153 lines
4.4 KiB
Go
153 lines
4.4 KiB
Go
// Package zstd provides decompression of zstandard files.
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//
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// For advanced usage and examples, go to the README: https://github.com/klauspost/compress/tree/master/zstd#zstd
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package zstd
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"log"
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"math"
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"math/bits"
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)
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// enable debug printing
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const debug = false
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// enable encoding debug printing
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const debugEncoder = debug
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// enable decoding debug printing
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const debugDecoder = debug
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// Enable extra assertions.
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const debugAsserts = debug || false
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// print sequence details
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const debugSequences = false
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// print detailed matching information
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const debugMatches = false
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// force encoder to use predefined tables.
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const forcePreDef = false
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// zstdMinMatch is the minimum zstd match length.
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const zstdMinMatch = 3
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// Reset the buffer offset when reaching this.
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const bufferReset = math.MaxInt32 - MaxWindowSize
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var (
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// ErrReservedBlockType is returned when a reserved block type is found.
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// Typically this indicates wrong or corrupted input.
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ErrReservedBlockType = errors.New("invalid input: reserved block type encountered")
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// ErrCompressedSizeTooBig is returned when a block is bigger than allowed.
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// Typically this indicates wrong or corrupted input.
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ErrCompressedSizeTooBig = errors.New("invalid input: compressed size too big")
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// ErrBlockTooSmall is returned when a block is too small to be decoded.
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// Typically returned on invalid input.
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ErrBlockTooSmall = errors.New("block too small")
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// ErrMagicMismatch is returned when a "magic" number isn't what is expected.
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// Typically this indicates wrong or corrupted input.
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ErrMagicMismatch = errors.New("invalid input: magic number mismatch")
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// ErrWindowSizeExceeded is returned when a reference exceeds the valid window size.
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// Typically this indicates wrong or corrupted input.
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ErrWindowSizeExceeded = errors.New("window size exceeded")
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// ErrWindowSizeTooSmall is returned when no window size is specified.
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// Typically this indicates wrong or corrupted input.
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ErrWindowSizeTooSmall = errors.New("invalid input: window size was too small")
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// ErrDecoderSizeExceeded is returned if decompressed size exceeds the configured limit.
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ErrDecoderSizeExceeded = errors.New("decompressed size exceeds configured limit")
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// ErrUnknownDictionary is returned if the dictionary ID is unknown.
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// For the time being dictionaries are not supported.
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ErrUnknownDictionary = errors.New("unknown dictionary")
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// ErrFrameSizeExceeded is returned if the stated frame size is exceeded.
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// This is only returned if SingleSegment is specified on the frame.
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ErrFrameSizeExceeded = errors.New("frame size exceeded")
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// ErrCRCMismatch is returned if CRC mismatches.
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ErrCRCMismatch = errors.New("CRC check failed")
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// ErrDecoderClosed will be returned if the Decoder was used after
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// Close has been called.
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ErrDecoderClosed = errors.New("decoder used after Close")
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// ErrDecoderNilInput is returned when a nil Reader was provided
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// and an operation other than Reset/DecodeAll/Close was attempted.
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ErrDecoderNilInput = errors.New("nil input provided as reader")
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)
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func println(a ...interface{}) {
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if debug || debugDecoder || debugEncoder {
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log.Println(a...)
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}
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}
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func printf(format string, a ...interface{}) {
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if debug || debugDecoder || debugEncoder {
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log.Printf(format, a...)
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}
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}
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// matchLenFast does matching, but will not match the last up to 7 bytes.
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func matchLenFast(a, b []byte) int {
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endI := len(a) & (math.MaxInt32 - 7)
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for i := 0; i < endI; i += 8 {
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if diff := load64(a, i) ^ load64(b, i); diff != 0 {
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return i + bits.TrailingZeros64(diff)>>3
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}
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}
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return endI
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}
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// matchLen returns the maximum length.
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// a must be the shortest of the two.
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// The function also returns whether all bytes matched.
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func matchLen(a, b []byte) int {
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b = b[:len(a)]
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for i := 0; i < len(a)-7; i += 8 {
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if diff := load64(a, i) ^ load64(b, i); diff != 0 {
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return i + (bits.TrailingZeros64(diff) >> 3)
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}
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}
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checked := (len(a) >> 3) << 3
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a = a[checked:]
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b = b[checked:]
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for i := range a {
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if a[i] != b[i] {
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return i + checked
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}
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}
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return len(a) + checked
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}
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func load3232(b []byte, i int32) uint32 {
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return binary.LittleEndian.Uint32(b[i:])
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}
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func load6432(b []byte, i int32) uint64 {
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return binary.LittleEndian.Uint64(b[i:])
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}
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func load64(b []byte, i int) uint64 {
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return binary.LittleEndian.Uint64(b[i:])
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}
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type byter interface {
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Bytes() []byte
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Len() int
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}
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var _ byter = &bytes.Buffer{}
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