,name=description,proto3" json:"description,omitempty"`
+	Color                string   `protobuf:"bytes,3,opt,name=color,proto3" json:"color,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *User) Reset()         { *m = User{} }
+func (m *User) String() string { return proto.CompactTextString(m) }
+func (*User) ProtoMessage()    {}
+func (*User) Descriptor() ([]byte, []int) {
+	return fileDescriptor_5f1e15b5f0115710, []int{2}
+}
+
+func (m *User) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_User.Unmarshal(m, b)
+}
+func (m *User) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_User.Marshal(b, m, deterministic)
+}
+func (m *User) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_User.Merge(m, src)
+}
+func (m *User) XXX_Size() int {
+	return xxx_messageInfo_User.Size(m)
+}
+func (m *User) XXX_DiscardUnknown() {
+	xxx_messageInfo_User.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_User proto.InternalMessageInfo
+
+func (m *User) GetDisplayName() string {
+	if m != nil {
+		return m.DisplayName
+	}
+	return ""
+}
+
+func (m *User) GetDescription() string {
+	if m != nil {
+		return m.Description
+	}
+	return ""
+}
+
+func (m *User) GetColor() string {
+	if m != nil {
+		return m.Color
+	}
+	return ""
+}
+
+type URLData struct {
+	// Community, Channel, or User
+	Content              []byte   `protobuf:"bytes,1,opt,name=content,proto3" json:"content,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *URLData) Reset()         { *m = URLData{} }
+func (m *URLData) String() string { return proto.CompactTextString(m) }
+func (*URLData) ProtoMessage()    {}
+func (*URLData) Descriptor() ([]byte, []int) {
+	return fileDescriptor_5f1e15b5f0115710, []int{3}
+}
+
+func (m *URLData) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_URLData.Unmarshal(m, b)
+}
+func (m *URLData) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_URLData.Marshal(b, m, deterministic)
+}
+func (m *URLData) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_URLData.Merge(m, src)
+}
+func (m *URLData) XXX_Size() int {
+	return xxx_messageInfo_URLData.Size(m)
+}
+func (m *URLData) XXX_DiscardUnknown() {
+	xxx_messageInfo_URLData.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_URLData proto.InternalMessageInfo
+
+func (m *URLData) GetContent() []byte {
+	if m != nil {
+		return m.Content
+	}
+	return nil
+}
+
+// Field on CommunityDescription, CommunityChat and ContactCodeAdvertisement
+type URLParams struct {
+	EncodedUrlData string `protobuf:"bytes,1,opt,name=encoded_url_data,json=encodedUrlData,proto3" json:"encoded_url_data,omitempty"`
+	// Signature of encoded URL data
+	EncodedSignature     string   `protobuf:"bytes,2,opt,name=encoded_signature,json=encodedSignature,proto3" json:"encoded_signature,omitempty"`
+	XXX_NoUnkeyedLiteral struct{} `json:"-"`
+	XXX_unrecognized     []byte   `json:"-"`
+	XXX_sizecache        int32    `json:"-"`
+}
+
+func (m *URLParams) Reset()         { *m = URLParams{} }
+func (m *URLParams) String() string { return proto.CompactTextString(m) }
+func (*URLParams) ProtoMessage()    {}
+func (*URLParams) Descriptor() ([]byte, []int) {
+	return fileDescriptor_5f1e15b5f0115710, []int{4}
+}
+
+func (m *URLParams) XXX_Unmarshal(b []byte) error {
+	return xxx_messageInfo_URLParams.Unmarshal(m, b)
+}
+func (m *URLParams) XXX_Marshal(b []byte, deterministic bool) ([]byte, error) {
+	return xxx_messageInfo_URLParams.Marshal(b, m, deterministic)
+}
+func (m *URLParams) XXX_Merge(src proto.Message) {
+	xxx_messageInfo_URLParams.Merge(m, src)
+}
+func (m *URLParams) XXX_Size() int {
+	return xxx_messageInfo_URLParams.Size(m)
+}
+func (m *URLParams) XXX_DiscardUnknown() {
+	xxx_messageInfo_URLParams.DiscardUnknown(m)
+}
+
+var xxx_messageInfo_URLParams proto.InternalMessageInfo
+
+func (m *URLParams) GetEncodedUrlData() string {
+	if m != nil {
+		return m.EncodedUrlData
+	}
+	return ""
+}
+
+func (m *URLParams) GetEncodedSignature() string {
+	if m != nil {
+		return m.EncodedSignature
+	}
+	return ""
+}
+
+func init() {
+	proto.RegisterType((*Community)(nil), "protobuf.Community")
+	proto.RegisterType((*Channel)(nil), "protobuf.Channel")
+	proto.RegisterType((*User)(nil), "protobuf.User")
+	proto.RegisterType((*URLData)(nil), "protobuf.URLData")
+	proto.RegisterType((*URLParams)(nil), "protobuf.URLParams")
+}
+
+func init() {
+	proto.RegisterFile("url_data.proto", fileDescriptor_5f1e15b5f0115710)
+}
+
+var fileDescriptor_5f1e15b5f0115710 = []byte{
+	// 342 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02, 0xff, 0xac, 0x92, 0xb1, 0x4e, 0xc3, 0x30,
+	0x10, 0x86, 0x15, 0xda, 0xb4, 0xe4, 0xd2, 0x54, 0x60, 0x3a, 0x78, 0x23, 0xa4, 0x4b, 0x24, 0xa4,
+	0x20, 0x60, 0x64, 0xa3, 0x2c, 0x48, 0x15, 0x42, 0x46, 0x59, 0x58, 0x22, 0x27, 0x31, 0xc5, 0x28,
+	0xb6, 0x2b, 0xc7, 0x19, 0xfa, 0x4e, 0xbc, 0x04, 0x6f, 0x86, 0x70, 0x62, 0xca, 0xc2, 0xd6, 0x29,
+	0x77, 0x9f, 0x4e, 0x7f, 0x3e, 0xfd, 0x32, 0xcc, 0x3b, 0xdd, 0x14, 0x35, 0x35, 0x34, 0xdb, 0x6a,
+	0x65, 0x14, 0x3a, 0xb6, 0x9f, 0xb2, 0x7b, 0x4b, 0x3e, 0x3d, 0x08, 0x56, 0x4a, 0x88, 0x4e, 0x72,
+	0xb3, 0x43, 0x17, 0x30, 0xab, 0x79, 0xbb, 0x6d, 0xe8, 0xae, 0x90, 0x54, 0x30, 0xec, 0xc5, 0x5e,
+	0x1a, 0x90, 0x70, 0x60, 0x4f, 0x54, 0x30, 0x14, 0x43, 0x58, 0xb3, 0xb6, 0xd2, 0x7c, 0x6b, 0xb8,
+	0x92, 0xf8, 0x68, 0xb8, 0xd8, 0x23, 0xb4, 0x84, 0x48, 0x30, 0x51, 0x32, 0xdd, 0x16, 0x95, 0xea,
+	0xa4, 0xc1, 0xa3, 0xd8, 0x4b, 0x23, 0x32, 0x1b, 0xe0, 0xea, 0x87, 0xa1, 0x05, 0xf8, 0x95, 0x6a,
+	0x94, 0xc6, 0x63, 0x1b, 0xd0, 0x2f, 0xe8, 0x1c, 0x42, 0x43, 0x37, 0x05, 0x97, 0x35, 0xaf, 0x58,
+	0x8b, 0xfd, 0x78, 0x94, 0x46, 0x04, 0x0c, 0xdd, 0x3c, 0xf6, 0x24, 0xf9, 0xf2, 0x60, 0xba, 0x7a,
+	0xa7, 0x52, 0xb2, 0xe6, 0x30, 0xb2, 0x0b, 0xf0, 0x99, 0x50, 0x1f, 0xdc, 0x4a, 0x06, 0xa4, 0x5f,
+	0xfe, 0xb1, 0xbb, 0x86, 0xa0, 0x72, 0x55, 0x61, 0x3f, 0xf6, 0xd2, 0xf0, 0xe6, 0x2c, 0x73, 0x4d,
+	0x66, 0xbf, 0x2d, 0x92, 0xfd, 0x15, 0x42, 0x30, 0xee, 0x3a, 0x5e, 0xe3, 0x89, 0xcd, 0xb1, 0x73,
+	0x42, 0x61, 0x9c, 0xb7, 0x4c, 0x1f, 0xcc, 0xbf, 0x37, 0x1d, 0xfd, 0x31, 0x4d, 0x96, 0x30, 0xcd,
+	0xc9, 0xfa, 0x81, 0x1a, 0x8a, 0x30, 0x4c, 0x2b, 0x25, 0x0d, 0x93, 0xc6, 0xfe, 0x60, 0x46, 0xdc,
+	0x9a, 0x94, 0x10, 0xe4, 0x64, 0xfd, 0x4c, 0x35, 0x15, 0x2d, 0x4a, 0xe1, 0x84, 0xc9, 0x4a, 0xd5,
+	0xac, 0x2e, 0xdc, 0x5b, 0x19, 0x84, 0xe6, 0x03, 0xcf, 0x75, 0x63, 0x03, 0x2f, 0xe1, 0xd4, 0x5d,
+	0xb6, 0x7c, 0x23, 0xa9, 0xe9, 0x34, 0x1b, 0xcc, 0x5c, 0xc4, 0x8b, 0xe3, 0xf7, 0xd1, 0x6b, 0x98,
+	0x5d, 0xdd, 0xb9, 0x8e, 0xca, 0x89, 0x9d, 0x6e, 0xbf, 0x03, 0x00, 0x00, 0xff, 0xff, 0xe0, 0xcf,
+	0x99, 0x77, 0x90, 0x02, 0x00, 0x00,
+}

protocol/protobuf/url_data.proto

@@ -0,0 +1,39 @@
+syntax = "proto3";
+
+option go_package = "./;protobuf";
+package protobuf;
+
+message Community {
+ string display_name = 1;
+ string description = 2;
+ uint32 members_count = 3;
+ string color = 4;
+ repeated uint32 tag_indices = 5;
+}
+
+message Channel {
+ string display_name = 1;
+ string description = 2;
+ string emoji = 3;
+ string color = 4;
+ Community community = 5;
+ string uuid = 6;
+}
+
+message User {
+ string display_name = 1;
+ string description = 2;
+ string color = 3;
+}
+
+message URLData {
+ // Community, Channel, or User
+ bytes content = 1;
+}
+
+// Field on CommunityDescription, CommunityChat and ContactCodeAdvertisement
+message URLParams {
+ string encoded_url_data = 1;
+ // Signature of encoded URL data
+ string encoded_signature = 2;
+}

protocol/requests/community_channel_share_url.go

@@ -0,0 +1,24 @@
+package requests
+
+import (
+	"errors"
+
+	"github.com/status-im/status-go/eth-node/types"
+)
+
+var (
+	ErrCommunityChannelShareURLCommunityInvalidID = errors.New("check-permission-to-join-community: invalid id")
+)
+
+type CommunityChannelShareURL struct {
+	CommunityID types.HexBytes
+	ChannelID   string
+}
+
+func (r *CommunityChannelShareURL) Validate() error {
+	if len(r.CommunityID) == 0 {
+		return ErrCheckPermissionToJoinCommunityInvalidID
+	}
+
+	return nil
+}

protocol/urls/urls.go

@@ -293,3 +293,11 @@ func GetLinkPreviewData(link string) (previewData LinkPreviewData, err error) {
 		return previewData, fmt.Errorf("link %s isn't whitelisted. Hostname - %s", link, u.Hostname())
 	}
 }
+
+func EncodeDataURL(data []byte) (string, error) {
+	return encodeDataURL(data)
+}
+
+func DecodeDataURL(data string) ([]byte, error) {
+	return decodeDataURL(data)
+}

protocol/urls/utils.go

@@ -1,8 +1,12 @@
 package urls
 
 import (
+	"bytes"
+	"encoding/base64"
 	"strings"
 	"unicode/utf8"
+
+	"github.com/andybalholm/brotli"
 )
 
 const (
@@ -52,3 +56,36 @@ func stripHTMLTags(s string) string {
 	s = builder.String()
 	return s
 }
+
+func encodeDataURL(data []byte) (string, error) {
+	bb := bytes.NewBuffer([]byte{})
+	writer := brotli.NewWriter(bb)
+	_, err := writer.Write(data)
+	if err != nil {
+		return "", err
+	}
+
+	err = writer.Close()
+	if err != nil {
+		return "", err
+	}
+
+	return base64.URLEncoding.EncodeToString(bb.Bytes()), nil
+}
+
+func decodeDataURL(data string) ([]byte, error) {
+	decoded, err := base64.URLEncoding.DecodeString(data)
+	if err != nil {
+		return nil, err
+	}
+
+	output := make([]byte, 4096)
+	bb := bytes.NewBuffer(decoded)
+	reader := brotli.NewReader(bb)
+	n, err := reader.Read(output)
+	if err != nil {
+		return nil, err
+	}
+
+	return output[:n], nil
+}

services/ext/api.go

@@ -1337,6 +1337,38 @@ func (api *PublicAPI) CheckAllCommunityChannelsPermissions(request *requests.Che
 	return api.service.messenger.CheckAllCommunityChannelsPermissions(request)
 }
 
+func (api *PublicAPI) ShareCommunityURLWithChatKey(communityID types.HexBytes) (string, error) {
+	return api.service.messenger.ShareCommunityURLWithChatKey(communityID)
+}
+
+func (api *PublicAPI) ShareCommunityURLWithData(communityID types.HexBytes) (string, error) {
+	return api.service.messenger.ShareCommunityURLWithData(communityID)
+}
+
+func (api *PublicAPI) ShareCommunityChannelURLWithChatKey(request *requests.CommunityChannelShareURL) (string, error) {
+	return api.service.messenger.ShareCommunityChannelURLWithChatKey(request)
+}
+
+func (api *PublicAPI) ShareCommunityChannelURLWithData(request *requests.CommunityChannelShareURL) (string, error) {
+	return api.service.messenger.ShareCommunityChannelURLWithData(request)
+}
+
+func (api *PublicAPI) ShareUserURLWithENS(pubKey string) (string, error) {
+	return api.service.messenger.ShareUserURLWithENS(pubKey)
+}
+
+func (api *PublicAPI) ShareUserURLWithChatKey(pubKey string) (string, error) {
+	return api.service.messenger.ShareUserURLWithChatKey(pubKey)
+}
+
+func (api *PublicAPI) ShareUserURLWithData(pubKey string) (string, error) {
+	return api.service.messenger.ShareUserURLWithData(pubKey)
+}
+
+func (api *PublicAPI) ParseSharedURL(url string) (*protocol.URLDataResponse, error) {
+	return api.service.messenger.ParseSharedURL(url)
+}
+
 func (api *PublicAPI) Messenger() *protocol.Messenger {
 	return api.service.messenger
 }

vendor/github.com/andybalholm/brotli/LICENSE

@@ -0,0 +1,19 @@
+Copyright (c) 2009, 2010, 2013-2016 by the Brotli Authors.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

vendor/github.com/andybalholm/brotli/README.md

@@ -0,0 +1,7 @@
+This package is a brotli compressor and decompressor implemented in Go.
+It was translated from the reference implementation (https://github.com/google/brotli)
+with the `c2go` tool at https://github.com/andybalholm/c2go.
+
+I am using it in production with https://github.com/andybalholm/redwood.
+
+API documentation is found at https://pkg.go.dev/github.com/andybalholm/brotli?tab=doc.

vendor/github.com/andybalholm/brotli/backward_references.go

@@ -0,0 +1,185 @@
+package brotli
+
+import (
+	"sync"
+)
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Function to find backward reference copies. */
+
+func computeDistanceCode(distance uint, max_distance uint, dist_cache []int) uint {
+	if distance <= max_distance {
+		var distance_plus_3 uint = distance + 3
+		var offset0 uint = distance_plus_3 - uint(dist_cache[0])
+		var offset1 uint = distance_plus_3 - uint(dist_cache[1])
+		if distance == uint(dist_cache[0]) {
+			return 0
+		} else if distance == uint(dist_cache[1]) {
+			return 1
+		} else if offset0 < 7 {
+			return (0x9750468 >> (4 * offset0)) & 0xF
+		} else if offset1 < 7 {
+			return (0xFDB1ACE >> (4 * offset1)) & 0xF
+		} else if distance == uint(dist_cache[2]) {
+			return 2
+		} else if distance == uint(dist_cache[3]) {
+			return 3
+		}
+	}
+
+	return distance + numDistanceShortCodes - 1
+}
+
+var hasherSearchResultPool sync.Pool
+
+func createBackwardReferences(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, hasher hasherHandle, dist_cache []int, last_insert_len *uint, commands *[]command, num_literals *uint) {
+	var max_backward_limit uint = maxBackwardLimit(params.lgwin)
+	var insert_length uint = *last_insert_len
+	var pos_end uint = position + num_bytes
+	var store_end uint
+	if num_bytes >= hasher.StoreLookahead() {
+		store_end = position + num_bytes - hasher.StoreLookahead() + 1
+	} else {
+		store_end = position
+	}
+	var random_heuristics_window_size uint = literalSpreeLengthForSparseSearch(params)
+	var apply_random_heuristics uint = position + random_heuristics_window_size
+	var gap uint = 0
+	/* Set maximum distance, see section 9.1. of the spec. */
+
+	const kMinScore uint = scoreBase + 100
+
+	/* For speed up heuristics for random data. */
+
+	/* Minimum score to accept a backward reference. */
+	hasher.PrepareDistanceCache(dist_cache)
+	sr2, _ := hasherSearchResultPool.Get().(*hasherSearchResult)
+	if sr2 == nil {
+		sr2 = &hasherSearchResult{}
+	}
+	sr, _ := hasherSearchResultPool.Get().(*hasherSearchResult)
+	if sr == nil {
+		sr = &hasherSearchResult{}
+	}
+
+	for position+hasher.HashTypeLength() < pos_end {
+		var max_length uint = pos_end - position
+		var max_distance uint = brotli_min_size_t(position, max_backward_limit)
+		sr.len = 0
+		sr.len_code_delta = 0
+		sr.distance = 0
+		sr.score = kMinScore
+		hasher.FindLongestMatch(&params.dictionary, ringbuffer, ringbuffer_mask, dist_cache, position, max_length, max_distance, gap, params.dist.max_distance, sr)
+		if sr.score > kMinScore {
+			/* Found a match. Let's look for something even better ahead. */
+			var delayed_backward_references_in_row int = 0
+			max_length--
+			for ; ; max_length-- {
+				var cost_diff_lazy uint = 175
+				if params.quality < minQualityForExtensiveReferenceSearch {
+					sr2.len = brotli_min_size_t(sr.len-1, max_length)
+				} else {
+					sr2.len = 0
+				}
+				sr2.len_code_delta = 0
+				sr2.distance = 0
+				sr2.score = kMinScore
+				max_distance = brotli_min_size_t(position+1, max_backward_limit)
+				hasher.FindLongestMatch(&params.dictionary, ringbuffer, ringbuffer_mask, dist_cache, position+1, max_length, max_distance, gap, params.dist.max_distance, sr2)
+				if sr2.score >= sr.score+cost_diff_lazy {
+					/* Ok, let's just write one byte for now and start a match from the
+					   next byte. */
+					position++
+
+					insert_length++
+					*sr = *sr2
+					delayed_backward_references_in_row++
+					if delayed_backward_references_in_row < 4 && position+hasher.HashTypeLength() < pos_end {
+						continue
+					}
+				}
+
+				break
+			}
+
+			apply_random_heuristics = position + 2*sr.len + random_heuristics_window_size
+			max_distance = brotli_min_size_t(position, max_backward_limit)
+			{
+				/* The first 16 codes are special short-codes,
+				   and the minimum offset is 1. */
+				var distance_code uint = computeDistanceCode(sr.distance, max_distance+gap, dist_cache)
+				if (sr.distance <= (max_distance + gap)) && distance_code > 0 {
+					dist_cache[3] = dist_cache[2]
+					dist_cache[2] = dist_cache[1]
+					dist_cache[1] = dist_cache[0]
+					dist_cache[0] = int(sr.distance)
+					hasher.PrepareDistanceCache(dist_cache)
+				}
+
+				*commands = append(*commands, makeCommand(&params.dist, insert_length, sr.len, sr.len_code_delta, distance_code))
+			}
+
+			*num_literals += insert_length
+			insert_length = 0
+			/* Put the hash keys into the table, if there are enough bytes left.
+			   Depending on the hasher implementation, it can push all positions
+			   in the given range or only a subset of them.
+			   Avoid hash poisoning with RLE data. */
+			{
+				var range_start uint = position + 2
+				var range_end uint = brotli_min_size_t(position+sr.len, store_end)
+				if sr.distance < sr.len>>2 {
+					range_start = brotli_min_size_t(range_end, brotli_max_size_t(range_start, position+sr.len-(sr.distance<<2)))
+				}
+
+				hasher.StoreRange(ringbuffer, ringbuffer_mask, range_start, range_end)
+			}
+
+			position += sr.len
+		} else {
+			insert_length++
+			position++
+
+			/* If we have not seen matches for a long time, we can skip some
+			   match lookups. Unsuccessful match lookups are very very expensive
+			   and this kind of a heuristic speeds up compression quite
+			   a lot. */
+			if position > apply_random_heuristics {
+				/* Going through uncompressible data, jump. */
+				if position > apply_random_heuristics+4*random_heuristics_window_size {
+					var kMargin uint = brotli_max_size_t(hasher.StoreLookahead()-1, 4)
+					/* It is quite a long time since we saw a copy, so we assume
+					   that this data is not compressible, and store hashes less
+					   often. Hashes of non compressible data are less likely to
+					   turn out to be useful in the future, too, so we store less of
+					   them to not to flood out the hash table of good compressible
+					   data. */
+
+					var pos_jump uint = brotli_min_size_t(position+16, pos_end-kMargin)
+					for ; position < pos_jump; position += 4 {
+						hasher.Store(ringbuffer, ringbuffer_mask, position)
+						insert_length += 4
+					}
+				} else {
+					var kMargin uint = brotli_max_size_t(hasher.StoreLookahead()-1, 2)
+					var pos_jump uint = brotli_min_size_t(position+8, pos_end-kMargin)
+					for ; position < pos_jump; position += 2 {
+						hasher.Store(ringbuffer, ringbuffer_mask, position)
+						insert_length += 2
+					}
+				}
+			}
+		}
+	}
+
+	insert_length += pos_end - position
+	*last_insert_len = insert_length
+
+	hasherSearchResultPool.Put(sr)
+	hasherSearchResultPool.Put(sr2)
+}

vendor/github.com/andybalholm/brotli/backward_references_hq.go

@@ -0,0 +1,796 @@
+package brotli
+
+import "math"
+
+type zopfliNode struct {
+	length              uint32
+	distance            uint32
+	dcode_insert_length uint32
+	u                   struct {
+		cost     float32
+		next     uint32
+		shortcut uint32
+	}
+}
+
+const maxEffectiveDistanceAlphabetSize = 544
+
+const kInfinity float32 = 1.7e38 /* ~= 2 ^ 127 */
+
+var kDistanceCacheIndex = []uint32{0, 1, 2, 3, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1}
+
+var kDistanceCacheOffset = []int{0, 0, 0, 0, -1, 1, -2, 2, -3, 3, -1, 1, -2, 2, -3, 3}
+
+func initZopfliNodes(array []zopfliNode, length uint) {
+	var stub zopfliNode
+	var i uint
+	stub.length = 1
+	stub.distance = 0
+	stub.dcode_insert_length = 0
+	stub.u.cost = kInfinity
+	for i = 0; i < length; i++ {
+		array[i] = stub
+	}
+}
+
+func zopfliNodeCopyLength(self *zopfliNode) uint32 {
+	return self.length & 0x1FFFFFF
+}
+
+func zopfliNodeLengthCode(self *zopfliNode) uint32 {
+	var modifier uint32 = self.length >> 25
+	return zopfliNodeCopyLength(self) + 9 - modifier
+}
+
+func zopfliNodeCopyDistance(self *zopfliNode) uint32 {
+	return self.distance
+}
+
+func zopfliNodeDistanceCode(self *zopfliNode) uint32 {
+	var short_code uint32 = self.dcode_insert_length >> 27
+	if short_code == 0 {
+		return zopfliNodeCopyDistance(self) + numDistanceShortCodes - 1
+	} else {
+		return short_code - 1
+	}
+}
+
+func zopfliNodeCommandLength(self *zopfliNode) uint32 {
+	return zopfliNodeCopyLength(self) + (self.dcode_insert_length & 0x7FFFFFF)
+}
+
+/* Histogram based cost model for zopflification. */
+type zopfliCostModel struct {
+	cost_cmd_               [numCommandSymbols]float32
+	cost_dist_              []float32
+	distance_histogram_size uint32
+	literal_costs_          []float32
+	min_cost_cmd_           float32
+	num_bytes_              uint
+}
+
+func initZopfliCostModel(self *zopfliCostModel, dist *distanceParams, num_bytes uint) {
+	var distance_histogram_size uint32 = dist.alphabet_size
+	if distance_histogram_size > maxEffectiveDistanceAlphabetSize {
+		distance_histogram_size = maxEffectiveDistanceAlphabetSize
+	}
+
+	self.num_bytes_ = num_bytes
+	self.literal_costs_ = make([]float32, (num_bytes + 2))
+	self.cost_dist_ = make([]float32, (dist.alphabet_size))
+	self.distance_histogram_size = distance_histogram_size
+}
+
+func cleanupZopfliCostModel(self *zopfliCostModel) {
+	self.literal_costs_ = nil
+	self.cost_dist_ = nil
+}
+
+func setCost(histogram []uint32, histogram_size uint, literal_histogram bool, cost []float32) {
+	var sum uint = 0
+	var missing_symbol_sum uint
+	var log2sum float32
+	var missing_symbol_cost float32
+	var i uint
+	for i = 0; i < histogram_size; i++ {
+		sum += uint(histogram[i])
+	}
+
+	log2sum = float32(fastLog2(sum))
+	missing_symbol_sum = sum
+	if !literal_histogram {
+		for i = 0; i < histogram_size; i++ {
+			if histogram[i] == 0 {
+				missing_symbol_sum++
+			}
+		}
+	}
+
+	missing_symbol_cost = float32(fastLog2(missing_symbol_sum)) + 2
+	for i = 0; i < histogram_size; i++ {
+		if histogram[i] == 0 {
+			cost[i] = missing_symbol_cost
+			continue
+		}
+
+		/* Shannon bits for this symbol. */
+		cost[i] = log2sum - float32(fastLog2(uint(histogram[i])))
+
+		/* Cannot be coded with less than 1 bit */
+		if cost[i] < 1 {
+			cost[i] = 1
+		}
+	}
+}
+
+func zopfliCostModelSetFromCommands(self *zopfliCostModel, position uint, ringbuffer []byte, ringbuffer_mask uint, commands []command, last_insert_len uint) {
+	var histogram_literal [numLiteralSymbols]uint32
+	var histogram_cmd [numCommandSymbols]uint32
+	var histogram_dist [maxEffectiveDistanceAlphabetSize]uint32
+	var cost_literal [numLiteralSymbols]float32
+	var pos uint = position - last_insert_len
+	var min_cost_cmd float32 = kInfinity
+	var cost_cmd []float32 = self.cost_cmd_[:]
+	var literal_costs []float32
+
+	histogram_literal = [numLiteralSymbols]uint32{}
+	histogram_cmd = [numCommandSymbols]uint32{}
+	histogram_dist = [maxEffectiveDistanceAlphabetSize]uint32{}
+
+	for i := range commands {
+		var inslength uint = uint(commands[i].insert_len_)
+		var copylength uint = uint(commandCopyLen(&commands[i]))
+		var distcode uint = uint(commands[i].dist_prefix_) & 0x3FF
+		var cmdcode uint = uint(commands[i].cmd_prefix_)
+		var j uint
+
+		histogram_cmd[cmdcode]++
+		if cmdcode >= 128 {
+			histogram_dist[distcode]++
+		}
+
+		for j = 0; j < inslength; j++ {
+			histogram_literal[ringbuffer[(pos+j)&ringbuffer_mask]]++
+		}
+
+		pos += inslength + copylength
+	}
+
+	setCost(histogram_literal[:], numLiteralSymbols, true, cost_literal[:])
+	setCost(histogram_cmd[:], numCommandSymbols, false, cost_cmd)
+	setCost(histogram_dist[:], uint(self.distance_histogram_size), false, self.cost_dist_)
+
+	for i := 0; i < numCommandSymbols; i++ {
+		min_cost_cmd = brotli_min_float(min_cost_cmd, cost_cmd[i])
+	}
+
+	self.min_cost_cmd_ = min_cost_cmd
+	{
+		literal_costs = self.literal_costs_
+		var literal_carry float32 = 0.0
+		num_bytes := int(self.num_bytes_)
+		literal_costs[0] = 0.0
+		for i := 0; i < num_bytes; i++ {
+			literal_carry += cost_literal[ringbuffer[(position+uint(i))&ringbuffer_mask]]
+			literal_costs[i+1] = literal_costs[i] + literal_carry
+			literal_carry -= literal_costs[i+1] - literal_costs[i]
+		}
+	}
+}
+
+func zopfliCostModelSetFromLiteralCosts(self *zopfliCostModel, position uint, ringbuffer []byte, ringbuffer_mask uint) {
+	var literal_costs []float32 = self.literal_costs_
+	var literal_carry float32 = 0.0
+	var cost_dist []float32 = self.cost_dist_
+	var cost_cmd []float32 = self.cost_cmd_[:]
+	var num_bytes uint = self.num_bytes_
+	var i uint
+	estimateBitCostsForLiterals(position, num_bytes, ringbuffer_mask, ringbuffer, literal_costs[1:])
+	literal_costs[0] = 0.0
+	for i = 0; i < num_bytes; i++ {
+		literal_carry += literal_costs[i+1]
+		literal_costs[i+1] = literal_costs[i] + literal_carry
+		literal_carry -= literal_costs[i+1] - literal_costs[i]
+	}
+
+	for i = 0; i < numCommandSymbols; i++ {
+		cost_cmd[i] = float32(fastLog2(uint(11 + uint32(i))))
+	}
+
+	for i = 0; uint32(i) < self.distance_histogram_size; i++ {
+		cost_dist[i] = float32(fastLog2(uint(20 + uint32(i))))
+	}
+
+	self.min_cost_cmd_ = float32(fastLog2(11))
+}
+
+func zopfliCostModelGetCommandCost(self *zopfliCostModel, cmdcode uint16) float32 {
+	return self.cost_cmd_[cmdcode]
+}
+
+func zopfliCostModelGetDistanceCost(self *zopfliCostModel, distcode uint) float32 {
+	return self.cost_dist_[distcode]
+}
+
+func zopfliCostModelGetLiteralCosts(self *zopfliCostModel, from uint, to uint) float32 {
+	return self.literal_costs_[to] - self.literal_costs_[from]
+}
+
+func zopfliCostModelGetMinCostCmd(self *zopfliCostModel) float32 {
+	return self.min_cost_cmd_
+}
+
+/* REQUIRES: len >= 2, start_pos <= pos */
+/* REQUIRES: cost < kInfinity, nodes[start_pos].cost < kInfinity */
+/* Maintains the "ZopfliNode array invariant". */
+func updateZopfliNode(nodes []zopfliNode, pos uint, start_pos uint, len uint, len_code uint, dist uint, short_code uint, cost float32) {
+	var next *zopfliNode = &nodes[pos+len]
+	next.length = uint32(len | (len+9-len_code)<<25)
+	next.distance = uint32(dist)
+	next.dcode_insert_length = uint32(short_code<<27 | (pos - start_pos))
+	next.u.cost = cost
+}
+
+type posData struct {
+	pos            uint
+	distance_cache [4]int
+	costdiff       float32
+	cost           float32
+}
+
+/* Maintains the smallest 8 cost difference together with their positions */
+type startPosQueue struct {
+	q_   [8]posData
+	idx_ uint
+}
+
+func initStartPosQueue(self *startPosQueue) {
+	self.idx_ = 0
+}
+
+func startPosQueueSize(self *startPosQueue) uint {
+	return brotli_min_size_t(self.idx_, 8)
+}
+
+func startPosQueuePush(self *startPosQueue, posdata *posData) {
+	var offset uint = ^(self.idx_) & 7
+	self.idx_++
+	var len uint = startPosQueueSize(self)
+	var i uint
+	var q []posData = self.q_[:]
+	q[offset] = *posdata
+
+	/* Restore the sorted order. In the list of |len| items at most |len - 1|
+	   adjacent element comparisons / swaps are required. */
+	for i = 1; i < len; i++ {
+		if q[offset&7].costdiff > q[(offset+1)&7].costdiff {
+			var tmp posData = q[offset&7]
+			q[offset&7] = q[(offset+1)&7]
+			q[(offset+1)&7] = tmp
+		}
+
+		offset++
+	}
+}
+
+func startPosQueueAt(self *startPosQueue, k uint) *posData {
+	return &self.q_[(k-self.idx_)&7]
+}
+
+/* Returns the minimum possible copy length that can improve the cost of any */
+/* future position. */
+func computeMinimumCopyLength(start_cost float32, nodes []zopfliNode, num_bytes uint, pos uint) uint {
+	var min_cost float32 = start_cost
+	var len uint = 2
+	var next_len_bucket uint = 4
+	/* Compute the minimum possible cost of reaching any future position. */
+
+	var next_len_offset uint = 10
+	for pos+len <= num_bytes && nodes[pos+len].u.cost <= min_cost {
+		/* We already reached (pos + len) with no more cost than the minimum
+		   possible cost of reaching anything from this pos, so there is no point in
+		   looking for lengths <= len. */
+		len++
+
+		if len == next_len_offset {
+			/* We reached the next copy length code bucket, so we add one more
+			   extra bit to the minimum cost. */
+			min_cost += 1.0
+
+			next_len_offset += next_len_bucket
+			next_len_bucket *= 2
+		}
+	}
+
+	return uint(len)
+}
+
+/* REQUIRES: nodes[pos].cost < kInfinity
+   REQUIRES: nodes[0..pos] satisfies that "ZopfliNode array invariant". */
+func computeDistanceShortcut(block_start uint, pos uint, max_backward_limit uint, gap uint, nodes []zopfliNode) uint32 {
+	var clen uint = uint(zopfliNodeCopyLength(&nodes[pos]))
+	var ilen uint = uint(nodes[pos].dcode_insert_length & 0x7FFFFFF)
+	var dist uint = uint(zopfliNodeCopyDistance(&nodes[pos]))
+
+	/* Since |block_start + pos| is the end position of the command, the copy part
+	   starts from |block_start + pos - clen|. Distances that are greater than
+	   this or greater than |max_backward_limit| + |gap| are static dictionary
+	   references, and do not update the last distances.
+	   Also distance code 0 (last distance) does not update the last distances. */
+	if pos == 0 {
+		return 0
+	} else if dist+clen <= block_start+pos+gap && dist <= max_backward_limit+gap && zopfliNodeDistanceCode(&nodes[pos]) > 0 {
+		return uint32(pos)
+	} else {
+		return nodes[pos-clen-ilen].u.shortcut
+	}
+}
+
+/* Fills in dist_cache[0..3] with the last four distances (as defined by
+   Section 4. of the Spec) that would be used at (block_start + pos) if we
+   used the shortest path of commands from block_start, computed from
+   nodes[0..pos]. The last four distances at block_start are in
+   starting_dist_cache[0..3].
+   REQUIRES: nodes[pos].cost < kInfinity
+   REQUIRES: nodes[0..pos] satisfies that "ZopfliNode array invariant". */
+func computeDistanceCache(pos uint, starting_dist_cache []int, nodes []zopfliNode, dist_cache []int) {
+	var idx int = 0
+	var p uint = uint(nodes[pos].u.shortcut)
+	for idx < 4 && p > 0 {
+		var ilen uint = uint(nodes[p].dcode_insert_length & 0x7FFFFFF)
+		var clen uint = uint(zopfliNodeCopyLength(&nodes[p]))
+		var dist uint = uint(zopfliNodeCopyDistance(&nodes[p]))
+		dist_cache[idx] = int(dist)
+		idx++
+
+		/* Because of prerequisite, p >= clen + ilen >= 2. */
+		p = uint(nodes[p-clen-ilen].u.shortcut)
+	}
+
+	for ; idx < 4; idx++ {
+		dist_cache[idx] = starting_dist_cache[0]
+		starting_dist_cache = starting_dist_cache[1:]
+	}
+}
+
+/* Maintains "ZopfliNode array invariant" and pushes node to the queue, if it
+   is eligible. */
+func evaluateNode(block_start uint, pos uint, max_backward_limit uint, gap uint, starting_dist_cache []int, model *zopfliCostModel, queue *startPosQueue, nodes []zopfliNode) {
+	/* Save cost, because ComputeDistanceCache invalidates it. */
+	var node_cost float32 = nodes[pos].u.cost
+	nodes[pos].u.shortcut = computeDistanceShortcut(block_start, pos, max_backward_limit, gap, nodes)
+	if node_cost <= zopfliCostModelGetLiteralCosts(model, 0, pos) {
+		var posdata posData
+		posdata.pos = pos
+		posdata.cost = node_cost
+		posdata.costdiff = node_cost - zopfliCostModelGetLiteralCosts(model, 0, pos)
+		computeDistanceCache(pos, starting_dist_cache, nodes, posdata.distance_cache[:])
+		startPosQueuePush(queue, &posdata)
+	}
+}
+
+/* Returns longest copy length. */
+func updateNodes(num_bytes uint, block_start uint, pos uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, max_backward_limit uint, starting_dist_cache []int, num_matches uint, matches []backwardMatch, model *zopfliCostModel, queue *startPosQueue, nodes []zopfliNode) uint {
+	var cur_ix uint = block_start + pos
+	var cur_ix_masked uint = cur_ix & ringbuffer_mask
+	var max_distance uint = brotli_min_size_t(cur_ix, max_backward_limit)
+	var max_len uint = num_bytes - pos
+	var max_zopfli_len uint = maxZopfliLen(params)
+	var max_iters uint = maxZopfliCandidates(params)
+	var min_len uint
+	var result uint = 0
+	var k uint
+	var gap uint = 0
+
+	evaluateNode(block_start, pos, max_backward_limit, gap, starting_dist_cache, model, queue, nodes)
+	{
+		var posdata *posData = startPosQueueAt(queue, 0)
+		var min_cost float32 = (posdata.cost + zopfliCostModelGetMinCostCmd(model) + zopfliCostModelGetLiteralCosts(model, posdata.pos, pos))
+		min_len = computeMinimumCopyLength(min_cost, nodes, num_bytes, pos)
+	}
+
+	/* Go over the command starting positions in order of increasing cost
+	   difference. */
+	for k = 0; k < max_iters && k < startPosQueueSize(queue); k++ {
+		var posdata *posData = startPosQueueAt(queue, k)
+		var start uint = posdata.pos
+		var inscode uint16 = getInsertLengthCode(pos - start)
+		var start_costdiff float32 = posdata.costdiff
+		var base_cost float32 = start_costdiff + float32(getInsertExtra(inscode)) + zopfliCostModelGetLiteralCosts(model, 0, pos)
+		var best_len uint = min_len - 1
+		var j uint = 0
+		/* Look for last distance matches using the distance cache from this
+		   starting position. */
+		for ; j < numDistanceShortCodes && best_len < max_len; j++ {
+			var idx uint = uint(kDistanceCacheIndex[j])
+			var backward uint = uint(posdata.distance_cache[idx] + kDistanceCacheOffset[j])
+			var prev_ix uint = cur_ix - backward
+			var len uint = 0
+			var continuation byte = ringbuffer[cur_ix_masked+best_len]
+			if cur_ix_masked+best_len > ringbuffer_mask {
+				break
+			}
+
+			if backward > max_distance+gap {
+				/* Word dictionary -> ignore. */
+				continue
+			}
+
+			if backward <= max_distance {
+				/* Regular backward reference. */
+				if prev_ix >= cur_ix {
+					continue
+				}
+
+				prev_ix &= ringbuffer_mask
+				if prev_ix+best_len > ringbuffer_mask || continuation != ringbuffer[prev_ix+best_len] {
+					continue
+				}
+
+				len = findMatchLengthWithLimit(ringbuffer[prev_ix:], ringbuffer[cur_ix_masked:], max_len)
+			} else {
+				continue
+			}
+			{
+				var dist_cost float32 = base_cost + zopfliCostModelGetDistanceCost(model, j)
+				var l uint
+				for l = best_len + 1; l <= len; l++ {
+					var copycode uint16 = getCopyLengthCode(l)
+					var cmdcode uint16 = combineLengthCodes(inscode, copycode, j == 0)
+					var tmp float32
+					if cmdcode < 128 {
+						tmp = base_cost
+					} else {
+						tmp = dist_cost
+					}
+					var cost float32 = tmp + float32(getCopyExtra(copycode)) + zopfliCostModelGetCommandCost(model, cmdcode)
+					if cost < nodes[pos+l].u.cost {
+						updateZopfliNode(nodes, pos, start, l, l, backward, j+1, cost)
+						result = brotli_max_size_t(result, l)
+					}
+
+					best_len = l
+				}
+			}
+		}
+
+		/* At higher iterations look only for new last distance matches, since
+		   looking only for new command start positions with the same distances
+		   does not help much. */
+		if k >= 2 {
+			continue
+		}
+		{
+			/* Loop through all possible copy lengths at this position. */
+			var len uint = min_len
+			for j = 0; j < num_matches; j++ {
+				var match backwardMatch = matches[j]
+				var dist uint = uint(match.distance)
+				var is_dictionary_match bool = (dist > max_distance+gap)
+				var dist_code uint = dist + numDistanceShortCodes - 1
+				var dist_symbol uint16
+				var distextra uint32
+				var distnumextra uint32
+				var dist_cost float32
+				var max_match_len uint
+				/* We already tried all possible last distance matches, so we can use
+				   normal distance code here. */
+				prefixEncodeCopyDistance(dist_code, uint(params.dist.num_direct_distance_codes), uint(params.dist.distance_postfix_bits), &dist_symbol, &distextra)
+
+				distnumextra = uint32(dist_symbol) >> 10
+				dist_cost = base_cost + float32(distnumextra) + zopfliCostModelGetDistanceCost(model, uint(dist_symbol)&0x3FF)
+
+				/* Try all copy lengths up until the maximum copy length corresponding
+				   to this distance. If the distance refers to the static dictionary, or
+				   the maximum length is long enough, try only one maximum length. */
+				max_match_len = backwardMatchLength(&match)
+
+				if len < max_match_len && (is_dictionary_match || max_match_len > max_zopfli_len) {
+					len = max_match_len
+				}
+
+				for ; len <= max_match_len; len++ {
+					var len_code uint
+					if is_dictionary_match {
+						len_code = backwardMatchLengthCode(&match)
+					} else {
+						len_code = len
+					}
+					var copycode uint16 = getCopyLengthCode(len_code)
+					var cmdcode uint16 = combineLengthCodes(inscode, copycode, false)
+					var cost float32 = dist_cost + float32(getCopyExtra(copycode)) + zopfliCostModelGetCommandCost(model, cmdcode)
+					if cost < nodes[pos+len].u.cost {
+						updateZopfliNode(nodes, pos, start, uint(len), len_code, dist, 0, cost)
+						if len > result {
+							result = len
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return result
+}
+
+func computeShortestPathFromNodes(num_bytes uint, nodes []zopfliNode) uint {
+	var index uint = num_bytes
+	var num_commands uint = 0
+	for nodes[index].dcode_insert_length&0x7FFFFFF == 0 && nodes[index].length == 1 {
+		index--
+	}
+	nodes[index].u.next = math.MaxUint32
+	for index != 0 {
+		var len uint = uint(zopfliNodeCommandLength(&nodes[index]))
+		index -= uint(len)
+		nodes[index].u.next = uint32(len)
+		num_commands++
+	}
+
+	return num_commands
+}
+
+/* REQUIRES: nodes != NULL and len(nodes) >= num_bytes + 1 */
+func zopfliCreateCommands(num_bytes uint, block_start uint, nodes []zopfliNode, dist_cache []int, last_insert_len *uint, params *encoderParams, commands *[]command, num_literals *uint) {
+	var max_backward_limit uint = maxBackwardLimit(params.lgwin)
+	var pos uint = 0
+	var offset uint32 = nodes[0].u.next
+	var i uint
+	var gap uint = 0
+	for i = 0; offset != math.MaxUint32; i++ {
+		var next *zopfliNode = &nodes[uint32(pos)+offset]
+		var copy_length uint = uint(zopfliNodeCopyLength(next))
+		var insert_length uint = uint(next.dcode_insert_length & 0x7FFFFFF)
+		pos += insert_length
+		offset = next.u.next
+		if i == 0 {
+			insert_length += *last_insert_len
+			*last_insert_len = 0
+		}
+		{
+			var distance uint = uint(zopfliNodeCopyDistance(next))
+			var len_code uint = uint(zopfliNodeLengthCode(next))
+			var max_distance uint = brotli_min_size_t(block_start+pos, max_backward_limit)
+			var is_dictionary bool = (distance > max_distance+gap)
+			var dist_code uint = uint(zopfliNodeDistanceCode(next))
+			*commands = append(*commands, makeCommand(&params.dist, insert_length, copy_length, int(len_code)-int(copy_length), dist_code))
+
+			if !is_dictionary && dist_code > 0 {
+				dist_cache[3] = dist_cache[2]
+				dist_cache[2] = dist_cache[1]
+				dist_cache[1] = dist_cache[0]
+				dist_cache[0] = int(distance)
+			}
+		}
+
+		*num_literals += insert_length
+		pos += copy_length
+	}
+
+	*last_insert_len += num_bytes - pos
+}
+
+func zopfliIterate(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, gap uint, dist_cache []int, model *zopfliCostModel, num_matches []uint32, matches []backwardMatch, nodes []zopfliNode) uint {
+	var max_backward_limit uint = maxBackwardLimit(params.lgwin)
+	var max_zopfli_len uint = maxZopfliLen(params)
+	var queue startPosQueue
+	var cur_match_pos uint = 0
+	var i uint
+	nodes[0].length = 0
+	nodes[0].u.cost = 0
+	initStartPosQueue(&queue)
+	for i = 0; i+3 < num_bytes; i++ {
+		var skip uint = updateNodes(num_bytes, position, i, ringbuffer, ringbuffer_mask, params, max_backward_limit, dist_cache, uint(num_matches[i]), matches[cur_match_pos:], model, &queue, nodes)
+		if skip < longCopyQuickStep {
+			skip = 0
+		}
+		cur_match_pos += uint(num_matches[i])
+		if num_matches[i] == 1 && backwardMatchLength(&matches[cur_match_pos-1]) > max_zopfli_len {
+			skip = brotli_max_size_t(backwardMatchLength(&matches[cur_match_pos-1]), skip)
+		}
+
+		if skip > 1 {
+			skip--
+			for skip != 0 {
+				i++
+				if i+3 >= num_bytes {
+					break
+				}
+				evaluateNode(position, i, max_backward_limit, gap, dist_cache, model, &queue, nodes)
+				cur_match_pos += uint(num_matches[i])
+				skip--
+			}
+		}
+	}
+
+	return computeShortestPathFromNodes(num_bytes, nodes)
+}
+
+/* Computes the shortest path of commands from position to at most
+   position + num_bytes.
+
+   On return, path->size() is the number of commands found and path[i] is the
+   length of the i-th command (copy length plus insert length).
+   Note that the sum of the lengths of all commands can be less than num_bytes.
+
+   On return, the nodes[0..num_bytes] array will have the following
+   "ZopfliNode array invariant":
+   For each i in [1..num_bytes], if nodes[i].cost < kInfinity, then
+     (1) nodes[i].copy_length() >= 2
+     (2) nodes[i].command_length() <= i and
+     (3) nodes[i - nodes[i].command_length()].cost < kInfinity
+
+ REQUIRES: nodes != nil and len(nodes) >= num_bytes + 1 */
+func zopfliComputeShortestPath(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, dist_cache []int, hasher *h10, nodes []zopfliNode) uint {
+	var max_backward_limit uint = maxBackwardLimit(params.lgwin)
+	var max_zopfli_len uint = maxZopfliLen(params)
+	var model zopfliCostModel
+	var queue startPosQueue
+	var matches [2 * (maxNumMatchesH10 + 64)]backwardMatch
+	var store_end uint
+	if num_bytes >= hasher.StoreLookahead() {
+		store_end = position + num_bytes - hasher.StoreLookahead() + 1
+	} else {
+		store_end = position
+	}
+	var i uint
+	var gap uint = 0
+	var lz_matches_offset uint = 0
+	nodes[0].length = 0
+	nodes[0].u.cost = 0
+	initZopfliCostModel(&model, &params.dist, num_bytes)
+	zopfliCostModelSetFromLiteralCosts(&model, position, ringbuffer, ringbuffer_mask)
+	initStartPosQueue(&queue)
+	for i = 0; i+hasher.HashTypeLength()-1 < num_bytes; i++ {
+		var pos uint = position + i
+		var max_distance uint = brotli_min_size_t(pos, max_backward_limit)
+		var skip uint
+		var num_matches uint
+		num_matches = findAllMatchesH10(hasher, &params.dictionary, ringbuffer, ringbuffer_mask, pos, num_bytes-i, max_distance, gap, params, matches[lz_matches_offset:])
+		if num_matches > 0 && backwardMatchLength(&matches[num_matches-1]) > max_zopfli_len {
+			matches[0] = matches[num_matches-1]
+			num_matches = 1
+		}
+
+		skip = updateNodes(num_bytes, position, i, ringbuffer, ringbuffer_mask, params, max_backward_limit, dist_cache, num_matches, matches[:], &model, &queue, nodes)
+		if skip < longCopyQuickStep {
+			skip = 0
+		}
+		if num_matches == 1 && backwardMatchLength(&matches[0]) > max_zopfli_len {
+			skip = brotli_max_size_t(backwardMatchLength(&matches[0]), skip)
+		}
+
+		if skip > 1 {
+			/* Add the tail of the copy to the hasher. */
+			hasher.StoreRange(ringbuffer, ringbuffer_mask, pos+1, brotli_min_size_t(pos+skip, store_end))
+
+			skip--
+			for skip != 0 {
+				i++
+				if i+hasher.HashTypeLength()-1 >= num_bytes {
+					break
+				}
+				evaluateNode(position, i, max_backward_limit, gap, dist_cache, &model, &queue, nodes)
+				skip--
+			}
+		}
+	}
+
+	cleanupZopfliCostModel(&model)
+	return computeShortestPathFromNodes(num_bytes, nodes)
+}
+
+func createZopfliBackwardReferences(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, hasher *h10, dist_cache []int, last_insert_len *uint, commands *[]command, num_literals *uint) {
+	var nodes []zopfliNode
+	nodes = make([]zopfliNode, (num_bytes + 1))
+	initZopfliNodes(nodes, num_bytes+1)
+	zopfliComputeShortestPath(num_bytes, position, ringbuffer, ringbuffer_mask, params, dist_cache, hasher, nodes)
+	zopfliCreateCommands(num_bytes, position, nodes, dist_cache, last_insert_len, params, commands, num_literals)
+	nodes = nil
+}
+
+func createHqZopfliBackwardReferences(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint, params *encoderParams, hasher hasherHandle, dist_cache []int, last_insert_len *uint, commands *[]command, num_literals *uint) {
+	var max_backward_limit uint = maxBackwardLimit(params.lgwin)
+	var num_matches []uint32 = make([]uint32, num_bytes)
+	var matches_size uint = 4 * num_bytes
+	var store_end uint
+	if num_bytes >= hasher.StoreLookahead() {
+		store_end = position + num_bytes - hasher.StoreLookahead() + 1
+	} else {
+		store_end = position
+	}
+	var cur_match_pos uint = 0
+	var i uint
+	var orig_num_literals uint
+	var orig_last_insert_len uint
+	var orig_dist_cache [4]int
+	var orig_num_commands int
+	var model zopfliCostModel
+	var nodes []zopfliNode
+	var matches []backwardMatch = make([]backwardMatch, matches_size)
+	var gap uint = 0
+	var shadow_matches uint = 0
+	var new_array []backwardMatch
+	for i = 0; i+hasher.HashTypeLength()-1 < num_bytes; i++ {
+		var pos uint = position + i
+		var max_distance uint = brotli_min_size_t(pos, max_backward_limit)
+		var max_length uint = num_bytes - i
+		var num_found_matches uint
+		var cur_match_end uint
+		var j uint
+
+		/* Ensure that we have enough free slots. */
+		if matches_size < cur_match_pos+maxNumMatchesH10+shadow_matches {
+			var new_size uint = matches_size
+			if new_size == 0 {
+				new_size = cur_match_pos + maxNumMatchesH10 + shadow_matches
+			}
+
+			for new_size < cur_match_pos+maxNumMatchesH10+shadow_matches {
+				new_size *= 2
+			}
+
+			new_array = make([]backwardMatch, new_size)
+			if matches_size != 0 {
+				copy(new_array, matches[:matches_size])
+			}
+
+			matches = new_array
+			matches_size = new_size
+		}
+
+		num_found_matches = findAllMatchesH10(hasher.(*h10), &params.dictionary, ringbuffer, ringbuffer_mask, pos, max_length, max_distance, gap, params, matches[cur_match_pos+shadow_matches:])
+		cur_match_end = cur_match_pos + num_found_matches
+		for j = cur_match_pos; j+1 < cur_match_end; j++ {
+			assert(backwardMatchLength(&matches[j]) <= backwardMatchLength(&matches[j+1]))
+		}
+
+		num_matches[i] = uint32(num_found_matches)
+		if num_found_matches > 0 {
+			var match_len uint = backwardMatchLength(&matches[cur_match_end-1])
+			if match_len > maxZopfliLenQuality11 {
+				var skip uint = match_len - 1
+				matches[cur_match_pos] = matches[cur_match_end-1]
+				cur_match_pos++
+				num_matches[i] = 1
+
+				/* Add the tail of the copy to the hasher. */
+				hasher.StoreRange(ringbuffer, ringbuffer_mask, pos+1, brotli_min_size_t(pos+match_len, store_end))
+				var pos uint = i
+				for i := 0; i < int(skip); i++ {
+					num_matches[pos+1:][i] = 0
+				}
+				i += skip
+			} else {
+				cur_match_pos = cur_match_end
+			}
+		}
+	}
+
+	orig_num_literals = *num_literals
+	orig_last_insert_len = *last_insert_len
+	copy(orig_dist_cache[:], dist_cache[:4])
+	orig_num_commands = len(*commands)
+	nodes = make([]zopfliNode, (num_bytes + 1))
+	initZopfliCostModel(&model, &params.dist, num_bytes)
+	for i = 0; i < 2; i++ {
+		initZopfliNodes(nodes, num_bytes+1)
+		if i == 0 {
+			zopfliCostModelSetFromLiteralCosts(&model, position, ringbuffer, ringbuffer_mask)
+		} else {
+			zopfliCostModelSetFromCommands(&model, position, ringbuffer, ringbuffer_mask, (*commands)[orig_num_commands:], orig_last_insert_len)
+		}
+
+		*commands = (*commands)[:orig_num_commands]
+		*num_literals = orig_num_literals
+		*last_insert_len = orig_last_insert_len
+		copy(dist_cache, orig_dist_cache[:4])
+		zopfliIterate(num_bytes, position, ringbuffer, ringbuffer_mask, params, gap, dist_cache, &model, num_matches, matches, nodes)
+		zopfliCreateCommands(num_bytes, position, nodes, dist_cache, last_insert_len, params, commands, num_literals)
+	}
+
+	cleanupZopfliCostModel(&model)
+	nodes = nil
+	matches = nil
+	num_matches = nil
+}

vendor/github.com/andybalholm/brotli/bit_cost.go

@@ -0,0 +1,436 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Functions to estimate the bit cost of Huffman trees. */
+func shannonEntropy(population []uint32, size uint, total *uint) float64 {
+	var sum uint = 0
+	var retval float64 = 0
+	var population_end []uint32 = population[size:]
+	var p uint
+	for -cap(population) < -cap(population_end) {
+		p = uint(population[0])
+		population = population[1:]
+		sum += p
+		retval -= float64(p) * fastLog2(p)
+	}
+
+	if sum != 0 {
+		retval += float64(sum) * fastLog2(sum)
+	}
+	*total = sum
+	return retval
+}
+
+func bitsEntropy(population []uint32, size uint) float64 {
+	var sum uint
+	var retval float64 = shannonEntropy(population, size, &sum)
+	if retval < float64(sum) {
+		/* At least one bit per literal is needed. */
+		retval = float64(sum)
+	}
+
+	return retval
+}
+
+const kOneSymbolHistogramCost float64 = 12
+const kTwoSymbolHistogramCost float64 = 20
+const kThreeSymbolHistogramCost float64 = 28
+const kFourSymbolHistogramCost float64 = 37
+
+func populationCostLiteral(histogram *histogramLiteral) float64 {
+	var data_size uint = histogramDataSizeLiteral()
+	var count int = 0
+	var s [5]uint
+	var bits float64 = 0.0
+	var i uint
+	if histogram.total_count_ == 0 {
+		return kOneSymbolHistogramCost
+	}
+
+	for i = 0; i < data_size; i++ {
+		if histogram.data_[i] > 0 {
+			s[count] = i
+			count++
+			if count > 4 {
+				break
+			}
+		}
+	}
+
+	if count == 1 {
+		return kOneSymbolHistogramCost
+	}
+
+	if count == 2 {
+		return kTwoSymbolHistogramCost + float64(histogram.total_count_)
+	}
+
+	if count == 3 {
+		var histo0 uint32 = histogram.data_[s[0]]
+		var histo1 uint32 = histogram.data_[s[1]]
+		var histo2 uint32 = histogram.data_[s[2]]
+		var histomax uint32 = brotli_max_uint32_t(histo0, brotli_max_uint32_t(histo1, histo2))
+		return kThreeSymbolHistogramCost + 2*(float64(histo0)+float64(histo1)+float64(histo2)) - float64(histomax)
+	}
+
+	if count == 4 {
+		var histo [4]uint32
+		var h23 uint32
+		var histomax uint32
+		for i = 0; i < 4; i++ {
+			histo[i] = histogram.data_[s[i]]
+		}
+
+		/* Sort */
+		for i = 0; i < 4; i++ {
+			var j uint
+			for j = i + 1; j < 4; j++ {
+				if histo[j] > histo[i] {
+					var tmp uint32 = histo[j]
+					histo[j] = histo[i]
+					histo[i] = tmp
+				}
+			}
+		}
+
+		h23 = histo[2] + histo[3]
+		histomax = brotli_max_uint32_t(h23, histo[0])
+		return kFourSymbolHistogramCost + 3*float64(h23) + 2*(float64(histo[0])+float64(histo[1])) - float64(histomax)
+	}
+	{
+		var max_depth uint = 1
+		var depth_histo = [codeLengthCodes]uint32{0}
+		/* In this loop we compute the entropy of the histogram and simultaneously
+		   build a simplified histogram of the code length codes where we use the
+		   zero repeat code 17, but we don't use the non-zero repeat code 16. */
+
+		var log2total float64 = fastLog2(histogram.total_count_)
+		for i = 0; i < data_size; {
+			if histogram.data_[i] > 0 {
+				var log2p float64 = log2total - fastLog2(uint(histogram.data_[i]))
+				/* Compute -log2(P(symbol)) = -log2(count(symbol)/total_count) =
+				   = log2(total_count) - log2(count(symbol)) */
+
+				var depth uint = uint(log2p + 0.5)
+				/* Approximate the bit depth by round(-log2(P(symbol))) */
+				bits += float64(histogram.data_[i]) * log2p
+
+				if depth > 15 {
+					depth = 15
+				}
+
+				if depth > max_depth {
+					max_depth = depth
+				}
+
+				depth_histo[depth]++
+				i++
+			} else {
+				var reps uint32 = 1
+				/* Compute the run length of zeros and add the appropriate number of 0
+				   and 17 code length codes to the code length code histogram. */
+
+				var k uint
+				for k = i + 1; k < data_size && histogram.data_[k] == 0; k++ {
+					reps++
+				}
+
+				i += uint(reps)
+				if i == data_size {
+					/* Don't add any cost for the last zero run, since these are encoded
+					   only implicitly. */
+					break
+				}
+
+				if reps < 3 {
+					depth_histo[0] += reps
+				} else {
+					reps -= 2
+					for reps > 0 {
+						depth_histo[repeatZeroCodeLength]++
+
+						/* Add the 3 extra bits for the 17 code length code. */
+						bits += 3
+
+						reps >>= 3
+					}
+				}
+			}
+		}
+
+		/* Add the estimated encoding cost of the code length code histogram. */
+		bits += float64(18 + 2*max_depth)
+
+		/* Add the entropy of the code length code histogram. */
+		bits += bitsEntropy(depth_histo[:], codeLengthCodes)
+	}
+
+	return bits
+}
+
+func populationCostCommand(histogram *histogramCommand) float64 {
+	var data_size uint = histogramDataSizeCommand()
+	var count int = 0
+	var s [5]uint
+	var bits float64 = 0.0
+	var i uint
+	if histogram.total_count_ == 0 {
+		return kOneSymbolHistogramCost
+	}
+
+	for i = 0; i < data_size; i++ {
+		if histogram.data_[i] > 0 {
+			s[count] = i
+			count++
+			if count > 4 {
+				break
+			}
+		}
+	}
+
+	if count == 1 {
+		return kOneSymbolHistogramCost
+	}
+
+	if count == 2 {
+		return kTwoSymbolHistogramCost + float64(histogram.total_count_)
+	}
+
+	if count == 3 {
+		var histo0 uint32 = histogram.data_[s[0]]
+		var histo1 uint32 = histogram.data_[s[1]]
+		var histo2 uint32 = histogram.data_[s[2]]
+		var histomax uint32 = brotli_max_uint32_t(histo0, brotli_max_uint32_t(histo1, histo2))
+		return kThreeSymbolHistogramCost + 2*(float64(histo0)+float64(histo1)+float64(histo2)) - float64(histomax)
+	}
+
+	if count == 4 {
+		var histo [4]uint32
+		var h23 uint32
+		var histomax uint32
+		for i = 0; i < 4; i++ {
+			histo[i] = histogram.data_[s[i]]
+		}
+
+		/* Sort */
+		for i = 0; i < 4; i++ {
+			var j uint
+			for j = i + 1; j < 4; j++ {
+				if histo[j] > histo[i] {
+					var tmp uint32 = histo[j]
+					histo[j] = histo[i]
+					histo[i] = tmp
+				}
+			}
+		}
+
+		h23 = histo[2] + histo[3]
+		histomax = brotli_max_uint32_t(h23, histo[0])
+		return kFourSymbolHistogramCost + 3*float64(h23) + 2*(float64(histo[0])+float64(histo[1])) - float64(histomax)
+	}
+	{
+		var max_depth uint = 1
+		var depth_histo = [codeLengthCodes]uint32{0}
+		/* In this loop we compute the entropy of the histogram and simultaneously
+		   build a simplified histogram of the code length codes where we use the
+		   zero repeat code 17, but we don't use the non-zero repeat code 16. */
+
+		var log2total float64 = fastLog2(histogram.total_count_)
+		for i = 0; i < data_size; {
+			if histogram.data_[i] > 0 {
+				var log2p float64 = log2total - fastLog2(uint(histogram.data_[i]))
+				/* Compute -log2(P(symbol)) = -log2(count(symbol)/total_count) =
+				   = log2(total_count) - log2(count(symbol)) */
+
+				var depth uint = uint(log2p + 0.5)
+				/* Approximate the bit depth by round(-log2(P(symbol))) */
+				bits += float64(histogram.data_[i]) * log2p
+
+				if depth > 15 {
+					depth = 15
+				}
+
+				if depth > max_depth {
+					max_depth = depth
+				}
+
+				depth_histo[depth]++
+				i++
+			} else {
+				var reps uint32 = 1
+				/* Compute the run length of zeros and add the appropriate number of 0
+				   and 17 code length codes to the code length code histogram. */
+
+				var k uint
+				for k = i + 1; k < data_size && histogram.data_[k] == 0; k++ {
+					reps++
+				}
+
+				i += uint(reps)
+				if i == data_size {
+					/* Don't add any cost for the last zero run, since these are encoded
+					   only implicitly. */
+					break
+				}
+
+				if reps < 3 {
+					depth_histo[0] += reps
+				} else {
+					reps -= 2
+					for reps > 0 {
+						depth_histo[repeatZeroCodeLength]++
+
+						/* Add the 3 extra bits for the 17 code length code. */
+						bits += 3
+
+						reps >>= 3
+					}
+				}
+			}
+		}
+
+		/* Add the estimated encoding cost of the code length code histogram. */
+		bits += float64(18 + 2*max_depth)
+
+		/* Add the entropy of the code length code histogram. */
+		bits += bitsEntropy(depth_histo[:], codeLengthCodes)
+	}
+
+	return bits
+}
+
+func populationCostDistance(histogram *histogramDistance) float64 {
+	var data_size uint = histogramDataSizeDistance()
+	var count int = 0
+	var s [5]uint
+	var bits float64 = 0.0
+	var i uint
+	if histogram.total_count_ == 0 {
+		return kOneSymbolHistogramCost
+	}
+
+	for i = 0; i < data_size; i++ {
+		if histogram.data_[i] > 0 {
+			s[count] = i
+			count++
+			if count > 4 {
+				break
+			}
+		}
+	}
+
+	if count == 1 {
+		return kOneSymbolHistogramCost
+	}
+
+	if count == 2 {
+		return kTwoSymbolHistogramCost + float64(histogram.total_count_)
+	}
+
+	if count == 3 {
+		var histo0 uint32 = histogram.data_[s[0]]
+		var histo1 uint32 = histogram.data_[s[1]]
+		var histo2 uint32 = histogram.data_[s[2]]
+		var histomax uint32 = brotli_max_uint32_t(histo0, brotli_max_uint32_t(histo1, histo2))
+		return kThreeSymbolHistogramCost + 2*(float64(histo0)+float64(histo1)+float64(histo2)) - float64(histomax)
+	}
+
+	if count == 4 {
+		var histo [4]uint32
+		var h23 uint32
+		var histomax uint32
+		for i = 0; i < 4; i++ {
+			histo[i] = histogram.data_[s[i]]
+		}
+
+		/* Sort */
+		for i = 0; i < 4; i++ {
+			var j uint
+			for j = i + 1; j < 4; j++ {
+				if histo[j] > histo[i] {
+					var tmp uint32 = histo[j]
+					histo[j] = histo[i]
+					histo[i] = tmp
+				}
+			}
+		}
+
+		h23 = histo[2] + histo[3]
+		histomax = brotli_max_uint32_t(h23, histo[0])
+		return kFourSymbolHistogramCost + 3*float64(h23) + 2*(float64(histo[0])+float64(histo[1])) - float64(histomax)
+	}
+	{
+		var max_depth uint = 1
+		var depth_histo = [codeLengthCodes]uint32{0}
+		/* In this loop we compute the entropy of the histogram and simultaneously
+		   build a simplified histogram of the code length codes where we use the
+		   zero repeat code 17, but we don't use the non-zero repeat code 16. */
+
+		var log2total float64 = fastLog2(histogram.total_count_)
+		for i = 0; i < data_size; {
+			if histogram.data_[i] > 0 {
+				var log2p float64 = log2total - fastLog2(uint(histogram.data_[i]))
+				/* Compute -log2(P(symbol)) = -log2(count(symbol)/total_count) =
+				   = log2(total_count) - log2(count(symbol)) */
+
+				var depth uint = uint(log2p + 0.5)
+				/* Approximate the bit depth by round(-log2(P(symbol))) */
+				bits += float64(histogram.data_[i]) * log2p
+
+				if depth > 15 {
+					depth = 15
+				}
+
+				if depth > max_depth {
+					max_depth = depth
+				}
+
+				depth_histo[depth]++
+				i++
+			} else {
+				var reps uint32 = 1
+				/* Compute the run length of zeros and add the appropriate number of 0
+				   and 17 code length codes to the code length code histogram. */
+
+				var k uint
+				for k = i + 1; k < data_size && histogram.data_[k] == 0; k++ {
+					reps++
+				}
+
+				i += uint(reps)
+				if i == data_size {
+					/* Don't add any cost for the last zero run, since these are encoded
+					   only implicitly. */
+					break
+				}
+
+				if reps < 3 {
+					depth_histo[0] += reps
+				} else {
+					reps -= 2
+					for reps > 0 {
+						depth_histo[repeatZeroCodeLength]++
+
+						/* Add the 3 extra bits for the 17 code length code. */
+						bits += 3
+
+						reps >>= 3
+					}
+				}
+			}
+		}
+
+		/* Add the estimated encoding cost of the code length code histogram. */
+		bits += float64(18 + 2*max_depth)
+
+		/* Add the entropy of the code length code histogram. */
+		bits += bitsEntropy(depth_histo[:], codeLengthCodes)
+	}
+
+	return bits
+}

vendor/github.com/andybalholm/brotli/bit_reader.go

@@ -0,0 +1,266 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Bit reading helpers */
+
+const shortFillBitWindowRead = (8 >> 1)
+
+var kBitMask = [33]uint32{
+	0x00000000,
+	0x00000001,
+	0x00000003,
+	0x00000007,
+	0x0000000F,
+	0x0000001F,
+	0x0000003F,
+	0x0000007F,
+	0x000000FF,
+	0x000001FF,
+	0x000003FF,
+	0x000007FF,
+	0x00000FFF,
+	0x00001FFF,
+	0x00003FFF,
+	0x00007FFF,
+	0x0000FFFF,
+	0x0001FFFF,
+	0x0003FFFF,
+	0x0007FFFF,
+	0x000FFFFF,
+	0x001FFFFF,
+	0x003FFFFF,
+	0x007FFFFF,
+	0x00FFFFFF,
+	0x01FFFFFF,
+	0x03FFFFFF,
+	0x07FFFFFF,
+	0x0FFFFFFF,
+	0x1FFFFFFF,
+	0x3FFFFFFF,
+	0x7FFFFFFF,
+	0xFFFFFFFF,
+}
+
+func bitMask(n uint32) uint32 {
+	return kBitMask[n]
+}
+
+type bitReader struct {
+	val_      uint64
+	bit_pos_  uint32
+	input     []byte
+	input_len uint
+	byte_pos  uint
+}
+
+type bitReaderState struct {
+	val_      uint64
+	bit_pos_  uint32
+	input     []byte
+	input_len uint
+	byte_pos  uint
+}
+
+/* Initializes the BrotliBitReader fields. */
+
+/* Ensures that accumulator is not empty.
+   May consume up to sizeof(brotli_reg_t) - 1 bytes of input.
+   Returns false if data is required but there is no input available.
+   For BROTLI_ALIGNED_READ this function also prepares bit reader for aligned
+   reading. */
+func bitReaderSaveState(from *bitReader, to *bitReaderState) {
+	to.val_ = from.val_
+	to.bit_pos_ = from.bit_pos_
+	to.input = from.input
+	to.input_len = from.input_len
+	to.byte_pos = from.byte_pos
+}
+
+func bitReaderRestoreState(to *bitReader, from *bitReaderState) {
+	to.val_ = from.val_
+	to.bit_pos_ = from.bit_pos_
+	to.input = from.input
+	to.input_len = from.input_len
+	to.byte_pos = from.byte_pos
+}
+
+func getAvailableBits(br *bitReader) uint32 {
+	return 64 - br.bit_pos_
+}
+
+/* Returns amount of unread bytes the bit reader still has buffered from the
+   BrotliInput, including whole bytes in br->val_. */
+func getRemainingBytes(br *bitReader) uint {
+	return uint(uint32(br.input_len-br.byte_pos) + (getAvailableBits(br) >> 3))
+}
+
+/* Checks if there is at least |num| bytes left in the input ring-buffer
+   (excluding the bits remaining in br->val_). */
+func checkInputAmount(br *bitReader, num uint) bool {
+	return br.input_len-br.byte_pos >= num
+}
+
+/* Guarantees that there are at least |n_bits| + 1 bits in accumulator.
+   Precondition: accumulator contains at least 1 bit.
+   |n_bits| should be in the range [1..24] for regular build. For portable
+   non-64-bit little-endian build only 16 bits are safe to request. */
+func fillBitWindow(br *bitReader, n_bits uint32) {
+	if br.bit_pos_ >= 32 {
+		br.val_ >>= 32
+		br.bit_pos_ ^= 32 /* here same as -= 32 because of the if condition */
+		br.val_ |= (uint64(binary.LittleEndian.Uint32(br.input[br.byte_pos:]))) << 32
+		br.byte_pos += 4
+	}
+}
+
+/* Mostly like BrotliFillBitWindow, but guarantees only 16 bits and reads no
+   more than BROTLI_SHORT_FILL_BIT_WINDOW_READ bytes of input. */
+func fillBitWindow16(br *bitReader) {
+	fillBitWindow(br, 17)
+}
+
+/* Tries to pull one byte of input to accumulator.
+   Returns false if there is no input available. */
+func pullByte(br *bitReader) bool {
+	if br.byte_pos == br.input_len {
+		return false
+	}
+
+	br.val_ >>= 8
+	br.val_ |= (uint64(br.input[br.byte_pos])) << 56
+	br.bit_pos_ -= 8
+	br.byte_pos++
+	return true
+}
+
+/* Returns currently available bits.
+   The number of valid bits could be calculated by BrotliGetAvailableBits. */
+func getBitsUnmasked(br *bitReader) uint64 {
+	return br.val_ >> br.bit_pos_
+}
+
+/* Like BrotliGetBits, but does not mask the result.
+   The result contains at least 16 valid bits. */
+func get16BitsUnmasked(br *bitReader) uint32 {
+	fillBitWindow(br, 16)
+	return uint32(getBitsUnmasked(br))
+}
+
+/* Returns the specified number of bits from |br| without advancing bit
+   position. */
+func getBits(br *bitReader, n_bits uint32) uint32 {
+	fillBitWindow(br, n_bits)
+	return uint32(getBitsUnmasked(br)) & bitMask(n_bits)
+}
+
+/* Tries to peek the specified amount of bits. Returns false, if there
+   is not enough input. */
+func safeGetBits(br *bitReader, n_bits uint32, val *uint32) bool {
+	for getAvailableBits(br) < n_bits {
+		if !pullByte(br) {
+			return false
+		}
+	}
+
+	*val = uint32(getBitsUnmasked(br)) & bitMask(n_bits)
+	return true
+}
+
+/* Advances the bit pos by |n_bits|. */
+func dropBits(br *bitReader, n_bits uint32) {
+	br.bit_pos_ += n_bits
+}
+
+func bitReaderUnload(br *bitReader) {
+	var unused_bytes uint32 = getAvailableBits(br) >> 3
+	var unused_bits uint32 = unused_bytes << 3
+	br.byte_pos -= uint(unused_bytes)
+	if unused_bits == 64 {
+		br.val_ = 0
+	} else {
+		br.val_ <<= unused_bits
+	}
+
+	br.bit_pos_ += unused_bits
+}
+
+/* Reads the specified number of bits from |br| and advances the bit pos.
+   Precondition: accumulator MUST contain at least |n_bits|. */
+func takeBits(br *bitReader, n_bits uint32, val *uint32) {
+	*val = uint32(getBitsUnmasked(br)) & bitMask(n_bits)
+	dropBits(br, n_bits)
+}
+
+/* Reads the specified number of bits from |br| and advances the bit pos.
+   Assumes that there is enough input to perform BrotliFillBitWindow. */
+func readBits(br *bitReader, n_bits uint32) uint32 {
+	var val uint32
+	fillBitWindow(br, n_bits)
+	takeBits(br, n_bits, &val)
+	return val
+}
+
+/* Tries to read the specified amount of bits. Returns false, if there
+   is not enough input. |n_bits| MUST be positive. */
+func safeReadBits(br *bitReader, n_bits uint32, val *uint32) bool {
+	for getAvailableBits(br) < n_bits {
+		if !pullByte(br) {
+			return false
+		}
+	}
+
+	takeBits(br, n_bits, val)
+	return true
+}
+
+/* Advances the bit reader position to the next byte boundary and verifies
+   that any skipped bits are set to zero. */
+func bitReaderJumpToByteBoundary(br *bitReader) bool {
+	var pad_bits_count uint32 = getAvailableBits(br) & 0x7
+	var pad_bits uint32 = 0
+	if pad_bits_count != 0 {
+		takeBits(br, pad_bits_count, &pad_bits)
+	}
+
+	return pad_bits == 0
+}
+
+/* Copies remaining input bytes stored in the bit reader to the output. Value
+   |num| may not be larger than BrotliGetRemainingBytes. The bit reader must be
+   warmed up again after this. */
+func copyBytes(dest []byte, br *bitReader, num uint) {
+	for getAvailableBits(br) >= 8 && num > 0 {
+		dest[0] = byte(getBitsUnmasked(br))
+		dropBits(br, 8)
+		dest = dest[1:]
+		num--
+	}
+
+	copy(dest, br.input[br.byte_pos:][:num])
+	br.byte_pos += num
+}
+
+func initBitReader(br *bitReader) {
+	br.val_ = 0
+	br.bit_pos_ = 64
+}
+
+func warmupBitReader(br *bitReader) bool {
+	/* Fixing alignment after unaligned BrotliFillWindow would result accumulator
+	   overflow. If unalignment is caused by BrotliSafeReadBits, then there is
+	   enough space in accumulator to fix alignment. */
+	if getAvailableBits(br) == 0 {
+		if !pullByte(br) {
+			return false
+		}
+	}
+
+	return true
+}

vendor/github.com/andybalholm/brotli/block_splitter.go

@@ -0,0 +1,144 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Block split point selection utilities. */
+
+type blockSplit struct {
+	num_types          uint
+	num_blocks         uint
+	types              []byte
+	lengths            []uint32
+	types_alloc_size   uint
+	lengths_alloc_size uint
+}
+
+const (
+	kMaxLiteralHistograms        uint    = 100
+	kMaxCommandHistograms        uint    = 50
+	kLiteralBlockSwitchCost      float64 = 28.1
+	kCommandBlockSwitchCost      float64 = 13.5
+	kDistanceBlockSwitchCost     float64 = 14.6
+	kLiteralStrideLength         uint    = 70
+	kCommandStrideLength         uint    = 40
+	kSymbolsPerLiteralHistogram  uint    = 544
+	kSymbolsPerCommandHistogram  uint    = 530
+	kSymbolsPerDistanceHistogram uint    = 544
+	kMinLengthForBlockSplitting  uint    = 128
+	kIterMulForRefining          uint    = 2
+	kMinItersForRefining         uint    = 100
+)
+
+func countLiterals(cmds []command) uint {
+	var total_length uint = 0
+	/* Count how many we have. */
+
+	for i := range cmds {
+		total_length += uint(cmds[i].insert_len_)
+	}
+
+	return total_length
+}
+
+func copyLiteralsToByteArray(cmds []command, data []byte, offset uint, mask uint, literals []byte) {
+	var pos uint = 0
+	var from_pos uint = offset & mask
+	for i := range cmds {
+		var insert_len uint = uint(cmds[i].insert_len_)
+		if from_pos+insert_len > mask {
+			var head_size uint = mask + 1 - from_pos
+			copy(literals[pos:], data[from_pos:][:head_size])
+			from_pos = 0
+			pos += head_size
+			insert_len -= head_size
+		}
+
+		if insert_len > 0 {
+			copy(literals[pos:], data[from_pos:][:insert_len])
+			pos += insert_len
+		}
+
+		from_pos = uint((uint32(from_pos+insert_len) + commandCopyLen(&cmds[i])) & uint32(mask))
+	}
+}
+
+func myRand(seed *uint32) uint32 {
+	/* Initial seed should be 7. In this case, loop length is (1 << 29). */
+	*seed *= 16807
+
+	return *seed
+}
+
+func bitCost(count uint) float64 {
+	if count == 0 {
+		return -2.0
+	} else {
+		return fastLog2(count)
+	}
+}
+
+const histogramsPerBatch = 64
+
+const clustersPerBatch = 16
+
+func initBlockSplit(self *blockSplit) {
+	self.num_types = 0
+	self.num_blocks = 0
+	self.types = self.types[:0]
+	self.lengths = self.lengths[:0]
+	self.types_alloc_size = 0
+	self.lengths_alloc_size = 0
+}
+
+func splitBlock(cmds []command, data []byte, pos uint, mask uint, params *encoderParams, literal_split *blockSplit, insert_and_copy_split *blockSplit, dist_split *blockSplit) {
+	{
+		var literals_count uint = countLiterals(cmds)
+		var literals []byte = make([]byte, literals_count)
+
+		/* Create a continuous array of literals. */
+		copyLiteralsToByteArray(cmds, data, pos, mask, literals)
+
+		/* Create the block split on the array of literals.
+		   Literal histograms have alphabet size 256. */
+		splitByteVectorLiteral(literals, literals_count, kSymbolsPerLiteralHistogram, kMaxLiteralHistograms, kLiteralStrideLength, kLiteralBlockSwitchCost, params, literal_split)
+
+		literals = nil
+	}
+	{
+		var insert_and_copy_codes []uint16 = make([]uint16, len(cmds))
+		/* Compute prefix codes for commands. */
+
+		for i := range cmds {
+			insert_and_copy_codes[i] = cmds[i].cmd_prefix_
+		}
+
+		/* Create the block split on the array of command prefixes. */
+		splitByteVectorCommand(insert_and_copy_codes, kSymbolsPerCommandHistogram, kMaxCommandHistograms, kCommandStrideLength, kCommandBlockSwitchCost, params, insert_and_copy_split)
+
+		/* TODO: reuse for distances? */
+
+		insert_and_copy_codes = nil
+	}
+	{
+		var distance_prefixes []uint16 = make([]uint16, len(cmds))
+		var j uint = 0
+		/* Create a continuous array of distance prefixes. */
+
+		for i := range cmds {
+			var cmd *command = &cmds[i]
+			if commandCopyLen(cmd) != 0 && cmd.cmd_prefix_ >= 128 {
+				distance_prefixes[j] = cmd.dist_prefix_ & 0x3FF
+				j++
+			}
+		}
+
+		/* Create the block split on the array of distance prefixes. */
+		splitByteVectorDistance(distance_prefixes, j, kSymbolsPerDistanceHistogram, kMaxCommandHistograms, kCommandStrideLength, kDistanceBlockSwitchCost, params, dist_split)
+
+		distance_prefixes = nil
+	}
+}

vendor/github.com/andybalholm/brotli/block_splitter_command.go

@@ -0,0 +1,434 @@
+package brotli
+
+import "math"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func initialEntropyCodesCommand(data []uint16, length uint, stride uint, num_histograms uint, histograms []histogramCommand) {
+	var seed uint32 = 7
+	var block_length uint = length / num_histograms
+	var i uint
+	clearHistogramsCommand(histograms, num_histograms)
+	for i = 0; i < num_histograms; i++ {
+		var pos uint = length * i / num_histograms
+		if i != 0 {
+			pos += uint(myRand(&seed) % uint32(block_length))
+		}
+
+		if pos+stride >= length {
+			pos = length - stride - 1
+		}
+
+		histogramAddVectorCommand(&histograms[i], data[pos:], stride)
+	}
+}
+
+func randomSampleCommand(seed *uint32, data []uint16, length uint, stride uint, sample *histogramCommand) {
+	var pos uint = 0
+	if stride >= length {
+		stride = length
+	} else {
+		pos = uint(myRand(seed) % uint32(length-stride+1))
+	}
+
+	histogramAddVectorCommand(sample, data[pos:], stride)
+}
+
+func refineEntropyCodesCommand(data []uint16, length uint, stride uint, num_histograms uint, histograms []histogramCommand) {
+	var iters uint = kIterMulForRefining*length/stride + kMinItersForRefining
+	var seed uint32 = 7
+	var iter uint
+	iters = ((iters + num_histograms - 1) / num_histograms) * num_histograms
+	for iter = 0; iter < iters; iter++ {
+		var sample histogramCommand
+		histogramClearCommand(&sample)
+		randomSampleCommand(&seed, data, length, stride, &sample)
+		histogramAddHistogramCommand(&histograms[iter%num_histograms], &sample)
+	}
+}
+
+/* Assigns a block id from the range [0, num_histograms) to each data element
+   in data[0..length) and fills in block_id[0..length) with the assigned values.
+   Returns the number of blocks, i.e. one plus the number of block switches. */
+func findBlocksCommand(data []uint16, length uint, block_switch_bitcost float64, num_histograms uint, histograms []histogramCommand, insert_cost []float64, cost []float64, switch_signal []byte, block_id []byte) uint {
+	var data_size uint = histogramDataSizeCommand()
+	var bitmaplen uint = (num_histograms + 7) >> 3
+	var num_blocks uint = 1
+	var i uint
+	var j uint
+	assert(num_histograms <= 256)
+	if num_histograms <= 1 {
+		for i = 0; i < length; i++ {
+			block_id[i] = 0
+		}
+
+		return 1
+	}
+
+	for i := 0; i < int(data_size*num_histograms); i++ {
+		insert_cost[i] = 0
+	}
+	for i = 0; i < num_histograms; i++ {
+		insert_cost[i] = fastLog2(uint(uint32(histograms[i].total_count_)))
+	}
+
+	for i = data_size; i != 0; {
+		i--
+		for j = 0; j < num_histograms; j++ {
+			insert_cost[i*num_histograms+j] = insert_cost[j] - bitCost(uint(histograms[j].data_[i]))
+		}
+	}
+
+	for i := 0; i < int(num_histograms); i++ {
+		cost[i] = 0
+	}
+	for i := 0; i < int(length*bitmaplen); i++ {
+		switch_signal[i] = 0
+	}
+
+	/* After each iteration of this loop, cost[k] will contain the difference
+	   between the minimum cost of arriving at the current byte position using
+	   entropy code k, and the minimum cost of arriving at the current byte
+	   position. This difference is capped at the block switch cost, and if it
+	   reaches block switch cost, it means that when we trace back from the last
+	   position, we need to switch here. */
+	for i = 0; i < length; i++ {
+		var byte_ix uint = i
+		var ix uint = byte_ix * bitmaplen
+		var insert_cost_ix uint = uint(data[byte_ix]) * num_histograms
+		var min_cost float64 = 1e99
+		var block_switch_cost float64 = block_switch_bitcost
+		var k uint
+		for k = 0; k < num_histograms; k++ {
+			/* We are coding the symbol in data[byte_ix] with entropy code k. */
+			cost[k] += insert_cost[insert_cost_ix+k]
+
+			if cost[k] < min_cost {
+				min_cost = cost[k]
+				block_id[byte_ix] = byte(k)
+			}
+		}
+
+		/* More blocks for the beginning. */
+		if byte_ix < 2000 {
+			block_switch_cost *= 0.77 + 0.07*float64(byte_ix)/2000
+		}
+
+		for k = 0; k < num_histograms; k++ {
+			cost[k] -= min_cost
+			if cost[k] >= block_switch_cost {
+				var mask byte = byte(1 << (k & 7))
+				cost[k] = block_switch_cost
+				assert(k>>3 < bitmaplen)
+				switch_signal[ix+(k>>3)] |= mask
+				/* Trace back from the last position and switch at the marked places. */
+			}
+		}
+	}
+	{
+		var byte_ix uint = length - 1
+		var ix uint = byte_ix * bitmaplen
+		var cur_id byte = block_id[byte_ix]
+		for byte_ix > 0 {
+			var mask byte = byte(1 << (cur_id & 7))
+			assert(uint(cur_id)>>3 < bitmaplen)
+			byte_ix--
+			ix -= bitmaplen
+			if switch_signal[ix+uint(cur_id>>3)]&mask != 0 {
+				if cur_id != block_id[byte_ix] {
+					cur_id = block_id[byte_ix]
+					num_blocks++
+				}
+			}
+
+			block_id[byte_ix] = cur_id
+		}
+	}
+
+	return num_blocks
+}
+
+var remapBlockIdsCommand_kInvalidId uint16 = 256
+
+func remapBlockIdsCommand(block_ids []byte, length uint, new_id []uint16, num_histograms uint) uint {
+	var next_id uint16 = 0
+	var i uint
+	for i = 0; i < num_histograms; i++ {
+		new_id[i] = remapBlockIdsCommand_kInvalidId
+	}
+
+	for i = 0; i < length; i++ {
+		assert(uint(block_ids[i]) < num_histograms)
+		if new_id[block_ids[i]] == remapBlockIdsCommand_kInvalidId {
+			new_id[block_ids[i]] = next_id
+			next_id++
+		}
+	}
+
+	for i = 0; i < length; i++ {
+		block_ids[i] = byte(new_id[block_ids[i]])
+		assert(uint(block_ids[i]) < num_histograms)
+	}
+
+	assert(uint(next_id) <= num_histograms)
+	return uint(next_id)
+}
+
+func buildBlockHistogramsCommand(data []uint16, length uint, block_ids []byte, num_histograms uint, histograms []histogramCommand) {
+	var i uint
+	clearHistogramsCommand(histograms, num_histograms)
+	for i = 0; i < length; i++ {
+		histogramAddCommand(&histograms[block_ids[i]], uint(data[i]))
+	}
+}
+
+var clusterBlocksCommand_kInvalidIndex uint32 = math.MaxUint32
+
+func clusterBlocksCommand(data []uint16, length uint, num_blocks uint, block_ids []byte, split *blockSplit) {
+	var histogram_symbols []uint32 = make([]uint32, num_blocks)
+	var block_lengths []uint32 = make([]uint32, num_blocks)
+	var expected_num_clusters uint = clustersPerBatch * (num_blocks + histogramsPerBatch - 1) / histogramsPerBatch
+	var all_histograms_size uint = 0
+	var all_histograms_capacity uint = expected_num_clusters
+	var all_histograms []histogramCommand = make([]histogramCommand, all_histograms_capacity)
+	var cluster_size_size uint = 0
+	var cluster_size_capacity uint = expected_num_clusters
+	var cluster_size []uint32 = make([]uint32, cluster_size_capacity)
+	var num_clusters uint = 0
+	var histograms []histogramCommand = make([]histogramCommand, brotli_min_size_t(num_blocks, histogramsPerBatch))
+	var max_num_pairs uint = histogramsPerBatch * histogramsPerBatch / 2
+	var pairs_capacity uint = max_num_pairs + 1
+	var pairs []histogramPair = make([]histogramPair, pairs_capacity)
+	var pos uint = 0
+	var clusters []uint32
+	var num_final_clusters uint
+	var new_index []uint32
+	var i uint
+	var sizes = [histogramsPerBatch]uint32{0}
+	var new_clusters = [histogramsPerBatch]uint32{0}
+	var symbols = [histogramsPerBatch]uint32{0}
+	var remap = [histogramsPerBatch]uint32{0}
+
+	for i := 0; i < int(num_blocks); i++ {
+		block_lengths[i] = 0
+	}
+	{
+		var block_idx uint = 0
+		for i = 0; i < length; i++ {
+			assert(block_idx < num_blocks)
+			block_lengths[block_idx]++
+			if i+1 == length || block_ids[i] != block_ids[i+1] {
+				block_idx++
+			}
+		}
+
+		assert(block_idx == num_blocks)
+	}
+
+	for i = 0; i < num_blocks; i += histogramsPerBatch {
+		var num_to_combine uint = brotli_min_size_t(num_blocks-i, histogramsPerBatch)
+		var num_new_clusters uint
+		var j uint
+		for j = 0; j < num_to_combine; j++ {
+			var k uint
+			histogramClearCommand(&histograms[j])
+			for k = 0; uint32(k) < block_lengths[i+j]; k++ {
+				histogramAddCommand(&histograms[j], uint(data[pos]))
+				pos++
+			}
+
+			histograms[j].bit_cost_ = populationCostCommand(&histograms[j])
+			new_clusters[j] = uint32(j)
+			symbols[j] = uint32(j)
+			sizes[j] = 1
+		}
+
+		num_new_clusters = histogramCombineCommand(histograms, sizes[:], symbols[:], new_clusters[:], []histogramPair(pairs), num_to_combine, num_to_combine, histogramsPerBatch, max_num_pairs)
+		if all_histograms_capacity < (all_histograms_size + num_new_clusters) {
+			var _new_size uint
+			if all_histograms_capacity == 0 {
+				_new_size = all_histograms_size + num_new_clusters
+			} else {
+				_new_size = all_histograms_capacity
+			}
+			var new_array []histogramCommand
+			for _new_size < (all_histograms_size + num_new_clusters) {
+				_new_size *= 2
+			}
+			new_array = make([]histogramCommand, _new_size)
+			if all_histograms_capacity != 0 {
+				copy(new_array, all_histograms[:all_histograms_capacity])
+			}
+
+			all_histograms = new_array
+			all_histograms_capacity = _new_size
+		}
+
+		brotli_ensure_capacity_uint32_t(&cluster_size, &cluster_size_capacity, cluster_size_size+num_new_clusters)
+		for j = 0; j < num_new_clusters; j++ {
+			all_histograms[all_histograms_size] = histograms[new_clusters[j]]
+			all_histograms_size++
+			cluster_size[cluster_size_size] = sizes[new_clusters[j]]
+			cluster_size_size++
+			remap[new_clusters[j]] = uint32(j)
+		}
+
+		for j = 0; j < num_to_combine; j++ {
+			histogram_symbols[i+j] = uint32(num_clusters) + remap[symbols[j]]
+		}
+
+		num_clusters += num_new_clusters
+		assert(num_clusters == cluster_size_size)
+		assert(num_clusters == all_histograms_size)
+	}
+
+	histograms = nil
+
+	max_num_pairs = brotli_min_size_t(64*num_clusters, (num_clusters/2)*num_clusters)
+	if pairs_capacity < max_num_pairs+1 {
+		pairs = nil
+		pairs = make([]histogramPair, (max_num_pairs + 1))
+	}
+
+	clusters = make([]uint32, num_clusters)
+	for i = 0; i < num_clusters; i++ {
+		clusters[i] = uint32(i)
+	}
+
+	num_final_clusters = histogramCombineCommand(all_histograms, cluster_size, histogram_symbols, clusters, pairs, num_clusters, num_blocks, maxNumberOfBlockTypes, max_num_pairs)
+	pairs = nil
+	cluster_size = nil
+
+	new_index = make([]uint32, num_clusters)
+	for i = 0; i < num_clusters; i++ {
+		new_index[i] = clusterBlocksCommand_kInvalidIndex
+	}
+	pos = 0
+	{
+		var next_index uint32 = 0
+		for i = 0; i < num_blocks; i++ {
+			var histo histogramCommand
+			var j uint
+			var best_out uint32
+			var best_bits float64
+			histogramClearCommand(&histo)
+			for j = 0; uint32(j) < block_lengths[i]; j++ {
+				histogramAddCommand(&histo, uint(data[pos]))
+				pos++
+			}
+
+			if i == 0 {
+				best_out = histogram_symbols[0]
+			} else {
+				best_out = histogram_symbols[i-1]
+			}
+			best_bits = histogramBitCostDistanceCommand(&histo, &all_histograms[best_out])
+			for j = 0; j < num_final_clusters; j++ {
+				var cur_bits float64 = histogramBitCostDistanceCommand(&histo, &all_histograms[clusters[j]])
+				if cur_bits < best_bits {
+					best_bits = cur_bits
+					best_out = clusters[j]
+				}
+			}
+
+			histogram_symbols[i] = best_out
+			if new_index[best_out] == clusterBlocksCommand_kInvalidIndex {
+				new_index[best_out] = next_index
+				next_index++
+			}
+		}
+	}
+
+	clusters = nil
+	all_histograms = nil
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, num_blocks)
+	{
+		var cur_length uint32 = 0
+		var block_idx uint = 0
+		var max_type byte = 0
+		for i = 0; i < num_blocks; i++ {
+			cur_length += block_lengths[i]
+			if i+1 == num_blocks || histogram_symbols[i] != histogram_symbols[i+1] {
+				var id byte = byte(new_index[histogram_symbols[i]])
+				split.types[block_idx] = id
+				split.lengths[block_idx] = cur_length
+				max_type = brotli_max_uint8_t(max_type, id)
+				cur_length = 0
+				block_idx++
+			}
+		}
+
+		split.num_blocks = block_idx
+		split.num_types = uint(max_type) + 1
+	}
+
+	new_index = nil
+	block_lengths = nil
+	histogram_symbols = nil
+}
+
+func splitByteVectorCommand(data []uint16, literals_per_histogram uint, max_histograms uint, sampling_stride_length uint, block_switch_cost float64, params *encoderParams, split *blockSplit) {
+	length := uint(len(data))
+	var data_size uint = histogramDataSizeCommand()
+	var num_histograms uint = length/literals_per_histogram + 1
+	var histograms []histogramCommand
+	if num_histograms > max_histograms {
+		num_histograms = max_histograms
+	}
+
+	if length == 0 {
+		split.num_types = 1
+		return
+	} else if length < kMinLengthForBlockSplitting {
+		brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, split.num_blocks+1)
+		brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, split.num_blocks+1)
+		split.num_types = 1
+		split.types[split.num_blocks] = 0
+		split.lengths[split.num_blocks] = uint32(length)
+		split.num_blocks++
+		return
+	}
+
+	histograms = make([]histogramCommand, num_histograms)
+
+	/* Find good entropy codes. */
+	initialEntropyCodesCommand(data, length, sampling_stride_length, num_histograms, histograms)
+
+	refineEntropyCodesCommand(data, length, sampling_stride_length, num_histograms, histograms)
+	{
+		var block_ids []byte = make([]byte, length)
+		var num_blocks uint = 0
+		var bitmaplen uint = (num_histograms + 7) >> 3
+		var insert_cost []float64 = make([]float64, (data_size * num_histograms))
+		var cost []float64 = make([]float64, num_histograms)
+		var switch_signal []byte = make([]byte, (length * bitmaplen))
+		var new_id []uint16 = make([]uint16, num_histograms)
+		var iters uint
+		if params.quality < hqZopflificationQuality {
+			iters = 3
+		} else {
+			iters = 10
+		}
+		/* Find a good path through literals with the good entropy codes. */
+
+		var i uint
+		for i = 0; i < iters; i++ {
+			num_blocks = findBlocksCommand(data, length, block_switch_cost, num_histograms, histograms, insert_cost, cost, switch_signal, block_ids)
+			num_histograms = remapBlockIdsCommand(block_ids, length, new_id, num_histograms)
+			buildBlockHistogramsCommand(data, length, block_ids, num_histograms, histograms)
+		}
+
+		insert_cost = nil
+		cost = nil
+		switch_signal = nil
+		new_id = nil
+		histograms = nil
+		clusterBlocksCommand(data, length, num_blocks, block_ids, split)
+		block_ids = nil
+	}
+}

vendor/github.com/andybalholm/brotli/block_splitter_distance.go

@@ -0,0 +1,433 @@
+package brotli
+
+import "math"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func initialEntropyCodesDistance(data []uint16, length uint, stride uint, num_histograms uint, histograms []histogramDistance) {
+	var seed uint32 = 7
+	var block_length uint = length / num_histograms
+	var i uint
+	clearHistogramsDistance(histograms, num_histograms)
+	for i = 0; i < num_histograms; i++ {
+		var pos uint = length * i / num_histograms
+		if i != 0 {
+			pos += uint(myRand(&seed) % uint32(block_length))
+		}
+
+		if pos+stride >= length {
+			pos = length - stride - 1
+		}
+
+		histogramAddVectorDistance(&histograms[i], data[pos:], stride)
+	}
+}
+
+func randomSampleDistance(seed *uint32, data []uint16, length uint, stride uint, sample *histogramDistance) {
+	var pos uint = 0
+	if stride >= length {
+		stride = length
+	} else {
+		pos = uint(myRand(seed) % uint32(length-stride+1))
+	}
+
+	histogramAddVectorDistance(sample, data[pos:], stride)
+}
+
+func refineEntropyCodesDistance(data []uint16, length uint, stride uint, num_histograms uint, histograms []histogramDistance) {
+	var iters uint = kIterMulForRefining*length/stride + kMinItersForRefining
+	var seed uint32 = 7
+	var iter uint
+	iters = ((iters + num_histograms - 1) / num_histograms) * num_histograms
+	for iter = 0; iter < iters; iter++ {
+		var sample histogramDistance
+		histogramClearDistance(&sample)
+		randomSampleDistance(&seed, data, length, stride, &sample)
+		histogramAddHistogramDistance(&histograms[iter%num_histograms], &sample)
+	}
+}
+
+/* Assigns a block id from the range [0, num_histograms) to each data element
+   in data[0..length) and fills in block_id[0..length) with the assigned values.
+   Returns the number of blocks, i.e. one plus the number of block switches. */
+func findBlocksDistance(data []uint16, length uint, block_switch_bitcost float64, num_histograms uint, histograms []histogramDistance, insert_cost []float64, cost []float64, switch_signal []byte, block_id []byte) uint {
+	var data_size uint = histogramDataSizeDistance()
+	var bitmaplen uint = (num_histograms + 7) >> 3
+	var num_blocks uint = 1
+	var i uint
+	var j uint
+	assert(num_histograms <= 256)
+	if num_histograms <= 1 {
+		for i = 0; i < length; i++ {
+			block_id[i] = 0
+		}
+
+		return 1
+	}
+
+	for i := 0; i < int(data_size*num_histograms); i++ {
+		insert_cost[i] = 0
+	}
+	for i = 0; i < num_histograms; i++ {
+		insert_cost[i] = fastLog2(uint(uint32(histograms[i].total_count_)))
+	}
+
+	for i = data_size; i != 0; {
+		i--
+		for j = 0; j < num_histograms; j++ {
+			insert_cost[i*num_histograms+j] = insert_cost[j] - bitCost(uint(histograms[j].data_[i]))
+		}
+	}
+
+	for i := 0; i < int(num_histograms); i++ {
+		cost[i] = 0
+	}
+	for i := 0; i < int(length*bitmaplen); i++ {
+		switch_signal[i] = 0
+	}
+
+	/* After each iteration of this loop, cost[k] will contain the difference
+	   between the minimum cost of arriving at the current byte position using
+	   entropy code k, and the minimum cost of arriving at the current byte
+	   position. This difference is capped at the block switch cost, and if it
+	   reaches block switch cost, it means that when we trace back from the last
+	   position, we need to switch here. */
+	for i = 0; i < length; i++ {
+		var byte_ix uint = i
+		var ix uint = byte_ix * bitmaplen
+		var insert_cost_ix uint = uint(data[byte_ix]) * num_histograms
+		var min_cost float64 = 1e99
+		var block_switch_cost float64 = block_switch_bitcost
+		var k uint
+		for k = 0; k < num_histograms; k++ {
+			/* We are coding the symbol in data[byte_ix] with entropy code k. */
+			cost[k] += insert_cost[insert_cost_ix+k]
+
+			if cost[k] < min_cost {
+				min_cost = cost[k]
+				block_id[byte_ix] = byte(k)
+			}
+		}
+
+		/* More blocks for the beginning. */
+		if byte_ix < 2000 {
+			block_switch_cost *= 0.77 + 0.07*float64(byte_ix)/2000
+		}
+
+		for k = 0; k < num_histograms; k++ {
+			cost[k] -= min_cost
+			if cost[k] >= block_switch_cost {
+				var mask byte = byte(1 << (k & 7))
+				cost[k] = block_switch_cost
+				assert(k>>3 < bitmaplen)
+				switch_signal[ix+(k>>3)] |= mask
+				/* Trace back from the last position and switch at the marked places. */
+			}
+		}
+	}
+	{
+		var byte_ix uint = length - 1
+		var ix uint = byte_ix * bitmaplen
+		var cur_id byte = block_id[byte_ix]
+		for byte_ix > 0 {
+			var mask byte = byte(1 << (cur_id & 7))
+			assert(uint(cur_id)>>3 < bitmaplen)
+			byte_ix--
+			ix -= bitmaplen
+			if switch_signal[ix+uint(cur_id>>3)]&mask != 0 {
+				if cur_id != block_id[byte_ix] {
+					cur_id = block_id[byte_ix]
+					num_blocks++
+				}
+			}
+
+			block_id[byte_ix] = cur_id
+		}
+	}
+
+	return num_blocks
+}
+
+var remapBlockIdsDistance_kInvalidId uint16 = 256
+
+func remapBlockIdsDistance(block_ids []byte, length uint, new_id []uint16, num_histograms uint) uint {
+	var next_id uint16 = 0
+	var i uint
+	for i = 0; i < num_histograms; i++ {
+		new_id[i] = remapBlockIdsDistance_kInvalidId
+	}
+
+	for i = 0; i < length; i++ {
+		assert(uint(block_ids[i]) < num_histograms)
+		if new_id[block_ids[i]] == remapBlockIdsDistance_kInvalidId {
+			new_id[block_ids[i]] = next_id
+			next_id++
+		}
+	}
+
+	for i = 0; i < length; i++ {
+		block_ids[i] = byte(new_id[block_ids[i]])
+		assert(uint(block_ids[i]) < num_histograms)
+	}
+
+	assert(uint(next_id) <= num_histograms)
+	return uint(next_id)
+}
+
+func buildBlockHistogramsDistance(data []uint16, length uint, block_ids []byte, num_histograms uint, histograms []histogramDistance) {
+	var i uint
+	clearHistogramsDistance(histograms, num_histograms)
+	for i = 0; i < length; i++ {
+		histogramAddDistance(&histograms[block_ids[i]], uint(data[i]))
+	}
+}
+
+var clusterBlocksDistance_kInvalidIndex uint32 = math.MaxUint32
+
+func clusterBlocksDistance(data []uint16, length uint, num_blocks uint, block_ids []byte, split *blockSplit) {
+	var histogram_symbols []uint32 = make([]uint32, num_blocks)
+	var block_lengths []uint32 = make([]uint32, num_blocks)
+	var expected_num_clusters uint = clustersPerBatch * (num_blocks + histogramsPerBatch - 1) / histogramsPerBatch
+	var all_histograms_size uint = 0
+	var all_histograms_capacity uint = expected_num_clusters
+	var all_histograms []histogramDistance = make([]histogramDistance, all_histograms_capacity)
+	var cluster_size_size uint = 0
+	var cluster_size_capacity uint = expected_num_clusters
+	var cluster_size []uint32 = make([]uint32, cluster_size_capacity)
+	var num_clusters uint = 0
+	var histograms []histogramDistance = make([]histogramDistance, brotli_min_size_t(num_blocks, histogramsPerBatch))
+	var max_num_pairs uint = histogramsPerBatch * histogramsPerBatch / 2
+	var pairs_capacity uint = max_num_pairs + 1
+	var pairs []histogramPair = make([]histogramPair, pairs_capacity)
+	var pos uint = 0
+	var clusters []uint32
+	var num_final_clusters uint
+	var new_index []uint32
+	var i uint
+	var sizes = [histogramsPerBatch]uint32{0}
+	var new_clusters = [histogramsPerBatch]uint32{0}
+	var symbols = [histogramsPerBatch]uint32{0}
+	var remap = [histogramsPerBatch]uint32{0}
+
+	for i := 0; i < int(num_blocks); i++ {
+		block_lengths[i] = 0
+	}
+	{
+		var block_idx uint = 0
+		for i = 0; i < length; i++ {
+			assert(block_idx < num_blocks)
+			block_lengths[block_idx]++
+			if i+1 == length || block_ids[i] != block_ids[i+1] {
+				block_idx++
+			}
+		}
+
+		assert(block_idx == num_blocks)
+	}
+
+	for i = 0; i < num_blocks; i += histogramsPerBatch {
+		var num_to_combine uint = brotli_min_size_t(num_blocks-i, histogramsPerBatch)
+		var num_new_clusters uint
+		var j uint
+		for j = 0; j < num_to_combine; j++ {
+			var k uint
+			histogramClearDistance(&histograms[j])
+			for k = 0; uint32(k) < block_lengths[i+j]; k++ {
+				histogramAddDistance(&histograms[j], uint(data[pos]))
+				pos++
+			}
+
+			histograms[j].bit_cost_ = populationCostDistance(&histograms[j])
+			new_clusters[j] = uint32(j)
+			symbols[j] = uint32(j)
+			sizes[j] = 1
+		}
+
+		num_new_clusters = histogramCombineDistance(histograms, sizes[:], symbols[:], new_clusters[:], []histogramPair(pairs), num_to_combine, num_to_combine, histogramsPerBatch, max_num_pairs)
+		if all_histograms_capacity < (all_histograms_size + num_new_clusters) {
+			var _new_size uint
+			if all_histograms_capacity == 0 {
+				_new_size = all_histograms_size + num_new_clusters
+			} else {
+				_new_size = all_histograms_capacity
+			}
+			var new_array []histogramDistance
+			for _new_size < (all_histograms_size + num_new_clusters) {
+				_new_size *= 2
+			}
+			new_array = make([]histogramDistance, _new_size)
+			if all_histograms_capacity != 0 {
+				copy(new_array, all_histograms[:all_histograms_capacity])
+			}
+
+			all_histograms = new_array
+			all_histograms_capacity = _new_size
+		}
+
+		brotli_ensure_capacity_uint32_t(&cluster_size, &cluster_size_capacity, cluster_size_size+num_new_clusters)
+		for j = 0; j < num_new_clusters; j++ {
+			all_histograms[all_histograms_size] = histograms[new_clusters[j]]
+			all_histograms_size++
+			cluster_size[cluster_size_size] = sizes[new_clusters[j]]
+			cluster_size_size++
+			remap[new_clusters[j]] = uint32(j)
+		}
+
+		for j = 0; j < num_to_combine; j++ {
+			histogram_symbols[i+j] = uint32(num_clusters) + remap[symbols[j]]
+		}
+
+		num_clusters += num_new_clusters
+		assert(num_clusters == cluster_size_size)
+		assert(num_clusters == all_histograms_size)
+	}
+
+	histograms = nil
+
+	max_num_pairs = brotli_min_size_t(64*num_clusters, (num_clusters/2)*num_clusters)
+	if pairs_capacity < max_num_pairs+1 {
+		pairs = nil
+		pairs = make([]histogramPair, (max_num_pairs + 1))
+	}
+
+	clusters = make([]uint32, num_clusters)
+	for i = 0; i < num_clusters; i++ {
+		clusters[i] = uint32(i)
+	}
+
+	num_final_clusters = histogramCombineDistance(all_histograms, cluster_size, histogram_symbols, clusters, pairs, num_clusters, num_blocks, maxNumberOfBlockTypes, max_num_pairs)
+	pairs = nil
+	cluster_size = nil
+
+	new_index = make([]uint32, num_clusters)
+	for i = 0; i < num_clusters; i++ {
+		new_index[i] = clusterBlocksDistance_kInvalidIndex
+	}
+	pos = 0
+	{
+		var next_index uint32 = 0
+		for i = 0; i < num_blocks; i++ {
+			var histo histogramDistance
+			var j uint
+			var best_out uint32
+			var best_bits float64
+			histogramClearDistance(&histo)
+			for j = 0; uint32(j) < block_lengths[i]; j++ {
+				histogramAddDistance(&histo, uint(data[pos]))
+				pos++
+			}
+
+			if i == 0 {
+				best_out = histogram_symbols[0]
+			} else {
+				best_out = histogram_symbols[i-1]
+			}
+			best_bits = histogramBitCostDistanceDistance(&histo, &all_histograms[best_out])
+			for j = 0; j < num_final_clusters; j++ {
+				var cur_bits float64 = histogramBitCostDistanceDistance(&histo, &all_histograms[clusters[j]])
+				if cur_bits < best_bits {
+					best_bits = cur_bits
+					best_out = clusters[j]
+				}
+			}
+
+			histogram_symbols[i] = best_out
+			if new_index[best_out] == clusterBlocksDistance_kInvalidIndex {
+				new_index[best_out] = next_index
+				next_index++
+			}
+		}
+	}
+
+	clusters = nil
+	all_histograms = nil
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, num_blocks)
+	{
+		var cur_length uint32 = 0
+		var block_idx uint = 0
+		var max_type byte = 0
+		for i = 0; i < num_blocks; i++ {
+			cur_length += block_lengths[i]
+			if i+1 == num_blocks || histogram_symbols[i] != histogram_symbols[i+1] {
+				var id byte = byte(new_index[histogram_symbols[i]])
+				split.types[block_idx] = id
+				split.lengths[block_idx] = cur_length
+				max_type = brotli_max_uint8_t(max_type, id)
+				cur_length = 0
+				block_idx++
+			}
+		}
+
+		split.num_blocks = block_idx
+		split.num_types = uint(max_type) + 1
+	}
+
+	new_index = nil
+	block_lengths = nil
+	histogram_symbols = nil
+}
+
+func splitByteVectorDistance(data []uint16, length uint, literals_per_histogram uint, max_histograms uint, sampling_stride_length uint, block_switch_cost float64, params *encoderParams, split *blockSplit) {
+	var data_size uint = histogramDataSizeDistance()
+	var num_histograms uint = length/literals_per_histogram + 1
+	var histograms []histogramDistance
+	if num_histograms > max_histograms {
+		num_histograms = max_histograms
+	}
+
+	if length == 0 {
+		split.num_types = 1
+		return
+	} else if length < kMinLengthForBlockSplitting {
+		brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, split.num_blocks+1)
+		brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, split.num_blocks+1)
+		split.num_types = 1
+		split.types[split.num_blocks] = 0
+		split.lengths[split.num_blocks] = uint32(length)
+		split.num_blocks++
+		return
+	}
+
+	histograms = make([]histogramDistance, num_histograms)
+
+	/* Find good entropy codes. */
+	initialEntropyCodesDistance(data, length, sampling_stride_length, num_histograms, histograms)
+
+	refineEntropyCodesDistance(data, length, sampling_stride_length, num_histograms, histograms)
+	{
+		var block_ids []byte = make([]byte, length)
+		var num_blocks uint = 0
+		var bitmaplen uint = (num_histograms + 7) >> 3
+		var insert_cost []float64 = make([]float64, (data_size * num_histograms))
+		var cost []float64 = make([]float64, num_histograms)
+		var switch_signal []byte = make([]byte, (length * bitmaplen))
+		var new_id []uint16 = make([]uint16, num_histograms)
+		var iters uint
+		if params.quality < hqZopflificationQuality {
+			iters = 3
+		} else {
+			iters = 10
+		}
+		/* Find a good path through literals with the good entropy codes. */
+
+		var i uint
+		for i = 0; i < iters; i++ {
+			num_blocks = findBlocksDistance(data, length, block_switch_cost, num_histograms, histograms, insert_cost, cost, switch_signal, block_ids)
+			num_histograms = remapBlockIdsDistance(block_ids, length, new_id, num_histograms)
+			buildBlockHistogramsDistance(data, length, block_ids, num_histograms, histograms)
+		}
+
+		insert_cost = nil
+		cost = nil
+		switch_signal = nil
+		new_id = nil
+		histograms = nil
+		clusterBlocksDistance(data, length, num_blocks, block_ids, split)
+		block_ids = nil
+	}
+}

vendor/github.com/andybalholm/brotli/block_splitter_literal.go

@@ -0,0 +1,433 @@
+package brotli
+
+import "math"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func initialEntropyCodesLiteral(data []byte, length uint, stride uint, num_histograms uint, histograms []histogramLiteral) {
+	var seed uint32 = 7
+	var block_length uint = length / num_histograms
+	var i uint
+	clearHistogramsLiteral(histograms, num_histograms)
+	for i = 0; i < num_histograms; i++ {
+		var pos uint = length * i / num_histograms
+		if i != 0 {
+			pos += uint(myRand(&seed) % uint32(block_length))
+		}
+
+		if pos+stride >= length {
+			pos = length - stride - 1
+		}
+
+		histogramAddVectorLiteral(&histograms[i], data[pos:], stride)
+	}
+}
+
+func randomSampleLiteral(seed *uint32, data []byte, length uint, stride uint, sample *histogramLiteral) {
+	var pos uint = 0
+	if stride >= length {
+		stride = length
+	} else {
+		pos = uint(myRand(seed) % uint32(length-stride+1))
+	}
+
+	histogramAddVectorLiteral(sample, data[pos:], stride)
+}
+
+func refineEntropyCodesLiteral(data []byte, length uint, stride uint, num_histograms uint, histograms []histogramLiteral) {
+	var iters uint = kIterMulForRefining*length/stride + kMinItersForRefining
+	var seed uint32 = 7
+	var iter uint
+	iters = ((iters + num_histograms - 1) / num_histograms) * num_histograms
+	for iter = 0; iter < iters; iter++ {
+		var sample histogramLiteral
+		histogramClearLiteral(&sample)
+		randomSampleLiteral(&seed, data, length, stride, &sample)
+		histogramAddHistogramLiteral(&histograms[iter%num_histograms], &sample)
+	}
+}
+
+/* Assigns a block id from the range [0, num_histograms) to each data element
+   in data[0..length) and fills in block_id[0..length) with the assigned values.
+   Returns the number of blocks, i.e. one plus the number of block switches. */
+func findBlocksLiteral(data []byte, length uint, block_switch_bitcost float64, num_histograms uint, histograms []histogramLiteral, insert_cost []float64, cost []float64, switch_signal []byte, block_id []byte) uint {
+	var data_size uint = histogramDataSizeLiteral()
+	var bitmaplen uint = (num_histograms + 7) >> 3
+	var num_blocks uint = 1
+	var i uint
+	var j uint
+	assert(num_histograms <= 256)
+	if num_histograms <= 1 {
+		for i = 0; i < length; i++ {
+			block_id[i] = 0
+		}
+
+		return 1
+	}
+
+	for i := 0; i < int(data_size*num_histograms); i++ {
+		insert_cost[i] = 0
+	}
+	for i = 0; i < num_histograms; i++ {
+		insert_cost[i] = fastLog2(uint(uint32(histograms[i].total_count_)))
+	}
+
+	for i = data_size; i != 0; {
+		i--
+		for j = 0; j < num_histograms; j++ {
+			insert_cost[i*num_histograms+j] = insert_cost[j] - bitCost(uint(histograms[j].data_[i]))
+		}
+	}
+
+	for i := 0; i < int(num_histograms); i++ {
+		cost[i] = 0
+	}
+	for i := 0; i < int(length*bitmaplen); i++ {
+		switch_signal[i] = 0
+	}
+
+	/* After each iteration of this loop, cost[k] will contain the difference
+	   between the minimum cost of arriving at the current byte position using
+	   entropy code k, and the minimum cost of arriving at the current byte
+	   position. This difference is capped at the block switch cost, and if it
+	   reaches block switch cost, it means that when we trace back from the last
+	   position, we need to switch here. */
+	for i = 0; i < length; i++ {
+		var byte_ix uint = i
+		var ix uint = byte_ix * bitmaplen
+		var insert_cost_ix uint = uint(data[byte_ix]) * num_histograms
+		var min_cost float64 = 1e99
+		var block_switch_cost float64 = block_switch_bitcost
+		var k uint
+		for k = 0; k < num_histograms; k++ {
+			/* We are coding the symbol in data[byte_ix] with entropy code k. */
+			cost[k] += insert_cost[insert_cost_ix+k]
+
+			if cost[k] < min_cost {
+				min_cost = cost[k]
+				block_id[byte_ix] = byte(k)
+			}
+		}
+
+		/* More blocks for the beginning. */
+		if byte_ix < 2000 {
+			block_switch_cost *= 0.77 + 0.07*float64(byte_ix)/2000
+		}
+
+		for k = 0; k < num_histograms; k++ {
+			cost[k] -= min_cost
+			if cost[k] >= block_switch_cost {
+				var mask byte = byte(1 << (k & 7))
+				cost[k] = block_switch_cost
+				assert(k>>3 < bitmaplen)
+				switch_signal[ix+(k>>3)] |= mask
+				/* Trace back from the last position and switch at the marked places. */
+			}
+		}
+	}
+	{
+		var byte_ix uint = length - 1
+		var ix uint = byte_ix * bitmaplen
+		var cur_id byte = block_id[byte_ix]
+		for byte_ix > 0 {
+			var mask byte = byte(1 << (cur_id & 7))
+			assert(uint(cur_id)>>3 < bitmaplen)
+			byte_ix--
+			ix -= bitmaplen
+			if switch_signal[ix+uint(cur_id>>3)]&mask != 0 {
+				if cur_id != block_id[byte_ix] {
+					cur_id = block_id[byte_ix]
+					num_blocks++
+				}
+			}
+
+			block_id[byte_ix] = cur_id
+		}
+	}
+
+	return num_blocks
+}
+
+var remapBlockIdsLiteral_kInvalidId uint16 = 256
+
+func remapBlockIdsLiteral(block_ids []byte, length uint, new_id []uint16, num_histograms uint) uint {
+	var next_id uint16 = 0
+	var i uint
+	for i = 0; i < num_histograms; i++ {
+		new_id[i] = remapBlockIdsLiteral_kInvalidId
+	}
+
+	for i = 0; i < length; i++ {
+		assert(uint(block_ids[i]) < num_histograms)
+		if new_id[block_ids[i]] == remapBlockIdsLiteral_kInvalidId {
+			new_id[block_ids[i]] = next_id
+			next_id++
+		}
+	}
+
+	for i = 0; i < length; i++ {
+		block_ids[i] = byte(new_id[block_ids[i]])
+		assert(uint(block_ids[i]) < num_histograms)
+	}
+
+	assert(uint(next_id) <= num_histograms)
+	return uint(next_id)
+}
+
+func buildBlockHistogramsLiteral(data []byte, length uint, block_ids []byte, num_histograms uint, histograms []histogramLiteral) {
+	var i uint
+	clearHistogramsLiteral(histograms, num_histograms)
+	for i = 0; i < length; i++ {
+		histogramAddLiteral(&histograms[block_ids[i]], uint(data[i]))
+	}
+}
+
+var clusterBlocksLiteral_kInvalidIndex uint32 = math.MaxUint32
+
+func clusterBlocksLiteral(data []byte, length uint, num_blocks uint, block_ids []byte, split *blockSplit) {
+	var histogram_symbols []uint32 = make([]uint32, num_blocks)
+	var block_lengths []uint32 = make([]uint32, num_blocks)
+	var expected_num_clusters uint = clustersPerBatch * (num_blocks + histogramsPerBatch - 1) / histogramsPerBatch
+	var all_histograms_size uint = 0
+	var all_histograms_capacity uint = expected_num_clusters
+	var all_histograms []histogramLiteral = make([]histogramLiteral, all_histograms_capacity)
+	var cluster_size_size uint = 0
+	var cluster_size_capacity uint = expected_num_clusters
+	var cluster_size []uint32 = make([]uint32, cluster_size_capacity)
+	var num_clusters uint = 0
+	var histograms []histogramLiteral = make([]histogramLiteral, brotli_min_size_t(num_blocks, histogramsPerBatch))
+	var max_num_pairs uint = histogramsPerBatch * histogramsPerBatch / 2
+	var pairs_capacity uint = max_num_pairs + 1
+	var pairs []histogramPair = make([]histogramPair, pairs_capacity)
+	var pos uint = 0
+	var clusters []uint32
+	var num_final_clusters uint
+	var new_index []uint32
+	var i uint
+	var sizes = [histogramsPerBatch]uint32{0}
+	var new_clusters = [histogramsPerBatch]uint32{0}
+	var symbols = [histogramsPerBatch]uint32{0}
+	var remap = [histogramsPerBatch]uint32{0}
+
+	for i := 0; i < int(num_blocks); i++ {
+		block_lengths[i] = 0
+	}
+	{
+		var block_idx uint = 0
+		for i = 0; i < length; i++ {
+			assert(block_idx < num_blocks)
+			block_lengths[block_idx]++
+			if i+1 == length || block_ids[i] != block_ids[i+1] {
+				block_idx++
+			}
+		}
+
+		assert(block_idx == num_blocks)
+	}
+
+	for i = 0; i < num_blocks; i += histogramsPerBatch {
+		var num_to_combine uint = brotli_min_size_t(num_blocks-i, histogramsPerBatch)
+		var num_new_clusters uint
+		var j uint
+		for j = 0; j < num_to_combine; j++ {
+			var k uint
+			histogramClearLiteral(&histograms[j])
+			for k = 0; uint32(k) < block_lengths[i+j]; k++ {
+				histogramAddLiteral(&histograms[j], uint(data[pos]))
+				pos++
+			}
+
+			histograms[j].bit_cost_ = populationCostLiteral(&histograms[j])
+			new_clusters[j] = uint32(j)
+			symbols[j] = uint32(j)
+			sizes[j] = 1
+		}
+
+		num_new_clusters = histogramCombineLiteral(histograms, sizes[:], symbols[:], new_clusters[:], []histogramPair(pairs), num_to_combine, num_to_combine, histogramsPerBatch, max_num_pairs)
+		if all_histograms_capacity < (all_histograms_size + num_new_clusters) {
+			var _new_size uint
+			if all_histograms_capacity == 0 {
+				_new_size = all_histograms_size + num_new_clusters
+			} else {
+				_new_size = all_histograms_capacity
+			}
+			var new_array []histogramLiteral
+			for _new_size < (all_histograms_size + num_new_clusters) {
+				_new_size *= 2
+			}
+			new_array = make([]histogramLiteral, _new_size)
+			if all_histograms_capacity != 0 {
+				copy(new_array, all_histograms[:all_histograms_capacity])
+			}
+
+			all_histograms = new_array
+			all_histograms_capacity = _new_size
+		}
+
+		brotli_ensure_capacity_uint32_t(&cluster_size, &cluster_size_capacity, cluster_size_size+num_new_clusters)
+		for j = 0; j < num_new_clusters; j++ {
+			all_histograms[all_histograms_size] = histograms[new_clusters[j]]
+			all_histograms_size++
+			cluster_size[cluster_size_size] = sizes[new_clusters[j]]
+			cluster_size_size++
+			remap[new_clusters[j]] = uint32(j)
+		}
+
+		for j = 0; j < num_to_combine; j++ {
+			histogram_symbols[i+j] = uint32(num_clusters) + remap[symbols[j]]
+		}
+
+		num_clusters += num_new_clusters
+		assert(num_clusters == cluster_size_size)
+		assert(num_clusters == all_histograms_size)
+	}
+
+	histograms = nil
+
+	max_num_pairs = brotli_min_size_t(64*num_clusters, (num_clusters/2)*num_clusters)
+	if pairs_capacity < max_num_pairs+1 {
+		pairs = nil
+		pairs = make([]histogramPair, (max_num_pairs + 1))
+	}
+
+	clusters = make([]uint32, num_clusters)
+	for i = 0; i < num_clusters; i++ {
+		clusters[i] = uint32(i)
+	}
+
+	num_final_clusters = histogramCombineLiteral(all_histograms, cluster_size, histogram_symbols, clusters, pairs, num_clusters, num_blocks, maxNumberOfBlockTypes, max_num_pairs)
+	pairs = nil
+	cluster_size = nil
+
+	new_index = make([]uint32, num_clusters)
+	for i = 0; i < num_clusters; i++ {
+		new_index[i] = clusterBlocksLiteral_kInvalidIndex
+	}
+	pos = 0
+	{
+		var next_index uint32 = 0
+		for i = 0; i < num_blocks; i++ {
+			var histo histogramLiteral
+			var j uint
+			var best_out uint32
+			var best_bits float64
+			histogramClearLiteral(&histo)
+			for j = 0; uint32(j) < block_lengths[i]; j++ {
+				histogramAddLiteral(&histo, uint(data[pos]))
+				pos++
+			}
+
+			if i == 0 {
+				best_out = histogram_symbols[0]
+			} else {
+				best_out = histogram_symbols[i-1]
+			}
+			best_bits = histogramBitCostDistanceLiteral(&histo, &all_histograms[best_out])
+			for j = 0; j < num_final_clusters; j++ {
+				var cur_bits float64 = histogramBitCostDistanceLiteral(&histo, &all_histograms[clusters[j]])
+				if cur_bits < best_bits {
+					best_bits = cur_bits
+					best_out = clusters[j]
+				}
+			}
+
+			histogram_symbols[i] = best_out
+			if new_index[best_out] == clusterBlocksLiteral_kInvalidIndex {
+				new_index[best_out] = next_index
+				next_index++
+			}
+		}
+	}
+
+	clusters = nil
+	all_histograms = nil
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, num_blocks)
+	{
+		var cur_length uint32 = 0
+		var block_idx uint = 0
+		var max_type byte = 0
+		for i = 0; i < num_blocks; i++ {
+			cur_length += block_lengths[i]
+			if i+1 == num_blocks || histogram_symbols[i] != histogram_symbols[i+1] {
+				var id byte = byte(new_index[histogram_symbols[i]])
+				split.types[block_idx] = id
+				split.lengths[block_idx] = cur_length
+				max_type = brotli_max_uint8_t(max_type, id)
+				cur_length = 0
+				block_idx++
+			}
+		}
+
+		split.num_blocks = block_idx
+		split.num_types = uint(max_type) + 1
+	}
+
+	new_index = nil
+	block_lengths = nil
+	histogram_symbols = nil
+}
+
+func splitByteVectorLiteral(data []byte, length uint, literals_per_histogram uint, max_histograms uint, sampling_stride_length uint, block_switch_cost float64, params *encoderParams, split *blockSplit) {
+	var data_size uint = histogramDataSizeLiteral()
+	var num_histograms uint = length/literals_per_histogram + 1
+	var histograms []histogramLiteral
+	if num_histograms > max_histograms {
+		num_histograms = max_histograms
+	}
+
+	if length == 0 {
+		split.num_types = 1
+		return
+	} else if length < kMinLengthForBlockSplitting {
+		brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, split.num_blocks+1)
+		brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, split.num_blocks+1)
+		split.num_types = 1
+		split.types[split.num_blocks] = 0
+		split.lengths[split.num_blocks] = uint32(length)
+		split.num_blocks++
+		return
+	}
+
+	histograms = make([]histogramLiteral, num_histograms)
+
+	/* Find good entropy codes. */
+	initialEntropyCodesLiteral(data, length, sampling_stride_length, num_histograms, histograms)
+
+	refineEntropyCodesLiteral(data, length, sampling_stride_length, num_histograms, histograms)
+	{
+		var block_ids []byte = make([]byte, length)
+		var num_blocks uint = 0
+		var bitmaplen uint = (num_histograms + 7) >> 3
+		var insert_cost []float64 = make([]float64, (data_size * num_histograms))
+		var cost []float64 = make([]float64, num_histograms)
+		var switch_signal []byte = make([]byte, (length * bitmaplen))
+		var new_id []uint16 = make([]uint16, num_histograms)
+		var iters uint
+		if params.quality < hqZopflificationQuality {
+			iters = 3
+		} else {
+			iters = 10
+		}
+		/* Find a good path through literals with the good entropy codes. */
+
+		var i uint
+		for i = 0; i < iters; i++ {
+			num_blocks = findBlocksLiteral(data, length, block_switch_cost, num_histograms, histograms, insert_cost, cost, switch_signal, block_ids)
+			num_histograms = remapBlockIdsLiteral(block_ids, length, new_id, num_histograms)
+			buildBlockHistogramsLiteral(data, length, block_ids, num_histograms, histograms)
+		}
+
+		insert_cost = nil
+		cost = nil
+		switch_signal = nil
+		new_id = nil
+		histograms = nil
+		clusterBlocksLiteral(data, length, num_blocks, block_ids, split)
+		block_ids = nil
+	}
+}

vendor/github.com/andybalholm/brotli/cluster.go

@@ -0,0 +1,30 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Functions for clustering similar histograms together. */
+
+type histogramPair struct {
+	idx1       uint32
+	idx2       uint32
+	cost_combo float64
+	cost_diff  float64
+}
+
+func histogramPairIsLess(p1 *histogramPair, p2 *histogramPair) bool {
+	if p1.cost_diff != p2.cost_diff {
+		return p1.cost_diff > p2.cost_diff
+	}
+
+	return (p1.idx2 - p1.idx1) > (p2.idx2 - p2.idx1)
+}
+
+/* Returns entropy reduction of the context map when we combine two clusters. */
+func clusterCostDiff(size_a uint, size_b uint) float64 {
+	var size_c uint = size_a + size_b
+	return float64(size_a)*fastLog2(size_a) + float64(size_b)*fastLog2(size_b) - float64(size_c)*fastLog2(size_c)
+}

vendor/github.com/andybalholm/brotli/cluster_command.go

@@ -0,0 +1,164 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Computes the bit cost reduction by combining out[idx1] and out[idx2] and if
+   it is below a threshold, stores the pair (idx1, idx2) in the *pairs queue. */
+func compareAndPushToQueueCommand(out []histogramCommand, cluster_size []uint32, idx1 uint32, idx2 uint32, max_num_pairs uint, pairs []histogramPair, num_pairs *uint) {
+	var is_good_pair bool = false
+	var p histogramPair
+	p.idx2 = 0
+	p.idx1 = p.idx2
+	p.cost_combo = 0
+	p.cost_diff = p.cost_combo
+	if idx1 == idx2 {
+		return
+	}
+
+	if idx2 < idx1 {
+		var t uint32 = idx2
+		idx2 = idx1
+		idx1 = t
+	}
+
+	p.idx1 = idx1
+	p.idx2 = idx2
+	p.cost_diff = 0.5 * clusterCostDiff(uint(cluster_size[idx1]), uint(cluster_size[idx2]))
+	p.cost_diff -= out[idx1].bit_cost_
+	p.cost_diff -= out[idx2].bit_cost_
+
+	if out[idx1].total_count_ == 0 {
+		p.cost_combo = out[idx2].bit_cost_
+		is_good_pair = true
+	} else if out[idx2].total_count_ == 0 {
+		p.cost_combo = out[idx1].bit_cost_
+		is_good_pair = true
+	} else {
+		var threshold float64
+		if *num_pairs == 0 {
+			threshold = 1e99
+		} else {
+			threshold = brotli_max_double(0.0, pairs[0].cost_diff)
+		}
+		var combo histogramCommand = out[idx1]
+		var cost_combo float64
+		histogramAddHistogramCommand(&combo, &out[idx2])
+		cost_combo = populationCostCommand(&combo)
+		if cost_combo < threshold-p.cost_diff {
+			p.cost_combo = cost_combo
+			is_good_pair = true
+		}
+	}
+
+	if is_good_pair {
+		p.cost_diff += p.cost_combo
+		if *num_pairs > 0 && histogramPairIsLess(&pairs[0], &p) {
+			/* Replace the top of the queue if needed. */
+			if *num_pairs < max_num_pairs {
+				pairs[*num_pairs] = pairs[0]
+				(*num_pairs)++
+			}
+
+			pairs[0] = p
+		} else if *num_pairs < max_num_pairs {
+			pairs[*num_pairs] = p
+			(*num_pairs)++
+		}
+	}
+}
+
+func histogramCombineCommand(out []histogramCommand, cluster_size []uint32, symbols []uint32, clusters []uint32, pairs []histogramPair, num_clusters uint, symbols_size uint, max_clusters uint, max_num_pairs uint) uint {
+	var cost_diff_threshold float64 = 0.0
+	var min_cluster_size uint = 1
+	var num_pairs uint = 0
+	{
+		/* We maintain a vector of histogram pairs, with the property that the pair
+		   with the maximum bit cost reduction is the first. */
+		var idx1 uint
+		for idx1 = 0; idx1 < num_clusters; idx1++ {
+			var idx2 uint
+			for idx2 = idx1 + 1; idx2 < num_clusters; idx2++ {
+				compareAndPushToQueueCommand(out, cluster_size, clusters[idx1], clusters[idx2], max_num_pairs, pairs[0:], &num_pairs)
+			}
+		}
+	}
+
+	for num_clusters > min_cluster_size {
+		var best_idx1 uint32
+		var best_idx2 uint32
+		var i uint
+		if pairs[0].cost_diff >= cost_diff_threshold {
+			cost_diff_threshold = 1e99
+			min_cluster_size = max_clusters
+			continue
+		}
+
+		/* Take the best pair from the top of heap. */
+		best_idx1 = pairs[0].idx1
+
+		best_idx2 = pairs[0].idx2
+		histogramAddHistogramCommand(&out[best_idx1], &out[best_idx2])
+		out[best_idx1].bit_cost_ = pairs[0].cost_combo
+		cluster_size[best_idx1] += cluster_size[best_idx2]
+		for i = 0; i < symbols_size; i++ {
+			if symbols[i] == best_idx2 {
+				symbols[i] = best_idx1
+			}
+		}
+
+		for i = 0; i < num_clusters; i++ {
+			if clusters[i] == best_idx2 {
+				copy(clusters[i:], clusters[i+1:][:num_clusters-i-1])
+				break
+			}
+		}
+
+		num_clusters--
+		{
+			/* Remove pairs intersecting the just combined best pair. */
+			var copy_to_idx uint = 0
+			for i = 0; i < num_pairs; i++ {
+				var p *histogramPair = &pairs[i]
+				if p.idx1 == best_idx1 || p.idx2 == best_idx1 || p.idx1 == best_idx2 || p.idx2 == best_idx2 {
+					/* Remove invalid pair from the queue. */
+					continue
+				}
+
+				if histogramPairIsLess(&pairs[0], p) {
+					/* Replace the top of the queue if needed. */
+					var front histogramPair = pairs[0]
+					pairs[0] = *p
+					pairs[copy_to_idx] = front
+				} else {
+					pairs[copy_to_idx] = *p
+				}
+
+				copy_to_idx++
+			}
+
+			num_pairs = copy_to_idx
+		}
+
+		/* Push new pairs formed with the combined histogram to the heap. */
+		for i = 0; i < num_clusters; i++ {
+			compareAndPushToQueueCommand(out, cluster_size, best_idx1, clusters[i], max_num_pairs, pairs[0:], &num_pairs)
+		}
+	}
+
+	return num_clusters
+}
+
+/* What is the bit cost of moving histogram from cur_symbol to candidate. */
+func histogramBitCostDistanceCommand(histogram *histogramCommand, candidate *histogramCommand) float64 {
+	if histogram.total_count_ == 0 {
+		return 0.0
+	} else {
+		var tmp histogramCommand = *histogram
+		histogramAddHistogramCommand(&tmp, candidate)
+		return populationCostCommand(&tmp) - candidate.bit_cost_
+	}
+}

vendor/github.com/andybalholm/brotli/cluster_distance.go

@@ -0,0 +1,326 @@
+package brotli
+
+import "math"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Computes the bit cost reduction by combining out[idx1] and out[idx2] and if
+   it is below a threshold, stores the pair (idx1, idx2) in the *pairs queue. */
+func compareAndPushToQueueDistance(out []histogramDistance, cluster_size []uint32, idx1 uint32, idx2 uint32, max_num_pairs uint, pairs []histogramPair, num_pairs *uint) {
+	var is_good_pair bool = false
+	var p histogramPair
+	p.idx2 = 0
+	p.idx1 = p.idx2
+	p.cost_combo = 0
+	p.cost_diff = p.cost_combo
+	if idx1 == idx2 {
+		return
+	}
+
+	if idx2 < idx1 {
+		var t uint32 = idx2
+		idx2 = idx1
+		idx1 = t
+	}
+
+	p.idx1 = idx1
+	p.idx2 = idx2
+	p.cost_diff = 0.5 * clusterCostDiff(uint(cluster_size[idx1]), uint(cluster_size[idx2]))
+	p.cost_diff -= out[idx1].bit_cost_
+	p.cost_diff -= out[idx2].bit_cost_
+
+	if out[idx1].total_count_ == 0 {
+		p.cost_combo = out[idx2].bit_cost_
+		is_good_pair = true
+	} else if out[idx2].total_count_ == 0 {
+		p.cost_combo = out[idx1].bit_cost_
+		is_good_pair = true
+	} else {
+		var threshold float64
+		if *num_pairs == 0 {
+			threshold = 1e99
+		} else {
+			threshold = brotli_max_double(0.0, pairs[0].cost_diff)
+		}
+		var combo histogramDistance = out[idx1]
+		var cost_combo float64
+		histogramAddHistogramDistance(&combo, &out[idx2])
+		cost_combo = populationCostDistance(&combo)
+		if cost_combo < threshold-p.cost_diff {
+			p.cost_combo = cost_combo
+			is_good_pair = true
+		}
+	}
+
+	if is_good_pair {
+		p.cost_diff += p.cost_combo
+		if *num_pairs > 0 && histogramPairIsLess(&pairs[0], &p) {
+			/* Replace the top of the queue if needed. */
+			if *num_pairs < max_num_pairs {
+				pairs[*num_pairs] = pairs[0]
+				(*num_pairs)++
+			}
+
+			pairs[0] = p
+		} else if *num_pairs < max_num_pairs {
+			pairs[*num_pairs] = p
+			(*num_pairs)++
+		}
+	}
+}
+
+func histogramCombineDistance(out []histogramDistance, cluster_size []uint32, symbols []uint32, clusters []uint32, pairs []histogramPair, num_clusters uint, symbols_size uint, max_clusters uint, max_num_pairs uint) uint {
+	var cost_diff_threshold float64 = 0.0
+	var min_cluster_size uint = 1
+	var num_pairs uint = 0
+	{
+		/* We maintain a vector of histogram pairs, with the property that the pair
+		   with the maximum bit cost reduction is the first. */
+		var idx1 uint
+		for idx1 = 0; idx1 < num_clusters; idx1++ {
+			var idx2 uint
+			for idx2 = idx1 + 1; idx2 < num_clusters; idx2++ {
+				compareAndPushToQueueDistance(out, cluster_size, clusters[idx1], clusters[idx2], max_num_pairs, pairs[0:], &num_pairs)
+			}
+		}
+	}
+
+	for num_clusters > min_cluster_size {
+		var best_idx1 uint32
+		var best_idx2 uint32
+		var i uint
+		if pairs[0].cost_diff >= cost_diff_threshold {
+			cost_diff_threshold = 1e99
+			min_cluster_size = max_clusters
+			continue
+		}
+
+		/* Take the best pair from the top of heap. */
+		best_idx1 = pairs[0].idx1
+
+		best_idx2 = pairs[0].idx2
+		histogramAddHistogramDistance(&out[best_idx1], &out[best_idx2])
+		out[best_idx1].bit_cost_ = pairs[0].cost_combo
+		cluster_size[best_idx1] += cluster_size[best_idx2]
+		for i = 0; i < symbols_size; i++ {
+			if symbols[i] == best_idx2 {
+				symbols[i] = best_idx1
+			}
+		}
+
+		for i = 0; i < num_clusters; i++ {
+			if clusters[i] == best_idx2 {
+				copy(clusters[i:], clusters[i+1:][:num_clusters-i-1])
+				break
+			}
+		}
+
+		num_clusters--
+		{
+			/* Remove pairs intersecting the just combined best pair. */
+			var copy_to_idx uint = 0
+			for i = 0; i < num_pairs; i++ {
+				var p *histogramPair = &pairs[i]
+				if p.idx1 == best_idx1 || p.idx2 == best_idx1 || p.idx1 == best_idx2 || p.idx2 == best_idx2 {
+					/* Remove invalid pair from the queue. */
+					continue
+				}
+
+				if histogramPairIsLess(&pairs[0], p) {
+					/* Replace the top of the queue if needed. */
+					var front histogramPair = pairs[0]
+					pairs[0] = *p
+					pairs[copy_to_idx] = front
+				} else {
+					pairs[copy_to_idx] = *p
+				}
+
+				copy_to_idx++
+			}
+
+			num_pairs = copy_to_idx
+		}
+
+		/* Push new pairs formed with the combined histogram to the heap. */
+		for i = 0; i < num_clusters; i++ {
+			compareAndPushToQueueDistance(out, cluster_size, best_idx1, clusters[i], max_num_pairs, pairs[0:], &num_pairs)
+		}
+	}
+
+	return num_clusters
+}
+
+/* What is the bit cost of moving histogram from cur_symbol to candidate. */
+func histogramBitCostDistanceDistance(histogram *histogramDistance, candidate *histogramDistance) float64 {
+	if histogram.total_count_ == 0 {
+		return 0.0
+	} else {
+		var tmp histogramDistance = *histogram
+		histogramAddHistogramDistance(&tmp, candidate)
+		return populationCostDistance(&tmp) - candidate.bit_cost_
+	}
+}
+
+/* Find the best 'out' histogram for each of the 'in' histograms.
+   When called, clusters[0..num_clusters) contains the unique values from
+   symbols[0..in_size), but this property is not preserved in this function.
+   Note: we assume that out[]->bit_cost_ is already up-to-date. */
+func histogramRemapDistance(in []histogramDistance, in_size uint, clusters []uint32, num_clusters uint, out []histogramDistance, symbols []uint32) {
+	var i uint
+	for i = 0; i < in_size; i++ {
+		var best_out uint32
+		if i == 0 {
+			best_out = symbols[0]
+		} else {
+			best_out = symbols[i-1]
+		}
+		var best_bits float64 = histogramBitCostDistanceDistance(&in[i], &out[best_out])
+		var j uint
+		for j = 0; j < num_clusters; j++ {
+			var cur_bits float64 = histogramBitCostDistanceDistance(&in[i], &out[clusters[j]])
+			if cur_bits < best_bits {
+				best_bits = cur_bits
+				best_out = clusters[j]
+			}
+		}
+
+		symbols[i] = best_out
+	}
+
+	/* Recompute each out based on raw and symbols. */
+	for i = 0; i < num_clusters; i++ {
+		histogramClearDistance(&out[clusters[i]])
+	}
+
+	for i = 0; i < in_size; i++ {
+		histogramAddHistogramDistance(&out[symbols[i]], &in[i])
+	}
+}
+
+/* Reorders elements of the out[0..length) array and changes values in
+   symbols[0..length) array in the following way:
+     * when called, symbols[] contains indexes into out[], and has N unique
+       values (possibly N < length)
+     * on return, symbols'[i] = f(symbols[i]) and
+                  out'[symbols'[i]] = out[symbols[i]], for each 0 <= i < length,
+       where f is a bijection between the range of symbols[] and [0..N), and
+       the first occurrences of values in symbols'[i] come in consecutive
+       increasing order.
+   Returns N, the number of unique values in symbols[]. */
+
+var histogramReindexDistance_kInvalidIndex uint32 = math.MaxUint32
+
+func histogramReindexDistance(out []histogramDistance, symbols []uint32, length uint) uint {
+	var new_index []uint32 = make([]uint32, length)
+	var next_index uint32
+	var tmp []histogramDistance
+	var i uint
+	for i = 0; i < length; i++ {
+		new_index[i] = histogramReindexDistance_kInvalidIndex
+	}
+
+	next_index = 0
+	for i = 0; i < length; i++ {
+		if new_index[symbols[i]] == histogramReindexDistance_kInvalidIndex {
+			new_index[symbols[i]] = next_index
+			next_index++
+		}
+	}
+
+	/* TODO: by using idea of "cycle-sort" we can avoid allocation of
+	   tmp and reduce the number of copying by the factor of 2. */
+	tmp = make([]histogramDistance, next_index)
+
+	next_index = 0
+	for i = 0; i < length; i++ {
+		if new_index[symbols[i]] == next_index {
+			tmp[next_index] = out[symbols[i]]
+			next_index++
+		}
+
+		symbols[i] = new_index[symbols[i]]
+	}
+
+	new_index = nil
+	for i = 0; uint32(i) < next_index; i++ {
+		out[i] = tmp[i]
+	}
+
+	tmp = nil
+	return uint(next_index)
+}
+
+func clusterHistogramsDistance(in []histogramDistance, in_size uint, max_histograms uint, out []histogramDistance, out_size *uint, histogram_symbols []uint32) {
+	var cluster_size []uint32 = make([]uint32, in_size)
+	var clusters []uint32 = make([]uint32, in_size)
+	var num_clusters uint = 0
+	var max_input_histograms uint = 64
+	var pairs_capacity uint = max_input_histograms * max_input_histograms / 2
+	var pairs []histogramPair = make([]histogramPair, (pairs_capacity + 1))
+	var i uint
+
+	/* For the first pass of clustering, we allow all pairs. */
+	for i = 0; i < in_size; i++ {
+		cluster_size[i] = 1
+	}
+
+	for i = 0; i < in_size; i++ {
+		out[i] = in[i]
+		out[i].bit_cost_ = populationCostDistance(&in[i])
+		histogram_symbols[i] = uint32(i)
+	}
+
+	for i = 0; i < in_size; i += max_input_histograms {
+		var num_to_combine uint = brotli_min_size_t(in_size-i, max_input_histograms)
+		var num_new_clusters uint
+		var j uint
+		for j = 0; j < num_to_combine; j++ {
+			clusters[num_clusters+j] = uint32(i + j)
+		}
+
+		num_new_clusters = histogramCombineDistance(out, cluster_size, histogram_symbols[i:], clusters[num_clusters:], pairs, num_to_combine, num_to_combine, max_histograms, pairs_capacity)
+		num_clusters += num_new_clusters
+	}
+	{
+		/* For the second pass, we limit the total number of histogram pairs.
+		   After this limit is reached, we only keep searching for the best pair. */
+		var max_num_pairs uint = brotli_min_size_t(64*num_clusters, (num_clusters/2)*num_clusters)
+		if pairs_capacity < (max_num_pairs + 1) {
+			var _new_size uint
+			if pairs_capacity == 0 {
+				_new_size = max_num_pairs + 1
+			} else {
+				_new_size = pairs_capacity
+			}
+			var new_array []histogramPair
+			for _new_size < (max_num_pairs + 1) {
+				_new_size *= 2
+			}
+			new_array = make([]histogramPair, _new_size)
+			if pairs_capacity != 0 {
+				copy(new_array, pairs[:pairs_capacity])
+			}
+
+			pairs = new_array
+			pairs_capacity = _new_size
+		}
+
+		/* Collapse similar histograms. */
+		num_clusters = histogramCombineDistance(out, cluster_size, histogram_symbols, clusters, pairs, num_clusters, in_size, max_histograms, max_num_pairs)
+	}
+
+	pairs = nil
+	cluster_size = nil
+
+	/* Find the optimal map from original histograms to the final ones. */
+	histogramRemapDistance(in, in_size, clusters, num_clusters, out, histogram_symbols)
+
+	clusters = nil
+
+	/* Convert the context map to a canonical form. */
+	*out_size = histogramReindexDistance(out, histogram_symbols, in_size)
+}

vendor/github.com/andybalholm/brotli/cluster_literal.go

@@ -0,0 +1,326 @@
+package brotli
+
+import "math"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Computes the bit cost reduction by combining out[idx1] and out[idx2] and if
+   it is below a threshold, stores the pair (idx1, idx2) in the *pairs queue. */
+func compareAndPushToQueueLiteral(out []histogramLiteral, cluster_size []uint32, idx1 uint32, idx2 uint32, max_num_pairs uint, pairs []histogramPair, num_pairs *uint) {
+	var is_good_pair bool = false
+	var p histogramPair
+	p.idx2 = 0
+	p.idx1 = p.idx2
+	p.cost_combo = 0
+	p.cost_diff = p.cost_combo
+	if idx1 == idx2 {
+		return
+	}
+
+	if idx2 < idx1 {
+		var t uint32 = idx2
+		idx2 = idx1
+		idx1 = t
+	}
+
+	p.idx1 = idx1
+	p.idx2 = idx2
+	p.cost_diff = 0.5 * clusterCostDiff(uint(cluster_size[idx1]), uint(cluster_size[idx2]))
+	p.cost_diff -= out[idx1].bit_cost_
+	p.cost_diff -= out[idx2].bit_cost_
+
+	if out[idx1].total_count_ == 0 {
+		p.cost_combo = out[idx2].bit_cost_
+		is_good_pair = true
+	} else if out[idx2].total_count_ == 0 {
+		p.cost_combo = out[idx1].bit_cost_
+		is_good_pair = true
+	} else {
+		var threshold float64
+		if *num_pairs == 0 {
+			threshold = 1e99
+		} else {
+			threshold = brotli_max_double(0.0, pairs[0].cost_diff)
+		}
+		var combo histogramLiteral = out[idx1]
+		var cost_combo float64
+		histogramAddHistogramLiteral(&combo, &out[idx2])
+		cost_combo = populationCostLiteral(&combo)
+		if cost_combo < threshold-p.cost_diff {
+			p.cost_combo = cost_combo
+			is_good_pair = true
+		}
+	}
+
+	if is_good_pair {
+		p.cost_diff += p.cost_combo
+		if *num_pairs > 0 && histogramPairIsLess(&pairs[0], &p) {
+			/* Replace the top of the queue if needed. */
+			if *num_pairs < max_num_pairs {
+				pairs[*num_pairs] = pairs[0]
+				(*num_pairs)++
+			}
+
+			pairs[0] = p
+		} else if *num_pairs < max_num_pairs {
+			pairs[*num_pairs] = p
+			(*num_pairs)++
+		}
+	}
+}
+
+func histogramCombineLiteral(out []histogramLiteral, cluster_size []uint32, symbols []uint32, clusters []uint32, pairs []histogramPair, num_clusters uint, symbols_size uint, max_clusters uint, max_num_pairs uint) uint {
+	var cost_diff_threshold float64 = 0.0
+	var min_cluster_size uint = 1
+	var num_pairs uint = 0
+	{
+		/* We maintain a vector of histogram pairs, with the property that the pair
+		   with the maximum bit cost reduction is the first. */
+		var idx1 uint
+		for idx1 = 0; idx1 < num_clusters; idx1++ {
+			var idx2 uint
+			for idx2 = idx1 + 1; idx2 < num_clusters; idx2++ {
+				compareAndPushToQueueLiteral(out, cluster_size, clusters[idx1], clusters[idx2], max_num_pairs, pairs[0:], &num_pairs)
+			}
+		}
+	}
+
+	for num_clusters > min_cluster_size {
+		var best_idx1 uint32
+		var best_idx2 uint32
+		var i uint
+		if pairs[0].cost_diff >= cost_diff_threshold {
+			cost_diff_threshold = 1e99
+			min_cluster_size = max_clusters
+			continue
+		}
+
+		/* Take the best pair from the top of heap. */
+		best_idx1 = pairs[0].idx1
+
+		best_idx2 = pairs[0].idx2
+		histogramAddHistogramLiteral(&out[best_idx1], &out[best_idx2])
+		out[best_idx1].bit_cost_ = pairs[0].cost_combo
+		cluster_size[best_idx1] += cluster_size[best_idx2]
+		for i = 0; i < symbols_size; i++ {
+			if symbols[i] == best_idx2 {
+				symbols[i] = best_idx1
+			}
+		}
+
+		for i = 0; i < num_clusters; i++ {
+			if clusters[i] == best_idx2 {
+				copy(clusters[i:], clusters[i+1:][:num_clusters-i-1])
+				break
+			}
+		}
+
+		num_clusters--
+		{
+			/* Remove pairs intersecting the just combined best pair. */
+			var copy_to_idx uint = 0
+			for i = 0; i < num_pairs; i++ {
+				var p *histogramPair = &pairs[i]
+				if p.idx1 == best_idx1 || p.idx2 == best_idx1 || p.idx1 == best_idx2 || p.idx2 == best_idx2 {
+					/* Remove invalid pair from the queue. */
+					continue
+				}
+
+				if histogramPairIsLess(&pairs[0], p) {
+					/* Replace the top of the queue if needed. */
+					var front histogramPair = pairs[0]
+					pairs[0] = *p
+					pairs[copy_to_idx] = front
+				} else {
+					pairs[copy_to_idx] = *p
+				}
+
+				copy_to_idx++
+			}
+
+			num_pairs = copy_to_idx
+		}
+
+		/* Push new pairs formed with the combined histogram to the heap. */
+		for i = 0; i < num_clusters; i++ {
+			compareAndPushToQueueLiteral(out, cluster_size, best_idx1, clusters[i], max_num_pairs, pairs[0:], &num_pairs)
+		}
+	}
+
+	return num_clusters
+}
+
+/* What is the bit cost of moving histogram from cur_symbol to candidate. */
+func histogramBitCostDistanceLiteral(histogram *histogramLiteral, candidate *histogramLiteral) float64 {
+	if histogram.total_count_ == 0 {
+		return 0.0
+	} else {
+		var tmp histogramLiteral = *histogram
+		histogramAddHistogramLiteral(&tmp, candidate)
+		return populationCostLiteral(&tmp) - candidate.bit_cost_
+	}
+}
+
+/* Find the best 'out' histogram for each of the 'in' histograms.
+   When called, clusters[0..num_clusters) contains the unique values from
+   symbols[0..in_size), but this property is not preserved in this function.
+   Note: we assume that out[]->bit_cost_ is already up-to-date. */
+func histogramRemapLiteral(in []histogramLiteral, in_size uint, clusters []uint32, num_clusters uint, out []histogramLiteral, symbols []uint32) {
+	var i uint
+	for i = 0; i < in_size; i++ {
+		var best_out uint32
+		if i == 0 {
+			best_out = symbols[0]
+		} else {
+			best_out = symbols[i-1]
+		}
+		var best_bits float64 = histogramBitCostDistanceLiteral(&in[i], &out[best_out])
+		var j uint
+		for j = 0; j < num_clusters; j++ {
+			var cur_bits float64 = histogramBitCostDistanceLiteral(&in[i], &out[clusters[j]])
+			if cur_bits < best_bits {
+				best_bits = cur_bits
+				best_out = clusters[j]
+			}
+		}
+
+		symbols[i] = best_out
+	}
+
+	/* Recompute each out based on raw and symbols. */
+	for i = 0; i < num_clusters; i++ {
+		histogramClearLiteral(&out[clusters[i]])
+	}
+
+	for i = 0; i < in_size; i++ {
+		histogramAddHistogramLiteral(&out[symbols[i]], &in[i])
+	}
+}
+
+/* Reorders elements of the out[0..length) array and changes values in
+   symbols[0..length) array in the following way:
+     * when called, symbols[] contains indexes into out[], and has N unique
+       values (possibly N < length)
+     * on return, symbols'[i] = f(symbols[i]) and
+                  out'[symbols'[i]] = out[symbols[i]], for each 0 <= i < length,
+       where f is a bijection between the range of symbols[] and [0..N), and
+       the first occurrences of values in symbols'[i] come in consecutive
+       increasing order.
+   Returns N, the number of unique values in symbols[]. */
+
+var histogramReindexLiteral_kInvalidIndex uint32 = math.MaxUint32
+
+func histogramReindexLiteral(out []histogramLiteral, symbols []uint32, length uint) uint {
+	var new_index []uint32 = make([]uint32, length)
+	var next_index uint32
+	var tmp []histogramLiteral
+	var i uint
+	for i = 0; i < length; i++ {
+		new_index[i] = histogramReindexLiteral_kInvalidIndex
+	}
+
+	next_index = 0
+	for i = 0; i < length; i++ {
+		if new_index[symbols[i]] == histogramReindexLiteral_kInvalidIndex {
+			new_index[symbols[i]] = next_index
+			next_index++
+		}
+	}
+
+	/* TODO: by using idea of "cycle-sort" we can avoid allocation of
+	   tmp and reduce the number of copying by the factor of 2. */
+	tmp = make([]histogramLiteral, next_index)
+
+	next_index = 0
+	for i = 0; i < length; i++ {
+		if new_index[symbols[i]] == next_index {
+			tmp[next_index] = out[symbols[i]]
+			next_index++
+		}
+
+		symbols[i] = new_index[symbols[i]]
+	}
+
+	new_index = nil
+	for i = 0; uint32(i) < next_index; i++ {
+		out[i] = tmp[i]
+	}
+
+	tmp = nil
+	return uint(next_index)
+}
+
+func clusterHistogramsLiteral(in []histogramLiteral, in_size uint, max_histograms uint, out []histogramLiteral, out_size *uint, histogram_symbols []uint32) {
+	var cluster_size []uint32 = make([]uint32, in_size)
+	var clusters []uint32 = make([]uint32, in_size)
+	var num_clusters uint = 0
+	var max_input_histograms uint = 64
+	var pairs_capacity uint = max_input_histograms * max_input_histograms / 2
+	var pairs []histogramPair = make([]histogramPair, (pairs_capacity + 1))
+	var i uint
+
+	/* For the first pass of clustering, we allow all pairs. */
+	for i = 0; i < in_size; i++ {
+		cluster_size[i] = 1
+	}
+
+	for i = 0; i < in_size; i++ {
+		out[i] = in[i]
+		out[i].bit_cost_ = populationCostLiteral(&in[i])
+		histogram_symbols[i] = uint32(i)
+	}
+
+	for i = 0; i < in_size; i += max_input_histograms {
+		var num_to_combine uint = brotli_min_size_t(in_size-i, max_input_histograms)
+		var num_new_clusters uint
+		var j uint
+		for j = 0; j < num_to_combine; j++ {
+			clusters[num_clusters+j] = uint32(i + j)
+		}
+
+		num_new_clusters = histogramCombineLiteral(out, cluster_size, histogram_symbols[i:], clusters[num_clusters:], pairs, num_to_combine, num_to_combine, max_histograms, pairs_capacity)
+		num_clusters += num_new_clusters
+	}
+	{
+		/* For the second pass, we limit the total number of histogram pairs.
+		   After this limit is reached, we only keep searching for the best pair. */
+		var max_num_pairs uint = brotli_min_size_t(64*num_clusters, (num_clusters/2)*num_clusters)
+		if pairs_capacity < (max_num_pairs + 1) {
+			var _new_size uint
+			if pairs_capacity == 0 {
+				_new_size = max_num_pairs + 1
+			} else {
+				_new_size = pairs_capacity
+			}
+			var new_array []histogramPair
+			for _new_size < (max_num_pairs + 1) {
+				_new_size *= 2
+			}
+			new_array = make([]histogramPair, _new_size)
+			if pairs_capacity != 0 {
+				copy(new_array, pairs[:pairs_capacity])
+			}
+
+			pairs = new_array
+			pairs_capacity = _new_size
+		}
+
+		/* Collapse similar histograms. */
+		num_clusters = histogramCombineLiteral(out, cluster_size, histogram_symbols, clusters, pairs, num_clusters, in_size, max_histograms, max_num_pairs)
+	}
+
+	pairs = nil
+	cluster_size = nil
+
+	/* Find the optimal map from original histograms to the final ones. */
+	histogramRemapLiteral(in, in_size, clusters, num_clusters, out, histogram_symbols)
+
+	clusters = nil
+
+	/* Convert the context map to a canonical form. */
+	*out_size = histogramReindexLiteral(out, histogram_symbols, in_size)
+}

vendor/github.com/andybalholm/brotli/command.go

@@ -0,0 +1,254 @@
+package brotli
+
+var kInsBase = []uint32{
+	0,
+	1,
+	2,
+	3,
+	4,
+	5,
+	6,
+	8,
+	10,
+	14,
+	18,
+	26,
+	34,
+	50,
+	66,
+	98,
+	130,
+	194,
+	322,
+	578,
+	1090,
+	2114,
+	6210,
+	22594,
+}
+
+var kInsExtra = []uint32{
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	2,
+	2,
+	3,
+	3,
+	4,
+	4,
+	5,
+	5,
+	6,
+	7,
+	8,
+	9,
+	10,
+	12,
+	14,
+	24,
+}
+
+var kCopyBase = []uint32{
+	2,
+	3,
+	4,
+	5,
+	6,
+	7,
+	8,
+	9,
+	10,
+	12,
+	14,
+	18,
+	22,
+	30,
+	38,
+	54,
+	70,
+	102,
+	134,
+	198,
+	326,
+	582,
+	1094,
+	2118,
+}
+
+var kCopyExtra = []uint32{
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	2,
+	2,
+	3,
+	3,
+	4,
+	4,
+	5,
+	5,
+	6,
+	7,
+	8,
+	9,
+	10,
+	24,
+}
+
+func getInsertLengthCode(insertlen uint) uint16 {
+	if insertlen < 6 {
+		return uint16(insertlen)
+	} else if insertlen < 130 {
+		var nbits uint32 = log2FloorNonZero(insertlen-2) - 1
+		return uint16((nbits << 1) + uint32((insertlen-2)>>nbits) + 2)
+	} else if insertlen < 2114 {
+		return uint16(log2FloorNonZero(insertlen-66) + 10)
+	} else if insertlen < 6210 {
+		return 21
+	} else if insertlen < 22594 {
+		return 22
+	} else {
+		return 23
+	}
+}
+
+func getCopyLengthCode(copylen uint) uint16 {
+	if copylen < 10 {
+		return uint16(copylen - 2)
+	} else if copylen < 134 {
+		var nbits uint32 = log2FloorNonZero(copylen-6) - 1
+		return uint16((nbits << 1) + uint32((copylen-6)>>nbits) + 4)
+	} else if copylen < 2118 {
+		return uint16(log2FloorNonZero(copylen-70) + 12)
+	} else {
+		return 23
+	}
+}
+
+func combineLengthCodes(inscode uint16, copycode uint16, use_last_distance bool) uint16 {
+	var bits64 uint16 = uint16(copycode&0x7 | (inscode&0x7)<<3)
+	if use_last_distance && inscode < 8 && copycode < 16 {
+		if copycode < 8 {
+			return bits64
+		} else {
+			return bits64 | 64
+		}
+	} else {
+		/* Specification: 5 Encoding of ... (last table) */
+		/* offset = 2 * index, where index is in range [0..8] */
+		var offset uint32 = 2 * ((uint32(copycode) >> 3) + 3*(uint32(inscode)>>3))
+
+		/* All values in specification are K * 64,
+		   where   K = [2, 3, 6, 4, 5, 8, 7, 9, 10],
+		       i + 1 = [1, 2, 3, 4, 5, 6, 7, 8,  9],
+		   K - i - 1 = [1, 1, 3, 0, 0, 2, 0, 1,  2] = D.
+		   All values in D require only 2 bits to encode.
+		   Magic constant is shifted 6 bits left, to avoid final multiplication. */
+		offset = (offset << 5) + 0x40 + ((0x520D40 >> offset) & 0xC0)
+
+		return uint16(offset | uint32(bits64))
+	}
+}
+
+func getLengthCode(insertlen uint, copylen uint, use_last_distance bool, code *uint16) {
+	var inscode uint16 = getInsertLengthCode(insertlen)
+	var copycode uint16 = getCopyLengthCode(copylen)
+	*code = combineLengthCodes(inscode, copycode, use_last_distance)
+}
+
+func getInsertBase(inscode uint16) uint32 {
+	return kInsBase[inscode]
+}
+
+func getInsertExtra(inscode uint16) uint32 {
+	return kInsExtra[inscode]
+}
+
+func getCopyBase(copycode uint16) uint32 {
+	return kCopyBase[copycode]
+}
+
+func getCopyExtra(copycode uint16) uint32 {
+	return kCopyExtra[copycode]
+}
+
+type command struct {
+	insert_len_  uint32
+	copy_len_    uint32
+	dist_extra_  uint32
+	cmd_prefix_  uint16
+	dist_prefix_ uint16
+}
+
+/* distance_code is e.g. 0 for same-as-last short code, or 16 for offset 1. */
+func makeCommand(dist *distanceParams, insertlen uint, copylen uint, copylen_code_delta int, distance_code uint) (cmd command) {
+	/* Don't rely on signed int representation, use honest casts. */
+	var delta uint32 = uint32(byte(int8(copylen_code_delta)))
+	cmd.insert_len_ = uint32(insertlen)
+	cmd.copy_len_ = uint32(uint32(copylen) | delta<<25)
+
+	/* The distance prefix and extra bits are stored in this Command as if
+	   npostfix and ndirect were 0, they are only recomputed later after the
+	   clustering if needed. */
+	prefixEncodeCopyDistance(distance_code, uint(dist.num_direct_distance_codes), uint(dist.distance_postfix_bits), &cmd.dist_prefix_, &cmd.dist_extra_)
+	getLengthCode(insertlen, uint(int(copylen)+copylen_code_delta), (cmd.dist_prefix_&0x3FF == 0), &cmd.cmd_prefix_)
+
+	return cmd
+}
+
+func makeInsertCommand(insertlen uint) (cmd command) {
+	cmd.insert_len_ = uint32(insertlen)
+	cmd.copy_len_ = 4 << 25
+	cmd.dist_extra_ = 0
+	cmd.dist_prefix_ = numDistanceShortCodes
+	getLengthCode(insertlen, 4, false, &cmd.cmd_prefix_)
+	return cmd
+}
+
+func commandRestoreDistanceCode(self *command, dist *distanceParams) uint32 {
+	if uint32(self.dist_prefix_&0x3FF) < numDistanceShortCodes+dist.num_direct_distance_codes {
+		return uint32(self.dist_prefix_) & 0x3FF
+	} else {
+		var dcode uint32 = uint32(self.dist_prefix_) & 0x3FF
+		var nbits uint32 = uint32(self.dist_prefix_) >> 10
+		var extra uint32 = self.dist_extra_
+		var postfix_mask uint32 = (1 << dist.distance_postfix_bits) - 1
+		var hcode uint32 = (dcode - dist.num_direct_distance_codes - numDistanceShortCodes) >> dist.distance_postfix_bits
+		var lcode uint32 = (dcode - dist.num_direct_distance_codes - numDistanceShortCodes) & postfix_mask
+		var offset uint32 = ((2 + (hcode & 1)) << nbits) - 4
+		return ((offset + extra) << dist.distance_postfix_bits) + lcode + dist.num_direct_distance_codes + numDistanceShortCodes
+	}
+}
+
+func commandDistanceContext(self *command) uint32 {
+	var r uint32 = uint32(self.cmd_prefix_) >> 6
+	var c uint32 = uint32(self.cmd_prefix_) & 7
+	if (r == 0 || r == 2 || r == 4 || r == 7) && (c <= 2) {
+		return c
+	}
+
+	return 3
+}
+
+func commandCopyLen(self *command) uint32 {
+	return self.copy_len_ & 0x1FFFFFF
+}
+
+func commandCopyLenCode(self *command) uint32 {
+	var modifier uint32 = self.copy_len_ >> 25
+	var delta int32 = int32(int8(byte(modifier | (modifier&0x40)<<1)))
+	return uint32(int32(self.copy_len_&0x1FFFFFF) + delta)
+}

vendor/github.com/andybalholm/brotli/compress_fragment.go

@@ -0,0 +1,834 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2015 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Function for fast encoding of an input fragment, independently from the input
+   history. This function uses one-pass processing: when we find a backward
+   match, we immediately emit the corresponding command and literal codes to
+   the bit stream.
+
+   Adapted from the CompressFragment() function in
+   https://github.com/google/snappy/blob/master/snappy.cc */
+
+const maxDistance_compress_fragment = 262128
+
+func hash5(p []byte, shift uint) uint32 {
+	var h uint64 = (binary.LittleEndian.Uint64(p) << 24) * uint64(kHashMul32)
+	return uint32(h >> shift)
+}
+
+func hashBytesAtOffset5(v uint64, offset int, shift uint) uint32 {
+	assert(offset >= 0)
+	assert(offset <= 3)
+	{
+		var h uint64 = ((v >> uint(8*offset)) << 24) * uint64(kHashMul32)
+		return uint32(h >> shift)
+	}
+}
+
+func isMatch5(p1 []byte, p2 []byte) bool {
+	return binary.LittleEndian.Uint32(p1) == binary.LittleEndian.Uint32(p2) &&
+		p1[4] == p2[4]
+}
+
+/* Builds a literal prefix code into "depths" and "bits" based on the statistics
+   of the "input" string and stores it into the bit stream.
+   Note that the prefix code here is built from the pre-LZ77 input, therefore
+   we can only approximate the statistics of the actual literal stream.
+   Moreover, for long inputs we build a histogram from a sample of the input
+   and thus have to assign a non-zero depth for each literal.
+   Returns estimated compression ratio millibytes/char for encoding given input
+   with generated code. */
+func buildAndStoreLiteralPrefixCode(input []byte, input_size uint, depths []byte, bits []uint16, storage_ix *uint, storage []byte) uint {
+	var histogram = [256]uint32{0}
+	var histogram_total uint
+	var i uint
+	if input_size < 1<<15 {
+		for i = 0; i < input_size; i++ {
+			histogram[input[i]]++
+		}
+
+		histogram_total = input_size
+		for i = 0; i < 256; i++ {
+			/* We weigh the first 11 samples with weight 3 to account for the
+			   balancing effect of the LZ77 phase on the histogram. */
+			var adjust uint32 = 2 * brotli_min_uint32_t(histogram[i], 11)
+			histogram[i] += adjust
+			histogram_total += uint(adjust)
+		}
+	} else {
+		const kSampleRate uint = 29
+		for i = 0; i < input_size; i += kSampleRate {
+			histogram[input[i]]++
+		}
+
+		histogram_total = (input_size + kSampleRate - 1) / kSampleRate
+		for i = 0; i < 256; i++ {
+			/* We add 1 to each population count to avoid 0 bit depths (since this is
+			   only a sample and we don't know if the symbol appears or not), and we
+			   weigh the first 11 samples with weight 3 to account for the balancing
+			   effect of the LZ77 phase on the histogram (more frequent symbols are
+			   more likely to be in backward references instead as literals). */
+			var adjust uint32 = 1 + 2*brotli_min_uint32_t(histogram[i], 11)
+			histogram[i] += adjust
+			histogram_total += uint(adjust)
+		}
+	}
+
+	buildAndStoreHuffmanTreeFast(histogram[:], histogram_total, /* max_bits = */
+		8, depths, bits, storage_ix, storage)
+	{
+		var literal_ratio uint = 0
+		for i = 0; i < 256; i++ {
+			if histogram[i] != 0 {
+				literal_ratio += uint(histogram[i] * uint32(depths[i]))
+			}
+		}
+
+		/* Estimated encoding ratio, millibytes per symbol. */
+		return (literal_ratio * 125) / histogram_total
+	}
+}
+
+/* Builds a command and distance prefix code (each 64 symbols) into "depth" and
+   "bits" based on "histogram" and stores it into the bit stream. */
+func buildAndStoreCommandPrefixCode1(histogram []uint32, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
+	var tree [129]huffmanTree
+	var cmd_depth = [numCommandSymbols]byte{0}
+	/* Tree size for building a tree over 64 symbols is 2 * 64 + 1. */
+
+	var cmd_bits [64]uint16
+
+	createHuffmanTree(histogram, 64, 15, tree[:], depth)
+	createHuffmanTree(histogram[64:], 64, 14, tree[:], depth[64:])
+
+	/* We have to jump through a few hoops here in order to compute
+	   the command bits because the symbols are in a different order than in
+	   the full alphabet. This looks complicated, but having the symbols
+	   in this order in the command bits saves a few branches in the Emit*
+	   functions. */
+	copy(cmd_depth[:], depth[:24])
+
+	copy(cmd_depth[24:][:], depth[40:][:8])
+	copy(cmd_depth[32:][:], depth[24:][:8])
+	copy(cmd_depth[40:][:], depth[48:][:8])
+	copy(cmd_depth[48:][:], depth[32:][:8])
+	copy(cmd_depth[56:][:], depth[56:][:8])
+	convertBitDepthsToSymbols(cmd_depth[:], 64, cmd_bits[:])
+	copy(bits, cmd_bits[:24])
+	copy(bits[24:], cmd_bits[32:][:8])
+	copy(bits[32:], cmd_bits[48:][:8])
+	copy(bits[40:], cmd_bits[24:][:8])
+	copy(bits[48:], cmd_bits[40:][:8])
+	copy(bits[56:], cmd_bits[56:][:8])
+	convertBitDepthsToSymbols(depth[64:], 64, bits[64:])
+	{
+		/* Create the bit length array for the full command alphabet. */
+		var i uint
+		for i := 0; i < int(64); i++ {
+			cmd_depth[i] = 0
+		} /* only 64 first values were used */
+		copy(cmd_depth[:], depth[:8])
+		copy(cmd_depth[64:][:], depth[8:][:8])
+		copy(cmd_depth[128:][:], depth[16:][:8])
+		copy(cmd_depth[192:][:], depth[24:][:8])
+		copy(cmd_depth[384:][:], depth[32:][:8])
+		for i = 0; i < 8; i++ {
+			cmd_depth[128+8*i] = depth[40+i]
+			cmd_depth[256+8*i] = depth[48+i]
+			cmd_depth[448+8*i] = depth[56+i]
+		}
+
+		storeHuffmanTree(cmd_depth[:], numCommandSymbols, tree[:], storage_ix, storage)
+	}
+
+	storeHuffmanTree(depth[64:], 64, tree[:], storage_ix, storage)
+}
+
+/* REQUIRES: insertlen < 6210 */
+func emitInsertLen1(insertlen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
+	if insertlen < 6 {
+		var code uint = insertlen + 40
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		histo[code]++
+	} else if insertlen < 130 {
+		var tail uint = insertlen - 2
+		var nbits uint32 = log2FloorNonZero(tail) - 1
+		var prefix uint = tail >> nbits
+		var inscode uint = uint((nbits << 1) + uint32(prefix) + 42)
+		writeBits(uint(depth[inscode]), uint64(bits[inscode]), storage_ix, storage)
+		writeBits(uint(nbits), uint64(tail)-(uint64(prefix)<<nbits), storage_ix, storage)
+		histo[inscode]++
+	} else if insertlen < 2114 {
+		var tail uint = insertlen - 66
+		var nbits uint32 = log2FloorNonZero(tail)
+		var code uint = uint(nbits + 50)
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		writeBits(uint(nbits), uint64(tail)-(uint64(uint(1))<<nbits), storage_ix, storage)
+		histo[code]++
+	} else {
+		writeBits(uint(depth[61]), uint64(bits[61]), storage_ix, storage)
+		writeBits(12, uint64(insertlen)-2114, storage_ix, storage)
+		histo[61]++
+	}
+}
+
+func emitLongInsertLen(insertlen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
+	if insertlen < 22594 {
+		writeBits(uint(depth[62]), uint64(bits[62]), storage_ix, storage)
+		writeBits(14, uint64(insertlen)-6210, storage_ix, storage)
+		histo[62]++
+	} else {
+		writeBits(uint(depth[63]), uint64(bits[63]), storage_ix, storage)
+		writeBits(24, uint64(insertlen)-22594, storage_ix, storage)
+		histo[63]++
+	}
+}
+
+func emitCopyLen1(copylen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
+	if copylen < 10 {
+		writeBits(uint(depth[copylen+14]), uint64(bits[copylen+14]), storage_ix, storage)
+		histo[copylen+14]++
+	} else if copylen < 134 {
+		var tail uint = copylen - 6
+		var nbits uint32 = log2FloorNonZero(tail) - 1
+		var prefix uint = tail >> nbits
+		var code uint = uint((nbits << 1) + uint32(prefix) + 20)
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		writeBits(uint(nbits), uint64(tail)-(uint64(prefix)<<nbits), storage_ix, storage)
+		histo[code]++
+	} else if copylen < 2118 {
+		var tail uint = copylen - 70
+		var nbits uint32 = log2FloorNonZero(tail)
+		var code uint = uint(nbits + 28)
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		writeBits(uint(nbits), uint64(tail)-(uint64(uint(1))<<nbits), storage_ix, storage)
+		histo[code]++
+	} else {
+		writeBits(uint(depth[39]), uint64(bits[39]), storage_ix, storage)
+		writeBits(24, uint64(copylen)-2118, storage_ix, storage)
+		histo[39]++
+	}
+}
+
+func emitCopyLenLastDistance1(copylen uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
+	if copylen < 12 {
+		writeBits(uint(depth[copylen-4]), uint64(bits[copylen-4]), storage_ix, storage)
+		histo[copylen-4]++
+	} else if copylen < 72 {
+		var tail uint = copylen - 8
+		var nbits uint32 = log2FloorNonZero(tail) - 1
+		var prefix uint = tail >> nbits
+		var code uint = uint((nbits << 1) + uint32(prefix) + 4)
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		writeBits(uint(nbits), uint64(tail)-(uint64(prefix)<<nbits), storage_ix, storage)
+		histo[code]++
+	} else if copylen < 136 {
+		var tail uint = copylen - 8
+		var code uint = (tail >> 5) + 30
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		writeBits(5, uint64(tail)&31, storage_ix, storage)
+		writeBits(uint(depth[64]), uint64(bits[64]), storage_ix, storage)
+		histo[code]++
+		histo[64]++
+	} else if copylen < 2120 {
+		var tail uint = copylen - 72
+		var nbits uint32 = log2FloorNonZero(tail)
+		var code uint = uint(nbits + 28)
+		writeBits(uint(depth[code]), uint64(bits[code]), storage_ix, storage)
+		writeBits(uint(nbits), uint64(tail)-(uint64(uint(1))<<nbits), storage_ix, storage)
+		writeBits(uint(depth[64]), uint64(bits[64]), storage_ix, storage)
+		histo[code]++
+		histo[64]++
+	} else {
+		writeBits(uint(depth[39]), uint64(bits[39]), storage_ix, storage)
+		writeBits(24, uint64(copylen)-2120, storage_ix, storage)
+		writeBits(uint(depth[64]), uint64(bits[64]), storage_ix, storage)
+		histo[39]++
+		histo[64]++
+	}
+}
+
+func emitDistance1(distance uint, depth []byte, bits []uint16, histo []uint32, storage_ix *uint, storage []byte) {
+	var d uint = distance + 3
+	var nbits uint32 = log2FloorNonZero(d) - 1
+	var prefix uint = (d >> nbits) & 1
+	var offset uint = (2 + prefix) << nbits
+	var distcode uint = uint(2*(nbits-1) + uint32(prefix) + 80)
+	writeBits(uint(depth[distcode]), uint64(bits[distcode]), storage_ix, storage)
+	writeBits(uint(nbits), uint64(d)-uint64(offset), storage_ix, storage)
+	histo[distcode]++
+}
+
+func emitLiterals(input []byte, len uint, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
+	var j uint
+	for j = 0; j < len; j++ {
+		var lit byte = input[j]
+		writeBits(uint(depth[lit]), uint64(bits[lit]), storage_ix, storage)
+	}
+}
+
+/* REQUIRES: len <= 1 << 24. */
+func storeMetaBlockHeader1(len uint, is_uncompressed bool, storage_ix *uint, storage []byte) {
+	var nibbles uint = 6
+
+	/* ISLAST */
+	writeBits(1, 0, storage_ix, storage)
+
+	if len <= 1<<16 {
+		nibbles = 4
+	} else if len <= 1<<20 {
+		nibbles = 5
+	}
+
+	writeBits(2, uint64(nibbles)-4, storage_ix, storage)
+	writeBits(nibbles*4, uint64(len)-1, storage_ix, storage)
+
+	/* ISUNCOMPRESSED */
+	writeSingleBit(is_uncompressed, storage_ix, storage)
+}
+
+func updateBits(n_bits uint, bits uint32, pos uint, array []byte) {
+	for n_bits > 0 {
+		var byte_pos uint = pos >> 3
+		var n_unchanged_bits uint = pos & 7
+		var n_changed_bits uint = brotli_min_size_t(n_bits, 8-n_unchanged_bits)
+		var total_bits uint = n_unchanged_bits + n_changed_bits
+		var mask uint32 = (^((1 << total_bits) - 1)) | ((1 << n_unchanged_bits) - 1)
+		var unchanged_bits uint32 = uint32(array[byte_pos]) & mask
+		var changed_bits uint32 = bits & ((1 << n_changed_bits) - 1)
+		array[byte_pos] = byte(changed_bits<<n_unchanged_bits | unchanged_bits)
+		n_bits -= n_changed_bits
+		bits >>= n_changed_bits
+		pos += n_changed_bits
+	}
+}
+
+func rewindBitPosition1(new_storage_ix uint, storage_ix *uint, storage []byte) {
+	var bitpos uint = new_storage_ix & 7
+	var mask uint = (1 << bitpos) - 1
+	storage[new_storage_ix>>3] &= byte(mask)
+	*storage_ix = new_storage_ix
+}
+
+var shouldMergeBlock_kSampleRate uint = 43
+
+func shouldMergeBlock(data []byte, len uint, depths []byte) bool {
+	var histo = [256]uint{0}
+	var i uint
+	for i = 0; i < len; i += shouldMergeBlock_kSampleRate {
+		histo[data[i]]++
+	}
+	{
+		var total uint = (len + shouldMergeBlock_kSampleRate - 1) / shouldMergeBlock_kSampleRate
+		var r float64 = (fastLog2(total)+0.5)*float64(total) + 200
+		for i = 0; i < 256; i++ {
+			r -= float64(histo[i]) * (float64(depths[i]) + fastLog2(histo[i]))
+		}
+
+		return r >= 0.0
+	}
+}
+
+func shouldUseUncompressedMode(metablock_start []byte, next_emit []byte, insertlen uint, literal_ratio uint) bool {
+	var compressed uint = uint(-cap(next_emit) + cap(metablock_start))
+	if compressed*50 > insertlen {
+		return false
+	} else {
+		return literal_ratio > 980
+	}
+}
+
+func emitUncompressedMetaBlock1(begin []byte, end []byte, storage_ix_start uint, storage_ix *uint, storage []byte) {
+	var len uint = uint(-cap(end) + cap(begin))
+	rewindBitPosition1(storage_ix_start, storage_ix, storage)
+	storeMetaBlockHeader1(uint(len), true, storage_ix, storage)
+	*storage_ix = (*storage_ix + 7) &^ 7
+	copy(storage[*storage_ix>>3:], begin[:len])
+	*storage_ix += uint(len << 3)
+	storage[*storage_ix>>3] = 0
+}
+
+var kCmdHistoSeed = [128]uint32{
+	0,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	0,
+	0,
+	0,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	0,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	1,
+	0,
+	0,
+	0,
+	0,
+}
+
+var compressFragmentFastImpl_kFirstBlockSize uint = 3 << 15
+var compressFragmentFastImpl_kMergeBlockSize uint = 1 << 16
+
+func compressFragmentFastImpl(in []byte, input_size uint, is_last bool, table []int, table_bits uint, cmd_depth []byte, cmd_bits []uint16, cmd_code_numbits *uint, cmd_code []byte, storage_ix *uint, storage []byte) {
+	var cmd_histo [128]uint32
+	var ip_end int
+	var next_emit int = 0
+	var base_ip int = 0
+	var input int = 0
+	const kInputMarginBytes uint = windowGap
+	const kMinMatchLen uint = 5
+	var metablock_start int = input
+	var block_size uint = brotli_min_size_t(input_size, compressFragmentFastImpl_kFirstBlockSize)
+	var total_block_size uint = block_size
+	var mlen_storage_ix uint = *storage_ix + 3
+	var lit_depth [256]byte
+	var lit_bits [256]uint16
+	var literal_ratio uint
+	var ip int
+	var last_distance int
+	var shift uint = 64 - table_bits
+
+	/* "next_emit" is a pointer to the first byte that is not covered by a
+	   previous copy. Bytes between "next_emit" and the start of the next copy or
+	   the end of the input will be emitted as literal bytes. */
+
+	/* Save the start of the first block for position and distance computations.
+	 */
+
+	/* Save the bit position of the MLEN field of the meta-block header, so that
+	   we can update it later if we decide to extend this meta-block. */
+	storeMetaBlockHeader1(block_size, false, storage_ix, storage)
+
+	/* No block splits, no contexts. */
+	writeBits(13, 0, storage_ix, storage)
+
+	literal_ratio = buildAndStoreLiteralPrefixCode(in[input:], block_size, lit_depth[:], lit_bits[:], storage_ix, storage)
+	{
+		/* Store the pre-compressed command and distance prefix codes. */
+		var i uint
+		for i = 0; i+7 < *cmd_code_numbits; i += 8 {
+			writeBits(8, uint64(cmd_code[i>>3]), storage_ix, storage)
+		}
+	}
+
+	writeBits(*cmd_code_numbits&7, uint64(cmd_code[*cmd_code_numbits>>3]), storage_ix, storage)
+
+	/* Initialize the command and distance histograms. We will gather
+	   statistics of command and distance codes during the processing
+	   of this block and use it to update the command and distance
+	   prefix codes for the next block. */
+emit_commands:
+	copy(cmd_histo[:], kCmdHistoSeed[:])
+
+	/* "ip" is the input pointer. */
+	ip = input
+
+	last_distance = -1
+	ip_end = int(uint(input) + block_size)
+
+	if block_size >= kInputMarginBytes {
+		var len_limit uint = brotli_min_size_t(block_size-kMinMatchLen, input_size-kInputMarginBytes)
+		var ip_limit int = int(uint(input) + len_limit)
+		/* For the last block, we need to keep a 16 bytes margin so that we can be
+		   sure that all distances are at most window size - 16.
+		   For all other blocks, we only need to keep a margin of 5 bytes so that
+		   we don't go over the block size with a copy. */
+
+		var next_hash uint32
+		ip++
+		for next_hash = hash5(in[ip:], shift); ; {
+			var skip uint32 = 32
+			var next_ip int = ip
+			/* Step 1: Scan forward in the input looking for a 5-byte-long match.
+			   If we get close to exhausting the input then goto emit_remainder.
+
+			   Heuristic match skipping: If 32 bytes are scanned with no matches
+			   found, start looking only at every other byte. If 32 more bytes are
+			   scanned, look at every third byte, etc.. When a match is found,
+			   immediately go back to looking at every byte. This is a small loss
+			   (~5% performance, ~0.1% density) for compressible data due to more
+			   bookkeeping, but for non-compressible data (such as JPEG) it's a huge
+			   win since the compressor quickly "realizes" the data is incompressible
+			   and doesn't bother looking for matches everywhere.
+
+			   The "skip" variable keeps track of how many bytes there are since the
+			   last match; dividing it by 32 (i.e. right-shifting by five) gives the
+			   number of bytes to move ahead for each iteration. */
+
+			var candidate int
+			assert(next_emit < ip)
+
+		trawl:
+			for {
+				var hash uint32 = next_hash
+				var bytes_between_hash_lookups uint32 = skip >> 5
+				skip++
+				assert(hash == hash5(in[next_ip:], shift))
+				ip = next_ip
+				next_ip = int(uint32(ip) + bytes_between_hash_lookups)
+				if next_ip > ip_limit {
+					goto emit_remainder
+				}
+
+				next_hash = hash5(in[next_ip:], shift)
+				candidate = ip - last_distance
+				if isMatch5(in[ip:], in[candidate:]) {
+					if candidate < ip {
+						table[hash] = int(ip - base_ip)
+						break
+					}
+				}
+
+				candidate = base_ip + table[hash]
+				assert(candidate >= base_ip)
+				assert(candidate < ip)
+
+				table[hash] = int(ip - base_ip)
+				if isMatch5(in[ip:], in[candidate:]) {
+					break
+				}
+			}
+
+			/* Check copy distance. If candidate is not feasible, continue search.
+			   Checking is done outside of hot loop to reduce overhead. */
+			if ip-candidate > maxDistance_compress_fragment {
+				goto trawl
+			}
+
+			/* Step 2: Emit the found match together with the literal bytes from
+			   "next_emit" to the bit stream, and then see if we can find a next match
+			   immediately afterwards. Repeat until we find no match for the input
+			   without emitting some literal bytes. */
+			{
+				var base int = ip
+				/* > 0 */
+				var matched uint = 5 + findMatchLengthWithLimit(in[candidate+5:], in[ip+5:], uint(ip_end-ip)-5)
+				var distance int = int(base - candidate)
+				/* We have a 5-byte match at ip, and we need to emit bytes in
+				   [next_emit, ip). */
+
+				var insert uint = uint(base - next_emit)
+				ip += int(matched)
+				if insert < 6210 {
+					emitInsertLen1(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+				} else if shouldUseUncompressedMode(in[metablock_start:], in[next_emit:], insert, literal_ratio) {
+					emitUncompressedMetaBlock1(in[metablock_start:], in[base:], mlen_storage_ix-3, storage_ix, storage)
+					input_size -= uint(base - input)
+					input = base
+					next_emit = input
+					goto next_block
+				} else {
+					emitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+				}
+
+				emitLiterals(in[next_emit:], insert, lit_depth[:], lit_bits[:], storage_ix, storage)
+				if distance == last_distance {
+					writeBits(uint(cmd_depth[64]), uint64(cmd_bits[64]), storage_ix, storage)
+					cmd_histo[64]++
+				} else {
+					emitDistance1(uint(distance), cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+					last_distance = distance
+				}
+
+				emitCopyLenLastDistance1(matched, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+
+				next_emit = ip
+				if ip >= ip_limit {
+					goto emit_remainder
+				}
+
+				/* We could immediately start working at ip now, but to improve
+				   compression we first update "table" with the hashes of some positions
+				   within the last copy. */
+				{
+					var input_bytes uint64 = binary.LittleEndian.Uint64(in[ip-3:])
+					var prev_hash uint32 = hashBytesAtOffset5(input_bytes, 0, shift)
+					var cur_hash uint32 = hashBytesAtOffset5(input_bytes, 3, shift)
+					table[prev_hash] = int(ip - base_ip - 3)
+					prev_hash = hashBytesAtOffset5(input_bytes, 1, shift)
+					table[prev_hash] = int(ip - base_ip - 2)
+					prev_hash = hashBytesAtOffset5(input_bytes, 2, shift)
+					table[prev_hash] = int(ip - base_ip - 1)
+
+					candidate = base_ip + table[cur_hash]
+					table[cur_hash] = int(ip - base_ip)
+				}
+			}
+
+			for isMatch5(in[ip:], in[candidate:]) {
+				var base int = ip
+				/* We have a 5-byte match at ip, and no need to emit any literal bytes
+				   prior to ip. */
+
+				var matched uint = 5 + findMatchLengthWithLimit(in[candidate+5:], in[ip+5:], uint(ip_end-ip)-5)
+				if ip-candidate > maxDistance_compress_fragment {
+					break
+				}
+				ip += int(matched)
+				last_distance = int(base - candidate) /* > 0 */
+				emitCopyLen1(matched, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+				emitDistance1(uint(last_distance), cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+
+				next_emit = ip
+				if ip >= ip_limit {
+					goto emit_remainder
+				}
+
+				/* We could immediately start working at ip now, but to improve
+				   compression we first update "table" with the hashes of some positions
+				   within the last copy. */
+				{
+					var input_bytes uint64 = binary.LittleEndian.Uint64(in[ip-3:])
+					var prev_hash uint32 = hashBytesAtOffset5(input_bytes, 0, shift)
+					var cur_hash uint32 = hashBytesAtOffset5(input_bytes, 3, shift)
+					table[prev_hash] = int(ip - base_ip - 3)
+					prev_hash = hashBytesAtOffset5(input_bytes, 1, shift)
+					table[prev_hash] = int(ip - base_ip - 2)
+					prev_hash = hashBytesAtOffset5(input_bytes, 2, shift)
+					table[prev_hash] = int(ip - base_ip - 1)
+
+					candidate = base_ip + table[cur_hash]
+					table[cur_hash] = int(ip - base_ip)
+				}
+			}
+
+			ip++
+			next_hash = hash5(in[ip:], shift)
+		}
+	}
+
+emit_remainder:
+	assert(next_emit <= ip_end)
+	input += int(block_size)
+	input_size -= block_size
+	block_size = brotli_min_size_t(input_size, compressFragmentFastImpl_kMergeBlockSize)
+
+	/* Decide if we want to continue this meta-block instead of emitting the
+	   last insert-only command. */
+	if input_size > 0 && total_block_size+block_size <= 1<<20 && shouldMergeBlock(in[input:], block_size, lit_depth[:]) {
+		assert(total_block_size > 1<<16)
+
+		/* Update the size of the current meta-block and continue emitting commands.
+		   We can do this because the current size and the new size both have 5
+		   nibbles. */
+		total_block_size += block_size
+
+		updateBits(20, uint32(total_block_size-1), mlen_storage_ix, storage)
+		goto emit_commands
+	}
+
+	/* Emit the remaining bytes as literals. */
+	if next_emit < ip_end {
+		var insert uint = uint(ip_end - next_emit)
+		if insert < 6210 {
+			emitInsertLen1(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+			emitLiterals(in[next_emit:], insert, lit_depth[:], lit_bits[:], storage_ix, storage)
+		} else if shouldUseUncompressedMode(in[metablock_start:], in[next_emit:], insert, literal_ratio) {
+			emitUncompressedMetaBlock1(in[metablock_start:], in[ip_end:], mlen_storage_ix-3, storage_ix, storage)
+		} else {
+			emitLongInsertLen(insert, cmd_depth, cmd_bits, cmd_histo[:], storage_ix, storage)
+			emitLiterals(in[next_emit:], insert, lit_depth[:], lit_bits[:], storage_ix, storage)
+		}
+	}
+
+	next_emit = ip_end
+
+	/* If we have more data, write a new meta-block header and prefix codes and
+	   then continue emitting commands. */
+next_block:
+	if input_size > 0 {
+		metablock_start = input
+		block_size = brotli_min_size_t(input_size, compressFragmentFastImpl_kFirstBlockSize)
+		total_block_size = block_size
+
+		/* Save the bit position of the MLEN field of the meta-block header, so that
+		   we can update it later if we decide to extend this meta-block. */
+		mlen_storage_ix = *storage_ix + 3
+
+		storeMetaBlockHeader1(block_size, false, storage_ix, storage)
+
+		/* No block splits, no contexts. */
+		writeBits(13, 0, storage_ix, storage)
+
+		literal_ratio = buildAndStoreLiteralPrefixCode(in[input:], block_size, lit_depth[:], lit_bits[:], storage_ix, storage)
+		buildAndStoreCommandPrefixCode1(cmd_histo[:], cmd_depth, cmd_bits, storage_ix, storage)
+		goto emit_commands
+	}
+
+	if !is_last {
+		/* If this is not the last block, update the command and distance prefix
+		   codes for the next block and store the compressed forms. */
+		cmd_code[0] = 0
+
+		*cmd_code_numbits = 0
+		buildAndStoreCommandPrefixCode1(cmd_histo[:], cmd_depth, cmd_bits, cmd_code_numbits, cmd_code)
+	}
+}
+
+/* Compresses "input" string to the "*storage" buffer as one or more complete
+   meta-blocks, and updates the "*storage_ix" bit position.
+
+   If "is_last" is 1, emits an additional empty last meta-block.
+
+   "cmd_depth" and "cmd_bits" contain the command and distance prefix codes
+   (see comment in encode.h) used for the encoding of this input fragment.
+   If "is_last" is 0, they are updated to reflect the statistics
+   of this input fragment, to be used for the encoding of the next fragment.
+
+   "*cmd_code_numbits" is the number of bits of the compressed representation
+   of the command and distance prefix codes, and "cmd_code" is an array of
+   at least "(*cmd_code_numbits + 7) >> 3" size that contains the compressed
+   command and distance prefix codes. If "is_last" is 0, these are also
+   updated to represent the updated "cmd_depth" and "cmd_bits".
+
+   REQUIRES: "input_size" is greater than zero, or "is_last" is 1.
+   REQUIRES: "input_size" is less or equal to maximal metablock size (1 << 24).
+   REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
+   REQUIRES: "table_size" is an odd (9, 11, 13, 15) power of two
+   OUTPUT: maximal copy distance <= |input_size|
+   OUTPUT: maximal copy distance <= BROTLI_MAX_BACKWARD_LIMIT(18) */
+func compressFragmentFast(input []byte, input_size uint, is_last bool, table []int, table_size uint, cmd_depth []byte, cmd_bits []uint16, cmd_code_numbits *uint, cmd_code []byte, storage_ix *uint, storage []byte) {
+	var initial_storage_ix uint = *storage_ix
+	var table_bits uint = uint(log2FloorNonZero(table_size))
+
+	if input_size == 0 {
+		assert(is_last)
+		writeBits(1, 1, storage_ix, storage) /* islast */
+		writeBits(1, 1, storage_ix, storage) /* isempty */
+		*storage_ix = (*storage_ix + 7) &^ 7
+		return
+	}
+
+	compressFragmentFastImpl(input, input_size, is_last, table, table_bits, cmd_depth, cmd_bits, cmd_code_numbits, cmd_code, storage_ix, storage)
+
+	/* If output is larger than single uncompressed block, rewrite it. */
+	if *storage_ix-initial_storage_ix > 31+(input_size<<3) {
+		emitUncompressedMetaBlock1(input, input[input_size:], initial_storage_ix, storage_ix, storage)
+	}
+
+	if is_last {
+		writeBits(1, 1, storage_ix, storage) /* islast */
+		writeBits(1, 1, storage_ix, storage) /* isempty */
+		*storage_ix = (*storage_ix + 7) &^ 7
+	}
+}

vendor/github.com/andybalholm/brotli/compress_fragment_two_pass.go

@@ -0,0 +1,748 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2015 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Function for fast encoding of an input fragment, independently from the input
+   history. This function uses two-pass processing: in the first pass we save
+   the found backward matches and literal bytes into a buffer, and in the
+   second pass we emit them into the bit stream using prefix codes built based
+   on the actual command and literal byte histograms. */
+
+const kCompressFragmentTwoPassBlockSize uint = 1 << 17
+
+func hash1(p []byte, shift uint, length uint) uint32 {
+	var h uint64 = (binary.LittleEndian.Uint64(p) << ((8 - length) * 8)) * uint64(kHashMul32)
+	return uint32(h >> shift)
+}
+
+func hashBytesAtOffset(v uint64, offset uint, shift uint, length uint) uint32 {
+	assert(offset <= 8-length)
+	{
+		var h uint64 = ((v >> (8 * offset)) << ((8 - length) * 8)) * uint64(kHashMul32)
+		return uint32(h >> shift)
+	}
+}
+
+func isMatch1(p1 []byte, p2 []byte, length uint) bool {
+	if binary.LittleEndian.Uint32(p1) != binary.LittleEndian.Uint32(p2) {
+		return false
+	}
+	if length == 4 {
+		return true
+	}
+	return p1[4] == p2[4] && p1[5] == p2[5]
+}
+
+/* Builds a command and distance prefix code (each 64 symbols) into "depth" and
+   "bits" based on "histogram" and stores it into the bit stream. */
+func buildAndStoreCommandPrefixCode(histogram []uint32, depth []byte, bits []uint16, storage_ix *uint, storage []byte) {
+	var tree [129]huffmanTree
+	var cmd_depth = [numCommandSymbols]byte{0}
+	/* Tree size for building a tree over 64 symbols is 2 * 64 + 1. */
+
+	var cmd_bits [64]uint16
+	createHuffmanTree(histogram, 64, 15, tree[:], depth)
+	createHuffmanTree(histogram[64:], 64, 14, tree[:], depth[64:])
+
+	/* We have to jump through a few hoops here in order to compute
+	   the command bits because the symbols are in a different order than in
+	   the full alphabet. This looks complicated, but having the symbols
+	   in this order in the command bits saves a few branches in the Emit*
+	   functions. */
+	copy(cmd_depth[:], depth[24:][:24])
+
+	copy(cmd_depth[24:][:], depth[:8])
+	copy(cmd_depth[32:][:], depth[48:][:8])
+	copy(cmd_depth[40:][:], depth[8:][:8])
+	copy(cmd_depth[48:][:], depth[56:][:8])
+	copy(cmd_depth[56:][:], depth[16:][:8])
+	convertBitDepthsToSymbols(cmd_depth[:], 64, cmd_bits[:])
+	copy(bits, cmd_bits[24:][:8])
+	copy(bits[8:], cmd_bits[40:][:8])
+	copy(bits[16:], cmd_bits[56:][:8])
+	copy(bits[24:], cmd_bits[:24])
+	copy(bits[48:], cmd_bits[32:][:8])
+	copy(bits[56:], cmd_bits[48:][:8])
+	convertBitDepthsToSymbols(depth[64:], 64, bits[64:])
+	{
+		/* Create the bit length array for the full command alphabet. */
+		var i uint
+		for i := 0; i < int(64); i++ {
+			cmd_depth[i] = 0
+		} /* only 64 first values were used */
+		copy(cmd_depth[:], depth[24:][:8])
+		copy(cmd_depth[64:][:], depth[32:][:8])
+		copy(cmd_depth[128:][:], depth[40:][:8])
+		copy(cmd_depth[192:][:], depth[48:][:8])
+		copy(cmd_depth[384:][:], depth[56:][:8])
+		for i = 0; i < 8; i++ {
+			cmd_depth[128+8*i] = depth[i]
+			cmd_depth[256+8*i] = depth[8+i]
+			cmd_depth[448+8*i] = depth[16+i]
+		}
+
+		storeHuffmanTree(cmd_depth[:], numCommandSymbols, tree[:], storage_ix, storage)
+	}
+
+	storeHuffmanTree(depth[64:], 64, tree[:], storage_ix, storage)
+}
+
+func emitInsertLen(insertlen uint32, commands *[]uint32) {
+	if insertlen < 6 {
+		(*commands)[0] = insertlen
+	} else if insertlen < 130 {
+		var tail uint32 = insertlen - 2
+		var nbits uint32 = log2FloorNonZero(uint(tail)) - 1
+		var prefix uint32 = tail >> nbits
+		var inscode uint32 = (nbits << 1) + prefix + 2
+		var extra uint32 = tail - (prefix << nbits)
+		(*commands)[0] = inscode | extra<<8
+	} else if insertlen < 2114 {
+		var tail uint32 = insertlen - 66
+		var nbits uint32 = log2FloorNonZero(uint(tail))
+		var code uint32 = nbits + 10
+		var extra uint32 = tail - (1 << nbits)
+		(*commands)[0] = code | extra<<8
+	} else if insertlen < 6210 {
+		var extra uint32 = insertlen - 2114
+		(*commands)[0] = 21 | extra<<8
+	} else if insertlen < 22594 {
+		var extra uint32 = insertlen - 6210
+		(*commands)[0] = 22 | extra<<8
+	} else {
+		var extra uint32 = insertlen - 22594
+		(*commands)[0] = 23 | extra<<8
+	}
+
+	*commands = (*commands)[1:]
+}
+
+func emitCopyLen(copylen uint, commands *[]uint32) {
+	if copylen < 10 {
+		(*commands)[0] = uint32(copylen + 38)
+	} else if copylen < 134 {
+		var tail uint = copylen - 6
+		var nbits uint = uint(log2FloorNonZero(tail) - 1)
+		var prefix uint = tail >> nbits
+		var code uint = (nbits << 1) + prefix + 44
+		var extra uint = tail - (prefix << nbits)
+		(*commands)[0] = uint32(code | extra<<8)
+	} else if copylen < 2118 {
+		var tail uint = copylen - 70
+		var nbits uint = uint(log2FloorNonZero(tail))
+		var code uint = nbits + 52
+		var extra uint = tail - (uint(1) << nbits)
+		(*commands)[0] = uint32(code | extra<<8)
+	} else {
+		var extra uint = copylen - 2118
+		(*commands)[0] = uint32(63 | extra<<8)
+	}
+
+	*commands = (*commands)[1:]
+}
+
+func emitCopyLenLastDistance(copylen uint, commands *[]uint32) {
+	if copylen < 12 {
+		(*commands)[0] = uint32(copylen + 20)
+		*commands = (*commands)[1:]
+	} else if copylen < 72 {
+		var tail uint = copylen - 8
+		var nbits uint = uint(log2FloorNonZero(tail) - 1)
+		var prefix uint = tail >> nbits
+		var code uint = (nbits << 1) + prefix + 28
+		var extra uint = tail - (prefix << nbits)
+		(*commands)[0] = uint32(code | extra<<8)
+		*commands = (*commands)[1:]
+	} else if copylen < 136 {
+		var tail uint = copylen - 8
+		var code uint = (tail >> 5) + 54
+		var extra uint = tail & 31
+		(*commands)[0] = uint32(code | extra<<8)
+		*commands = (*commands)[1:]
+		(*commands)[0] = 64
+		*commands = (*commands)[1:]
+	} else if copylen < 2120 {
+		var tail uint = copylen - 72
+		var nbits uint = uint(log2FloorNonZero(tail))
+		var code uint = nbits + 52
+		var extra uint = tail - (uint(1) << nbits)
+		(*commands)[0] = uint32(code | extra<<8)
+		*commands = (*commands)[1:]
+		(*commands)[0] = 64
+		*commands = (*commands)[1:]
+	} else {
+		var extra uint = copylen - 2120
+		(*commands)[0] = uint32(63 | extra<<8)
+		*commands = (*commands)[1:]
+		(*commands)[0] = 64
+		*commands = (*commands)[1:]
+	}
+}
+
+func emitDistance(distance uint32, commands *[]uint32) {
+	var d uint32 = distance + 3
+	var nbits uint32 = log2FloorNonZero(uint(d)) - 1
+	var prefix uint32 = (d >> nbits) & 1
+	var offset uint32 = (2 + prefix) << nbits
+	var distcode uint32 = 2*(nbits-1) + prefix + 80
+	var extra uint32 = d - offset
+	(*commands)[0] = distcode | extra<<8
+	*commands = (*commands)[1:]
+}
+
+/* REQUIRES: len <= 1 << 24. */
+func storeMetaBlockHeader(len uint, is_uncompressed bool, storage_ix *uint, storage []byte) {
+	var nibbles uint = 6
+
+	/* ISLAST */
+	writeBits(1, 0, storage_ix, storage)
+
+	if len <= 1<<16 {
+		nibbles = 4
+	} else if len <= 1<<20 {
+		nibbles = 5
+	}
+
+	writeBits(2, uint64(nibbles)-4, storage_ix, storage)
+	writeBits(nibbles*4, uint64(len)-1, storage_ix, storage)
+
+	/* ISUNCOMPRESSED */
+	writeSingleBit(is_uncompressed, storage_ix, storage)
+}
+
+func createCommands(input []byte, block_size uint, input_size uint, base_ip_ptr []byte, table []int, table_bits uint, min_match uint, literals *[]byte, commands *[]uint32) {
+	var ip int = 0
+	var shift uint = 64 - table_bits
+	var ip_end int = int(block_size)
+	var base_ip int = -cap(base_ip_ptr) + cap(input)
+	var next_emit int = 0
+	var last_distance int = -1
+	/* "ip" is the input pointer. */
+
+	const kInputMarginBytes uint = windowGap
+
+	/* "next_emit" is a pointer to the first byte that is not covered by a
+	   previous copy. Bytes between "next_emit" and the start of the next copy or
+	   the end of the input will be emitted as literal bytes. */
+	if block_size >= kInputMarginBytes {
+		var len_limit uint = brotli_min_size_t(block_size-min_match, input_size-kInputMarginBytes)
+		var ip_limit int = int(len_limit)
+		/* For the last block, we need to keep a 16 bytes margin so that we can be
+		   sure that all distances are at most window size - 16.
+		   For all other blocks, we only need to keep a margin of 5 bytes so that
+		   we don't go over the block size with a copy. */
+
+		var next_hash uint32
+		ip++
+		for next_hash = hash1(input[ip:], shift, min_match); ; {
+			var skip uint32 = 32
+			var next_ip int = ip
+			/* Step 1: Scan forward in the input looking for a 6-byte-long match.
+			   If we get close to exhausting the input then goto emit_remainder.
+
+			   Heuristic match skipping: If 32 bytes are scanned with no matches
+			   found, start looking only at every other byte. If 32 more bytes are
+			   scanned, look at every third byte, etc.. When a match is found,
+			   immediately go back to looking at every byte. This is a small loss
+			   (~5% performance, ~0.1% density) for compressible data due to more
+			   bookkeeping, but for non-compressible data (such as JPEG) it's a huge
+			   win since the compressor quickly "realizes" the data is incompressible
+			   and doesn't bother looking for matches everywhere.
+
+			   The "skip" variable keeps track of how many bytes there are since the
+			   last match; dividing it by 32 (ie. right-shifting by five) gives the
+			   number of bytes to move ahead for each iteration. */
+
+			var candidate int
+
+			assert(next_emit < ip)
+
+		trawl:
+			for {
+				var hash uint32 = next_hash
+				var bytes_between_hash_lookups uint32 = skip >> 5
+				skip++
+				ip = next_ip
+				assert(hash == hash1(input[ip:], shift, min_match))
+				next_ip = int(uint32(ip) + bytes_between_hash_lookups)
+				if next_ip > ip_limit {
+					goto emit_remainder
+				}
+
+				next_hash = hash1(input[next_ip:], shift, min_match)
+				candidate = ip - last_distance
+				if isMatch1(input[ip:], base_ip_ptr[candidate-base_ip:], min_match) {
+					if candidate < ip {
+						table[hash] = int(ip - base_ip)
+						break
+					}
+				}
+
+				candidate = base_ip + table[hash]
+				assert(candidate >= base_ip)
+				assert(candidate < ip)
+
+				table[hash] = int(ip - base_ip)
+				if isMatch1(input[ip:], base_ip_ptr[candidate-base_ip:], min_match) {
+					break
+				}
+			}
+
+			/* Check copy distance. If candidate is not feasible, continue search.
+			   Checking is done outside of hot loop to reduce overhead. */
+			if ip-candidate > maxDistance_compress_fragment {
+				goto trawl
+			}
+
+			/* Step 2: Emit the found match together with the literal bytes from
+			   "next_emit", and then see if we can find a next match immediately
+			   afterwards. Repeat until we find no match for the input
+			   without emitting some literal bytes. */
+			{
+				var base int = ip
+				/* > 0 */
+				var matched uint = min_match + findMatchLengthWithLimit(base_ip_ptr[uint(candidate-base_ip)+min_match:], input[uint(ip)+min_match:], uint(ip_end-ip)-min_match)
+				var distance int = int(base - candidate)
+				/* We have a 6-byte match at ip, and we need to emit bytes in
+				   [next_emit, ip). */
+
+				var insert int = int(base - next_emit)
+				ip += int(matched)
+				emitInsertLen(uint32(insert), commands)
+				copy(*literals, input[next_emit:][:uint(insert)])
+				*literals = (*literals)[insert:]
+				if distance == last_distance {
+					(*commands)[0] = 64
+					*commands = (*commands)[1:]
+				} else {
+					emitDistance(uint32(distance), commands)
+					last_distance = distance
+				}
+
+				emitCopyLenLastDistance(matched, commands)
+
+				next_emit = ip
+				if ip >= ip_limit {
+					goto emit_remainder
+				}
+				{
+					var input_bytes uint64
+					var cur_hash uint32
+					/* We could immediately start working at ip now, but to improve
+					   compression we first update "table" with the hashes of some
+					   positions within the last copy. */
+
+					var prev_hash uint32
+					if min_match == 4 {
+						input_bytes = binary.LittleEndian.Uint64(input[ip-3:])
+						cur_hash = hashBytesAtOffset(input_bytes, 3, shift, min_match)
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 3)
+						prev_hash = hashBytesAtOffset(input_bytes, 1, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 2)
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 1)
+					} else {
+						input_bytes = binary.LittleEndian.Uint64(input[ip-5:])
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 5)
+						prev_hash = hashBytesAtOffset(input_bytes, 1, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 4)
+						prev_hash = hashBytesAtOffset(input_bytes, 2, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 3)
+						input_bytes = binary.LittleEndian.Uint64(input[ip-2:])
+						cur_hash = hashBytesAtOffset(input_bytes, 2, shift, min_match)
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 2)
+						prev_hash = hashBytesAtOffset(input_bytes, 1, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 1)
+					}
+
+					candidate = base_ip + table[cur_hash]
+					table[cur_hash] = int(ip - base_ip)
+				}
+			}
+
+			for ip-candidate <= maxDistance_compress_fragment && isMatch1(input[ip:], base_ip_ptr[candidate-base_ip:], min_match) {
+				var base int = ip
+				/* We have a 6-byte match at ip, and no need to emit any
+				   literal bytes prior to ip. */
+
+				var matched uint = min_match + findMatchLengthWithLimit(base_ip_ptr[uint(candidate-base_ip)+min_match:], input[uint(ip)+min_match:], uint(ip_end-ip)-min_match)
+				ip += int(matched)
+				last_distance = int(base - candidate) /* > 0 */
+				emitCopyLen(matched, commands)
+				emitDistance(uint32(last_distance), commands)
+
+				next_emit = ip
+				if ip >= ip_limit {
+					goto emit_remainder
+				}
+				{
+					var input_bytes uint64
+					var cur_hash uint32
+					/* We could immediately start working at ip now, but to improve
+					   compression we first update "table" with the hashes of some
+					   positions within the last copy. */
+
+					var prev_hash uint32
+					if min_match == 4 {
+						input_bytes = binary.LittleEndian.Uint64(input[ip-3:])
+						cur_hash = hashBytesAtOffset(input_bytes, 3, shift, min_match)
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 3)
+						prev_hash = hashBytesAtOffset(input_bytes, 1, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 2)
+						prev_hash = hashBytesAtOffset(input_bytes, 2, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 1)
+					} else {
+						input_bytes = binary.LittleEndian.Uint64(input[ip-5:])
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 5)
+						prev_hash = hashBytesAtOffset(input_bytes, 1, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 4)
+						prev_hash = hashBytesAtOffset(input_bytes, 2, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 3)
+						input_bytes = binary.LittleEndian.Uint64(input[ip-2:])
+						cur_hash = hashBytesAtOffset(input_bytes, 2, shift, min_match)
+						prev_hash = hashBytesAtOffset(input_bytes, 0, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 2)
+						prev_hash = hashBytesAtOffset(input_bytes, 1, shift, min_match)
+						table[prev_hash] = int(ip - base_ip - 1)
+					}
+
+					candidate = base_ip + table[cur_hash]
+					table[cur_hash] = int(ip - base_ip)
+				}
+			}
+
+			ip++
+			next_hash = hash1(input[ip:], shift, min_match)
+		}
+	}
+
+emit_remainder:
+	assert(next_emit <= ip_end)
+
+	/* Emit the remaining bytes as literals. */
+	if next_emit < ip_end {
+		var insert uint32 = uint32(ip_end - next_emit)
+		emitInsertLen(insert, commands)
+		copy(*literals, input[next_emit:][:insert])
+		*literals = (*literals)[insert:]
+	}
+}
+
+var storeCommands_kNumExtraBits = [128]uint32{
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	2,
+	2,
+	3,
+	3,
+	4,
+	4,
+	5,
+	5,
+	6,
+	7,
+	8,
+	9,
+	10,
+	12,
+	14,
+	24,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	2,
+	2,
+	3,
+	3,
+	4,
+	4,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	2,
+	2,
+	3,
+	3,
+	4,
+	4,
+	5,
+	5,
+	6,
+	7,
+	8,
+	9,
+	10,
+	24,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	0,
+	1,
+	1,
+	2,
+	2,
+	3,
+	3,
+	4,
+	4,
+	5,
+	5,
+	6,
+	6,
+	7,
+	7,
+	8,
+	8,
+	9,
+	9,
+	10,
+	10,
+	11,
+	11,
+	12,
+	12,
+	13,
+	13,
+	14,
+	14,
+	15,
+	15,
+	16,
+	16,
+	17,
+	17,
+	18,
+	18,
+	19,
+	19,
+	20,
+	20,
+	21,
+	21,
+	22,
+	22,
+	23,
+	23,
+	24,
+	24,
+}
+var storeCommands_kInsertOffset = [24]uint32{
+	0,
+	1,
+	2,
+	3,
+	4,
+	5,
+	6,
+	8,
+	10,
+	14,
+	18,
+	26,
+	34,
+	50,
+	66,
+	98,
+	130,
+	194,
+	322,
+	578,
+	1090,
+	2114,
+	6210,
+	22594,
+}
+
+func storeCommands(literals []byte, num_literals uint, commands []uint32, num_commands uint, storage_ix *uint, storage []byte) {
+	var lit_depths [256]byte
+	var lit_bits [256]uint16
+	var lit_histo = [256]uint32{0}
+	var cmd_depths = [128]byte{0}
+	var cmd_bits = [128]uint16{0}
+	var cmd_histo = [128]uint32{0}
+	var i uint
+	for i = 0; i < num_literals; i++ {
+		lit_histo[literals[i]]++
+	}
+
+	buildAndStoreHuffmanTreeFast(lit_histo[:], num_literals, /* max_bits = */
+		8, lit_depths[:], lit_bits[:], storage_ix, storage)
+
+	for i = 0; i < num_commands; i++ {
+		var code uint32 = commands[i] & 0xFF
+		assert(code < 128)
+		cmd_histo[code]++
+	}
+
+	cmd_histo[1] += 1
+	cmd_histo[2] += 1
+	cmd_histo[64] += 1
+	cmd_histo[84] += 1
+	buildAndStoreCommandPrefixCode(cmd_histo[:], cmd_depths[:], cmd_bits[:], storage_ix, storage)
+
+	for i = 0; i < num_commands; i++ {
+		var cmd uint32 = commands[i]
+		var code uint32 = cmd & 0xFF
+		var extra uint32 = cmd >> 8
+		assert(code < 128)
+		writeBits(uint(cmd_depths[code]), uint64(cmd_bits[code]), storage_ix, storage)
+		writeBits(uint(storeCommands_kNumExtraBits[code]), uint64(extra), storage_ix, storage)
+		if code < 24 {
+			var insert uint32 = storeCommands_kInsertOffset[code] + extra
+			var j uint32
+			for j = 0; j < insert; j++ {
+				var lit byte = literals[0]
+				writeBits(uint(lit_depths[lit]), uint64(lit_bits[lit]), storage_ix, storage)
+				literals = literals[1:]
+			}
+		}
+	}
+}
+
+/* Acceptable loss for uncompressible speedup is 2% */
+const minRatio = 0.98
+
+const sampleRate = 43
+
+func shouldCompress(input []byte, input_size uint, num_literals uint) bool {
+	var corpus_size float64 = float64(input_size)
+	if float64(num_literals) < minRatio*corpus_size {
+		return true
+	} else {
+		var literal_histo = [256]uint32{0}
+		var max_total_bit_cost float64 = corpus_size * 8 * minRatio / sampleRate
+		var i uint
+		for i = 0; i < input_size; i += sampleRate {
+			literal_histo[input[i]]++
+		}
+
+		return bitsEntropy(literal_histo[:], 256) < max_total_bit_cost
+	}
+}
+
+func rewindBitPosition(new_storage_ix uint, storage_ix *uint, storage []byte) {
+	var bitpos uint = new_storage_ix & 7
+	var mask uint = (1 << bitpos) - 1
+	storage[new_storage_ix>>3] &= byte(mask)
+	*storage_ix = new_storage_ix
+}
+
+func emitUncompressedMetaBlock(input []byte, input_size uint, storage_ix *uint, storage []byte) {
+	storeMetaBlockHeader(input_size, true, storage_ix, storage)
+	*storage_ix = (*storage_ix + 7) &^ 7
+	copy(storage[*storage_ix>>3:], input[:input_size])
+	*storage_ix += input_size << 3
+	storage[*storage_ix>>3] = 0
+}
+
+func compressFragmentTwoPassImpl(input []byte, input_size uint, is_last bool, command_buf []uint32, literal_buf []byte, table []int, table_bits uint, min_match uint, storage_ix *uint, storage []byte) {
+	/* Save the start of the first block for position and distance computations.
+	 */
+	var base_ip []byte = input
+
+	for input_size > 0 {
+		var block_size uint = brotli_min_size_t(input_size, kCompressFragmentTwoPassBlockSize)
+		var commands []uint32 = command_buf
+		var literals []byte = literal_buf
+		var num_literals uint
+		createCommands(input, block_size, input_size, base_ip, table, table_bits, min_match, &literals, &commands)
+		num_literals = uint(-cap(literals) + cap(literal_buf))
+		if shouldCompress(input, block_size, num_literals) {
+			var num_commands uint = uint(-cap(commands) + cap(command_buf))
+			storeMetaBlockHeader(block_size, false, storage_ix, storage)
+
+			/* No block splits, no contexts. */
+			writeBits(13, 0, storage_ix, storage)
+
+			storeCommands(literal_buf, num_literals, command_buf, num_commands, storage_ix, storage)
+		} else {
+			/* Since we did not find many backward references and the entropy of
+			   the data is close to 8 bits, we can simply emit an uncompressed block.
+			   This makes compression speed of uncompressible data about 3x faster. */
+			emitUncompressedMetaBlock(input, block_size, storage_ix, storage)
+		}
+
+		input = input[block_size:]
+		input_size -= block_size
+	}
+}
+
+/* Compresses "input" string to the "*storage" buffer as one or more complete
+   meta-blocks, and updates the "*storage_ix" bit position.
+
+   If "is_last" is 1, emits an additional empty last meta-block.
+
+   REQUIRES: "input_size" is greater than zero, or "is_last" is 1.
+   REQUIRES: "input_size" is less or equal to maximal metablock size (1 << 24).
+   REQUIRES: "command_buf" and "literal_buf" point to at least
+              kCompressFragmentTwoPassBlockSize long arrays.
+   REQUIRES: All elements in "table[0..table_size-1]" are initialized to zero.
+   REQUIRES: "table_size" is a power of two
+   OUTPUT: maximal copy distance <= |input_size|
+   OUTPUT: maximal copy distance <= BROTLI_MAX_BACKWARD_LIMIT(18) */
+func compressFragmentTwoPass(input []byte, input_size uint, is_last bool, command_buf []uint32, literal_buf []byte, table []int, table_size uint, storage_ix *uint, storage []byte) {
+	var initial_storage_ix uint = *storage_ix
+	var table_bits uint = uint(log2FloorNonZero(table_size))
+	var min_match uint
+	if table_bits <= 15 {
+		min_match = 4
+	} else {
+		min_match = 6
+	}
+	compressFragmentTwoPassImpl(input, input_size, is_last, command_buf, literal_buf, table, table_bits, min_match, storage_ix, storage)
+
+	/* If output is larger than single uncompressed block, rewrite it. */
+	if *storage_ix-initial_storage_ix > 31+(input_size<<3) {
+		rewindBitPosition(initial_storage_ix, storage_ix, storage)
+		emitUncompressedMetaBlock(input, input_size, storage_ix, storage)
+	}
+
+	if is_last {
+		writeBits(1, 1, storage_ix, storage) /* islast */
+		writeBits(1, 1, storage_ix, storage) /* isempty */
+		*storage_ix = (*storage_ix + 7) &^ 7
+	}
+}

vendor/github.com/andybalholm/brotli/constants.go

@@ -0,0 +1,77 @@
+package brotli
+
+/* Copyright 2016 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Specification: 7.3. Encoding of the context map */
+const contextMapMaxRle = 16
+
+/* Specification: 2. Compressed representation overview */
+const maxNumberOfBlockTypes = 256
+
+/* Specification: 3.3. Alphabet sizes: insert-and-copy length */
+const numLiteralSymbols = 256
+
+const numCommandSymbols = 704
+
+const numBlockLenSymbols = 26
+
+const maxContextMapSymbols = (maxNumberOfBlockTypes + contextMapMaxRle)
+
+const maxBlockTypeSymbols = (maxNumberOfBlockTypes + 2)
+
+/* Specification: 3.5. Complex prefix codes */
+const repeatPreviousCodeLength = 16
+
+const repeatZeroCodeLength = 17
+
+const codeLengthCodes = (repeatZeroCodeLength + 1)
+
+/* "code length of 8 is repeated" */
+const initialRepeatedCodeLength = 8
+
+/* "Large Window Brotli" */
+const largeMaxDistanceBits = 62
+
+const largeMinWbits = 10
+
+const largeMaxWbits = 30
+
+/* Specification: 4. Encoding of distances */
+const numDistanceShortCodes = 16
+
+const maxNpostfix = 3
+
+const maxNdirect = 120
+
+const maxDistanceBits = 24
+
+func distanceAlphabetSize(NPOSTFIX uint, NDIRECT uint, MAXNBITS uint) uint {
+	return numDistanceShortCodes + NDIRECT + uint(MAXNBITS<<(NPOSTFIX+1))
+}
+
+/* numDistanceSymbols == 1128 */
+const numDistanceSymbols = 1128
+
+const maxDistance = 0x3FFFFFC
+
+const maxAllowedDistance = 0x7FFFFFFC
+
+/* 7.1. Context modes and context ID lookup for literals */
+/* "context IDs for literals are in the range of 0..63" */
+const literalContextBits = 6
+
+/* 7.2. Context ID for distances */
+const distanceContextBits = 2
+
+/* 9.1. Format of the Stream Header */
+/* Number of slack bytes for window size. Don't confuse
+   with BROTLI_NUM_DISTANCE_SHORT_CODES. */
+const windowGap = 16
+
+func maxBackwardLimit(W uint) uint {
+	return (uint(1) << W) - windowGap
+}

vendor/github.com/andybalholm/brotli/encoder_dict.go

@@ -0,0 +1,22 @@
+package brotli
+
+/* Dictionary data (words and transforms) for 1 possible context */
+type encoderDictionary struct {
+	words                 *dictionary
+	cutoffTransformsCount uint32
+	cutoffTransforms      uint64
+	hash_table            []uint16
+	buckets               []uint16
+	dict_words            []dictWord
+}
+
+func initEncoderDictionary(dict *encoderDictionary) {
+	dict.words = getDictionary()
+
+	dict.hash_table = kStaticDictionaryHash[:]
+	dict.buckets = kStaticDictionaryBuckets[:]
+	dict.dict_words = kStaticDictionaryWords[:]
+
+	dict.cutoffTransformsCount = kCutoffTransformsCount
+	dict.cutoffTransforms = kCutoffTransforms
+}

vendor/github.com/andybalholm/brotli/entropy_encode.go

@@ -0,0 +1,592 @@
+package brotli
+
+import "math"
+
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Entropy encoding (Huffman) utilities. */
+
+/* A node of a Huffman tree. */
+type huffmanTree struct {
+	total_count_          uint32
+	index_left_           int16
+	index_right_or_value_ int16
+}
+
+func initHuffmanTree(self *huffmanTree, count uint32, left int16, right int16) {
+	self.total_count_ = count
+	self.index_left_ = left
+	self.index_right_or_value_ = right
+}
+
+/* Input size optimized Shell sort. */
+type huffmanTreeComparator func(huffmanTree, huffmanTree) bool
+
+var sortHuffmanTreeItems_gaps = []uint{132, 57, 23, 10, 4, 1}
+
+func sortHuffmanTreeItems(items []huffmanTree, n uint, comparator huffmanTreeComparator) {
+	if n < 13 {
+		/* Insertion sort. */
+		var i uint
+		for i = 1; i < n; i++ {
+			var tmp huffmanTree = items[i]
+			var k uint = i
+			var j uint = i - 1
+			for comparator(tmp, items[j]) {
+				items[k] = items[j]
+				k = j
+				if j == 0 {
+					break
+				}
+				j--
+			}
+
+			items[k] = tmp
+		}
+
+		return
+	} else {
+		var g int
+		if n < 57 {
+			g = 2
+		} else {
+			g = 0
+		}
+		for ; g < 6; g++ {
+			var gap uint = sortHuffmanTreeItems_gaps[g]
+			var i uint
+			for i = gap; i < n; i++ {
+				var j uint = i
+				var tmp huffmanTree = items[i]
+				for ; j >= gap && comparator(tmp, items[j-gap]); j -= gap {
+					items[j] = items[j-gap]
+				}
+
+				items[j] = tmp
+			}
+		}
+	}
+}
+
+/* Returns 1 if assignment of depths succeeded, otherwise 0. */
+func setDepth(p0 int, pool []huffmanTree, depth []byte, max_depth int) bool {
+	var stack [16]int
+	var level int = 0
+	var p int = p0
+	assert(max_depth <= 15)
+	stack[0] = -1
+	for {
+		if pool[p].index_left_ >= 0 {
+			level++
+			if level > max_depth {
+				return false
+			}
+			stack[level] = int(pool[p].index_right_or_value_)
+			p = int(pool[p].index_left_)
+			continue
+		} else {
+			depth[pool[p].index_right_or_value_] = byte(level)
+		}
+
+		for level >= 0 && stack[level] == -1 {
+			level--
+		}
+		if level < 0 {
+			return true
+		}
+		p = stack[level]
+		stack[level] = -1
+	}
+}
+
+/* Sort the root nodes, least popular first. */
+func sortHuffmanTree(v0 huffmanTree, v1 huffmanTree) bool {
+	if v0.total_count_ != v1.total_count_ {
+		return v0.total_count_ < v1.total_count_
+	}
+
+	return v0.index_right_or_value_ > v1.index_right_or_value_
+}
+
+/* This function will create a Huffman tree.
+
+   The catch here is that the tree cannot be arbitrarily deep.
+   Brotli specifies a maximum depth of 15 bits for "code trees"
+   and 7 bits for "code length code trees."
+
+   count_limit is the value that is to be faked as the minimum value
+   and this minimum value is raised until the tree matches the
+   maximum length requirement.
+
+   This algorithm is not of excellent performance for very long data blocks,
+   especially when population counts are longer than 2**tree_limit, but
+   we are not planning to use this with extremely long blocks.
+
+   See http://en.wikipedia.org/wiki/Huffman_coding */
+func createHuffmanTree(data []uint32, length uint, tree_limit int, tree []huffmanTree, depth []byte) {
+	var count_limit uint32
+	var sentinel huffmanTree
+	initHuffmanTree(&sentinel, math.MaxUint32, -1, -1)
+
+	/* For block sizes below 64 kB, we never need to do a second iteration
+	   of this loop. Probably all of our block sizes will be smaller than
+	   that, so this loop is mostly of academic interest. If we actually
+	   would need this, we would be better off with the Katajainen algorithm. */
+	for count_limit = 1; ; count_limit *= 2 {
+		var n uint = 0
+		var i uint
+		var j uint
+		var k uint
+		for i = length; i != 0; {
+			i--
+			if data[i] != 0 {
+				var count uint32 = brotli_max_uint32_t(data[i], count_limit)
+				initHuffmanTree(&tree[n], count, -1, int16(i))
+				n++
+			}
+		}
+
+		if n == 1 {
+			depth[tree[0].index_right_or_value_] = 1 /* Only one element. */
+			break
+		}
+
+		sortHuffmanTreeItems(tree, n, huffmanTreeComparator(sortHuffmanTree))
+
+		/* The nodes are:
+		   [0, n): the sorted leaf nodes that we start with.
+		   [n]: we add a sentinel here.
+		   [n + 1, 2n): new parent nodes are added here, starting from
+		                (n+1). These are naturally in ascending order.
+		   [2n]: we add a sentinel at the end as well.
+		   There will be (2n+1) elements at the end. */
+		tree[n] = sentinel
+
+		tree[n+1] = sentinel
+
+		i = 0     /* Points to the next leaf node. */
+		j = n + 1 /* Points to the next non-leaf node. */
+		for k = n - 1; k != 0; k-- {
+			var left uint
+			var right uint
+			if tree[i].total_count_ <= tree[j].total_count_ {
+				left = i
+				i++
+			} else {
+				left = j
+				j++
+			}
+
+			if tree[i].total_count_ <= tree[j].total_count_ {
+				right = i
+				i++
+			} else {
+				right = j
+				j++
+			}
+			{
+				/* The sentinel node becomes the parent node. */
+				var j_end uint = 2*n - k
+				tree[j_end].total_count_ = tree[left].total_count_ + tree[right].total_count_
+				tree[j_end].index_left_ = int16(left)
+				tree[j_end].index_right_or_value_ = int16(right)
+
+				/* Add back the last sentinel node. */
+				tree[j_end+1] = sentinel
+			}
+		}
+
+		if setDepth(int(2*n-1), tree[0:], depth, tree_limit) {
+			/* We need to pack the Huffman tree in tree_limit bits. If this was not
+			   successful, add fake entities to the lowest values and retry. */
+			break
+		}
+	}
+}
+
+func reverse(v []byte, start uint, end uint) {
+	end--
+	for start < end {
+		var tmp byte = v[start]
+		v[start] = v[end]
+		v[end] = tmp
+		start++
+		end--
+	}
+}
+
+func writeHuffmanTreeRepetitions(previous_value byte, value byte, repetitions uint, tree_size *uint, tree []byte, extra_bits_data []byte) {
+	assert(repetitions > 0)
+	if previous_value != value {
+		tree[*tree_size] = value
+		extra_bits_data[*tree_size] = 0
+		(*tree_size)++
+		repetitions--
+	}
+
+	if repetitions == 7 {
+		tree[*tree_size] = value
+		extra_bits_data[*tree_size] = 0
+		(*tree_size)++
+		repetitions--
+	}
+
+	if repetitions < 3 {
+		var i uint
+		for i = 0; i < repetitions; i++ {
+			tree[*tree_size] = value
+			extra_bits_data[*tree_size] = 0
+			(*tree_size)++
+		}
+	} else {
+		var start uint = *tree_size
+		repetitions -= 3
+		for {
+			tree[*tree_size] = repeatPreviousCodeLength
+			extra_bits_data[*tree_size] = byte(repetitions & 0x3)
+			(*tree_size)++
+			repetitions >>= 2
+			if repetitions == 0 {
+				break
+			}
+
+			repetitions--
+		}
+
+		reverse(tree, start, *tree_size)
+		reverse(extra_bits_data, start, *tree_size)
+	}
+}
+
+func writeHuffmanTreeRepetitionsZeros(repetitions uint, tree_size *uint, tree []byte, extra_bits_data []byte) {
+	if repetitions == 11 {
+		tree[*tree_size] = 0
+		extra_bits_data[*tree_size] = 0
+		(*tree_size)++
+		repetitions--
+	}
+
+	if repetitions < 3 {
+		var i uint
+		for i = 0; i < repetitions; i++ {
+			tree[*tree_size] = 0
+			extra_bits_data[*tree_size] = 0
+			(*tree_size)++
+		}
+	} else {
+		var start uint = *tree_size
+		repetitions -= 3
+		for {
+			tree[*tree_size] = repeatZeroCodeLength
+			extra_bits_data[*tree_size] = byte(repetitions & 0x7)
+			(*tree_size)++
+			repetitions >>= 3
+			if repetitions == 0 {
+				break
+			}
+
+			repetitions--
+		}
+
+		reverse(tree, start, *tree_size)
+		reverse(extra_bits_data, start, *tree_size)
+	}
+}
+
+/* Change the population counts in a way that the consequent
+   Huffman tree compression, especially its RLE-part will be more
+   likely to compress this data more efficiently.
+
+   length contains the size of the histogram.
+   counts contains the population counts.
+   good_for_rle is a buffer of at least length size */
+func optimizeHuffmanCountsForRLE(length uint, counts []uint32, good_for_rle []byte) {
+	var nonzero_count uint = 0
+	var stride uint
+	var limit uint
+	var sum uint
+	var streak_limit uint = 1240
+	var i uint
+	/* Let's make the Huffman code more compatible with RLE encoding. */
+	for i = 0; i < length; i++ {
+		if counts[i] != 0 {
+			nonzero_count++
+		}
+	}
+
+	if nonzero_count < 16 {
+		return
+	}
+
+	for length != 0 && counts[length-1] == 0 {
+		length--
+	}
+
+	if length == 0 {
+		return /* All zeros. */
+	}
+
+	/* Now counts[0..length - 1] does not have trailing zeros. */
+	{
+		var nonzeros uint = 0
+		var smallest_nonzero uint32 = 1 << 30
+		for i = 0; i < length; i++ {
+			if counts[i] != 0 {
+				nonzeros++
+				if smallest_nonzero > counts[i] {
+					smallest_nonzero = counts[i]
+				}
+			}
+		}
+
+		if nonzeros < 5 {
+			/* Small histogram will model it well. */
+			return
+		}
+
+		if smallest_nonzero < 4 {
+			var zeros uint = length - nonzeros
+			if zeros < 6 {
+				for i = 1; i < length-1; i++ {
+					if counts[i-1] != 0 && counts[i] == 0 && counts[i+1] != 0 {
+						counts[i] = 1
+					}
+				}
+			}
+		}
+
+		if nonzeros < 28 {
+			return
+		}
+	}
+
+	/* 2) Let's mark all population counts that already can be encoded
+	   with an RLE code. */
+	for i := 0; i < int(length); i++ {
+		good_for_rle[i] = 0
+	}
+	{
+		var symbol uint32 = counts[0]
+		/* Let's not spoil any of the existing good RLE codes.
+		   Mark any seq of 0's that is longer as 5 as a good_for_rle.
+		   Mark any seq of non-0's that is longer as 7 as a good_for_rle. */
+
+		var step uint = 0
+		for i = 0; i <= length; i++ {
+			if i == length || counts[i] != symbol {
+				if (symbol == 0 && step >= 5) || (symbol != 0 && step >= 7) {
+					var k uint
+					for k = 0; k < step; k++ {
+						good_for_rle[i-k-1] = 1
+					}
+				}
+
+				step = 1
+				if i != length {
+					symbol = counts[i]
+				}
+			} else {
+				step++
+			}
+		}
+	}
+
+	/* 3) Let's replace those population counts that lead to more RLE codes.
+	   Math here is in 24.8 fixed point representation. */
+	stride = 0
+
+	limit = uint(256*(counts[0]+counts[1]+counts[2])/3 + 420)
+	sum = 0
+	for i = 0; i <= length; i++ {
+		if i == length || good_for_rle[i] != 0 || (i != 0 && good_for_rle[i-1] != 0) || (256*counts[i]-uint32(limit)+uint32(streak_limit)) >= uint32(2*streak_limit) {
+			if stride >= 4 || (stride >= 3 && sum == 0) {
+				var k uint
+				var count uint = (sum + stride/2) / stride
+				/* The stride must end, collapse what we have, if we have enough (4). */
+				if count == 0 {
+					count = 1
+				}
+
+				if sum == 0 {
+					/* Don't make an all zeros stride to be upgraded to ones. */
+					count = 0
+				}
+
+				for k = 0; k < stride; k++ {
+					/* We don't want to change value at counts[i],
+					   that is already belonging to the next stride. Thus - 1. */
+					counts[i-k-1] = uint32(count)
+				}
+			}
+
+			stride = 0
+			sum = 0
+			if i < length-2 {
+				/* All interesting strides have a count of at least 4, */
+				/* at least when non-zeros. */
+				limit = uint(256*(counts[i]+counts[i+1]+counts[i+2])/3 + 420)
+			} else if i < length {
+				limit = uint(256 * counts[i])
+			} else {
+				limit = 0
+			}
+		}
+
+		stride++
+		if i != length {
+			sum += uint(counts[i])
+			if stride >= 4 {
+				limit = (256*sum + stride/2) / stride
+			}
+
+			if stride == 4 {
+				limit += 120
+			}
+		}
+	}
+}
+
+func decideOverRLEUse(depth []byte, length uint, use_rle_for_non_zero *bool, use_rle_for_zero *bool) {
+	var total_reps_zero uint = 0
+	var total_reps_non_zero uint = 0
+	var count_reps_zero uint = 1
+	var count_reps_non_zero uint = 1
+	var i uint
+	for i = 0; i < length; {
+		var value byte = depth[i]
+		var reps uint = 1
+		var k uint
+		for k = i + 1; k < length && depth[k] == value; k++ {
+			reps++
+		}
+
+		if reps >= 3 && value == 0 {
+			total_reps_zero += reps
+			count_reps_zero++
+		}
+
+		if reps >= 4 && value != 0 {
+			total_reps_non_zero += reps
+			count_reps_non_zero++
+		}
+
+		i += reps
+	}
+
+	*use_rle_for_non_zero = total_reps_non_zero > count_reps_non_zero*2
+	*use_rle_for_zero = total_reps_zero > count_reps_zero*2
+}
+
+/* Write a Huffman tree from bit depths into the bit-stream representation
+   of a Huffman tree. The generated Huffman tree is to be compressed once
+   more using a Huffman tree */
+func writeHuffmanTree(depth []byte, length uint, tree_size *uint, tree []byte, extra_bits_data []byte) {
+	var previous_value byte = initialRepeatedCodeLength
+	var i uint
+	var use_rle_for_non_zero bool = false
+	var use_rle_for_zero bool = false
+	var new_length uint = length
+	/* Throw away trailing zeros. */
+	for i = 0; i < length; i++ {
+		if depth[length-i-1] == 0 {
+			new_length--
+		} else {
+			break
+		}
+	}
+
+	/* First gather statistics on if it is a good idea to do RLE. */
+	if length > 50 {
+		/* Find RLE coding for longer codes.
+		   Shorter codes seem not to benefit from RLE. */
+		decideOverRLEUse(depth, new_length, &use_rle_for_non_zero, &use_rle_for_zero)
+	}
+
+	/* Actual RLE coding. */
+	for i = 0; i < new_length; {
+		var value byte = depth[i]
+		var reps uint = 1
+		if (value != 0 && use_rle_for_non_zero) || (value == 0 && use_rle_for_zero) {
+			var k uint
+			for k = i + 1; k < new_length && depth[k] == value; k++ {
+				reps++
+			}
+		}
+
+		if value == 0 {
+			writeHuffmanTreeRepetitionsZeros(reps, tree_size, tree, extra_bits_data)
+		} else {
+			writeHuffmanTreeRepetitions(previous_value, value, reps, tree_size, tree, extra_bits_data)
+			previous_value = value
+		}
+
+		i += reps
+	}
+}
+
+var reverseBits_kLut = [16]uint{
+	0x00,
+	0x08,
+	0x04,
+	0x0C,
+	0x02,
+	0x0A,
+	0x06,
+	0x0E,
+	0x01,
+	0x09,
+	0x05,
+	0x0D,
+	0x03,
+	0x0B,
+	0x07,
+	0x0F,
+}
+
+func reverseBits(num_bits uint, bits uint16) uint16 {
+	var retval uint = reverseBits_kLut[bits&0x0F]
+	var i uint
+	for i = 4; i < num_bits; i += 4 {
+		retval <<= 4
+		bits = uint16(bits >> 4)
+		retval |= reverseBits_kLut[bits&0x0F]
+	}
+
+	retval >>= ((0 - num_bits) & 0x03)
+	return uint16(retval)
+}
+
+/* 0..15 are values for bits */
+const maxHuffmanBits = 16
+
+/* Get the actual bit values for a tree of bit depths. */
+func convertBitDepthsToSymbols(depth []byte, len uint, bits []uint16) {
+	var bl_count = [maxHuffmanBits]uint16{0}
+	var next_code [maxHuffmanBits]uint16
+	var i uint
+	/* In Brotli, all bit depths are [1..15]
+	   0 bit depth means that the symbol does not exist. */
+
+	var code int = 0
+	for i = 0; i < len; i++ {
+		bl_count[depth[i]]++
+	}
+
+	bl_count[0] = 0
+	next_code[0] = 0
+	for i = 1; i < maxHuffmanBits; i++ {
+		code = (code + int(bl_count[i-1])) << 1
+		next_code[i] = uint16(code)
+	}
+
+	for i = 0; i < len; i++ {
+		if depth[i] != 0 {
+			bits[i] = reverseBits(uint(depth[i]), next_code[depth[i]])
+			next_code[depth[i]]++
+		}
+	}
+}

vendor/github.com/andybalholm/brotli/fast_log.go

@@ -0,0 +1,290 @@
+package brotli
+
+import (
+	"math"
+	"math/bits"
+)
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Utilities for fast computation of logarithms. */
+
+func log2FloorNonZero(n uint) uint32 {
+	return uint32(bits.Len(n)) - 1
+}
+
+/* A lookup table for small values of log2(int) to be used in entropy
+   computation.
+
+   ", ".join(["%.16ff" % x for x in [0.0]+[log2(x) for x in range(1, 256)]]) */
+var kLog2Table = []float32{
+	0.0000000000000000,
+	0.0000000000000000,
+	1.0000000000000000,
+	1.5849625007211563,
+	2.0000000000000000,
+	2.3219280948873622,
+	2.5849625007211561,
+	2.8073549220576042,
+	3.0000000000000000,
+	3.1699250014423126,
+	3.3219280948873626,
+	3.4594316186372978,
+	3.5849625007211565,
+	3.7004397181410922,
+	3.8073549220576037,
+	3.9068905956085187,
+	4.0000000000000000,
+	4.0874628412503400,
+	4.1699250014423122,
+	4.2479275134435852,
+	4.3219280948873626,
+	4.3923174227787607,
+	4.4594316186372973,
+	4.5235619560570131,
+	4.5849625007211570,
+	4.6438561897747244,
+	4.7004397181410926,
+	4.7548875021634691,
+	4.8073549220576037,
+	4.8579809951275728,
+	4.9068905956085187,
+	4.9541963103868758,
+	5.0000000000000000,
+	5.0443941193584534,
+	5.0874628412503400,
+	5.1292830169449664,
+	5.1699250014423122,
+	5.2094533656289501,
+	5.2479275134435852,
+	5.2854022188622487,
+	5.3219280948873626,
+	5.3575520046180838,
+	5.3923174227787607,
+	5.4262647547020979,
+	5.4594316186372973,
+	5.4918530963296748,
+	5.5235619560570131,
+	5.5545888516776376,
+	5.5849625007211570,
+	5.6147098441152083,
+	5.6438561897747244,
+	5.6724253419714961,
+	5.7004397181410926,
+	5.7279204545631996,
+	5.7548875021634691,
+	5.7813597135246599,
+	5.8073549220576046,
+	5.8328900141647422,
+	5.8579809951275719,
+	5.8826430493618416,
+	5.9068905956085187,
+	5.9307373375628867,
+	5.9541963103868758,
+	5.9772799234999168,
+	6.0000000000000000,
+	6.0223678130284544,
+	6.0443941193584534,
+	6.0660891904577721,
+	6.0874628412503400,
+	6.1085244567781700,
+	6.1292830169449672,
+	6.1497471195046822,
+	6.1699250014423122,
+	6.1898245588800176,
+	6.2094533656289510,
+	6.2288186904958804,
+	6.2479275134435861,
+	6.2667865406949019,
+	6.2854022188622487,
+	6.3037807481771031,
+	6.3219280948873617,
+	6.3398500028846252,
+	6.3575520046180847,
+	6.3750394313469254,
+	6.3923174227787598,
+	6.4093909361377026,
+	6.4262647547020979,
+	6.4429434958487288,
+	6.4594316186372982,
+	6.4757334309663976,
+	6.4918530963296748,
+	6.5077946401986964,
+	6.5235619560570131,
+	6.5391588111080319,
+	6.5545888516776376,
+	6.5698556083309478,
+	6.5849625007211561,
+	6.5999128421871278,
+	6.6147098441152092,
+	6.6293566200796095,
+	6.6438561897747253,
+	6.6582114827517955,
+	6.6724253419714952,
+	6.6865005271832185,
+	6.7004397181410917,
+	6.7142455176661224,
+	6.7279204545631988,
+	6.7414669864011465,
+	6.7548875021634691,
+	6.7681843247769260,
+	6.7813597135246599,
+	6.7944158663501062,
+	6.8073549220576037,
+	6.8201789624151887,
+	6.8328900141647422,
+	6.8454900509443757,
+	6.8579809951275719,
+	6.8703647195834048,
+	6.8826430493618416,
+	6.8948177633079437,
+	6.9068905956085187,
+	6.9188632372745955,
+	6.9307373375628867,
+	6.9425145053392399,
+	6.9541963103868758,
+	6.9657842846620879,
+	6.9772799234999168,
+	6.9886846867721664,
+	7.0000000000000000,
+	7.0112272554232540,
+	7.0223678130284544,
+	7.0334230015374501,
+	7.0443941193584534,
+	7.0552824355011898,
+	7.0660891904577721,
+	7.0768155970508317,
+	7.0874628412503400,
+	7.0980320829605272,
+	7.1085244567781700,
+	7.1189410727235076,
+	7.1292830169449664,
+	7.1395513523987937,
+	7.1497471195046822,
+	7.1598713367783891,
+	7.1699250014423130,
+	7.1799090900149345,
+	7.1898245588800176,
+	7.1996723448363644,
+	7.2094533656289492,
+	7.2191685204621621,
+	7.2288186904958804,
+	7.2384047393250794,
+	7.2479275134435861,
+	7.2573878426926521,
+	7.2667865406949019,
+	7.2761244052742384,
+	7.2854022188622487,
+	7.2946207488916270,
+	7.3037807481771031,
+	7.3128829552843557,
+	7.3219280948873617,
+	7.3309168781146177,
+	7.3398500028846243,
+	7.3487281542310781,
+	7.3575520046180847,
+	7.3663222142458151,
+	7.3750394313469254,
+	7.3837042924740528,
+	7.3923174227787607,
+	7.4008794362821844,
+	7.4093909361377026,
+	7.4178525148858991,
+	7.4262647547020979,
+	7.4346282276367255,
+	7.4429434958487288,
+	7.4512111118323299,
+	7.4594316186372973,
+	7.4676055500829976,
+	7.4757334309663976,
+	7.4838157772642564,
+	7.4918530963296748,
+	7.4998458870832057,
+	7.5077946401986964,
+	7.5156998382840436,
+	7.5235619560570131,
+	7.5313814605163119,
+	7.5391588111080319,
+	7.5468944598876373,
+	7.5545888516776376,
+	7.5622424242210728,
+	7.5698556083309478,
+	7.5774288280357487,
+	7.5849625007211561,
+	7.5924570372680806,
+	7.5999128421871278,
+	7.6073303137496113,
+	7.6147098441152075,
+	7.6220518194563764,
+	7.6293566200796095,
+	7.6366246205436488,
+	7.6438561897747244,
+	7.6510516911789290,
+	7.6582114827517955,
+	7.6653359171851765,
+	7.6724253419714952,
+	7.6794800995054464,
+	7.6865005271832185,
+	7.6934869574993252,
+	7.7004397181410926,
+	7.7073591320808825,
+	7.7142455176661224,
+	7.7210991887071856,
+	7.7279204545631996,
+	7.7347096202258392,
+	7.7414669864011465,
+	7.7481928495894596,
+	7.7548875021634691,
+	7.7615512324444795,
+	7.7681843247769260,
+	7.7747870596011737,
+	7.7813597135246608,
+	7.7879025593914317,
+	7.7944158663501062,
+	7.8008998999203047,
+	7.8073549220576037,
+	7.8137811912170374,
+	7.8201789624151887,
+	7.8265484872909159,
+	7.8328900141647422,
+	7.8392037880969445,
+	7.8454900509443757,
+	7.8517490414160571,
+	7.8579809951275719,
+	7.8641861446542798,
+	7.8703647195834048,
+	7.8765169465650002,
+	7.8826430493618425,
+	7.8887432488982601,
+	7.8948177633079446,
+	7.9008668079807496,
+	7.9068905956085187,
+	7.9128893362299619,
+	7.9188632372745955,
+	7.9248125036057813,
+	7.9307373375628867,
+	7.9366379390025719,
+	7.9425145053392399,
+	7.9483672315846778,
+	7.9541963103868758,
+	7.9600019320680806,
+	7.9657842846620870,
+	7.9715435539507720,
+	7.9772799234999168,
+	7.9829935746943104,
+	7.9886846867721664,
+	7.9943534368588578,
+}
+
+/* Faster logarithm for small integers, with the property of log2(0) == 0. */
+func fastLog2(v uint) float64 {
+	if v < uint(len(kLog2Table)) {
+		return float64(kLog2Table[v])
+	}
+
+	return math.Log2(float64(v))
+}

vendor/github.com/andybalholm/brotli/find_match_length.go

@@ -0,0 +1,45 @@
+package brotli
+
+import (
+	"encoding/binary"
+	"math/bits"
+	"runtime"
+)
+
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Function to find maximal matching prefixes of strings. */
+func findMatchLengthWithLimit(s1 []byte, s2 []byte, limit uint) uint {
+	var matched uint = 0
+	_, _ = s1[limit-1], s2[limit-1] // bounds check
+	switch runtime.GOARCH {
+	case "amd64":
+		// Compare 8 bytes at at time.
+		for matched+8 <= limit {
+			w1 := binary.LittleEndian.Uint64(s1[matched:])
+			w2 := binary.LittleEndian.Uint64(s2[matched:])
+			if w1 != w2 {
+				return matched + uint(bits.TrailingZeros64(w1^w2)>>3)
+			}
+			matched += 8
+		}
+	case "386":
+		// Compare 4 bytes at at time.
+		for matched+4 <= limit {
+			w1 := binary.LittleEndian.Uint32(s1[matched:])
+			w2 := binary.LittleEndian.Uint32(s2[matched:])
+			if w1 != w2 {
+				return matched + uint(bits.TrailingZeros32(w1^w2)>>3)
+			}
+			matched += 4
+		}
+	}
+	for matched < limit && s1[matched] == s2[matched] {
+		matched++
+	}
+	return matched
+}

vendor/github.com/andybalholm/brotli/h10.go

@@ -0,0 +1,287 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2016 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func (*h10) HashTypeLength() uint {
+	return 4
+}
+
+func (*h10) StoreLookahead() uint {
+	return 128
+}
+
+func hashBytesH10(data []byte) uint32 {
+	var h uint32 = binary.LittleEndian.Uint32(data) * kHashMul32
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return h >> (32 - 17)
+}
+
+/* A (forgetful) hash table where each hash bucket contains a binary tree of
+   sequences whose first 4 bytes share the same hash code.
+   Each sequence is 128 long and is identified by its starting
+   position in the input data. The binary tree is sorted by the lexicographic
+   order of the sequences, and it is also a max-heap with respect to the
+   starting positions. */
+type h10 struct {
+	hasherCommon
+	window_mask_ uint
+	buckets_     [1 << 17]uint32
+	invalid_pos_ uint32
+	forest       []uint32
+}
+
+func (h *h10) Initialize(params *encoderParams) {
+	h.window_mask_ = (1 << params.lgwin) - 1
+	h.invalid_pos_ = uint32(0 - h.window_mask_)
+	var num_nodes uint = uint(1) << params.lgwin
+	h.forest = make([]uint32, 2*num_nodes)
+}
+
+func (h *h10) Prepare(one_shot bool, input_size uint, data []byte) {
+	var invalid_pos uint32 = h.invalid_pos_
+	var i uint32
+	for i = 0; i < 1<<17; i++ {
+		h.buckets_[i] = invalid_pos
+	}
+}
+
+func leftChildIndexH10(self *h10, pos uint) uint {
+	return 2 * (pos & self.window_mask_)
+}
+
+func rightChildIndexH10(self *h10, pos uint) uint {
+	return 2*(pos&self.window_mask_) + 1
+}
+
+/* Stores the hash of the next 4 bytes and in a single tree-traversal, the
+   hash bucket's binary tree is searched for matches and is re-rooted at the
+   current position.
+
+   If less than 128 data is available, the hash bucket of the
+   current position is searched for matches, but the state of the hash table
+   is not changed, since we can not know the final sorting order of the
+   current (incomplete) sequence.
+
+   This function must be called with increasing cur_ix positions. */
+func storeAndFindMatchesH10(self *h10, data []byte, cur_ix uint, ring_buffer_mask uint, max_length uint, max_backward uint, best_len *uint, matches []backwardMatch) []backwardMatch {
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var max_comp_len uint = brotli_min_size_t(max_length, 128)
+	var should_reroot_tree bool = (max_length >= 128)
+	var key uint32 = hashBytesH10(data[cur_ix_masked:])
+	var forest []uint32 = self.forest
+	var prev_ix uint = uint(self.buckets_[key])
+	var node_left uint = leftChildIndexH10(self, cur_ix)
+	var node_right uint = rightChildIndexH10(self, cur_ix)
+	var best_len_left uint = 0
+	var best_len_right uint = 0
+	var depth_remaining uint
+	/* The forest index of the rightmost node of the left subtree of the new
+	   root, updated as we traverse and re-root the tree of the hash bucket. */
+
+	/* The forest index of the leftmost node of the right subtree of the new
+	   root, updated as we traverse and re-root the tree of the hash bucket. */
+
+	/* The match length of the rightmost node of the left subtree of the new
+	   root, updated as we traverse and re-root the tree of the hash bucket. */
+
+	/* The match length of the leftmost node of the right subtree of the new
+	   root, updated as we traverse and re-root the tree of the hash bucket. */
+	if should_reroot_tree {
+		self.buckets_[key] = uint32(cur_ix)
+	}
+
+	for depth_remaining = 64; ; depth_remaining-- {
+		var backward uint = cur_ix - prev_ix
+		var prev_ix_masked uint = prev_ix & ring_buffer_mask
+		if backward == 0 || backward > max_backward || depth_remaining == 0 {
+			if should_reroot_tree {
+				forest[node_left] = self.invalid_pos_
+				forest[node_right] = self.invalid_pos_
+			}
+
+			break
+		}
+		{
+			var cur_len uint = brotli_min_size_t(best_len_left, best_len_right)
+			var len uint
+			assert(cur_len <= 128)
+			len = cur_len + findMatchLengthWithLimit(data[cur_ix_masked+cur_len:], data[prev_ix_masked+cur_len:], max_length-cur_len)
+			if matches != nil && len > *best_len {
+				*best_len = uint(len)
+				initBackwardMatch(&matches[0], backward, uint(len))
+				matches = matches[1:]
+			}
+
+			if len >= max_comp_len {
+				if should_reroot_tree {
+					forest[node_left] = forest[leftChildIndexH10(self, prev_ix)]
+					forest[node_right] = forest[rightChildIndexH10(self, prev_ix)]
+				}
+
+				break
+			}
+
+			if data[cur_ix_masked+len] > data[prev_ix_masked+len] {
+				best_len_left = uint(len)
+				if should_reroot_tree {
+					forest[node_left] = uint32(prev_ix)
+				}
+
+				node_left = rightChildIndexH10(self, prev_ix)
+				prev_ix = uint(forest[node_left])
+			} else {
+				best_len_right = uint(len)
+				if should_reroot_tree {
+					forest[node_right] = uint32(prev_ix)
+				}
+
+				node_right = leftChildIndexH10(self, prev_ix)
+				prev_ix = uint(forest[node_right])
+			}
+		}
+	}
+
+	return matches
+}
+
+/* Finds all backward matches of &data[cur_ix & ring_buffer_mask] up to the
+   length of max_length and stores the position cur_ix in the hash table.
+
+   Sets *num_matches to the number of matches found, and stores the found
+   matches in matches[0] to matches[*num_matches - 1]. The matches will be
+   sorted by strictly increasing length and (non-strictly) increasing
+   distance. */
+func findAllMatchesH10(handle *h10, dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, cur_ix uint, max_length uint, max_backward uint, gap uint, params *encoderParams, matches []backwardMatch) uint {
+	var orig_matches []backwardMatch = matches
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var best_len uint = 1
+	var short_match_max_backward uint
+	if params.quality != hqZopflificationQuality {
+		short_match_max_backward = 16
+	} else {
+		short_match_max_backward = 64
+	}
+	var stop uint = cur_ix - short_match_max_backward
+	var dict_matches [maxStaticDictionaryMatchLen + 1]uint32
+	var i uint
+	if cur_ix < short_match_max_backward {
+		stop = 0
+	}
+	for i = cur_ix - 1; i > stop && best_len <= 2; i-- {
+		var prev_ix uint = i
+		var backward uint = cur_ix - prev_ix
+		if backward > max_backward {
+			break
+		}
+
+		prev_ix &= ring_buffer_mask
+		if data[cur_ix_masked] != data[prev_ix] || data[cur_ix_masked+1] != data[prev_ix+1] {
+			continue
+		}
+		{
+			var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+			if len > best_len {
+				best_len = uint(len)
+				initBackwardMatch(&matches[0], backward, uint(len))
+				matches = matches[1:]
+			}
+		}
+	}
+
+	if best_len < max_length {
+		matches = storeAndFindMatchesH10(handle, data, cur_ix, ring_buffer_mask, max_length, max_backward, &best_len, matches)
+	}
+
+	for i = 0; i <= maxStaticDictionaryMatchLen; i++ {
+		dict_matches[i] = kInvalidMatch
+	}
+	{
+		var minlen uint = brotli_max_size_t(4, best_len+1)
+		if findAllStaticDictionaryMatches(dictionary, data[cur_ix_masked:], minlen, max_length, dict_matches[0:]) {
+			var maxlen uint = brotli_min_size_t(maxStaticDictionaryMatchLen, max_length)
+			var l uint
+			for l = minlen; l <= maxlen; l++ {
+				var dict_id uint32 = dict_matches[l]
+				if dict_id < kInvalidMatch {
+					var distance uint = max_backward + gap + uint(dict_id>>5) + 1
+					if distance <= params.dist.max_distance {
+						initDictionaryBackwardMatch(&matches[0], distance, l, uint(dict_id&31))
+						matches = matches[1:]
+					}
+				}
+			}
+		}
+	}
+
+	return uint(-cap(matches) + cap(orig_matches))
+}
+
+/* Stores the hash of the next 4 bytes and re-roots the binary tree at the
+   current sequence, without returning any matches.
+   REQUIRES: ix + 128 <= end-of-current-block */
+func (h *h10) Store(data []byte, mask uint, ix uint) {
+	var max_backward uint = h.window_mask_ - windowGap + 1
+	/* Maximum distance is window size - 16, see section 9.1. of the spec. */
+	storeAndFindMatchesH10(h, data, ix, mask, 128, max_backward, nil, nil)
+}
+
+func (h *h10) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+	var i uint = ix_start
+	var j uint = ix_start
+	if ix_start+63 <= ix_end {
+		i = ix_end - 63
+	}
+
+	if ix_start+512 <= i {
+		for ; j < i; j += 8 {
+			h.Store(data, mask, j)
+		}
+	}
+
+	for ; i < ix_end; i++ {
+		h.Store(data, mask, i)
+	}
+}
+
+func (h *h10) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint) {
+	if num_bytes >= h.HashTypeLength()-1 && position >= 128 {
+		var i_start uint = position - 128 + 1
+		var i_end uint = brotli_min_size_t(position, i_start+num_bytes)
+		/* Store the last `128 - 1` positions in the hasher.
+		   These could not be calculated before, since they require knowledge
+		   of both the previous and the current block. */
+
+		var i uint
+		for i = i_start; i < i_end; i++ {
+			/* Maximum distance is window size - 16, see section 9.1. of the spec.
+			   Furthermore, we have to make sure that we don't look further back
+			   from the start of the next block than the window size, otherwise we
+			   could access already overwritten areas of the ring-buffer. */
+			var max_backward uint = h.window_mask_ - brotli_max_size_t(windowGap-1, position-i)
+
+			/* We know that i + 128 <= position + num_bytes, i.e. the
+			   end of the current block and that we have at least
+			   128 tail in the ring-buffer. */
+			storeAndFindMatchesH10(h, ringbuffer, i, ringbuffer_mask, 128, max_backward, nil, nil)
+		}
+	}
+}
+
+/* MAX_NUM_MATCHES == 64 + MAX_TREE_SEARCH_DEPTH */
+const maxNumMatchesH10 = 128
+
+func (*h10) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	panic("unimplemented")
+}
+
+func (*h10) PrepareDistanceCache(distance_cache []int) {
+	panic("unimplemented")
+}

vendor/github.com/andybalholm/brotli/h5.go

@@ -0,0 +1,214 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* A (forgetful) hash table to the data seen by the compressor, to
+   help create backward references to previous data.
+
+   This is a hash map of fixed size (bucket_size_) to a ring buffer of
+   fixed size (block_size_). The ring buffer contains the last block_size_
+   index positions of the given hash key in the compressed data. */
+func (*h5) HashTypeLength() uint {
+	return 4
+}
+
+func (*h5) StoreLookahead() uint {
+	return 4
+}
+
+/* HashBytes is the function that chooses the bucket to place the address in. */
+func hashBytesH5(data []byte, shift int) uint32 {
+	var h uint32 = binary.LittleEndian.Uint32(data) * kHashMul32
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return uint32(h >> uint(shift))
+}
+
+type h5 struct {
+	hasherCommon
+	bucket_size_ uint
+	block_size_  uint
+	hash_shift_  int
+	block_mask_  uint32
+	num          []uint16
+	buckets      []uint32
+}
+
+func (h *h5) Initialize(params *encoderParams) {
+	h.hash_shift_ = 32 - h.params.bucket_bits
+	h.bucket_size_ = uint(1) << uint(h.params.bucket_bits)
+	h.block_size_ = uint(1) << uint(h.params.block_bits)
+	h.block_mask_ = uint32(h.block_size_ - 1)
+	h.num = make([]uint16, h.bucket_size_)
+	h.buckets = make([]uint32, h.block_size_*h.bucket_size_)
+}
+
+func (h *h5) Prepare(one_shot bool, input_size uint, data []byte) {
+	var num []uint16 = h.num
+	var partial_prepare_threshold uint = h.bucket_size_ >> 6
+	/* Partial preparation is 100 times slower (per socket). */
+	if one_shot && input_size <= partial_prepare_threshold {
+		var i uint
+		for i = 0; i < input_size; i++ {
+			var key uint32 = hashBytesH5(data[i:], h.hash_shift_)
+			num[key] = 0
+		}
+	} else {
+		for i := 0; i < int(h.bucket_size_); i++ {
+			num[i] = 0
+		}
+	}
+}
+
+/* Look at 4 bytes at &data[ix & mask].
+   Compute a hash from these, and store the value of ix at that position. */
+func (h *h5) Store(data []byte, mask uint, ix uint) {
+	var num []uint16 = h.num
+	var key uint32 = hashBytesH5(data[ix&mask:], h.hash_shift_)
+	var minor_ix uint = uint(num[key]) & uint(h.block_mask_)
+	var offset uint = minor_ix + uint(key<<uint(h.params.block_bits))
+	h.buckets[offset] = uint32(ix)
+	num[key]++
+}
+
+func (h *h5) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+	var i uint
+	for i = ix_start; i < ix_end; i++ {
+		h.Store(data, mask, i)
+	}
+}
+
+func (h *h5) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint) {
+	if num_bytes >= h.HashTypeLength()-1 && position >= 3 {
+		/* Prepare the hashes for three last bytes of the last write.
+		   These could not be calculated before, since they require knowledge
+		   of both the previous and the current block. */
+		h.Store(ringbuffer, ringbuffer_mask, position-3)
+		h.Store(ringbuffer, ringbuffer_mask, position-2)
+		h.Store(ringbuffer, ringbuffer_mask, position-1)
+	}
+}
+
+func (h *h5) PrepareDistanceCache(distance_cache []int) {
+	prepareDistanceCache(distance_cache, h.params.num_last_distances_to_check)
+}
+
+/* Find a longest backward match of &data[cur_ix] up to the length of
+   max_length and stores the position cur_ix in the hash table.
+
+   REQUIRES: PrepareDistanceCacheH5 must be invoked for current distance cache
+             values; if this method is invoked repeatedly with the same distance
+             cache values, it is enough to invoke PrepareDistanceCacheH5 once.
+
+   Does not look for matches longer than max_length.
+   Does not look for matches further away than max_backward.
+   Writes the best match into |out|.
+   |out|->score is updated only if a better match is found. */
+func (h *h5) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	var num []uint16 = h.num
+	var buckets []uint32 = h.buckets
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var min_score uint = out.score
+	var best_score uint = out.score
+	var best_len uint = out.len
+	var i uint
+	var bucket []uint32
+	/* Don't accept a short copy from far away. */
+	out.len = 0
+
+	out.len_code_delta = 0
+
+	/* Try last distance first. */
+	for i = 0; i < uint(h.params.num_last_distances_to_check); i++ {
+		var backward uint = uint(distance_cache[i])
+		var prev_ix uint = uint(cur_ix - backward)
+		if prev_ix >= cur_ix {
+			continue
+		}
+
+		if backward > max_backward {
+			continue
+		}
+
+		prev_ix &= ring_buffer_mask
+
+		if cur_ix_masked+best_len > ring_buffer_mask || prev_ix+best_len > ring_buffer_mask || data[cur_ix_masked+best_len] != data[prev_ix+best_len] {
+			continue
+		}
+		{
+			var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+			if len >= 3 || (len == 2 && i < 2) {
+				/* Comparing for >= 2 does not change the semantics, but just saves for
+				   a few unnecessary binary logarithms in backward reference score,
+				   since we are not interested in such short matches. */
+				var score uint = backwardReferenceScoreUsingLastDistance(uint(len))
+				if best_score < score {
+					if i != 0 {
+						score -= backwardReferencePenaltyUsingLastDistance(i)
+					}
+					if best_score < score {
+						best_score = score
+						best_len = uint(len)
+						out.len = best_len
+						out.distance = backward
+						out.score = best_score
+					}
+				}
+			}
+		}
+	}
+	{
+		var key uint32 = hashBytesH5(data[cur_ix_masked:], h.hash_shift_)
+		bucket = buckets[key<<uint(h.params.block_bits):]
+		var down uint
+		if uint(num[key]) > h.block_size_ {
+			down = uint(num[key]) - h.block_size_
+		} else {
+			down = 0
+		}
+		for i = uint(num[key]); i > down; {
+			var prev_ix uint
+			i--
+			prev_ix = uint(bucket[uint32(i)&h.block_mask_])
+			var backward uint = cur_ix - prev_ix
+			if backward > max_backward {
+				break
+			}
+
+			prev_ix &= ring_buffer_mask
+			if cur_ix_masked+best_len > ring_buffer_mask || prev_ix+best_len > ring_buffer_mask || data[cur_ix_masked+best_len] != data[prev_ix+best_len] {
+				continue
+			}
+			{
+				var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+				if len >= 4 {
+					/* Comparing for >= 3 does not change the semantics, but just saves
+					   for a few unnecessary binary logarithms in backward reference
+					   score, since we are not interested in such short matches. */
+					var score uint = backwardReferenceScore(uint(len), backward)
+					if best_score < score {
+						best_score = score
+						best_len = uint(len)
+						out.len = best_len
+						out.distance = backward
+						out.score = best_score
+					}
+				}
+			}
+		}
+
+		bucket[uint32(num[key])&h.block_mask_] = uint32(cur_ix)
+		num[key]++
+	}
+
+	if min_score == out.score {
+		searchInStaticDictionary(dictionary, h, data[cur_ix_masked:], max_length, max_backward+gap, max_distance, out, false)
+	}
+}

vendor/github.com/andybalholm/brotli/h6.go

@@ -0,0 +1,216 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* A (forgetful) hash table to the data seen by the compressor, to
+   help create backward references to previous data.
+
+   This is a hash map of fixed size (bucket_size_) to a ring buffer of
+   fixed size (block_size_). The ring buffer contains the last block_size_
+   index positions of the given hash key in the compressed data. */
+func (*h6) HashTypeLength() uint {
+	return 8
+}
+
+func (*h6) StoreLookahead() uint {
+	return 8
+}
+
+/* HashBytes is the function that chooses the bucket to place the address in. */
+func hashBytesH6(data []byte, mask uint64, shift int) uint32 {
+	var h uint64 = (binary.LittleEndian.Uint64(data) & mask) * kHashMul64Long
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return uint32(h >> uint(shift))
+}
+
+type h6 struct {
+	hasherCommon
+	bucket_size_ uint
+	block_size_  uint
+	hash_shift_  int
+	hash_mask_   uint64
+	block_mask_  uint32
+	num          []uint16
+	buckets      []uint32
+}
+
+func (h *h6) Initialize(params *encoderParams) {
+	h.hash_shift_ = 64 - h.params.bucket_bits
+	h.hash_mask_ = (^(uint64(0))) >> uint(64-8*h.params.hash_len)
+	h.bucket_size_ = uint(1) << uint(h.params.bucket_bits)
+	h.block_size_ = uint(1) << uint(h.params.block_bits)
+	h.block_mask_ = uint32(h.block_size_ - 1)
+	h.num = make([]uint16, h.bucket_size_)
+	h.buckets = make([]uint32, h.block_size_*h.bucket_size_)
+}
+
+func (h *h6) Prepare(one_shot bool, input_size uint, data []byte) {
+	var num []uint16 = h.num
+	var partial_prepare_threshold uint = h.bucket_size_ >> 6
+	/* Partial preparation is 100 times slower (per socket). */
+	if one_shot && input_size <= partial_prepare_threshold {
+		var i uint
+		for i = 0; i < input_size; i++ {
+			var key uint32 = hashBytesH6(data[i:], h.hash_mask_, h.hash_shift_)
+			num[key] = 0
+		}
+	} else {
+		for i := 0; i < int(h.bucket_size_); i++ {
+			num[i] = 0
+		}
+	}
+}
+
+/* Look at 4 bytes at &data[ix & mask].
+   Compute a hash from these, and store the value of ix at that position. */
+func (h *h6) Store(data []byte, mask uint, ix uint) {
+	var num []uint16 = h.num
+	var key uint32 = hashBytesH6(data[ix&mask:], h.hash_mask_, h.hash_shift_)
+	var minor_ix uint = uint(num[key]) & uint(h.block_mask_)
+	var offset uint = minor_ix + uint(key<<uint(h.params.block_bits))
+	h.buckets[offset] = uint32(ix)
+	num[key]++
+}
+
+func (h *h6) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+	var i uint
+	for i = ix_start; i < ix_end; i++ {
+		h.Store(data, mask, i)
+	}
+}
+
+func (h *h6) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint) {
+	if num_bytes >= h.HashTypeLength()-1 && position >= 3 {
+		/* Prepare the hashes for three last bytes of the last write.
+		   These could not be calculated before, since they require knowledge
+		   of both the previous and the current block. */
+		h.Store(ringbuffer, ringbuffer_mask, position-3)
+		h.Store(ringbuffer, ringbuffer_mask, position-2)
+		h.Store(ringbuffer, ringbuffer_mask, position-1)
+	}
+}
+
+func (h *h6) PrepareDistanceCache(distance_cache []int) {
+	prepareDistanceCache(distance_cache, h.params.num_last_distances_to_check)
+}
+
+/* Find a longest backward match of &data[cur_ix] up to the length of
+   max_length and stores the position cur_ix in the hash table.
+
+   REQUIRES: PrepareDistanceCacheH6 must be invoked for current distance cache
+             values; if this method is invoked repeatedly with the same distance
+             cache values, it is enough to invoke PrepareDistanceCacheH6 once.
+
+   Does not look for matches longer than max_length.
+   Does not look for matches further away than max_backward.
+   Writes the best match into |out|.
+   |out|->score is updated only if a better match is found. */
+func (h *h6) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	var num []uint16 = h.num
+	var buckets []uint32 = h.buckets
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var min_score uint = out.score
+	var best_score uint = out.score
+	var best_len uint = out.len
+	var i uint
+	var bucket []uint32
+	/* Don't accept a short copy from far away. */
+	out.len = 0
+
+	out.len_code_delta = 0
+
+	/* Try last distance first. */
+	for i = 0; i < uint(h.params.num_last_distances_to_check); i++ {
+		var backward uint = uint(distance_cache[i])
+		var prev_ix uint = uint(cur_ix - backward)
+		if prev_ix >= cur_ix {
+			continue
+		}
+
+		if backward > max_backward {
+			continue
+		}
+
+		prev_ix &= ring_buffer_mask
+
+		if cur_ix_masked+best_len > ring_buffer_mask || prev_ix+best_len > ring_buffer_mask || data[cur_ix_masked+best_len] != data[prev_ix+best_len] {
+			continue
+		}
+		{
+			var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+			if len >= 3 || (len == 2 && i < 2) {
+				/* Comparing for >= 2 does not change the semantics, but just saves for
+				   a few unnecessary binary logarithms in backward reference score,
+				   since we are not interested in such short matches. */
+				var score uint = backwardReferenceScoreUsingLastDistance(uint(len))
+				if best_score < score {
+					if i != 0 {
+						score -= backwardReferencePenaltyUsingLastDistance(i)
+					}
+					if best_score < score {
+						best_score = score
+						best_len = uint(len)
+						out.len = best_len
+						out.distance = backward
+						out.score = best_score
+					}
+				}
+			}
+		}
+	}
+	{
+		var key uint32 = hashBytesH6(data[cur_ix_masked:], h.hash_mask_, h.hash_shift_)
+		bucket = buckets[key<<uint(h.params.block_bits):]
+		var down uint
+		if uint(num[key]) > h.block_size_ {
+			down = uint(num[key]) - h.block_size_
+		} else {
+			down = 0
+		}
+		for i = uint(num[key]); i > down; {
+			var prev_ix uint
+			i--
+			prev_ix = uint(bucket[uint32(i)&h.block_mask_])
+			var backward uint = cur_ix - prev_ix
+			if backward > max_backward {
+				break
+			}
+
+			prev_ix &= ring_buffer_mask
+			if cur_ix_masked+best_len > ring_buffer_mask || prev_ix+best_len > ring_buffer_mask || data[cur_ix_masked+best_len] != data[prev_ix+best_len] {
+				continue
+			}
+			{
+				var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+				if len >= 4 {
+					/* Comparing for >= 3 does not change the semantics, but just saves
+					   for a few unnecessary binary logarithms in backward reference
+					   score, since we are not interested in such short matches. */
+					var score uint = backwardReferenceScore(uint(len), backward)
+					if best_score < score {
+						best_score = score
+						best_len = uint(len)
+						out.len = best_len
+						out.distance = backward
+						out.score = best_score
+					}
+				}
+			}
+		}
+
+		bucket[uint32(num[key])&h.block_mask_] = uint32(cur_ix)
+		num[key]++
+	}
+
+	if min_score == out.score {
+		searchInStaticDictionary(dictionary, h, data[cur_ix_masked:], max_length, max_backward+gap, max_distance, out, false)
+	}
+}

vendor/github.com/andybalholm/brotli/hash.go

@@ -0,0 +1,342 @@
+package brotli
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+type hasherCommon struct {
+	params           hasherParams
+	is_prepared_     bool
+	dict_num_lookups uint
+	dict_num_matches uint
+}
+
+func (h *hasherCommon) Common() *hasherCommon {
+	return h
+}
+
+type hasherHandle interface {
+	Common() *hasherCommon
+	Initialize(params *encoderParams)
+	Prepare(one_shot bool, input_size uint, data []byte)
+	StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint)
+	HashTypeLength() uint
+	StoreLookahead() uint
+	PrepareDistanceCache(distance_cache []int)
+	FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult)
+	StoreRange(data []byte, mask uint, ix_start uint, ix_end uint)
+	Store(data []byte, mask uint, ix uint)
+}
+
+const kCutoffTransformsCount uint32 = 10
+
+/*   0,  12,   27,    23,    42,    63,    56,    48,    59,    64 */
+/* 0+0, 4+8, 8+19, 12+11, 16+26, 20+43, 24+32, 28+20, 32+27, 36+28 */
+const kCutoffTransforms uint64 = 0x071B520ADA2D3200
+
+type hasherSearchResult struct {
+	len            uint
+	distance       uint
+	score          uint
+	len_code_delta int
+}
+
+/* kHashMul32 multiplier has these properties:
+   * The multiplier must be odd. Otherwise we may lose the highest bit.
+   * No long streaks of ones or zeros.
+   * There is no effort to ensure that it is a prime, the oddity is enough
+     for this use.
+   * The number has been tuned heuristically against compression benchmarks. */
+const kHashMul32 uint32 = 0x1E35A7BD
+
+const kHashMul64 uint64 = 0x1E35A7BD1E35A7BD
+
+const kHashMul64Long uint64 = 0x1FE35A7BD3579BD3
+
+func hash14(data []byte) uint32 {
+	var h uint32 = binary.LittleEndian.Uint32(data) * kHashMul32
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return h >> (32 - 14)
+}
+
+func prepareDistanceCache(distance_cache []int, num_distances int) {
+	if num_distances > 4 {
+		var last_distance int = distance_cache[0]
+		distance_cache[4] = last_distance - 1
+		distance_cache[5] = last_distance + 1
+		distance_cache[6] = last_distance - 2
+		distance_cache[7] = last_distance + 2
+		distance_cache[8] = last_distance - 3
+		distance_cache[9] = last_distance + 3
+		if num_distances > 10 {
+			var next_last_distance int = distance_cache[1]
+			distance_cache[10] = next_last_distance - 1
+			distance_cache[11] = next_last_distance + 1
+			distance_cache[12] = next_last_distance - 2
+			distance_cache[13] = next_last_distance + 2
+			distance_cache[14] = next_last_distance - 3
+			distance_cache[15] = next_last_distance + 3
+		}
+	}
+}
+
+const literalByteScore = 135
+
+const distanceBitPenalty = 30
+
+/* Score must be positive after applying maximal penalty. */
+const scoreBase = (distanceBitPenalty * 8 * 8)
+
+/* Usually, we always choose the longest backward reference. This function
+   allows for the exception of that rule.
+
+   If we choose a backward reference that is further away, it will
+   usually be coded with more bits. We approximate this by assuming
+   log2(distance). If the distance can be expressed in terms of the
+   last four distances, we use some heuristic constants to estimate
+   the bits cost. For the first up to four literals we use the bit
+   cost of the literals from the literal cost model, after that we
+   use the average bit cost of the cost model.
+
+   This function is used to sometimes discard a longer backward reference
+   when it is not much longer and the bit cost for encoding it is more
+   than the saved literals.
+
+   backward_reference_offset MUST be positive. */
+func backwardReferenceScore(copy_length uint, backward_reference_offset uint) uint {
+	return scoreBase + literalByteScore*uint(copy_length) - distanceBitPenalty*uint(log2FloorNonZero(backward_reference_offset))
+}
+
+func backwardReferenceScoreUsingLastDistance(copy_length uint) uint {
+	return literalByteScore*uint(copy_length) + scoreBase + 15
+}
+
+func backwardReferencePenaltyUsingLastDistance(distance_short_code uint) uint {
+	return uint(39) + ((0x1CA10 >> (distance_short_code & 0xE)) & 0xE)
+}
+
+func testStaticDictionaryItem(dictionary *encoderDictionary, item uint, data []byte, max_length uint, max_backward uint, max_distance uint, out *hasherSearchResult) bool {
+	var len uint
+	var word_idx uint
+	var offset uint
+	var matchlen uint
+	var backward uint
+	var score uint
+	len = item & 0x1F
+	word_idx = item >> 5
+	offset = uint(dictionary.words.offsets_by_length[len]) + len*word_idx
+	if len > max_length {
+		return false
+	}
+
+	matchlen = findMatchLengthWithLimit(data, dictionary.words.data[offset:], uint(len))
+	if matchlen+uint(dictionary.cutoffTransformsCount) <= len || matchlen == 0 {
+		return false
+	}
+	{
+		var cut uint = len - matchlen
+		var transform_id uint = (cut << 2) + uint((dictionary.cutoffTransforms>>(cut*6))&0x3F)
+		backward = max_backward + 1 + word_idx + (transform_id << dictionary.words.size_bits_by_length[len])
+	}
+
+	if backward > max_distance {
+		return false
+	}
+
+	score = backwardReferenceScore(matchlen, backward)
+	if score < out.score {
+		return false
+	}
+
+	out.len = matchlen
+	out.len_code_delta = int(len) - int(matchlen)
+	out.distance = backward
+	out.score = score
+	return true
+}
+
+func searchInStaticDictionary(dictionary *encoderDictionary, handle hasherHandle, data []byte, max_length uint, max_backward uint, max_distance uint, out *hasherSearchResult, shallow bool) {
+	var key uint
+	var i uint
+	var self *hasherCommon = handle.Common()
+	if self.dict_num_matches < self.dict_num_lookups>>7 {
+		return
+	}
+
+	key = uint(hash14(data) << 1)
+	for i = 0; ; (func() { i++; key++ })() {
+		var tmp uint
+		if shallow {
+			tmp = 1
+		} else {
+			tmp = 2
+		}
+		if i >= tmp {
+			break
+		}
+		var item uint = uint(dictionary.hash_table[key])
+		self.dict_num_lookups++
+		if item != 0 {
+			var item_matches bool = testStaticDictionaryItem(dictionary, item, data, max_length, max_backward, max_distance, out)
+			if item_matches {
+				self.dict_num_matches++
+			}
+		}
+	}
+}
+
+type backwardMatch struct {
+	distance        uint32
+	length_and_code uint32
+}
+
+func initBackwardMatch(self *backwardMatch, dist uint, len uint) {
+	self.distance = uint32(dist)
+	self.length_and_code = uint32(len << 5)
+}
+
+func initDictionaryBackwardMatch(self *backwardMatch, dist uint, len uint, len_code uint) {
+	self.distance = uint32(dist)
+	var tmp uint
+	if len == len_code {
+		tmp = 0
+	} else {
+		tmp = len_code
+	}
+	self.length_and_code = uint32(len<<5 | tmp)
+}
+
+func backwardMatchLength(self *backwardMatch) uint {
+	return uint(self.length_and_code >> 5)
+}
+
+func backwardMatchLengthCode(self *backwardMatch) uint {
+	var code uint = uint(self.length_and_code) & 31
+	if code != 0 {
+		return code
+	} else {
+		return backwardMatchLength(self)
+	}
+}
+
+func hasherReset(handle hasherHandle) {
+	if handle == nil {
+		return
+	}
+	handle.Common().is_prepared_ = false
+}
+
+func newHasher(typ int) hasherHandle {
+	switch typ {
+	case 2:
+		return &hashLongestMatchQuickly{
+			bucketBits:    16,
+			bucketSweep:   1,
+			hashLen:       5,
+			useDictionary: true,
+		}
+	case 3:
+		return &hashLongestMatchQuickly{
+			bucketBits:    16,
+			bucketSweep:   2,
+			hashLen:       5,
+			useDictionary: false,
+		}
+	case 4:
+		return &hashLongestMatchQuickly{
+			bucketBits:    17,
+			bucketSweep:   4,
+			hashLen:       5,
+			useDictionary: true,
+		}
+	case 5:
+		return new(h5)
+	case 6:
+		return new(h6)
+	case 10:
+		return new(h10)
+	case 35:
+		return &hashComposite{
+			ha: newHasher(3),
+			hb: &hashRolling{jump: 4},
+		}
+	case 40:
+		return &hashForgetfulChain{
+			bucketBits:              15,
+			numBanks:                1,
+			bankBits:                16,
+			numLastDistancesToCheck: 4,
+		}
+	case 41:
+		return &hashForgetfulChain{
+			bucketBits:              15,
+			numBanks:                1,
+			bankBits:                16,
+			numLastDistancesToCheck: 10,
+		}
+	case 42:
+		return &hashForgetfulChain{
+			bucketBits:              15,
+			numBanks:                512,
+			bankBits:                9,
+			numLastDistancesToCheck: 16,
+		}
+	case 54:
+		return &hashLongestMatchQuickly{
+			bucketBits:    20,
+			bucketSweep:   4,
+			hashLen:       7,
+			useDictionary: false,
+		}
+	case 55:
+		return &hashComposite{
+			ha: newHasher(54),
+			hb: &hashRolling{jump: 4},
+		}
+	case 65:
+		return &hashComposite{
+			ha: newHasher(6),
+			hb: &hashRolling{jump: 1},
+		}
+	}
+
+	panic(fmt.Sprintf("unknown hasher type: %d", typ))
+}
+
+func hasherSetup(handle *hasherHandle, params *encoderParams, data []byte, position uint, input_size uint, is_last bool) {
+	var self hasherHandle = nil
+	var common *hasherCommon = nil
+	var one_shot bool = (position == 0 && is_last)
+	if *handle == nil {
+		chooseHasher(params, &params.hasher)
+		self = newHasher(params.hasher.type_)
+
+		*handle = self
+		common = self.Common()
+		common.params = params.hasher
+		self.Initialize(params)
+	}
+
+	self = *handle
+	common = self.Common()
+	if !common.is_prepared_ {
+		self.Prepare(one_shot, input_size, data)
+
+		if position == 0 {
+			common.dict_num_lookups = 0
+			common.dict_num_matches = 0
+		}
+
+		common.is_prepared_ = true
+	}
+}
+
+func initOrStitchToPreviousBlock(handle *hasherHandle, data []byte, mask uint, params *encoderParams, position uint, input_size uint, is_last bool) {
+	var self hasherHandle
+	hasherSetup(handle, params, data, position, input_size, is_last)
+	self = *handle
+	self.StitchToPreviousBlock(input_size, position, data, mask)
+}

vendor/github.com/andybalholm/brotli/hash_composite.go

@@ -0,0 +1,93 @@
+package brotli
+
+/* Copyright 2018 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func (h *hashComposite) HashTypeLength() uint {
+	var a uint = h.ha.HashTypeLength()
+	var b uint = h.hb.HashTypeLength()
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func (h *hashComposite) StoreLookahead() uint {
+	var a uint = h.ha.StoreLookahead()
+	var b uint = h.hb.StoreLookahead()
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+/* Composite hasher: This hasher allows to combine two other hashers, HASHER_A
+   and HASHER_B. */
+type hashComposite struct {
+	hasherCommon
+	ha     hasherHandle
+	hb     hasherHandle
+	params *encoderParams
+}
+
+func (h *hashComposite) Initialize(params *encoderParams) {
+	h.params = params
+}
+
+/* TODO: Initialize of the hashers is defered to Prepare (and params
+   remembered here) because we don't get the one_shot and input_size params
+   here that are needed to know the memory size of them. Instead provide
+   those params to all hashers InitializehashComposite */
+func (h *hashComposite) Prepare(one_shot bool, input_size uint, data []byte) {
+	if h.ha == nil {
+		var common_a *hasherCommon
+		var common_b *hasherCommon
+
+		common_a = h.ha.Common()
+		common_a.params = h.params.hasher
+		common_a.is_prepared_ = false
+		common_a.dict_num_lookups = 0
+		common_a.dict_num_matches = 0
+		h.ha.Initialize(h.params)
+
+		common_b = h.hb.Common()
+		common_b.params = h.params.hasher
+		common_b.is_prepared_ = false
+		common_b.dict_num_lookups = 0
+		common_b.dict_num_matches = 0
+		h.hb.Initialize(h.params)
+	}
+
+	h.ha.Prepare(one_shot, input_size, data)
+	h.hb.Prepare(one_shot, input_size, data)
+}
+
+func (h *hashComposite) Store(data []byte, mask uint, ix uint) {
+	h.ha.Store(data, mask, ix)
+	h.hb.Store(data, mask, ix)
+}
+
+func (h *hashComposite) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+	h.ha.StoreRange(data, mask, ix_start, ix_end)
+	h.hb.StoreRange(data, mask, ix_start, ix_end)
+}
+
+func (h *hashComposite) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ring_buffer_mask uint) {
+	h.ha.StitchToPreviousBlock(num_bytes, position, ringbuffer, ring_buffer_mask)
+	h.hb.StitchToPreviousBlock(num_bytes, position, ringbuffer, ring_buffer_mask)
+}
+
+func (h *hashComposite) PrepareDistanceCache(distance_cache []int) {
+	h.ha.PrepareDistanceCache(distance_cache)
+	h.hb.PrepareDistanceCache(distance_cache)
+}
+
+func (h *hashComposite) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	h.ha.FindLongestMatch(dictionary, data, ring_buffer_mask, distance_cache, cur_ix, max_length, max_backward, gap, max_distance, out)
+	h.hb.FindLongestMatch(dictionary, data, ring_buffer_mask, distance_cache, cur_ix, max_length, max_backward, gap, max_distance, out)
+}

vendor/github.com/andybalholm/brotli/hash_forgetful_chain.go

@@ -0,0 +1,252 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2016 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func (*hashForgetfulChain) HashTypeLength() uint {
+	return 4
+}
+
+func (*hashForgetfulChain) StoreLookahead() uint {
+	return 4
+}
+
+/* HashBytes is the function that chooses the bucket to place the address in.*/
+func (h *hashForgetfulChain) HashBytes(data []byte) uint {
+	var hash uint32 = binary.LittleEndian.Uint32(data) * kHashMul32
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return uint(hash >> (32 - h.bucketBits))
+}
+
+type slot struct {
+	delta uint16
+	next  uint16
+}
+
+/* A (forgetful) hash table to the data seen by the compressor, to
+   help create backward references to previous data.
+
+   Hashes are stored in chains which are bucketed to groups. Group of chains
+   share a storage "bank". When more than "bank size" chain nodes are added,
+   oldest nodes are replaced; this way several chains may share a tail. */
+type hashForgetfulChain struct {
+	hasherCommon
+
+	bucketBits              uint
+	numBanks                uint
+	bankBits                uint
+	numLastDistancesToCheck int
+
+	addr          []uint32
+	head          []uint16
+	tiny_hash     [65536]byte
+	banks         [][]slot
+	free_slot_idx []uint16
+	max_hops      uint
+}
+
+func (h *hashForgetfulChain) Initialize(params *encoderParams) {
+	var q uint
+	if params.quality > 6 {
+		q = 7
+	} else {
+		q = 8
+	}
+	h.max_hops = q << uint(params.quality-4)
+
+	bankSize := 1 << h.bankBits
+	bucketSize := 1 << h.bucketBits
+
+	h.addr = make([]uint32, bucketSize)
+	h.head = make([]uint16, bucketSize)
+	h.banks = make([][]slot, h.numBanks)
+	for i := range h.banks {
+		h.banks[i] = make([]slot, bankSize)
+	}
+	h.free_slot_idx = make([]uint16, h.numBanks)
+}
+
+func (h *hashForgetfulChain) Prepare(one_shot bool, input_size uint, data []byte) {
+	var partial_prepare_threshold uint = (1 << h.bucketBits) >> 6
+	/* Partial preparation is 100 times slower (per socket). */
+	if one_shot && input_size <= partial_prepare_threshold {
+		var i uint
+		for i = 0; i < input_size; i++ {
+			var bucket uint = h.HashBytes(data[i:])
+
+			/* See InitEmpty comment. */
+			h.addr[bucket] = 0xCCCCCCCC
+
+			h.head[bucket] = 0xCCCC
+		}
+	} else {
+		/* Fill |addr| array with 0xCCCCCCCC value. Because of wrapping, position
+		   processed by hasher never reaches 3GB + 64M; this makes all new chains
+		   to be terminated after the first node. */
+		for i := range h.addr {
+			h.addr[i] = 0xCCCCCCCC
+		}
+
+		for i := range h.head {
+			h.head[i] = 0
+		}
+	}
+
+	h.tiny_hash = [65536]byte{}
+	for i := range h.free_slot_idx {
+		h.free_slot_idx[i] = 0
+	}
+}
+
+/* Look at 4 bytes at &data[ix & mask]. Compute a hash from these, and prepend
+   node to corresponding chain; also update tiny_hash for current position. */
+func (h *hashForgetfulChain) Store(data []byte, mask uint, ix uint) {
+	var key uint = h.HashBytes(data[ix&mask:])
+	var bank uint = key & (h.numBanks - 1)
+	idx := uint(h.free_slot_idx[bank]) & ((1 << h.bankBits) - 1)
+	h.free_slot_idx[bank]++
+	var delta uint = ix - uint(h.addr[key])
+	h.tiny_hash[uint16(ix)] = byte(key)
+	if delta > 0xFFFF {
+		delta = 0xFFFF
+	}
+	h.banks[bank][idx].delta = uint16(delta)
+	h.banks[bank][idx].next = h.head[key]
+	h.addr[key] = uint32(ix)
+	h.head[key] = uint16(idx)
+}
+
+func (h *hashForgetfulChain) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+	var i uint
+	for i = ix_start; i < ix_end; i++ {
+		h.Store(data, mask, i)
+	}
+}
+
+func (h *hashForgetfulChain) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ring_buffer_mask uint) {
+	if num_bytes >= h.HashTypeLength()-1 && position >= 3 {
+		/* Prepare the hashes for three last bytes of the last write.
+		   These could not be calculated before, since they require knowledge
+		   of both the previous and the current block. */
+		h.Store(ringbuffer, ring_buffer_mask, position-3)
+		h.Store(ringbuffer, ring_buffer_mask, position-2)
+		h.Store(ringbuffer, ring_buffer_mask, position-1)
+	}
+}
+
+func (h *hashForgetfulChain) PrepareDistanceCache(distance_cache []int) {
+	prepareDistanceCache(distance_cache, h.numLastDistancesToCheck)
+}
+
+/* Find a longest backward match of &data[cur_ix] up to the length of
+   max_length and stores the position cur_ix in the hash table.
+
+   REQUIRES: PrepareDistanceCachehashForgetfulChain must be invoked for current distance cache
+             values; if this method is invoked repeatedly with the same distance
+             cache values, it is enough to invoke PrepareDistanceCachehashForgetfulChain once.
+
+   Does not look for matches longer than max_length.
+   Does not look for matches further away than max_backward.
+   Writes the best match into |out|.
+   |out|->score is updated only if a better match is found. */
+func (h *hashForgetfulChain) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var min_score uint = out.score
+	var best_score uint = out.score
+	var best_len uint = out.len
+	var key uint = h.HashBytes(data[cur_ix_masked:])
+	var tiny_hash byte = byte(key)
+	/* Don't accept a short copy from far away. */
+	out.len = 0
+
+	out.len_code_delta = 0
+
+	/* Try last distance first. */
+	for i := 0; i < h.numLastDistancesToCheck; i++ {
+		var backward uint = uint(distance_cache[i])
+		var prev_ix uint = (cur_ix - backward)
+
+		/* For distance code 0 we want to consider 2-byte matches. */
+		if i > 0 && h.tiny_hash[uint16(prev_ix)] != tiny_hash {
+			continue
+		}
+		if prev_ix >= cur_ix || backward > max_backward {
+			continue
+		}
+
+		prev_ix &= ring_buffer_mask
+		{
+			var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+			if len >= 2 {
+				var score uint = backwardReferenceScoreUsingLastDistance(uint(len))
+				if best_score < score {
+					if i != 0 {
+						score -= backwardReferencePenaltyUsingLastDistance(uint(i))
+					}
+					if best_score < score {
+						best_score = score
+						best_len = uint(len)
+						out.len = best_len
+						out.distance = backward
+						out.score = best_score
+					}
+				}
+			}
+		}
+	}
+	{
+		var bank uint = key & (h.numBanks - 1)
+		var backward uint = 0
+		var hops uint = h.max_hops
+		var delta uint = cur_ix - uint(h.addr[key])
+		var slot uint = uint(h.head[key])
+		for {
+			tmp6 := hops
+			hops--
+			if tmp6 == 0 {
+				break
+			}
+			var prev_ix uint
+			var last uint = slot
+			backward += delta
+			if backward > max_backward {
+				break
+			}
+			prev_ix = (cur_ix - backward) & ring_buffer_mask
+			slot = uint(h.banks[bank][last].next)
+			delta = uint(h.banks[bank][last].delta)
+			if cur_ix_masked+best_len > ring_buffer_mask || prev_ix+best_len > ring_buffer_mask || data[cur_ix_masked+best_len] != data[prev_ix+best_len] {
+				continue
+			}
+			{
+				var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+				if len >= 4 {
+					/* Comparing for >= 3 does not change the semantics, but just saves
+					   for a few unnecessary binary logarithms in backward reference
+					   score, since we are not interested in such short matches. */
+					var score uint = backwardReferenceScore(uint(len), backward)
+					if best_score < score {
+						best_score = score
+						best_len = uint(len)
+						out.len = best_len
+						out.distance = backward
+						out.score = best_score
+					}
+				}
+			}
+		}
+
+		h.Store(data, ring_buffer_mask, cur_ix)
+	}
+
+	if out.score == min_score {
+		searchInStaticDictionary(dictionary, h, data[cur_ix_masked:], max_length, max_backward+gap, max_distance, out, false)
+	}
+}

vendor/github.com/andybalholm/brotli/hash_longest_match_quickly.go

@@ -0,0 +1,214 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* For BUCKET_SWEEP == 1, enabling the dictionary lookup makes compression
+   a little faster (0.5% - 1%) and it compresses 0.15% better on small text
+   and HTML inputs. */
+
+func (*hashLongestMatchQuickly) HashTypeLength() uint {
+	return 8
+}
+
+func (*hashLongestMatchQuickly) StoreLookahead() uint {
+	return 8
+}
+
+/* HashBytes is the function that chooses the bucket to place
+   the address in. The HashLongestMatch and hashLongestMatchQuickly
+   classes have separate, different implementations of hashing. */
+func (h *hashLongestMatchQuickly) HashBytes(data []byte) uint32 {
+	var hash uint64 = ((binary.LittleEndian.Uint64(data) << (64 - 8*h.hashLen)) * kHashMul64)
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return uint32(hash >> (64 - h.bucketBits))
+}
+
+/* A (forgetful) hash table to the data seen by the compressor, to
+   help create backward references to previous data.
+
+   This is a hash map of fixed size (1 << 16). Starting from the
+   given index, 1 buckets are used to store values of a key. */
+type hashLongestMatchQuickly struct {
+	hasherCommon
+
+	bucketBits    uint
+	bucketSweep   int
+	hashLen       uint
+	useDictionary bool
+
+	buckets []uint32
+}
+
+func (h *hashLongestMatchQuickly) Initialize(params *encoderParams) {
+	h.buckets = make([]uint32, 1<<h.bucketBits+h.bucketSweep)
+}
+
+func (h *hashLongestMatchQuickly) Prepare(one_shot bool, input_size uint, data []byte) {
+	var partial_prepare_threshold uint = (4 << h.bucketBits) >> 7
+	/* Partial preparation is 100 times slower (per socket). */
+	if one_shot && input_size <= partial_prepare_threshold {
+		var i uint
+		for i = 0; i < input_size; i++ {
+			var key uint32 = h.HashBytes(data[i:])
+			for j := 0; j < h.bucketSweep; j++ {
+				h.buckets[key+uint32(j)] = 0
+			}
+		}
+	} else {
+		/* It is not strictly necessary to fill this buffer here, but
+		   not filling will make the results of the compression stochastic
+		   (but correct). This is because random data would cause the
+		   system to find accidentally good backward references here and there. */
+		for i := range h.buckets {
+			h.buckets[i] = 0
+		}
+	}
+}
+
+/* Look at 5 bytes at &data[ix & mask].
+   Compute a hash from these, and store the value somewhere within
+   [ix .. ix+3]. */
+func (h *hashLongestMatchQuickly) Store(data []byte, mask uint, ix uint) {
+	var key uint32 = h.HashBytes(data[ix&mask:])
+	var off uint32 = uint32(ix>>3) % uint32(h.bucketSweep)
+	/* Wiggle the value with the bucket sweep range. */
+	h.buckets[key+off] = uint32(ix)
+}
+
+func (h *hashLongestMatchQuickly) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+	var i uint
+	for i = ix_start; i < ix_end; i++ {
+		h.Store(data, mask, i)
+	}
+}
+
+func (h *hashLongestMatchQuickly) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ringbuffer_mask uint) {
+	if num_bytes >= h.HashTypeLength()-1 && position >= 3 {
+		/* Prepare the hashes for three last bytes of the last write.
+		   These could not be calculated before, since they require knowledge
+		   of both the previous and the current block. */
+		h.Store(ringbuffer, ringbuffer_mask, position-3)
+		h.Store(ringbuffer, ringbuffer_mask, position-2)
+		h.Store(ringbuffer, ringbuffer_mask, position-1)
+	}
+}
+
+func (*hashLongestMatchQuickly) PrepareDistanceCache(distance_cache []int) {
+}
+
+/* Find a longest backward match of &data[cur_ix & ring_buffer_mask]
+   up to the length of max_length and stores the position cur_ix in the
+   hash table.
+
+   Does not look for matches longer than max_length.
+   Does not look for matches further away than max_backward.
+   Writes the best match into |out|.
+   |out|->score is updated only if a better match is found. */
+func (h *hashLongestMatchQuickly) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	var best_len_in uint = out.len
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var key uint32 = h.HashBytes(data[cur_ix_masked:])
+	var compare_char int = int(data[cur_ix_masked+best_len_in])
+	var min_score uint = out.score
+	var best_score uint = out.score
+	var best_len uint = best_len_in
+	var cached_backward uint = uint(distance_cache[0])
+	var prev_ix uint = cur_ix - cached_backward
+	var bucket []uint32
+	out.len_code_delta = 0
+	if prev_ix < cur_ix {
+		prev_ix &= uint(uint32(ring_buffer_mask))
+		if compare_char == int(data[prev_ix+best_len]) {
+			var len uint = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+			if len >= 4 {
+				var score uint = backwardReferenceScoreUsingLastDistance(uint(len))
+				if best_score < score {
+					best_score = score
+					best_len = uint(len)
+					out.len = uint(len)
+					out.distance = cached_backward
+					out.score = best_score
+					compare_char = int(data[cur_ix_masked+best_len])
+					if h.bucketSweep == 1 {
+						h.buckets[key] = uint32(cur_ix)
+						return
+					}
+				}
+			}
+		}
+	}
+
+	if h.bucketSweep == 1 {
+		var backward uint
+		var len uint
+
+		/* Only one to look for, don't bother to prepare for a loop. */
+		prev_ix = uint(h.buckets[key])
+
+		h.buckets[key] = uint32(cur_ix)
+		backward = cur_ix - prev_ix
+		prev_ix &= uint(uint32(ring_buffer_mask))
+		if compare_char != int(data[prev_ix+best_len_in]) {
+			return
+		}
+
+		if backward == 0 || backward > max_backward {
+			return
+		}
+
+		len = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+		if len >= 4 {
+			var score uint = backwardReferenceScore(uint(len), backward)
+			if best_score < score {
+				out.len = uint(len)
+				out.distance = backward
+				out.score = score
+				return
+			}
+		}
+	} else {
+		bucket = h.buckets[key:]
+		var i int
+		prev_ix = uint(bucket[0])
+		bucket = bucket[1:]
+		for i = 0; i < h.bucketSweep; (func() { i++; tmp3 := bucket; bucket = bucket[1:]; prev_ix = uint(tmp3[0]) })() {
+			var backward uint = cur_ix - prev_ix
+			var len uint
+			prev_ix &= uint(uint32(ring_buffer_mask))
+			if compare_char != int(data[prev_ix+best_len]) {
+				continue
+			}
+
+			if backward == 0 || backward > max_backward {
+				continue
+			}
+
+			len = findMatchLengthWithLimit(data[prev_ix:], data[cur_ix_masked:], max_length)
+			if len >= 4 {
+				var score uint = backwardReferenceScore(uint(len), backward)
+				if best_score < score {
+					best_score = score
+					best_len = uint(len)
+					out.len = best_len
+					out.distance = backward
+					out.score = score
+					compare_char = int(data[cur_ix_masked+best_len])
+				}
+			}
+		}
+	}
+
+	if h.useDictionary && min_score == out.score {
+		searchInStaticDictionary(dictionary, h, data[cur_ix_masked:], max_length, max_backward+gap, max_distance, out, true)
+	}
+
+	h.buckets[key+uint32((cur_ix>>3)%uint(h.bucketSweep))] = uint32(cur_ix)
+}

vendor/github.com/andybalholm/brotli/hash_rolling.go

@@ -0,0 +1,168 @@
+package brotli
+
+/* Copyright 2018 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* NOTE: this hasher does not search in the dictionary. It is used as
+   backup-hasher, the main hasher already searches in it. */
+
+const kRollingHashMul32 uint32 = 69069
+
+const kInvalidPosHashRolling uint32 = 0xffffffff
+
+/* This hasher uses a longer forward length, but returning a higher value here
+   will hurt compression by the main hasher when combined with a composite
+   hasher. The hasher tests for forward itself instead. */
+func (*hashRolling) HashTypeLength() uint {
+	return 4
+}
+
+func (*hashRolling) StoreLookahead() uint {
+	return 4
+}
+
+/* Computes a code from a single byte. A lookup table of 256 values could be
+   used, but simply adding 1 works about as good. */
+func (*hashRolling) HashByte(b byte) uint32 {
+	return uint32(b) + 1
+}
+
+func (h *hashRolling) HashRollingFunctionInitial(state uint32, add byte, factor uint32) uint32 {
+	return uint32(factor*state + h.HashByte(add))
+}
+
+func (h *hashRolling) HashRollingFunction(state uint32, add byte, rem byte, factor uint32, factor_remove uint32) uint32 {
+	return uint32(factor*state + h.HashByte(add) - factor_remove*h.HashByte(rem))
+}
+
+/* Rolling hash for long distance long string matches. Stores one position
+   per bucket, bucket key is computed over a long region. */
+type hashRolling struct {
+	hasherCommon
+
+	jump int
+
+	state         uint32
+	table         []uint32
+	next_ix       uint
+	factor        uint32
+	factor_remove uint32
+}
+
+func (h *hashRolling) Initialize(params *encoderParams) {
+	h.state = 0
+	h.next_ix = 0
+
+	h.factor = kRollingHashMul32
+
+	/* Compute the factor of the oldest byte to remove: factor**steps modulo
+	   0xffffffff (the multiplications rely on 32-bit overflow) */
+	h.factor_remove = 1
+
+	for i := 0; i < 32; i += h.jump {
+		h.factor_remove *= h.factor
+	}
+
+	h.table = make([]uint32, 16777216)
+	for i := 0; i < 16777216; i++ {
+		h.table[i] = kInvalidPosHashRolling
+	}
+}
+
+func (h *hashRolling) Prepare(one_shot bool, input_size uint, data []byte) {
+	/* Too small size, cannot use this hasher. */
+	if input_size < 32 {
+		return
+	}
+	h.state = 0
+	for i := 0; i < 32; i += h.jump {
+		h.state = h.HashRollingFunctionInitial(h.state, data[i], h.factor)
+	}
+}
+
+func (*hashRolling) Store(data []byte, mask uint, ix uint) {
+}
+
+func (*hashRolling) StoreRange(data []byte, mask uint, ix_start uint, ix_end uint) {
+}
+
+func (h *hashRolling) StitchToPreviousBlock(num_bytes uint, position uint, ringbuffer []byte, ring_buffer_mask uint) {
+	var position_masked uint
+	/* In this case we must re-initialize the hasher from scratch from the
+	   current position. */
+
+	var available uint = num_bytes
+	if position&uint(h.jump-1) != 0 {
+		var diff uint = uint(h.jump) - (position & uint(h.jump-1))
+		if diff > available {
+			available = 0
+		} else {
+			available = available - diff
+		}
+		position += diff
+	}
+
+	position_masked = position & ring_buffer_mask
+
+	/* wrapping around ringbuffer not handled. */
+	if available > ring_buffer_mask-position_masked {
+		available = ring_buffer_mask - position_masked
+	}
+
+	h.Prepare(false, available, ringbuffer[position&ring_buffer_mask:])
+	h.next_ix = position
+}
+
+func (*hashRolling) PrepareDistanceCache(distance_cache []int) {
+}
+
+func (h *hashRolling) FindLongestMatch(dictionary *encoderDictionary, data []byte, ring_buffer_mask uint, distance_cache []int, cur_ix uint, max_length uint, max_backward uint, gap uint, max_distance uint, out *hasherSearchResult) {
+	var cur_ix_masked uint = cur_ix & ring_buffer_mask
+	var pos uint = h.next_ix
+
+	if cur_ix&uint(h.jump-1) != 0 {
+		return
+	}
+
+	/* Not enough lookahead */
+	if max_length < 32 {
+		return
+	}
+
+	for pos = h.next_ix; pos <= cur_ix; pos += uint(h.jump) {
+		var code uint32 = h.state & ((16777216 * 64) - 1)
+		var rem byte = data[pos&ring_buffer_mask]
+		var add byte = data[(pos+32)&ring_buffer_mask]
+		var found_ix uint = uint(kInvalidPosHashRolling)
+
+		h.state = h.HashRollingFunction(h.state, add, rem, h.factor, h.factor_remove)
+
+		if code < 16777216 {
+			found_ix = uint(h.table[code])
+			h.table[code] = uint32(pos)
+			if pos == cur_ix && uint32(found_ix) != kInvalidPosHashRolling {
+				/* The cast to 32-bit makes backward distances up to 4GB work even
+				   if cur_ix is above 4GB, despite using 32-bit values in the table. */
+				var backward uint = uint(uint32(cur_ix - found_ix))
+				if backward <= max_backward {
+					var found_ix_masked uint = found_ix & ring_buffer_mask
+					var len uint = findMatchLengthWithLimit(data[found_ix_masked:], data[cur_ix_masked:], max_length)
+					if len >= 4 && len > out.len {
+						var score uint = backwardReferenceScore(uint(len), backward)
+						if score > out.score {
+							out.len = uint(len)
+							out.distance = backward
+							out.score = score
+							out.len_code_delta = 0
+						}
+					}
+				}
+			}
+		}
+	}
+
+	h.next_ix = cur_ix + uint(h.jump)
+}

vendor/github.com/andybalholm/brotli/histogram.go

@@ -0,0 +1,226 @@
+package brotli
+
+import "math"
+
+/* The distance symbols effectively used by "Large Window Brotli" (32-bit). */
+const numHistogramDistanceSymbols = 544
+
+type histogramLiteral struct {
+	data_        [numLiteralSymbols]uint32
+	total_count_ uint
+	bit_cost_    float64
+}
+
+func histogramClearLiteral(self *histogramLiteral) {
+	self.data_ = [numLiteralSymbols]uint32{}
+	self.total_count_ = 0
+	self.bit_cost_ = math.MaxFloat64
+}
+
+func clearHistogramsLiteral(array []histogramLiteral, length uint) {
+	var i uint
+	for i = 0; i < length; i++ {
+		histogramClearLiteral(&array[i:][0])
+	}
+}
+
+func histogramAddLiteral(self *histogramLiteral, val uint) {
+	self.data_[val]++
+	self.total_count_++
+}
+
+func histogramAddVectorLiteral(self *histogramLiteral, p []byte, n uint) {
+	self.total_count_ += n
+	n += 1
+	for {
+		n--
+		if n == 0 {
+			break
+		}
+		self.data_[p[0]]++
+		p = p[1:]
+	}
+}
+
+func histogramAddHistogramLiteral(self *histogramLiteral, v *histogramLiteral) {
+	var i uint
+	self.total_count_ += v.total_count_
+	for i = 0; i < numLiteralSymbols; i++ {
+		self.data_[i] += v.data_[i]
+	}
+}
+
+func histogramDataSizeLiteral() uint {
+	return numLiteralSymbols
+}
+
+type histogramCommand struct {
+	data_        [numCommandSymbols]uint32
+	total_count_ uint
+	bit_cost_    float64
+}
+
+func histogramClearCommand(self *histogramCommand) {
+	self.data_ = [numCommandSymbols]uint32{}
+	self.total_count_ = 0
+	self.bit_cost_ = math.MaxFloat64
+}
+
+func clearHistogramsCommand(array []histogramCommand, length uint) {
+	var i uint
+	for i = 0; i < length; i++ {
+		histogramClearCommand(&array[i:][0])
+	}
+}
+
+func histogramAddCommand(self *histogramCommand, val uint) {
+	self.data_[val]++
+	self.total_count_++
+}
+
+func histogramAddVectorCommand(self *histogramCommand, p []uint16, n uint) {
+	self.total_count_ += n
+	n += 1
+	for {
+		n--
+		if n == 0 {
+			break
+		}
+		self.data_[p[0]]++
+		p = p[1:]
+	}
+}
+
+func histogramAddHistogramCommand(self *histogramCommand, v *histogramCommand) {
+	var i uint
+	self.total_count_ += v.total_count_
+	for i = 0; i < numCommandSymbols; i++ {
+		self.data_[i] += v.data_[i]
+	}
+}
+
+func histogramDataSizeCommand() uint {
+	return numCommandSymbols
+}
+
+type histogramDistance struct {
+	data_        [numDistanceSymbols]uint32
+	total_count_ uint
+	bit_cost_    float64
+}
+
+func histogramClearDistance(self *histogramDistance) {
+	self.data_ = [numDistanceSymbols]uint32{}
+	self.total_count_ = 0
+	self.bit_cost_ = math.MaxFloat64
+}
+
+func clearHistogramsDistance(array []histogramDistance, length uint) {
+	var i uint
+	for i = 0; i < length; i++ {
+		histogramClearDistance(&array[i:][0])
+	}
+}
+
+func histogramAddDistance(self *histogramDistance, val uint) {
+	self.data_[val]++
+	self.total_count_++
+}
+
+func histogramAddVectorDistance(self *histogramDistance, p []uint16, n uint) {
+	self.total_count_ += n
+	n += 1
+	for {
+		n--
+		if n == 0 {
+			break
+		}
+		self.data_[p[0]]++
+		p = p[1:]
+	}
+}
+
+func histogramAddHistogramDistance(self *histogramDistance, v *histogramDistance) {
+	var i uint
+	self.total_count_ += v.total_count_
+	for i = 0; i < numDistanceSymbols; i++ {
+		self.data_[i] += v.data_[i]
+	}
+}
+
+func histogramDataSizeDistance() uint {
+	return numDistanceSymbols
+}
+
+type blockSplitIterator struct {
+	split_  *blockSplit
+	idx_    uint
+	type_   uint
+	length_ uint
+}
+
+func initBlockSplitIterator(self *blockSplitIterator, split *blockSplit) {
+	self.split_ = split
+	self.idx_ = 0
+	self.type_ = 0
+	if len(split.lengths) > 0 {
+		self.length_ = uint(split.lengths[0])
+	} else {
+		self.length_ = 0
+	}
+}
+
+func blockSplitIteratorNext(self *blockSplitIterator) {
+	if self.length_ == 0 {
+		self.idx_++
+		self.type_ = uint(self.split_.types[self.idx_])
+		self.length_ = uint(self.split_.lengths[self.idx_])
+	}
+
+	self.length_--
+}
+
+func buildHistogramsWithContext(cmds []command, literal_split *blockSplit, insert_and_copy_split *blockSplit, dist_split *blockSplit, ringbuffer []byte, start_pos uint, mask uint, prev_byte byte, prev_byte2 byte, context_modes []int, literal_histograms []histogramLiteral, insert_and_copy_histograms []histogramCommand, copy_dist_histograms []histogramDistance) {
+	var pos uint = start_pos
+	var literal_it blockSplitIterator
+	var insert_and_copy_it blockSplitIterator
+	var dist_it blockSplitIterator
+
+	initBlockSplitIterator(&literal_it, literal_split)
+	initBlockSplitIterator(&insert_and_copy_it, insert_and_copy_split)
+	initBlockSplitIterator(&dist_it, dist_split)
+	for i := range cmds {
+		var cmd *command = &cmds[i]
+		var j uint
+		blockSplitIteratorNext(&insert_and_copy_it)
+		histogramAddCommand(&insert_and_copy_histograms[insert_and_copy_it.type_], uint(cmd.cmd_prefix_))
+
+		/* TODO: unwrap iterator blocks. */
+		for j = uint(cmd.insert_len_); j != 0; j-- {
+			var context uint
+			blockSplitIteratorNext(&literal_it)
+			context = literal_it.type_
+			if context_modes != nil {
+				var lut contextLUT = getContextLUT(context_modes[context])
+				context = (context << literalContextBits) + uint(getContext(prev_byte, prev_byte2, lut))
+			}
+
+			histogramAddLiteral(&literal_histograms[context], uint(ringbuffer[pos&mask]))
+			prev_byte2 = prev_byte
+			prev_byte = ringbuffer[pos&mask]
+			pos++
+		}
+
+		pos += uint(commandCopyLen(cmd))
+		if commandCopyLen(cmd) != 0 {
+			prev_byte2 = ringbuffer[(pos-2)&mask]
+			prev_byte = ringbuffer[(pos-1)&mask]
+			if cmd.cmd_prefix_ >= 128 {
+				var context uint
+				blockSplitIteratorNext(&dist_it)
+				context = uint(uint32(dist_it.type_<<distanceContextBits) + commandDistanceContext(cmd))
+				histogramAddDistance(&copy_dist_histograms[context], uint(cmd.dist_prefix_)&0x3FF)
+			}
+		}
+	}
+}

vendor/github.com/andybalholm/brotli/http.go

@@ -0,0 +1,192 @@
+package brotli
+
+import (
+	"compress/gzip"
+	"io"
+	"net/http"
+	"strings"
+)
+
+// HTTPCompressor chooses a compression method (brotli, gzip, or none) based on
+// the Accept-Encoding header, sets the Content-Encoding header, and returns a
+// WriteCloser that implements that compression. The Close method must be called
+// before the current HTTP handler returns.
+//
+// Due to https://github.com/golang/go/issues/31753, the response will not be
+// compressed unless you set a Content-Type header before you call
+// HTTPCompressor.
+func HTTPCompressor(w http.ResponseWriter, r *http.Request) io.WriteCloser {
+	if w.Header().Get("Content-Type") == "" {
+		return nopCloser{w}
+	}
+
+	if w.Header().Get("Vary") == "" {
+		w.Header().Set("Vary", "Accept-Encoding")
+	}
+
+	encoding := negotiateContentEncoding(r, []string{"br", "gzip"})
+	switch encoding {
+	case "br":
+		w.Header().Set("Content-Encoding", "br")
+		return NewWriter(w)
+	case "gzip":
+		w.Header().Set("Content-Encoding", "gzip")
+		return gzip.NewWriter(w)
+	}
+	return nopCloser{w}
+}
+
+// negotiateContentEncoding returns the best offered content encoding for the
+// request's Accept-Encoding header. If two offers match with equal weight and
+// then the offer earlier in the list is preferred. If no offers are
+// acceptable, then "" is returned.
+func negotiateContentEncoding(r *http.Request, offers []string) string {
+	bestOffer := "identity"
+	bestQ := -1.0
+	specs := parseAccept(r.Header, "Accept-Encoding")
+	for _, offer := range offers {
+		for _, spec := range specs {
+			if spec.Q > bestQ &&
+				(spec.Value == "*" || spec.Value == offer) {
+				bestQ = spec.Q
+				bestOffer = offer
+			}
+		}
+	}
+	if bestQ == 0 {
+		bestOffer = ""
+	}
+	return bestOffer
+}
+
+// acceptSpec describes an Accept* header.
+type acceptSpec struct {
+	Value string
+	Q     float64
+}
+
+// parseAccept parses Accept* headers.
+func parseAccept(header http.Header, key string) (specs []acceptSpec) {
+loop:
+	for _, s := range header[key] {
+		for {
+			var spec acceptSpec
+			spec.Value, s = expectTokenSlash(s)
+			if spec.Value == "" {
+				continue loop
+			}
+			spec.Q = 1.0
+			s = skipSpace(s)
+			if strings.HasPrefix(s, ";") {
+				s = skipSpace(s[1:])
+				if !strings.HasPrefix(s, "q=") {
+					continue loop
+				}
+				spec.Q, s = expectQuality(s[2:])
+				if spec.Q < 0.0 {
+					continue loop
+				}
+			}
+			specs = append(specs, spec)
+			s = skipSpace(s)
+			if !strings.HasPrefix(s, ",") {
+				continue loop
+			}
+			s = skipSpace(s[1:])
+		}
+	}
+	return
+}
+
+func skipSpace(s string) (rest string) {
+	i := 0
+	for ; i < len(s); i++ {
+		if octetTypes[s[i]]&isSpace == 0 {
+			break
+		}
+	}
+	return s[i:]
+}
+
+func expectTokenSlash(s string) (token, rest string) {
+	i := 0
+	for ; i < len(s); i++ {
+		b := s[i]
+		if (octetTypes[b]&isToken == 0) && b != '/' {
+			break
+		}
+	}
+	return s[:i], s[i:]
+}
+
+func expectQuality(s string) (q float64, rest string) {
+	switch {
+	case len(s) == 0:
+		return -1, ""
+	case s[0] == '0':
+		q = 0
+	case s[0] == '1':
+		q = 1
+	default:
+		return -1, ""
+	}
+	s = s[1:]
+	if !strings.HasPrefix(s, ".") {
+		return q, s
+	}
+	s = s[1:]
+	i := 0
+	n := 0
+	d := 1
+	for ; i < len(s); i++ {
+		b := s[i]
+		if b < '0' || b > '9' {
+			break
+		}
+		n = n*10 + int(b) - '0'
+		d *= 10
+	}
+	return q + float64(n)/float64(d), s[i:]
+}
+
+// Octet types from RFC 2616.
+var octetTypes [256]octetType
+
+type octetType byte
+
+const (
+	isToken octetType = 1 << iota
+	isSpace
+)
+
+func init() {
+	// OCTET      = <any 8-bit sequence of data>
+	// CHAR       = <any US-ASCII character (octets 0 - 127)>
+	// CTL        = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
+	// CR         = <US-ASCII CR, carriage return (13)>
+	// LF         = <US-ASCII LF, linefeed (10)>
+	// SP         = <US-ASCII SP, space (32)>
+	// HT         = <US-ASCII HT, horizontal-tab (9)>
+	// <">        = <US-ASCII double-quote mark (34)>
+	// CRLF       = CR LF
+	// LWS        = [CRLF] 1*( SP | HT )
+	// TEXT       = <any OCTET except CTLs, but including LWS>
+	// separators = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | "\" | <">
+	//              | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT
+	// token      = 1*<any CHAR except CTLs or separators>
+	// qdtext     = <any TEXT except <">>
+
+	for c := 0; c < 256; c++ {
+		var t octetType
+		isCtl := c <= 31 || c == 127
+		isChar := 0 <= c && c <= 127
+		isSeparator := strings.ContainsRune(" \t\"(),/:;<=>?@[]\\{}", rune(c))
+		if strings.ContainsRune(" \t\r\n", rune(c)) {
+			t |= isSpace
+		}
+		if isChar && !isCtl && !isSeparator {
+			t |= isToken
+		}
+		octetTypes[c] = t
+	}
+}

vendor/github.com/andybalholm/brotli/huffman.go

@@ -0,0 +1,653 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Utilities for building Huffman decoding tables. */
+
+const huffmanMaxCodeLength = 15
+
+/* Maximum possible Huffman table size for an alphabet size of (index * 32),
+   max code length 15 and root table bits 8. */
+var kMaxHuffmanTableSize = []uint16{
+	256,
+	402,
+	436,
+	468,
+	500,
+	534,
+	566,
+	598,
+	630,
+	662,
+	694,
+	726,
+	758,
+	790,
+	822,
+	854,
+	886,
+	920,
+	952,
+	984,
+	1016,
+	1048,
+	1080,
+	1112,
+	1144,
+	1176,
+	1208,
+	1240,
+	1272,
+	1304,
+	1336,
+	1368,
+	1400,
+	1432,
+	1464,
+	1496,
+	1528,
+}
+
+/* BROTLI_NUM_BLOCK_LEN_SYMBOLS == 26 */
+const huffmanMaxSize26 = 396
+
+/* BROTLI_MAX_BLOCK_TYPE_SYMBOLS == 258 */
+const huffmanMaxSize258 = 632
+
+/* BROTLI_MAX_CONTEXT_MAP_SYMBOLS == 272 */
+const huffmanMaxSize272 = 646
+
+const huffmanMaxCodeLengthCodeLength = 5
+
+/* Do not create this struct directly - use the ConstructHuffmanCode
+ * constructor below! */
+type huffmanCode struct {
+	bits  byte
+	value uint16
+}
+
+func constructHuffmanCode(bits byte, value uint16) huffmanCode {
+	var h huffmanCode
+	h.bits = bits
+	h.value = value
+	return h
+}
+
+/* Builds Huffman lookup table assuming code lengths are in symbol order. */
+
+/* Builds Huffman lookup table assuming code lengths are in symbol order.
+   Returns size of resulting table. */
+
+/* Builds a simple Huffman table. The |num_symbols| parameter is to be
+   interpreted as follows: 0 means 1 symbol, 1 means 2 symbols,
+   2 means 3 symbols, 3 means 4 symbols with lengths [2, 2, 2, 2],
+   4 means 4 symbols with lengths [1, 2, 3, 3]. */
+
+/* Contains a collection of Huffman trees with the same alphabet size. */
+/* max_symbol is needed due to simple codes since log2(alphabet_size) could be
+   greater than log2(max_symbol). */
+type huffmanTreeGroup struct {
+	htrees        [][]huffmanCode
+	codes         []huffmanCode
+	alphabet_size uint16
+	max_symbol    uint16
+	num_htrees    uint16
+}
+
+const reverseBitsMax = 8
+
+const reverseBitsBase = 0
+
+var kReverseBits = [1 << reverseBitsMax]byte{
+	0x00,
+	0x80,
+	0x40,
+	0xC0,
+	0x20,
+	0xA0,
+	0x60,
+	0xE0,
+	0x10,
+	0x90,
+	0x50,
+	0xD0,
+	0x30,
+	0xB0,
+	0x70,
+	0xF0,
+	0x08,
+	0x88,
+	0x48,
+	0xC8,
+	0x28,
+	0xA8,
+	0x68,
+	0xE8,
+	0x18,
+	0x98,
+	0x58,
+	0xD8,
+	0x38,
+	0xB8,
+	0x78,
+	0xF8,
+	0x04,
+	0x84,
+	0x44,
+	0xC4,
+	0x24,
+	0xA4,
+	0x64,
+	0xE4,
+	0x14,
+	0x94,
+	0x54,
+	0xD4,
+	0x34,
+	0xB4,
+	0x74,
+	0xF4,
+	0x0C,
+	0x8C,
+	0x4C,
+	0xCC,
+	0x2C,
+	0xAC,
+	0x6C,
+	0xEC,
+	0x1C,
+	0x9C,
+	0x5C,
+	0xDC,
+	0x3C,
+	0xBC,
+	0x7C,
+	0xFC,
+	0x02,
+	0x82,
+	0x42,
+	0xC2,
+	0x22,
+	0xA2,
+	0x62,
+	0xE2,
+	0x12,
+	0x92,
+	0x52,
+	0xD2,
+	0x32,
+	0xB2,
+	0x72,
+	0xF2,
+	0x0A,
+	0x8A,
+	0x4A,
+	0xCA,
+	0x2A,
+	0xAA,
+	0x6A,
+	0xEA,
+	0x1A,
+	0x9A,
+	0x5A,
+	0xDA,
+	0x3A,
+	0xBA,
+	0x7A,
+	0xFA,
+	0x06,
+	0x86,
+	0x46,
+	0xC6,
+	0x26,
+	0xA6,
+	0x66,
+	0xE6,
+	0x16,
+	0x96,
+	0x56,
+	0xD6,
+	0x36,
+	0xB6,
+	0x76,
+	0xF6,
+	0x0E,
+	0x8E,
+	0x4E,
+	0xCE,
+	0x2E,
+	0xAE,
+	0x6E,
+	0xEE,
+	0x1E,
+	0x9E,
+	0x5E,
+	0xDE,
+	0x3E,
+	0xBE,
+	0x7E,
+	0xFE,
+	0x01,
+	0x81,
+	0x41,
+	0xC1,
+	0x21,
+	0xA1,
+	0x61,
+	0xE1,
+	0x11,
+	0x91,
+	0x51,
+	0xD1,
+	0x31,
+	0xB1,
+	0x71,
+	0xF1,
+	0x09,
+	0x89,
+	0x49,
+	0xC9,
+	0x29,
+	0xA9,
+	0x69,
+	0xE9,
+	0x19,
+	0x99,
+	0x59,
+	0xD9,
+	0x39,
+	0xB9,
+	0x79,
+	0xF9,
+	0x05,
+	0x85,
+	0x45,
+	0xC5,
+	0x25,
+	0xA5,
+	0x65,
+	0xE5,
+	0x15,
+	0x95,
+	0x55,
+	0xD5,
+	0x35,
+	0xB5,
+	0x75,
+	0xF5,
+	0x0D,
+	0x8D,
+	0x4D,
+	0xCD,
+	0x2D,
+	0xAD,
+	0x6D,
+	0xED,
+	0x1D,
+	0x9D,
+	0x5D,
+	0xDD,
+	0x3D,
+	0xBD,
+	0x7D,
+	0xFD,
+	0x03,
+	0x83,
+	0x43,
+	0xC3,
+	0x23,
+	0xA3,
+	0x63,
+	0xE3,
+	0x13,
+	0x93,
+	0x53,
+	0xD3,
+	0x33,
+	0xB3,
+	0x73,
+	0xF3,
+	0x0B,
+	0x8B,
+	0x4B,
+	0xCB,
+	0x2B,
+	0xAB,
+	0x6B,
+	0xEB,
+	0x1B,
+	0x9B,
+	0x5B,
+	0xDB,
+	0x3B,
+	0xBB,
+	0x7B,
+	0xFB,
+	0x07,
+	0x87,
+	0x47,
+	0xC7,
+	0x27,
+	0xA7,
+	0x67,
+	0xE7,
+	0x17,
+	0x97,
+	0x57,
+	0xD7,
+	0x37,
+	0xB7,
+	0x77,
+	0xF7,
+	0x0F,
+	0x8F,
+	0x4F,
+	0xCF,
+	0x2F,
+	0xAF,
+	0x6F,
+	0xEF,
+	0x1F,
+	0x9F,
+	0x5F,
+	0xDF,
+	0x3F,
+	0xBF,
+	0x7F,
+	0xFF,
+}
+
+const reverseBitsLowest = (uint64(1) << (reverseBitsMax - 1 + reverseBitsBase))
+
+/* Returns reverse(num >> BROTLI_REVERSE_BITS_BASE, BROTLI_REVERSE_BITS_MAX),
+   where reverse(value, len) is the bit-wise reversal of the len least
+   significant bits of value. */
+func reverseBits8(num uint64) uint64 {
+	return uint64(kReverseBits[num])
+}
+
+/* Stores code in table[0], table[step], table[2*step], ..., table[end] */
+/* Assumes that end is an integer multiple of step */
+func replicateValue(table []huffmanCode, step int, end int, code huffmanCode) {
+	for {
+		end -= step
+		table[end] = code
+		if end <= 0 {
+			break
+		}
+	}
+}
+
+/* Returns the table width of the next 2nd level table. |count| is the histogram
+   of bit lengths for the remaining symbols, |len| is the code length of the
+   next processed symbol. */
+func nextTableBitSize(count []uint16, len int, root_bits int) int {
+	var left int = 1 << uint(len-root_bits)
+	for len < huffmanMaxCodeLength {
+		left -= int(count[len])
+		if left <= 0 {
+			break
+		}
+		len++
+		left <<= 1
+	}
+
+	return len - root_bits
+}
+
+func buildCodeLengthsHuffmanTable(table []huffmanCode, code_lengths []byte, count []uint16) {
+	var code huffmanCode /* current table entry */ /* symbol index in original or sorted table */ /* prefix code */ /* prefix code addend */ /* step size to replicate values in current table */ /* size of current table */ /* symbols sorted by code length */
+	var symbol int
+	var key uint64
+	var key_step uint64
+	var step int
+	var table_size int
+	var sorted [codeLengthCodes]int
+	var offset [huffmanMaxCodeLengthCodeLength + 1]int
+	var bits int
+	var bits_count int
+	/* offsets in sorted table for each length */
+	assert(huffmanMaxCodeLengthCodeLength <= reverseBitsMax)
+
+	/* Generate offsets into sorted symbol table by code length. */
+	symbol = -1
+
+	bits = 1
+	var i int
+	for i = 0; i < huffmanMaxCodeLengthCodeLength; i++ {
+		symbol += int(count[bits])
+		offset[bits] = symbol
+		bits++
+	}
+
+	/* Symbols with code length 0 are placed after all other symbols. */
+	offset[0] = codeLengthCodes - 1
+
+	/* Sort symbols by length, by symbol order within each length. */
+	symbol = codeLengthCodes
+
+	for {
+		var i int
+		for i = 0; i < 6; i++ {
+			symbol--
+			sorted[offset[code_lengths[symbol]]] = symbol
+			offset[code_lengths[symbol]]--
+		}
+		if symbol == 0 {
+			break
+		}
+	}
+
+	table_size = 1 << huffmanMaxCodeLengthCodeLength
+
+	/* Special case: all symbols but one have 0 code length. */
+	if offset[0] == 0 {
+		code = constructHuffmanCode(0, uint16(sorted[0]))
+		for key = 0; key < uint64(table_size); key++ {
+			table[key] = code
+		}
+
+		return
+	}
+
+	/* Fill in table. */
+	key = 0
+
+	key_step = reverseBitsLowest
+	symbol = 0
+	bits = 1
+	step = 2
+	for {
+		for bits_count = int(count[bits]); bits_count != 0; bits_count-- {
+			code = constructHuffmanCode(byte(bits), uint16(sorted[symbol]))
+			symbol++
+			replicateValue(table[reverseBits8(key):], step, table_size, code)
+			key += key_step
+		}
+
+		step <<= 1
+		key_step >>= 1
+		bits++
+		if bits > huffmanMaxCodeLengthCodeLength {
+			break
+		}
+	}
+}
+
+func buildHuffmanTable(root_table []huffmanCode, root_bits int, symbol_lists symbolList, count []uint16) uint32 {
+	var code huffmanCode /* current table entry */ /* next available space in table */ /* current code length */ /* symbol index in original or sorted table */ /* prefix code */ /* prefix code addend */ /* 2nd level table prefix code */ /* 2nd level table prefix code addend */ /* step size to replicate values in current table */ /* key length of current table */ /* size of current table */ /* sum of root table size and 2nd level table sizes */
+	var table []huffmanCode
+	var len int
+	var symbol int
+	var key uint64
+	var key_step uint64
+	var sub_key uint64
+	var sub_key_step uint64
+	var step int
+	var table_bits int
+	var table_size int
+	var total_size int
+	var max_length int = -1
+	var bits int
+	var bits_count int
+
+	assert(root_bits <= reverseBitsMax)
+	assert(huffmanMaxCodeLength-root_bits <= reverseBitsMax)
+
+	for symbolListGet(symbol_lists, max_length) == 0xFFFF {
+		max_length--
+	}
+	max_length += huffmanMaxCodeLength + 1
+
+	table = root_table
+	table_bits = root_bits
+	table_size = 1 << uint(table_bits)
+	total_size = table_size
+
+	/* Fill in the root table. Reduce the table size to if possible,
+	   and create the repetitions by memcpy. */
+	if table_bits > max_length {
+		table_bits = max_length
+		table_size = 1 << uint(table_bits)
+	}
+
+	key = 0
+	key_step = reverseBitsLowest
+	bits = 1
+	step = 2
+	for {
+		symbol = bits - (huffmanMaxCodeLength + 1)
+		for bits_count = int(count[bits]); bits_count != 0; bits_count-- {
+			symbol = int(symbolListGet(symbol_lists, symbol))
+			code = constructHuffmanCode(byte(bits), uint16(symbol))
+			replicateValue(table[reverseBits8(key):], step, table_size, code)
+			key += key_step
+		}
+
+		step <<= 1
+		key_step >>= 1
+		bits++
+		if bits > table_bits {
+			break
+		}
+	}
+
+	/* If root_bits != table_bits then replicate to fill the remaining slots. */
+	for total_size != table_size {
+		copy(table[table_size:], table[:uint(table_size)])
+		table_size <<= 1
+	}
+
+	/* Fill in 2nd level tables and add pointers to root table. */
+	key_step = reverseBitsLowest >> uint(root_bits-1)
+
+	sub_key = reverseBitsLowest << 1
+	sub_key_step = reverseBitsLowest
+	len = root_bits + 1
+	step = 2
+	for ; len <= max_length; len++ {
+		symbol = len - (huffmanMaxCodeLength + 1)
+		for ; count[len] != 0; count[len]-- {
+			if sub_key == reverseBitsLowest<<1 {
+				table = table[table_size:]
+				table_bits = nextTableBitSize(count, int(len), root_bits)
+				table_size = 1 << uint(table_bits)
+				total_size += table_size
+				sub_key = reverseBits8(key)
+				key += key_step
+				root_table[sub_key] = constructHuffmanCode(byte(table_bits+root_bits), uint16(uint64(uint(-cap(table)+cap(root_table)))-sub_key))
+				sub_key = 0
+			}
+
+			symbol = int(symbolListGet(symbol_lists, symbol))
+			code = constructHuffmanCode(byte(len-root_bits), uint16(symbol))
+			replicateValue(table[reverseBits8(sub_key):], step, table_size, code)
+			sub_key += sub_key_step
+		}
+
+		step <<= 1
+		sub_key_step >>= 1
+	}
+
+	return uint32(total_size)
+}
+
+func buildSimpleHuffmanTable(table []huffmanCode, root_bits int, val []uint16, num_symbols uint32) uint32 {
+	var table_size uint32 = 1
+	var goal_size uint32 = 1 << uint(root_bits)
+	switch num_symbols {
+	case 0:
+		table[0] = constructHuffmanCode(0, val[0])
+
+	case 1:
+		if val[1] > val[0] {
+			table[0] = constructHuffmanCode(1, val[0])
+			table[1] = constructHuffmanCode(1, val[1])
+		} else {
+			table[0] = constructHuffmanCode(1, val[1])
+			table[1] = constructHuffmanCode(1, val[0])
+		}
+
+		table_size = 2
+
+	case 2:
+		table[0] = constructHuffmanCode(1, val[0])
+		table[2] = constructHuffmanCode(1, val[0])
+		if val[2] > val[1] {
+			table[1] = constructHuffmanCode(2, val[1])
+			table[3] = constructHuffmanCode(2, val[2])
+		} else {
+			table[1] = constructHuffmanCode(2, val[2])
+			table[3] = constructHuffmanCode(2, val[1])
+		}
+
+		table_size = 4
+
+	case 3:
+		var i int
+		var k int
+		for i = 0; i < 3; i++ {
+			for k = i + 1; k < 4; k++ {
+				if val[k] < val[i] {
+					var t uint16 = val[k]
+					val[k] = val[i]
+					val[i] = t
+				}
+			}
+		}
+
+		table[0] = constructHuffmanCode(2, val[0])
+		table[2] = constructHuffmanCode(2, val[1])
+		table[1] = constructHuffmanCode(2, val[2])
+		table[3] = constructHuffmanCode(2, val[3])
+		table_size = 4
+
+	case 4:
+		if val[3] < val[2] {
+			var t uint16 = val[3]
+			val[3] = val[2]
+			val[2] = t
+		}
+
+		table[0] = constructHuffmanCode(1, val[0])
+		table[1] = constructHuffmanCode(2, val[1])
+		table[2] = constructHuffmanCode(1, val[0])
+		table[3] = constructHuffmanCode(3, val[2])
+		table[4] = constructHuffmanCode(1, val[0])
+		table[5] = constructHuffmanCode(2, val[1])
+		table[6] = constructHuffmanCode(1, val[0])
+		table[7] = constructHuffmanCode(3, val[3])
+		table_size = 8
+	}
+
+	for table_size != goal_size {
+		copy(table[table_size:], table[:uint(table_size)])
+		table_size <<= 1
+	}
+
+	return goal_size
+}

vendor/github.com/andybalholm/brotli/literal_cost.go

@@ -0,0 +1,182 @@
+package brotli
+
+func utf8Position(last uint, c uint, clamp uint) uint {
+	if c < 128 {
+		return 0 /* Next one is the 'Byte 1' again. */
+	} else if c >= 192 { /* Next one is the 'Byte 2' of utf-8 encoding. */
+		return brotli_min_size_t(1, clamp)
+	} else {
+		/* Let's decide over the last byte if this ends the sequence. */
+		if last < 0xE0 {
+			return 0 /* Completed two or three byte coding. */ /* Next one is the 'Byte 3' of utf-8 encoding. */
+		} else {
+			return brotli_min_size_t(2, clamp)
+		}
+	}
+}
+
+func decideMultiByteStatsLevel(pos uint, len uint, mask uint, data []byte) uint {
+	var counts = [3]uint{0} /* should be 2, but 1 compresses better. */
+	var max_utf8 uint = 1
+	var last_c uint = 0
+	var i uint
+	for i = 0; i < len; i++ {
+		var c uint = uint(data[(pos+i)&mask])
+		counts[utf8Position(last_c, c, 2)]++
+		last_c = c
+	}
+
+	if counts[2] < 500 {
+		max_utf8 = 1
+	}
+
+	if counts[1]+counts[2] < 25 {
+		max_utf8 = 0
+	}
+
+	return max_utf8
+}
+
+func estimateBitCostsForLiteralsUTF8(pos uint, len uint, mask uint, data []byte, cost []float32) {
+	var max_utf8 uint = decideMultiByteStatsLevel(pos, uint(len), mask, data)
+	/* Bootstrap histograms. */
+	var histogram = [3][256]uint{[256]uint{0}}
+	var window_half uint = 495
+	var in_window uint = brotli_min_size_t(window_half, uint(len))
+	var in_window_utf8 = [3]uint{0}
+	/* max_utf8 is 0 (normal ASCII single byte modeling),
+	   1 (for 2-byte UTF-8 modeling), or 2 (for 3-byte UTF-8 modeling). */
+
+	var i uint
+	{
+		var last_c uint = 0
+		var utf8_pos uint = 0
+		for i = 0; i < in_window; i++ {
+			var c uint = uint(data[(pos+i)&mask])
+			histogram[utf8_pos][c]++
+			in_window_utf8[utf8_pos]++
+			utf8_pos = utf8Position(last_c, c, max_utf8)
+			last_c = c
+		}
+	}
+
+	/* Compute bit costs with sliding window. */
+	for i = 0; i < len; i++ {
+		if i >= window_half {
+			var c uint
+			var last_c uint
+			if i < window_half+1 {
+				c = 0
+			} else {
+				c = uint(data[(pos+i-window_half-1)&mask])
+			}
+			if i < window_half+2 {
+				last_c = 0
+			} else {
+				last_c = uint(data[(pos+i-window_half-2)&mask])
+			}
+			/* Remove a byte in the past. */
+
+			var utf8_pos2 uint = utf8Position(last_c, c, max_utf8)
+			histogram[utf8_pos2][data[(pos+i-window_half)&mask]]--
+			in_window_utf8[utf8_pos2]--
+		}
+
+		if i+window_half < len {
+			var c uint = uint(data[(pos+i+window_half-1)&mask])
+			var last_c uint = uint(data[(pos+i+window_half-2)&mask])
+			/* Add a byte in the future. */
+
+			var utf8_pos2 uint = utf8Position(last_c, c, max_utf8)
+			histogram[utf8_pos2][data[(pos+i+window_half)&mask]]++
+			in_window_utf8[utf8_pos2]++
+		}
+		{
+			var c uint
+			var last_c uint
+			if i < 1 {
+				c = 0
+			} else {
+				c = uint(data[(pos+i-1)&mask])
+			}
+			if i < 2 {
+				last_c = 0
+			} else {
+				last_c = uint(data[(pos+i-2)&mask])
+			}
+			var utf8_pos uint = utf8Position(last_c, c, max_utf8)
+			var masked_pos uint = (pos + i) & mask
+			var histo uint = histogram[utf8_pos][data[masked_pos]]
+			var lit_cost float64
+			if histo == 0 {
+				histo = 1
+			}
+
+			lit_cost = fastLog2(in_window_utf8[utf8_pos]) - fastLog2(histo)
+			lit_cost += 0.02905
+			if lit_cost < 1.0 {
+				lit_cost *= 0.5
+				lit_cost += 0.5
+			}
+
+			/* Make the first bytes more expensive -- seems to help, not sure why.
+			   Perhaps because the entropy source is changing its properties
+			   rapidly in the beginning of the file, perhaps because the beginning
+			   of the data is a statistical "anomaly". */
+			if i < 2000 {
+				lit_cost += 0.7 - (float64(2000-i) / 2000.0 * 0.35)
+			}
+
+			cost[i] = float32(lit_cost)
+		}
+	}
+}
+
+func estimateBitCostsForLiterals(pos uint, len uint, mask uint, data []byte, cost []float32) {
+	if isMostlyUTF8(data, pos, mask, uint(len), kMinUTF8Ratio) {
+		estimateBitCostsForLiteralsUTF8(pos, uint(len), mask, data, cost)
+		return
+	} else {
+		var histogram = [256]uint{0}
+		var window_half uint = 2000
+		var in_window uint = brotli_min_size_t(window_half, uint(len))
+		var i uint
+		/* Bootstrap histogram. */
+		for i = 0; i < in_window; i++ {
+			histogram[data[(pos+i)&mask]]++
+		}
+
+		/* Compute bit costs with sliding window. */
+		for i = 0; i < len; i++ {
+			var histo uint
+			if i >= window_half {
+				/* Remove a byte in the past. */
+				histogram[data[(pos+i-window_half)&mask]]--
+
+				in_window--
+			}
+
+			if i+window_half < len {
+				/* Add a byte in the future. */
+				histogram[data[(pos+i+window_half)&mask]]++
+
+				in_window++
+			}
+
+			histo = histogram[data[(pos+i)&mask]]
+			if histo == 0 {
+				histo = 1
+			}
+			{
+				var lit_cost float64 = fastLog2(in_window) - fastLog2(histo)
+				lit_cost += 0.029
+				if lit_cost < 1.0 {
+					lit_cost *= 0.5
+					lit_cost += 0.5
+				}
+
+				cost[i] = float32(lit_cost)
+			}
+		}
+	}
+}

vendor/github.com/andybalholm/brotli/memory.go

@@ -0,0 +1,66 @@
+package brotli
+
+/* Copyright 2016 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/*
+Dynamically grows array capacity to at least the requested size
+T: data type
+A: array
+C: capacity
+R: requested size
+*/
+func brotli_ensure_capacity_uint8_t(a *[]byte, c *uint, r uint) {
+	if *c < r {
+		var new_size uint = *c
+		if new_size == 0 {
+			new_size = r
+		}
+
+		for new_size < r {
+			new_size *= 2
+		}
+
+		if cap(*a) < int(new_size) {
+			var new_array []byte = make([]byte, new_size)
+			if *c != 0 {
+				copy(new_array, (*a)[:*c])
+			}
+
+			*a = new_array
+		} else {
+			*a = (*a)[:new_size]
+		}
+
+		*c = new_size
+	}
+}
+
+func brotli_ensure_capacity_uint32_t(a *[]uint32, c *uint, r uint) {
+	var new_array []uint32
+	if *c < r {
+		var new_size uint = *c
+		if new_size == 0 {
+			new_size = r
+		}
+
+		for new_size < r {
+			new_size *= 2
+		}
+
+		if cap(*a) < int(new_size) {
+			new_array = make([]uint32, new_size)
+			if *c != 0 {
+				copy(new_array, (*a)[:*c])
+			}
+
+			*a = new_array
+		} else {
+			*a = (*a)[:new_size]
+		}
+		*c = new_size
+	}
+}

vendor/github.com/andybalholm/brotli/metablock.go

@@ -0,0 +1,574 @@
+package brotli
+
+import (
+	"sync"
+)
+
+/* Copyright 2014 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Algorithms for distributing the literals and commands of a metablock between
+   block types and contexts. */
+
+type metaBlockSplit struct {
+	literal_split             blockSplit
+	command_split             blockSplit
+	distance_split            blockSplit
+	literal_context_map       []uint32
+	literal_context_map_size  uint
+	distance_context_map      []uint32
+	distance_context_map_size uint
+	literal_histograms        []histogramLiteral
+	literal_histograms_size   uint
+	command_histograms        []histogramCommand
+	command_histograms_size   uint
+	distance_histograms       []histogramDistance
+	distance_histograms_size  uint
+}
+
+var metaBlockPool sync.Pool
+
+func getMetaBlockSplit() *metaBlockSplit {
+	mb, _ := metaBlockPool.Get().(*metaBlockSplit)
+
+	if mb == nil {
+		mb = &metaBlockSplit{}
+	} else {
+		initBlockSplit(&mb.literal_split)
+		initBlockSplit(&mb.command_split)
+		initBlockSplit(&mb.distance_split)
+		mb.literal_context_map = mb.literal_context_map[:0]
+		mb.literal_context_map_size = 0
+		mb.distance_context_map = mb.distance_context_map[:0]
+		mb.distance_context_map_size = 0
+		mb.literal_histograms = mb.literal_histograms[:0]
+		mb.command_histograms = mb.command_histograms[:0]
+		mb.distance_histograms = mb.distance_histograms[:0]
+	}
+	return mb
+}
+
+func freeMetaBlockSplit(mb *metaBlockSplit) {
+	metaBlockPool.Put(mb)
+}
+
+func initDistanceParams(params *encoderParams, npostfix uint32, ndirect uint32) {
+	var dist_params *distanceParams = &params.dist
+	var alphabet_size uint32
+	var max_distance uint32
+
+	dist_params.distance_postfix_bits = npostfix
+	dist_params.num_direct_distance_codes = ndirect
+
+	alphabet_size = uint32(distanceAlphabetSize(uint(npostfix), uint(ndirect), maxDistanceBits))
+	max_distance = ndirect + (1 << (maxDistanceBits + npostfix + 2)) - (1 << (npostfix + 2))
+
+	if params.large_window {
+		var bound = [maxNpostfix + 1]uint32{0, 4, 12, 28}
+		var postfix uint32 = 1 << npostfix
+		alphabet_size = uint32(distanceAlphabetSize(uint(npostfix), uint(ndirect), largeMaxDistanceBits))
+
+		/* The maximum distance is set so that no distance symbol used can encode
+		   a distance larger than BROTLI_MAX_ALLOWED_DISTANCE with all
+		   its extra bits set. */
+		if ndirect < bound[npostfix] {
+			max_distance = maxAllowedDistance - (bound[npostfix] - ndirect)
+		} else if ndirect >= bound[npostfix]+postfix {
+			max_distance = (3 << 29) - 4 + (ndirect - bound[npostfix])
+		} else {
+			max_distance = maxAllowedDistance
+		}
+	}
+
+	dist_params.alphabet_size = alphabet_size
+	dist_params.max_distance = uint(max_distance)
+}
+
+func recomputeDistancePrefixes(cmds []command, orig_params *distanceParams, new_params *distanceParams) {
+	if orig_params.distance_postfix_bits == new_params.distance_postfix_bits && orig_params.num_direct_distance_codes == new_params.num_direct_distance_codes {
+		return
+	}
+
+	for i := range cmds {
+		var cmd *command = &cmds[i]
+		if commandCopyLen(cmd) != 0 && cmd.cmd_prefix_ >= 128 {
+			prefixEncodeCopyDistance(uint(commandRestoreDistanceCode(cmd, orig_params)), uint(new_params.num_direct_distance_codes), uint(new_params.distance_postfix_bits), &cmd.dist_prefix_, &cmd.dist_extra_)
+		}
+	}
+}
+
+func computeDistanceCost(cmds []command, orig_params *distanceParams, new_params *distanceParams, cost *float64) bool {
+	var equal_params bool = false
+	var dist_prefix uint16
+	var dist_extra uint32
+	var extra_bits float64 = 0.0
+	var histo histogramDistance
+	histogramClearDistance(&histo)
+
+	if orig_params.distance_postfix_bits == new_params.distance_postfix_bits && orig_params.num_direct_distance_codes == new_params.num_direct_distance_codes {
+		equal_params = true
+	}
+
+	for i := range cmds {
+		cmd := &cmds[i]
+		if commandCopyLen(cmd) != 0 && cmd.cmd_prefix_ >= 128 {
+			if equal_params {
+				dist_prefix = cmd.dist_prefix_
+			} else {
+				var distance uint32 = commandRestoreDistanceCode(cmd, orig_params)
+				if distance > uint32(new_params.max_distance) {
+					return false
+				}
+
+				prefixEncodeCopyDistance(uint(distance), uint(new_params.num_direct_distance_codes), uint(new_params.distance_postfix_bits), &dist_prefix, &dist_extra)
+			}
+
+			histogramAddDistance(&histo, uint(dist_prefix)&0x3FF)
+			extra_bits += float64(dist_prefix >> 10)
+		}
+	}
+
+	*cost = populationCostDistance(&histo) + extra_bits
+	return true
+}
+
+var buildMetaBlock_kMaxNumberOfHistograms uint = 256
+
+func buildMetaBlock(ringbuffer []byte, pos uint, mask uint, params *encoderParams, prev_byte byte, prev_byte2 byte, cmds []command, literal_context_mode int, mb *metaBlockSplit) {
+	var distance_histograms []histogramDistance
+	var literal_histograms []histogramLiteral
+	var literal_context_modes []int = nil
+	var literal_histograms_size uint
+	var distance_histograms_size uint
+	var i uint
+	var literal_context_multiplier uint = 1
+	var npostfix uint32
+	var ndirect_msb uint32 = 0
+	var check_orig bool = true
+	var best_dist_cost float64 = 1e99
+	var orig_params encoderParams = *params
+	/* Histogram ids need to fit in one byte. */
+
+	var new_params encoderParams = *params
+
+	for npostfix = 0; npostfix <= maxNpostfix; npostfix++ {
+		for ; ndirect_msb < 16; ndirect_msb++ {
+			var ndirect uint32 = ndirect_msb << npostfix
+			var skip bool
+			var dist_cost float64
+			initDistanceParams(&new_params, npostfix, ndirect)
+			if npostfix == orig_params.dist.distance_postfix_bits && ndirect == orig_params.dist.num_direct_distance_codes {
+				check_orig = false
+			}
+
+			skip = !computeDistanceCost(cmds, &orig_params.dist, &new_params.dist, &dist_cost)
+			if skip || (dist_cost > best_dist_cost) {
+				break
+			}
+
+			best_dist_cost = dist_cost
+			params.dist = new_params.dist
+		}
+
+		if ndirect_msb > 0 {
+			ndirect_msb--
+		}
+		ndirect_msb /= 2
+	}
+
+	if check_orig {
+		var dist_cost float64
+		computeDistanceCost(cmds, &orig_params.dist, &orig_params.dist, &dist_cost)
+		if dist_cost < best_dist_cost {
+			/* NB: currently unused; uncomment when more param tuning is added. */
+			/* best_dist_cost = dist_cost; */
+			params.dist = orig_params.dist
+		}
+	}
+
+	recomputeDistancePrefixes(cmds, &orig_params.dist, &params.dist)
+
+	splitBlock(cmds, ringbuffer, pos, mask, params, &mb.literal_split, &mb.command_split, &mb.distance_split)
+
+	if !params.disable_literal_context_modeling {
+		literal_context_multiplier = 1 << literalContextBits
+		literal_context_modes = make([]int, (mb.literal_split.num_types))
+		for i = 0; i < mb.literal_split.num_types; i++ {
+			literal_context_modes[i] = literal_context_mode
+		}
+	}
+
+	literal_histograms_size = mb.literal_split.num_types * literal_context_multiplier
+	literal_histograms = make([]histogramLiteral, literal_histograms_size)
+	clearHistogramsLiteral(literal_histograms, literal_histograms_size)
+
+	distance_histograms_size = mb.distance_split.num_types << distanceContextBits
+	distance_histograms = make([]histogramDistance, distance_histograms_size)
+	clearHistogramsDistance(distance_histograms, distance_histograms_size)
+
+	mb.command_histograms_size = mb.command_split.num_types
+	if cap(mb.command_histograms) < int(mb.command_histograms_size) {
+		mb.command_histograms = make([]histogramCommand, (mb.command_histograms_size))
+	} else {
+		mb.command_histograms = mb.command_histograms[:mb.command_histograms_size]
+	}
+	clearHistogramsCommand(mb.command_histograms, mb.command_histograms_size)
+
+	buildHistogramsWithContext(cmds, &mb.literal_split, &mb.command_split, &mb.distance_split, ringbuffer, pos, mask, prev_byte, prev_byte2, literal_context_modes, literal_histograms, mb.command_histograms, distance_histograms)
+	literal_context_modes = nil
+
+	mb.literal_context_map_size = mb.literal_split.num_types << literalContextBits
+	if cap(mb.literal_context_map) < int(mb.literal_context_map_size) {
+		mb.literal_context_map = make([]uint32, (mb.literal_context_map_size))
+	} else {
+		mb.literal_context_map = mb.literal_context_map[:mb.literal_context_map_size]
+	}
+
+	mb.literal_histograms_size = mb.literal_context_map_size
+	if cap(mb.literal_histograms) < int(mb.literal_histograms_size) {
+		mb.literal_histograms = make([]histogramLiteral, (mb.literal_histograms_size))
+	} else {
+		mb.literal_histograms = mb.literal_histograms[:mb.literal_histograms_size]
+	}
+
+	clusterHistogramsLiteral(literal_histograms, literal_histograms_size, buildMetaBlock_kMaxNumberOfHistograms, mb.literal_histograms, &mb.literal_histograms_size, mb.literal_context_map)
+	literal_histograms = nil
+
+	if params.disable_literal_context_modeling {
+		/* Distribute assignment to all contexts. */
+		for i = mb.literal_split.num_types; i != 0; {
+			var j uint = 0
+			i--
+			for ; j < 1<<literalContextBits; j++ {
+				mb.literal_context_map[(i<<literalContextBits)+j] = mb.literal_context_map[i]
+			}
+		}
+	}
+
+	mb.distance_context_map_size = mb.distance_split.num_types << distanceContextBits
+	if cap(mb.distance_context_map) < int(mb.distance_context_map_size) {
+		mb.distance_context_map = make([]uint32, (mb.distance_context_map_size))
+	} else {
+		mb.distance_context_map = mb.distance_context_map[:mb.distance_context_map_size]
+	}
+
+	mb.distance_histograms_size = mb.distance_context_map_size
+	if cap(mb.distance_histograms) < int(mb.distance_histograms_size) {
+		mb.distance_histograms = make([]histogramDistance, (mb.distance_histograms_size))
+	} else {
+		mb.distance_histograms = mb.distance_histograms[:mb.distance_histograms_size]
+	}
+
+	clusterHistogramsDistance(distance_histograms, mb.distance_context_map_size, buildMetaBlock_kMaxNumberOfHistograms, mb.distance_histograms, &mb.distance_histograms_size, mb.distance_context_map)
+	distance_histograms = nil
+}
+
+const maxStaticContexts = 13
+
+/* Greedy block splitter for one block category (literal, command or distance).
+   Gathers histograms for all context buckets. */
+type contextBlockSplitter struct {
+	alphabet_size_     uint
+	num_contexts_      uint
+	max_block_types_   uint
+	min_block_size_    uint
+	split_threshold_   float64
+	num_blocks_        uint
+	split_             *blockSplit
+	histograms_        []histogramLiteral
+	histograms_size_   *uint
+	target_block_size_ uint
+	block_size_        uint
+	curr_histogram_ix_ uint
+	last_histogram_ix_ [2]uint
+	last_entropy_      [2 * maxStaticContexts]float64
+	merge_last_count_  uint
+}
+
+func initContextBlockSplitter(self *contextBlockSplitter, alphabet_size uint, num_contexts uint, min_block_size uint, split_threshold float64, num_symbols uint, split *blockSplit, histograms *[]histogramLiteral, histograms_size *uint) {
+	var max_num_blocks uint = num_symbols/min_block_size + 1
+	var max_num_types uint
+	assert(num_contexts <= maxStaticContexts)
+
+	self.alphabet_size_ = alphabet_size
+	self.num_contexts_ = num_contexts
+	self.max_block_types_ = maxNumberOfBlockTypes / num_contexts
+	self.min_block_size_ = min_block_size
+	self.split_threshold_ = split_threshold
+	self.num_blocks_ = 0
+	self.split_ = split
+	self.histograms_size_ = histograms_size
+	self.target_block_size_ = min_block_size
+	self.block_size_ = 0
+	self.curr_histogram_ix_ = 0
+	self.merge_last_count_ = 0
+
+	/* We have to allocate one more histogram than the maximum number of block
+	   types for the current histogram when the meta-block is too big. */
+	max_num_types = brotli_min_size_t(max_num_blocks, self.max_block_types_+1)
+
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, max_num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, max_num_blocks)
+	split.num_blocks = max_num_blocks
+	*histograms_size = max_num_types * num_contexts
+	if histograms == nil || cap(*histograms) < int(*histograms_size) {
+		*histograms = make([]histogramLiteral, (*histograms_size))
+	} else {
+		*histograms = (*histograms)[:*histograms_size]
+	}
+	self.histograms_ = *histograms
+
+	/* Clear only current histogram. */
+	clearHistogramsLiteral(self.histograms_[0:], num_contexts)
+
+	self.last_histogram_ix_[1] = 0
+	self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+}
+
+/* Does either of three things:
+   (1) emits the current block with a new block type;
+   (2) emits the current block with the type of the second last block;
+   (3) merges the current block with the last block. */
+func contextBlockSplitterFinishBlock(self *contextBlockSplitter, is_final bool) {
+	var split *blockSplit = self.split_
+	var num_contexts uint = self.num_contexts_
+	var last_entropy []float64 = self.last_entropy_[:]
+	var histograms []histogramLiteral = self.histograms_
+
+	if self.block_size_ < self.min_block_size_ {
+		self.block_size_ = self.min_block_size_
+	}
+
+	if self.num_blocks_ == 0 {
+		var i uint
+
+		/* Create first block. */
+		split.lengths[0] = uint32(self.block_size_)
+
+		split.types[0] = 0
+
+		for i = 0; i < num_contexts; i++ {
+			last_entropy[i] = bitsEntropy(histograms[i].data_[:], self.alphabet_size_)
+			last_entropy[num_contexts+i] = last_entropy[i]
+		}
+
+		self.num_blocks_++
+		split.num_types++
+		self.curr_histogram_ix_ += num_contexts
+		if self.curr_histogram_ix_ < *self.histograms_size_ {
+			clearHistogramsLiteral(self.histograms_[self.curr_histogram_ix_:], self.num_contexts_)
+		}
+
+		self.block_size_ = 0
+	} else if self.block_size_ > 0 {
+		var entropy [maxStaticContexts]float64
+		var combined_histo []histogramLiteral = make([]histogramLiteral, (2 * num_contexts))
+		var combined_entropy [2 * maxStaticContexts]float64
+		var diff = [2]float64{0.0}
+		/* Try merging the set of histograms for the current block type with the
+		   respective set of histograms for the last and second last block types.
+		   Decide over the split based on the total reduction of entropy across
+		   all contexts. */
+
+		var i uint
+		for i = 0; i < num_contexts; i++ {
+			var curr_histo_ix uint = self.curr_histogram_ix_ + i
+			var j uint
+			entropy[i] = bitsEntropy(histograms[curr_histo_ix].data_[:], self.alphabet_size_)
+			for j = 0; j < 2; j++ {
+				var jx uint = j*num_contexts + i
+				var last_histogram_ix uint = self.last_histogram_ix_[j] + i
+				combined_histo[jx] = histograms[curr_histo_ix]
+				histogramAddHistogramLiteral(&combined_histo[jx], &histograms[last_histogram_ix])
+				combined_entropy[jx] = bitsEntropy(combined_histo[jx].data_[0:], self.alphabet_size_)
+				diff[j] += combined_entropy[jx] - entropy[i] - last_entropy[jx]
+			}
+		}
+
+		if split.num_types < self.max_block_types_ && diff[0] > self.split_threshold_ && diff[1] > self.split_threshold_ {
+			/* Create new block. */
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+
+			split.types[self.num_blocks_] = byte(split.num_types)
+			self.last_histogram_ix_[1] = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = split.num_types * num_contexts
+			for i = 0; i < num_contexts; i++ {
+				last_entropy[num_contexts+i] = last_entropy[i]
+				last_entropy[i] = entropy[i]
+			}
+
+			self.num_blocks_++
+			split.num_types++
+			self.curr_histogram_ix_ += num_contexts
+			if self.curr_histogram_ix_ < *self.histograms_size_ {
+				clearHistogramsLiteral(self.histograms_[self.curr_histogram_ix_:], self.num_contexts_)
+			}
+
+			self.block_size_ = 0
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else if diff[1] < diff[0]-20.0 {
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+			split.types[self.num_blocks_] = split.types[self.num_blocks_-2]
+			/* Combine this block with second last block. */
+
+			var tmp uint = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+			self.last_histogram_ix_[1] = tmp
+			for i = 0; i < num_contexts; i++ {
+				histograms[self.last_histogram_ix_[0]+i] = combined_histo[num_contexts+i]
+				last_entropy[num_contexts+i] = last_entropy[i]
+				last_entropy[i] = combined_entropy[num_contexts+i]
+				histogramClearLiteral(&histograms[self.curr_histogram_ix_+i])
+			}
+
+			self.num_blocks_++
+			self.block_size_ = 0
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else {
+			/* Combine this block with last block. */
+			split.lengths[self.num_blocks_-1] += uint32(self.block_size_)
+
+			for i = 0; i < num_contexts; i++ {
+				histograms[self.last_histogram_ix_[0]+i] = combined_histo[i]
+				last_entropy[i] = combined_entropy[i]
+				if split.num_types == 1 {
+					last_entropy[num_contexts+i] = last_entropy[i]
+				}
+
+				histogramClearLiteral(&histograms[self.curr_histogram_ix_+i])
+			}
+
+			self.block_size_ = 0
+			self.merge_last_count_++
+			if self.merge_last_count_ > 1 {
+				self.target_block_size_ += self.min_block_size_
+			}
+		}
+
+		combined_histo = nil
+	}
+
+	if is_final {
+		*self.histograms_size_ = split.num_types * num_contexts
+		split.num_blocks = self.num_blocks_
+	}
+}
+
+/* Adds the next symbol to the current block type and context. When the
+   current block reaches the target size, decides on merging the block. */
+func contextBlockSplitterAddSymbol(self *contextBlockSplitter, symbol uint, context uint) {
+	histogramAddLiteral(&self.histograms_[self.curr_histogram_ix_+context], symbol)
+	self.block_size_++
+	if self.block_size_ == self.target_block_size_ {
+		contextBlockSplitterFinishBlock(self, false) /* is_final = */
+	}
+}
+
+func mapStaticContexts(num_contexts uint, static_context_map []uint32, mb *metaBlockSplit) {
+	var i uint
+	mb.literal_context_map_size = mb.literal_split.num_types << literalContextBits
+	if cap(mb.literal_context_map) < int(mb.literal_context_map_size) {
+		mb.literal_context_map = make([]uint32, (mb.literal_context_map_size))
+	} else {
+		mb.literal_context_map = mb.literal_context_map[:mb.literal_context_map_size]
+	}
+
+	for i = 0; i < mb.literal_split.num_types; i++ {
+		var offset uint32 = uint32(i * num_contexts)
+		var j uint
+		for j = 0; j < 1<<literalContextBits; j++ {
+			mb.literal_context_map[(i<<literalContextBits)+j] = offset + static_context_map[j]
+		}
+	}
+}
+
+func buildMetaBlockGreedyInternal(ringbuffer []byte, pos uint, mask uint, prev_byte byte, prev_byte2 byte, literal_context_lut contextLUT, num_contexts uint, static_context_map []uint32, commands []command, mb *metaBlockSplit) {
+	var lit_blocks struct {
+		plain blockSplitterLiteral
+		ctx   contextBlockSplitter
+	}
+	var cmd_blocks blockSplitterCommand
+	var dist_blocks blockSplitterDistance
+	var num_literals uint = 0
+	for i := range commands {
+		num_literals += uint(commands[i].insert_len_)
+	}
+
+	if num_contexts == 1 {
+		initBlockSplitterLiteral(&lit_blocks.plain, 256, 512, 400.0, num_literals, &mb.literal_split, &mb.literal_histograms, &mb.literal_histograms_size)
+	} else {
+		initContextBlockSplitter(&lit_blocks.ctx, 256, num_contexts, 512, 400.0, num_literals, &mb.literal_split, &mb.literal_histograms, &mb.literal_histograms_size)
+	}
+
+	initBlockSplitterCommand(&cmd_blocks, numCommandSymbols, 1024, 500.0, uint(len(commands)), &mb.command_split, &mb.command_histograms, &mb.command_histograms_size)
+	initBlockSplitterDistance(&dist_blocks, 64, 512, 100.0, uint(len(commands)), &mb.distance_split, &mb.distance_histograms, &mb.distance_histograms_size)
+
+	for _, cmd := range commands {
+		var j uint
+		blockSplitterAddSymbolCommand(&cmd_blocks, uint(cmd.cmd_prefix_))
+		for j = uint(cmd.insert_len_); j != 0; j-- {
+			var literal byte = ringbuffer[pos&mask]
+			if num_contexts == 1 {
+				blockSplitterAddSymbolLiteral(&lit_blocks.plain, uint(literal))
+			} else {
+				var context uint = uint(getContext(prev_byte, prev_byte2, literal_context_lut))
+				contextBlockSplitterAddSymbol(&lit_blocks.ctx, uint(literal), uint(static_context_map[context]))
+			}
+
+			prev_byte2 = prev_byte
+			prev_byte = literal
+			pos++
+		}
+
+		pos += uint(commandCopyLen(&cmd))
+		if commandCopyLen(&cmd) != 0 {
+			prev_byte2 = ringbuffer[(pos-2)&mask]
+			prev_byte = ringbuffer[(pos-1)&mask]
+			if cmd.cmd_prefix_ >= 128 {
+				blockSplitterAddSymbolDistance(&dist_blocks, uint(cmd.dist_prefix_)&0x3FF)
+			}
+		}
+	}
+
+	if num_contexts == 1 {
+		blockSplitterFinishBlockLiteral(&lit_blocks.plain, true) /* is_final = */
+	} else {
+		contextBlockSplitterFinishBlock(&lit_blocks.ctx, true) /* is_final = */
+	}
+
+	blockSplitterFinishBlockCommand(&cmd_blocks, true)   /* is_final = */
+	blockSplitterFinishBlockDistance(&dist_blocks, true) /* is_final = */
+
+	if num_contexts > 1 {
+		mapStaticContexts(num_contexts, static_context_map, mb)
+	}
+}
+
+func buildMetaBlockGreedy(ringbuffer []byte, pos uint, mask uint, prev_byte byte, prev_byte2 byte, literal_context_lut contextLUT, num_contexts uint, static_context_map []uint32, commands []command, mb *metaBlockSplit) {
+	if num_contexts == 1 {
+		buildMetaBlockGreedyInternal(ringbuffer, pos, mask, prev_byte, prev_byte2, literal_context_lut, 1, nil, commands, mb)
+	} else {
+		buildMetaBlockGreedyInternal(ringbuffer, pos, mask, prev_byte, prev_byte2, literal_context_lut, num_contexts, static_context_map, commands, mb)
+	}
+}
+
+func optimizeHistograms(num_distance_codes uint32, mb *metaBlockSplit) {
+	var good_for_rle [numCommandSymbols]byte
+	var i uint
+	for i = 0; i < mb.literal_histograms_size; i++ {
+		optimizeHuffmanCountsForRLE(256, mb.literal_histograms[i].data_[:], good_for_rle[:])
+	}
+
+	for i = 0; i < mb.command_histograms_size; i++ {
+		optimizeHuffmanCountsForRLE(numCommandSymbols, mb.command_histograms[i].data_[:], good_for_rle[:])
+	}
+
+	for i = 0; i < mb.distance_histograms_size; i++ {
+		optimizeHuffmanCountsForRLE(uint(num_distance_codes), mb.distance_histograms[i].data_[:], good_for_rle[:])
+	}
+}

vendor/github.com/andybalholm/brotli/metablock_command.go

@@ -0,0 +1,165 @@
+package brotli
+
+/* Copyright 2015 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Greedy block splitter for one block category (literal, command or distance).
+ */
+type blockSplitterCommand struct {
+	alphabet_size_     uint
+	min_block_size_    uint
+	split_threshold_   float64
+	num_blocks_        uint
+	split_             *blockSplit
+	histograms_        []histogramCommand
+	histograms_size_   *uint
+	target_block_size_ uint
+	block_size_        uint
+	curr_histogram_ix_ uint
+	last_histogram_ix_ [2]uint
+	last_entropy_      [2]float64
+	merge_last_count_  uint
+}
+
+func initBlockSplitterCommand(self *blockSplitterCommand, alphabet_size uint, min_block_size uint, split_threshold float64, num_symbols uint, split *blockSplit, histograms *[]histogramCommand, histograms_size *uint) {
+	var max_num_blocks uint = num_symbols/min_block_size + 1
+	var max_num_types uint = brotli_min_size_t(max_num_blocks, maxNumberOfBlockTypes+1)
+	/* We have to allocate one more histogram than the maximum number of block
+	   types for the current histogram when the meta-block is too big. */
+	self.alphabet_size_ = alphabet_size
+
+	self.min_block_size_ = min_block_size
+	self.split_threshold_ = split_threshold
+	self.num_blocks_ = 0
+	self.split_ = split
+	self.histograms_size_ = histograms_size
+	self.target_block_size_ = min_block_size
+	self.block_size_ = 0
+	self.curr_histogram_ix_ = 0
+	self.merge_last_count_ = 0
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, max_num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, max_num_blocks)
+	self.split_.num_blocks = max_num_blocks
+	*histograms_size = max_num_types
+	if histograms == nil || cap(*histograms) < int(*histograms_size) {
+		*histograms = make([]histogramCommand, (*histograms_size))
+	} else {
+		*histograms = (*histograms)[:*histograms_size]
+	}
+	self.histograms_ = *histograms
+
+	/* Clear only current histogram. */
+	histogramClearCommand(&self.histograms_[0])
+
+	self.last_histogram_ix_[1] = 0
+	self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+}
+
+/* Does either of three things:
+   (1) emits the current block with a new block type;
+   (2) emits the current block with the type of the second last block;
+   (3) merges the current block with the last block. */
+func blockSplitterFinishBlockCommand(self *blockSplitterCommand, is_final bool) {
+	var split *blockSplit = self.split_
+	var last_entropy []float64 = self.last_entropy_[:]
+	var histograms []histogramCommand = self.histograms_
+	self.block_size_ = brotli_max_size_t(self.block_size_, self.min_block_size_)
+	if self.num_blocks_ == 0 {
+		/* Create first block. */
+		split.lengths[0] = uint32(self.block_size_)
+
+		split.types[0] = 0
+		last_entropy[0] = bitsEntropy(histograms[0].data_[:], self.alphabet_size_)
+		last_entropy[1] = last_entropy[0]
+		self.num_blocks_++
+		split.num_types++
+		self.curr_histogram_ix_++
+		if self.curr_histogram_ix_ < *self.histograms_size_ {
+			histogramClearCommand(&histograms[self.curr_histogram_ix_])
+		}
+		self.block_size_ = 0
+	} else if self.block_size_ > 0 {
+		var entropy float64 = bitsEntropy(histograms[self.curr_histogram_ix_].data_[:], self.alphabet_size_)
+		var combined_histo [2]histogramCommand
+		var combined_entropy [2]float64
+		var diff [2]float64
+		var j uint
+		for j = 0; j < 2; j++ {
+			var last_histogram_ix uint = self.last_histogram_ix_[j]
+			combined_histo[j] = histograms[self.curr_histogram_ix_]
+			histogramAddHistogramCommand(&combined_histo[j], &histograms[last_histogram_ix])
+			combined_entropy[j] = bitsEntropy(combined_histo[j].data_[0:], self.alphabet_size_)
+			diff[j] = combined_entropy[j] - entropy - last_entropy[j]
+		}
+
+		if split.num_types < maxNumberOfBlockTypes && diff[0] > self.split_threshold_ && diff[1] > self.split_threshold_ {
+			/* Create new block. */
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+
+			split.types[self.num_blocks_] = byte(split.num_types)
+			self.last_histogram_ix_[1] = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = uint(byte(split.num_types))
+			last_entropy[1] = last_entropy[0]
+			last_entropy[0] = entropy
+			self.num_blocks_++
+			split.num_types++
+			self.curr_histogram_ix_++
+			if self.curr_histogram_ix_ < *self.histograms_size_ {
+				histogramClearCommand(&histograms[self.curr_histogram_ix_])
+			}
+			self.block_size_ = 0
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else if diff[1] < diff[0]-20.0 {
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+			split.types[self.num_blocks_] = split.types[self.num_blocks_-2]
+			/* Combine this block with second last block. */
+
+			var tmp uint = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+			self.last_histogram_ix_[1] = tmp
+			histograms[self.last_histogram_ix_[0]] = combined_histo[1]
+			last_entropy[1] = last_entropy[0]
+			last_entropy[0] = combined_entropy[1]
+			self.num_blocks_++
+			self.block_size_ = 0
+			histogramClearCommand(&histograms[self.curr_histogram_ix_])
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else {
+			/* Combine this block with last block. */
+			split.lengths[self.num_blocks_-1] += uint32(self.block_size_)
+
+			histograms[self.last_histogram_ix_[0]] = combined_histo[0]
+			last_entropy[0] = combined_entropy[0]
+			if split.num_types == 1 {
+				last_entropy[1] = last_entropy[0]
+			}
+
+			self.block_size_ = 0
+			histogramClearCommand(&histograms[self.curr_histogram_ix_])
+			self.merge_last_count_++
+			if self.merge_last_count_ > 1 {
+				self.target_block_size_ += self.min_block_size_
+			}
+		}
+	}
+
+	if is_final {
+		*self.histograms_size_ = split.num_types
+		split.num_blocks = self.num_blocks_
+	}
+}
+
+/* Adds the next symbol to the current histogram. When the current histogram
+   reaches the target size, decides on merging the block. */
+func blockSplitterAddSymbolCommand(self *blockSplitterCommand, symbol uint) {
+	histogramAddCommand(&self.histograms_[self.curr_histogram_ix_], symbol)
+	self.block_size_++
+	if self.block_size_ == self.target_block_size_ {
+		blockSplitterFinishBlockCommand(self, false) /* is_final = */
+	}
+}

vendor/github.com/andybalholm/brotli/metablock_distance.go

@@ -0,0 +1,165 @@
+package brotli
+
+/* Copyright 2015 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Greedy block splitter for one block category (literal, command or distance).
+ */
+type blockSplitterDistance struct {
+	alphabet_size_     uint
+	min_block_size_    uint
+	split_threshold_   float64
+	num_blocks_        uint
+	split_             *blockSplit
+	histograms_        []histogramDistance
+	histograms_size_   *uint
+	target_block_size_ uint
+	block_size_        uint
+	curr_histogram_ix_ uint
+	last_histogram_ix_ [2]uint
+	last_entropy_      [2]float64
+	merge_last_count_  uint
+}
+
+func initBlockSplitterDistance(self *blockSplitterDistance, alphabet_size uint, min_block_size uint, split_threshold float64, num_symbols uint, split *blockSplit, histograms *[]histogramDistance, histograms_size *uint) {
+	var max_num_blocks uint = num_symbols/min_block_size + 1
+	var max_num_types uint = brotli_min_size_t(max_num_blocks, maxNumberOfBlockTypes+1)
+	/* We have to allocate one more histogram than the maximum number of block
+	   types for the current histogram when the meta-block is too big. */
+	self.alphabet_size_ = alphabet_size
+
+	self.min_block_size_ = min_block_size
+	self.split_threshold_ = split_threshold
+	self.num_blocks_ = 0
+	self.split_ = split
+	self.histograms_size_ = histograms_size
+	self.target_block_size_ = min_block_size
+	self.block_size_ = 0
+	self.curr_histogram_ix_ = 0
+	self.merge_last_count_ = 0
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, max_num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, max_num_blocks)
+	self.split_.num_blocks = max_num_blocks
+	*histograms_size = max_num_types
+	if histograms == nil || cap(*histograms) < int(*histograms_size) {
+		*histograms = make([]histogramDistance, *histograms_size)
+	} else {
+		*histograms = (*histograms)[:*histograms_size]
+	}
+	self.histograms_ = *histograms
+
+	/* Clear only current histogram. */
+	histogramClearDistance(&self.histograms_[0])
+
+	self.last_histogram_ix_[1] = 0
+	self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+}
+
+/* Does either of three things:
+   (1) emits the current block with a new block type;
+   (2) emits the current block with the type of the second last block;
+   (3) merges the current block with the last block. */
+func blockSplitterFinishBlockDistance(self *blockSplitterDistance, is_final bool) {
+	var split *blockSplit = self.split_
+	var last_entropy []float64 = self.last_entropy_[:]
+	var histograms []histogramDistance = self.histograms_
+	self.block_size_ = brotli_max_size_t(self.block_size_, self.min_block_size_)
+	if self.num_blocks_ == 0 {
+		/* Create first block. */
+		split.lengths[0] = uint32(self.block_size_)
+
+		split.types[0] = 0
+		last_entropy[0] = bitsEntropy(histograms[0].data_[:], self.alphabet_size_)
+		last_entropy[1] = last_entropy[0]
+		self.num_blocks_++
+		split.num_types++
+		self.curr_histogram_ix_++
+		if self.curr_histogram_ix_ < *self.histograms_size_ {
+			histogramClearDistance(&histograms[self.curr_histogram_ix_])
+		}
+		self.block_size_ = 0
+	} else if self.block_size_ > 0 {
+		var entropy float64 = bitsEntropy(histograms[self.curr_histogram_ix_].data_[:], self.alphabet_size_)
+		var combined_histo [2]histogramDistance
+		var combined_entropy [2]float64
+		var diff [2]float64
+		var j uint
+		for j = 0; j < 2; j++ {
+			var last_histogram_ix uint = self.last_histogram_ix_[j]
+			combined_histo[j] = histograms[self.curr_histogram_ix_]
+			histogramAddHistogramDistance(&combined_histo[j], &histograms[last_histogram_ix])
+			combined_entropy[j] = bitsEntropy(combined_histo[j].data_[0:], self.alphabet_size_)
+			diff[j] = combined_entropy[j] - entropy - last_entropy[j]
+		}
+
+		if split.num_types < maxNumberOfBlockTypes && diff[0] > self.split_threshold_ && diff[1] > self.split_threshold_ {
+			/* Create new block. */
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+
+			split.types[self.num_blocks_] = byte(split.num_types)
+			self.last_histogram_ix_[1] = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = uint(byte(split.num_types))
+			last_entropy[1] = last_entropy[0]
+			last_entropy[0] = entropy
+			self.num_blocks_++
+			split.num_types++
+			self.curr_histogram_ix_++
+			if self.curr_histogram_ix_ < *self.histograms_size_ {
+				histogramClearDistance(&histograms[self.curr_histogram_ix_])
+			}
+			self.block_size_ = 0
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else if diff[1] < diff[0]-20.0 {
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+			split.types[self.num_blocks_] = split.types[self.num_blocks_-2]
+			/* Combine this block with second last block. */
+
+			var tmp uint = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+			self.last_histogram_ix_[1] = tmp
+			histograms[self.last_histogram_ix_[0]] = combined_histo[1]
+			last_entropy[1] = last_entropy[0]
+			last_entropy[0] = combined_entropy[1]
+			self.num_blocks_++
+			self.block_size_ = 0
+			histogramClearDistance(&histograms[self.curr_histogram_ix_])
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else {
+			/* Combine this block with last block. */
+			split.lengths[self.num_blocks_-1] += uint32(self.block_size_)
+
+			histograms[self.last_histogram_ix_[0]] = combined_histo[0]
+			last_entropy[0] = combined_entropy[0]
+			if split.num_types == 1 {
+				last_entropy[1] = last_entropy[0]
+			}
+
+			self.block_size_ = 0
+			histogramClearDistance(&histograms[self.curr_histogram_ix_])
+			self.merge_last_count_++
+			if self.merge_last_count_ > 1 {
+				self.target_block_size_ += self.min_block_size_
+			}
+		}
+	}
+
+	if is_final {
+		*self.histograms_size_ = split.num_types
+		split.num_blocks = self.num_blocks_
+	}
+}
+
+/* Adds the next symbol to the current histogram. When the current histogram
+   reaches the target size, decides on merging the block. */
+func blockSplitterAddSymbolDistance(self *blockSplitterDistance, symbol uint) {
+	histogramAddDistance(&self.histograms_[self.curr_histogram_ix_], symbol)
+	self.block_size_++
+	if self.block_size_ == self.target_block_size_ {
+		blockSplitterFinishBlockDistance(self, false) /* is_final = */
+	}
+}

vendor/github.com/andybalholm/brotli/metablock_literal.go

@@ -0,0 +1,165 @@
+package brotli
+
+/* Copyright 2015 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Greedy block splitter for one block category (literal, command or distance).
+ */
+type blockSplitterLiteral struct {
+	alphabet_size_     uint
+	min_block_size_    uint
+	split_threshold_   float64
+	num_blocks_        uint
+	split_             *blockSplit
+	histograms_        []histogramLiteral
+	histograms_size_   *uint
+	target_block_size_ uint
+	block_size_        uint
+	curr_histogram_ix_ uint
+	last_histogram_ix_ [2]uint
+	last_entropy_      [2]float64
+	merge_last_count_  uint
+}
+
+func initBlockSplitterLiteral(self *blockSplitterLiteral, alphabet_size uint, min_block_size uint, split_threshold float64, num_symbols uint, split *blockSplit, histograms *[]histogramLiteral, histograms_size *uint) {
+	var max_num_blocks uint = num_symbols/min_block_size + 1
+	var max_num_types uint = brotli_min_size_t(max_num_blocks, maxNumberOfBlockTypes+1)
+	/* We have to allocate one more histogram than the maximum number of block
+	   types for the current histogram when the meta-block is too big. */
+	self.alphabet_size_ = alphabet_size
+
+	self.min_block_size_ = min_block_size
+	self.split_threshold_ = split_threshold
+	self.num_blocks_ = 0
+	self.split_ = split
+	self.histograms_size_ = histograms_size
+	self.target_block_size_ = min_block_size
+	self.block_size_ = 0
+	self.curr_histogram_ix_ = 0
+	self.merge_last_count_ = 0
+	brotli_ensure_capacity_uint8_t(&split.types, &split.types_alloc_size, max_num_blocks)
+	brotli_ensure_capacity_uint32_t(&split.lengths, &split.lengths_alloc_size, max_num_blocks)
+	self.split_.num_blocks = max_num_blocks
+	*histograms_size = max_num_types
+	if histograms == nil || cap(*histograms) < int(*histograms_size) {
+		*histograms = make([]histogramLiteral, *histograms_size)
+	} else {
+		*histograms = (*histograms)[:*histograms_size]
+	}
+	self.histograms_ = *histograms
+
+	/* Clear only current histogram. */
+	histogramClearLiteral(&self.histograms_[0])
+
+	self.last_histogram_ix_[1] = 0
+	self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+}
+
+/* Does either of three things:
+   (1) emits the current block with a new block type;
+   (2) emits the current block with the type of the second last block;
+   (3) merges the current block with the last block. */
+func blockSplitterFinishBlockLiteral(self *blockSplitterLiteral, is_final bool) {
+	var split *blockSplit = self.split_
+	var last_entropy []float64 = self.last_entropy_[:]
+	var histograms []histogramLiteral = self.histograms_
+	self.block_size_ = brotli_max_size_t(self.block_size_, self.min_block_size_)
+	if self.num_blocks_ == 0 {
+		/* Create first block. */
+		split.lengths[0] = uint32(self.block_size_)
+
+		split.types[0] = 0
+		last_entropy[0] = bitsEntropy(histograms[0].data_[:], self.alphabet_size_)
+		last_entropy[1] = last_entropy[0]
+		self.num_blocks_++
+		split.num_types++
+		self.curr_histogram_ix_++
+		if self.curr_histogram_ix_ < *self.histograms_size_ {
+			histogramClearLiteral(&histograms[self.curr_histogram_ix_])
+		}
+		self.block_size_ = 0
+	} else if self.block_size_ > 0 {
+		var entropy float64 = bitsEntropy(histograms[self.curr_histogram_ix_].data_[:], self.alphabet_size_)
+		var combined_histo [2]histogramLiteral
+		var combined_entropy [2]float64
+		var diff [2]float64
+		var j uint
+		for j = 0; j < 2; j++ {
+			var last_histogram_ix uint = self.last_histogram_ix_[j]
+			combined_histo[j] = histograms[self.curr_histogram_ix_]
+			histogramAddHistogramLiteral(&combined_histo[j], &histograms[last_histogram_ix])
+			combined_entropy[j] = bitsEntropy(combined_histo[j].data_[0:], self.alphabet_size_)
+			diff[j] = combined_entropy[j] - entropy - last_entropy[j]
+		}
+
+		if split.num_types < maxNumberOfBlockTypes && diff[0] > self.split_threshold_ && diff[1] > self.split_threshold_ {
+			/* Create new block. */
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+
+			split.types[self.num_blocks_] = byte(split.num_types)
+			self.last_histogram_ix_[1] = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = uint(byte(split.num_types))
+			last_entropy[1] = last_entropy[0]
+			last_entropy[0] = entropy
+			self.num_blocks_++
+			split.num_types++
+			self.curr_histogram_ix_++
+			if self.curr_histogram_ix_ < *self.histograms_size_ {
+				histogramClearLiteral(&histograms[self.curr_histogram_ix_])
+			}
+			self.block_size_ = 0
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else if diff[1] < diff[0]-20.0 {
+			split.lengths[self.num_blocks_] = uint32(self.block_size_)
+			split.types[self.num_blocks_] = split.types[self.num_blocks_-2]
+			/* Combine this block with second last block. */
+
+			var tmp uint = self.last_histogram_ix_[0]
+			self.last_histogram_ix_[0] = self.last_histogram_ix_[1]
+			self.last_histogram_ix_[1] = tmp
+			histograms[self.last_histogram_ix_[0]] = combined_histo[1]
+			last_entropy[1] = last_entropy[0]
+			last_entropy[0] = combined_entropy[1]
+			self.num_blocks_++
+			self.block_size_ = 0
+			histogramClearLiteral(&histograms[self.curr_histogram_ix_])
+			self.merge_last_count_ = 0
+			self.target_block_size_ = self.min_block_size_
+		} else {
+			/* Combine this block with last block. */
+			split.lengths[self.num_blocks_-1] += uint32(self.block_size_)
+
+			histograms[self.last_histogram_ix_[0]] = combined_histo[0]
+			last_entropy[0] = combined_entropy[0]
+			if split.num_types == 1 {
+				last_entropy[1] = last_entropy[0]
+			}
+
+			self.block_size_ = 0
+			histogramClearLiteral(&histograms[self.curr_histogram_ix_])
+			self.merge_last_count_++
+			if self.merge_last_count_ > 1 {
+				self.target_block_size_ += self.min_block_size_
+			}
+		}
+	}
+
+	if is_final {
+		*self.histograms_size_ = split.num_types
+		split.num_blocks = self.num_blocks_
+	}
+}
+
+/* Adds the next symbol to the current histogram. When the current histogram
+   reaches the target size, decides on merging the block. */
+func blockSplitterAddSymbolLiteral(self *blockSplitterLiteral, symbol uint) {
+	histogramAddLiteral(&self.histograms_[self.curr_histogram_ix_], symbol)
+	self.block_size_++
+	if self.block_size_ == self.target_block_size_ {
+		blockSplitterFinishBlockLiteral(self, false) /* is_final = */
+	}
+}

vendor/github.com/andybalholm/brotli/params.go

@@ -0,0 +1,37 @@
+package brotli
+
+/* Copyright 2017 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Parameters for the Brotli encoder with chosen quality levels. */
+type hasherParams struct {
+	type_                       int
+	bucket_bits                 int
+	block_bits                  int
+	hash_len                    int
+	num_last_distances_to_check int
+}
+
+type distanceParams struct {
+	distance_postfix_bits     uint32
+	num_direct_distance_codes uint32
+	alphabet_size             uint32
+	max_distance              uint
+}
+
+/* Encoding parameters */
+type encoderParams struct {
+	mode                             int
+	quality                          int
+	lgwin                            uint
+	lgblock                          int
+	size_hint                        uint
+	disable_literal_context_modeling bool
+	large_window                     bool
+	hasher                           hasherParams
+	dist                             distanceParams
+	dictionary                       encoderDictionary
+}

vendor/github.com/andybalholm/brotli/platform.go

@@ -0,0 +1,103 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+func brotli_min_double(a float64, b float64) float64 {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_max_double(a float64, b float64) float64 {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_min_float(a float32, b float32) float32 {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_max_float(a float32, b float32) float32 {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_min_int(a int, b int) int {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_max_int(a int, b int) int {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_min_size_t(a uint, b uint) uint {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_max_size_t(a uint, b uint) uint {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_min_uint32_t(a uint32, b uint32) uint32 {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_max_uint32_t(a uint32, b uint32) uint32 {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_min_uint8_t(a byte, b byte) byte {
+	if a < b {
+		return a
+	} else {
+		return b
+	}
+}
+
+func brotli_max_uint8_t(a byte, b byte) byte {
+	if a > b {
+		return a
+	} else {
+		return b
+	}
+}

vendor/github.com/andybalholm/brotli/prefix.go

@@ -0,0 +1,30 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Functions for encoding of integers into prefix codes the amount of extra
+   bits, and the actual values of the extra bits. */
+
+/* Here distance_code is an intermediate code, i.e. one of the special codes or
+   the actual distance increased by BROTLI_NUM_DISTANCE_SHORT_CODES - 1. */
+func prefixEncodeCopyDistance(distance_code uint, num_direct_codes uint, postfix_bits uint, code *uint16, extra_bits *uint32) {
+	if distance_code < numDistanceShortCodes+num_direct_codes {
+		*code = uint16(distance_code)
+		*extra_bits = 0
+		return
+	} else {
+		var dist uint = (uint(1) << (postfix_bits + 2)) + (distance_code - numDistanceShortCodes - num_direct_codes)
+		var bucket uint = uint(log2FloorNonZero(dist) - 1)
+		var postfix_mask uint = (1 << postfix_bits) - 1
+		var postfix uint = dist & postfix_mask
+		var prefix uint = (dist >> bucket) & 1
+		var offset uint = (2 + prefix) << bucket
+		var nbits uint = bucket - postfix_bits
+		*code = uint16(nbits<<10 | (numDistanceShortCodes + num_direct_codes + ((2*(nbits-1) + prefix) << postfix_bits) + postfix))
+		*extra_bits = uint32((dist - offset) >> postfix_bits)
+	}
+}

vendor/github.com/andybalholm/brotli/prefix_dec.go

@@ -0,0 +1,723 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+type cmdLutElement struct {
+	insert_len_extra_bits byte
+	copy_len_extra_bits   byte
+	distance_code         int8
+	context               byte
+	insert_len_offset     uint16
+	copy_len_offset       uint16
+}
+
+var kCmdLut = [numCommandSymbols]cmdLutElement{
+	cmdLutElement{0x00, 0x00, 0, 0x00, 0x0000, 0x0002},
+	cmdLutElement{0x00, 0x00, 0, 0x01, 0x0000, 0x0003},
+	cmdLutElement{0x00, 0x00, 0, 0x02, 0x0000, 0x0004},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0000, 0x0005},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0000, 0x0006},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0000, 0x0007},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0000, 0x0008},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0000, 0x0009},
+	cmdLutElement{0x00, 0x00, 0, 0x00, 0x0001, 0x0002},
+	cmdLutElement{0x00, 0x00, 0, 0x01, 0x0001, 0x0003},
+	cmdLutElement{0x00, 0x00, 0, 0x02, 0x0001, 0x0004},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0001, 0x0005},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0001, 0x0006},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0001, 0x0007},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0001, 0x0008},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0001, 0x0009},
+	cmdLutElement{0x00, 0x00, 0, 0x00, 0x0002, 0x0002},
+	cmdLutElement{0x00, 0x00, 0, 0x01, 0x0002, 0x0003},
+	cmdLutElement{0x00, 0x00, 0, 0x02, 0x0002, 0x0004},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0002, 0x0005},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0002, 0x0006},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0002, 0x0007},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0002, 0x0008},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0002, 0x0009},
+	cmdLutElement{0x00, 0x00, 0, 0x00, 0x0003, 0x0002},
+	cmdLutElement{0x00, 0x00, 0, 0x01, 0x0003, 0x0003},
+	cmdLutElement{0x00, 0x00, 0, 0x02, 0x0003, 0x0004},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0003, 0x0005},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0003, 0x0006},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0003, 0x0007},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0003, 0x0008},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0003, 0x0009},
+	cmdLutElement{0x00, 0x00, 0, 0x00, 0x0004, 0x0002},
+	cmdLutElement{0x00, 0x00, 0, 0x01, 0x0004, 0x0003},
+	cmdLutElement{0x00, 0x00, 0, 0x02, 0x0004, 0x0004},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0004, 0x0005},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0004, 0x0006},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0004, 0x0007},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0004, 0x0008},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0004, 0x0009},
+	cmdLutElement{0x00, 0x00, 0, 0x00, 0x0005, 0x0002},
+	cmdLutElement{0x00, 0x00, 0, 0x01, 0x0005, 0x0003},
+	cmdLutElement{0x00, 0x00, 0, 0x02, 0x0005, 0x0004},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0005, 0x0005},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0005, 0x0006},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0005, 0x0007},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0005, 0x0008},
+	cmdLutElement{0x00, 0x00, 0, 0x03, 0x0005, 0x0009},
+	cmdLutElement{0x01, 0x00, 0, 0x00, 0x0006, 0x0002},
+	cmdLutElement{0x01, 0x00, 0, 0x01, 0x0006, 0x0003},
+	cmdLutElement{0x01, 0x00, 0, 0x02, 0x0006, 0x0004},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0006, 0x0005},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0006, 0x0006},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0006, 0x0007},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0006, 0x0008},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0006, 0x0009},
+	cmdLutElement{0x01, 0x00, 0, 0x00, 0x0008, 0x0002},
+	cmdLutElement{0x01, 0x00, 0, 0x01, 0x0008, 0x0003},
+	cmdLutElement{0x01, 0x00, 0, 0x02, 0x0008, 0x0004},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0008, 0x0005},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0008, 0x0006},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0008, 0x0007},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0008, 0x0008},
+	cmdLutElement{0x01, 0x00, 0, 0x03, 0x0008, 0x0009},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0000, 0x000a},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0000, 0x000c},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0000, 0x000e},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0000, 0x0012},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0000, 0x0016},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0000, 0x001e},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0000, 0x0026},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0000, 0x0036},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0001, 0x000a},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0001, 0x000c},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0001, 0x000e},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0001, 0x0012},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0001, 0x0016},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0001, 0x001e},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0001, 0x0026},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0001, 0x0036},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0002, 0x000a},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0002, 0x000c},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0002, 0x000e},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0002, 0x0012},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0002, 0x0016},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0002, 0x001e},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0002, 0x0026},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0002, 0x0036},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0003, 0x000a},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0003, 0x000c},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0003, 0x000e},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0003, 0x0012},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0003, 0x0016},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0003, 0x001e},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0003, 0x0026},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0003, 0x0036},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0004, 0x000a},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0004, 0x000c},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0004, 0x000e},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0004, 0x0012},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0004, 0x0016},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0004, 0x001e},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0004, 0x0026},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0004, 0x0036},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0005, 0x000a},
+	cmdLutElement{0x00, 0x01, 0, 0x03, 0x0005, 0x000c},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0005, 0x000e},
+	cmdLutElement{0x00, 0x02, 0, 0x03, 0x0005, 0x0012},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0005, 0x0016},
+	cmdLutElement{0x00, 0x03, 0, 0x03, 0x0005, 0x001e},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0005, 0x0026},
+	cmdLutElement{0x00, 0x04, 0, 0x03, 0x0005, 0x0036},
+	cmdLutElement{0x01, 0x01, 0, 0x03, 0x0006, 0x000a},
+	cmdLutElement{0x01, 0x01, 0, 0x03, 0x0006, 0x000c},
+	cmdLutElement{0x01, 0x02, 0, 0x03, 0x0006, 0x000e},
+	cmdLutElement{0x01, 0x02, 0, 0x03, 0x0006, 0x0012},
+	cmdLutElement{0x01, 0x03, 0, 0x03, 0x0006, 0x0016},
+	cmdLutElement{0x01, 0x03, 0, 0x03, 0x0006, 0x001e},
+	cmdLutElement{0x01, 0x04, 0, 0x03, 0x0006, 0x0026},
+	cmdLutElement{0x01, 0x04, 0, 0x03, 0x0006, 0x0036},
+	cmdLutElement{0x01, 0x01, 0, 0x03, 0x0008, 0x000a},
+	cmdLutElement{0x01, 0x01, 0, 0x03, 0x0008, 0x000c},
+	cmdLutElement{0x01, 0x02, 0, 0x03, 0x0008, 0x000e},
+	cmdLutElement{0x01, 0x02, 0, 0x03, 0x0008, 0x0012},
+	cmdLutElement{0x01, 0x03, 0, 0x03, 0x0008, 0x0016},
+	cmdLutElement{0x01, 0x03, 0, 0x03, 0x0008, 0x001e},
+	cmdLutElement{0x01, 0x04, 0, 0x03, 0x0008, 0x0026},
+	cmdLutElement{0x01, 0x04, 0, 0x03, 0x0008, 0x0036},
+	cmdLutElement{0x00, 0x00, -1, 0x00, 0x0000, 0x0002},
+	cmdLutElement{0x00, 0x00, -1, 0x01, 0x0000, 0x0003},
+	cmdLutElement{0x00, 0x00, -1, 0x02, 0x0000, 0x0004},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0000, 0x0005},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0000, 0x0006},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0000, 0x0007},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0000, 0x0008},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0000, 0x0009},
+	cmdLutElement{0x00, 0x00, -1, 0x00, 0x0001, 0x0002},
+	cmdLutElement{0x00, 0x00, -1, 0x01, 0x0001, 0x0003},
+	cmdLutElement{0x00, 0x00, -1, 0x02, 0x0001, 0x0004},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0001, 0x0005},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0001, 0x0006},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0001, 0x0007},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0001, 0x0008},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0001, 0x0009},
+	cmdLutElement{0x00, 0x00, -1, 0x00, 0x0002, 0x0002},
+	cmdLutElement{0x00, 0x00, -1, 0x01, 0x0002, 0x0003},
+	cmdLutElement{0x00, 0x00, -1, 0x02, 0x0002, 0x0004},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0002, 0x0005},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0002, 0x0006},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0002, 0x0007},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0002, 0x0008},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0002, 0x0009},
+	cmdLutElement{0x00, 0x00, -1, 0x00, 0x0003, 0x0002},
+	cmdLutElement{0x00, 0x00, -1, 0x01, 0x0003, 0x0003},
+	cmdLutElement{0x00, 0x00, -1, 0x02, 0x0003, 0x0004},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0003, 0x0005},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0003, 0x0006},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0003, 0x0007},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0003, 0x0008},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0003, 0x0009},
+	cmdLutElement{0x00, 0x00, -1, 0x00, 0x0004, 0x0002},
+	cmdLutElement{0x00, 0x00, -1, 0x01, 0x0004, 0x0003},
+	cmdLutElement{0x00, 0x00, -1, 0x02, 0x0004, 0x0004},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0004, 0x0005},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0004, 0x0006},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0004, 0x0007},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0004, 0x0008},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0004, 0x0009},
+	cmdLutElement{0x00, 0x00, -1, 0x00, 0x0005, 0x0002},
+	cmdLutElement{0x00, 0x00, -1, 0x01, 0x0005, 0x0003},
+	cmdLutElement{0x00, 0x00, -1, 0x02, 0x0005, 0x0004},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0005, 0x0005},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0005, 0x0006},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0005, 0x0007},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0005, 0x0008},
+	cmdLutElement{0x00, 0x00, -1, 0x03, 0x0005, 0x0009},
+	cmdLutElement{0x01, 0x00, -1, 0x00, 0x0006, 0x0002},
+	cmdLutElement{0x01, 0x00, -1, 0x01, 0x0006, 0x0003},
+	cmdLutElement{0x01, 0x00, -1, 0x02, 0x0006, 0x0004},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0006, 0x0005},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0006, 0x0006},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0006, 0x0007},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0006, 0x0008},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0006, 0x0009},
+	cmdLutElement{0x01, 0x00, -1, 0x00, 0x0008, 0x0002},
+	cmdLutElement{0x01, 0x00, -1, 0x01, 0x0008, 0x0003},
+	cmdLutElement{0x01, 0x00, -1, 0x02, 0x0008, 0x0004},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0008, 0x0005},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0008, 0x0006},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0008, 0x0007},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0008, 0x0008},
+	cmdLutElement{0x01, 0x00, -1, 0x03, 0x0008, 0x0009},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0000, 0x000a},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0000, 0x000c},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0000, 0x000e},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0000, 0x0012},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0000, 0x0016},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0000, 0x001e},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0000, 0x0026},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0000, 0x0036},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0001, 0x000a},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0001, 0x000c},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0001, 0x000e},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0001, 0x0012},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0001, 0x0016},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0001, 0x001e},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0001, 0x0026},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0001, 0x0036},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0002, 0x000a},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0002, 0x000c},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0002, 0x000e},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0002, 0x0012},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0002, 0x0016},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0002, 0x001e},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0002, 0x0026},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0002, 0x0036},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0003, 0x000a},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0003, 0x000c},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0003, 0x000e},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0003, 0x0012},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0003, 0x0016},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0003, 0x001e},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0003, 0x0026},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0003, 0x0036},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0004, 0x000a},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0004, 0x000c},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0004, 0x000e},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0004, 0x0012},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0004, 0x0016},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0004, 0x001e},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0004, 0x0026},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0004, 0x0036},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0005, 0x000a},
+	cmdLutElement{0x00, 0x01, -1, 0x03, 0x0005, 0x000c},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0005, 0x000e},
+	cmdLutElement{0x00, 0x02, -1, 0x03, 0x0005, 0x0012},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0005, 0x0016},
+	cmdLutElement{0x00, 0x03, -1, 0x03, 0x0005, 0x001e},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0005, 0x0026},
+	cmdLutElement{0x00, 0x04, -1, 0x03, 0x0005, 0x0036},
+	cmdLutElement{0x01, 0x01, -1, 0x03, 0x0006, 0x000a},
+	cmdLutElement{0x01, 0x01, -1, 0x03, 0x0006, 0x000c},
+	cmdLutElement{0x01, 0x02, -1, 0x03, 0x0006, 0x000e},
+	cmdLutElement{0x01, 0x02, -1, 0x03, 0x0006, 0x0012},
+	cmdLutElement{0x01, 0x03, -1, 0x03, 0x0006, 0x0016},
+	cmdLutElement{0x01, 0x03, -1, 0x03, 0x0006, 0x001e},
+	cmdLutElement{0x01, 0x04, -1, 0x03, 0x0006, 0x0026},
+	cmdLutElement{0x01, 0x04, -1, 0x03, 0x0006, 0x0036},
+	cmdLutElement{0x01, 0x01, -1, 0x03, 0x0008, 0x000a},
+	cmdLutElement{0x01, 0x01, -1, 0x03, 0x0008, 0x000c},
+	cmdLutElement{0x01, 0x02, -1, 0x03, 0x0008, 0x000e},
+	cmdLutElement{0x01, 0x02, -1, 0x03, 0x0008, 0x0012},
+	cmdLutElement{0x01, 0x03, -1, 0x03, 0x0008, 0x0016},
+	cmdLutElement{0x01, 0x03, -1, 0x03, 0x0008, 0x001e},
+	cmdLutElement{0x01, 0x04, -1, 0x03, 0x0008, 0x0026},
+	cmdLutElement{0x01, 0x04, -1, 0x03, 0x0008, 0x0036},
+	cmdLutElement{0x02, 0x00, -1, 0x00, 0x000a, 0x0002},
+	cmdLutElement{0x02, 0x00, -1, 0x01, 0x000a, 0x0003},
+	cmdLutElement{0x02, 0x00, -1, 0x02, 0x000a, 0x0004},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000a, 0x0005},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000a, 0x0006},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000a, 0x0007},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000a, 0x0008},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000a, 0x0009},
+	cmdLutElement{0x02, 0x00, -1, 0x00, 0x000e, 0x0002},
+	cmdLutElement{0x02, 0x00, -1, 0x01, 0x000e, 0x0003},
+	cmdLutElement{0x02, 0x00, -1, 0x02, 0x000e, 0x0004},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000e, 0x0005},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000e, 0x0006},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000e, 0x0007},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000e, 0x0008},
+	cmdLutElement{0x02, 0x00, -1, 0x03, 0x000e, 0x0009},
+	cmdLutElement{0x03, 0x00, -1, 0x00, 0x0012, 0x0002},
+	cmdLutElement{0x03, 0x00, -1, 0x01, 0x0012, 0x0003},
+	cmdLutElement{0x03, 0x00, -1, 0x02, 0x0012, 0x0004},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x0012, 0x0005},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x0012, 0x0006},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x0012, 0x0007},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x0012, 0x0008},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x0012, 0x0009},
+	cmdLutElement{0x03, 0x00, -1, 0x00, 0x001a, 0x0002},
+	cmdLutElement{0x03, 0x00, -1, 0x01, 0x001a, 0x0003},
+	cmdLutElement{0x03, 0x00, -1, 0x02, 0x001a, 0x0004},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x001a, 0x0005},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x001a, 0x0006},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x001a, 0x0007},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x001a, 0x0008},
+	cmdLutElement{0x03, 0x00, -1, 0x03, 0x001a, 0x0009},
+	cmdLutElement{0x04, 0x00, -1, 0x00, 0x0022, 0x0002},
+	cmdLutElement{0x04, 0x00, -1, 0x01, 0x0022, 0x0003},
+	cmdLutElement{0x04, 0x00, -1, 0x02, 0x0022, 0x0004},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0022, 0x0005},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0022, 0x0006},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0022, 0x0007},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0022, 0x0008},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0022, 0x0009},
+	cmdLutElement{0x04, 0x00, -1, 0x00, 0x0032, 0x0002},
+	cmdLutElement{0x04, 0x00, -1, 0x01, 0x0032, 0x0003},
+	cmdLutElement{0x04, 0x00, -1, 0x02, 0x0032, 0x0004},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0032, 0x0005},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0032, 0x0006},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0032, 0x0007},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0032, 0x0008},
+	cmdLutElement{0x04, 0x00, -1, 0x03, 0x0032, 0x0009},
+	cmdLutElement{0x05, 0x00, -1, 0x00, 0x0042, 0x0002},
+	cmdLutElement{0x05, 0x00, -1, 0x01, 0x0042, 0x0003},
+	cmdLutElement{0x05, 0x00, -1, 0x02, 0x0042, 0x0004},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0042, 0x0005},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0042, 0x0006},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0042, 0x0007},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0042, 0x0008},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0042, 0x0009},
+	cmdLutElement{0x05, 0x00, -1, 0x00, 0x0062, 0x0002},
+	cmdLutElement{0x05, 0x00, -1, 0x01, 0x0062, 0x0003},
+	cmdLutElement{0x05, 0x00, -1, 0x02, 0x0062, 0x0004},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0062, 0x0005},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0062, 0x0006},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0062, 0x0007},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0062, 0x0008},
+	cmdLutElement{0x05, 0x00, -1, 0x03, 0x0062, 0x0009},
+	cmdLutElement{0x02, 0x01, -1, 0x03, 0x000a, 0x000a},
+	cmdLutElement{0x02, 0x01, -1, 0x03, 0x000a, 0x000c},
+	cmdLutElement{0x02, 0x02, -1, 0x03, 0x000a, 0x000e},
+	cmdLutElement{0x02, 0x02, -1, 0x03, 0x000a, 0x0012},
+	cmdLutElement{0x02, 0x03, -1, 0x03, 0x000a, 0x0016},
+	cmdLutElement{0x02, 0x03, -1, 0x03, 0x000a, 0x001e},
+	cmdLutElement{0x02, 0x04, -1, 0x03, 0x000a, 0x0026},
+	cmdLutElement{0x02, 0x04, -1, 0x03, 0x000a, 0x0036},
+	cmdLutElement{0x02, 0x01, -1, 0x03, 0x000e, 0x000a},
+	cmdLutElement{0x02, 0x01, -1, 0x03, 0x000e, 0x000c},
+	cmdLutElement{0x02, 0x02, -1, 0x03, 0x000e, 0x000e},
+	cmdLutElement{0x02, 0x02, -1, 0x03, 0x000e, 0x0012},
+	cmdLutElement{0x02, 0x03, -1, 0x03, 0x000e, 0x0016},
+	cmdLutElement{0x02, 0x03, -1, 0x03, 0x000e, 0x001e},
+	cmdLutElement{0x02, 0x04, -1, 0x03, 0x000e, 0x0026},
+	cmdLutElement{0x02, 0x04, -1, 0x03, 0x000e, 0x0036},
+	cmdLutElement{0x03, 0x01, -1, 0x03, 0x0012, 0x000a},
+	cmdLutElement{0x03, 0x01, -1, 0x03, 0x0012, 0x000c},
+	cmdLutElement{0x03, 0x02, -1, 0x03, 0x0012, 0x000e},
+	cmdLutElement{0x03, 0x02, -1, 0x03, 0x0012, 0x0012},
+	cmdLutElement{0x03, 0x03, -1, 0x03, 0x0012, 0x0016},
+	cmdLutElement{0x03, 0x03, -1, 0x03, 0x0012, 0x001e},
+	cmdLutElement{0x03, 0x04, -1, 0x03, 0x0012, 0x0026},
+	cmdLutElement{0x03, 0x04, -1, 0x03, 0x0012, 0x0036},
+	cmdLutElement{0x03, 0x01, -1, 0x03, 0x001a, 0x000a},
+	cmdLutElement{0x03, 0x01, -1, 0x03, 0x001a, 0x000c},
+	cmdLutElement{0x03, 0x02, -1, 0x03, 0x001a, 0x000e},
+	cmdLutElement{0x03, 0x02, -1, 0x03, 0x001a, 0x0012},
+	cmdLutElement{0x03, 0x03, -1, 0x03, 0x001a, 0x0016},
+	cmdLutElement{0x03, 0x03, -1, 0x03, 0x001a, 0x001e},
+	cmdLutElement{0x03, 0x04, -1, 0x03, 0x001a, 0x0026},
+	cmdLutElement{0x03, 0x04, -1, 0x03, 0x001a, 0x0036},
+	cmdLutElement{0x04, 0x01, -1, 0x03, 0x0022, 0x000a},
+	cmdLutElement{0x04, 0x01, -1, 0x03, 0x0022, 0x000c},
+	cmdLutElement{0x04, 0x02, -1, 0x03, 0x0022, 0x000e},
+	cmdLutElement{0x04, 0x02, -1, 0x03, 0x0022, 0x0012},
+	cmdLutElement{0x04, 0x03, -1, 0x03, 0x0022, 0x0016},
+	cmdLutElement{0x04, 0x03, -1, 0x03, 0x0022, 0x001e},
+	cmdLutElement{0x04, 0x04, -1, 0x03, 0x0022, 0x0026},
+	cmdLutElement{0x04, 0x04, -1, 0x03, 0x0022, 0x0036},
+	cmdLutElement{0x04, 0x01, -1, 0x03, 0x0032, 0x000a},
+	cmdLutElement{0x04, 0x01, -1, 0x03, 0x0032, 0x000c},
+	cmdLutElement{0x04, 0x02, -1, 0x03, 0x0032, 0x000e},
+	cmdLutElement{0x04, 0x02, -1, 0x03, 0x0032, 0x0012},
+	cmdLutElement{0x04, 0x03, -1, 0x03, 0x0032, 0x0016},
+	cmdLutElement{0x04, 0x03, -1, 0x03, 0x0032, 0x001e},
+	cmdLutElement{0x04, 0x04, -1, 0x03, 0x0032, 0x0026},
+	cmdLutElement{0x04, 0x04, -1, 0x03, 0x0032, 0x0036},
+	cmdLutElement{0x05, 0x01, -1, 0x03, 0x0042, 0x000a},
+	cmdLutElement{0x05, 0x01, -1, 0x03, 0x0042, 0x000c},
+	cmdLutElement{0x05, 0x02, -1, 0x03, 0x0042, 0x000e},
+	cmdLutElement{0x05, 0x02, -1, 0x03, 0x0042, 0x0012},
+	cmdLutElement{0x05, 0x03, -1, 0x03, 0x0042, 0x0016},
+	cmdLutElement{0x05, 0x03, -1, 0x03, 0x0042, 0x001e},
+	cmdLutElement{0x05, 0x04, -1, 0x03, 0x0042, 0x0026},
+	cmdLutElement{0x05, 0x04, -1, 0x03, 0x0042, 0x0036},
+	cmdLutElement{0x05, 0x01, -1, 0x03, 0x0062, 0x000a},
+	cmdLutElement{0x05, 0x01, -1, 0x03, 0x0062, 0x000c},
+	cmdLutElement{0x05, 0x02, -1, 0x03, 0x0062, 0x000e},
+	cmdLutElement{0x05, 0x02, -1, 0x03, 0x0062, 0x0012},
+	cmdLutElement{0x05, 0x03, -1, 0x03, 0x0062, 0x0016},
+	cmdLutElement{0x05, 0x03, -1, 0x03, 0x0062, 0x001e},
+	cmdLutElement{0x05, 0x04, -1, 0x03, 0x0062, 0x0026},
+	cmdLutElement{0x05, 0x04, -1, 0x03, 0x0062, 0x0036},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0000, 0x0046},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0000, 0x0066},
+	cmdLutElement{0x00, 0x06, -1, 0x03, 0x0000, 0x0086},
+	cmdLutElement{0x00, 0x07, -1, 0x03, 0x0000, 0x00c6},
+	cmdLutElement{0x00, 0x08, -1, 0x03, 0x0000, 0x0146},
+	cmdLutElement{0x00, 0x09, -1, 0x03, 0x0000, 0x0246},
+	cmdLutElement{0x00, 0x0a, -1, 0x03, 0x0000, 0x0446},
+	cmdLutElement{0x00, 0x18, -1, 0x03, 0x0000, 0x0846},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0001, 0x0046},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0001, 0x0066},
+	cmdLutElement{0x00, 0x06, -1, 0x03, 0x0001, 0x0086},
+	cmdLutElement{0x00, 0x07, -1, 0x03, 0x0001, 0x00c6},
+	cmdLutElement{0x00, 0x08, -1, 0x03, 0x0001, 0x0146},
+	cmdLutElement{0x00, 0x09, -1, 0x03, 0x0001, 0x0246},
+	cmdLutElement{0x00, 0x0a, -1, 0x03, 0x0001, 0x0446},
+	cmdLutElement{0x00, 0x18, -1, 0x03, 0x0001, 0x0846},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0002, 0x0046},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0002, 0x0066},
+	cmdLutElement{0x00, 0x06, -1, 0x03, 0x0002, 0x0086},
+	cmdLutElement{0x00, 0x07, -1, 0x03, 0x0002, 0x00c6},
+	cmdLutElement{0x00, 0x08, -1, 0x03, 0x0002, 0x0146},
+	cmdLutElement{0x00, 0x09, -1, 0x03, 0x0002, 0x0246},
+	cmdLutElement{0x00, 0x0a, -1, 0x03, 0x0002, 0x0446},
+	cmdLutElement{0x00, 0x18, -1, 0x03, 0x0002, 0x0846},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0003, 0x0046},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0003, 0x0066},
+	cmdLutElement{0x00, 0x06, -1, 0x03, 0x0003, 0x0086},
+	cmdLutElement{0x00, 0x07, -1, 0x03, 0x0003, 0x00c6},
+	cmdLutElement{0x00, 0x08, -1, 0x03, 0x0003, 0x0146},
+	cmdLutElement{0x00, 0x09, -1, 0x03, 0x0003, 0x0246},
+	cmdLutElement{0x00, 0x0a, -1, 0x03, 0x0003, 0x0446},
+	cmdLutElement{0x00, 0x18, -1, 0x03, 0x0003, 0x0846},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0004, 0x0046},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0004, 0x0066},
+	cmdLutElement{0x00, 0x06, -1, 0x03, 0x0004, 0x0086},
+	cmdLutElement{0x00, 0x07, -1, 0x03, 0x0004, 0x00c6},
+	cmdLutElement{0x00, 0x08, -1, 0x03, 0x0004, 0x0146},
+	cmdLutElement{0x00, 0x09, -1, 0x03, 0x0004, 0x0246},
+	cmdLutElement{0x00, 0x0a, -1, 0x03, 0x0004, 0x0446},
+	cmdLutElement{0x00, 0x18, -1, 0x03, 0x0004, 0x0846},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0005, 0x0046},
+	cmdLutElement{0x00, 0x05, -1, 0x03, 0x0005, 0x0066},
+	cmdLutElement{0x00, 0x06, -1, 0x03, 0x0005, 0x0086},
+	cmdLutElement{0x00, 0x07, -1, 0x03, 0x0005, 0x00c6},
+	cmdLutElement{0x00, 0x08, -1, 0x03, 0x0005, 0x0146},
+	cmdLutElement{0x00, 0x09, -1, 0x03, 0x0005, 0x0246},
+	cmdLutElement{0x00, 0x0a, -1, 0x03, 0x0005, 0x0446},
+	cmdLutElement{0x00, 0x18, -1, 0x03, 0x0005, 0x0846},
+	cmdLutElement{0x01, 0x05, -1, 0x03, 0x0006, 0x0046},
+	cmdLutElement{0x01, 0x05, -1, 0x03, 0x0006, 0x0066},
+	cmdLutElement{0x01, 0x06, -1, 0x03, 0x0006, 0x0086},
+	cmdLutElement{0x01, 0x07, -1, 0x03, 0x0006, 0x00c6},
+	cmdLutElement{0x01, 0x08, -1, 0x03, 0x0006, 0x0146},
+	cmdLutElement{0x01, 0x09, -1, 0x03, 0x0006, 0x0246},
+	cmdLutElement{0x01, 0x0a, -1, 0x03, 0x0006, 0x0446},
+	cmdLutElement{0x01, 0x18, -1, 0x03, 0x0006, 0x0846},
+	cmdLutElement{0x01, 0x05, -1, 0x03, 0x0008, 0x0046},
+	cmdLutElement{0x01, 0x05, -1, 0x03, 0x0008, 0x0066},
+	cmdLutElement{0x01, 0x06, -1, 0x03, 0x0008, 0x0086},
+	cmdLutElement{0x01, 0x07, -1, 0x03, 0x0008, 0x00c6},
+	cmdLutElement{0x01, 0x08, -1, 0x03, 0x0008, 0x0146},
+	cmdLutElement{0x01, 0x09, -1, 0x03, 0x0008, 0x0246},
+	cmdLutElement{0x01, 0x0a, -1, 0x03, 0x0008, 0x0446},
+	cmdLutElement{0x01, 0x18, -1, 0x03, 0x0008, 0x0846},
+	cmdLutElement{0x06, 0x00, -1, 0x00, 0x0082, 0x0002},
+	cmdLutElement{0x06, 0x00, -1, 0x01, 0x0082, 0x0003},
+	cmdLutElement{0x06, 0x00, -1, 0x02, 0x0082, 0x0004},
+	cmdLutElement{0x06, 0x00, -1, 0x03, 0x0082, 0x0005},
+	cmdLutElement{0x06, 0x00, -1, 0x03, 0x0082, 0x0006},
+	cmdLutElement{0x06, 0x00, -1, 0x03, 0x0082, 0x0007},
+	cmdLutElement{0x06, 0x00, -1, 0x03, 0x0082, 0x0008},
+	cmdLutElement{0x06, 0x00, -1, 0x03, 0x0082, 0x0009},
+	cmdLutElement{0x07, 0x00, -1, 0x00, 0x00c2, 0x0002},
+	cmdLutElement{0x07, 0x00, -1, 0x01, 0x00c2, 0x0003},
+	cmdLutElement{0x07, 0x00, -1, 0x02, 0x00c2, 0x0004},
+	cmdLutElement{0x07, 0x00, -1, 0x03, 0x00c2, 0x0005},
+	cmdLutElement{0x07, 0x00, -1, 0x03, 0x00c2, 0x0006},
+	cmdLutElement{0x07, 0x00, -1, 0x03, 0x00c2, 0x0007},
+	cmdLutElement{0x07, 0x00, -1, 0x03, 0x00c2, 0x0008},
+	cmdLutElement{0x07, 0x00, -1, 0x03, 0x00c2, 0x0009},
+	cmdLutElement{0x08, 0x00, -1, 0x00, 0x0142, 0x0002},
+	cmdLutElement{0x08, 0x00, -1, 0x01, 0x0142, 0x0003},
+	cmdLutElement{0x08, 0x00, -1, 0x02, 0x0142, 0x0004},
+	cmdLutElement{0x08, 0x00, -1, 0x03, 0x0142, 0x0005},
+	cmdLutElement{0x08, 0x00, -1, 0x03, 0x0142, 0x0006},
+	cmdLutElement{0x08, 0x00, -1, 0x03, 0x0142, 0x0007},
+	cmdLutElement{0x08, 0x00, -1, 0x03, 0x0142, 0x0008},
+	cmdLutElement{0x08, 0x00, -1, 0x03, 0x0142, 0x0009},
+	cmdLutElement{0x09, 0x00, -1, 0x00, 0x0242, 0x0002},
+	cmdLutElement{0x09, 0x00, -1, 0x01, 0x0242, 0x0003},
+	cmdLutElement{0x09, 0x00, -1, 0x02, 0x0242, 0x0004},
+	cmdLutElement{0x09, 0x00, -1, 0x03, 0x0242, 0x0005},
+	cmdLutElement{0x09, 0x00, -1, 0x03, 0x0242, 0x0006},
+	cmdLutElement{0x09, 0x00, -1, 0x03, 0x0242, 0x0007},
+	cmdLutElement{0x09, 0x00, -1, 0x03, 0x0242, 0x0008},
+	cmdLutElement{0x09, 0x00, -1, 0x03, 0x0242, 0x0009},
+	cmdLutElement{0x0a, 0x00, -1, 0x00, 0x0442, 0x0002},
+	cmdLutElement{0x0a, 0x00, -1, 0x01, 0x0442, 0x0003},
+	cmdLutElement{0x0a, 0x00, -1, 0x02, 0x0442, 0x0004},
+	cmdLutElement{0x0a, 0x00, -1, 0x03, 0x0442, 0x0005},
+	cmdLutElement{0x0a, 0x00, -1, 0x03, 0x0442, 0x0006},
+	cmdLutElement{0x0a, 0x00, -1, 0x03, 0x0442, 0x0007},
+	cmdLutElement{0x0a, 0x00, -1, 0x03, 0x0442, 0x0008},
+	cmdLutElement{0x0a, 0x00, -1, 0x03, 0x0442, 0x0009},
+	cmdLutElement{0x0c, 0x00, -1, 0x00, 0x0842, 0x0002},
+	cmdLutElement{0x0c, 0x00, -1, 0x01, 0x0842, 0x0003},
+	cmdLutElement{0x0c, 0x00, -1, 0x02, 0x0842, 0x0004},
+	cmdLutElement{0x0c, 0x00, -1, 0x03, 0x0842, 0x0005},
+	cmdLutElement{0x0c, 0x00, -1, 0x03, 0x0842, 0x0006},
+	cmdLutElement{0x0c, 0x00, -1, 0x03, 0x0842, 0x0007},
+	cmdLutElement{0x0c, 0x00, -1, 0x03, 0x0842, 0x0008},
+	cmdLutElement{0x0c, 0x00, -1, 0x03, 0x0842, 0x0009},
+	cmdLutElement{0x0e, 0x00, -1, 0x00, 0x1842, 0x0002},
+	cmdLutElement{0x0e, 0x00, -1, 0x01, 0x1842, 0x0003},
+	cmdLutElement{0x0e, 0x00, -1, 0x02, 0x1842, 0x0004},
+	cmdLutElement{0x0e, 0x00, -1, 0x03, 0x1842, 0x0005},
+	cmdLutElement{0x0e, 0x00, -1, 0x03, 0x1842, 0x0006},
+	cmdLutElement{0x0e, 0x00, -1, 0x03, 0x1842, 0x0007},
+	cmdLutElement{0x0e, 0x00, -1, 0x03, 0x1842, 0x0008},
+	cmdLutElement{0x0e, 0x00, -1, 0x03, 0x1842, 0x0009},
+	cmdLutElement{0x18, 0x00, -1, 0x00, 0x5842, 0x0002},
+	cmdLutElement{0x18, 0x00, -1, 0x01, 0x5842, 0x0003},
+	cmdLutElement{0x18, 0x00, -1, 0x02, 0x5842, 0x0004},
+	cmdLutElement{0x18, 0x00, -1, 0x03, 0x5842, 0x0005},
+	cmdLutElement{0x18, 0x00, -1, 0x03, 0x5842, 0x0006},
+	cmdLutElement{0x18, 0x00, -1, 0x03, 0x5842, 0x0007},
+	cmdLutElement{0x18, 0x00, -1, 0x03, 0x5842, 0x0008},
+	cmdLutElement{0x18, 0x00, -1, 0x03, 0x5842, 0x0009},
+	cmdLutElement{0x02, 0x05, -1, 0x03, 0x000a, 0x0046},
+	cmdLutElement{0x02, 0x05, -1, 0x03, 0x000a, 0x0066},
+	cmdLutElement{0x02, 0x06, -1, 0x03, 0x000a, 0x0086},
+	cmdLutElement{0x02, 0x07, -1, 0x03, 0x000a, 0x00c6},
+	cmdLutElement{0x02, 0x08, -1, 0x03, 0x000a, 0x0146},
+	cmdLutElement{0x02, 0x09, -1, 0x03, 0x000a, 0x0246},
+	cmdLutElement{0x02, 0x0a, -1, 0x03, 0x000a, 0x0446},
+	cmdLutElement{0x02, 0x18, -1, 0x03, 0x000a, 0x0846},
+	cmdLutElement{0x02, 0x05, -1, 0x03, 0x000e, 0x0046},
+	cmdLutElement{0x02, 0x05, -1, 0x03, 0x000e, 0x0066},
+	cmdLutElement{0x02, 0x06, -1, 0x03, 0x000e, 0x0086},
+	cmdLutElement{0x02, 0x07, -1, 0x03, 0x000e, 0x00c6},
+	cmdLutElement{0x02, 0x08, -1, 0x03, 0x000e, 0x0146},
+	cmdLutElement{0x02, 0x09, -1, 0x03, 0x000e, 0x0246},
+	cmdLutElement{0x02, 0x0a, -1, 0x03, 0x000e, 0x0446},
+	cmdLutElement{0x02, 0x18, -1, 0x03, 0x000e, 0x0846},
+	cmdLutElement{0x03, 0x05, -1, 0x03, 0x0012, 0x0046},
+	cmdLutElement{0x03, 0x05, -1, 0x03, 0x0012, 0x0066},
+	cmdLutElement{0x03, 0x06, -1, 0x03, 0x0012, 0x0086},
+	cmdLutElement{0x03, 0x07, -1, 0x03, 0x0012, 0x00c6},
+	cmdLutElement{0x03, 0x08, -1, 0x03, 0x0012, 0x0146},
+	cmdLutElement{0x03, 0x09, -1, 0x03, 0x0012, 0x0246},
+	cmdLutElement{0x03, 0x0a, -1, 0x03, 0x0012, 0x0446},
+	cmdLutElement{0x03, 0x18, -1, 0x03, 0x0012, 0x0846},
+	cmdLutElement{0x03, 0x05, -1, 0x03, 0x001a, 0x0046},
+	cmdLutElement{0x03, 0x05, -1, 0x03, 0x001a, 0x0066},
+	cmdLutElement{0x03, 0x06, -1, 0x03, 0x001a, 0x0086},
+	cmdLutElement{0x03, 0x07, -1, 0x03, 0x001a, 0x00c6},
+	cmdLutElement{0x03, 0x08, -1, 0x03, 0x001a, 0x0146},
+	cmdLutElement{0x03, 0x09, -1, 0x03, 0x001a, 0x0246},
+	cmdLutElement{0x03, 0x0a, -1, 0x03, 0x001a, 0x0446},
+	cmdLutElement{0x03, 0x18, -1, 0x03, 0x001a, 0x0846},
+	cmdLutElement{0x04, 0x05, -1, 0x03, 0x0022, 0x0046},
+	cmdLutElement{0x04, 0x05, -1, 0x03, 0x0022, 0x0066},
+	cmdLutElement{0x04, 0x06, -1, 0x03, 0x0022, 0x0086},
+	cmdLutElement{0x04, 0x07, -1, 0x03, 0x0022, 0x00c6},
+	cmdLutElement{0x04, 0x08, -1, 0x03, 0x0022, 0x0146},
+	cmdLutElement{0x04, 0x09, -1, 0x03, 0x0022, 0x0246},
+	cmdLutElement{0x04, 0x0a, -1, 0x03, 0x0022, 0x0446},
+	cmdLutElement{0x04, 0x18, -1, 0x03, 0x0022, 0x0846},
+	cmdLutElement{0x04, 0x05, -1, 0x03, 0x0032, 0x0046},
+	cmdLutElement{0x04, 0x05, -1, 0x03, 0x0032, 0x0066},
+	cmdLutElement{0x04, 0x06, -1, 0x03, 0x0032, 0x0086},
+	cmdLutElement{0x04, 0x07, -1, 0x03, 0x0032, 0x00c6},
+	cmdLutElement{0x04, 0x08, -1, 0x03, 0x0032, 0x0146},
+	cmdLutElement{0x04, 0x09, -1, 0x03, 0x0032, 0x0246},
+	cmdLutElement{0x04, 0x0a, -1, 0x03, 0x0032, 0x0446},
+	cmdLutElement{0x04, 0x18, -1, 0x03, 0x0032, 0x0846},
+	cmdLutElement{0x05, 0x05, -1, 0x03, 0x0042, 0x0046},
+	cmdLutElement{0x05, 0x05, -1, 0x03, 0x0042, 0x0066},
+	cmdLutElement{0x05, 0x06, -1, 0x03, 0x0042, 0x0086},
+	cmdLutElement{0x05, 0x07, -1, 0x03, 0x0042, 0x00c6},
+	cmdLutElement{0x05, 0x08, -1, 0x03, 0x0042, 0x0146},
+	cmdLutElement{0x05, 0x09, -1, 0x03, 0x0042, 0x0246},
+	cmdLutElement{0x05, 0x0a, -1, 0x03, 0x0042, 0x0446},
+	cmdLutElement{0x05, 0x18, -1, 0x03, 0x0042, 0x0846},
+	cmdLutElement{0x05, 0x05, -1, 0x03, 0x0062, 0x0046},
+	cmdLutElement{0x05, 0x05, -1, 0x03, 0x0062, 0x0066},
+	cmdLutElement{0x05, 0x06, -1, 0x03, 0x0062, 0x0086},
+	cmdLutElement{0x05, 0x07, -1, 0x03, 0x0062, 0x00c6},
+	cmdLutElement{0x05, 0x08, -1, 0x03, 0x0062, 0x0146},
+	cmdLutElement{0x05, 0x09, -1, 0x03, 0x0062, 0x0246},
+	cmdLutElement{0x05, 0x0a, -1, 0x03, 0x0062, 0x0446},
+	cmdLutElement{0x05, 0x18, -1, 0x03, 0x0062, 0x0846},
+	cmdLutElement{0x06, 0x01, -1, 0x03, 0x0082, 0x000a},
+	cmdLutElement{0x06, 0x01, -1, 0x03, 0x0082, 0x000c},
+	cmdLutElement{0x06, 0x02, -1, 0x03, 0x0082, 0x000e},
+	cmdLutElement{0x06, 0x02, -1, 0x03, 0x0082, 0x0012},
+	cmdLutElement{0x06, 0x03, -1, 0x03, 0x0082, 0x0016},
+	cmdLutElement{0x06, 0x03, -1, 0x03, 0x0082, 0x001e},
+	cmdLutElement{0x06, 0x04, -1, 0x03, 0x0082, 0x0026},
+	cmdLutElement{0x06, 0x04, -1, 0x03, 0x0082, 0x0036},
+	cmdLutElement{0x07, 0x01, -1, 0x03, 0x00c2, 0x000a},
+	cmdLutElement{0x07, 0x01, -1, 0x03, 0x00c2, 0x000c},
+	cmdLutElement{0x07, 0x02, -1, 0x03, 0x00c2, 0x000e},
+	cmdLutElement{0x07, 0x02, -1, 0x03, 0x00c2, 0x0012},
+	cmdLutElement{0x07, 0x03, -1, 0x03, 0x00c2, 0x0016},
+	cmdLutElement{0x07, 0x03, -1, 0x03, 0x00c2, 0x001e},
+	cmdLutElement{0x07, 0x04, -1, 0x03, 0x00c2, 0x0026},
+	cmdLutElement{0x07, 0x04, -1, 0x03, 0x00c2, 0x0036},
+	cmdLutElement{0x08, 0x01, -1, 0x03, 0x0142, 0x000a},
+	cmdLutElement{0x08, 0x01, -1, 0x03, 0x0142, 0x000c},
+	cmdLutElement{0x08, 0x02, -1, 0x03, 0x0142, 0x000e},
+	cmdLutElement{0x08, 0x02, -1, 0x03, 0x0142, 0x0012},
+	cmdLutElement{0x08, 0x03, -1, 0x03, 0x0142, 0x0016},
+	cmdLutElement{0x08, 0x03, -1, 0x03, 0x0142, 0x001e},
+	cmdLutElement{0x08, 0x04, -1, 0x03, 0x0142, 0x0026},
+	cmdLutElement{0x08, 0x04, -1, 0x03, 0x0142, 0x0036},
+	cmdLutElement{0x09, 0x01, -1, 0x03, 0x0242, 0x000a},
+	cmdLutElement{0x09, 0x01, -1, 0x03, 0x0242, 0x000c},
+	cmdLutElement{0x09, 0x02, -1, 0x03, 0x0242, 0x000e},
+	cmdLutElement{0x09, 0x02, -1, 0x03, 0x0242, 0x0012},
+	cmdLutElement{0x09, 0x03, -1, 0x03, 0x0242, 0x0016},
+	cmdLutElement{0x09, 0x03, -1, 0x03, 0x0242, 0x001e},
+	cmdLutElement{0x09, 0x04, -1, 0x03, 0x0242, 0x0026},
+	cmdLutElement{0x09, 0x04, -1, 0x03, 0x0242, 0x0036},
+	cmdLutElement{0x0a, 0x01, -1, 0x03, 0x0442, 0x000a},
+	cmdLutElement{0x0a, 0x01, -1, 0x03, 0x0442, 0x000c},
+	cmdLutElement{0x0a, 0x02, -1, 0x03, 0x0442, 0x000e},
+	cmdLutElement{0x0a, 0x02, -1, 0x03, 0x0442, 0x0012},
+	cmdLutElement{0x0a, 0x03, -1, 0x03, 0x0442, 0x0016},
+	cmdLutElement{0x0a, 0x03, -1, 0x03, 0x0442, 0x001e},
+	cmdLutElement{0x0a, 0x04, -1, 0x03, 0x0442, 0x0026},
+	cmdLutElement{0x0a, 0x04, -1, 0x03, 0x0442, 0x0036},
+	cmdLutElement{0x0c, 0x01, -1, 0x03, 0x0842, 0x000a},
+	cmdLutElement{0x0c, 0x01, -1, 0x03, 0x0842, 0x000c},
+	cmdLutElement{0x0c, 0x02, -1, 0x03, 0x0842, 0x000e},
+	cmdLutElement{0x0c, 0x02, -1, 0x03, 0x0842, 0x0012},
+	cmdLutElement{0x0c, 0x03, -1, 0x03, 0x0842, 0x0016},
+	cmdLutElement{0x0c, 0x03, -1, 0x03, 0x0842, 0x001e},
+	cmdLutElement{0x0c, 0x04, -1, 0x03, 0x0842, 0x0026},
+	cmdLutElement{0x0c, 0x04, -1, 0x03, 0x0842, 0x0036},
+	cmdLutElement{0x0e, 0x01, -1, 0x03, 0x1842, 0x000a},
+	cmdLutElement{0x0e, 0x01, -1, 0x03, 0x1842, 0x000c},
+	cmdLutElement{0x0e, 0x02, -1, 0x03, 0x1842, 0x000e},
+	cmdLutElement{0x0e, 0x02, -1, 0x03, 0x1842, 0x0012},
+	cmdLutElement{0x0e, 0x03, -1, 0x03, 0x1842, 0x0016},
+	cmdLutElement{0x0e, 0x03, -1, 0x03, 0x1842, 0x001e},
+	cmdLutElement{0x0e, 0x04, -1, 0x03, 0x1842, 0x0026},
+	cmdLutElement{0x0e, 0x04, -1, 0x03, 0x1842, 0x0036},
+	cmdLutElement{0x18, 0x01, -1, 0x03, 0x5842, 0x000a},
+	cmdLutElement{0x18, 0x01, -1, 0x03, 0x5842, 0x000c},
+	cmdLutElement{0x18, 0x02, -1, 0x03, 0x5842, 0x000e},
+	cmdLutElement{0x18, 0x02, -1, 0x03, 0x5842, 0x0012},
+	cmdLutElement{0x18, 0x03, -1, 0x03, 0x5842, 0x0016},
+	cmdLutElement{0x18, 0x03, -1, 0x03, 0x5842, 0x001e},
+	cmdLutElement{0x18, 0x04, -1, 0x03, 0x5842, 0x0026},
+	cmdLutElement{0x18, 0x04, -1, 0x03, 0x5842, 0x0036},
+	cmdLutElement{0x06, 0x05, -1, 0x03, 0x0082, 0x0046},
+	cmdLutElement{0x06, 0x05, -1, 0x03, 0x0082, 0x0066},
+	cmdLutElement{0x06, 0x06, -1, 0x03, 0x0082, 0x0086},
+	cmdLutElement{0x06, 0x07, -1, 0x03, 0x0082, 0x00c6},
+	cmdLutElement{0x06, 0x08, -1, 0x03, 0x0082, 0x0146},
+	cmdLutElement{0x06, 0x09, -1, 0x03, 0x0082, 0x0246},
+	cmdLutElement{0x06, 0x0a, -1, 0x03, 0x0082, 0x0446},
+	cmdLutElement{0x06, 0x18, -1, 0x03, 0x0082, 0x0846},
+	cmdLutElement{0x07, 0x05, -1, 0x03, 0x00c2, 0x0046},
+	cmdLutElement{0x07, 0x05, -1, 0x03, 0x00c2, 0x0066},
+	cmdLutElement{0x07, 0x06, -1, 0x03, 0x00c2, 0x0086},
+	cmdLutElement{0x07, 0x07, -1, 0x03, 0x00c2, 0x00c6},
+	cmdLutElement{0x07, 0x08, -1, 0x03, 0x00c2, 0x0146},
+	cmdLutElement{0x07, 0x09, -1, 0x03, 0x00c2, 0x0246},
+	cmdLutElement{0x07, 0x0a, -1, 0x03, 0x00c2, 0x0446},
+	cmdLutElement{0x07, 0x18, -1, 0x03, 0x00c2, 0x0846},
+	cmdLutElement{0x08, 0x05, -1, 0x03, 0x0142, 0x0046},
+	cmdLutElement{0x08, 0x05, -1, 0x03, 0x0142, 0x0066},
+	cmdLutElement{0x08, 0x06, -1, 0x03, 0x0142, 0x0086},
+	cmdLutElement{0x08, 0x07, -1, 0x03, 0x0142, 0x00c6},
+	cmdLutElement{0x08, 0x08, -1, 0x03, 0x0142, 0x0146},
+	cmdLutElement{0x08, 0x09, -1, 0x03, 0x0142, 0x0246},
+	cmdLutElement{0x08, 0x0a, -1, 0x03, 0x0142, 0x0446},
+	cmdLutElement{0x08, 0x18, -1, 0x03, 0x0142, 0x0846},
+	cmdLutElement{0x09, 0x05, -1, 0x03, 0x0242, 0x0046},
+	cmdLutElement{0x09, 0x05, -1, 0x03, 0x0242, 0x0066},
+	cmdLutElement{0x09, 0x06, -1, 0x03, 0x0242, 0x0086},
+	cmdLutElement{0x09, 0x07, -1, 0x03, 0x0242, 0x00c6},
+	cmdLutElement{0x09, 0x08, -1, 0x03, 0x0242, 0x0146},
+	cmdLutElement{0x09, 0x09, -1, 0x03, 0x0242, 0x0246},
+	cmdLutElement{0x09, 0x0a, -1, 0x03, 0x0242, 0x0446},
+	cmdLutElement{0x09, 0x18, -1, 0x03, 0x0242, 0x0846},
+	cmdLutElement{0x0a, 0x05, -1, 0x03, 0x0442, 0x0046},
+	cmdLutElement{0x0a, 0x05, -1, 0x03, 0x0442, 0x0066},
+	cmdLutElement{0x0a, 0x06, -1, 0x03, 0x0442, 0x0086},
+	cmdLutElement{0x0a, 0x07, -1, 0x03, 0x0442, 0x00c6},
+	cmdLutElement{0x0a, 0x08, -1, 0x03, 0x0442, 0x0146},
+	cmdLutElement{0x0a, 0x09, -1, 0x03, 0x0442, 0x0246},
+	cmdLutElement{0x0a, 0x0a, -1, 0x03, 0x0442, 0x0446},
+	cmdLutElement{0x0a, 0x18, -1, 0x03, 0x0442, 0x0846},
+	cmdLutElement{0x0c, 0x05, -1, 0x03, 0x0842, 0x0046},
+	cmdLutElement{0x0c, 0x05, -1, 0x03, 0x0842, 0x0066},
+	cmdLutElement{0x0c, 0x06, -1, 0x03, 0x0842, 0x0086},
+	cmdLutElement{0x0c, 0x07, -1, 0x03, 0x0842, 0x00c6},
+	cmdLutElement{0x0c, 0x08, -1, 0x03, 0x0842, 0x0146},
+	cmdLutElement{0x0c, 0x09, -1, 0x03, 0x0842, 0x0246},
+	cmdLutElement{0x0c, 0x0a, -1, 0x03, 0x0842, 0x0446},
+	cmdLutElement{0x0c, 0x18, -1, 0x03, 0x0842, 0x0846},
+	cmdLutElement{0x0e, 0x05, -1, 0x03, 0x1842, 0x0046},
+	cmdLutElement{0x0e, 0x05, -1, 0x03, 0x1842, 0x0066},
+	cmdLutElement{0x0e, 0x06, -1, 0x03, 0x1842, 0x0086},
+	cmdLutElement{0x0e, 0x07, -1, 0x03, 0x1842, 0x00c6},
+	cmdLutElement{0x0e, 0x08, -1, 0x03, 0x1842, 0x0146},
+	cmdLutElement{0x0e, 0x09, -1, 0x03, 0x1842, 0x0246},
+	cmdLutElement{0x0e, 0x0a, -1, 0x03, 0x1842, 0x0446},
+	cmdLutElement{0x0e, 0x18, -1, 0x03, 0x1842, 0x0846},
+	cmdLutElement{0x18, 0x05, -1, 0x03, 0x5842, 0x0046},
+	cmdLutElement{0x18, 0x05, -1, 0x03, 0x5842, 0x0066},
+	cmdLutElement{0x18, 0x06, -1, 0x03, 0x5842, 0x0086},
+	cmdLutElement{0x18, 0x07, -1, 0x03, 0x5842, 0x00c6},
+	cmdLutElement{0x18, 0x08, -1, 0x03, 0x5842, 0x0146},
+	cmdLutElement{0x18, 0x09, -1, 0x03, 0x5842, 0x0246},
+	cmdLutElement{0x18, 0x0a, -1, 0x03, 0x5842, 0x0446},
+	cmdLutElement{0x18, 0x18, -1, 0x03, 0x5842, 0x0846},
+}

vendor/github.com/andybalholm/brotli/quality.go

@@ -0,0 +1,196 @@
+package brotli
+
+const fastOnePassCompressionQuality = 0
+
+const fastTwoPassCompressionQuality = 1
+
+const zopflificationQuality = 10
+
+const hqZopflificationQuality = 11
+
+const maxQualityForStaticEntropyCodes = 2
+
+const minQualityForBlockSplit = 4
+
+const minQualityForNonzeroDistanceParams = 4
+
+const minQualityForOptimizeHistograms = 4
+
+const minQualityForExtensiveReferenceSearch = 5
+
+const minQualityForContextModeling = 5
+
+const minQualityForHqContextModeling = 7
+
+const minQualityForHqBlockSplitting = 10
+
+/* For quality below MIN_QUALITY_FOR_BLOCK_SPLIT there is no block splitting,
+   so we buffer at most this much literals and commands. */
+const maxNumDelayedSymbols = 0x2FFF
+
+/* Returns hash-table size for quality levels 0 and 1. */
+func maxHashTableSize(quality int) uint {
+	if quality == fastOnePassCompressionQuality {
+		return 1 << 15
+	} else {
+		return 1 << 17
+	}
+}
+
+/* The maximum length for which the zopflification uses distinct distances. */
+const maxZopfliLenQuality10 = 150
+
+const maxZopfliLenQuality11 = 325
+
+/* Do not thoroughly search when a long copy is found. */
+const longCopyQuickStep = 16384
+
+func maxZopfliLen(params *encoderParams) uint {
+	if params.quality <= 10 {
+		return maxZopfliLenQuality10
+	} else {
+		return maxZopfliLenQuality11
+	}
+}
+
+/* Number of best candidates to evaluate to expand Zopfli chain. */
+func maxZopfliCandidates(params *encoderParams) uint {
+	if params.quality <= 10 {
+		return 1
+	} else {
+		return 5
+	}
+}
+
+func sanitizeParams(params *encoderParams) {
+	params.quality = brotli_min_int(maxQuality, brotli_max_int(minQuality, params.quality))
+	if params.quality <= maxQualityForStaticEntropyCodes {
+		params.large_window = false
+	}
+
+	if params.lgwin < minWindowBits {
+		params.lgwin = minWindowBits
+	} else {
+		var max_lgwin int
+		if params.large_window {
+			max_lgwin = largeMaxWindowBits
+		} else {
+			max_lgwin = maxWindowBits
+		}
+		if params.lgwin > uint(max_lgwin) {
+			params.lgwin = uint(max_lgwin)
+		}
+	}
+}
+
+/* Returns optimized lg_block value. */
+func computeLgBlock(params *encoderParams) int {
+	var lgblock int = params.lgblock
+	if params.quality == fastOnePassCompressionQuality || params.quality == fastTwoPassCompressionQuality {
+		lgblock = int(params.lgwin)
+	} else if params.quality < minQualityForBlockSplit {
+		lgblock = 14
+	} else if lgblock == 0 {
+		lgblock = 16
+		if params.quality >= 9 && params.lgwin > uint(lgblock) {
+			lgblock = brotli_min_int(18, int(params.lgwin))
+		}
+	} else {
+		lgblock = brotli_min_int(maxInputBlockBits, brotli_max_int(minInputBlockBits, lgblock))
+	}
+
+	return lgblock
+}
+
+/* Returns log2 of the size of main ring buffer area.
+   Allocate at least lgwin + 1 bits for the ring buffer so that the newly
+   added block fits there completely and we still get lgwin bits and at least
+   read_block_size_bits + 1 bits because the copy tail length needs to be
+   smaller than ring-buffer size. */
+func computeRbBits(params *encoderParams) int {
+	return 1 + brotli_max_int(int(params.lgwin), params.lgblock)
+}
+
+func maxMetablockSize(params *encoderParams) uint {
+	var bits int = brotli_min_int(computeRbBits(params), maxInputBlockBits)
+	return uint(1) << uint(bits)
+}
+
+/* When searching for backward references and have not seen matches for a long
+   time, we can skip some match lookups. Unsuccessful match lookups are very
+   expensive and this kind of a heuristic speeds up compression quite a lot.
+   At first 8 byte strides are taken and every second byte is put to hasher.
+   After 4x more literals stride by 16 bytes, every put 4-th byte to hasher.
+   Applied only to qualities 2 to 9. */
+func literalSpreeLengthForSparseSearch(params *encoderParams) uint {
+	if params.quality < 9 {
+		return 64
+	} else {
+		return 512
+	}
+}
+
+func chooseHasher(params *encoderParams, hparams *hasherParams) {
+	if params.quality > 9 {
+		hparams.type_ = 10
+	} else if params.quality == 4 && params.size_hint >= 1<<20 {
+		hparams.type_ = 54
+	} else if params.quality < 5 {
+		hparams.type_ = params.quality
+	} else if params.lgwin <= 16 {
+		if params.quality < 7 {
+			hparams.type_ = 40
+		} else if params.quality < 9 {
+			hparams.type_ = 41
+		} else {
+			hparams.type_ = 42
+		}
+	} else if params.size_hint >= 1<<20 && params.lgwin >= 19 {
+		hparams.type_ = 6
+		hparams.block_bits = params.quality - 1
+		hparams.bucket_bits = 15
+		hparams.hash_len = 5
+		if params.quality < 7 {
+			hparams.num_last_distances_to_check = 4
+		} else if params.quality < 9 {
+			hparams.num_last_distances_to_check = 10
+		} else {
+			hparams.num_last_distances_to_check = 16
+		}
+	} else {
+		hparams.type_ = 5
+		hparams.block_bits = params.quality - 1
+		if params.quality < 7 {
+			hparams.bucket_bits = 14
+		} else {
+			hparams.bucket_bits = 15
+		}
+		if params.quality < 7 {
+			hparams.num_last_distances_to_check = 4
+		} else if params.quality < 9 {
+			hparams.num_last_distances_to_check = 10
+		} else {
+			hparams.num_last_distances_to_check = 16
+		}
+	}
+
+	if params.lgwin > 24 {
+		/* Different hashers for large window brotli: not for qualities <= 2,
+		   these are too fast for large window. Not for qualities >= 10: their
+		   hasher already works well with large window. So the changes are:
+		   H3 --> H35: for quality 3.
+		   H54 --> H55: for quality 4 with size hint > 1MB
+		   H6 --> H65: for qualities 5, 6, 7, 8, 9. */
+		if hparams.type_ == 3 {
+			hparams.type_ = 35
+		}
+
+		if hparams.type_ == 54 {
+			hparams.type_ = 55
+		}
+
+		if hparams.type_ == 6 {
+			hparams.type_ = 65
+		}
+	}
+}

vendor/github.com/andybalholm/brotli/reader.go

@@ -0,0 +1,108 @@
+package brotli
+
+import (
+	"errors"
+	"io"
+)
+
+type decodeError int
+
+func (err decodeError) Error() string {
+	return "brotli: " + string(decoderErrorString(int(err)))
+}
+
+var errExcessiveInput = errors.New("brotli: excessive input")
+var errInvalidState = errors.New("brotli: invalid state")
+
+// readBufSize is a "good" buffer size that avoids excessive round-trips
+// between C and Go but doesn't waste too much memory on buffering.
+// It is arbitrarily chosen to be equal to the constant used in io.Copy.
+const readBufSize = 32 * 1024
+
+// NewReader creates a new Reader reading the given reader.
+func NewReader(src io.Reader) *Reader {
+	r := new(Reader)
+	r.Reset(src)
+	return r
+}
+
+// Reset discards the Reader's state and makes it equivalent to the result of
+// its original state from NewReader, but reading from src instead.
+// This permits reusing a Reader rather than allocating a new one.
+// Error is always nil
+func (r *Reader) Reset(src io.Reader) error {
+	if r.error_code < 0 {
+		// There was an unrecoverable error, leaving the Reader's state
+		// undefined. Clear out everything but the buffer.
+		*r = Reader{buf: r.buf}
+	}
+
+	decoderStateInit(r)
+	r.src = src
+	if r.buf == nil {
+		r.buf = make([]byte, readBufSize)
+	}
+	return nil
+}
+
+func (r *Reader) Read(p []byte) (n int, err error) {
+	if !decoderHasMoreOutput(r) && len(r.in) == 0 {
+		m, readErr := r.src.Read(r.buf)
+		if m == 0 {
+			// If readErr is `nil`, we just proxy underlying stream behavior.
+			return 0, readErr
+		}
+		r.in = r.buf[:m]
+	}
+
+	if len(p) == 0 {
+		return 0, nil
+	}
+
+	for {
+		var written uint
+		in_len := uint(len(r.in))
+		out_len := uint(len(p))
+		in_remaining := in_len
+		out_remaining := out_len
+		result := decoderDecompressStream(r, &in_remaining, &r.in, &out_remaining, &p)
+		written = out_len - out_remaining
+		n = int(written)
+
+		switch result {
+		case decoderResultSuccess:
+			if len(r.in) > 0 {
+				return n, errExcessiveInput
+			}
+			return n, nil
+		case decoderResultError:
+			return n, decodeError(decoderGetErrorCode(r))
+		case decoderResultNeedsMoreOutput:
+			if n == 0 {
+				return 0, io.ErrShortBuffer
+			}
+			return n, nil
+		case decoderNeedsMoreInput:
+		}
+
+		if len(r.in) != 0 {
+			return 0, errInvalidState
+		}
+
+		// Calling r.src.Read may block. Don't block if we have data to return.
+		if n > 0 {
+			return n, nil
+		}
+
+		// Top off the buffer.
+		encN, err := r.src.Read(r.buf)
+		if encN == 0 {
+			// Not enough data to complete decoding.
+			if err == io.EOF {
+				return 0, io.ErrUnexpectedEOF
+			}
+			return 0, err
+		}
+		r.in = r.buf[:encN]
+	}
+}

vendor/github.com/andybalholm/brotli/ringbuffer.go

@@ -0,0 +1,134 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* A ringBuffer(window_bits, tail_bits) contains `1 << window_bits' bytes of
+   data in a circular manner: writing a byte writes it to:
+     `position() % (1 << window_bits)'.
+   For convenience, the ringBuffer array contains another copy of the
+   first `1 << tail_bits' bytes:
+     buffer_[i] == buffer_[i + (1 << window_bits)], if i < (1 << tail_bits),
+   and another copy of the last two bytes:
+     buffer_[-1] == buffer_[(1 << window_bits) - 1] and
+     buffer_[-2] == buffer_[(1 << window_bits) - 2]. */
+type ringBuffer struct {
+	size_       uint32
+	mask_       uint32
+	tail_size_  uint32
+	total_size_ uint32
+	cur_size_   uint32
+	pos_        uint32
+	data_       []byte
+	buffer_     []byte
+}
+
+func ringBufferInit(rb *ringBuffer) {
+	rb.pos_ = 0
+}
+
+func ringBufferSetup(params *encoderParams, rb *ringBuffer) {
+	var window_bits int = computeRbBits(params)
+	var tail_bits int = params.lgblock
+	*(*uint32)(&rb.size_) = 1 << uint(window_bits)
+	*(*uint32)(&rb.mask_) = (1 << uint(window_bits)) - 1
+	*(*uint32)(&rb.tail_size_) = 1 << uint(tail_bits)
+	*(*uint32)(&rb.total_size_) = rb.size_ + rb.tail_size_
+}
+
+const kSlackForEightByteHashingEverywhere uint = 7
+
+/* Allocates or re-allocates data_ to the given length + plus some slack
+   region before and after. Fills the slack regions with zeros. */
+func ringBufferInitBuffer(buflen uint32, rb *ringBuffer) {
+	var new_data []byte
+	var i uint
+	size := 2 + int(buflen) + int(kSlackForEightByteHashingEverywhere)
+	if cap(rb.data_) < size {
+		new_data = make([]byte, size)
+	} else {
+		new_data = rb.data_[:size]
+	}
+	if rb.data_ != nil {
+		copy(new_data, rb.data_[:2+rb.cur_size_+uint32(kSlackForEightByteHashingEverywhere)])
+	}
+
+	rb.data_ = new_data
+	rb.cur_size_ = buflen
+	rb.buffer_ = rb.data_[2:]
+	rb.data_[1] = 0
+	rb.data_[0] = rb.data_[1]
+	for i = 0; i < kSlackForEightByteHashingEverywhere; i++ {
+		rb.buffer_[rb.cur_size_+uint32(i)] = 0
+	}
+}
+
+func ringBufferWriteTail(bytes []byte, n uint, rb *ringBuffer) {
+	var masked_pos uint = uint(rb.pos_ & rb.mask_)
+	if uint32(masked_pos) < rb.tail_size_ {
+		/* Just fill the tail buffer with the beginning data. */
+		var p uint = uint(rb.size_ + uint32(masked_pos))
+		copy(rb.buffer_[p:], bytes[:brotli_min_size_t(n, uint(rb.tail_size_-uint32(masked_pos)))])
+	}
+}
+
+/* Push bytes into the ring buffer. */
+func ringBufferWrite(bytes []byte, n uint, rb *ringBuffer) {
+	if rb.pos_ == 0 && uint32(n) < rb.tail_size_ {
+		/* Special case for the first write: to process the first block, we don't
+		   need to allocate the whole ring-buffer and we don't need the tail
+		   either. However, we do this memory usage optimization only if the
+		   first write is less than the tail size, which is also the input block
+		   size, otherwise it is likely that other blocks will follow and we
+		   will need to reallocate to the full size anyway. */
+		rb.pos_ = uint32(n)
+
+		ringBufferInitBuffer(rb.pos_, rb)
+		copy(rb.buffer_, bytes[:n])
+		return
+	}
+
+	if rb.cur_size_ < rb.total_size_ {
+		/* Lazily allocate the full buffer. */
+		ringBufferInitBuffer(rb.total_size_, rb)
+
+		/* Initialize the last two bytes to zero, so that we don't have to worry
+		   later when we copy the last two bytes to the first two positions. */
+		rb.buffer_[rb.size_-2] = 0
+
+		rb.buffer_[rb.size_-1] = 0
+	}
+	{
+		var masked_pos uint = uint(rb.pos_ & rb.mask_)
+
+		/* The length of the writes is limited so that we do not need to worry
+		   about a write */
+		ringBufferWriteTail(bytes, n, rb)
+
+		if uint32(masked_pos+n) <= rb.size_ {
+			/* A single write fits. */
+			copy(rb.buffer_[masked_pos:], bytes[:n])
+		} else {
+			/* Split into two writes.
+			   Copy into the end of the buffer, including the tail buffer. */
+			copy(rb.buffer_[masked_pos:], bytes[:brotli_min_size_t(n, uint(rb.total_size_-uint32(masked_pos)))])
+
+			/* Copy into the beginning of the buffer */
+			copy(rb.buffer_, bytes[rb.size_-uint32(masked_pos):][:uint32(n)-(rb.size_-uint32(masked_pos))])
+		}
+	}
+	{
+		var not_first_lap bool = rb.pos_&(1<<31) != 0
+		var rb_pos_mask uint32 = (1 << 31) - 1
+		rb.data_[0] = rb.buffer_[rb.size_-2]
+		rb.data_[1] = rb.buffer_[rb.size_-1]
+		rb.pos_ = (rb.pos_ & rb_pos_mask) + uint32(uint32(n)&rb_pos_mask)
+		if not_first_lap {
+			/* Wrap, but preserve not-a-first-lap feature. */
+			rb.pos_ |= 1 << 31
+		}
+	}
+}

vendor/github.com/andybalholm/brotli/state.go

@@ -0,0 +1,294 @@
+package brotli
+
+import "io"
+
+/* Copyright 2015 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Brotli state for partial streaming decoding. */
+const (
+	stateUninited = iota
+	stateLargeWindowBits
+	stateInitialize
+	stateMetablockBegin
+	stateMetablockHeader
+	stateMetablockHeader2
+	stateContextModes
+	stateCommandBegin
+	stateCommandInner
+	stateCommandPostDecodeLiterals
+	stateCommandPostWrapCopy
+	stateUncompressed
+	stateMetadata
+	stateCommandInnerWrite
+	stateMetablockDone
+	stateCommandPostWrite1
+	stateCommandPostWrite2
+	stateHuffmanCode0
+	stateHuffmanCode1
+	stateHuffmanCode2
+	stateHuffmanCode3
+	stateContextMap1
+	stateContextMap2
+	stateTreeGroup
+	stateDone
+)
+
+const (
+	stateMetablockHeaderNone = iota
+	stateMetablockHeaderEmpty
+	stateMetablockHeaderNibbles
+	stateMetablockHeaderSize
+	stateMetablockHeaderUncompressed
+	stateMetablockHeaderReserved
+	stateMetablockHeaderBytes
+	stateMetablockHeaderMetadata
+)
+
+const (
+	stateUncompressedNone = iota
+	stateUncompressedWrite
+)
+
+const (
+	stateTreeGroupNone = iota
+	stateTreeGroupLoop
+)
+
+const (
+	stateContextMapNone = iota
+	stateContextMapReadPrefix
+	stateContextMapHuffman
+	stateContextMapDecode
+	stateContextMapTransform
+)
+
+const (
+	stateHuffmanNone = iota
+	stateHuffmanSimpleSize
+	stateHuffmanSimpleRead
+	stateHuffmanSimpleBuild
+	stateHuffmanComplex
+	stateHuffmanLengthSymbols
+)
+
+const (
+	stateDecodeUint8None = iota
+	stateDecodeUint8Short
+	stateDecodeUint8Long
+)
+
+const (
+	stateReadBlockLengthNone = iota
+	stateReadBlockLengthSuffix
+)
+
+type Reader struct {
+	src io.Reader
+	buf []byte // scratch space for reading from src
+	in  []byte // current chunk to decode; usually aliases buf
+
+	state        int
+	loop_counter int
+	br           bitReader
+	buffer       struct {
+		u64 uint64
+		u8  [8]byte
+	}
+	buffer_length               uint32
+	pos                         int
+	max_backward_distance       int
+	max_distance                int
+	ringbuffer_size             int
+	ringbuffer_mask             int
+	dist_rb_idx                 int
+	dist_rb                     [4]int
+	error_code                  int
+	sub_loop_counter            uint32
+	ringbuffer                  []byte
+	ringbuffer_end              []byte
+	htree_command               []huffmanCode
+	context_lookup              []byte
+	context_map_slice           []byte
+	dist_context_map_slice      []byte
+	literal_hgroup              huffmanTreeGroup
+	insert_copy_hgroup          huffmanTreeGroup
+	distance_hgroup             huffmanTreeGroup
+	block_type_trees            []huffmanCode
+	block_len_trees             []huffmanCode
+	trivial_literal_context     int
+	distance_context            int
+	meta_block_remaining_len    int
+	block_length_index          uint32
+	block_length                [3]uint32
+	num_block_types             [3]uint32
+	block_type_rb               [6]uint32
+	distance_postfix_bits       uint32
+	num_direct_distance_codes   uint32
+	distance_postfix_mask       int
+	num_dist_htrees             uint32
+	dist_context_map            []byte
+	literal_htree               []huffmanCode
+	dist_htree_index            byte
+	repeat_code_len             uint32
+	prev_code_len               uint32
+	copy_length                 int
+	distance_code               int
+	rb_roundtrips               uint
+	partial_pos_out             uint
+	symbol                      uint32
+	repeat                      uint32
+	space                       uint32
+	table                       [32]huffmanCode
+	symbol_lists                symbolList
+	symbols_lists_array         [huffmanMaxCodeLength + 1 + numCommandSymbols]uint16
+	next_symbol                 [32]int
+	code_length_code_lengths    [codeLengthCodes]byte
+	code_length_histo           [16]uint16
+	htree_index                 int
+	next                        []huffmanCode
+	context_index               uint32
+	max_run_length_prefix       uint32
+	code                        uint32
+	context_map_table           [huffmanMaxSize272]huffmanCode
+	substate_metablock_header   int
+	substate_tree_group         int
+	substate_context_map        int
+	substate_uncompressed       int
+	substate_huffman            int
+	substate_decode_uint8       int
+	substate_read_block_length  int
+	is_last_metablock           uint
+	is_uncompressed             uint
+	is_metadata                 uint
+	should_wrap_ringbuffer      uint
+	canny_ringbuffer_allocation uint
+	large_window                bool
+	size_nibbles                uint
+	window_bits                 uint32
+	new_ringbuffer_size         int
+	num_literal_htrees          uint32
+	context_map                 []byte
+	context_modes               []byte
+	dictionary                  *dictionary
+	transforms                  *transforms
+	trivial_literal_contexts    [8]uint32
+}
+
+func decoderStateInit(s *Reader) bool {
+	s.error_code = 0 /* BROTLI_DECODER_NO_ERROR */
+
+	initBitReader(&s.br)
+	s.state = stateUninited
+	s.large_window = false
+	s.substate_metablock_header = stateMetablockHeaderNone
+	s.substate_tree_group = stateTreeGroupNone
+	s.substate_context_map = stateContextMapNone
+	s.substate_uncompressed = stateUncompressedNone
+	s.substate_huffman = stateHuffmanNone
+	s.substate_decode_uint8 = stateDecodeUint8None
+	s.substate_read_block_length = stateReadBlockLengthNone
+
+	s.buffer_length = 0
+	s.loop_counter = 0
+	s.pos = 0
+	s.rb_roundtrips = 0
+	s.partial_pos_out = 0
+
+	s.block_type_trees = nil
+	s.block_len_trees = nil
+	s.ringbuffer_size = 0
+	s.new_ringbuffer_size = 0
+	s.ringbuffer_mask = 0
+
+	s.context_map = nil
+	s.context_modes = nil
+	s.dist_context_map = nil
+	s.context_map_slice = nil
+	s.dist_context_map_slice = nil
+
+	s.sub_loop_counter = 0
+
+	s.literal_hgroup.codes = nil
+	s.literal_hgroup.htrees = nil
+	s.insert_copy_hgroup.codes = nil
+	s.insert_copy_hgroup.htrees = nil
+	s.distance_hgroup.codes = nil
+	s.distance_hgroup.htrees = nil
+
+	s.is_last_metablock = 0
+	s.is_uncompressed = 0
+	s.is_metadata = 0
+	s.should_wrap_ringbuffer = 0
+	s.canny_ringbuffer_allocation = 1
+
+	s.window_bits = 0
+	s.max_distance = 0
+	s.dist_rb[0] = 16
+	s.dist_rb[1] = 15
+	s.dist_rb[2] = 11
+	s.dist_rb[3] = 4
+	s.dist_rb_idx = 0
+	s.block_type_trees = nil
+	s.block_len_trees = nil
+
+	s.symbol_lists.storage = s.symbols_lists_array[:]
+	s.symbol_lists.offset = huffmanMaxCodeLength + 1
+
+	s.dictionary = getDictionary()
+	s.transforms = getTransforms()
+
+	return true
+}
+
+func decoderStateMetablockBegin(s *Reader) {
+	s.meta_block_remaining_len = 0
+	s.block_length[0] = 1 << 24
+	s.block_length[1] = 1 << 24
+	s.block_length[2] = 1 << 24
+	s.num_block_types[0] = 1
+	s.num_block_types[1] = 1
+	s.num_block_types[2] = 1
+	s.block_type_rb[0] = 1
+	s.block_type_rb[1] = 0
+	s.block_type_rb[2] = 1
+	s.block_type_rb[3] = 0
+	s.block_type_rb[4] = 1
+	s.block_type_rb[5] = 0
+	s.context_map = nil
+	s.context_modes = nil
+	s.dist_context_map = nil
+	s.context_map_slice = nil
+	s.literal_htree = nil
+	s.dist_context_map_slice = nil
+	s.dist_htree_index = 0
+	s.context_lookup = nil
+	s.literal_hgroup.codes = nil
+	s.literal_hgroup.htrees = nil
+	s.insert_copy_hgroup.codes = nil
+	s.insert_copy_hgroup.htrees = nil
+	s.distance_hgroup.codes = nil
+	s.distance_hgroup.htrees = nil
+}
+
+func decoderStateCleanupAfterMetablock(s *Reader) {
+	s.context_modes = nil
+	s.context_map = nil
+	s.dist_context_map = nil
+	s.literal_hgroup.htrees = nil
+	s.insert_copy_hgroup.htrees = nil
+	s.distance_hgroup.htrees = nil
+}
+
+func decoderHuffmanTreeGroupInit(s *Reader, group *huffmanTreeGroup, alphabet_size uint32, max_symbol uint32, ntrees uint32) bool {
+	var max_table_size uint = uint(kMaxHuffmanTableSize[(alphabet_size+31)>>5])
+	group.alphabet_size = uint16(alphabet_size)
+	group.max_symbol = uint16(max_symbol)
+	group.num_htrees = uint16(ntrees)
+	group.htrees = make([][]huffmanCode, ntrees)
+	group.codes = make([]huffmanCode, (uint(ntrees) * max_table_size))
+	return !(group.codes == nil)
+}

vendor/github.com/andybalholm/brotli/static_dict.go

@@ -0,0 +1,662 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Class to model the static dictionary. */
+
+const maxStaticDictionaryMatchLen = 37
+
+const kInvalidMatch uint32 = 0xFFFFFFF
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+func hash(data []byte) uint32 {
+	var h uint32 = binary.LittleEndian.Uint32(data) * kDictHashMul32
+
+	/* The higher bits contain more mixture from the multiplication,
+	   so we take our results from there. */
+	return h >> uint(32-kDictNumBits)
+}
+
+func addMatch(distance uint, len uint, len_code uint, matches []uint32) {
+	var match uint32 = uint32((distance << 5) + len_code)
+	matches[len] = brotli_min_uint32_t(matches[len], match)
+}
+
+func dictMatchLength(dict *dictionary, data []byte, id uint, len uint, maxlen uint) uint {
+	var offset uint = uint(dict.offsets_by_length[len]) + len*id
+	return findMatchLengthWithLimit(dict.data[offset:], data, brotli_min_size_t(uint(len), maxlen))
+}
+
+func isMatch(d *dictionary, w dictWord, data []byte, max_length uint) bool {
+	if uint(w.len) > max_length {
+		return false
+	} else {
+		var offset uint = uint(d.offsets_by_length[w.len]) + uint(w.len)*uint(w.idx)
+		var dict []byte = d.data[offset:]
+		if w.transform == 0 {
+			/* Match against base dictionary word. */
+			return findMatchLengthWithLimit(dict, data, uint(w.len)) == uint(w.len)
+		} else if w.transform == 10 {
+			/* Match against uppercase first transform.
+			   Note that there are only ASCII uppercase words in the lookup table. */
+			return dict[0] >= 'a' && dict[0] <= 'z' && (dict[0]^32) == data[0] && findMatchLengthWithLimit(dict[1:], data[1:], uint(w.len)-1) == uint(w.len-1)
+		} else {
+			/* Match against uppercase all transform.
+			   Note that there are only ASCII uppercase words in the lookup table. */
+			var i uint
+			for i = 0; i < uint(w.len); i++ {
+				if dict[i] >= 'a' && dict[i] <= 'z' {
+					if (dict[i] ^ 32) != data[i] {
+						return false
+					}
+				} else {
+					if dict[i] != data[i] {
+						return false
+					}
+				}
+			}
+
+			return true
+		}
+	}
+}
+
+func findAllStaticDictionaryMatches(dict *encoderDictionary, data []byte, min_length uint, max_length uint, matches []uint32) bool {
+	var has_found_match bool = false
+	{
+		var offset uint = uint(dict.buckets[hash(data)])
+		var end bool = offset == 0
+		for !end {
+			w := dict.dict_words[offset]
+			offset++
+			var l uint = uint(w.len) & 0x1F
+			var n uint = uint(1) << dict.words.size_bits_by_length[l]
+			var id uint = uint(w.idx)
+			end = !(w.len&0x80 == 0)
+			w.len = byte(l)
+			if w.transform == 0 {
+				var matchlen uint = dictMatchLength(dict.words, data, id, l, max_length)
+				var s []byte
+				var minlen uint
+				var maxlen uint
+				var len uint
+
+				/* Transform "" + BROTLI_TRANSFORM_IDENTITY + "" */
+				if matchlen == l {
+					addMatch(id, l, l, matches)
+					has_found_match = true
+				}
+
+				/* Transforms "" + BROTLI_TRANSFORM_OMIT_LAST_1 + "" and
+				   "" + BROTLI_TRANSFORM_OMIT_LAST_1 + "ing " */
+				if matchlen >= l-1 {
+					addMatch(id+12*n, l-1, l, matches)
+					if l+2 < max_length && data[l-1] == 'i' && data[l] == 'n' && data[l+1] == 'g' && data[l+2] == ' ' {
+						addMatch(id+49*n, l+3, l, matches)
+					}
+
+					has_found_match = true
+				}
+
+				/* Transform "" + BROTLI_TRANSFORM_OMIT_LAST_# + "" (# = 2 .. 9) */
+				minlen = min_length
+
+				if l > 9 {
+					minlen = brotli_max_size_t(minlen, l-9)
+				}
+				maxlen = brotli_min_size_t(matchlen, l-2)
+				for len = minlen; len <= maxlen; len++ {
+					var cut uint = l - len
+					var transform_id uint = (cut << 2) + uint((dict.cutoffTransforms>>(cut*6))&0x3F)
+					addMatch(id+transform_id*n, uint(len), l, matches)
+					has_found_match = true
+				}
+
+				if matchlen < l || l+6 >= max_length {
+					continue
+				}
+
+				s = data[l:]
+
+				/* Transforms "" + BROTLI_TRANSFORM_IDENTITY + <suffix> */
+				if s[0] == ' ' {
+					addMatch(id+n, l+1, l, matches)
+					if s[1] == 'a' {
+						if s[2] == ' ' {
+							addMatch(id+28*n, l+3, l, matches)
+						} else if s[2] == 's' {
+							if s[3] == ' ' {
+								addMatch(id+46*n, l+4, l, matches)
+							}
+						} else if s[2] == 't' {
+							if s[3] == ' ' {
+								addMatch(id+60*n, l+4, l, matches)
+							}
+						} else if s[2] == 'n' {
+							if s[3] == 'd' && s[4] == ' ' {
+								addMatch(id+10*n, l+5, l, matches)
+							}
+						}
+					} else if s[1] == 'b' {
+						if s[2] == 'y' && s[3] == ' ' {
+							addMatch(id+38*n, l+4, l, matches)
+						}
+					} else if s[1] == 'i' {
+						if s[2] == 'n' {
+							if s[3] == ' ' {
+								addMatch(id+16*n, l+4, l, matches)
+							}
+						} else if s[2] == 's' {
+							if s[3] == ' ' {
+								addMatch(id+47*n, l+4, l, matches)
+							}
+						}
+					} else if s[1] == 'f' {
+						if s[2] == 'o' {
+							if s[3] == 'r' && s[4] == ' ' {
+								addMatch(id+25*n, l+5, l, matches)
+							}
+						} else if s[2] == 'r' {
+							if s[3] == 'o' && s[4] == 'm' && s[5] == ' ' {
+								addMatch(id+37*n, l+6, l, matches)
+							}
+						}
+					} else if s[1] == 'o' {
+						if s[2] == 'f' {
+							if s[3] == ' ' {
+								addMatch(id+8*n, l+4, l, matches)
+							}
+						} else if s[2] == 'n' {
+							if s[3] == ' ' {
+								addMatch(id+45*n, l+4, l, matches)
+							}
+						}
+					} else if s[1] == 'n' {
+						if s[2] == 'o' && s[3] == 't' && s[4] == ' ' {
+							addMatch(id+80*n, l+5, l, matches)
+						}
+					} else if s[1] == 't' {
+						if s[2] == 'h' {
+							if s[3] == 'e' {
+								if s[4] == ' ' {
+									addMatch(id+5*n, l+5, l, matches)
+								}
+							} else if s[3] == 'a' {
+								if s[4] == 't' && s[5] == ' ' {
+									addMatch(id+29*n, l+6, l, matches)
+								}
+							}
+						} else if s[2] == 'o' {
+							if s[3] == ' ' {
+								addMatch(id+17*n, l+4, l, matches)
+							}
+						}
+					} else if s[1] == 'w' {
+						if s[2] == 'i' && s[3] == 't' && s[4] == 'h' && s[5] == ' ' {
+							addMatch(id+35*n, l+6, l, matches)
+						}
+					}
+				} else if s[0] == '"' {
+					addMatch(id+19*n, l+1, l, matches)
+					if s[1] == '>' {
+						addMatch(id+21*n, l+2, l, matches)
+					}
+				} else if s[0] == '.' {
+					addMatch(id+20*n, l+1, l, matches)
+					if s[1] == ' ' {
+						addMatch(id+31*n, l+2, l, matches)
+						if s[2] == 'T' && s[3] == 'h' {
+							if s[4] == 'e' {
+								if s[5] == ' ' {
+									addMatch(id+43*n, l+6, l, matches)
+								}
+							} else if s[4] == 'i' {
+								if s[5] == 's' && s[6] == ' ' {
+									addMatch(id+75*n, l+7, l, matches)
+								}
+							}
+						}
+					}
+				} else if s[0] == ',' {
+					addMatch(id+76*n, l+1, l, matches)
+					if s[1] == ' ' {
+						addMatch(id+14*n, l+2, l, matches)
+					}
+				} else if s[0] == '\n' {
+					addMatch(id+22*n, l+1, l, matches)
+					if s[1] == '\t' {
+						addMatch(id+50*n, l+2, l, matches)
+					}
+				} else if s[0] == ']' {
+					addMatch(id+24*n, l+1, l, matches)
+				} else if s[0] == '\'' {
+					addMatch(id+36*n, l+1, l, matches)
+				} else if s[0] == ':' {
+					addMatch(id+51*n, l+1, l, matches)
+				} else if s[0] == '(' {
+					addMatch(id+57*n, l+1, l, matches)
+				} else if s[0] == '=' {
+					if s[1] == '"' {
+						addMatch(id+70*n, l+2, l, matches)
+					} else if s[1] == '\'' {
+						addMatch(id+86*n, l+2, l, matches)
+					}
+				} else if s[0] == 'a' {
+					if s[1] == 'l' && s[2] == ' ' {
+						addMatch(id+84*n, l+3, l, matches)
+					}
+				} else if s[0] == 'e' {
+					if s[1] == 'd' {
+						if s[2] == ' ' {
+							addMatch(id+53*n, l+3, l, matches)
+						}
+					} else if s[1] == 'r' {
+						if s[2] == ' ' {
+							addMatch(id+82*n, l+3, l, matches)
+						}
+					} else if s[1] == 's' {
+						if s[2] == 't' && s[3] == ' ' {
+							addMatch(id+95*n, l+4, l, matches)
+						}
+					}
+				} else if s[0] == 'f' {
+					if s[1] == 'u' && s[2] == 'l' && s[3] == ' ' {
+						addMatch(id+90*n, l+4, l, matches)
+					}
+				} else if s[0] == 'i' {
+					if s[1] == 'v' {
+						if s[2] == 'e' && s[3] == ' ' {
+							addMatch(id+92*n, l+4, l, matches)
+						}
+					} else if s[1] == 'z' {
+						if s[2] == 'e' && s[3] == ' ' {
+							addMatch(id+100*n, l+4, l, matches)
+						}
+					}
+				} else if s[0] == 'l' {
+					if s[1] == 'e' {
+						if s[2] == 's' && s[3] == 's' && s[4] == ' ' {
+							addMatch(id+93*n, l+5, l, matches)
+						}
+					} else if s[1] == 'y' {
+						if s[2] == ' ' {
+							addMatch(id+61*n, l+3, l, matches)
+						}
+					}
+				} else if s[0] == 'o' {
+					if s[1] == 'u' && s[2] == 's' && s[3] == ' ' {
+						addMatch(id+106*n, l+4, l, matches)
+					}
+				}
+			} else {
+				var is_all_caps bool = (w.transform != transformUppercaseFirst)
+				/* Set is_all_caps=0 for BROTLI_TRANSFORM_UPPERCASE_FIRST and
+				    is_all_caps=1 otherwise (BROTLI_TRANSFORM_UPPERCASE_ALL)
+				transform. */
+
+				var s []byte
+				if !isMatch(dict.words, w, data, max_length) {
+					continue
+				}
+
+				/* Transform "" + kUppercase{First,All} + "" */
+				var tmp int
+				if is_all_caps {
+					tmp = 44
+				} else {
+					tmp = 9
+				}
+				addMatch(id+uint(tmp)*n, l, l, matches)
+
+				has_found_match = true
+				if l+1 >= max_length {
+					continue
+				}
+
+				/* Transforms "" + kUppercase{First,All} + <suffix> */
+				s = data[l:]
+
+				if s[0] == ' ' {
+					var tmp int
+					if is_all_caps {
+						tmp = 68
+					} else {
+						tmp = 4
+					}
+					addMatch(id+uint(tmp)*n, l+1, l, matches)
+				} else if s[0] == '"' {
+					var tmp int
+					if is_all_caps {
+						tmp = 87
+					} else {
+						tmp = 66
+					}
+					addMatch(id+uint(tmp)*n, l+1, l, matches)
+					if s[1] == '>' {
+						var tmp int
+						if is_all_caps {
+							tmp = 97
+						} else {
+							tmp = 69
+						}
+						addMatch(id+uint(tmp)*n, l+2, l, matches)
+					}
+				} else if s[0] == '.' {
+					var tmp int
+					if is_all_caps {
+						tmp = 101
+					} else {
+						tmp = 79
+					}
+					addMatch(id+uint(tmp)*n, l+1, l, matches)
+					if s[1] == ' ' {
+						var tmp int
+						if is_all_caps {
+							tmp = 114
+						} else {
+							tmp = 88
+						}
+						addMatch(id+uint(tmp)*n, l+2, l, matches)
+					}
+				} else if s[0] == ',' {
+					var tmp int
+					if is_all_caps {
+						tmp = 112
+					} else {
+						tmp = 99
+					}
+					addMatch(id+uint(tmp)*n, l+1, l, matches)
+					if s[1] == ' ' {
+						var tmp int
+						if is_all_caps {
+							tmp = 107
+						} else {
+							tmp = 58
+						}
+						addMatch(id+uint(tmp)*n, l+2, l, matches)
+					}
+				} else if s[0] == '\'' {
+					var tmp int
+					if is_all_caps {
+						tmp = 94
+					} else {
+						tmp = 74
+					}
+					addMatch(id+uint(tmp)*n, l+1, l, matches)
+				} else if s[0] == '(' {
+					var tmp int
+					if is_all_caps {
+						tmp = 113
+					} else {
+						tmp = 78
+					}
+					addMatch(id+uint(tmp)*n, l+1, l, matches)
+				} else if s[0] == '=' {
+					if s[1] == '"' {
+						var tmp int
+						if is_all_caps {
+							tmp = 105
+						} else {
+							tmp = 104
+						}
+						addMatch(id+uint(tmp)*n, l+2, l, matches)
+					} else if s[1] == '\'' {
+						var tmp int
+						if is_all_caps {
+							tmp = 116
+						} else {
+							tmp = 108
+						}
+						addMatch(id+uint(tmp)*n, l+2, l, matches)
+					}
+				}
+			}
+		}
+	}
+
+	/* Transforms with prefixes " " and "." */
+	if max_length >= 5 && (data[0] == ' ' || data[0] == '.') {
+		var is_space bool = (data[0] == ' ')
+		var offset uint = uint(dict.buckets[hash(data[1:])])
+		var end bool = offset == 0
+		for !end {
+			w := dict.dict_words[offset]
+			offset++
+			var l uint = uint(w.len) & 0x1F
+			var n uint = uint(1) << dict.words.size_bits_by_length[l]
+			var id uint = uint(w.idx)
+			end = !(w.len&0x80 == 0)
+			w.len = byte(l)
+			if w.transform == 0 {
+				var s []byte
+				if !isMatch(dict.words, w, data[1:], max_length-1) {
+					continue
+				}
+
+				/* Transforms " " + BROTLI_TRANSFORM_IDENTITY + "" and
+				   "." + BROTLI_TRANSFORM_IDENTITY + "" */
+				var tmp int
+				if is_space {
+					tmp = 6
+				} else {
+					tmp = 32
+				}
+				addMatch(id+uint(tmp)*n, l+1, l, matches)
+
+				has_found_match = true
+				if l+2 >= max_length {
+					continue
+				}
+
+				/* Transforms " " + BROTLI_TRANSFORM_IDENTITY + <suffix> and
+				   "." + BROTLI_TRANSFORM_IDENTITY + <suffix>
+				*/
+				s = data[l+1:]
+
+				if s[0] == ' ' {
+					var tmp int
+					if is_space {
+						tmp = 2
+					} else {
+						tmp = 77
+					}
+					addMatch(id+uint(tmp)*n, l+2, l, matches)
+				} else if s[0] == '(' {
+					var tmp int
+					if is_space {
+						tmp = 89
+					} else {
+						tmp = 67
+					}
+					addMatch(id+uint(tmp)*n, l+2, l, matches)
+				} else if is_space {
+					if s[0] == ',' {
+						addMatch(id+103*n, l+2, l, matches)
+						if s[1] == ' ' {
+							addMatch(id+33*n, l+3, l, matches)
+						}
+					} else if s[0] == '.' {
+						addMatch(id+71*n, l+2, l, matches)
+						if s[1] == ' ' {
+							addMatch(id+52*n, l+3, l, matches)
+						}
+					} else if s[0] == '=' {
+						if s[1] == '"' {
+							addMatch(id+81*n, l+3, l, matches)
+						} else if s[1] == '\'' {
+							addMatch(id+98*n, l+3, l, matches)
+						}
+					}
+				}
+			} else if is_space {
+				var is_all_caps bool = (w.transform != transformUppercaseFirst)
+				/* Set is_all_caps=0 for BROTLI_TRANSFORM_UPPERCASE_FIRST and
+				    is_all_caps=1 otherwise (BROTLI_TRANSFORM_UPPERCASE_ALL)
+				transform. */
+
+				var s []byte
+				if !isMatch(dict.words, w, data[1:], max_length-1) {
+					continue
+				}
+
+				/* Transforms " " + kUppercase{First,All} + "" */
+				var tmp int
+				if is_all_caps {
+					tmp = 85
+				} else {
+					tmp = 30
+				}
+				addMatch(id+uint(tmp)*n, l+1, l, matches)
+
+				has_found_match = true
+				if l+2 >= max_length {
+					continue
+				}
+
+				/* Transforms " " + kUppercase{First,All} + <suffix> */
+				s = data[l+1:]
+
+				if s[0] == ' ' {
+					var tmp int
+					if is_all_caps {
+						tmp = 83
+					} else {
+						tmp = 15
+					}
+					addMatch(id+uint(tmp)*n, l+2, l, matches)
+				} else if s[0] == ',' {
+					if !is_all_caps {
+						addMatch(id+109*n, l+2, l, matches)
+					}
+
+					if s[1] == ' ' {
+						var tmp int
+						if is_all_caps {
+							tmp = 111
+						} else {
+							tmp = 65
+						}
+						addMatch(id+uint(tmp)*n, l+3, l, matches)
+					}
+				} else if s[0] == '.' {
+					var tmp int
+					if is_all_caps {
+						tmp = 115
+					} else {
+						tmp = 96
+					}
+					addMatch(id+uint(tmp)*n, l+2, l, matches)
+					if s[1] == ' ' {
+						var tmp int
+						if is_all_caps {
+							tmp = 117
+						} else {
+							tmp = 91
+						}
+						addMatch(id+uint(tmp)*n, l+3, l, matches)
+					}
+				} else if s[0] == '=' {
+					if s[1] == '"' {
+						var tmp int
+						if is_all_caps {
+							tmp = 110
+						} else {
+							tmp = 118
+						}
+						addMatch(id+uint(tmp)*n, l+3, l, matches)
+					} else if s[1] == '\'' {
+						var tmp int
+						if is_all_caps {
+							tmp = 119
+						} else {
+							tmp = 120
+						}
+						addMatch(id+uint(tmp)*n, l+3, l, matches)
+					}
+				}
+			}
+		}
+	}
+
+	if max_length >= 6 {
+		/* Transforms with prefixes "e ", "s ", ", " and "\xC2\xA0" */
+		if (data[1] == ' ' && (data[0] == 'e' || data[0] == 's' || data[0] == ',')) || (data[0] == 0xC2 && data[1] == 0xA0) {
+			var offset uint = uint(dict.buckets[hash(data[2:])])
+			var end bool = offset == 0
+			for !end {
+				w := dict.dict_words[offset]
+				offset++
+				var l uint = uint(w.len) & 0x1F
+				var n uint = uint(1) << dict.words.size_bits_by_length[l]
+				var id uint = uint(w.idx)
+				end = !(w.len&0x80 == 0)
+				w.len = byte(l)
+				if w.transform == 0 && isMatch(dict.words, w, data[2:], max_length-2) {
+					if data[0] == 0xC2 {
+						addMatch(id+102*n, l+2, l, matches)
+						has_found_match = true
+					} else if l+2 < max_length && data[l+2] == ' ' {
+						var t uint = 13
+						if data[0] == 'e' {
+							t = 18
+						} else if data[0] == 's' {
+							t = 7
+						}
+						addMatch(id+t*n, l+3, l, matches)
+						has_found_match = true
+					}
+				}
+			}
+		}
+	}
+
+	if max_length >= 9 {
+		/* Transforms with prefixes " the " and ".com/" */
+		if (data[0] == ' ' && data[1] == 't' && data[2] == 'h' && data[3] == 'e' && data[4] == ' ') || (data[0] == '.' && data[1] == 'c' && data[2] == 'o' && data[3] == 'm' && data[4] == '/') {
+			var offset uint = uint(dict.buckets[hash(data[5:])])
+			var end bool = offset == 0
+			for !end {
+				w := dict.dict_words[offset]
+				offset++
+				var l uint = uint(w.len) & 0x1F
+				var n uint = uint(1) << dict.words.size_bits_by_length[l]
+				var id uint = uint(w.idx)
+				end = !(w.len&0x80 == 0)
+				w.len = byte(l)
+				if w.transform == 0 && isMatch(dict.words, w, data[5:], max_length-5) {
+					var tmp int
+					if data[0] == ' ' {
+						tmp = 41
+					} else {
+						tmp = 72
+					}
+					addMatch(id+uint(tmp)*n, l+5, l, matches)
+					has_found_match = true
+					if l+5 < max_length {
+						var s []byte = data[l+5:]
+						if data[0] == ' ' {
+							if l+8 < max_length && s[0] == ' ' && s[1] == 'o' && s[2] == 'f' && s[3] == ' ' {
+								addMatch(id+62*n, l+9, l, matches)
+								if l+12 < max_length && s[4] == 't' && s[5] == 'h' && s[6] == 'e' && s[7] == ' ' {
+									addMatch(id+73*n, l+13, l, matches)
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
+	return has_found_match
+}

vendor/github.com/andybalholm/brotli/symbol_list.go

@@ -0,0 +1,22 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Utilities for building Huffman decoding tables. */
+
+type symbolList struct {
+	storage []uint16
+	offset  int
+}
+
+func symbolListGet(sl symbolList, i int) uint16 {
+	return sl.storage[i+sl.offset]
+}
+
+func symbolListPut(sl symbolList, i int, val uint16) {
+	sl.storage[i+sl.offset] = val
+}

vendor/github.com/andybalholm/brotli/transform.go

@@ -0,0 +1,641 @@
+package brotli
+
+const (
+	transformIdentity       = 0
+	transformOmitLast1      = 1
+	transformOmitLast2      = 2
+	transformOmitLast3      = 3
+	transformOmitLast4      = 4
+	transformOmitLast5      = 5
+	transformOmitLast6      = 6
+	transformOmitLast7      = 7
+	transformOmitLast8      = 8
+	transformOmitLast9      = 9
+	transformUppercaseFirst = 10
+	transformUppercaseAll   = 11
+	transformOmitFirst1     = 12
+	transformOmitFirst2     = 13
+	transformOmitFirst3     = 14
+	transformOmitFirst4     = 15
+	transformOmitFirst5     = 16
+	transformOmitFirst6     = 17
+	transformOmitFirst7     = 18
+	transformOmitFirst8     = 19
+	transformOmitFirst9     = 20
+	transformShiftFirst     = 21
+	transformShiftAll       = 22 + iota - 22
+	numTransformTypes
+)
+
+const transformsMaxCutOff = transformOmitLast9
+
+type transforms struct {
+	prefix_suffix_size uint16
+	prefix_suffix      []byte
+	prefix_suffix_map  []uint16
+	num_transforms     uint32
+	transforms         []byte
+	params             []byte
+	cutOffTransforms   [transformsMaxCutOff + 1]int16
+}
+
+func transformPrefixId(t *transforms, I int) byte {
+	return t.transforms[(I*3)+0]
+}
+
+func transformType(t *transforms, I int) byte {
+	return t.transforms[(I*3)+1]
+}
+
+func transformSuffixId(t *transforms, I int) byte {
+	return t.transforms[(I*3)+2]
+}
+
+func transformPrefix(t *transforms, I int) []byte {
+	return t.prefix_suffix[t.prefix_suffix_map[transformPrefixId(t, I)]:]
+}
+
+func transformSuffix(t *transforms, I int) []byte {
+	return t.prefix_suffix[t.prefix_suffix_map[transformSuffixId(t, I)]:]
+}
+
+/* RFC 7932 transforms string data */
+const kPrefixSuffix string = "\001 \002, \010 of the \004 of \002s \001.\005 and \004 " + "in \001\"\004 to \002\">\001\n\002. \001]\005 for \003 a \006 " + "that \001'\006 with \006 from \004 by \001(\006. T" + "he \004 on \004 as \004 is \004ing \002\n\t\001:\003ed " + "\002=\"\004 at \003ly \001,\002='\005.com/\007. This \005" + " not \003er \003al \004ful \004ive \005less \004es" + "t \004ize \002\xc2\xa0\004ous \005 the \002e \000"
+
+var kPrefixSuffixMap = [50]uint16{
+	0x00,
+	0x02,
+	0x05,
+	0x0E,
+	0x13,
+	0x16,
+	0x18,
+	0x1E,
+	0x23,
+	0x25,
+	0x2A,
+	0x2D,
+	0x2F,
+	0x32,
+	0x34,
+	0x3A,
+	0x3E,
+	0x45,
+	0x47,
+	0x4E,
+	0x55,
+	0x5A,
+	0x5C,
+	0x63,
+	0x68,
+	0x6D,
+	0x72,
+	0x77,
+	0x7A,
+	0x7C,
+	0x80,
+	0x83,
+	0x88,
+	0x8C,
+	0x8E,
+	0x91,
+	0x97,
+	0x9F,
+	0xA5,
+	0xA9,
+	0xAD,
+	0xB2,
+	0xB7,
+	0xBD,
+	0xC2,
+	0xC7,
+	0xCA,
+	0xCF,
+	0xD5,
+	0xD8,
+}
+
+/* RFC 7932 transforms */
+var kTransformsData = []byte{
+	49,
+	transformIdentity,
+	49,
+	49,
+	transformIdentity,
+	0,
+	0,
+	transformIdentity,
+	0,
+	49,
+	transformOmitFirst1,
+	49,
+	49,
+	transformUppercaseFirst,
+	0,
+	49,
+	transformIdentity,
+	47,
+	0,
+	transformIdentity,
+	49,
+	4,
+	transformIdentity,
+	0,
+	49,
+	transformIdentity,
+	3,
+	49,
+	transformUppercaseFirst,
+	49,
+	49,
+	transformIdentity,
+	6,
+	49,
+	transformOmitFirst2,
+	49,
+	49,
+	transformOmitLast1,
+	49,
+	1,
+	transformIdentity,
+	0,
+	49,
+	transformIdentity,
+	1,
+	0,
+	transformUppercaseFirst,
+	0,
+	49,
+	transformIdentity,
+	7,
+	49,
+	transformIdentity,
+	9,
+	48,
+	transformIdentity,
+	0,
+	49,
+	transformIdentity,
+	8,
+	49,
+	transformIdentity,
+	5,
+	49,
+	transformIdentity,
+	10,
+	49,
+	transformIdentity,
+	11,
+	49,
+	transformOmitLast3,
+	49,
+	49,
+	transformIdentity,
+	13,
+	49,
+	transformIdentity,
+	14,
+	49,
+	transformOmitFirst3,
+	49,
+	49,
+	transformOmitLast2,
+	49,
+	49,
+	transformIdentity,
+	15,
+	49,
+	transformIdentity,
+	16,
+	0,
+	transformUppercaseFirst,
+	49,
+	49,
+	transformIdentity,
+	12,
+	5,
+	transformIdentity,
+	49,
+	0,
+	transformIdentity,
+	1,
+	49,
+	transformOmitFirst4,
+	49,
+	49,
+	transformIdentity,
+	18,
+	49,
+	transformIdentity,
+	17,
+	49,
+	transformIdentity,
+	19,
+	49,
+	transformIdentity,
+	20,
+	49,
+	transformOmitFirst5,
+	49,
+	49,
+	transformOmitFirst6,
+	49,
+	47,
+	transformIdentity,
+	49,
+	49,
+	transformOmitLast4,
+	49,
+	49,
+	transformIdentity,
+	22,
+	49,
+	transformUppercaseAll,
+	49,
+	49,
+	transformIdentity,
+	23,
+	49,
+	transformIdentity,
+	24,
+	49,
+	transformIdentity,
+	25,
+	49,
+	transformOmitLast7,
+	49,
+	49,
+	transformOmitLast1,
+	26,
+	49,
+	transformIdentity,
+	27,
+	49,
+	transformIdentity,
+	28,
+	0,
+	transformIdentity,
+	12,
+	49,
+	transformIdentity,
+	29,
+	49,
+	transformOmitFirst9,
+	49,
+	49,
+	transformOmitFirst7,
+	49,
+	49,
+	transformOmitLast6,
+	49,
+	49,
+	transformIdentity,
+	21,
+	49,
+	transformUppercaseFirst,
+	1,
+	49,
+	transformOmitLast8,
+	49,
+	49,
+	transformIdentity,
+	31,
+	49,
+	transformIdentity,
+	32,
+	47,
+	transformIdentity,
+	3,
+	49,
+	transformOmitLast5,
+	49,
+	49,
+	transformOmitLast9,
+	49,
+	0,
+	transformUppercaseFirst,
+	1,
+	49,
+	transformUppercaseFirst,
+	8,
+	5,
+	transformIdentity,
+	21,
+	49,
+	transformUppercaseAll,
+	0,
+	49,
+	transformUppercaseFirst,
+	10,
+	49,
+	transformIdentity,
+	30,
+	0,
+	transformIdentity,
+	5,
+	35,
+	transformIdentity,
+	49,
+	47,
+	transformIdentity,
+	2,
+	49,
+	transformUppercaseFirst,
+	17,
+	49,
+	transformIdentity,
+	36,
+	49,
+	transformIdentity,
+	33,
+	5,
+	transformIdentity,
+	0,
+	49,
+	transformUppercaseFirst,
+	21,
+	49,
+	transformUppercaseFirst,
+	5,
+	49,
+	transformIdentity,
+	37,
+	0,
+	transformIdentity,
+	30,
+	49,
+	transformIdentity,
+	38,
+	0,
+	transformUppercaseAll,
+	0,
+	49,
+	transformIdentity,
+	39,
+	0,
+	transformUppercaseAll,
+	49,
+	49,
+	transformIdentity,
+	34,
+	49,
+	transformUppercaseAll,
+	8,
+	49,
+	transformUppercaseFirst,
+	12,
+	0,
+	transformIdentity,
+	21,
+	49,
+	transformIdentity,
+	40,
+	0,
+	transformUppercaseFirst,
+	12,
+	49,
+	transformIdentity,
+	41,
+	49,
+	transformIdentity,
+	42,
+	49,
+	transformUppercaseAll,
+	17,
+	49,
+	transformIdentity,
+	43,
+	0,
+	transformUppercaseFirst,
+	5,
+	49,
+	transformUppercaseAll,
+	10,
+	0,
+	transformIdentity,
+	34,
+	49,
+	transformUppercaseFirst,
+	33,
+	49,
+	transformIdentity,
+	44,
+	49,
+	transformUppercaseAll,
+	5,
+	45,
+	transformIdentity,
+	49,
+	0,
+	transformIdentity,
+	33,
+	49,
+	transformUppercaseFirst,
+	30,
+	49,
+	transformUppercaseAll,
+	30,
+	49,
+	transformIdentity,
+	46,
+	49,
+	transformUppercaseAll,
+	1,
+	49,
+	transformUppercaseFirst,
+	34,
+	0,
+	transformUppercaseFirst,
+	33,
+	0,
+	transformUppercaseAll,
+	30,
+	0,
+	transformUppercaseAll,
+	1,
+	49,
+	transformUppercaseAll,
+	33,
+	49,
+	transformUppercaseAll,
+	21,
+	49,
+	transformUppercaseAll,
+	12,
+	0,
+	transformUppercaseAll,
+	5,
+	49,
+	transformUppercaseAll,
+	34,
+	0,
+	transformUppercaseAll,
+	12,
+	0,
+	transformUppercaseFirst,
+	30,
+	0,
+	transformUppercaseAll,
+	34,
+	0,
+	transformUppercaseFirst,
+	34,
+}
+
+var kBrotliTransforms = transforms{
+	217,
+	[]byte(kPrefixSuffix),
+	kPrefixSuffixMap[:],
+	121,
+	kTransformsData,
+	nil, /* no extra parameters */
+	[transformsMaxCutOff + 1]int16{0, 12, 27, 23, 42, 63, 56, 48, 59, 64},
+}
+
+func getTransforms() *transforms {
+	return &kBrotliTransforms
+}
+
+func toUpperCase(p []byte) int {
+	if p[0] < 0xC0 {
+		if p[0] >= 'a' && p[0] <= 'z' {
+			p[0] ^= 32
+		}
+
+		return 1
+	}
+
+	/* An overly simplified uppercasing model for UTF-8. */
+	if p[0] < 0xE0 {
+		p[1] ^= 32
+		return 2
+	}
+
+	/* An arbitrary transform for three byte characters. */
+	p[2] ^= 5
+
+	return 3
+}
+
+func shiftTransform(word []byte, word_len int, parameter uint16) int {
+	/* Limited sign extension: scalar < (1 << 24). */
+	var scalar uint32 = (uint32(parameter) & 0x7FFF) + (0x1000000 - (uint32(parameter) & 0x8000))
+	if word[0] < 0x80 {
+		/* 1-byte rune / 0sssssss / 7 bit scalar (ASCII). */
+		scalar += uint32(word[0])
+
+		word[0] = byte(scalar & 0x7F)
+		return 1
+	} else if word[0] < 0xC0 {
+		/* Continuation / 10AAAAAA. */
+		return 1
+	} else if word[0] < 0xE0 {
+		/* 2-byte rune / 110sssss AAssssss / 11 bit scalar. */
+		if word_len < 2 {
+			return 1
+		}
+		scalar += uint32(word[1]&0x3F | (word[0]&0x1F)<<6)
+		word[0] = byte(0xC0 | (scalar>>6)&0x1F)
+		word[1] = byte(uint32(word[1]&0xC0) | scalar&0x3F)
+		return 2
+	} else if word[0] < 0xF0 {
+		/* 3-byte rune / 1110ssss AAssssss BBssssss / 16 bit scalar. */
+		if word_len < 3 {
+			return word_len
+		}
+		scalar += uint32(word[2])&0x3F | uint32(word[1]&0x3F)<<6 | uint32(word[0]&0x0F)<<12
+		word[0] = byte(0xE0 | (scalar>>12)&0x0F)
+		word[1] = byte(uint32(word[1]&0xC0) | (scalar>>6)&0x3F)
+		word[2] = byte(uint32(word[2]&0xC0) | scalar&0x3F)
+		return 3
+	} else if word[0] < 0xF8 {
+		/* 4-byte rune / 11110sss AAssssss BBssssss CCssssss / 21 bit scalar. */
+		if word_len < 4 {
+			return word_len
+		}
+		scalar += uint32(word[3])&0x3F | uint32(word[2]&0x3F)<<6 | uint32(word[1]&0x3F)<<12 | uint32(word[0]&0x07)<<18
+		word[0] = byte(0xF0 | (scalar>>18)&0x07)
+		word[1] = byte(uint32(word[1]&0xC0) | (scalar>>12)&0x3F)
+		word[2] = byte(uint32(word[2]&0xC0) | (scalar>>6)&0x3F)
+		word[3] = byte(uint32(word[3]&0xC0) | scalar&0x3F)
+		return 4
+	}
+
+	return 1
+}
+
+func transformDictionaryWord(dst []byte, word []byte, len int, trans *transforms, transform_idx int) int {
+	var idx int = 0
+	var prefix []byte = transformPrefix(trans, transform_idx)
+	var type_ byte = transformType(trans, transform_idx)
+	var suffix []byte = transformSuffix(trans, transform_idx)
+	{
+		var prefix_len int = int(prefix[0])
+		prefix = prefix[1:]
+		for {
+			tmp1 := prefix_len
+			prefix_len--
+			if tmp1 == 0 {
+				break
+			}
+			dst[idx] = prefix[0]
+			idx++
+			prefix = prefix[1:]
+		}
+	}
+	{
+		var t int = int(type_)
+		var i int = 0
+		if t <= transformOmitLast9 {
+			len -= t
+		} else if t >= transformOmitFirst1 && t <= transformOmitFirst9 {
+			var skip int = t - (transformOmitFirst1 - 1)
+			word = word[skip:]
+			len -= skip
+		}
+
+		for i < len {
+			dst[idx] = word[i]
+			idx++
+			i++
+		}
+		if t == transformUppercaseFirst {
+			toUpperCase(dst[idx-len:])
+		} else if t == transformUppercaseAll {
+			var uppercase []byte = dst
+			uppercase = uppercase[idx-len:]
+			for len > 0 {
+				var step int = toUpperCase(uppercase)
+				uppercase = uppercase[step:]
+				len -= step
+			}
+		} else if t == transformShiftFirst {
+			var param uint16 = uint16(trans.params[transform_idx*2]) + uint16(trans.params[transform_idx*2+1])<<8
+			shiftTransform(dst[idx-len:], int(len), param)
+		} else if t == transformShiftAll {
+			var param uint16 = uint16(trans.params[transform_idx*2]) + uint16(trans.params[transform_idx*2+1])<<8
+			var shift []byte = dst
+			shift = shift[idx-len:]
+			for len > 0 {
+				var step int = shiftTransform(shift, int(len), param)
+				shift = shift[step:]
+				len -= step
+			}
+		}
+	}
+	{
+		var suffix_len int = int(suffix[0])
+		suffix = suffix[1:]
+		for {
+			tmp2 := suffix_len
+			suffix_len--
+			if tmp2 == 0 {
+				break
+			}
+			dst[idx] = suffix[0]
+			idx++
+			suffix = suffix[1:]
+		}
+		return idx
+	}
+}

vendor/github.com/andybalholm/brotli/utf8_util.go

@@ -0,0 +1,70 @@
+package brotli
+
+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Heuristics for deciding about the UTF8-ness of strings. */
+
+const kMinUTF8Ratio float64 = 0.75
+
+/* Returns 1 if at least min_fraction of the bytes between pos and
+   pos + length in the (data, mask) ring-buffer is UTF8-encoded, otherwise
+   returns 0. */
+func parseAsUTF8(symbol *int, input []byte, size uint) uint {
+	/* ASCII */
+	if input[0]&0x80 == 0 {
+		*symbol = int(input[0])
+		if *symbol > 0 {
+			return 1
+		}
+	}
+
+	/* 2-byte UTF8 */
+	if size > 1 && input[0]&0xE0 == 0xC0 && input[1]&0xC0 == 0x80 {
+		*symbol = (int(input[0])&0x1F)<<6 | int(input[1])&0x3F
+		if *symbol > 0x7F {
+			return 2
+		}
+	}
+
+	/* 3-byte UFT8 */
+	if size > 2 && input[0]&0xF0 == 0xE0 && input[1]&0xC0 == 0x80 && input[2]&0xC0 == 0x80 {
+		*symbol = (int(input[0])&0x0F)<<12 | (int(input[1])&0x3F)<<6 | int(input[2])&0x3F
+		if *symbol > 0x7FF {
+			return 3
+		}
+	}
+
+	/* 4-byte UFT8 */
+	if size > 3 && input[0]&0xF8 == 0xF0 && input[1]&0xC0 == 0x80 && input[2]&0xC0 == 0x80 && input[3]&0xC0 == 0x80 {
+		*symbol = (int(input[0])&0x07)<<18 | (int(input[1])&0x3F)<<12 | (int(input[2])&0x3F)<<6 | int(input[3])&0x3F
+		if *symbol > 0xFFFF && *symbol <= 0x10FFFF {
+			return 4
+		}
+	}
+
+	/* Not UTF8, emit a special symbol above the UTF8-code space */
+	*symbol = 0x110000 | int(input[0])
+
+	return 1
+}
+
+/* Returns 1 if at least min_fraction of the data is UTF8-encoded.*/
+func isMostlyUTF8(data []byte, pos uint, mask uint, length uint, min_fraction float64) bool {
+	var size_utf8 uint = 0
+	var i uint = 0
+	for i < length {
+		var symbol int
+		current_data := data[(pos+i)&mask:]
+		var bytes_read uint = parseAsUTF8(&symbol, current_data, length-i)
+		i += bytes_read
+		if symbol < 0x110000 {
+			size_utf8 += bytes_read
+		}
+	}
+
+	return float64(size_utf8) > min_fraction*float64(length)
+}

vendor/github.com/andybalholm/brotli/util.go

@@ -0,0 +1,7 @@
+package brotli
+
+func assert(cond bool) {
+	if !cond {
+		panic("assertion failure")
+	}
+}

vendor/github.com/andybalholm/brotli/write_bits.go

@@ -0,0 +1,52 @@
+package brotli
+
+import "encoding/binary"
+
+/* Copyright 2010 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Write bits into a byte array. */
+
+/* This function writes bits into bytes in increasing addresses, and within
+   a byte least-significant-bit first.
+
+   The function can write up to 56 bits in one go with WriteBits
+   Example: let's assume that 3 bits (Rs below) have been written already:
+
+   BYTE-0     BYTE+1       BYTE+2
+
+   0000 0RRR    0000 0000    0000 0000
+
+   Now, we could write 5 or less bits in MSB by just sifting by 3
+   and OR'ing to BYTE-0.
+
+   For n bits, we take the last 5 bits, OR that with high bits in BYTE-0,
+   and locate the rest in BYTE+1, BYTE+2, etc. */
+func writeBits(n_bits uint, bits uint64, pos *uint, array []byte) {
+	/* This branch of the code can write up to 56 bits at a time,
+	   7 bits are lost by being perhaps already in *p and at least
+	   1 bit is needed to initialize the bit-stream ahead (i.e. if 7
+	   bits are in *p and we write 57 bits, then the next write will
+	   access a byte that was never initialized). */
+	p := array[*pos>>3:]
+	v := uint64(p[0])
+	v |= bits << (*pos & 7)
+	binary.LittleEndian.PutUint64(p, v)
+	*pos += n_bits
+}
+
+func writeSingleBit(bit bool, pos *uint, array []byte) {
+	if bit {
+		writeBits(1, 1, pos, array)
+	} else {
+		writeBits(1, 0, pos, array)
+	}
+}
+
+func writeBitsPrepareStorage(pos uint, array []byte) {
+	assert(pos&7 == 0)
+	array[pos>>3] = 0
+}

vendor/github.com/andybalholm/brotli/writer.go

@@ -0,0 +1,119 @@
+package brotli
+
+import (
+	"errors"
+	"io"
+)
+
+const (
+	BestSpeed          = 0
+	BestCompression    = 11
+	DefaultCompression = 6
+)
+
+// WriterOptions configures Writer.
+type WriterOptions struct {
+	// Quality controls the compression-speed vs compression-density trade-offs.
+	// The higher the quality, the slower the compression. Range is 0 to 11.
+	Quality int
+	// LGWin is the base 2 logarithm of the sliding window size.
+	// Range is 10 to 24. 0 indicates automatic configuration based on Quality.
+	LGWin int
+}
+
+var (
+	errEncode       = errors.New("brotli: encode error")
+	errWriterClosed = errors.New("brotli: Writer is closed")
+)
+
+// Writes to the returned writer are compressed and written to dst.
+// It is the caller's responsibility to call Close on the Writer when done.
+// Writes may be buffered and not flushed until Close.
+func NewWriter(dst io.Writer) *Writer {
+	return NewWriterLevel(dst, DefaultCompression)
+}
+
+// NewWriterLevel is like NewWriter but specifies the compression level instead
+// of assuming DefaultCompression.
+// The compression level can be DefaultCompression or any integer value between
+// BestSpeed and BestCompression inclusive.
+func NewWriterLevel(dst io.Writer, level int) *Writer {
+	return NewWriterOptions(dst, WriterOptions{
+		Quality: level,
+	})
+}
+
+// NewWriterOptions is like NewWriter but specifies WriterOptions
+func NewWriterOptions(dst io.Writer, options WriterOptions) *Writer {
+	w := new(Writer)
+	w.options = options
+	w.Reset(dst)
+	return w
+}
+
+// Reset discards the Writer's state and makes it equivalent to the result of
+// its original state from NewWriter or NewWriterLevel, but writing to dst
+// instead. This permits reusing a Writer rather than allocating a new one.
+func (w *Writer) Reset(dst io.Writer) {
+	encoderInitState(w)
+	w.params.quality = w.options.Quality
+	if w.options.LGWin > 0 {
+		w.params.lgwin = uint(w.options.LGWin)
+	}
+	w.dst = dst
+	w.err = nil
+}
+
+func (w *Writer) writeChunk(p []byte, op int) (n int, err error) {
+	if w.dst == nil {
+		return 0, errWriterClosed
+	}
+	if w.err != nil {
+		return 0, w.err
+	}
+
+	for {
+		availableIn := uint(len(p))
+		nextIn := p
+		success := encoderCompressStream(w, op, &availableIn, &nextIn)
+		bytesConsumed := len(p) - int(availableIn)
+		p = p[bytesConsumed:]
+		n += bytesConsumed
+		if !success {
+			return n, errEncode
+		}
+
+		if len(p) == 0 || w.err != nil {
+			return n, w.err
+		}
+	}
+}
+
+// Flush outputs encoded data for all input provided to Write. The resulting
+// output can be decoded to match all input before Flush, but the stream is
+// not yet complete until after Close.
+// Flush has a negative impact on compression.
+func (w *Writer) Flush() error {
+	_, err := w.writeChunk(nil, operationFlush)
+	return err
+}
+
+// Close flushes remaining data to the decorated writer.
+func (w *Writer) Close() error {
+	// If stream is already closed, it is reported by `writeChunk`.
+	_, err := w.writeChunk(nil, operationFinish)
+	w.dst = nil
+	return err
+}
+
+// Write implements io.Writer. Flush or Close must be called to ensure that the
+// encoded bytes are actually flushed to the underlying Writer.
+func (w *Writer) Write(p []byte) (n int, err error) {
+	return w.writeChunk(p, operationProcess)
+}
+
+type nopCloser struct {
+	io.Writer
+}
+
+func (nopCloser) Close() error { return nil }

vendor/modules.txt

@@ -113,6 +113,9 @@ github.com/anacrolix/upnp
 # github.com/anacrolix/utp v0.1.0
 ## explicit
 github.com/anacrolix/utp
+# github.com/andybalholm/brotli v1.0.5
+## explicit; go 1.12
+github.com/andybalholm/brotli
 # github.com/andybalholm/cascadia v1.2.0
 ## explicit; go 1.13
 github.com/andybalholm/cascadia