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146 lines
3.3 KiB
146 lines
3.3 KiB
// Copyright 2014-2021 Ulrich Kunitz. 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 lzma
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// states defines the overall state count
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const states = 12
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// State maintains the full state of the operation encoding or decoding
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// process.
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type state struct {
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rep [4]uint32
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isMatch [states << maxPosBits]prob
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isRepG0Long [states << maxPosBits]prob
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isRep [states]prob
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isRepG0 [states]prob
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isRepG1 [states]prob
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isRepG2 [states]prob
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litCodec literalCodec
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lenCodec lengthCodec
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repLenCodec lengthCodec
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distCodec distCodec
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state uint32
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posBitMask uint32
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Properties Properties
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}
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// initProbSlice initializes a slice of probabilities.
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func initProbSlice(p []prob) {
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for i := range p {
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p[i] = probInit
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}
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}
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// Reset sets all state information to the original values.
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func (s *state) Reset() {
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p := s.Properties
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*s = state{
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Properties: p,
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// dict: s.dict,
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posBitMask: (uint32(1) << uint(p.PB)) - 1,
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}
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initProbSlice(s.isMatch[:])
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initProbSlice(s.isRep[:])
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initProbSlice(s.isRepG0[:])
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initProbSlice(s.isRepG1[:])
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initProbSlice(s.isRepG2[:])
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initProbSlice(s.isRepG0Long[:])
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s.litCodec.init(p.LC, p.LP)
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s.lenCodec.init()
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s.repLenCodec.init()
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s.distCodec.init()
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}
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// newState creates a new state from the give Properties.
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func newState(p Properties) *state {
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s := &state{Properties: p}
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s.Reset()
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return s
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}
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// deepcopy initializes s as a deep copy of the source.
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func (s *state) deepcopy(src *state) {
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if s == src {
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return
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}
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s.rep = src.rep
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s.isMatch = src.isMatch
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s.isRepG0Long = src.isRepG0Long
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s.isRep = src.isRep
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s.isRepG0 = src.isRepG0
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s.isRepG1 = src.isRepG1
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s.isRepG2 = src.isRepG2
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s.litCodec.deepcopy(&src.litCodec)
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s.lenCodec.deepcopy(&src.lenCodec)
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s.repLenCodec.deepcopy(&src.repLenCodec)
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s.distCodec.deepcopy(&src.distCodec)
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s.state = src.state
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s.posBitMask = src.posBitMask
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s.Properties = src.Properties
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}
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// cloneState creates a new clone of the give state.
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func cloneState(src *state) *state {
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s := new(state)
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s.deepcopy(src)
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return s
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}
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// updateStateLiteral updates the state for a literal.
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func (s *state) updateStateLiteral() {
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switch {
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case s.state < 4:
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s.state = 0
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return
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case s.state < 10:
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s.state -= 3
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return
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}
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s.state -= 6
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}
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// updateStateMatch updates the state for a match.
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func (s *state) updateStateMatch() {
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if s.state < 7 {
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s.state = 7
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} else {
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s.state = 10
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}
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}
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// updateStateRep updates the state for a repetition.
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func (s *state) updateStateRep() {
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if s.state < 7 {
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s.state = 8
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} else {
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s.state = 11
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}
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}
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// updateStateShortRep updates the state for a short repetition.
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func (s *state) updateStateShortRep() {
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if s.state < 7 {
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s.state = 9
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} else {
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s.state = 11
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}
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}
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// states computes the states of the operation codec.
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func (s *state) states(dictHead int64) (state1, state2, posState uint32) {
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state1 = s.state
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posState = uint32(dictHead) & s.posBitMask
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state2 = (s.state << maxPosBits) | posState
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return
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}
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// litState computes the literal state.
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func (s *state) litState(prev byte, dictHead int64) uint32 {
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lp, lc := uint(s.Properties.LP), uint(s.Properties.LC)
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litState := ((uint32(dictHead) & ((1 << lp) - 1)) << lc) |
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(uint32(prev) >> (8 - lc))
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return litState
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}
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