303 lines
8.1 KiB
Go
303 lines
8.1 KiB
Go
// Package multihash is the Go implementation of
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// https://github.com/multiformats/multihash, or self-describing
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// hashes.
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package multihash
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import (
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"encoding/hex"
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"errors"
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"fmt"
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"math"
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b58 "github.com/mr-tron/base58/base58"
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"github.com/multiformats/go-varint"
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)
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// errors
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var (
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ErrUnknownCode = errors.New("unknown multihash code")
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ErrTooShort = errors.New("multihash too short. must be >= 2 bytes")
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ErrTooLong = errors.New("multihash too long. must be < 129 bytes")
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ErrLenNotSupported = errors.New("multihash does not yet support digests longer than 127 bytes")
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ErrInvalidMultihash = errors.New("input isn't valid multihash")
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ErrVarintBufferShort = errors.New("uvarint: buffer too small")
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ErrVarintTooLong = errors.New("uvarint: varint too big (max 64bit)")
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)
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// ErrInconsistentLen is returned when a decoded multihash has an inconsistent length
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type ErrInconsistentLen struct {
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dm *DecodedMultihash
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}
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func (e ErrInconsistentLen) Error() string {
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return fmt.Sprintf("multihash length inconsistent: expected %d, got %d", e.dm.Length, len(e.dm.Digest))
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}
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// constants
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const (
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IDENTITY = 0x00
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// Deprecated: use IDENTITY
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ID = IDENTITY
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SHA1 = 0x11
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SHA2_256 = 0x12
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SHA2_512 = 0x13
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SHA3_224 = 0x17
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SHA3_256 = 0x16
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SHA3_384 = 0x15
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SHA3_512 = 0x14
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SHA3 = SHA3_512
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KECCAK_224 = 0x1A
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KECCAK_256 = 0x1B
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KECCAK_384 = 0x1C
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KECCAK_512 = 0x1D
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SHAKE_128 = 0x18
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SHAKE_256 = 0x19
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BLAKE2B_MIN = 0xb201
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BLAKE2B_MAX = 0xb240
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BLAKE2S_MIN = 0xb241
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BLAKE2S_MAX = 0xb260
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MD5 = 0xd5
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DBL_SHA2_256 = 0x56
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MURMUR3_128 = 0x22
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// Deprecated: use MURMUR3_128
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MURMUR3 = MURMUR3_128
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SHA2_256_TRUNC254_PADDED = 0x1012
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X11 = 0x1100
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POSEIDON_BLS12_381_A1_FC1 = 0xb401
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)
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func init() {
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// Add blake2b (64 codes)
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for c := uint64(BLAKE2B_MIN); c <= BLAKE2B_MAX; c++ {
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n := c - BLAKE2B_MIN + 1
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name := fmt.Sprintf("blake2b-%d", n*8)
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Names[name] = c
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Codes[c] = name
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}
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// Add blake2s (32 codes)
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for c := uint64(BLAKE2S_MIN); c <= BLAKE2S_MAX; c++ {
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n := c - BLAKE2S_MIN + 1
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name := fmt.Sprintf("blake2s-%d", n*8)
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Names[name] = c
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Codes[c] = name
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}
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}
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// Names maps the name of a hash to the code
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var Names = map[string]uint64{
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"identity": IDENTITY,
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"sha1": SHA1,
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"sha2-256": SHA2_256,
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"sha2-512": SHA2_512,
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"sha3": SHA3_512,
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"sha3-224": SHA3_224,
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"sha3-256": SHA3_256,
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"sha3-384": SHA3_384,
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"sha3-512": SHA3_512,
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"dbl-sha2-256": DBL_SHA2_256,
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"murmur3-128": MURMUR3_128,
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"keccak-224": KECCAK_224,
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"keccak-256": KECCAK_256,
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"keccak-384": KECCAK_384,
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"keccak-512": KECCAK_512,
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"shake-128": SHAKE_128,
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"shake-256": SHAKE_256,
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"sha2-256-trunc254-padded": SHA2_256_TRUNC254_PADDED,
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"x11": X11,
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"md5": MD5,
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"poseidon-bls12_381-a2-fc1": POSEIDON_BLS12_381_A1_FC1,
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}
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// Codes maps a hash code to it's name
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var Codes = map[uint64]string{
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IDENTITY: "identity",
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SHA1: "sha1",
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SHA2_256: "sha2-256",
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SHA2_512: "sha2-512",
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SHA3_224: "sha3-224",
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SHA3_256: "sha3-256",
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SHA3_384: "sha3-384",
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SHA3_512: "sha3-512",
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DBL_SHA2_256: "dbl-sha2-256",
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MURMUR3_128: "murmur3-128",
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KECCAK_224: "keccak-224",
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KECCAK_256: "keccak-256",
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KECCAK_384: "keccak-384",
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KECCAK_512: "keccak-512",
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SHAKE_128: "shake-128",
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SHAKE_256: "shake-256",
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SHA2_256_TRUNC254_PADDED: "sha2-256-trunc254-padded",
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X11: "x11",
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POSEIDON_BLS12_381_A1_FC1: "poseidon-bls12_381-a2-fc1",
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MD5: "md5",
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}
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func uvarint(buf []byte) (uint64, []byte, error) {
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n, c, err := varint.FromUvarint(buf)
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if err != nil {
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return n, buf, err
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}
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if c == 0 {
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return n, buf, ErrVarintBufferShort
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} else if c < 0 {
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return n, buf[-c:], ErrVarintTooLong
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} else {
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return n, buf[c:], nil
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}
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}
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// DecodedMultihash represents a parsed multihash and allows
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// easy access to the different parts of a multihash.
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type DecodedMultihash struct {
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Code uint64
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Name string
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Length int // Length is just int as it is type of len() opearator
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Digest []byte // Digest holds the raw multihash bytes
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}
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// Multihash is byte slice with the following form:
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// <hash function code><digest size><hash function output>.
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// See the spec for more information.
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type Multihash []byte
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// HexString returns the hex-encoded representation of a multihash.
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func (m *Multihash) HexString() string {
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return hex.EncodeToString([]byte(*m))
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}
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// String is an alias to HexString().
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func (m *Multihash) String() string {
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return m.HexString()
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}
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// FromHexString parses a hex-encoded multihash.
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func FromHexString(s string) (Multihash, error) {
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b, err := hex.DecodeString(s)
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if err != nil {
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return Multihash{}, err
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}
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return Cast(b)
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}
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// B58String returns the B58-encoded representation of a multihash.
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func (m Multihash) B58String() string {
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return b58.Encode([]byte(m))
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}
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// FromB58String parses a B58-encoded multihash.
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func FromB58String(s string) (m Multihash, err error) {
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b, err := b58.Decode(s)
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if err != nil {
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return Multihash{}, ErrInvalidMultihash
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}
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return Cast(b)
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}
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// Cast casts a buffer onto a multihash, and returns an error
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// if it does not work.
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func Cast(buf []byte) (Multihash, error) {
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_, err := Decode(buf)
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if err != nil {
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return Multihash{}, err
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}
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return Multihash(buf), nil
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}
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// Decode parses multihash bytes into a DecodedMultihash.
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func Decode(buf []byte) (*DecodedMultihash, error) {
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rlen, code, hdig, err := readMultihashFromBuf(buf)
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if err != nil {
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return nil, err
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}
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dm := &DecodedMultihash{
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Code: code,
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Name: Codes[code],
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Length: len(hdig),
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Digest: hdig,
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}
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if len(buf) != rlen {
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return nil, ErrInconsistentLen{dm}
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}
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return dm, nil
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}
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// Encode a hash digest along with the specified function code.
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// Note: the length is derived from the length of the digest itself.
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//
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// The error return is legacy; it is always nil.
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func Encode(buf []byte, code uint64) ([]byte, error) {
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// FUTURE: this function always causes heap allocs... but when used, this value is almost always going to be appended to another buffer (either as part of CID creation, or etc) -- should this whole function be rethought and alternatives offered?
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newBuf := make([]byte, varint.UvarintSize(code)+varint.UvarintSize(uint64(len(buf)))+len(buf))
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n := varint.PutUvarint(newBuf, code)
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n += varint.PutUvarint(newBuf[n:], uint64(len(buf)))
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copy(newBuf[n:], buf)
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return newBuf, nil
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}
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// EncodeName is like Encode() but providing a string name
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// instead of a numeric code. See Names for allowed values.
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func EncodeName(buf []byte, name string) ([]byte, error) {
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return Encode(buf, Names[name])
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}
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// readMultihashFromBuf reads a multihash from the given buffer, returning the
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// individual pieces of the multihash.
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// Note: the returned digest is a slice over the passed in data and should be
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// copied if the buffer will be reused
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func readMultihashFromBuf(buf []byte) (int, uint64, []byte, error) {
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bufl := len(buf)
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if bufl < 2 {
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return 0, 0, nil, ErrTooShort
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}
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var err error
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var code, length uint64
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code, buf, err = uvarint(buf)
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if err != nil {
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return 0, 0, nil, err
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}
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length, buf, err = uvarint(buf)
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if err != nil {
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return 0, 0, nil, err
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}
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if length > math.MaxInt32 {
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return 0, 0, nil, errors.New("digest too long, supporting only <= 2^31-1")
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}
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if int(length) > len(buf) {
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return 0, 0, nil, errors.New("length greater than remaining number of bytes in buffer")
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}
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rlen := (bufl - len(buf)) + int(length)
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return rlen, code, buf[:length], nil
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}
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// MHFromBytes reads a multihash from the given byte buffer, returning the
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// number of bytes read as well as the multihash
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func MHFromBytes(buf []byte) (int, Multihash, error) {
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nr, _, _, err := readMultihashFromBuf(buf)
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if err != nil {
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return 0, nil, err
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}
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return nr, Multihash(buf[:nr]), nil
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}
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