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155 lines
6.9 KiB
Go
155 lines
6.9 KiB
Go
// 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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type encParams struct {
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// largest match distance : larger == more compression, more memory needed during decompression
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windowLog uint8
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// fully searched segment : larger == more compression, slower, more memory (useless for fast)
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chainLog uint8
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// dispatch table : larger == faster, more memory
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hashLog uint8
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// < nb of searches : larger == more compression, slower
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searchLog uint8
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// < match length searched : larger == faster decompression, sometimes less compression
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minMatch uint8
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// acceptable match size for optimal parser (only) : larger == more compression, slower
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targetLength uint32
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// see ZSTD_strategy definition above
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strategy strategy
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}
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// strategy defines the algorithm to use when generating sequences.
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type strategy uint8
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const (
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// Compression strategies, listed from fastest to strongest
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strategyFast strategy = iota + 1
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strategyDfast
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strategyGreedy
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strategyLazy
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strategyLazy2
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strategyBtlazy2
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strategyBtopt
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strategyBtultra
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strategyBtultra2
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// note : new strategies _might_ be added in the future.
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// Only the order (from fast to strong) is guaranteed
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)
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var defEncParams = [4][]encParams{
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{ // "default" - for any srcSize > 256 KB
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// W, C, H, S, L, TL, strat
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{19, 12, 13, 1, 6, 1, strategyFast}, // base for negative levels
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{19, 13, 14, 1, 7, 0, strategyFast}, // level 1
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{20, 15, 16, 1, 6, 0, strategyFast}, // level 2
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{21, 16, 17, 1, 5, 1, strategyDfast}, // level 3
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{21, 18, 18, 1, 5, 1, strategyDfast}, // level 4
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{21, 18, 19, 2, 5, 2, strategyGreedy}, // level 5
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{21, 19, 19, 3, 5, 4, strategyGreedy}, // level 6
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{21, 19, 19, 3, 5, 8, strategyLazy}, // level 7
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{21, 19, 19, 3, 5, 16, strategyLazy2}, // level 8
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{21, 19, 20, 4, 5, 16, strategyLazy2}, // level 9
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{22, 20, 21, 4, 5, 16, strategyLazy2}, // level 10
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{22, 21, 22, 4, 5, 16, strategyLazy2}, // level 11
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{22, 21, 22, 5, 5, 16, strategyLazy2}, // level 12
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{22, 21, 22, 5, 5, 32, strategyBtlazy2}, // level 13
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{22, 22, 23, 5, 5, 32, strategyBtlazy2}, // level 14
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{22, 23, 23, 6, 5, 32, strategyBtlazy2}, // level 15
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{22, 22, 22, 5, 5, 48, strategyBtopt}, // level 16
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{23, 23, 22, 5, 4, 64, strategyBtopt}, // level 17
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{23, 23, 22, 6, 3, 64, strategyBtultra}, // level 18
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{23, 24, 22, 7, 3, 256, strategyBtultra2}, // level 19
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{25, 25, 23, 7, 3, 256, strategyBtultra2}, // level 20
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{26, 26, 24, 7, 3, 512, strategyBtultra2}, // level 21
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{27, 27, 25, 9, 3, 999, strategyBtultra2}, // level 22
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},
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{ // for srcSize <= 256 KB
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// W, C, H, S, L, T, strat
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{18, 12, 13, 1, 5, 1, strategyFast}, // base for negative levels
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{18, 13, 14, 1, 6, 0, strategyFast}, // level 1
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{18, 14, 14, 1, 5, 1, strategyDfast}, // level 2
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{18, 16, 16, 1, 4, 1, strategyDfast}, // level 3
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{18, 16, 17, 2, 5, 2, strategyGreedy}, // level 4.
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{18, 18, 18, 3, 5, 2, strategyGreedy}, // level 5.
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{18, 18, 19, 3, 5, 4, strategyLazy}, // level 6.
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{18, 18, 19, 4, 4, 4, strategyLazy}, // level 7
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{18, 18, 19, 4, 4, 8, strategyLazy2}, // level 8
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{18, 18, 19, 5, 4, 8, strategyLazy2}, // level 9
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{18, 18, 19, 6, 4, 8, strategyLazy2}, // level 10
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{18, 18, 19, 5, 4, 12, strategyBtlazy2}, // level 11.
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{18, 19, 19, 7, 4, 12, strategyBtlazy2}, // level 12.
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{18, 18, 19, 4, 4, 16, strategyBtopt}, // level 13
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{18, 18, 19, 4, 3, 32, strategyBtopt}, // level 14.
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{18, 18, 19, 6, 3, 128, strategyBtopt}, // level 15.
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{18, 19, 19, 6, 3, 128, strategyBtultra}, // level 16.
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{18, 19, 19, 8, 3, 256, strategyBtultra}, // level 17.
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{18, 19, 19, 6, 3, 128, strategyBtultra2}, // level 18.
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{18, 19, 19, 8, 3, 256, strategyBtultra2}, // level 19.
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{18, 19, 19, 10, 3, 512, strategyBtultra2}, // level 20.
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{18, 19, 19, 12, 3, 512, strategyBtultra2}, // level 21.
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{18, 19, 19, 13, 3, 999, strategyBtultra2}, // level 22.
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},
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{ // for srcSize <= 128 KB
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// W, C, H, S, L, T, strat
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{17, 12, 12, 1, 5, 1, strategyFast}, // base for negative levels
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{17, 12, 13, 1, 6, 0, strategyFast}, // level 1
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{17, 13, 15, 1, 5, 0, strategyFast}, // level 2
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{17, 15, 16, 2, 5, 1, strategyDfast}, // level 3
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{17, 17, 17, 2, 4, 1, strategyDfast}, // level 4
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{17, 16, 17, 3, 4, 2, strategyGreedy}, // level 5
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{17, 17, 17, 3, 4, 4, strategyLazy}, // level 6
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{17, 17, 17, 3, 4, 8, strategyLazy2}, // level 7
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{17, 17, 17, 4, 4, 8, strategyLazy2}, // level 8
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{17, 17, 17, 5, 4, 8, strategyLazy2}, // level 9
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{17, 17, 17, 6, 4, 8, strategyLazy2}, // level 10
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{17, 17, 17, 5, 4, 8, strategyBtlazy2}, // level 11
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{17, 18, 17, 7, 4, 12, strategyBtlazy2}, // level 12
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{17, 18, 17, 3, 4, 12, strategyBtopt}, // level 13.
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{17, 18, 17, 4, 3, 32, strategyBtopt}, // level 14.
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{17, 18, 17, 6, 3, 256, strategyBtopt}, // level 15.
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{17, 18, 17, 6, 3, 128, strategyBtultra}, // level 16.
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{17, 18, 17, 8, 3, 256, strategyBtultra}, // level 17.
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{17, 18, 17, 10, 3, 512, strategyBtultra}, // level 18.
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{17, 18, 17, 5, 3, 256, strategyBtultra2}, // level 19.
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{17, 18, 17, 7, 3, 512, strategyBtultra2}, // level 20.
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{17, 18, 17, 9, 3, 512, strategyBtultra2}, // level 21.
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{17, 18, 17, 11, 3, 999, strategyBtultra2}, // level 22.
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},
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{ // for srcSize <= 16 KB
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// W, C, H, S, L, T, strat
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{14, 12, 13, 1, 5, 1, strategyFast}, // base for negative levels
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{14, 14, 15, 1, 5, 0, strategyFast}, // level 1
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{14, 14, 15, 1, 4, 0, strategyFast}, // level 2
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{14, 14, 15, 2, 4, 1, strategyDfast}, // level 3
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{14, 14, 14, 4, 4, 2, strategyGreedy}, // level 4
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{14, 14, 14, 3, 4, 4, strategyLazy}, // level 5.
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{14, 14, 14, 4, 4, 8, strategyLazy2}, // level 6
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{14, 14, 14, 6, 4, 8, strategyLazy2}, // level 7
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{14, 14, 14, 8, 4, 8, strategyLazy2}, // level 8.
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{14, 15, 14, 5, 4, 8, strategyBtlazy2}, // level 9.
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{14, 15, 14, 9, 4, 8, strategyBtlazy2}, // level 10.
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{14, 15, 14, 3, 4, 12, strategyBtopt}, // level 11.
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{14, 15, 14, 4, 3, 24, strategyBtopt}, // level 12.
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{14, 15, 14, 5, 3, 32, strategyBtultra}, // level 13.
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{14, 15, 15, 6, 3, 64, strategyBtultra}, // level 14.
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{14, 15, 15, 7, 3, 256, strategyBtultra}, // level 15.
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{14, 15, 15, 5, 3, 48, strategyBtultra2}, // level 16.
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{14, 15, 15, 6, 3, 128, strategyBtultra2}, // level 17.
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{14, 15, 15, 7, 3, 256, strategyBtultra2}, // level 18.
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{14, 15, 15, 8, 3, 256, strategyBtultra2}, // level 19.
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{14, 15, 15, 8, 3, 512, strategyBtultra2}, // level 20.
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{14, 15, 15, 9, 3, 512, strategyBtultra2}, // level 21.
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{14, 15, 15, 10, 3, 999, strategyBtultra2}, // level 22.
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},
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}
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