mirror of
https://github.com/aptly-dev/aptly.git
synced 2026-05-06 22:18:28 +00:00
Andrey Smirnov
127 lines
3.3 KiB
Go
127 lines
3.3 KiB
Go
// Copyright (c) 2010, Andrei Vieru. 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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type lenCoder struct {
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choice []uint16
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lowCoder []*rangeBitTreeCoder
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midCoder []*rangeBitTreeCoder
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highCoder *rangeBitTreeCoder
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}
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func newLenCoder(numPosStates /*1 << pb*/ uint32) *lenCoder {
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lc := &lenCoder{
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choice: initBitModels(2),
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lowCoder: make([]*rangeBitTreeCoder, kNumPosStatesMax),
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midCoder: make([]*rangeBitTreeCoder, kNumPosStatesMax),
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highCoder: newRangeBitTreeCoder(kNumHighLenBits),
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}
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for i := uint32(0); i < numPosStates; i++ {
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lc.lowCoder[i] = newRangeBitTreeCoder(kNumLowLenBits)
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lc.midCoder[i] = newRangeBitTreeCoder(kNumMidLenBits)
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}
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return lc
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}
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func (lc *lenCoder) decode(rd *rangeDecoder, posState uint32) (res uint32) {
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i := rd.decodeBit(lc.choice, 0)
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if i == 0 {
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res = lc.lowCoder[posState].decode(rd)
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return
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}
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res = kNumLowLenSymbols
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j := rd.decodeBit(lc.choice, 1)
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if j == 0 {
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k := lc.midCoder[posState].decode(rd)
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res += k
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return
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} else {
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l := lc.highCoder.decode(rd)
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res = res + kNumMidLenSymbols + l
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return
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}
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return
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}
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func (lc *lenCoder) encode(re *rangeEncoder, symbol, posState uint32) {
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if symbol < kNumLowLenSymbols {
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re.encode(lc.choice, 0, 0)
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lc.lowCoder[posState].encode(re, symbol)
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} else {
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symbol -= kNumLowLenSymbols
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re.encode(lc.choice, 0, 1)
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if symbol < kNumMidLenSymbols {
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re.encode(lc.choice, 1, 0)
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lc.midCoder[posState].encode(re, symbol)
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} else {
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re.encode(lc.choice, 1, 1)
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lc.highCoder.encode(re, symbol-kNumMidLenSymbols)
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}
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}
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}
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// write prices into prices []uint32
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func (lc *lenCoder) setPrices(prices []uint32, posState, numSymbols, st uint32) {
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a0 := getPrice0(lc.choice[0])
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a1 := getPrice1(lc.choice[0])
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b0 := a1 + getPrice0(lc.choice[1])
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b1 := a1 + getPrice1(lc.choice[1])
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var i uint32
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for i = 0; i < kNumLowLenSymbols; i++ {
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if i >= numSymbols {
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return
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}
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prices[st+i] = a0 + lc.lowCoder[posState].getPrice(i)
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}
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for ; i < kNumLowLenSymbols+kNumMidLenSymbols; i++ {
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if i >= numSymbols {
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return
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}
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prices[st+i] = b0 + lc.midCoder[posState].getPrice(i-kNumLowLenSymbols)
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}
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for ; i < numSymbols; i++ {
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prices[st+i] = b1 + lc.highCoder.getPrice(i-kNumLowLenSymbols-kNumMidLenSymbols)
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}
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}
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type lenPriceTableCoder struct {
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lc *lenCoder
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prices []uint32
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counters []uint32
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tableSize uint32
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}
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func newLenPriceTableCoder(tableSize, numPosStates uint32) *lenPriceTableCoder {
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pc := &lenPriceTableCoder{
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lc: newLenCoder(numPosStates),
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prices: make([]uint32, kNumLenSymbols<<kNumPosStatesBitsMax),
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counters: make([]uint32, kNumPosStatesMax),
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tableSize: tableSize,
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}
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for posState := uint32(0); posState < numPosStates; posState++ {
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pc.updateTable(posState)
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}
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return pc
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}
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func (pc *lenPriceTableCoder) updateTable(posState uint32) {
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pc.lc.setPrices(pc.prices, posState, pc.tableSize, posState*kNumLenSymbols)
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pc.counters[posState] = pc.tableSize
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}
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func (pc *lenPriceTableCoder) getPrice(symbol, posState uint32) uint32 {
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return pc.prices[posState*kNumLenSymbols+symbol]
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}
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func (pc *lenPriceTableCoder) encode(re *rangeEncoder, symbol, posState uint32) {
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pc.lc.encode(re, symbol, posState)
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pc.counters[posState]--
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if pc.counters[posState] == 0 {
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pc.updateTable(posState)
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}
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}
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