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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 | /* Utilities for building Huffman decoding tables. */ | |
8 | ||
9 | #include <stdlib.h> | |
10 | #include <stdio.h> | |
11 | #include <string.h> | |
12 | #include "./huffman.h" | |
13 | #include "./port.h" | |
14 | ||
15 | #if defined(__cplusplus) || defined(c_plusplus) | |
16 | extern "C" { | |
17 | #endif | |
18 | ||
19 | #define BROTLI_REVERSE_BITS_MAX 8 | |
20 | ||
21 | #ifdef BROTLI_RBIT | |
22 | #define BROTLI_REVERSE_BITS_BASE (32 - BROTLI_REVERSE_BITS_MAX) | |
23 | #else | |
24 | #define BROTLI_REVERSE_BITS_BASE 0 | |
25 | static uint8_t kReverseBits[1 << BROTLI_REVERSE_BITS_MAX] = { | |
26 | 0x00, 0x80, 0x40, 0xC0, 0x20, 0xA0, 0x60, 0xE0, | |
27 | 0x10, 0x90, 0x50, 0xD0, 0x30, 0xB0, 0x70, 0xF0, | |
28 | 0x08, 0x88, 0x48, 0xC8, 0x28, 0xA8, 0x68, 0xE8, | |
29 | 0x18, 0x98, 0x58, 0xD8, 0x38, 0xB8, 0x78, 0xF8, | |
30 | 0x04, 0x84, 0x44, 0xC4, 0x24, 0xA4, 0x64, 0xE4, | |
31 | 0x14, 0x94, 0x54, 0xD4, 0x34, 0xB4, 0x74, 0xF4, | |
32 | 0x0C, 0x8C, 0x4C, 0xCC, 0x2C, 0xAC, 0x6C, 0xEC, | |
33 | 0x1C, 0x9C, 0x5C, 0xDC, 0x3C, 0xBC, 0x7C, 0xFC, | |
34 | 0x02, 0x82, 0x42, 0xC2, 0x22, 0xA2, 0x62, 0xE2, | |
35 | 0x12, 0x92, 0x52, 0xD2, 0x32, 0xB2, 0x72, 0xF2, | |
36 | 0x0A, 0x8A, 0x4A, 0xCA, 0x2A, 0xAA, 0x6A, 0xEA, | |
37 | 0x1A, 0x9A, 0x5A, 0xDA, 0x3A, 0xBA, 0x7A, 0xFA, | |
38 | 0x06, 0x86, 0x46, 0xC6, 0x26, 0xA6, 0x66, 0xE6, | |
39 | 0x16, 0x96, 0x56, 0xD6, 0x36, 0xB6, 0x76, 0xF6, | |
40 | 0x0E, 0x8E, 0x4E, 0xCE, 0x2E, 0xAE, 0x6E, 0xEE, | |
41 | 0x1E, 0x9E, 0x5E, 0xDE, 0x3E, 0xBE, 0x7E, 0xFE, | |
42 | 0x01, 0x81, 0x41, 0xC1, 0x21, 0xA1, 0x61, 0xE1, | |
43 | 0x11, 0x91, 0x51, 0xD1, 0x31, 0xB1, 0x71, 0xF1, | |
44 | 0x09, 0x89, 0x49, 0xC9, 0x29, 0xA9, 0x69, 0xE9, | |
45 | 0x19, 0x99, 0x59, 0xD9, 0x39, 0xB9, 0x79, 0xF9, | |
46 | 0x05, 0x85, 0x45, 0xC5, 0x25, 0xA5, 0x65, 0xE5, | |
47 | 0x15, 0x95, 0x55, 0xD5, 0x35, 0xB5, 0x75, 0xF5, | |
48 | 0x0D, 0x8D, 0x4D, 0xCD, 0x2D, 0xAD, 0x6D, 0xED, | |
49 | 0x1D, 0x9D, 0x5D, 0xDD, 0x3D, 0xBD, 0x7D, 0xFD, | |
50 | 0x03, 0x83, 0x43, 0xC3, 0x23, 0xA3, 0x63, 0xE3, | |
51 | 0x13, 0x93, 0x53, 0xD3, 0x33, 0xB3, 0x73, 0xF3, | |
52 | 0x0B, 0x8B, 0x4B, 0xCB, 0x2B, 0xAB, 0x6B, 0xEB, | |
53 | 0x1B, 0x9B, 0x5B, 0xDB, 0x3B, 0xBB, 0x7B, 0xFB, | |
54 | 0x07, 0x87, 0x47, 0xC7, 0x27, 0xA7, 0x67, 0xE7, | |
55 | 0x17, 0x97, 0x57, 0xD7, 0x37, 0xB7, 0x77, 0xF7, | |
56 | 0x0F, 0x8F, 0x4F, 0xCF, 0x2F, 0xAF, 0x6F, 0xEF, | |
57 | 0x1F, 0x9F, 0x5F, 0xDF, 0x3F, 0xBF, 0x7F, 0xFF | |
58 | }; | |
59 | #endif /* BROTLI_RBIT */ | |
60 | ||
61 | #define BROTLI_REVERSE_BITS_LOWEST \ | |
62 | (1U << (BROTLI_REVERSE_BITS_MAX - 1 + BROTLI_REVERSE_BITS_BASE)) | |
63 | ||
64 | /* Returns reverse(num >> BROTLI_REVERSE_BITS_BASE, BROTLI_REVERSE_BITS_MAX), | |
65 | where reverse(value, len) is the bit-wise reversal of the len least | |
66 | significant bits of value. */ | |
67 | static BROTLI_INLINE uint32_t BrotliReverseBits(uint32_t num) { | |
68 | #ifdef BROTLI_RBIT | |
69 | return BROTLI_RBIT(num); | |
70 | #else | |
71 | return kReverseBits[num]; | |
72 | #endif | |
73 | } | |
74 | ||
75 | /* Stores code in table[0], table[step], table[2*step], ..., table[end] */ | |
76 | /* Assumes that end is an integer multiple of step */ | |
77 | static BROTLI_INLINE void ReplicateValue(HuffmanCode* table, | |
78 | int step, int end, | |
79 | HuffmanCode code) { | |
80 | do { | |
81 | end -= step; | |
82 | table[end] = code; | |
83 | } while (end > 0); | |
84 | } | |
85 | ||
86 | /* Returns the table width of the next 2nd level table. count is the histogram | |
87 | of bit lengths for the remaining symbols, len is the code length of the next | |
88 | processed symbol */ | |
89 | static BROTLI_INLINE int NextTableBitSize(const uint16_t* const count, | |
90 | int len, int root_bits) { | |
91 | int left = 1 << (len - root_bits); | |
92 | while (len < BROTLI_HUFFMAN_MAX_CODE_LENGTH) { | |
93 | left -= count[len]; | |
94 | if (left <= 0) break; | |
95 | ++len; | |
96 | left <<= 1; | |
97 | } | |
98 | return len - root_bits; | |
99 | } | |
100 | ||
101 | ||
102 | void BrotliBuildCodeLengthsHuffmanTable(HuffmanCode* table, | |
103 | const uint8_t* const code_lengths, | |
104 | uint16_t *count) { | |
105 | HuffmanCode code; /* current table entry */ | |
106 | int symbol; /* symbol index in original or sorted table */ | |
107 | uint32_t key; /* prefix code */ | |
108 | uint32_t key_step; /* prefix code addend */ | |
109 | int step; /* step size to replicate values in current table */ | |
110 | int table_size; /* size of current table */ | |
111 | int sorted[18]; /* symbols sorted by code length */ | |
112 | /* offsets in sorted table for each length */ | |
113 | int offset[BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH + 1]; | |
114 | int bits; | |
115 | int bits_count; | |
116 | BROTLI_DCHECK( | |
117 | BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH <= BROTLI_REVERSE_BITS_MAX); | |
118 | ||
119 | /* generate offsets into sorted symbol table by code length */ | |
120 | symbol = -1; | |
121 | bits = 1; | |
122 | BROTLI_REPEAT(BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH, { | |
123 | symbol += count[bits]; | |
124 | offset[bits] = symbol; | |
125 | bits++; | |
126 | }); | |
127 | /* Symbols with code length 0 are placed after all other symbols. */ | |
128 | offset[0] = 17; | |
129 | ||
130 | /* sort symbols by length, by symbol order within each length */ | |
131 | symbol = 18; | |
132 | do { | |
133 | BROTLI_REPEAT(6, { | |
134 | symbol--; | |
135 | sorted[offset[code_lengths[symbol]]--] = symbol; | |
136 | }); | |
137 | } while (symbol != 0); | |
138 | ||
139 | table_size = 1 << BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH; | |
140 | ||
141 | /* Special case: all symbols but one have 0 code length. */ | |
142 | if (offset[0] == 0) { | |
143 | code.bits = 0; | |
144 | code.value = (uint16_t)sorted[0]; | |
145 | for (key = 0; key < (uint32_t)table_size; ++key) { | |
146 | table[key] = code; | |
147 | } | |
148 | return; | |
149 | } | |
150 | ||
151 | /* fill in table */ | |
152 | key = 0; | |
153 | key_step = BROTLI_REVERSE_BITS_LOWEST; | |
154 | symbol = 0; | |
155 | bits = 1; | |
156 | step = 2; | |
157 | do { | |
158 | code.bits = (uint8_t)bits; | |
159 | for (bits_count = count[bits]; bits_count != 0; --bits_count) { | |
160 | code.value = (uint16_t)sorted[symbol++]; | |
161 | ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code); | |
162 | key += key_step; | |
163 | } | |
164 | step <<= 1; | |
165 | key_step >>= 1; | |
166 | } while (++bits <= BROTLI_HUFFMAN_MAX_CODE_LENGTH_CODE_LENGTH); | |
167 | } | |
168 | ||
169 | uint32_t BrotliBuildHuffmanTable(HuffmanCode* root_table, | |
170 | int root_bits, | |
171 | const uint16_t* const symbol_lists, | |
172 | uint16_t *count) { | |
173 | HuffmanCode code; /* current table entry */ | |
174 | HuffmanCode* table; /* next available space in table */ | |
175 | int len; /* current code length */ | |
176 | int symbol; /* symbol index in original or sorted table */ | |
177 | uint32_t key; /* prefix code */ | |
178 | uint32_t key_step; /* prefix code addend */ | |
179 | uint32_t sub_key; /* 2nd level table prefix code */ | |
180 | uint32_t sub_key_step;/* 2nd level table prefix code addend */ | |
181 | int step; /* step size to replicate values in current table */ | |
182 | int table_bits; /* key length of current table */ | |
183 | int table_size; /* size of current table */ | |
184 | int total_size; /* sum of root table size and 2nd level table sizes */ | |
185 | int max_length = -1; | |
186 | int bits; | |
187 | int bits_count; | |
188 | ||
189 | BROTLI_DCHECK(root_bits <= BROTLI_REVERSE_BITS_MAX); | |
190 | BROTLI_DCHECK( | |
191 | BROTLI_HUFFMAN_MAX_CODE_LENGTH - root_bits <= BROTLI_REVERSE_BITS_MAX); | |
192 | ||
193 | while (symbol_lists[max_length] == 0xFFFF) max_length--; | |
194 | max_length += BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1; | |
195 | ||
196 | table = root_table; | |
197 | table_bits = root_bits; | |
198 | table_size = 1 << table_bits; | |
199 | total_size = table_size; | |
200 | ||
201 | /* fill in root table */ | |
202 | /* let's reduce the table size to a smaller size if possible, and */ | |
203 | /* create the repetitions by memcpy if possible in the coming loop */ | |
204 | if (table_bits > max_length) { | |
205 | table_bits = max_length; | |
206 | table_size = 1 << table_bits; | |
207 | } | |
208 | key = 0; | |
209 | key_step = BROTLI_REVERSE_BITS_LOWEST; | |
210 | bits = 1; | |
211 | step = 2; | |
212 | do { | |
213 | code.bits = (uint8_t)bits; | |
214 | symbol = bits - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1); | |
215 | for (bits_count = count[bits]; bits_count != 0; --bits_count) { | |
216 | symbol = symbol_lists[symbol]; | |
217 | code.value = (uint16_t)symbol; | |
218 | ReplicateValue(&table[BrotliReverseBits(key)], step, table_size, code); | |
219 | key += key_step; | |
220 | } | |
221 | step <<= 1; | |
222 | key_step >>= 1; | |
223 | } while (++bits <= table_bits); | |
224 | ||
225 | /* if root_bits != table_bits we only created one fraction of the */ | |
226 | /* table, and we need to replicate it now. */ | |
227 | while (total_size != table_size) { | |
228 | memcpy(&table[table_size], &table[0], | |
229 | (size_t)table_size * sizeof(table[0])); | |
230 | table_size <<= 1; | |
231 | } | |
232 | ||
233 | /* fill in 2nd level tables and add pointers to root table */ | |
234 | key_step = BROTLI_REVERSE_BITS_LOWEST >> (root_bits - 1); | |
235 | sub_key = (BROTLI_REVERSE_BITS_LOWEST << 1); | |
236 | sub_key_step = BROTLI_REVERSE_BITS_LOWEST; | |
237 | for (len = root_bits + 1, step = 2; len <= max_length; ++len) { | |
238 | symbol = len - (BROTLI_HUFFMAN_MAX_CODE_LENGTH + 1); | |
239 | for (; count[len] != 0; --count[len]) { | |
240 | if (sub_key == (uint32_t)(BROTLI_REVERSE_BITS_LOWEST << 1)) { | |
241 | table += table_size; | |
242 | table_bits = NextTableBitSize(count, len, root_bits); | |
243 | table_size = 1 << table_bits; | |
244 | total_size += table_size; | |
245 | sub_key = BrotliReverseBits(key); | |
246 | key += key_step; | |
247 | root_table[sub_key].bits = (uint8_t)(table_bits + root_bits); | |
248 | root_table[sub_key].value = (uint16_t)( | |
249 | ((size_t)(table - root_table)) - sub_key); | |
250 | sub_key = 0; | |
251 | } | |
252 | code.bits = (uint8_t)(len - root_bits); | |
253 | symbol = symbol_lists[symbol]; | |
254 | code.value = (uint16_t)symbol; | |
255 | ReplicateValue( | |
256 | &table[BrotliReverseBits(sub_key)], step, table_size, code); | |
257 | sub_key += sub_key_step; | |
258 | } | |
259 | step <<= 1; | |
260 | sub_key_step >>= 1; | |
261 | } | |
262 | return (uint32_t)total_size; | |
263 | } | |
264 | ||
265 | uint32_t BrotliBuildSimpleHuffmanTable(HuffmanCode* table, | |
266 | int root_bits, | |
267 | uint16_t *val, | |
268 | uint32_t num_symbols) { | |
269 | uint32_t table_size = 1; | |
270 | const uint32_t goal_size = 1U << root_bits; | |
271 | switch (num_symbols) { | |
272 | case 0: | |
273 | table[0].bits = 0; | |
274 | table[0].value = val[0]; | |
275 | break; | |
276 | case 1: | |
277 | table[0].bits = 1; | |
278 | table[1].bits = 1; | |
279 | if (val[1] > val[0]) { | |
280 | table[0].value = val[0]; | |
281 | table[1].value = val[1]; | |
282 | } else { | |
283 | table[0].value = val[1]; | |
284 | table[1].value = val[0]; | |
285 | } | |
286 | table_size = 2; | |
287 | break; | |
288 | case 2: | |
289 | table[0].bits = 1; | |
290 | table[0].value = val[0]; | |
291 | table[2].bits = 1; | |
292 | table[2].value = val[0]; | |
293 | if (val[2] > val[1]) { | |
294 | table[1].value = val[1]; | |
295 | table[3].value = val[2]; | |
296 | } else { | |
297 | table[1].value = val[2]; | |
298 | table[3].value = val[1]; | |
299 | } | |
300 | table[1].bits = 2; | |
301 | table[3].bits = 2; | |
302 | table_size = 4; | |
303 | break; | |
304 | case 3: | |
305 | { | |
306 | int i, k; | |
307 | for (i = 0; i < 3; ++i) { | |
308 | for (k = i + 1; k < 4; ++k) { | |
309 | if (val[k] < val[i]) { | |
310 | uint16_t t = val[k]; | |
311 | val[k] = val[i]; | |
312 | val[i] = t; | |
313 | } | |
314 | } | |
315 | } | |
316 | for (i = 0; i < 4; ++i) { | |
317 | table[i].bits = 2; | |
318 | } | |
319 | table[0].value = val[0]; | |
320 | table[2].value = val[1]; | |
321 | table[1].value = val[2]; | |
322 | table[3].value = val[3]; | |
323 | table_size = 4; | |
324 | } | |
325 | break; | |
326 | case 4: | |
327 | { | |
328 | int i; | |
329 | if (val[3] < val[2]) { | |
330 | uint16_t t = val[3]; | |
331 | val[3] = val[2]; | |
332 | val[2] = t; | |
333 | } | |
334 | for (i = 0; i < 7; ++i) { | |
335 | table[i].value = val[0]; | |
336 | table[i].bits = (uint8_t)(1 + (i & 1)); | |
337 | } | |
338 | table[1].value = val[1]; | |
339 | table[3].value = val[2]; | |
340 | table[5].value = val[1]; | |
341 | table[7].value = val[3]; | |
342 | table[3].bits = 3; | |
343 | table[7].bits = 3; | |
344 | table_size = 8; | |
345 | } | |
346 | break; | |
347 | } | |
348 | while (table_size != goal_size) { | |
349 | memcpy(&table[table_size], &table[0], | |
350 | (size_t)table_size * sizeof(table[0])); | |
351 | table_size <<= 1; | |
352 | } | |
353 | return goal_size; | |
354 | } | |
355 | ||
356 | #if defined(__cplusplus) || defined(c_plusplus) | |
357 | } /* extern "C" */ | |
358 | #endif |