763 lines
20 KiB
Go
763 lines
20 KiB
Go
// Copyright 2011 The Snappy-Go Authors. All rights reserved.
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// Copyright (c) 2019 Klaus Post. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package s2
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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"io/ioutil"
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)
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var (
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// ErrCorrupt reports that the input is invalid.
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ErrCorrupt = errors.New("s2: corrupt input")
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// ErrCRC reports that the input failed CRC validation (streams only)
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ErrCRC = errors.New("s2: corrupt input, crc mismatch")
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// ErrTooLarge reports that the uncompressed length is too large.
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ErrTooLarge = errors.New("s2: decoded block is too large")
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// ErrUnsupported reports that the input isn't supported.
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ErrUnsupported = errors.New("s2: unsupported input")
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)
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// ErrCantSeek is returned if the stream cannot be seeked.
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type ErrCantSeek struct {
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Reason string
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}
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// Error returns the error as string.
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func (e ErrCantSeek) Error() string {
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return fmt.Sprintf("s2: Can't seek because %s", e.Reason)
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}
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// DecodedLen returns the length of the decoded block.
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func DecodedLen(src []byte) (int, error) {
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v, _, err := decodedLen(src)
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return v, err
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}
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// decodedLen returns the length of the decoded block and the number of bytes
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// that the length header occupied.
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func decodedLen(src []byte) (blockLen, headerLen int, err error) {
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v, n := binary.Uvarint(src)
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if n <= 0 || v > 0xffffffff {
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return 0, 0, ErrCorrupt
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}
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const wordSize = 32 << (^uint(0) >> 32 & 1)
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if wordSize == 32 && v > 0x7fffffff {
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return 0, 0, ErrTooLarge
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}
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return int(v), n, nil
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}
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const (
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decodeErrCodeCorrupt = 1
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)
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// Decode returns the decoded form of src. The returned slice may be a sub-
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// slice of dst if dst was large enough to hold the entire decoded block.
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// Otherwise, a newly allocated slice will be returned.
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//
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// The dst and src must not overlap. It is valid to pass a nil dst.
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func Decode(dst, src []byte) ([]byte, error) {
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dLen, s, err := decodedLen(src)
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if err != nil {
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return nil, err
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}
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if dLen <= cap(dst) {
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dst = dst[:dLen]
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} else {
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dst = make([]byte, dLen)
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}
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if s2Decode(dst, src[s:]) != 0 {
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return nil, ErrCorrupt
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}
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return dst, nil
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}
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// NewReader returns a new Reader that decompresses from r, using the framing
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// format described at
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// https://github.com/google/snappy/blob/master/framing_format.txt with S2 changes.
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func NewReader(r io.Reader, opts ...ReaderOption) *Reader {
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nr := Reader{
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r: r,
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maxBlock: maxBlockSize,
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}
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for _, opt := range opts {
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if err := opt(&nr); err != nil {
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nr.err = err
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return &nr
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}
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}
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nr.maxBufSize = MaxEncodedLen(nr.maxBlock) + checksumSize
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if nr.lazyBuf > 0 {
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nr.buf = make([]byte, MaxEncodedLen(nr.lazyBuf)+checksumSize)
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} else {
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nr.buf = make([]byte, MaxEncodedLen(defaultBlockSize)+checksumSize)
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}
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nr.readHeader = nr.ignoreStreamID
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nr.paramsOK = true
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return &nr
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}
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// ReaderOption is an option for creating a decoder.
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type ReaderOption func(*Reader) error
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// ReaderMaxBlockSize allows to control allocations if the stream
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// has been compressed with a smaller WriterBlockSize, or with the default 1MB.
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// Blocks must be this size or smaller to decompress,
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// otherwise the decoder will return ErrUnsupported.
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//
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// For streams compressed with Snappy this can safely be set to 64KB (64 << 10).
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//
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// Default is the maximum limit of 4MB.
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func ReaderMaxBlockSize(blockSize int) ReaderOption {
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return func(r *Reader) error {
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if blockSize > maxBlockSize || blockSize <= 0 {
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return errors.New("s2: block size too large. Must be <= 4MB and > 0")
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}
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if r.lazyBuf == 0 && blockSize < defaultBlockSize {
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r.lazyBuf = blockSize
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}
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r.maxBlock = blockSize
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return nil
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}
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}
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// ReaderAllocBlock allows to control upfront stream allocations
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// and not allocate for frames bigger than this initially.
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// If frames bigger than this is seen a bigger buffer will be allocated.
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//
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// Default is 1MB, which is default output size.
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func ReaderAllocBlock(blockSize int) ReaderOption {
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return func(r *Reader) error {
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if blockSize > maxBlockSize || blockSize < 1024 {
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return errors.New("s2: invalid ReaderAllocBlock. Must be <= 4MB and >= 1024")
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}
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r.lazyBuf = blockSize
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return nil
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}
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}
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// ReaderIgnoreStreamIdentifier will make the reader skip the expected
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// stream identifier at the beginning of the stream.
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// This can be used when serving a stream that has been forwarded to a specific point.
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func ReaderIgnoreStreamIdentifier() ReaderOption {
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return func(r *Reader) error {
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r.ignoreStreamID = true
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return nil
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}
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}
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// ReaderSkippableCB will register a callback for chuncks with the specified ID.
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// ID must be a Reserved skippable chunks ID, 0x80-0xfd (inclusive).
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// For each chunk with the ID, the callback is called with the content.
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// Any returned non-nil error will abort decompression.
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// Only one callback per ID is supported, latest sent will be used.
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func ReaderSkippableCB(id uint8, fn func(r io.Reader) error) ReaderOption {
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return func(r *Reader) error {
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if id < 0x80 || id > 0xfd {
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return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfd (inclusive)")
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}
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r.skippableCB[id] = fn
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return nil
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}
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}
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// Reader is an io.Reader that can read Snappy-compressed bytes.
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type Reader struct {
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r io.Reader
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err error
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decoded []byte
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buf []byte
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skippableCB [0x80]func(r io.Reader) error
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blockStart int64 // Uncompressed offset at start of current.
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index *Index
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// decoded[i:j] contains decoded bytes that have not yet been passed on.
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i, j int
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// maximum block size allowed.
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maxBlock int
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// maximum expected buffer size.
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maxBufSize int
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// alloc a buffer this size if > 0.
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lazyBuf int
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readHeader bool
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paramsOK bool
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snappyFrame bool
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ignoreStreamID bool
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}
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// ensureBufferSize will ensure that the buffer can take at least n bytes.
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// If false is returned the buffer exceeds maximum allowed size.
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func (r *Reader) ensureBufferSize(n int) bool {
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if len(r.buf) >= n {
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return true
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}
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if n > r.maxBufSize {
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r.err = ErrCorrupt
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return false
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}
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// Realloc buffer.
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r.buf = make([]byte, n)
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return true
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}
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// Reset discards any buffered data, resets all state, and switches the Snappy
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// reader to read from r. This permits reusing a Reader rather than allocating
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// a new one.
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func (r *Reader) Reset(reader io.Reader) {
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if !r.paramsOK {
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return
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}
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r.index = nil
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r.r = reader
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r.err = nil
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r.i = 0
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r.j = 0
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r.readHeader = r.ignoreStreamID
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}
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func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
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if _, r.err = io.ReadFull(r.r, p); r.err != nil {
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if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
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r.err = ErrCorrupt
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}
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return false
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}
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return true
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}
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// skippable will skip n bytes.
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// If the supplied reader supports seeking that is used.
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// tmp is used as a temporary buffer for reading.
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// The supplied slice does not need to be the size of the read.
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func (r *Reader) skippable(tmp []byte, n int, allowEOF bool, id uint8) (ok bool) {
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if id < 0x80 {
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r.err = fmt.Errorf("interbal error: skippable id < 0x80")
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return false
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}
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if fn := r.skippableCB[id-0x80]; fn != nil {
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rd := io.LimitReader(r.r, int64(n))
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r.err = fn(rd)
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if r.err != nil {
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return false
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}
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_, r.err = io.CopyBuffer(ioutil.Discard, rd, tmp)
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return r.err == nil
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}
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if rs, ok := r.r.(io.ReadSeeker); ok {
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_, err := rs.Seek(int64(n), io.SeekCurrent)
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if err == nil {
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return true
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}
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if err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
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r.err = ErrCorrupt
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return false
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}
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}
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for n > 0 {
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if n < len(tmp) {
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tmp = tmp[:n]
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}
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if _, r.err = io.ReadFull(r.r, tmp); r.err != nil {
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if r.err == io.ErrUnexpectedEOF || (r.err == io.EOF && !allowEOF) {
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r.err = ErrCorrupt
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}
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return false
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}
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n -= len(tmp)
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}
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return true
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}
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// Read satisfies the io.Reader interface.
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func (r *Reader) Read(p []byte) (int, error) {
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if r.err != nil {
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return 0, r.err
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}
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for {
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if r.i < r.j {
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n := copy(p, r.decoded[r.i:r.j])
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r.i += n
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return n, nil
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}
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if !r.readFull(r.buf[:4], true) {
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return 0, r.err
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}
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chunkType := r.buf[0]
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if !r.readHeader {
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if chunkType != chunkTypeStreamIdentifier {
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r.err = ErrCorrupt
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return 0, r.err
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}
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r.readHeader = true
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}
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chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
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// The chunk types are specified at
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// https://github.com/google/snappy/blob/master/framing_format.txt
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switch chunkType {
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case chunkTypeCompressedData:
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r.blockStart += int64(r.j)
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// Section 4.2. Compressed data (chunk type 0x00).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err == nil {
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r.err = ErrUnsupported
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}
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return 0, r.err
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}
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buf := r.buf[:chunkLen]
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if !r.readFull(buf, false) {
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return 0, r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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buf = buf[checksumSize:]
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n, err := DecodedLen(buf)
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if err != nil {
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r.err = err
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return 0, r.err
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}
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if r.snappyFrame && n > maxSnappyBlockSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if n > len(r.decoded) {
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if n > r.maxBlock {
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r.err = ErrCorrupt
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return 0, r.err
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}
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r.decoded = make([]byte, n)
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}
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if _, err := Decode(r.decoded, buf); err != nil {
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r.err = err
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return 0, r.err
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}
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if crc(r.decoded[:n]) != checksum {
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r.err = ErrCRC
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return 0, r.err
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}
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r.i, r.j = 0, n
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continue
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case chunkTypeUncompressedData:
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r.blockStart += int64(r.j)
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// Section 4.3. Uncompressed data (chunk type 0x01).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err == nil {
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r.err = ErrUnsupported
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}
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return 0, r.err
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}
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buf := r.buf[:checksumSize]
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if !r.readFull(buf, false) {
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return 0, r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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// Read directly into r.decoded instead of via r.buf.
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n := chunkLen - checksumSize
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if r.snappyFrame && n > maxSnappyBlockSize {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if n > len(r.decoded) {
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if n > r.maxBlock {
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r.err = ErrCorrupt
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return 0, r.err
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}
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r.decoded = make([]byte, n)
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}
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if !r.readFull(r.decoded[:n], false) {
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return 0, r.err
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}
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if crc(r.decoded[:n]) != checksum {
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r.err = ErrCRC
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return 0, r.err
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}
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r.i, r.j = 0, n
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continue
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case chunkTypeStreamIdentifier:
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// Section 4.1. Stream identifier (chunk type 0xff).
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if chunkLen != len(magicBody) {
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r.err = ErrCorrupt
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return 0, r.err
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}
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if !r.readFull(r.buf[:len(magicBody)], false) {
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return 0, r.err
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}
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if string(r.buf[:len(magicBody)]) != magicBody {
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if string(r.buf[:len(magicBody)]) != magicBodySnappy {
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r.err = ErrCorrupt
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return 0, r.err
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} else {
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r.snappyFrame = true
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}
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} else {
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r.snappyFrame = false
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}
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continue
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}
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if chunkType <= 0x7f {
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// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
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// fmt.Printf("ERR chunktype: 0x%x\n", chunkType)
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r.err = ErrUnsupported
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return 0, r.err
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}
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// Section 4.4 Padding (chunk type 0xfe).
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// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
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if chunkLen > maxChunkSize {
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// fmt.Printf("ERR chunkLen: 0x%x\n", chunkLen)
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r.err = ErrUnsupported
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return 0, r.err
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}
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// fmt.Printf("skippable: ID: 0x%x, len: 0x%x\n", chunkType, chunkLen)
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if !r.skippable(r.buf, chunkLen, false, chunkType) {
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return 0, r.err
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}
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}
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}
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// Skip will skip n bytes forward in the decompressed output.
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// For larger skips this consumes less CPU and is faster than reading output and discarding it.
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// CRC is not checked on skipped blocks.
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// io.ErrUnexpectedEOF is returned if the stream ends before all bytes have been skipped.
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// If a decoding error is encountered subsequent calls to Read will also fail.
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func (r *Reader) Skip(n int64) error {
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if n < 0 {
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return errors.New("attempted negative skip")
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}
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if r.err != nil {
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return r.err
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}
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for n > 0 {
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if r.i < r.j {
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// Skip in buffer.
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// decoded[i:j] contains decoded bytes that have not yet been passed on.
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left := int64(r.j - r.i)
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if left >= n {
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r.i += int(n)
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return nil
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}
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n -= int64(r.j - r.i)
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r.i = r.j
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}
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// Buffer empty; read blocks until we have content.
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if !r.readFull(r.buf[:4], true) {
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if r.err == io.EOF {
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r.err = io.ErrUnexpectedEOF
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}
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return r.err
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}
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chunkType := r.buf[0]
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if !r.readHeader {
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if chunkType != chunkTypeStreamIdentifier {
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r.err = ErrCorrupt
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return r.err
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}
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r.readHeader = true
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}
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chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
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// The chunk types are specified at
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// https://github.com/google/snappy/blob/master/framing_format.txt
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switch chunkType {
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case chunkTypeCompressedData:
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r.blockStart += int64(r.j)
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// Section 4.2. Compressed data (chunk type 0x00).
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if chunkLen < checksumSize {
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r.err = ErrCorrupt
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return r.err
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}
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if !r.ensureBufferSize(chunkLen) {
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if r.err == nil {
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r.err = ErrUnsupported
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}
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return r.err
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}
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buf := r.buf[:chunkLen]
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if !r.readFull(buf, false) {
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return r.err
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}
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checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
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buf = buf[checksumSize:]
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dLen, err := DecodedLen(buf)
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if err != nil {
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r.err = err
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return r.err
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}
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if dLen > r.maxBlock {
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r.err = ErrCorrupt
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return r.err
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}
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// Check if destination is within this block
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if int64(dLen) > n {
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if len(r.decoded) < dLen {
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r.decoded = make([]byte, dLen)
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}
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if _, err := Decode(r.decoded, buf); err != nil {
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r.err = err
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return r.err
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}
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if crc(r.decoded[:dLen]) != checksum {
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r.err = ErrCorrupt
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return r.err
|
|
}
|
|
} else {
|
|
// Skip block completely
|
|
n -= int64(dLen)
|
|
dLen = 0
|
|
}
|
|
r.i, r.j = 0, dLen
|
|
continue
|
|
case chunkTypeUncompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.3. Uncompressed data (chunk type 0x01).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
if !r.ensureBufferSize(chunkLen) {
|
|
if r.err != nil {
|
|
r.err = ErrUnsupported
|
|
}
|
|
return r.err
|
|
}
|
|
buf := r.buf[:checksumSize]
|
|
if !r.readFull(buf, false) {
|
|
return r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
// Read directly into r.decoded instead of via r.buf.
|
|
n2 := chunkLen - checksumSize
|
|
if n2 > len(r.decoded) {
|
|
if n2 > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
r.decoded = make([]byte, n2)
|
|
}
|
|
if !r.readFull(r.decoded[:n2], false) {
|
|
return r.err
|
|
}
|
|
if int64(n2) < n {
|
|
if crc(r.decoded[:n2]) != checksum {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
}
|
|
r.i, r.j = 0, n2
|
|
continue
|
|
case chunkTypeStreamIdentifier:
|
|
// Section 4.1. Stream identifier (chunk type 0xff).
|
|
if chunkLen != len(magicBody) {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
if !r.readFull(r.buf[:len(magicBody)], false) {
|
|
return r.err
|
|
}
|
|
if string(r.buf[:len(magicBody)]) != magicBody {
|
|
if string(r.buf[:len(magicBody)]) != magicBodySnappy {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
}
|
|
|
|
continue
|
|
}
|
|
|
|
if chunkType <= 0x7f {
|
|
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
|
|
r.err = ErrUnsupported
|
|
return r.err
|
|
}
|
|
if chunkLen > maxChunkSize {
|
|
r.err = ErrUnsupported
|
|
return r.err
|
|
}
|
|
// Section 4.4 Padding (chunk type 0xfe).
|
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
|
if !r.skippable(r.buf, chunkLen, false, chunkType) {
|
|
return r.err
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// ReadSeeker provides random or forward seeking in compressed content.
|
|
// See Reader.ReadSeeker
|
|
type ReadSeeker struct {
|
|
*Reader
|
|
}
|
|
|
|
// ReadSeeker will return an io.ReadSeeker compatible version of the reader.
|
|
// If 'random' is specified the returned io.Seeker can be used for
|
|
// random seeking, otherwise only forward seeking is supported.
|
|
// Enabling random seeking requires the original input to support
|
|
// the io.Seeker interface.
|
|
// A custom index can be specified which will be used if supplied.
|
|
// When using a custom index, it will not be read from the input stream.
|
|
// The returned ReadSeeker contains a shallow reference to the existing Reader,
|
|
// meaning changes performed to one is reflected in the other.
|
|
func (r *Reader) ReadSeeker(random bool, index []byte) (*ReadSeeker, error) {
|
|
// Read index if provided.
|
|
if len(index) != 0 {
|
|
if r.index == nil {
|
|
r.index = &Index{}
|
|
}
|
|
if _, err := r.index.Load(index); err != nil {
|
|
return nil, ErrCantSeek{Reason: "loading index returned: " + err.Error()}
|
|
}
|
|
}
|
|
|
|
// Check if input is seekable
|
|
rs, ok := r.r.(io.ReadSeeker)
|
|
if !ok {
|
|
if !random {
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
return nil, ErrCantSeek{Reason: "input stream isn't seekable"}
|
|
}
|
|
|
|
if r.index != nil {
|
|
// Seekable and index, ok...
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
|
|
// Load from stream.
|
|
r.index = &Index{}
|
|
|
|
// Read current position.
|
|
pos, err := rs.Seek(0, io.SeekCurrent)
|
|
if err != nil {
|
|
return nil, ErrCantSeek{Reason: "seeking input returned: " + err.Error()}
|
|
}
|
|
err = r.index.LoadStream(rs)
|
|
if err != nil {
|
|
if err == ErrUnsupported {
|
|
return nil, ErrCantSeek{Reason: "input stream does not contain an index"}
|
|
}
|
|
return nil, ErrCantSeek{Reason: "reading index returned: " + err.Error()}
|
|
}
|
|
|
|
// reset position.
|
|
_, err = rs.Seek(pos, io.SeekStart)
|
|
if err != nil {
|
|
return nil, ErrCantSeek{Reason: "seeking input returned: " + err.Error()}
|
|
}
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
|
|
// Seek allows seeking in compressed data.
|
|
func (r *ReadSeeker) Seek(offset int64, whence int) (int64, error) {
|
|
if r.err != nil {
|
|
return 0, r.err
|
|
}
|
|
if offset == 0 && whence == io.SeekCurrent {
|
|
return r.blockStart + int64(r.i), nil
|
|
}
|
|
if !r.readHeader {
|
|
// Make sure we read the header.
|
|
_, r.err = r.Read([]byte{})
|
|
}
|
|
rs, ok := r.r.(io.ReadSeeker)
|
|
if r.index == nil || !ok {
|
|
if whence == io.SeekCurrent && offset >= 0 {
|
|
err := r.Skip(offset)
|
|
return r.blockStart + int64(r.i), err
|
|
}
|
|
if whence == io.SeekStart && offset >= r.blockStart+int64(r.i) {
|
|
err := r.Skip(offset - r.blockStart - int64(r.i))
|
|
return r.blockStart + int64(r.i), err
|
|
}
|
|
return 0, ErrUnsupported
|
|
|
|
}
|
|
|
|
switch whence {
|
|
case io.SeekCurrent:
|
|
offset += r.blockStart + int64(r.i)
|
|
case io.SeekEnd:
|
|
offset = -offset
|
|
}
|
|
c, u, err := r.index.Find(offset)
|
|
if err != nil {
|
|
return r.blockStart + int64(r.i), err
|
|
}
|
|
|
|
// Seek to next block
|
|
_, err = rs.Seek(c, io.SeekStart)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
if offset < 0 {
|
|
offset = r.index.TotalUncompressed + offset
|
|
}
|
|
|
|
r.i = r.j // Remove rest of current block.
|
|
if u < offset {
|
|
// Forward inside block
|
|
return offset, r.Skip(offset - u)
|
|
}
|
|
return offset, nil
|
|
}
|
|
|
|
// ReadByte satisfies the io.ByteReader interface.
|
|
func (r *Reader) ReadByte() (byte, error) {
|
|
if r.err != nil {
|
|
return 0, r.err
|
|
}
|
|
if r.i < r.j {
|
|
c := r.decoded[r.i]
|
|
r.i++
|
|
return c, nil
|
|
}
|
|
var tmp [1]byte
|
|
for i := 0; i < 10; i++ {
|
|
n, err := r.Read(tmp[:])
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
if n == 1 {
|
|
return tmp[0], nil
|
|
}
|
|
}
|
|
return 0, io.ErrNoProgress
|
|
}
|
|
|
|
// SkippableCB will register a callback for chunks with the specified ID.
|
|
// ID must be a Reserved skippable chunks ID, 0x80-0xfe (inclusive).
|
|
// For each chunk with the ID, the callback is called with the content.
|
|
// Any returned non-nil error will abort decompression.
|
|
// Only one callback per ID is supported, latest sent will be used.
|
|
// Sending a nil function will disable previous callbacks.
|
|
func (r *Reader) SkippableCB(id uint8, fn func(r io.Reader) error) error {
|
|
if id < 0x80 || id > chunkTypePadding {
|
|
return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfe (inclusive)")
|
|
}
|
|
r.skippableCB[id] = fn
|
|
return nil
|
|
}
|