diff options
Diffstat (limited to 'vendor/github.com/klauspost/compress/flate/stateless.go')
-rw-r--r-- | vendor/github.com/klauspost/compress/flate/stateless.go | 318 |
1 files changed, 0 insertions, 318 deletions
diff --git a/vendor/github.com/klauspost/compress/flate/stateless.go b/vendor/github.com/klauspost/compress/flate/stateless.go deleted file mode 100644 index f3d4139ef..000000000 --- a/vendor/github.com/klauspost/compress/flate/stateless.go +++ /dev/null @@ -1,318 +0,0 @@ -package flate - -import ( - "io" - "math" - "sync" -) - -const ( - maxStatelessBlock = math.MaxInt16 - // dictionary will be taken from maxStatelessBlock, so limit it. - maxStatelessDict = 8 << 10 - - slTableBits = 13 - slTableSize = 1 << slTableBits - slTableShift = 32 - slTableBits -) - -type statelessWriter struct { - dst io.Writer - closed bool -} - -func (s *statelessWriter) Close() error { - if s.closed { - return nil - } - s.closed = true - // Emit EOF block - return StatelessDeflate(s.dst, nil, true, nil) -} - -func (s *statelessWriter) Write(p []byte) (n int, err error) { - err = StatelessDeflate(s.dst, p, false, nil) - if err != nil { - return 0, err - } - return len(p), nil -} - -func (s *statelessWriter) Reset(w io.Writer) { - s.dst = w - s.closed = false -} - -// NewStatelessWriter will do compression but without maintaining any state -// between Write calls. -// There will be no memory kept between Write calls, -// but compression and speed will be suboptimal. -// Because of this, the size of actual Write calls will affect output size. -func NewStatelessWriter(dst io.Writer) io.WriteCloser { - return &statelessWriter{dst: dst} -} - -// bitWriterPool contains bit writers that can be reused. -var bitWriterPool = sync.Pool{ - New: func() interface{} { - return newHuffmanBitWriter(nil) - }, -} - -// StatelessDeflate allows compressing directly to a Writer without retaining state. -// When returning everything will be flushed. -// Up to 8KB of an optional dictionary can be given which is presumed to precede the block. -// Longer dictionaries will be truncated and will still produce valid output. -// Sending nil dictionary is perfectly fine. -func StatelessDeflate(out io.Writer, in []byte, eof bool, dict []byte) error { - var dst tokens - bw := bitWriterPool.Get().(*huffmanBitWriter) - bw.reset(out) - defer func() { - // don't keep a reference to our output - bw.reset(nil) - bitWriterPool.Put(bw) - }() - if eof && len(in) == 0 { - // Just write an EOF block. - // Could be faster... - bw.writeStoredHeader(0, true) - bw.flush() - return bw.err - } - - // Truncate dict - if len(dict) > maxStatelessDict { - dict = dict[len(dict)-maxStatelessDict:] - } - - // For subsequent loops, keep shallow dict reference to avoid alloc+copy. - var inDict []byte - - for len(in) > 0 { - todo := in - if len(inDict) > 0 { - if len(todo) > maxStatelessBlock-maxStatelessDict { - todo = todo[:maxStatelessBlock-maxStatelessDict] - } - } else if len(todo) > maxStatelessBlock-len(dict) { - todo = todo[:maxStatelessBlock-len(dict)] - } - inOrg := in - in = in[len(todo):] - uncompressed := todo - if len(dict) > 0 { - // combine dict and source - bufLen := len(todo) + len(dict) - combined := make([]byte, bufLen) - copy(combined, dict) - copy(combined[len(dict):], todo) - todo = combined - } - // Compress - if len(inDict) == 0 { - statelessEnc(&dst, todo, int16(len(dict))) - } else { - statelessEnc(&dst, inDict[:maxStatelessDict+len(todo)], maxStatelessDict) - } - isEof := eof && len(in) == 0 - - if dst.n == 0 { - bw.writeStoredHeader(len(uncompressed), isEof) - if bw.err != nil { - return bw.err - } - bw.writeBytes(uncompressed) - } else if int(dst.n) > len(uncompressed)-len(uncompressed)>>4 { - // If we removed less than 1/16th, huffman compress the block. - bw.writeBlockHuff(isEof, uncompressed, len(in) == 0) - } else { - bw.writeBlockDynamic(&dst, isEof, uncompressed, len(in) == 0) - } - if len(in) > 0 { - // Retain a dict if we have more - inDict = inOrg[len(uncompressed)-maxStatelessDict:] - dict = nil - dst.Reset() - } - if bw.err != nil { - return bw.err - } - } - if !eof { - // Align, only a stored block can do that. - bw.writeStoredHeader(0, false) - } - bw.flush() - return bw.err -} - -func hashSL(u uint32) uint32 { - return (u * 0x1e35a7bd) >> slTableShift -} - -func load3216(b []byte, i int16) uint32 { - // Help the compiler eliminate bounds checks on the read so it can be done in a single read. - b = b[i:] - b = b[:4] - return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24 -} - -func load6416(b []byte, i int16) uint64 { - // Help the compiler eliminate bounds checks on the read so it can be done in a single read. - b = b[i:] - b = b[:8] - return uint64(b[0]) | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 | - uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56 -} - -func statelessEnc(dst *tokens, src []byte, startAt int16) { - const ( - inputMargin = 12 - 1 - minNonLiteralBlockSize = 1 + 1 + inputMargin - ) - - type tableEntry struct { - offset int16 - } - - var table [slTableSize]tableEntry - - // This check isn't in the Snappy implementation, but there, the caller - // instead of the callee handles this case. - if len(src)-int(startAt) < minNonLiteralBlockSize { - // We do not fill the token table. - // This will be picked up by caller. - dst.n = 0 - return - } - // Index until startAt - if startAt > 0 { - cv := load3232(src, 0) - for i := int16(0); i < startAt; i++ { - table[hashSL(cv)] = tableEntry{offset: i} - cv = (cv >> 8) | (uint32(src[i+4]) << 24) - } - } - - s := startAt + 1 - nextEmit := startAt - // sLimit is when to stop looking for offset/length copies. The inputMargin - // lets us use a fast path for emitLiteral in the main loop, while we are - // looking for copies. - sLimit := int16(len(src) - inputMargin) - - // nextEmit is where in src the next emitLiteral should start from. - cv := load3216(src, s) - - for { - const skipLog = 5 - const doEvery = 2 - - nextS := s - var candidate tableEntry - for { - nextHash := hashSL(cv) - candidate = table[nextHash] - nextS = s + doEvery + (s-nextEmit)>>skipLog - if nextS > sLimit || nextS <= 0 { - goto emitRemainder - } - - now := load6416(src, nextS) - table[nextHash] = tableEntry{offset: s} - nextHash = hashSL(uint32(now)) - - if cv == load3216(src, candidate.offset) { - table[nextHash] = tableEntry{offset: nextS} - break - } - - // Do one right away... - cv = uint32(now) - s = nextS - nextS++ - candidate = table[nextHash] - now >>= 8 - table[nextHash] = tableEntry{offset: s} - - if cv == load3216(src, candidate.offset) { - table[nextHash] = tableEntry{offset: nextS} - break - } - cv = uint32(now) - s = nextS - } - - // A 4-byte match has been found. We'll later see if more than 4 bytes - // match. But, prior to the match, src[nextEmit:s] are unmatched. Emit - // them as literal bytes. - for { - // Invariant: we have a 4-byte match at s, and no need to emit any - // literal bytes prior to s. - - // Extend the 4-byte match as long as possible. - t := candidate.offset - l := int16(matchLen(src[s+4:], src[t+4:]) + 4) - - // Extend backwards - for t > 0 && s > nextEmit && src[t-1] == src[s-1] { - s-- - t-- - l++ - } - if nextEmit < s { - if false { - emitLiteral(dst, src[nextEmit:s]) - } else { - for _, v := range src[nextEmit:s] { - dst.tokens[dst.n] = token(v) - dst.litHist[v]++ - dst.n++ - } - } - } - - // Save the match found - dst.AddMatchLong(int32(l), uint32(s-t-baseMatchOffset)) - s += l - nextEmit = s - if nextS >= s { - s = nextS + 1 - } - if s >= sLimit { - goto emitRemainder - } - - // We could immediately start working at s now, but to improve - // compression we first update the hash table at s-2 and at s. If - // another emitCopy is not our next move, also calculate nextHash - // at s+1. At least on GOARCH=amd64, these three hash calculations - // are faster as one load64 call (with some shifts) instead of - // three load32 calls. - x := load6416(src, s-2) - o := s - 2 - prevHash := hashSL(uint32(x)) - table[prevHash] = tableEntry{offset: o} - x >>= 16 - currHash := hashSL(uint32(x)) - candidate = table[currHash] - table[currHash] = tableEntry{offset: o + 2} - - if uint32(x) != load3216(src, candidate.offset) { - cv = uint32(x >> 8) - s++ - break - } - } - } - -emitRemainder: - if int(nextEmit) < len(src) { - // If nothing was added, don't encode literals. - if dst.n == 0 { - return - } - emitLiteral(dst, src[nextEmit:]) - } -} |