662 lines
16 KiB
Go
662 lines
16 KiB
Go
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// 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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"fmt"
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"math"
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"math/bits"
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)
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const (
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tableBits = 15 // Bits used in the table
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tableSize = 1 << tableBits // Size of the table
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tableMask = tableSize - 1 // Mask for table indices. Redundant, but can eliminate bounds checks.
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maxMatchLength = 131074
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)
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type tableEntry struct {
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val uint32
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offset int32
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}
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type fastEncoder struct {
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fastBase
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table [tableSize]tableEntry
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dictTable []tableEntry
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}
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// Encode mimmics functionality in zstd_fast.c
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func (e *fastEncoder) Encode(blk *blockEnc, src []byte) {
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const (
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inputMargin = 8
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minNonLiteralBlockSize = 1 + 1 + inputMargin
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)
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// Protect against e.cur wraparound.
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for e.cur >= bufferReset {
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if len(e.hist) == 0 {
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for i := range e.table[:] {
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e.table[i] = tableEntry{}
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}
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e.cur = e.maxMatchOff
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break
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}
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// Shift down everything in the table that isn't already too far away.
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minOff := e.cur + int32(len(e.hist)) - e.maxMatchOff
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for i := range e.table[:] {
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v := e.table[i].offset
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if v < minOff {
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v = 0
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} else {
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v = v - e.cur + e.maxMatchOff
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}
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e.table[i].offset = v
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}
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e.cur = e.maxMatchOff
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break
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}
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s := e.addBlock(src)
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blk.size = len(src)
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if len(src) < minNonLiteralBlockSize {
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blk.extraLits = len(src)
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blk.literals = blk.literals[:len(src)]
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copy(blk.literals, src)
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return
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}
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// Override src
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src = e.hist
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sLimit := int32(len(src)) - inputMargin
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// stepSize is the number of bytes to skip on every main loop iteration.
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// It should be >= 2.
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const stepSize = 2
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// TEMPLATE
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const hashLog = tableBits
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// seems global, but would be nice to tweak.
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const kSearchStrength = 8
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// nextEmit is where in src the next emitLiteral should start from.
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nextEmit := s
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cv := load6432(src, s)
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// Relative offsets
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offset1 := int32(blk.recentOffsets[0])
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offset2 := int32(blk.recentOffsets[1])
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addLiterals := func(s *seq, until int32) {
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if until == nextEmit {
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return
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}
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blk.literals = append(blk.literals, src[nextEmit:until]...)
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s.litLen = uint32(until - nextEmit)
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}
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if debug {
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println("recent offsets:", blk.recentOffsets)
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}
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encodeLoop:
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for {
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// t will contain the match offset when we find one.
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// When existing the search loop, we have already checked 4 bytes.
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var t int32
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// We will not use repeat offsets across blocks.
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// By not using them for the first 3 matches
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canRepeat := len(blk.sequences) > 2
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for {
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if debugAsserts && canRepeat && offset1 == 0 {
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panic("offset0 was 0")
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}
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nextHash := hash6(cv, hashLog)
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nextHash2 := hash6(cv>>8, hashLog)
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candidate := e.table[nextHash]
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candidate2 := e.table[nextHash2]
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repIndex := s - offset1 + 2
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e.table[nextHash] = tableEntry{offset: s + e.cur, val: uint32(cv)}
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e.table[nextHash2] = tableEntry{offset: s + e.cur + 1, val: uint32(cv >> 8)}
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if canRepeat && repIndex >= 0 && load3232(src, repIndex) == uint32(cv>>16) {
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// Consider history as well.
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var seq seq
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var length int32
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// length = 4 + e.matchlen(s+6, repIndex+4, src)
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{
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a := src[s+6:]
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b := src[repIndex+4:]
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endI := len(a) & (math.MaxInt32 - 7)
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length = int32(endI) + 4
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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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length = int32(i+bits.TrailingZeros64(diff)>>3) + 4
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break
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}
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}
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}
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seq.matchLen = uint32(length - zstdMinMatch)
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// We might be able to match backwards.
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// Extend as long as we can.
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start := s + 2
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// We end the search early, so we don't risk 0 literals
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// and have to do special offset treatment.
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startLimit := nextEmit + 1
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sMin := s - e.maxMatchOff
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if sMin < 0 {
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sMin = 0
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}
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for repIndex > sMin && start > startLimit && src[repIndex-1] == src[start-1] && seq.matchLen < maxMatchLength-zstdMinMatch {
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repIndex--
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start--
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seq.matchLen++
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}
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addLiterals(&seq, start)
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// rep 0
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seq.offset = 1
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if debugSequences {
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println("repeat sequence", seq, "next s:", s)
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}
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blk.sequences = append(blk.sequences, seq)
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s += length + 2
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nextEmit = s
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if s >= sLimit {
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if debug {
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println("repeat ended", s, length)
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}
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break encodeLoop
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}
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cv = load6432(src, s)
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continue
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}
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coffset0 := s - (candidate.offset - e.cur)
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coffset1 := s - (candidate2.offset - e.cur) + 1
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if coffset0 < e.maxMatchOff && uint32(cv) == candidate.val {
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// found a regular match
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t = candidate.offset - e.cur
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if debugAsserts && s <= t {
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panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
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}
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if debugAsserts && s-t > e.maxMatchOff {
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panic("s - t >e.maxMatchOff")
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}
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break
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}
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if coffset1 < e.maxMatchOff && uint32(cv>>8) == candidate2.val {
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// found a regular match
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t = candidate2.offset - e.cur
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s++
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if debugAsserts && s <= t {
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panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
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}
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if debugAsserts && s-t > e.maxMatchOff {
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panic("s - t >e.maxMatchOff")
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}
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if debugAsserts && t < 0 {
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panic("t<0")
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}
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break
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}
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s += stepSize + ((s - nextEmit) >> (kSearchStrength - 1))
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if s >= sLimit {
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break encodeLoop
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}
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cv = load6432(src, s)
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}
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// A 4-byte match has been found. We'll later see if more than 4 bytes.
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offset2 = offset1
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offset1 = s - t
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if debugAsserts && s <= t {
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panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
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}
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if debugAsserts && canRepeat && int(offset1) > len(src) {
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panic("invalid offset")
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}
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// Extend the 4-byte match as long as possible.
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//l := e.matchlen(s+4, t+4, src) + 4
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var l int32
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{
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a := src[s+4:]
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b := src[t+4:]
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endI := len(a) & (math.MaxInt32 - 7)
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l = int32(endI) + 4
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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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l = int32(i+bits.TrailingZeros64(diff)>>3) + 4
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break
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}
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}
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}
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// Extend backwards
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tMin := s - e.maxMatchOff
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if tMin < 0 {
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tMin = 0
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}
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for t > tMin && s > nextEmit && src[t-1] == src[s-1] && l < maxMatchLength {
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s--
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t--
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l++
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}
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// Write our sequence.
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var seq seq
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seq.litLen = uint32(s - nextEmit)
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seq.matchLen = uint32(l - zstdMinMatch)
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if seq.litLen > 0 {
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blk.literals = append(blk.literals, src[nextEmit:s]...)
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}
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// Don't use repeat offsets
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seq.offset = uint32(s-t) + 3
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s += l
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if debugSequences {
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println("sequence", seq, "next s:", s)
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}
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blk.sequences = append(blk.sequences, seq)
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nextEmit = s
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if s >= sLimit {
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break encodeLoop
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}
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cv = load6432(src, s)
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// Check offset 2
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if o2 := s - offset2; canRepeat && load3232(src, o2) == uint32(cv) {
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// We have at least 4 byte match.
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// No need to check backwards. We come straight from a match
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//l := 4 + e.matchlen(s+4, o2+4, src)
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var l int32
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{
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a := src[s+4:]
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b := src[o2+4:]
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endI := len(a) & (math.MaxInt32 - 7)
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l = int32(endI) + 4
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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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l = int32(i+bits.TrailingZeros64(diff)>>3) + 4
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break
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}
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}
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}
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// Store this, since we have it.
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nextHash := hash6(cv, hashLog)
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e.table[nextHash] = tableEntry{offset: s + e.cur, val: uint32(cv)}
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seq.matchLen = uint32(l) - zstdMinMatch
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seq.litLen = 0
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// Since litlen is always 0, this is offset 1.
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seq.offset = 1
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s += l
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nextEmit = s
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if debugSequences {
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println("sequence", seq, "next s:", s)
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}
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blk.sequences = append(blk.sequences, seq)
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// Swap offset 1 and 2.
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offset1, offset2 = offset2, offset1
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if s >= sLimit {
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break encodeLoop
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}
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// Prepare next loop.
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cv = load6432(src, s)
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}
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}
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if int(nextEmit) < len(src) {
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blk.literals = append(blk.literals, src[nextEmit:]...)
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blk.extraLits = len(src) - int(nextEmit)
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}
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blk.recentOffsets[0] = uint32(offset1)
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blk.recentOffsets[1] = uint32(offset2)
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if debug {
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println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits)
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}
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}
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// EncodeNoHist will encode a block with no history and no following blocks.
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// Most notable difference is that src will not be copied for history and
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// we do not need to check for max match length.
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func (e *fastEncoder) EncodeNoHist(blk *blockEnc, src []byte) {
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|
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const (
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inputMargin = 8
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minNonLiteralBlockSize = 1 + 1 + inputMargin
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)
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if debug {
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if len(src) > maxBlockSize {
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panic("src too big")
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}
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}
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// Protect against e.cur wraparound.
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if e.cur >= bufferReset {
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for i := range e.table[:] {
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e.table[i] = tableEntry{}
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}
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e.cur = e.maxMatchOff
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}
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s := int32(0)
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blk.size = len(src)
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if len(src) < minNonLiteralBlockSize {
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blk.extraLits = len(src)
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blk.literals = blk.literals[:len(src)]
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copy(blk.literals, src)
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return
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||
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}
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||
|
|
|
||
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sLimit := int32(len(src)) - inputMargin
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|
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// stepSize is the number of bytes to skip on every main loop iteration.
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||
|
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// It should be >= 2.
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||
|
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const stepSize = 2
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|
|
|
||
|
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// TEMPLATE
|
||
|
|
const hashLog = tableBits
|
||
|
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// seems global, but would be nice to tweak.
|
||
|
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const kSearchStrength = 8
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||
|
|
|
||
|
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// nextEmit is where in src the next emitLiteral should start from.
|
||
|
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nextEmit := s
|
||
|
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cv := load6432(src, s)
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|
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// Relative offsets
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||
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offset1 := int32(blk.recentOffsets[0])
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||
|
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offset2 := int32(blk.recentOffsets[1])
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||
|
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|
||
|
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addLiterals := func(s *seq, until int32) {
|
||
|
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if until == nextEmit {
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return
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}
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blk.literals = append(blk.literals, src[nextEmit:until]...)
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s.litLen = uint32(until - nextEmit)
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}
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||
|
|
if debug {
|
||
|
|
println("recent offsets:", blk.recentOffsets)
|
||
|
|
}
|
||
|
|
|
||
|
|
encodeLoop:
|
||
|
|
for {
|
||
|
|
// t will contain the match offset when we find one.
|
||
|
|
// When existing the search loop, we have already checked 4 bytes.
|
||
|
|
var t int32
|
||
|
|
|
||
|
|
// We will not use repeat offsets across blocks.
|
||
|
|
// By not using them for the first 3 matches
|
||
|
|
|
||
|
|
for {
|
||
|
|
nextHash := hash6(cv, hashLog)
|
||
|
|
nextHash2 := hash6(cv>>8, hashLog)
|
||
|
|
candidate := e.table[nextHash]
|
||
|
|
candidate2 := e.table[nextHash2]
|
||
|
|
repIndex := s - offset1 + 2
|
||
|
|
|
||
|
|
e.table[nextHash] = tableEntry{offset: s + e.cur, val: uint32(cv)}
|
||
|
|
e.table[nextHash2] = tableEntry{offset: s + e.cur + 1, val: uint32(cv >> 8)}
|
||
|
|
|
||
|
|
if len(blk.sequences) > 2 && load3232(src, repIndex) == uint32(cv>>16) {
|
||
|
|
// Consider history as well.
|
||
|
|
var seq seq
|
||
|
|
// length := 4 + e.matchlen(s+6, repIndex+4, src)
|
||
|
|
// length := 4 + int32(matchLen(src[s+6:], src[repIndex+4:]))
|
||
|
|
var length int32
|
||
|
|
{
|
||
|
|
a := src[s+6:]
|
||
|
|
b := src[repIndex+4:]
|
||
|
|
endI := len(a) & (math.MaxInt32 - 7)
|
||
|
|
length = int32(endI) + 4
|
||
|
|
for i := 0; i < endI; i += 8 {
|
||
|
|
if diff := load64(a, i) ^ load64(b, i); diff != 0 {
|
||
|
|
length = int32(i+bits.TrailingZeros64(diff)>>3) + 4
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
seq.matchLen = uint32(length - zstdMinMatch)
|
||
|
|
|
||
|
|
// We might be able to match backwards.
|
||
|
|
// Extend as long as we can.
|
||
|
|
start := s + 2
|
||
|
|
// We end the search early, so we don't risk 0 literals
|
||
|
|
// and have to do special offset treatment.
|
||
|
|
startLimit := nextEmit + 1
|
||
|
|
|
||
|
|
sMin := s - e.maxMatchOff
|
||
|
|
if sMin < 0 {
|
||
|
|
sMin = 0
|
||
|
|
}
|
||
|
|
for repIndex > sMin && start > startLimit && src[repIndex-1] == src[start-1] {
|
||
|
|
repIndex--
|
||
|
|
start--
|
||
|
|
seq.matchLen++
|
||
|
|
}
|
||
|
|
addLiterals(&seq, start)
|
||
|
|
|
||
|
|
// rep 0
|
||
|
|
seq.offset = 1
|
||
|
|
if debugSequences {
|
||
|
|
println("repeat sequence", seq, "next s:", s)
|
||
|
|
}
|
||
|
|
blk.sequences = append(blk.sequences, seq)
|
||
|
|
s += length + 2
|
||
|
|
nextEmit = s
|
||
|
|
if s >= sLimit {
|
||
|
|
if debug {
|
||
|
|
println("repeat ended", s, length)
|
||
|
|
|
||
|
|
}
|
||
|
|
break encodeLoop
|
||
|
|
}
|
||
|
|
cv = load6432(src, s)
|
||
|
|
continue
|
||
|
|
}
|
||
|
|
coffset0 := s - (candidate.offset - e.cur)
|
||
|
|
coffset1 := s - (candidate2.offset - e.cur) + 1
|
||
|
|
if coffset0 < e.maxMatchOff && uint32(cv) == candidate.val {
|
||
|
|
// found a regular match
|
||
|
|
t = candidate.offset - e.cur
|
||
|
|
if debugAsserts && s <= t {
|
||
|
|
panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
|
||
|
|
}
|
||
|
|
if debugAsserts && s-t > e.maxMatchOff {
|
||
|
|
panic("s - t >e.maxMatchOff")
|
||
|
|
}
|
||
|
|
if debugAsserts && t < 0 {
|
||
|
|
panic(fmt.Sprintf("t (%d) < 0, candidate.offset: %d, e.cur: %d, coffset0: %d, e.maxMatchOff: %d", t, candidate.offset, e.cur, coffset0, e.maxMatchOff))
|
||
|
|
}
|
||
|
|
break
|
||
|
|
}
|
||
|
|
|
||
|
|
if coffset1 < e.maxMatchOff && uint32(cv>>8) == candidate2.val {
|
||
|
|
// found a regular match
|
||
|
|
t = candidate2.offset - e.cur
|
||
|
|
s++
|
||
|
|
if debugAsserts && s <= t {
|
||
|
|
panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
|
||
|
|
}
|
||
|
|
if debugAsserts && s-t > e.maxMatchOff {
|
||
|
|
panic("s - t >e.maxMatchOff")
|
||
|
|
}
|
||
|
|
if debugAsserts && t < 0 {
|
||
|
|
panic("t<0")
|
||
|
|
}
|
||
|
|
break
|
||
|
|
}
|
||
|
|
s += stepSize + ((s - nextEmit) >> (kSearchStrength - 1))
|
||
|
|
if s >= sLimit {
|
||
|
|
break encodeLoop
|
||
|
|
}
|
||
|
|
cv = load6432(src, s)
|
||
|
|
}
|
||
|
|
// A 4-byte match has been found. We'll later see if more than 4 bytes.
|
||
|
|
offset2 = offset1
|
||
|
|
offset1 = s - t
|
||
|
|
|
||
|
|
if debugAsserts && s <= t {
|
||
|
|
panic(fmt.Sprintf("s (%d) <= t (%d)", s, t))
|
||
|
|
}
|
||
|
|
|
||
|
|
if debugAsserts && t < 0 {
|
||
|
|
panic(fmt.Sprintf("t (%d) < 0 ", t))
|
||
|
|
}
|
||
|
|
// Extend the 4-byte match as long as possible.
|
||
|
|
//l := e.matchlenNoHist(s+4, t+4, src) + 4
|
||
|
|
// l := int32(matchLen(src[s+4:], src[t+4:])) + 4
|
||
|
|
var l int32
|
||
|
|
{
|
||
|
|
a := src[s+4:]
|
||
|
|
b := src[t+4:]
|
||
|
|
endI := len(a) & (math.MaxInt32 - 7)
|
||
|
|
l = int32(endI) + 4
|
||
|
|
for i := 0; i < endI; i += 8 {
|
||
|
|
if diff := load64(a, i) ^ load64(b, i); diff != 0 {
|
||
|
|
l = int32(i+bits.TrailingZeros64(diff)>>3) + 4
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Extend backwards
|
||
|
|
tMin := s - e.maxMatchOff
|
||
|
|
if tMin < 0 {
|
||
|
|
tMin = 0
|
||
|
|
}
|
||
|
|
for t > tMin && s > nextEmit && src[t-1] == src[s-1] {
|
||
|
|
s--
|
||
|
|
t--
|
||
|
|
l++
|
||
|
|
}
|
||
|
|
|
||
|
|
// Write our sequence.
|
||
|
|
var seq seq
|
||
|
|
seq.litLen = uint32(s - nextEmit)
|
||
|
|
seq.matchLen = uint32(l - zstdMinMatch)
|
||
|
|
if seq.litLen > 0 {
|
||
|
|
blk.literals = append(blk.literals, src[nextEmit:s]...)
|
||
|
|
}
|
||
|
|
// Don't use repeat offsets
|
||
|
|
seq.offset = uint32(s-t) + 3
|
||
|
|
s += l
|
||
|
|
if debugSequences {
|
||
|
|
println("sequence", seq, "next s:", s)
|
||
|
|
}
|
||
|
|
blk.sequences = append(blk.sequences, seq)
|
||
|
|
nextEmit = s
|
||
|
|
if s >= sLimit {
|
||
|
|
break encodeLoop
|
||
|
|
}
|
||
|
|
cv = load6432(src, s)
|
||
|
|
|
||
|
|
// Check offset 2
|
||
|
|
if o2 := s - offset2; len(blk.sequences) > 2 && load3232(src, o2) == uint32(cv) {
|
||
|
|
// We have at least 4 byte match.
|
||
|
|
// No need to check backwards. We come straight from a match
|
||
|
|
//l := 4 + e.matchlenNoHist(s+4, o2+4, src)
|
||
|
|
// l := 4 + int32(matchLen(src[s+4:], src[o2+4:]))
|
||
|
|
var l int32
|
||
|
|
{
|
||
|
|
a := src[s+4:]
|
||
|
|
b := src[o2+4:]
|
||
|
|
endI := len(a) & (math.MaxInt32 - 7)
|
||
|
|
l = int32(endI) + 4
|
||
|
|
for i := 0; i < endI; i += 8 {
|
||
|
|
if diff := load64(a, i) ^ load64(b, i); diff != 0 {
|
||
|
|
l = int32(i+bits.TrailingZeros64(diff)>>3) + 4
|
||
|
|
break
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// Store this, since we have it.
|
||
|
|
nextHash := hash6(cv, hashLog)
|
||
|
|
e.table[nextHash] = tableEntry{offset: s + e.cur, val: uint32(cv)}
|
||
|
|
seq.matchLen = uint32(l) - zstdMinMatch
|
||
|
|
seq.litLen = 0
|
||
|
|
// Since litlen is always 0, this is offset 1.
|
||
|
|
seq.offset = 1
|
||
|
|
s += l
|
||
|
|
nextEmit = s
|
||
|
|
if debugSequences {
|
||
|
|
println("sequence", seq, "next s:", s)
|
||
|
|
}
|
||
|
|
blk.sequences = append(blk.sequences, seq)
|
||
|
|
|
||
|
|
// Swap offset 1 and 2.
|
||
|
|
offset1, offset2 = offset2, offset1
|
||
|
|
if s >= sLimit {
|
||
|
|
break encodeLoop
|
||
|
|
}
|
||
|
|
// Prepare next loop.
|
||
|
|
cv = load6432(src, s)
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
if int(nextEmit) < len(src) {
|
||
|
|
blk.literals = append(blk.literals, src[nextEmit:]...)
|
||
|
|
blk.extraLits = len(src) - int(nextEmit)
|
||
|
|
}
|
||
|
|
if debug {
|
||
|
|
println("returning, recent offsets:", blk.recentOffsets, "extra literals:", blk.extraLits)
|
||
|
|
}
|
||
|
|
// We do not store history, so we must offset e.cur to avoid false matches for next user.
|
||
|
|
if e.cur < bufferReset {
|
||
|
|
e.cur += int32(len(src))
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
// ResetDict will reset and set a dictionary if not nil
|
||
|
|
func (e *fastEncoder) Reset(d *dict, singleBlock bool) {
|
||
|
|
e.resetBase(d, singleBlock)
|
||
|
|
if d == nil {
|
||
|
|
return
|
||
|
|
}
|
||
|
|
|
||
|
|
// Init or copy dict table
|
||
|
|
if len(e.dictTable) != len(e.table) || d.id != e.lastDictID {
|
||
|
|
if len(e.dictTable) != len(e.table) {
|
||
|
|
e.dictTable = make([]tableEntry, len(e.table))
|
||
|
|
}
|
||
|
|
if true {
|
||
|
|
end := e.maxMatchOff + int32(len(d.content)) - 8
|
||
|
|
for i := e.maxMatchOff; i < end; i += 3 {
|
||
|
|
const hashLog = tableBits
|
||
|
|
|
||
|
|
cv := load6432(d.content, i-e.maxMatchOff)
|
||
|
|
nextHash := hash6(cv, hashLog) // 0 -> 5
|
||
|
|
nextHash1 := hash6(cv>>8, hashLog) // 1 -> 6
|
||
|
|
nextHash2 := hash6(cv>>16, hashLog) // 2 -> 7
|
||
|
|
e.dictTable[nextHash] = tableEntry{
|
||
|
|
val: uint32(cv),
|
||
|
|
offset: i,
|
||
|
|
}
|
||
|
|
e.dictTable[nextHash1] = tableEntry{
|
||
|
|
val: uint32(cv >> 8),
|
||
|
|
offset: i + 1,
|
||
|
|
}
|
||
|
|
e.dictTable[nextHash2] = tableEntry{
|
||
|
|
val: uint32(cv >> 16),
|
||
|
|
offset: i + 2,
|
||
|
|
}
|
||
|
|
}
|
||
|
|
}
|
||
|
|
e.lastDictID = d.id
|
||
|
|
}
|
||
|
|
|
||
|
|
e.cur = e.maxMatchOff
|
||
|
|
// Reset table to initial state
|
||
|
|
copy(e.table[:], e.dictTable)
|
||
|
|
}
|