| // 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. |
| }, |
| } |