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// Copyright 2019+ Klaus Post. All rights reserved.
// License information can be found in the LICENSE file.
// Based on work by Yann Collet, released under BSD License.
package zstd
type encParams struct {
// largest match distance : larger == more compression, more memory needed during decompression
windowLog uint8
// fully searched segment : larger == more compression, slower, more memory (useless for fast)
chainLog uint8
// dispatch table : larger == faster, more memory
hashLog uint8
// < nb of searches : larger == more compression, slower
searchLog uint8
// < match length searched : larger == faster decompression, sometimes less compression
minMatch uint8
// acceptable match size for optimal parser (only) : larger == more compression, slower
targetLength uint32
// see ZSTD_strategy definition above
strategy strategy
}
// strategy defines the algorithm to use when generating sequences.
type strategy uint8
const (
// Compression strategies, listed from fastest to strongest
strategyFast strategy = iota + 1
strategyDfast
strategyGreedy
strategyLazy
strategyLazy2
strategyBtlazy2
strategyBtopt
strategyBtultra
strategyBtultra2
// note : new strategies _might_ be added in the future.
// Only the order (from fast to strong) is guaranteed
)
var defEncParams = [4][]encParams{
{ // "default" - for any srcSize > 256 KB
// W, C, H, S, L, TL, strat
{19, 12, 13, 1, 6, 1, strategyFast}, // base for negative levels
{19, 13, 14, 1, 7, 0, strategyFast}, // level 1
{20, 15, 16, 1, 6, 0, strategyFast}, // level 2
{21, 16, 17, 1, 5, 1, strategyDfast}, // level 3
{21, 18, 18, 1, 5, 1, strategyDfast}, // level 4
{21, 18, 19, 2, 5, 2, strategyGreedy}, // level 5
{21, 19, 19, 3, 5, 4, strategyGreedy}, // level 6
{21, 19, 19, 3, 5, 8, strategyLazy}, // level 7
{21, 19, 19, 3, 5, 16, strategyLazy2}, // level 8
{21, 19, 20, 4, 5, 16, strategyLazy2}, // level 9
{22, 20, 21, 4, 5, 16, strategyLazy2}, // level 10
{22, 21, 22, 4, 5, 16, strategyLazy2}, // level 11
{22, 21, 22, 5, 5, 16, strategyLazy2}, // level 12
{22, 21, 22, 5, 5, 32, strategyBtlazy2}, // level 13
{22, 22, 23, 5, 5, 32, strategyBtlazy2}, // level 14
{22, 23, 23, 6, 5, 32, strategyBtlazy2}, // level 15
{22, 22, 22, 5, 5, 48, strategyBtopt}, // level 16
{23, 23, 22, 5, 4, 64, strategyBtopt}, // level 17
{23, 23, 22, 6, 3, 64, strategyBtultra}, // level 18
{23, 24, 22, 7, 3, 256, strategyBtultra2}, // level 19
{25, 25, 23, 7, 3, 256, strategyBtultra2}, // level 20
{26, 26, 24, 7, 3, 512, strategyBtultra2}, // level 21
{27, 27, 25, 9, 3, 999, strategyBtultra2}, // level 22
},
{ // for srcSize <= 256 KB
// W, C, H, S, L, T, strat
{18, 12, 13, 1, 5, 1, strategyFast}, // base for negative levels
{18, 13, 14, 1, 6, 0, strategyFast}, // level 1
{18, 14, 14, 1, 5, 1, strategyDfast}, // level 2
{18, 16, 16, 1, 4, 1, strategyDfast}, // level 3
{18, 16, 17, 2, 5, 2, strategyGreedy}, // level 4.
{18, 18, 18, 3, 5, 2, strategyGreedy}, // level 5.
{18, 18, 19, 3, 5, 4, strategyLazy}, // level 6.
{18, 18, 19, 4, 4, 4, strategyLazy}, // level 7
{18, 18, 19, 4, 4, 8, strategyLazy2}, // level 8
{18, 18, 19, 5, 4, 8, strategyLazy2}, // level 9
{18, 18, 19, 6, 4, 8, strategyLazy2}, // level 10
{18, 18, 19, 5, 4, 12, strategyBtlazy2}, // level 11.
{18, 19, 19, 7, 4, 12, strategyBtlazy2}, // level 12.
{18, 18, 19, 4, 4, 16, strategyBtopt}, // level 13
{18, 18, 19, 4, 3, 32, strategyBtopt}, // level 14.
{18, 18, 19, 6, 3, 128, strategyBtopt}, // level 15.
{18, 19, 19, 6, 3, 128, strategyBtultra}, // level 16.
{18, 19, 19, 8, 3, 256, strategyBtultra}, // level 17.
{18, 19, 19, 6, 3, 128, strategyBtultra2}, // level 18.
{18, 19, 19, 8, 3, 256, strategyBtultra2}, // level 19.
{18, 19, 19, 10, 3, 512, strategyBtultra2}, // level 20.
{18, 19, 19, 12, 3, 512, strategyBtultra2}, // level 21.
{18, 19, 19, 13, 3, 999, strategyBtultra2}, // level 22.
},
{ // for srcSize <= 128 KB
// W, C, H, S, L, T, strat
{17, 12, 12, 1, 5, 1, strategyFast}, // base for negative levels
{17, 12, 13, 1, 6, 0, strategyFast}, // level 1
{17, 13, 15, 1, 5, 0, strategyFast}, // level 2
{17, 15, 16, 2, 5, 1, strategyDfast}, // level 3
{17, 17, 17, 2, 4, 1, strategyDfast}, // level 4
{17, 16, 17, 3, 4, 2, strategyGreedy}, // level 5
{17, 17, 17, 3, 4, 4, strategyLazy}, // level 6
{17, 17, 17, 3, 4, 8, strategyLazy2}, // level 7
{17, 17, 17, 4, 4, 8, strategyLazy2}, // level 8
{17, 17, 17, 5, 4, 8, strategyLazy2}, // level 9
{17, 17, 17, 6, 4, 8, strategyLazy2}, // level 10
{17, 17, 17, 5, 4, 8, strategyBtlazy2}, // level 11
{17, 18, 17, 7, 4, 12, strategyBtlazy2}, // level 12
{17, 18, 17, 3, 4, 12, strategyBtopt}, // level 13.
{17, 18, 17, 4, 3, 32, strategyBtopt}, // level 14.
{17, 18, 17, 6, 3, 256, strategyBtopt}, // level 15.
{17, 18, 17, 6, 3, 128, strategyBtultra}, // level 16.
{17, 18, 17, 8, 3, 256, strategyBtultra}, // level 17.
{17, 18, 17, 10, 3, 512, strategyBtultra}, // level 18.
{17, 18, 17, 5, 3, 256, strategyBtultra2}, // level 19.
{17, 18, 17, 7, 3, 512, strategyBtultra2}, // level 20.
{17, 18, 17, 9, 3, 512, strategyBtultra2}, // level 21.
{17, 18, 17, 11, 3, 999, strategyBtultra2}, // level 22.
},
{ // for srcSize <= 16 KB
// W, C, H, S, L, T, strat
{14, 12, 13, 1, 5, 1, strategyFast}, // base for negative levels
{14, 14, 15, 1, 5, 0, strategyFast}, // level 1
{14, 14, 15, 1, 4, 0, strategyFast}, // level 2
{14, 14, 15, 2, 4, 1, strategyDfast}, // level 3
{14, 14, 14, 4, 4, 2, strategyGreedy}, // level 4
{14, 14, 14, 3, 4, 4, strategyLazy}, // level 5.
{14, 14, 14, 4, 4, 8, strategyLazy2}, // level 6
{14, 14, 14, 6, 4, 8, strategyLazy2}, // level 7
{14, 14, 14, 8, 4, 8, strategyLazy2}, // level 8.
{14, 15, 14, 5, 4, 8, strategyBtlazy2}, // level 9.
{14, 15, 14, 9, 4, 8, strategyBtlazy2}, // level 10.
{14, 15, 14, 3, 4, 12, strategyBtopt}, // level 11.
{14, 15, 14, 4, 3, 24, strategyBtopt}, // level 12.
{14, 15, 14, 5, 3, 32, strategyBtultra}, // level 13.
{14, 15, 15, 6, 3, 64, strategyBtultra}, // level 14.
{14, 15, 15, 7, 3, 256, strategyBtultra}, // level 15.
{14, 15, 15, 5, 3, 48, strategyBtultra2}, // level 16.
{14, 15, 15, 6, 3, 128, strategyBtultra2}, // level 17.
{14, 15, 15, 7, 3, 256, strategyBtultra2}, // level 18.
{14, 15, 15, 8, 3, 256, strategyBtultra2}, // level 19.
{14, 15, 15, 8, 3, 512, strategyBtultra2}, // level 20.
{14, 15, 15, 9, 3, 512, strategyBtultra2}, // level 21.
{14, 15, 15, 10, 3, 999, strategyBtultra2}, // level 22.
},
}
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