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Pragya Arya324337e2020-02-20 14:35:08 +05301// Copyright 2019+ Klaus Post. All rights reserved.
2// License information can be found in the LICENSE file.
3// Based on work by Yann Collet, released under BSD License.
4
5package zstd
6
7type encParams struct {
8 // largest match distance : larger == more compression, more memory needed during decompression
9 windowLog uint8
10
11 // fully searched segment : larger == more compression, slower, more memory (useless for fast)
12 chainLog uint8
13
14 // dispatch table : larger == faster, more memory
15 hashLog uint8
16
17 // < nb of searches : larger == more compression, slower
18 searchLog uint8
19
20 // < match length searched : larger == faster decompression, sometimes less compression
21 minMatch uint8
22
23 // acceptable match size for optimal parser (only) : larger == more compression, slower
24 targetLength uint32
25
26 // see ZSTD_strategy definition above
27 strategy strategy
28}
29
30// strategy defines the algorithm to use when generating sequences.
31type strategy uint8
32
33const (
34 // Compression strategies, listed from fastest to strongest
35 strategyFast strategy = iota + 1
36 strategyDfast
37 strategyGreedy
38 strategyLazy
39 strategyLazy2
40 strategyBtlazy2
41 strategyBtopt
42 strategyBtultra
43 strategyBtultra2
44 // note : new strategies _might_ be added in the future.
45 // Only the order (from fast to strong) is guaranteed
46
47)
48
49var defEncParams = [4][]encParams{
50 { // "default" - for any srcSize > 256 KB
51 // W, C, H, S, L, TL, strat
52 {19, 12, 13, 1, 6, 1, strategyFast}, // base for negative levels
53 {19, 13, 14, 1, 7, 0, strategyFast}, // level 1
54 {20, 15, 16, 1, 6, 0, strategyFast}, // level 2
55 {21, 16, 17, 1, 5, 1, strategyDfast}, // level 3
56 {21, 18, 18, 1, 5, 1, strategyDfast}, // level 4
57 {21, 18, 19, 2, 5, 2, strategyGreedy}, // level 5
58 {21, 19, 19, 3, 5, 4, strategyGreedy}, // level 6
59 {21, 19, 19, 3, 5, 8, strategyLazy}, // level 7
60 {21, 19, 19, 3, 5, 16, strategyLazy2}, // level 8
61 {21, 19, 20, 4, 5, 16, strategyLazy2}, // level 9
62 {22, 20, 21, 4, 5, 16, strategyLazy2}, // level 10
63 {22, 21, 22, 4, 5, 16, strategyLazy2}, // level 11
64 {22, 21, 22, 5, 5, 16, strategyLazy2}, // level 12
65 {22, 21, 22, 5, 5, 32, strategyBtlazy2}, // level 13
66 {22, 22, 23, 5, 5, 32, strategyBtlazy2}, // level 14
67 {22, 23, 23, 6, 5, 32, strategyBtlazy2}, // level 15
68 {22, 22, 22, 5, 5, 48, strategyBtopt}, // level 16
69 {23, 23, 22, 5, 4, 64, strategyBtopt}, // level 17
70 {23, 23, 22, 6, 3, 64, strategyBtultra}, // level 18
71 {23, 24, 22, 7, 3, 256, strategyBtultra2}, // level 19
72 {25, 25, 23, 7, 3, 256, strategyBtultra2}, // level 20
73 {26, 26, 24, 7, 3, 512, strategyBtultra2}, // level 21
74 {27, 27, 25, 9, 3, 999, strategyBtultra2}, // level 22
75 },
76 { // for srcSize <= 256 KB
77 // W, C, H, S, L, T, strat
78 {18, 12, 13, 1, 5, 1, strategyFast}, // base for negative levels
79 {18, 13, 14, 1, 6, 0, strategyFast}, // level 1
80 {18, 14, 14, 1, 5, 1, strategyDfast}, // level 2
81 {18, 16, 16, 1, 4, 1, strategyDfast}, // level 3
82 {18, 16, 17, 2, 5, 2, strategyGreedy}, // level 4.
83 {18, 18, 18, 3, 5, 2, strategyGreedy}, // level 5.
84 {18, 18, 19, 3, 5, 4, strategyLazy}, // level 6.
85 {18, 18, 19, 4, 4, 4, strategyLazy}, // level 7
86 {18, 18, 19, 4, 4, 8, strategyLazy2}, // level 8
87 {18, 18, 19, 5, 4, 8, strategyLazy2}, // level 9
88 {18, 18, 19, 6, 4, 8, strategyLazy2}, // level 10
89 {18, 18, 19, 5, 4, 12, strategyBtlazy2}, // level 11.
90 {18, 19, 19, 7, 4, 12, strategyBtlazy2}, // level 12.
91 {18, 18, 19, 4, 4, 16, strategyBtopt}, // level 13
92 {18, 18, 19, 4, 3, 32, strategyBtopt}, // level 14.
93 {18, 18, 19, 6, 3, 128, strategyBtopt}, // level 15.
94 {18, 19, 19, 6, 3, 128, strategyBtultra}, // level 16.
95 {18, 19, 19, 8, 3, 256, strategyBtultra}, // level 17.
96 {18, 19, 19, 6, 3, 128, strategyBtultra2}, // level 18.
97 {18, 19, 19, 8, 3, 256, strategyBtultra2}, // level 19.
98 {18, 19, 19, 10, 3, 512, strategyBtultra2}, // level 20.
99 {18, 19, 19, 12, 3, 512, strategyBtultra2}, // level 21.
100 {18, 19, 19, 13, 3, 999, strategyBtultra2}, // level 22.
101 },
102 { // for srcSize <= 128 KB
103 // W, C, H, S, L, T, strat
104 {17, 12, 12, 1, 5, 1, strategyFast}, // base for negative levels
105 {17, 12, 13, 1, 6, 0, strategyFast}, // level 1
106 {17, 13, 15, 1, 5, 0, strategyFast}, // level 2
107 {17, 15, 16, 2, 5, 1, strategyDfast}, // level 3
108 {17, 17, 17, 2, 4, 1, strategyDfast}, // level 4
109 {17, 16, 17, 3, 4, 2, strategyGreedy}, // level 5
110 {17, 17, 17, 3, 4, 4, strategyLazy}, // level 6
111 {17, 17, 17, 3, 4, 8, strategyLazy2}, // level 7
112 {17, 17, 17, 4, 4, 8, strategyLazy2}, // level 8
113 {17, 17, 17, 5, 4, 8, strategyLazy2}, // level 9
114 {17, 17, 17, 6, 4, 8, strategyLazy2}, // level 10
115 {17, 17, 17, 5, 4, 8, strategyBtlazy2}, // level 11
116 {17, 18, 17, 7, 4, 12, strategyBtlazy2}, // level 12
117 {17, 18, 17, 3, 4, 12, strategyBtopt}, // level 13.
118 {17, 18, 17, 4, 3, 32, strategyBtopt}, // level 14.
119 {17, 18, 17, 6, 3, 256, strategyBtopt}, // level 15.
120 {17, 18, 17, 6, 3, 128, strategyBtultra}, // level 16.
121 {17, 18, 17, 8, 3, 256, strategyBtultra}, // level 17.
122 {17, 18, 17, 10, 3, 512, strategyBtultra}, // level 18.
123 {17, 18, 17, 5, 3, 256, strategyBtultra2}, // level 19.
124 {17, 18, 17, 7, 3, 512, strategyBtultra2}, // level 20.
125 {17, 18, 17, 9, 3, 512, strategyBtultra2}, // level 21.
126 {17, 18, 17, 11, 3, 999, strategyBtultra2}, // level 22.
127 },
128 { // for srcSize <= 16 KB
129 // W, C, H, S, L, T, strat
130 {14, 12, 13, 1, 5, 1, strategyFast}, // base for negative levels
131 {14, 14, 15, 1, 5, 0, strategyFast}, // level 1
132 {14, 14, 15, 1, 4, 0, strategyFast}, // level 2
133 {14, 14, 15, 2, 4, 1, strategyDfast}, // level 3
134 {14, 14, 14, 4, 4, 2, strategyGreedy}, // level 4
135 {14, 14, 14, 3, 4, 4, strategyLazy}, // level 5.
136 {14, 14, 14, 4, 4, 8, strategyLazy2}, // level 6
137 {14, 14, 14, 6, 4, 8, strategyLazy2}, // level 7
138 {14, 14, 14, 8, 4, 8, strategyLazy2}, // level 8.
139 {14, 15, 14, 5, 4, 8, strategyBtlazy2}, // level 9.
140 {14, 15, 14, 9, 4, 8, strategyBtlazy2}, // level 10.
141 {14, 15, 14, 3, 4, 12, strategyBtopt}, // level 11.
142 {14, 15, 14, 4, 3, 24, strategyBtopt}, // level 12.
143 {14, 15, 14, 5, 3, 32, strategyBtultra}, // level 13.
144 {14, 15, 15, 6, 3, 64, strategyBtultra}, // level 14.
145 {14, 15, 15, 7, 3, 256, strategyBtultra}, // level 15.
146 {14, 15, 15, 5, 3, 48, strategyBtultra2}, // level 16.
147 {14, 15, 15, 6, 3, 128, strategyBtultra2}, // level 17.
148 {14, 15, 15, 7, 3, 256, strategyBtultra2}, // level 18.
149 {14, 15, 15, 8, 3, 256, strategyBtultra2}, // level 19.
150 {14, 15, 15, 8, 3, 512, strategyBtultra2}, // level 20.
151 {14, 15, 15, 9, 3, 512, strategyBtultra2}, // level 21.
152 {14, 15, 15, 10, 3, 999, strategyBtultra2}, // level 22.
153 },
154}