1 /* Copyright 2013 Google Inc. All Rights Reserved.
2
3 Distributed under MIT license.
4 See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
5 */
6
7 /* Block split point selection utilities. */
8
9 #include "./block_splitter.h"
10
11 #include <assert.h>
12 #include <string.h> /* memcpy, memset */
13
14 #include "./bit_cost.h"
15 #include "./cluster.h"
16 #include "./command.h"
17 #include "./fast_log.h"
18 #include "./histogram.h"
19 #include "./memory.h"
20 #include "./port.h"
21 #include "./quality.h"
22
23 #if defined(__cplusplus) || defined(c_plusplus)
24 extern "C" {
25 #endif
26
27 static const size_t kMaxLiteralHistograms = 100;
28 static const size_t kMaxCommandHistograms = 50;
29 static const double kLiteralBlockSwitchCost = 28.1;
30 static const double kCommandBlockSwitchCost = 13.5;
31 static const double kDistanceBlockSwitchCost = 14.6;
32 static const size_t kLiteralStrideLength = 70;
33 static const size_t kCommandStrideLength = 40;
34 static const size_t kSymbolsPerLiteralHistogram = 544;
35 static const size_t kSymbolsPerCommandHistogram = 530;
36 static const size_t kSymbolsPerDistanceHistogram = 544;
37 static const size_t kMinLengthForBlockSplitting = 128;
38 static const size_t kIterMulForRefining = 2;
39 static const size_t kMinItersForRefining = 100;
40
CountLiterals(const Command * cmds,const size_t num_commands)41 static size_t CountLiterals(const Command* cmds, const size_t num_commands) {
42 /* Count how many we have. */
43 size_t total_length = 0;
44 size_t i;
45 for (i = 0; i < num_commands; ++i) {
46 total_length += cmds[i].insert_len_;
47 }
48 return total_length;
49 }
50
CopyLiteralsToByteArray(const Command * cmds,const size_t num_commands,const uint8_t * data,const size_t offset,const size_t mask,uint8_t * literals)51 static void CopyLiteralsToByteArray(const Command* cmds,
52 const size_t num_commands,
53 const uint8_t* data,
54 const size_t offset,
55 const size_t mask,
56 uint8_t* literals) {
57 size_t pos = 0;
58 size_t from_pos = offset & mask;
59 size_t i;
60 for (i = 0; i < num_commands; ++i) {
61 size_t insert_len = cmds[i].insert_len_;
62 if (from_pos + insert_len > mask) {
63 size_t head_size = mask + 1 - from_pos;
64 memcpy(literals + pos, data + from_pos, head_size);
65 from_pos = 0;
66 pos += head_size;
67 insert_len -= head_size;
68 }
69 if (insert_len > 0) {
70 memcpy(literals + pos, data + from_pos, insert_len);
71 pos += insert_len;
72 }
73 from_pos = (from_pos + insert_len + CommandCopyLen(&cmds[i])) & mask;
74 }
75 }
76
MyRand(uint32_t * seed)77 static BROTLI_INLINE uint32_t MyRand(uint32_t* seed) {
78 /* Initial seed should be 7. In this case, loop length is (1 << 29). */
79 *seed *= 16807U;
80 return *seed;
81 }
82
BitCost(size_t count)83 static BROTLI_INLINE double BitCost(size_t count) {
84 return count == 0 ? -2.0 : FastLog2(count);
85 }
86
87 #define HISTOGRAMS_PER_BATCH 64
88 #define CLUSTERS_PER_BATCH 16
89
90 #define FN(X) X ## Literal
91 #define DataType uint8_t
92 /* NOLINTNEXTLINE(build/include) */
93 #include "./block_splitter_inc.h"
94 #undef DataType
95 #undef FN
96
97 #define FN(X) X ## Command
98 #define DataType uint16_t
99 /* NOLINTNEXTLINE(build/include) */
100 #include "./block_splitter_inc.h"
101 #undef FN
102
103 #define FN(X) X ## Distance
104 /* NOLINTNEXTLINE(build/include) */
105 #include "./block_splitter_inc.h"
106 #undef DataType
107 #undef FN
108
BrotliInitBlockSplit(BlockSplit * self)109 void BrotliInitBlockSplit(BlockSplit* self) {
110 self->num_types = 0;
111 self->num_blocks = 0;
112 self->types = 0;
113 self->lengths = 0;
114 self->types_alloc_size = 0;
115 self->lengths_alloc_size = 0;
116 }
117
BrotliDestroyBlockSplit(MemoryManager * m,BlockSplit * self)118 void BrotliDestroyBlockSplit(MemoryManager* m, BlockSplit* self) {
119 BROTLI_FREE(m, self->types);
120 BROTLI_FREE(m, self->lengths);
121 }
122
BrotliSplitBlock(MemoryManager * m,const Command * cmds,const size_t num_commands,const uint8_t * data,const size_t pos,const size_t mask,const BrotliEncoderParams * params,BlockSplit * literal_split,BlockSplit * insert_and_copy_split,BlockSplit * dist_split)123 void BrotliSplitBlock(MemoryManager* m,
124 const Command* cmds,
125 const size_t num_commands,
126 const uint8_t* data,
127 const size_t pos,
128 const size_t mask,
129 const BrotliEncoderParams* params,
130 BlockSplit* literal_split,
131 BlockSplit* insert_and_copy_split,
132 BlockSplit* dist_split) {
133 {
134 size_t literals_count = CountLiterals(cmds, num_commands);
135 uint8_t* literals = BROTLI_ALLOC(m, uint8_t, literals_count);
136 if (BROTLI_IS_OOM(m)) return;
137 /* Create a continuous array of literals. */
138 CopyLiteralsToByteArray(cmds, num_commands, data, pos, mask, literals);
139 /* Create the block split on the array of literals.
140 Literal histograms have alphabet size 256. */
141 SplitByteVectorLiteral(
142 m, literals, literals_count,
143 kSymbolsPerLiteralHistogram, kMaxLiteralHistograms,
144 kLiteralStrideLength, kLiteralBlockSwitchCost, params,
145 literal_split);
146 if (BROTLI_IS_OOM(m)) return;
147 BROTLI_FREE(m, literals);
148 }
149
150 {
151 /* Compute prefix codes for commands. */
152 uint16_t* insert_and_copy_codes = BROTLI_ALLOC(m, uint16_t, num_commands);
153 size_t i;
154 if (BROTLI_IS_OOM(m)) return;
155 for (i = 0; i < num_commands; ++i) {
156 insert_and_copy_codes[i] = cmds[i].cmd_prefix_;
157 }
158 /* Create the block split on the array of command prefixes. */
159 SplitByteVectorCommand(
160 m, insert_and_copy_codes, num_commands,
161 kSymbolsPerCommandHistogram, kMaxCommandHistograms,
162 kCommandStrideLength, kCommandBlockSwitchCost, params,
163 insert_and_copy_split);
164 if (BROTLI_IS_OOM(m)) return;
165 /* TODO: reuse for distances? */
166 BROTLI_FREE(m, insert_and_copy_codes);
167 }
168
169 {
170 /* Create a continuous array of distance prefixes. */
171 uint16_t* distance_prefixes = BROTLI_ALLOC(m, uint16_t, num_commands);
172 size_t j = 0;
173 size_t i;
174 if (BROTLI_IS_OOM(m)) return;
175 for (i = 0; i < num_commands; ++i) {
176 const Command* cmd = &cmds[i];
177 if (CommandCopyLen(cmd) && cmd->cmd_prefix_ >= 128) {
178 distance_prefixes[j++] = cmd->dist_prefix_;
179 }
180 }
181 /* Create the block split on the array of distance prefixes. */
182 SplitByteVectorDistance(
183 m, distance_prefixes, j,
184 kSymbolsPerDistanceHistogram, kMaxCommandHistograms,
185 kCommandStrideLength, kDistanceBlockSwitchCost, params,
186 dist_split);
187 if (BROTLI_IS_OOM(m)) return;
188 BROTLI_FREE(m, distance_prefixes);
189 }
190 }
191
192
193 #if defined(__cplusplus) || defined(c_plusplus)
194 } /* extern "C" */
195 #endif
196