1 /* 2 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc. 3 * All rights reserved. 4 * 5 * This source code is licensed under both the BSD-style license (found in the 6 * LICENSE file in the root directory of this source tree) and the GPLv2 (found 7 * in the COPYING file in the root directory of this source tree). 8 * You may select, at your option, one of the above-listed licenses. 9 */ 10 11 /*-************************************* 12 * Dependencies 13 ***************************************/ 14 #include "zstd_compress_sequences.h" 15 16 /** 17 * -log2(x / 256) lookup table for x in [0, 256). 18 * If x == 0: Return 0 19 * Else: Return floor(-log2(x / 256) * 256) 20 */ 21 static unsigned const kInverseProbabilityLog256[256] = { 22 0, 2048, 1792, 1642, 1536, 1453, 1386, 1329, 1280, 1236, 1197, 1162, 23 1130, 1100, 1073, 1047, 1024, 1001, 980, 960, 941, 923, 906, 889, 24 874, 859, 844, 830, 817, 804, 791, 779, 768, 756, 745, 734, 25 724, 714, 704, 694, 685, 676, 667, 658, 650, 642, 633, 626, 26 618, 610, 603, 595, 588, 581, 574, 567, 561, 554, 548, 542, 27 535, 529, 523, 517, 512, 506, 500, 495, 489, 484, 478, 473, 28 468, 463, 458, 453, 448, 443, 438, 434, 429, 424, 420, 415, 29 411, 407, 402, 398, 394, 390, 386, 382, 377, 373, 370, 366, 30 362, 358, 354, 350, 347, 343, 339, 336, 332, 329, 325, 322, 31 318, 315, 311, 308, 305, 302, 298, 295, 292, 289, 286, 282, 32 279, 276, 273, 270, 267, 264, 261, 258, 256, 253, 250, 247, 33 244, 241, 239, 236, 233, 230, 228, 225, 222, 220, 217, 215, 34 212, 209, 207, 204, 202, 199, 197, 194, 192, 190, 187, 185, 35 182, 180, 178, 175, 173, 171, 168, 166, 164, 162, 159, 157, 36 155, 153, 151, 149, 146, 144, 142, 140, 138, 136, 134, 132, 37 130, 128, 126, 123, 121, 119, 117, 115, 114, 112, 110, 108, 38 106, 104, 102, 100, 98, 96, 94, 93, 91, 89, 87, 85, 39 83, 82, 80, 78, 76, 74, 73, 71, 69, 67, 66, 64, 40 62, 61, 59, 57, 55, 54, 52, 50, 49, 47, 46, 44, 41 42, 41, 39, 37, 36, 34, 33, 31, 30, 28, 26, 25, 42 23, 22, 20, 19, 17, 16, 14, 13, 11, 10, 8, 7, 43 5, 4, 2, 1, 44 }; 45 46 static unsigned ZSTD_getFSEMaxSymbolValue(FSE_CTable const* ctable) { 47 void const* ptr = ctable; 48 U16 const* u16ptr = (U16 const*)ptr; 49 U32 const maxSymbolValue = MEM_read16(u16ptr + 1); 50 return maxSymbolValue; 51 } 52 53 /** 54 * Returns the cost in bytes of encoding the normalized count header. 55 * Returns an error if any of the helper functions return an error. 56 */ 57 static size_t ZSTD_NCountCost(unsigned const* count, unsigned const max, 58 size_t const nbSeq, unsigned const FSELog) 59 { 60 BYTE wksp[FSE_NCOUNTBOUND]; 61 S16 norm[MaxSeq + 1]; 62 const U32 tableLog = FSE_optimalTableLog(FSELog, nbSeq, max); 63 FORWARD_IF_ERROR(FSE_normalizeCount(norm, tableLog, count, nbSeq, max)); 64 return FSE_writeNCount(wksp, sizeof(wksp), norm, max, tableLog); 65 } 66 67 /** 68 * Returns the cost in bits of encoding the distribution described by count 69 * using the entropy bound. 70 */ 71 static size_t ZSTD_entropyCost(unsigned const* count, unsigned const max, size_t const total) 72 { 73 unsigned cost = 0; 74 unsigned s; 75 for (s = 0; s <= max; ++s) { 76 unsigned norm = (unsigned)((256 * count[s]) / total); 77 if (count[s] != 0 && norm == 0) 78 norm = 1; 79 assert(count[s] < total); 80 cost += count[s] * kInverseProbabilityLog256[norm]; 81 } 82 return cost >> 8; 83 } 84 85 /** 86 * Returns the cost in bits of encoding the distribution in count using ctable. 87 * Returns an error if ctable cannot represent all the symbols in count. 88 */ 89 static size_t ZSTD_fseBitCost( 90 FSE_CTable const* ctable, 91 unsigned const* count, 92 unsigned const max) 93 { 94 unsigned const kAccuracyLog = 8; 95 size_t cost = 0; 96 unsigned s; 97 FSE_CState_t cstate; 98 FSE_initCState(&cstate, ctable); 99 RETURN_ERROR_IF(ZSTD_getFSEMaxSymbolValue(ctable) < max, GENERIC, 100 "Repeat FSE_CTable has maxSymbolValue %u < %u", 101 ZSTD_getFSEMaxSymbolValue(ctable), max); 102 for (s = 0; s <= max; ++s) { 103 unsigned const tableLog = cstate.stateLog; 104 unsigned const badCost = (tableLog + 1) << kAccuracyLog; 105 unsigned const bitCost = FSE_bitCost(cstate.symbolTT, tableLog, s, kAccuracyLog); 106 if (count[s] == 0) 107 continue; 108 RETURN_ERROR_IF(bitCost >= badCost, GENERIC, 109 "Repeat FSE_CTable has Prob[%u] == 0", s); 110 cost += count[s] * bitCost; 111 } 112 return cost >> kAccuracyLog; 113 } 114 115 /** 116 * Returns the cost in bits of encoding the distribution in count using the 117 * table described by norm. The max symbol support by norm is assumed >= max. 118 * norm must be valid for every symbol with non-zero probability in count. 119 */ 120 static size_t ZSTD_crossEntropyCost(short const* norm, unsigned accuracyLog, 121 unsigned const* count, unsigned const max) 122 { 123 unsigned const shift = 8 - accuracyLog; 124 size_t cost = 0; 125 unsigned s; 126 assert(accuracyLog <= 8); 127 for (s = 0; s <= max; ++s) { 128 unsigned const normAcc = norm[s] != -1 ? norm[s] : 1; 129 unsigned const norm256 = normAcc << shift; 130 assert(norm256 > 0); 131 assert(norm256 < 256); 132 cost += count[s] * kInverseProbabilityLog256[norm256]; 133 } 134 return cost >> 8; 135 } 136 137 symbolEncodingType_e 138 ZSTD_selectEncodingType( 139 FSE_repeat* repeatMode, unsigned const* count, unsigned const max, 140 size_t const mostFrequent, size_t nbSeq, unsigned const FSELog, 141 FSE_CTable const* prevCTable, 142 short const* defaultNorm, U32 defaultNormLog, 143 ZSTD_defaultPolicy_e const isDefaultAllowed, 144 ZSTD_strategy const strategy) 145 { 146 ZSTD_STATIC_ASSERT(ZSTD_defaultDisallowed == 0 && ZSTD_defaultAllowed != 0); 147 if (mostFrequent == nbSeq) { 148 *repeatMode = FSE_repeat_none; 149 if (isDefaultAllowed && nbSeq <= 2) { 150 /* Prefer set_basic over set_rle when there are 2 or less symbols, 151 * since RLE uses 1 byte, but set_basic uses 5-6 bits per symbol. 152 * If basic encoding isn't possible, always choose RLE. 153 */ 154 DEBUGLOG(5, "Selected set_basic"); 155 return set_basic; 156 } 157 DEBUGLOG(5, "Selected set_rle"); 158 return set_rle; 159 } 160 if (strategy < ZSTD_lazy) { 161 if (isDefaultAllowed) { 162 size_t const staticFse_nbSeq_max = 1000; 163 size_t const mult = 10 - strategy; 164 size_t const baseLog = 3; 165 size_t const dynamicFse_nbSeq_min = (((size_t)1 << defaultNormLog) * mult) >> baseLog; /* 28-36 for offset, 56-72 for lengths */ 166 assert(defaultNormLog >= 5 && defaultNormLog <= 6); /* xx_DEFAULTNORMLOG */ 167 assert(mult <= 9 && mult >= 7); 168 if ( (*repeatMode == FSE_repeat_valid) 169 && (nbSeq < staticFse_nbSeq_max) ) { 170 DEBUGLOG(5, "Selected set_repeat"); 171 return set_repeat; 172 } 173 if ( (nbSeq < dynamicFse_nbSeq_min) 174 || (mostFrequent < (nbSeq >> (defaultNormLog-1))) ) { 175 DEBUGLOG(5, "Selected set_basic"); 176 /* The format allows default tables to be repeated, but it isn't useful. 177 * When using simple heuristics to select encoding type, we don't want 178 * to confuse these tables with dictionaries. When running more careful 179 * analysis, we don't need to waste time checking both repeating tables 180 * and default tables. 181 */ 182 *repeatMode = FSE_repeat_none; 183 return set_basic; 184 } 185 } 186 } else { 187 size_t const basicCost = isDefaultAllowed ? ZSTD_crossEntropyCost(defaultNorm, defaultNormLog, count, max) : ERROR(GENERIC); 188 size_t const repeatCost = *repeatMode != FSE_repeat_none ? ZSTD_fseBitCost(prevCTable, count, max) : ERROR(GENERIC); 189 size_t const NCountCost = ZSTD_NCountCost(count, max, nbSeq, FSELog); 190 size_t const compressedCost = (NCountCost << 3) + ZSTD_entropyCost(count, max, nbSeq); 191 192 if (isDefaultAllowed) { 193 assert(!ZSTD_isError(basicCost)); 194 assert(!(*repeatMode == FSE_repeat_valid && ZSTD_isError(repeatCost))); 195 } 196 assert(!ZSTD_isError(NCountCost)); 197 assert(compressedCost < ERROR(maxCode)); 198 DEBUGLOG(5, "Estimated bit costs: basic=%u\trepeat=%u\tcompressed=%u", 199 (unsigned)basicCost, (unsigned)repeatCost, (unsigned)compressedCost); 200 if (basicCost <= repeatCost && basicCost <= compressedCost) { 201 DEBUGLOG(5, "Selected set_basic"); 202 assert(isDefaultAllowed); 203 *repeatMode = FSE_repeat_none; 204 return set_basic; 205 } 206 if (repeatCost <= compressedCost) { 207 DEBUGLOG(5, "Selected set_repeat"); 208 assert(!ZSTD_isError(repeatCost)); 209 return set_repeat; 210 } 211 assert(compressedCost < basicCost && compressedCost < repeatCost); 212 } 213 DEBUGLOG(5, "Selected set_compressed"); 214 *repeatMode = FSE_repeat_check; 215 return set_compressed; 216 } 217 218 size_t 219 ZSTD_buildCTable(void* dst, size_t dstCapacity, 220 FSE_CTable* nextCTable, U32 FSELog, symbolEncodingType_e type, 221 unsigned* count, U32 max, 222 const BYTE* codeTable, size_t nbSeq, 223 const S16* defaultNorm, U32 defaultNormLog, U32 defaultMax, 224 const FSE_CTable* prevCTable, size_t prevCTableSize, 225 void* entropyWorkspace, size_t entropyWorkspaceSize) 226 { 227 BYTE* op = (BYTE*)dst; 228 const BYTE* const oend = op + dstCapacity; 229 DEBUGLOG(6, "ZSTD_buildCTable (dstCapacity=%u)", (unsigned)dstCapacity); 230 231 switch (type) { 232 case set_rle: 233 FORWARD_IF_ERROR(FSE_buildCTable_rle(nextCTable, (BYTE)max)); 234 RETURN_ERROR_IF(dstCapacity==0, dstSize_tooSmall); 235 *op = codeTable[0]; 236 return 1; 237 case set_repeat: 238 memcpy(nextCTable, prevCTable, prevCTableSize); 239 return 0; 240 case set_basic: 241 FORWARD_IF_ERROR(FSE_buildCTable_wksp(nextCTable, defaultNorm, defaultMax, defaultNormLog, entropyWorkspace, entropyWorkspaceSize)); /* note : could be pre-calculated */ 242 return 0; 243 case set_compressed: { 244 S16 norm[MaxSeq + 1]; 245 size_t nbSeq_1 = nbSeq; 246 const U32 tableLog = FSE_optimalTableLog(FSELog, nbSeq, max); 247 if (count[codeTable[nbSeq-1]] > 1) { 248 count[codeTable[nbSeq-1]]--; 249 nbSeq_1--; 250 } 251 assert(nbSeq_1 > 1); 252 FORWARD_IF_ERROR(FSE_normalizeCount(norm, tableLog, count, nbSeq_1, max)); 253 { size_t const NCountSize = FSE_writeNCount(op, oend - op, norm, max, tableLog); /* overflow protected */ 254 FORWARD_IF_ERROR(NCountSize); 255 FORWARD_IF_ERROR(FSE_buildCTable_wksp(nextCTable, norm, max, tableLog, entropyWorkspace, entropyWorkspaceSize)); 256 return NCountSize; 257 } 258 } 259 default: assert(0); RETURN_ERROR(GENERIC); 260 } 261 } 262 263 FORCE_INLINE_TEMPLATE size_t 264 ZSTD_encodeSequences_body( 265 void* dst, size_t dstCapacity, 266 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 267 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 268 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 269 seqDef const* sequences, size_t nbSeq, int longOffsets) 270 { 271 BIT_CStream_t blockStream; 272 FSE_CState_t stateMatchLength; 273 FSE_CState_t stateOffsetBits; 274 FSE_CState_t stateLitLength; 275 276 RETURN_ERROR_IF( 277 ERR_isError(BIT_initCStream(&blockStream, dst, dstCapacity)), 278 dstSize_tooSmall, "not enough space remaining"); 279 DEBUGLOG(6, "available space for bitstream : %i (dstCapacity=%u)", 280 (int)(blockStream.endPtr - blockStream.startPtr), 281 (unsigned)dstCapacity); 282 283 /* first symbols */ 284 FSE_initCState2(&stateMatchLength, CTable_MatchLength, mlCodeTable[nbSeq-1]); 285 FSE_initCState2(&stateOffsetBits, CTable_OffsetBits, ofCodeTable[nbSeq-1]); 286 FSE_initCState2(&stateLitLength, CTable_LitLength, llCodeTable[nbSeq-1]); 287 BIT_addBits(&blockStream, sequences[nbSeq-1].litLength, LL_bits[llCodeTable[nbSeq-1]]); 288 if (MEM_32bits()) BIT_flushBits(&blockStream); 289 BIT_addBits(&blockStream, sequences[nbSeq-1].matchLength, ML_bits[mlCodeTable[nbSeq-1]]); 290 if (MEM_32bits()) BIT_flushBits(&blockStream); 291 if (longOffsets) { 292 U32 const ofBits = ofCodeTable[nbSeq-1]; 293 int const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN-1); 294 if (extraBits) { 295 BIT_addBits(&blockStream, sequences[nbSeq-1].offset, extraBits); 296 BIT_flushBits(&blockStream); 297 } 298 BIT_addBits(&blockStream, sequences[nbSeq-1].offset >> extraBits, 299 ofBits - extraBits); 300 } else { 301 BIT_addBits(&blockStream, sequences[nbSeq-1].offset, ofCodeTable[nbSeq-1]); 302 } 303 BIT_flushBits(&blockStream); 304 305 { size_t n; 306 for (n=nbSeq-2 ; n<nbSeq ; n--) { /* intentional underflow */ 307 BYTE const llCode = llCodeTable[n]; 308 BYTE const ofCode = ofCodeTable[n]; 309 BYTE const mlCode = mlCodeTable[n]; 310 U32 const llBits = LL_bits[llCode]; 311 U32 const ofBits = ofCode; 312 U32 const mlBits = ML_bits[mlCode]; 313 DEBUGLOG(6, "encoding: litlen:%2u - matchlen:%2u - offCode:%7u", 314 (unsigned)sequences[n].litLength, 315 (unsigned)sequences[n].matchLength + MINMATCH, 316 (unsigned)sequences[n].offset); 317 /* 32b*/ /* 64b*/ 318 /* (7)*/ /* (7)*/ 319 FSE_encodeSymbol(&blockStream, &stateOffsetBits, ofCode); /* 15 */ /* 15 */ 320 FSE_encodeSymbol(&blockStream, &stateMatchLength, mlCode); /* 24 */ /* 24 */ 321 if (MEM_32bits()) BIT_flushBits(&blockStream); /* (7)*/ 322 FSE_encodeSymbol(&blockStream, &stateLitLength, llCode); /* 16 */ /* 33 */ 323 if (MEM_32bits() || (ofBits+mlBits+llBits >= 64-7-(LLFSELog+MLFSELog+OffFSELog))) 324 BIT_flushBits(&blockStream); /* (7)*/ 325 BIT_addBits(&blockStream, sequences[n].litLength, llBits); 326 if (MEM_32bits() && ((llBits+mlBits)>24)) BIT_flushBits(&blockStream); 327 BIT_addBits(&blockStream, sequences[n].matchLength, mlBits); 328 if (MEM_32bits() || (ofBits+mlBits+llBits > 56)) BIT_flushBits(&blockStream); 329 if (longOffsets) { 330 int const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN-1); 331 if (extraBits) { 332 BIT_addBits(&blockStream, sequences[n].offset, extraBits); 333 BIT_flushBits(&blockStream); /* (7)*/ 334 } 335 BIT_addBits(&blockStream, sequences[n].offset >> extraBits, 336 ofBits - extraBits); /* 31 */ 337 } else { 338 BIT_addBits(&blockStream, sequences[n].offset, ofBits); /* 31 */ 339 } 340 BIT_flushBits(&blockStream); /* (7)*/ 341 DEBUGLOG(7, "remaining space : %i", (int)(blockStream.endPtr - blockStream.ptr)); 342 } } 343 344 DEBUGLOG(6, "ZSTD_encodeSequences: flushing ML state with %u bits", stateMatchLength.stateLog); 345 FSE_flushCState(&blockStream, &stateMatchLength); 346 DEBUGLOG(6, "ZSTD_encodeSequences: flushing Off state with %u bits", stateOffsetBits.stateLog); 347 FSE_flushCState(&blockStream, &stateOffsetBits); 348 DEBUGLOG(6, "ZSTD_encodeSequences: flushing LL state with %u bits", stateLitLength.stateLog); 349 FSE_flushCState(&blockStream, &stateLitLength); 350 351 { size_t const streamSize = BIT_closeCStream(&blockStream); 352 RETURN_ERROR_IF(streamSize==0, dstSize_tooSmall, "not enough space"); 353 return streamSize; 354 } 355 } 356 357 static size_t 358 ZSTD_encodeSequences_default( 359 void* dst, size_t dstCapacity, 360 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 361 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 362 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 363 seqDef const* sequences, size_t nbSeq, int longOffsets) 364 { 365 return ZSTD_encodeSequences_body(dst, dstCapacity, 366 CTable_MatchLength, mlCodeTable, 367 CTable_OffsetBits, ofCodeTable, 368 CTable_LitLength, llCodeTable, 369 sequences, nbSeq, longOffsets); 370 } 371 372 373 #if DYNAMIC_BMI2 374 375 static TARGET_ATTRIBUTE("bmi2") size_t 376 ZSTD_encodeSequences_bmi2( 377 void* dst, size_t dstCapacity, 378 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 379 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 380 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 381 seqDef const* sequences, size_t nbSeq, int longOffsets) 382 { 383 return ZSTD_encodeSequences_body(dst, dstCapacity, 384 CTable_MatchLength, mlCodeTable, 385 CTable_OffsetBits, ofCodeTable, 386 CTable_LitLength, llCodeTable, 387 sequences, nbSeq, longOffsets); 388 } 389 390 #endif 391 392 size_t ZSTD_encodeSequences( 393 void* dst, size_t dstCapacity, 394 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 395 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 396 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 397 seqDef const* sequences, size_t nbSeq, int longOffsets, int bmi2) 398 { 399 DEBUGLOG(5, "ZSTD_encodeSequences: dstCapacity = %u", (unsigned)dstCapacity); 400 #if DYNAMIC_BMI2 401 if (bmi2) { 402 return ZSTD_encodeSequences_bmi2(dst, dstCapacity, 403 CTable_MatchLength, mlCodeTable, 404 CTable_OffsetBits, ofCodeTable, 405 CTable_LitLength, llCodeTable, 406 sequences, nbSeq, longOffsets); 407 } 408 #endif 409 (void)bmi2; 410 return ZSTD_encodeSequences_default(dst, dstCapacity, 411 CTable_MatchLength, mlCodeTable, 412 CTable_OffsetBits, ofCodeTable, 413 CTable_LitLength, llCodeTable, 414 sequences, nbSeq, longOffsets); 415 } 416