mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-24 17:51:36 +00:00
1482 lines
38 KiB
Go
1482 lines
38 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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"math"
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"runtime"
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"strconv"
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"sync"
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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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// ReaderIgnoreCRC will make the reader skip CRC calculation and checks.
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func ReaderIgnoreCRC() ReaderOption {
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return func(r *Reader) error {
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r.ignoreCRC = true
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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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ignoreCRC 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 n > r.maxBufSize {
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r.err = ErrCorrupt
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return false
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}
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if cap(r.buf) >= n {
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return true
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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.blockStart = 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 !r.ignoreCRC && 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 !r.ignoreCRC && 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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// DecodeConcurrent will decode the full stream to w.
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// This function should not be combined with reading, seeking or other operations.
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// Up to 'concurrent' goroutines will be used.
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// If <= 0, runtime.NumCPU will be used.
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// On success the number of bytes decompressed nil and is returned.
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// This is mainly intended for bigger streams.
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func (r *Reader) DecodeConcurrent(w io.Writer, concurrent int) (written int64, err error) {
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if r.i > 0 || r.j > 0 || r.blockStart > 0 {
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return 0, errors.New("DecodeConcurrent called after ")
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}
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if concurrent <= 0 {
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concurrent = runtime.NumCPU()
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}
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// Write to output
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var errMu sync.Mutex
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var aErr error
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setErr := func(e error) (ok bool) {
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errMu.Lock()
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defer errMu.Unlock()
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if e == nil {
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return aErr == nil
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}
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if aErr == nil {
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aErr = e
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}
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return false
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}
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hasErr := func() (ok bool) {
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errMu.Lock()
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v := aErr != nil
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errMu.Unlock()
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return v
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}
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var aWritten int64
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toRead := make(chan []byte, concurrent)
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writtenBlocks := make(chan []byte, concurrent)
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queue := make(chan chan []byte, concurrent)
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reUse := make(chan chan []byte, concurrent)
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for i := 0; i < concurrent; i++ {
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toRead <- make([]byte, 0, r.maxBufSize)
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writtenBlocks <- make([]byte, 0, r.maxBufSize)
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reUse <- make(chan []byte, 1)
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}
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// Writer
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var wg sync.WaitGroup
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wg.Add(1)
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go func() {
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defer wg.Done()
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for toWrite := range queue {
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entry := <-toWrite
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reUse <- toWrite
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if hasErr() {
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writtenBlocks <- entry
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continue
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}
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n, err := w.Write(entry)
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want := len(entry)
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writtenBlocks <- entry
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if err != nil {
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setErr(err)
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continue
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}
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if n != want {
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setErr(io.ErrShortWrite)
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continue
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}
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aWritten += int64(n)
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}
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}()
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|
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// Reader
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defer func() {
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close(queue)
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if r.err != nil {
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err = r.err
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setErr(r.err)
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}
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wg.Wait()
|
|
if err == nil {
|
|
err = aErr
|
|
}
|
|
written = aWritten
|
|
}()
|
|
|
|
for !hasErr() {
|
|
if !r.readFull(r.buf[:4], true) {
|
|
if r.err == io.EOF {
|
|
r.err = nil
|
|
}
|
|
return 0, r.err
|
|
}
|
|
chunkType := r.buf[0]
|
|
if !r.readHeader {
|
|
if chunkType != chunkTypeStreamIdentifier {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
r.readHeader = true
|
|
}
|
|
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
|
|
|
|
// The chunk types are specified at
|
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
|
switch chunkType {
|
|
case chunkTypeCompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.2. Compressed data (chunk type 0x00).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if chunkLen > r.maxBufSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
orgBuf := <-toRead
|
|
buf := orgBuf[:chunkLen]
|
|
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
buf = buf[checksumSize:]
|
|
|
|
n, err := DecodedLen(buf)
|
|
if err != nil {
|
|
r.err = err
|
|
return 0, r.err
|
|
}
|
|
if r.snappyFrame && n > maxSnappyBlockSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
|
|
if n > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
wg.Add(1)
|
|
|
|
decoded := <-writtenBlocks
|
|
entry := <-reUse
|
|
queue <- entry
|
|
go func() {
|
|
defer wg.Done()
|
|
decoded = decoded[:n]
|
|
_, err := Decode(decoded, buf)
|
|
toRead <- orgBuf
|
|
if err != nil {
|
|
writtenBlocks <- decoded
|
|
setErr(err)
|
|
return
|
|
}
|
|
if !r.ignoreCRC && crc(decoded) != checksum {
|
|
writtenBlocks <- decoded
|
|
setErr(ErrCRC)
|
|
return
|
|
}
|
|
entry <- decoded
|
|
}()
|
|
continue
|
|
|
|
case chunkTypeUncompressedData:
|
|
|
|
// Section 4.3. Uncompressed data (chunk type 0x01).
|
|
if chunkLen < checksumSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if chunkLen > r.maxBufSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
// Grab write buffer
|
|
orgBuf := <-writtenBlocks
|
|
buf := orgBuf[:checksumSize]
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
// Read content.
|
|
n := chunkLen - checksumSize
|
|
|
|
if r.snappyFrame && n > maxSnappyBlockSize {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if n > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
// Read uncompressed
|
|
buf = orgBuf[:n]
|
|
if !r.readFull(buf, false) {
|
|
return 0, r.err
|
|
}
|
|
|
|
if !r.ignoreCRC && crc(buf) != checksum {
|
|
r.err = ErrCRC
|
|
return 0, r.err
|
|
}
|
|
entry := <-reUse
|
|
queue <- entry
|
|
entry <- buf
|
|
continue
|
|
|
|
case chunkTypeStreamIdentifier:
|
|
// Section 4.1. Stream identifier (chunk type 0xff).
|
|
if chunkLen != len(magicBody) {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
}
|
|
if !r.readFull(r.buf[:len(magicBody)], false) {
|
|
return 0, r.err
|
|
}
|
|
if string(r.buf[:len(magicBody)]) != magicBody {
|
|
if string(r.buf[:len(magicBody)]) != magicBodySnappy {
|
|
r.err = ErrCorrupt
|
|
return 0, r.err
|
|
} else {
|
|
r.snappyFrame = true
|
|
}
|
|
} else {
|
|
r.snappyFrame = false
|
|
}
|
|
continue
|
|
}
|
|
|
|
if chunkType <= 0x7f {
|
|
// Section 4.5. Reserved unskippable chunks (chunk types 0x02-0x7f).
|
|
// fmt.Printf("ERR chunktype: 0x%x\n", chunkType)
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
// Section 4.4 Padding (chunk type 0xfe).
|
|
// Section 4.6. Reserved skippable chunks (chunk types 0x80-0xfd).
|
|
if chunkLen > maxChunkSize {
|
|
// fmt.Printf("ERR chunkLen: 0x%x\n", chunkLen)
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
|
|
// fmt.Printf("skippable: ID: 0x%x, len: 0x%x\n", chunkType, chunkLen)
|
|
if !r.skippable(r.buf, chunkLen, false, chunkType) {
|
|
return 0, r.err
|
|
}
|
|
}
|
|
return 0, r.err
|
|
}
|
|
|
|
// Skip will skip n bytes forward in the decompressed output.
|
|
// For larger skips this consumes less CPU and is faster than reading output and discarding it.
|
|
// CRC is not checked on skipped blocks.
|
|
// io.ErrUnexpectedEOF is returned if the stream ends before all bytes have been skipped.
|
|
// If a decoding error is encountered subsequent calls to Read will also fail.
|
|
func (r *Reader) Skip(n int64) error {
|
|
if n < 0 {
|
|
return errors.New("attempted negative skip")
|
|
}
|
|
if r.err != nil {
|
|
return r.err
|
|
}
|
|
|
|
for n > 0 {
|
|
if r.i < r.j {
|
|
// Skip in buffer.
|
|
// decoded[i:j] contains decoded bytes that have not yet been passed on.
|
|
left := int64(r.j - r.i)
|
|
if left >= n {
|
|
tmp := int64(r.i) + n
|
|
if tmp > math.MaxInt32 {
|
|
return errors.New("s2: internal overflow in skip")
|
|
}
|
|
r.i = int(tmp)
|
|
return nil
|
|
}
|
|
n -= int64(r.j - r.i)
|
|
r.i = r.j
|
|
}
|
|
|
|
// Buffer empty; read blocks until we have content.
|
|
if !r.readFull(r.buf[:4], true) {
|
|
if r.err == io.EOF {
|
|
r.err = io.ErrUnexpectedEOF
|
|
}
|
|
return r.err
|
|
}
|
|
chunkType := r.buf[0]
|
|
if !r.readHeader {
|
|
if chunkType != chunkTypeStreamIdentifier {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
r.readHeader = true
|
|
}
|
|
chunkLen := int(r.buf[1]) | int(r.buf[2])<<8 | int(r.buf[3])<<16
|
|
|
|
// The chunk types are specified at
|
|
// https://github.com/google/snappy/blob/master/framing_format.txt
|
|
switch chunkType {
|
|
case chunkTypeCompressedData:
|
|
r.blockStart += int64(r.j)
|
|
// Section 4.2. Compressed data (chunk type 0x00).
|
|
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[:chunkLen]
|
|
if !r.readFull(buf, false) {
|
|
return r.err
|
|
}
|
|
checksum := uint32(buf[0]) | uint32(buf[1])<<8 | uint32(buf[2])<<16 | uint32(buf[3])<<24
|
|
buf = buf[checksumSize:]
|
|
|
|
dLen, err := DecodedLen(buf)
|
|
if err != nil {
|
|
r.err = err
|
|
return r.err
|
|
}
|
|
if dLen > r.maxBlock {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
// Check if destination is within this block
|
|
if int64(dLen) > n {
|
|
if len(r.decoded) < dLen {
|
|
r.decoded = make([]byte, dLen)
|
|
}
|
|
if _, err := Decode(r.decoded, buf); err != nil {
|
|
r.err = err
|
|
return r.err
|
|
}
|
|
if crc(r.decoded[:dLen]) != checksum {
|
|
r.err = ErrCorrupt
|
|
return r.err
|
|
}
|
|
} else {
|
|
// Skip block completely
|
|
n -= int64(dLen)
|
|
r.blockStart += 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
|
|
readAtMu sync.Mutex
|
|
}
|
|
|
|
// ReadSeeker will return an io.ReadSeeker and io.ReaderAt
|
|
// 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 ReadAt position will affect regular reads and the current position of Seek.
|
|
// So using Read after ReadAt will continue from where the ReadAt stopped.
|
|
// No functions should be used concurrently.
|
|
// 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 {
|
|
// If we don't require random seeking, reset input and return.
|
|
if !random {
|
|
_, err = rs.Seek(pos, io.SeekStart)
|
|
if err != nil {
|
|
return nil, ErrCantSeek{Reason: "resetting stream returned: " + err.Error()}
|
|
}
|
|
r.index = nil
|
|
return &ReadSeeker{Reader: r}, nil
|
|
}
|
|
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 {
|
|
if !errors.Is(r.err, io.EOF) {
|
|
return 0, r.err
|
|
}
|
|
// Reset on EOF
|
|
r.err = nil
|
|
}
|
|
|
|
// Calculate absolute offset.
|
|
absOffset := offset
|
|
|
|
switch whence {
|
|
case io.SeekStart:
|
|
case io.SeekCurrent:
|
|
absOffset = r.blockStart + int64(r.i) + offset
|
|
case io.SeekEnd:
|
|
if r.index == nil {
|
|
return 0, ErrUnsupported
|
|
}
|
|
absOffset = r.index.TotalUncompressed + offset
|
|
default:
|
|
r.err = ErrUnsupported
|
|
return 0, r.err
|
|
}
|
|
|
|
if absOffset < 0 {
|
|
return 0, errors.New("seek before start of file")
|
|
}
|
|
|
|
if !r.readHeader {
|
|
// Make sure we read the header.
|
|
_, r.err = r.Read([]byte{})
|
|
if r.err != nil {
|
|
return 0, r.err
|
|
}
|
|
}
|
|
|
|
// If we are inside current block no need to seek.
|
|
// This includes no offset changes.
|
|
if absOffset >= r.blockStart && absOffset < r.blockStart+int64(r.j) {
|
|
r.i = int(absOffset - r.blockStart)
|
|
return r.blockStart + int64(r.i), nil
|
|
}
|
|
|
|
rs, ok := r.r.(io.ReadSeeker)
|
|
if r.index == nil || !ok {
|
|
currOffset := r.blockStart + int64(r.i)
|
|
if absOffset >= currOffset {
|
|
err := r.Skip(absOffset - currOffset)
|
|
return r.blockStart + int64(r.i), err
|
|
}
|
|
return 0, ErrUnsupported
|
|
}
|
|
|
|
// We can seek and we have an index.
|
|
c, u, err := r.index.Find(absOffset)
|
|
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
|
|
}
|
|
|
|
r.i = r.j // Remove rest of current block.
|
|
r.blockStart = u - int64(r.j) // Adjust current block start for accounting.
|
|
if u < absOffset {
|
|
// Forward inside block
|
|
return absOffset, r.Skip(absOffset - u)
|
|
}
|
|
if u > absOffset {
|
|
return 0, fmt.Errorf("s2 seek: (internal error) u (%d) > absOffset (%d)", u, absOffset)
|
|
}
|
|
return absOffset, nil
|
|
}
|
|
|
|
// ReadAt reads len(p) bytes into p starting at offset off in the
|
|
// underlying input source. It returns the number of bytes
|
|
// read (0 <= n <= len(p)) and any error encountered.
|
|
//
|
|
// When ReadAt returns n < len(p), it returns a non-nil error
|
|
// explaining why more bytes were not returned. In this respect,
|
|
// ReadAt is stricter than Read.
|
|
//
|
|
// Even if ReadAt returns n < len(p), it may use all of p as scratch
|
|
// space during the call. If some data is available but not len(p) bytes,
|
|
// ReadAt blocks until either all the data is available or an error occurs.
|
|
// In this respect ReadAt is different from Read.
|
|
//
|
|
// If the n = len(p) bytes returned by ReadAt are at the end of the
|
|
// input source, ReadAt may return either err == EOF or err == nil.
|
|
//
|
|
// If ReadAt is reading from an input source with a seek offset,
|
|
// ReadAt should not affect nor be affected by the underlying
|
|
// seek offset.
|
|
//
|
|
// Clients of ReadAt can execute parallel ReadAt calls on the
|
|
// same input source. This is however not recommended.
|
|
func (r *ReadSeeker) ReadAt(p []byte, offset int64) (int, error) {
|
|
r.readAtMu.Lock()
|
|
defer r.readAtMu.Unlock()
|
|
_, err := r.Seek(offset, io.SeekStart)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
n := 0
|
|
for n < len(p) {
|
|
n2, err := r.Read(p[n:])
|
|
if err != nil {
|
|
// This will include io.EOF
|
|
return n + n2, err
|
|
}
|
|
n += n2
|
|
}
|
|
return n, 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
|
|
}
|
|
|
|
// s2DecodeDict writes the decoding of src to dst. It assumes that the varint-encoded
|
|
// length of the decompressed bytes has already been read, and that len(dst)
|
|
// equals that length.
|
|
//
|
|
// It returns 0 on success or a decodeErrCodeXxx error code on failure.
|
|
func s2DecodeDict(dst, src []byte, dict *Dict) int {
|
|
if dict == nil {
|
|
return s2Decode(dst, src)
|
|
}
|
|
const debug = false
|
|
const debugErrs = debug
|
|
|
|
if debug {
|
|
fmt.Println("Starting decode, dst len:", len(dst))
|
|
}
|
|
var d, s, length int
|
|
offset := len(dict.dict) - dict.repeat
|
|
|
|
// As long as we can read at least 5 bytes...
|
|
for s < len(src)-5 {
|
|
// Removing bounds checks is SLOWER, when if doing
|
|
// in := src[s:s+5]
|
|
// Checked on Go 1.18
|
|
switch src[s] & 0x03 {
|
|
case tagLiteral:
|
|
x := uint32(src[s] >> 2)
|
|
switch {
|
|
case x < 60:
|
|
s++
|
|
case x == 60:
|
|
s += 2
|
|
x = uint32(src[s-1])
|
|
case x == 61:
|
|
in := src[s : s+3]
|
|
x = uint32(in[1]) | uint32(in[2])<<8
|
|
s += 3
|
|
case x == 62:
|
|
in := src[s : s+4]
|
|
// Load as 32 bit and shift down.
|
|
x = uint32(in[0]) | uint32(in[1])<<8 | uint32(in[2])<<16 | uint32(in[3])<<24
|
|
x >>= 8
|
|
s += 4
|
|
case x == 63:
|
|
in := src[s : s+5]
|
|
x = uint32(in[1]) | uint32(in[2])<<8 | uint32(in[3])<<16 | uint32(in[4])<<24
|
|
s += 5
|
|
}
|
|
length = int(x) + 1
|
|
if debug {
|
|
fmt.Println("literals, length:", length, "d-after:", d+length)
|
|
}
|
|
if length > len(dst)-d || length > len(src)-s || (strconv.IntSize == 32 && length <= 0) {
|
|
if debugErrs {
|
|
fmt.Println("corrupt literal: length:", length, "d-left:", len(dst)-d, "src-left:", len(src)-s)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
|
|
copy(dst[d:], src[s:s+length])
|
|
d += length
|
|
s += length
|
|
continue
|
|
|
|
case tagCopy1:
|
|
s += 2
|
|
toffset := int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
|
|
length = int(src[s-2]) >> 2 & 0x7
|
|
if toffset == 0 {
|
|
if debug {
|
|
fmt.Print("(repeat) ")
|
|
}
|
|
// keep last offset
|
|
switch length {
|
|
case 5:
|
|
length = int(src[s]) + 4
|
|
s += 1
|
|
case 6:
|
|
in := src[s : s+2]
|
|
length = int(uint32(in[0])|(uint32(in[1])<<8)) + (1 << 8)
|
|
s += 2
|
|
case 7:
|
|
in := src[s : s+3]
|
|
length = int((uint32(in[2])<<16)|(uint32(in[1])<<8)|uint32(in[0])) + (1 << 16)
|
|
s += 3
|
|
default: // 0-> 4
|
|
}
|
|
} else {
|
|
offset = toffset
|
|
}
|
|
length += 4
|
|
case tagCopy2:
|
|
in := src[s : s+3]
|
|
offset = int(uint32(in[1]) | uint32(in[2])<<8)
|
|
length = 1 + int(in[0])>>2
|
|
s += 3
|
|
|
|
case tagCopy4:
|
|
in := src[s : s+5]
|
|
offset = int(uint32(in[1]) | uint32(in[2])<<8 | uint32(in[3])<<16 | uint32(in[4])<<24)
|
|
length = 1 + int(in[0])>>2
|
|
s += 5
|
|
}
|
|
|
|
if offset <= 0 || length > len(dst)-d {
|
|
if debugErrs {
|
|
fmt.Println("match error; offset:", offset, "length:", length, "dst-left:", len(dst)-d)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
|
|
// copy from dict
|
|
if d < offset {
|
|
if d > MaxDictSrcOffset {
|
|
if debugErrs {
|
|
fmt.Println("dict after", MaxDictSrcOffset, "d:", d, "offset:", offset, "length:", length)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
startOff := len(dict.dict) - offset + d
|
|
if startOff < 0 || startOff+length > len(dict.dict) {
|
|
if debugErrs {
|
|
fmt.Printf("offset (%d) + length (%d) bigger than dict (%d)\n", offset, length, len(dict.dict))
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
if debug {
|
|
fmt.Println("dict copy, length:", length, "offset:", offset, "d-after:", d+length, "dict start offset:", startOff)
|
|
}
|
|
copy(dst[d:d+length], dict.dict[startOff:])
|
|
d += length
|
|
continue
|
|
}
|
|
|
|
if debug {
|
|
fmt.Println("copy, length:", length, "offset:", offset, "d-after:", d+length)
|
|
}
|
|
|
|
// Copy from an earlier sub-slice of dst to a later sub-slice.
|
|
// If no overlap, use the built-in copy:
|
|
if offset > length {
|
|
copy(dst[d:d+length], dst[d-offset:])
|
|
d += length
|
|
continue
|
|
}
|
|
|
|
// Unlike the built-in copy function, this byte-by-byte copy always runs
|
|
// forwards, even if the slices overlap. Conceptually, this is:
|
|
//
|
|
// d += forwardCopy(dst[d:d+length], dst[d-offset:])
|
|
//
|
|
// We align the slices into a and b and show the compiler they are the same size.
|
|
// This allows the loop to run without bounds checks.
|
|
a := dst[d : d+length]
|
|
b := dst[d-offset:]
|
|
b = b[:len(a)]
|
|
for i := range a {
|
|
a[i] = b[i]
|
|
}
|
|
d += length
|
|
}
|
|
|
|
// Remaining with extra checks...
|
|
for s < len(src) {
|
|
switch src[s] & 0x03 {
|
|
case tagLiteral:
|
|
x := uint32(src[s] >> 2)
|
|
switch {
|
|
case x < 60:
|
|
s++
|
|
case x == 60:
|
|
s += 2
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-1])
|
|
case x == 61:
|
|
s += 3
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-2]) | uint32(src[s-1])<<8
|
|
case x == 62:
|
|
s += 4
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
|
|
case x == 63:
|
|
s += 5
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
|
|
}
|
|
length = int(x) + 1
|
|
if length > len(dst)-d || length > len(src)-s || (strconv.IntSize == 32 && length <= 0) {
|
|
if debugErrs {
|
|
fmt.Println("corrupt literal: length:", length, "d-left:", len(dst)-d, "src-left:", len(src)-s)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
if debug {
|
|
fmt.Println("literals, length:", length, "d-after:", d+length)
|
|
}
|
|
|
|
copy(dst[d:], src[s:s+length])
|
|
d += length
|
|
s += length
|
|
continue
|
|
|
|
case tagCopy1:
|
|
s += 2
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(src[s-2]) >> 2 & 0x7
|
|
toffset := int(uint32(src[s-2])&0xe0<<3 | uint32(src[s-1]))
|
|
if toffset == 0 {
|
|
if debug {
|
|
fmt.Print("(repeat) ")
|
|
}
|
|
// keep last offset
|
|
switch length {
|
|
case 5:
|
|
s += 1
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(uint32(src[s-1])) + 4
|
|
case 6:
|
|
s += 2
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(uint32(src[s-2])|(uint32(src[s-1])<<8)) + (1 << 8)
|
|
case 7:
|
|
s += 3
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = int(uint32(src[s-3])|(uint32(src[s-2])<<8)|(uint32(src[s-1])<<16)) + (1 << 16)
|
|
default: // 0-> 4
|
|
}
|
|
} else {
|
|
offset = toffset
|
|
}
|
|
length += 4
|
|
case tagCopy2:
|
|
s += 3
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = 1 + int(src[s-3])>>2
|
|
offset = int(uint32(src[s-2]) | uint32(src[s-1])<<8)
|
|
|
|
case tagCopy4:
|
|
s += 5
|
|
if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
|
|
if debugErrs {
|
|
fmt.Println("src went oob")
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
length = 1 + int(src[s-5])>>2
|
|
offset = int(uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24)
|
|
}
|
|
|
|
if offset <= 0 || length > len(dst)-d {
|
|
if debugErrs {
|
|
fmt.Println("match error; offset:", offset, "length:", length, "dst-left:", len(dst)-d)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
|
|
// copy from dict
|
|
if d < offset {
|
|
if d > MaxDictSrcOffset {
|
|
if debugErrs {
|
|
fmt.Println("dict after", MaxDictSrcOffset, "d:", d, "offset:", offset, "length:", length)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
rOff := len(dict.dict) - (offset - d)
|
|
if debug {
|
|
fmt.Println("starting dict entry from dict offset", len(dict.dict)-rOff)
|
|
}
|
|
if rOff+length > len(dict.dict) {
|
|
if debugErrs {
|
|
fmt.Println("err: END offset", rOff+length, "bigger than dict", len(dict.dict), "dict offset:", rOff, "length:", length)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
if rOff < 0 {
|
|
if debugErrs {
|
|
fmt.Println("err: START offset", rOff, "less than 0", len(dict.dict), "dict offset:", rOff, "length:", length)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
copy(dst[d:d+length], dict.dict[rOff:])
|
|
d += length
|
|
continue
|
|
}
|
|
|
|
if debug {
|
|
fmt.Println("copy, length:", length, "offset:", offset, "d-after:", d+length)
|
|
}
|
|
|
|
// Copy from an earlier sub-slice of dst to a later sub-slice.
|
|
// If no overlap, use the built-in copy:
|
|
if offset > length {
|
|
copy(dst[d:d+length], dst[d-offset:])
|
|
d += length
|
|
continue
|
|
}
|
|
|
|
// Unlike the built-in copy function, this byte-by-byte copy always runs
|
|
// forwards, even if the slices overlap. Conceptually, this is:
|
|
//
|
|
// d += forwardCopy(dst[d:d+length], dst[d-offset:])
|
|
//
|
|
// We align the slices into a and b and show the compiler they are the same size.
|
|
// This allows the loop to run without bounds checks.
|
|
a := dst[d : d+length]
|
|
b := dst[d-offset:]
|
|
b = b[:len(a)]
|
|
for i := range a {
|
|
a[i] = b[i]
|
|
}
|
|
d += length
|
|
}
|
|
|
|
if d != len(dst) {
|
|
if debugErrs {
|
|
fmt.Println("wanted length", len(dst), "got", d)
|
|
}
|
|
return decodeErrCodeCorrupt
|
|
}
|
|
return 0
|
|
}
|