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436 lines
13 KiB
Go
436 lines
13 KiB
Go
// Copyright 2019+ Klaus Post. All rights reserved.
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// License information can be found in the LICENSE file.
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// Based on work by Yann Collet, released under BSD License.
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package zstd
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import (
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"encoding/binary"
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"errors"
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"hash/crc32"
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"io"
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"github.com/klauspost/compress/huff0"
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snappy "github.com/klauspost/compress/internal/snapref"
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)
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const (
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snappyTagLiteral = 0x00
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snappyTagCopy1 = 0x01
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snappyTagCopy2 = 0x02
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snappyTagCopy4 = 0x03
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)
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const (
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snappyChecksumSize = 4
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snappyMagicBody = "sNaPpY"
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// snappyMaxBlockSize is the maximum size of the input to encodeBlock. It is not
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// part of the wire format per se, but some parts of the encoder assume
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// that an offset fits into a uint16.
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//
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// Also, for the framing format (Writer type instead of Encode function),
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// https://github.com/google/snappy/blob/master/framing_format.txt says
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// that "the uncompressed data in a chunk must be no longer than 65536
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// bytes".
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snappyMaxBlockSize = 65536
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// snappyMaxEncodedLenOfMaxBlockSize equals MaxEncodedLen(snappyMaxBlockSize), but is
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// hard coded to be a const instead of a variable, so that obufLen can also
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// be a const. Their equivalence is confirmed by
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// TestMaxEncodedLenOfMaxBlockSize.
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snappyMaxEncodedLenOfMaxBlockSize = 76490
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)
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const (
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chunkTypeCompressedData = 0x00
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chunkTypeUncompressedData = 0x01
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chunkTypePadding = 0xfe
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chunkTypeStreamIdentifier = 0xff
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)
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var (
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// ErrSnappyCorrupt reports that the input is invalid.
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ErrSnappyCorrupt = errors.New("snappy: corrupt input")
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// ErrSnappyTooLarge reports that the uncompressed length is too large.
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ErrSnappyTooLarge = errors.New("snappy: decoded block is too large")
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// ErrSnappyUnsupported reports that the input isn't supported.
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ErrSnappyUnsupported = errors.New("snappy: unsupported input")
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errUnsupportedLiteralLength = errors.New("snappy: unsupported literal length")
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)
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// SnappyConverter can read SnappyConverter-compressed streams and convert them to zstd.
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// Conversion is done by converting the stream directly from Snappy without intermediate
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// full decoding.
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// Therefore the compression ratio is much less than what can be done by a full decompression
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// and compression, and a faulty Snappy stream may lead to a faulty Zstandard stream without
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// any errors being generated.
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// No CRC value is being generated and not all CRC values of the Snappy stream are checked.
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// However, it provides really fast recompression of Snappy streams.
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// The converter can be reused to avoid allocations, even after errors.
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type SnappyConverter struct {
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r io.Reader
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err error
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buf []byte
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block *blockEnc
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}
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// Convert the Snappy stream supplied in 'in' and write the zStandard stream to 'w'.
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// If any error is detected on the Snappy stream it is returned.
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// The number of bytes written is returned.
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func (r *SnappyConverter) Convert(in io.Reader, w io.Writer) (int64, error) {
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initPredefined()
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r.err = nil
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r.r = in
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if r.block == nil {
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r.block = &blockEnc{}
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r.block.init()
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}
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r.block.initNewEncode()
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if len(r.buf) != snappyMaxEncodedLenOfMaxBlockSize+snappyChecksumSize {
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r.buf = make([]byte, snappyMaxEncodedLenOfMaxBlockSize+snappyChecksumSize)
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}
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r.block.litEnc.Reuse = huff0.ReusePolicyNone
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var written int64
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var readHeader bool
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{
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var header []byte
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var n int
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header, r.err = frameHeader{WindowSize: snappyMaxBlockSize}.appendTo(r.buf[:0])
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n, r.err = w.Write(header)
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if r.err != nil {
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return written, r.err
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}
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written += int64(n)
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}
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for {
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if !r.readFull(r.buf[:4], true) {
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// Add empty last block
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r.block.reset(nil)
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r.block.last = true
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err := r.block.encodeLits(r.block.literals, false)
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if err != nil {
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return written, err
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}
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n, err := w.Write(r.block.output)
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if err != nil {
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return written, err
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}
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written += int64(n)
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return written, r.err
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}
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chunkType := r.buf[0]
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if !readHeader {
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if chunkType != chunkTypeStreamIdentifier {
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println("chunkType != chunkTypeStreamIdentifier", chunkType)
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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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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if chunkLen > len(r.buf) {
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println("chunkLen > len(r.buf)", chunkType)
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r.err = ErrSnappyUnsupported
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return written, r.err
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}
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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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// Section 4.2. Compressed data (chunk type 0x00).
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if chunkLen < snappyChecksumSize {
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println("chunkLen < snappyChecksumSize", chunkLen, snappyChecksumSize)
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r.err = ErrSnappyCorrupt
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return written, 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 written, 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[snappyChecksumSize:]
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n, hdr, err := snappyDecodedLen(buf)
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if err != nil {
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r.err = err
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return written, r.err
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}
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buf = buf[hdr:]
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if n > snappyMaxBlockSize {
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println("n > snappyMaxBlockSize", n, snappyMaxBlockSize)
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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r.block.reset(nil)
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r.block.pushOffsets()
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if err := decodeSnappy(r.block, buf); err != nil {
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r.err = err
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return written, r.err
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}
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if r.block.size+r.block.extraLits != n {
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printf("invalid size, want %d, got %d\n", n, r.block.size+r.block.extraLits)
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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err = r.block.encode(nil, false, false)
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switch err {
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case errIncompressible:
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r.block.popOffsets()
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r.block.reset(nil)
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r.block.literals, err = snappy.Decode(r.block.literals[:n], r.buf[snappyChecksumSize:chunkLen])
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if err != nil {
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return written, err
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}
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err = r.block.encodeLits(r.block.literals, false)
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if err != nil {
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return written, err
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}
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case nil:
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default:
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return written, err
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}
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n, r.err = w.Write(r.block.output)
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if r.err != nil {
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return written, err
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}
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written += int64(n)
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continue
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case chunkTypeUncompressedData:
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if debugEncoder {
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println("Uncompressed, chunklen", chunkLen)
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}
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// Section 4.3. Uncompressed data (chunk type 0x01).
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if chunkLen < snappyChecksumSize {
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println("chunkLen < snappyChecksumSize", chunkLen, snappyChecksumSize)
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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r.block.reset(nil)
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buf := r.buf[:snappyChecksumSize]
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if !r.readFull(buf, false) {
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return written, 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 - snappyChecksumSize
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if n > snappyMaxBlockSize {
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println("n > snappyMaxBlockSize", n, snappyMaxBlockSize)
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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r.block.literals = r.block.literals[:n]
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if !r.readFull(r.block.literals, false) {
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return written, r.err
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}
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if snappyCRC(r.block.literals) != checksum {
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println("literals crc mismatch")
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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err := r.block.encodeLits(r.block.literals, false)
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if err != nil {
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return written, err
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}
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n, r.err = w.Write(r.block.output)
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if r.err != nil {
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return written, err
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}
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written += int64(n)
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continue
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case chunkTypeStreamIdentifier:
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if debugEncoder {
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println("stream id", chunkLen, len(snappyMagicBody))
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}
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// Section 4.1. Stream identifier (chunk type 0xff).
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if chunkLen != len(snappyMagicBody) {
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println("chunkLen != len(snappyMagicBody)", chunkLen, len(snappyMagicBody))
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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if !r.readFull(r.buf[:len(snappyMagicBody)], false) {
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return written, r.err
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}
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for i := 0; i < len(snappyMagicBody); i++ {
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if r.buf[i] != snappyMagicBody[i] {
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println("r.buf[i] != snappyMagicBody[i]", r.buf[i], snappyMagicBody[i], i)
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r.err = ErrSnappyCorrupt
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return written, r.err
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}
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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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println("chunkType <= 0x7f")
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r.err = ErrSnappyUnsupported
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return written, 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 !r.readFull(r.buf[:chunkLen], false) {
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return written, r.err
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}
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}
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}
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// decodeSnappy writes the decoding of src to dst. It assumes that the varint-encoded
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// length of the decompressed bytes has already been read.
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func decodeSnappy(blk *blockEnc, src []byte) error {
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//decodeRef(make([]byte, snappyMaxBlockSize), src)
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var s, length int
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lits := blk.extraLits
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var offset uint32
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for s < len(src) {
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switch src[s] & 0x03 {
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case snappyTagLiteral:
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x := uint32(src[s] >> 2)
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switch {
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case x < 60:
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s++
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case x == 60:
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s += 2
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, src)
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return ErrSnappyCorrupt
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}
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x = uint32(src[s-1])
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case x == 61:
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s += 3
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, src)
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return ErrSnappyCorrupt
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}
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x = uint32(src[s-2]) | uint32(src[s-1])<<8
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case x == 62:
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s += 4
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, src)
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return ErrSnappyCorrupt
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}
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x = uint32(src[s-3]) | uint32(src[s-2])<<8 | uint32(src[s-1])<<16
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case x == 63:
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s += 5
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, src)
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return ErrSnappyCorrupt
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}
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x = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
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}
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if x > snappyMaxBlockSize {
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println("x > snappyMaxBlockSize", x, snappyMaxBlockSize)
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return ErrSnappyCorrupt
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}
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length = int(x) + 1
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if length <= 0 {
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println("length <= 0 ", length)
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return errUnsupportedLiteralLength
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}
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//if length > snappyMaxBlockSize-d || uint32(length) > len(src)-s {
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// return ErrSnappyCorrupt
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//}
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blk.literals = append(blk.literals, src[s:s+length]...)
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//println(length, "litLen")
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lits += length
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s += length
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continue
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case snappyTagCopy1:
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s += 2
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, len(src))
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return ErrSnappyCorrupt
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}
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length = 4 + int(src[s-2])>>2&0x7
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offset = uint32(src[s-2])&0xe0<<3 | uint32(src[s-1])
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case snappyTagCopy2:
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s += 3
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, len(src))
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return ErrSnappyCorrupt
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}
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length = 1 + int(src[s-3])>>2
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offset = uint32(src[s-2]) | uint32(src[s-1])<<8
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case snappyTagCopy4:
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s += 5
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if uint(s) > uint(len(src)) { // The uint conversions catch overflow from the previous line.
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println("uint(s) > uint(len(src)", s, len(src))
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return ErrSnappyCorrupt
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}
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length = 1 + int(src[s-5])>>2
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offset = uint32(src[s-4]) | uint32(src[s-3])<<8 | uint32(src[s-2])<<16 | uint32(src[s-1])<<24
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}
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if offset <= 0 || blk.size+lits < int(offset) /*|| length > len(blk)-d */ {
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println("offset <= 0 || blk.size+lits < int(offset)", offset, blk.size+lits, int(offset), blk.size, lits)
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return ErrSnappyCorrupt
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}
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// Check if offset is one of the recent offsets.
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// Adjusts the output offset accordingly.
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// Gives a tiny bit of compression, typically around 1%.
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if false {
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offset = blk.matchOffset(offset, uint32(lits))
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} else {
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offset += 3
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}
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blk.sequences = append(blk.sequences, seq{
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litLen: uint32(lits),
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offset: offset,
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matchLen: uint32(length) - zstdMinMatch,
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})
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blk.size += length + lits
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lits = 0
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}
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blk.extraLits = lits
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return nil
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}
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func (r *SnappyConverter) 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 = ErrSnappyCorrupt
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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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var crcTable = crc32.MakeTable(crc32.Castagnoli)
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// crc implements the checksum specified in section 3 of
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// https://github.com/google/snappy/blob/master/framing_format.txt
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func snappyCRC(b []byte) uint32 {
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c := crc32.Update(0, crcTable, b)
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return c>>15 | c<<17 + 0xa282ead8
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}
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// snappyDecodedLen 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 snappyDecodedLen(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, ErrSnappyCorrupt
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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, ErrSnappyTooLarge
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}
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return int(v), n, nil
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}
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