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 <string.h> /* memcpy, memset */
12
13#include "../common/platform.h"
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 "./quality.h"
21
22#if defined(__cplusplus) || defined(c_plusplus)
23extern "C" {
24#endif
25
26static const size_t kMaxLiteralHistograms = 100;
27static const size_t kMaxCommandHistograms = 50;
28static const double kLiteralBlockSwitchCost = 28.1;
29static const double kCommandBlockSwitchCost = 13.5;
30static const double kDistanceBlockSwitchCost = 14.6;
31static const size_t kLiteralStrideLength = 70;
32static const size_t kCommandStrideLength = 40;
33static const size_t kSymbolsPerLiteralHistogram = 544;
34static const size_t kSymbolsPerCommandHistogram = 530;
35static const size_t kSymbolsPerDistanceHistogram = 544;
36static const size_t kMinLengthForBlockSplitting = 128;
37static const size_t kIterMulForRefining = 2;
38static const size_t kMinItersForRefining = 100;
39
40static size_t CountLiterals(const Command* cmds, const size_t num_commands) {
41 /* Count how many we have. */
42 size_t total_length = 0;
43 size_t i;
44 for (i = 0; i < num_commands; ++i) {
45 total_length += cmds[i].insert_len_;
46 }
47 return total_length;
48}
49
50static void CopyLiteralsToByteArray(const Command* cmds,
51 const size_t num_commands,
52 const uint8_t* data,
53 const size_t offset,
54 const size_t mask,
55 uint8_t* literals) {
56 size_t pos = 0;
57 size_t from_pos = offset & mask;
58 size_t i;
59 for (i = 0; i < num_commands; ++i) {
60 size_t insert_len = cmds[i].insert_len_;
61 if (from_pos + insert_len > mask) {
62 size_t head_size = mask + 1 - from_pos;
63 memcpy(literals + pos, data + from_pos, head_size);
64 from_pos = 0;
65 pos += head_size;
66 insert_len -= head_size;
67 }
68 if (insert_len > 0) {
69 memcpy(literals + pos, data + from_pos, insert_len);
70 pos += insert_len;
71 }
72 from_pos = (from_pos + insert_len + CommandCopyLen(&cmds[i])) & mask;
73 }
74}
75
76static BROTLI_INLINE uint32_t MyRand(uint32_t* seed) {
77 /* Initial seed should be 7. In this case, loop length is (1 << 29). */
78 *seed *= 16807U;
79 return *seed;
80}
81
82static BROTLI_INLINE double BitCost(size_t count) {
83 return count == 0 ? -2.0 : FastLog2(count);
84}
85
86#define HISTOGRAMS_PER_BATCH 64
87#define CLUSTERS_PER_BATCH 16
88
89#define FN(X) X ## Literal
90#define DataType uint8_t
91/* NOLINTNEXTLINE(build/include) */
92#include "./block_splitter_inc.h"
93#undef DataType
94#undef FN
95
96#define FN(X) X ## Command
97#define DataType uint16_t
98/* NOLINTNEXTLINE(build/include) */
99#include "./block_splitter_inc.h"
100#undef FN
101
102#define FN(X) X ## Distance
103/* NOLINTNEXTLINE(build/include) */
104#include "./block_splitter_inc.h"
105#undef DataType
106#undef FN
107
108void BrotliInitBlockSplit(BlockSplit* self) {
109 self->num_types = 0;
110 self->num_blocks = 0;
111 self->types = 0;
112 self->lengths = 0;
113 self->types_alloc_size = 0;
114 self->lengths_alloc_size = 0;
115}
116
117void BrotliDestroyBlockSplit(MemoryManager* m, BlockSplit* self) {
118 BROTLI_FREE(m, self->types);
119 BROTLI_FREE(m, self->lengths);
120}
121
122void BrotliSplitBlock(MemoryManager* m,
123 const Command* cmds,
124 const size_t num_commands,
125 const uint8_t* data,
126 const size_t pos,
127 const size_t mask,
128 const BrotliEncoderParams* params,
129 BlockSplit* literal_split,
130 BlockSplit* insert_and_copy_split,
131 BlockSplit* dist_split) {
132 {
133 size_t literals_count = CountLiterals(cmds, num_commands);
134 uint8_t* literals = BROTLI_ALLOC(m, uint8_t, literals_count);
135 if (BROTLI_IS_OOM(m)) return;
136 /* Create a continuous array of literals. */
137 CopyLiteralsToByteArray(cmds, num_commands, data, pos, mask, literals);
138 /* Create the block split on the array of literals.
139 Literal histograms have alphabet size 256. */
140 SplitByteVectorLiteral(
141 m, literals, literals_count,
142 kSymbolsPerLiteralHistogram, kMaxLiteralHistograms,
143 kLiteralStrideLength, kLiteralBlockSwitchCost, params,
144 literal_split);
145 if (BROTLI_IS_OOM(m)) return;
146 BROTLI_FREE(m, literals);
147 }
148
149 {
150 /* Compute prefix codes for commands. */
151 uint16_t* insert_and_copy_codes = BROTLI_ALLOC(m, uint16_t, num_commands);
152 size_t i;
153 if (BROTLI_IS_OOM(m)) return;
154 for (i = 0; i < num_commands; ++i) {
155 insert_and_copy_codes[i] = cmds[i].cmd_prefix_;
156 }
157 /* Create the block split on the array of command prefixes. */
158 SplitByteVectorCommand(
159 m, insert_and_copy_codes, num_commands,
160 kSymbolsPerCommandHistogram, kMaxCommandHistograms,
161 kCommandStrideLength, kCommandBlockSwitchCost, params,
162 insert_and_copy_split);
163 if (BROTLI_IS_OOM(m)) return;
164 /* TODO: reuse for distances? */
165 BROTLI_FREE(m, insert_and_copy_codes);
166 }
167
168 {
169 /* Create a continuous array of distance prefixes. */
170 uint16_t* distance_prefixes = BROTLI_ALLOC(m, uint16_t, num_commands);
171 size_t j = 0;
172 size_t i;
173 if (BROTLI_IS_OOM(m)) return;
174 for (i = 0; i < num_commands; ++i) {
175 const Command* cmd = &cmds[i];
176 if (CommandCopyLen(cmd) && cmd->cmd_prefix_ >= 128) {
177 distance_prefixes[j++] = cmd->dist_prefix_ & 0x3FF;
178 }
179 }
180 /* Create the block split on the array of distance prefixes. */
181 SplitByteVectorDistance(
182 m, distance_prefixes, j,
183 kSymbolsPerDistanceHistogram, kMaxCommandHistograms,
184 kCommandStrideLength, kDistanceBlockSwitchCost, params,
185 dist_split);
186 if (BROTLI_IS_OOM(m)) return;
187 BROTLI_FREE(m, distance_prefixes);
188 }
189}
190
191
192#if defined(__cplusplus) || defined(c_plusplus)
193} /* extern "C" */
194#endif
195