mirror of
https://github.com/aptly-dev/aptly.git
synced 2026-05-06 22:18:28 +00:00
118 lines
2.8 KiB
Go
118 lines
2.8 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 rangeBitTreeCoder struct {
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models []uint16 // length(models) is at most 1<<8
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numBitLevels uint32 // min 2; max 8
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}
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func newRangeBitTreeCoder(numBitLevels uint32) *rangeBitTreeCoder {
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return &rangeBitTreeCoder{
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numBitLevels: numBitLevels,
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models: initBitModels(1 << numBitLevels),
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}
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}
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func (rc *rangeBitTreeCoder) decode(rd *rangeDecoder) (res uint32) {
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res = 1
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for bitIndex := rc.numBitLevels; bitIndex != 0; bitIndex-- {
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bit := rd.decodeBit(rc.models, res)
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res = res<<1 + bit
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}
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res -= 1 << rc.numBitLevels
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return
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}
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func (rc *rangeBitTreeCoder) reverseDecode(rd *rangeDecoder) (res uint32) {
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index := uint32(1)
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res = 0
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for bitIndex := uint32(0); bitIndex < rc.numBitLevels; bitIndex++ {
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bit := rd.decodeBit(rc.models, index)
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index <<= 1
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index += bit
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res |= bit << bitIndex
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}
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return
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}
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func reverseDecodeIndex(rd *rangeDecoder, models []uint16, startIndex, numBitModels uint32) (res uint32) {
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index := uint32(1)
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res = 0
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for bitIndex := uint32(0); bitIndex < numBitModels; bitIndex++ {
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bit := rd.decodeBit(models, startIndex+index)
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index <<= 1
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index += bit
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res |= bit << bitIndex
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}
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return
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}
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func (rc *rangeBitTreeCoder) encode(re *rangeEncoder, symbol uint32) {
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m := uint32(1)
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for bitIndex := rc.numBitLevels; bitIndex != 0; {
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bitIndex--
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bit := (symbol >> bitIndex) & 1
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re.encode(rc.models, m, bit)
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m = m<<1 | bit
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}
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}
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func (rc *rangeBitTreeCoder) reverseEncode(re *rangeEncoder, symbol uint32) {
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m := uint32(1)
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for i := uint32(0); i < rc.numBitLevels; i++ {
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bit := symbol & 1
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re.encode(rc.models, m, bit)
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m = m<<1 | bit
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symbol >>= 1
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}
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}
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func (rc *rangeBitTreeCoder) getPrice(symbol uint32) (res uint32) {
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res = 0
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m := uint32(1)
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for bitIndex := rc.numBitLevels; bitIndex != 0; {
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bitIndex--
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bit := (symbol >> bitIndex) & 1
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res += getPrice(rc.models[m], bit)
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m = m<<1 + bit
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}
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return
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}
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func (rc *rangeBitTreeCoder) reverseGetPrice(symbol uint32) (res uint32) {
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res = 0
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m := uint32(1)
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for i := rc.numBitLevels; i != 0; i-- {
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bit := symbol & 1
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symbol >>= 1
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res += getPrice(rc.models[m], bit)
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m = m<<1 | bit
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}
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return
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}
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func reverseGetPriceIndex(models []uint16, startIndex, numBitLevels, symbol uint32) (res uint32) {
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res = 0
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m := uint32(1)
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for i := numBitLevels; i != 0; i-- {
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bit := symbol & 1
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symbol >>= 1
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res += getPrice(models[startIndex+m], bit)
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m = m<<1 | bit
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}
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return
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}
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func reverseEncodeIndex(re *rangeEncoder, models []uint16, startIndex, numBitLevels, symbol uint32) {
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m := uint32(1)
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for i := uint32(0); i < numBitLevels; i++ {
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bit := symbol & 1
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re.encode(models, startIndex+m, bit)
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m = m<<1 | bit
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symbol >>= 1
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}
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}
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