Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/zstd/lib/compress/zstd_compress_sequences.c
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1 /* 2 * Copyright (c) 2016-2020, 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 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 if (ZSTD_getFSEMaxSymbolValue(ctable) < max) { 100 DEBUGLOG(5, "Repeat FSE_CTable has maxSymbolValue %u < %u", 101 ZSTD_getFSEMaxSymbolValue(ctable), max); 102 return ERROR(GENERIC); 103 } 104 for (s = 0; s <= max; ++s) { 105 unsigned const tableLog = cstate.stateLog; 106 unsigned const badCost = (tableLog + 1) << kAccuracyLog; 107 unsigned const bitCost = FSE_bitCost(cstate.symbolTT, tableLog, s, kAccuracyLog); 108 if (count[s] == 0) 109 continue; 110 if (bitCost >= badCost) { 111 DEBUGLOG(5, "Repeat FSE_CTable has Prob[%u] == 0", s); 112 return ERROR(GENERIC); 113 } 114 cost += (size_t)count[s] * bitCost; 115 } 116 return cost >> kAccuracyLog; 117 } 118 119 /** 120 * Returns the cost in bits of encoding the distribution in count using the 121 * table described by norm. The max symbol support by norm is assumed >= max. 122 * norm must be valid for every symbol with non-zero probability in count. 123 */ 124 size_t ZSTD_crossEntropyCost(short const* norm, unsigned accuracyLog, 125 unsigned const* count, unsigned const max) 126 { 127 unsigned const shift = 8 - accuracyLog; 128 size_t cost = 0; 129 unsigned s; 130 assert(accuracyLog <= 8); 131 for (s = 0; s <= max; ++s) { 132 unsigned const normAcc = (norm[s] != -1) ? (unsigned)norm[s] : 1; 133 unsigned const norm256 = normAcc << shift; 134 assert(norm256 > 0); 135 assert(norm256 < 256); 136 cost += count[s] * kInverseProbabilityLog256[norm256]; 137 } 138 return cost >> 8; 139 } 140 141 symbolEncodingType_e 142 ZSTD_selectEncodingType( 143 FSE_repeat* repeatMode, unsigned const* count, unsigned const max, 144 size_t const mostFrequent, size_t nbSeq, unsigned const FSELog, 145 FSE_CTable const* prevCTable, 146 short const* defaultNorm, U32 defaultNormLog, 147 ZSTD_defaultPolicy_e const isDefaultAllowed, 148 ZSTD_strategy const strategy) 149 { 150 ZSTD_STATIC_ASSERT(ZSTD_defaultDisallowed == 0 && ZSTD_defaultAllowed != 0); 151 if (mostFrequent == nbSeq) { 152 *repeatMode = FSE_repeat_none; 153 if (isDefaultAllowed && nbSeq <= 2) { 154 /* Prefer set_basic over set_rle when there are 2 or less symbols, 155 * since RLE uses 1 byte, but set_basic uses 5-6 bits per symbol. 156 * If basic encoding isn't possible, always choose RLE. 157 */ 158 DEBUGLOG(5, "Selected set_basic"); 159 return set_basic; 160 } 161 DEBUGLOG(5, "Selected set_rle"); 162 return set_rle; 163 } 164 if (strategy < ZSTD_lazy) { 165 if (isDefaultAllowed) { 166 size_t const staticFse_nbSeq_max = 1000; 167 size_t const mult = 10 - strategy; 168 size_t const baseLog = 3; 169 size_t const dynamicFse_nbSeq_min = (((size_t)1 << defaultNormLog) * mult) >> baseLog; /* 28-36 for offset, 56-72 for lengths */ 170 assert(defaultNormLog >= 5 && defaultNormLog <= 6); /* xx_DEFAULTNORMLOG */ 171 assert(mult <= 9 && mult >= 7); 172 if ( (*repeatMode == FSE_repeat_valid) 173 && (nbSeq < staticFse_nbSeq_max) ) { 174 DEBUGLOG(5, "Selected set_repeat"); 175 return set_repeat; 176 } 177 if ( (nbSeq < dynamicFse_nbSeq_min) 178 || (mostFrequent < (nbSeq >> (defaultNormLog-1))) ) { 179 DEBUGLOG(5, "Selected set_basic"); 180 /* The format allows default tables to be repeated, but it isn't useful. 181 * When using simple heuristics to select encoding type, we don't want 182 * to confuse these tables with dictionaries. When running more careful 183 * analysis, we don't need to waste time checking both repeating tables 184 * and default tables. 185 */ 186 *repeatMode = FSE_repeat_none; 187 return set_basic; 188 } 189 } 190 } else { 191 size_t const basicCost = isDefaultAllowed ? ZSTD_crossEntropyCost(defaultNorm, defaultNormLog, count, max) : ERROR(GENERIC); 192 size_t const repeatCost = *repeatMode != FSE_repeat_none ? ZSTD_fseBitCost(prevCTable, count, max) : ERROR(GENERIC); 193 size_t const NCountCost = ZSTD_NCountCost(count, max, nbSeq, FSELog); 194 size_t const compressedCost = (NCountCost << 3) + ZSTD_entropyCost(count, max, nbSeq); 195 196 if (isDefaultAllowed) { 197 assert(!ZSTD_isError(basicCost)); 198 assert(!(*repeatMode == FSE_repeat_valid && ZSTD_isError(repeatCost))); 199 } 200 assert(!ZSTD_isError(NCountCost)); 201 assert(compressedCost < ERROR(maxCode)); 202 DEBUGLOG(5, "Estimated bit costs: basic=%u\trepeat=%u\tcompressed=%u", 203 (unsigned)basicCost, (unsigned)repeatCost, (unsigned)compressedCost); 204 if (basicCost <= repeatCost && basicCost <= compressedCost) { 205 DEBUGLOG(5, "Selected set_basic"); 206 assert(isDefaultAllowed); 207 *repeatMode = FSE_repeat_none; 208 return set_basic; 209 } 210 if (repeatCost <= compressedCost) { 211 DEBUGLOG(5, "Selected set_repeat"); 212 assert(!ZSTD_isError(repeatCost)); 213 return set_repeat; 214 } 215 assert(compressedCost < basicCost && compressedCost < repeatCost); 216 } 217 DEBUGLOG(5, "Selected set_compressed"); 218 *repeatMode = FSE_repeat_check; 219 return set_compressed; 220 } 221 222 size_t 223 ZSTD_buildCTable(void* dst, size_t dstCapacity, 224 FSE_CTable* nextCTable, U32 FSELog, symbolEncodingType_e type, 225 unsigned* count, U32 max, 226 const BYTE* codeTable, size_t nbSeq, 227 const S16* defaultNorm, U32 defaultNormLog, U32 defaultMax, 228 const FSE_CTable* prevCTable, size_t prevCTableSize, 229 void* entropyWorkspace, size_t entropyWorkspaceSize) 230 { 231 BYTE* op = (BYTE*)dst; 232 const BYTE* const oend = op + dstCapacity; 233 DEBUGLOG(6, "ZSTD_buildCTable (dstCapacity=%u)", (unsigned)dstCapacity); 234 235 switch (type) { 236 case set_rle: 237 FORWARD_IF_ERROR(FSE_buildCTable_rle(nextCTable, (BYTE)max), ""); 238 RETURN_ERROR_IF(dstCapacity==0, dstSize_tooSmall, "not enough space"); 239 *op = codeTable[0]; 240 return 1; 241 case set_repeat: 242 memcpy(nextCTable, prevCTable, prevCTableSize); 243 return 0; 244 case set_basic: 245 FORWARD_IF_ERROR(FSE_buildCTable_wksp(nextCTable, defaultNorm, defaultMax, defaultNormLog, entropyWorkspace, entropyWorkspaceSize), ""); /* note : could be pre-calculated */ 246 return 0; 247 case set_compressed: { 248 S16 norm[MaxSeq + 1]; 249 size_t nbSeq_1 = nbSeq; 250 const U32 tableLog = FSE_optimalTableLog(FSELog, nbSeq, max); 251 if (count[codeTable[nbSeq-1]] > 1) { 252 count[codeTable[nbSeq-1]]--; 253 nbSeq_1--; 254 } 255 assert(nbSeq_1 > 1); 256 FORWARD_IF_ERROR(FSE_normalizeCount(norm, tableLog, count, nbSeq_1, max), ""); 257 { size_t const NCountSize = FSE_writeNCount(op, oend - op, norm, max, tableLog); /* overflow protected */ 258 FORWARD_IF_ERROR(NCountSize, "FSE_writeNCount failed"); 259 FORWARD_IF_ERROR(FSE_buildCTable_wksp(nextCTable, norm, max, tableLog, entropyWorkspace, entropyWorkspaceSize), ""); 260 return NCountSize; 261 } 262 } 263 default: assert(0); RETURN_ERROR(GENERIC, "impossible to reach"); 264 } 265 } 266 267 FORCE_INLINE_TEMPLATE size_t 268 ZSTD_encodeSequences_body( 269 void* dst, size_t dstCapacity, 270 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 271 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 272 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 273 seqDef const* sequences, size_t nbSeq, int longOffsets) 274 { 275 BIT_CStream_t blockStream; 276 FSE_CState_t stateMatchLength; 277 FSE_CState_t stateOffsetBits; 278 FSE_CState_t stateLitLength; 279 280 RETURN_ERROR_IF( 281 ERR_isError(BIT_initCStream(&blockStream, dst, dstCapacity)), 282 dstSize_tooSmall, "not enough space remaining"); 283 DEBUGLOG(6, "available space for bitstream : %i (dstCapacity=%u)", 284 (int)(blockStream.endPtr - blockStream.startPtr), 285 (unsigned)dstCapacity); 286 287 /* first symbols */ 288 FSE_initCState2(&stateMatchLength, CTable_MatchLength, mlCodeTable[nbSeq-1]); 289 FSE_initCState2(&stateOffsetBits, CTable_OffsetBits, ofCodeTable[nbSeq-1]); 290 FSE_initCState2(&stateLitLength, CTable_LitLength, llCodeTable[nbSeq-1]); 291 BIT_addBits(&blockStream, sequences[nbSeq-1].litLength, LL_bits[llCodeTable[nbSeq-1]]); 292 if (MEM_32bits()) BIT_flushBits(&blockStream); 293 BIT_addBits(&blockStream, sequences[nbSeq-1].matchLength, ML_bits[mlCodeTable[nbSeq-1]]); 294 if (MEM_32bits()) BIT_flushBits(&blockStream); 295 if (longOffsets) { 296 U32 const ofBits = ofCodeTable[nbSeq-1]; 297 unsigned const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN-1); 298 if (extraBits) { 299 BIT_addBits(&blockStream, sequences[nbSeq-1].offset, extraBits); 300 BIT_flushBits(&blockStream); 301 } 302 BIT_addBits(&blockStream, sequences[nbSeq-1].offset >> extraBits, 303 ofBits - extraBits); 304 } else { 305 BIT_addBits(&blockStream, sequences[nbSeq-1].offset, ofCodeTable[nbSeq-1]); 306 } 307 BIT_flushBits(&blockStream); 308 309 { size_t n; 310 for (n=nbSeq-2 ; n<nbSeq ; n--) { /* intentional underflow */ 311 BYTE const llCode = llCodeTable[n]; 312 BYTE const ofCode = ofCodeTable[n]; 313 BYTE const mlCode = mlCodeTable[n]; 314 U32 const llBits = LL_bits[llCode]; 315 U32 const ofBits = ofCode; 316 U32 const mlBits = ML_bits[mlCode]; 317 DEBUGLOG(6, "encoding: litlen:%2u - matchlen:%2u - offCode:%7u", 318 (unsigned)sequences[n].litLength, 319 (unsigned)sequences[n].matchLength + MINMATCH, 320 (unsigned)sequences[n].offset); 321 /* 32b*/ /* 64b*/ 322 /* (7)*/ /* (7)*/ 323 FSE_encodeSymbol(&blockStream, &stateOffsetBits, ofCode); /* 15 */ /* 15 */ 324 FSE_encodeSymbol(&blockStream, &stateMatchLength, mlCode); /* 24 */ /* 24 */ 325 if (MEM_32bits()) BIT_flushBits(&blockStream); /* (7)*/ 326 FSE_encodeSymbol(&blockStream, &stateLitLength, llCode); /* 16 */ /* 33 */ 327 if (MEM_32bits() || (ofBits+mlBits+llBits >= 64-7-(LLFSELog+MLFSELog+OffFSELog))) 328 BIT_flushBits(&blockStream); /* (7)*/ 329 BIT_addBits(&blockStream, sequences[n].litLength, llBits); 330 if (MEM_32bits() && ((llBits+mlBits)>24)) BIT_flushBits(&blockStream); 331 BIT_addBits(&blockStream, sequences[n].matchLength, mlBits); 332 if (MEM_32bits() || (ofBits+mlBits+llBits > 56)) BIT_flushBits(&blockStream); 333 if (longOffsets) { 334 unsigned const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN-1); 335 if (extraBits) { 336 BIT_addBits(&blockStream, sequences[n].offset, extraBits); 337 BIT_flushBits(&blockStream); /* (7)*/ 338 } 339 BIT_addBits(&blockStream, sequences[n].offset >> extraBits, 340 ofBits - extraBits); /* 31 */ 341 } else { 342 BIT_addBits(&blockStream, sequences[n].offset, ofBits); /* 31 */ 343 } 344 BIT_flushBits(&blockStream); /* (7)*/ 345 DEBUGLOG(7, "remaining space : %i", (int)(blockStream.endPtr - blockStream.ptr)); 346 } } 347 348 DEBUGLOG(6, "ZSTD_encodeSequences: flushing ML state with %u bits", stateMatchLength.stateLog); 349 FSE_flushCState(&blockStream, &stateMatchLength); 350 DEBUGLOG(6, "ZSTD_encodeSequences: flushing Off state with %u bits", stateOffsetBits.stateLog); 351 FSE_flushCState(&blockStream, &stateOffsetBits); 352 DEBUGLOG(6, "ZSTD_encodeSequences: flushing LL state with %u bits", stateLitLength.stateLog); 353 FSE_flushCState(&blockStream, &stateLitLength); 354 355 { size_t const streamSize = BIT_closeCStream(&blockStream); 356 RETURN_ERROR_IF(streamSize==0, dstSize_tooSmall, "not enough space"); 357 return streamSize; 358 } 359 } 360 361 static size_t 362 ZSTD_encodeSequences_default( 363 void* dst, size_t dstCapacity, 364 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 365 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 366 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 367 seqDef const* sequences, size_t nbSeq, int longOffsets) 368 { 369 return ZSTD_encodeSequences_body(dst, dstCapacity, 370 CTable_MatchLength, mlCodeTable, 371 CTable_OffsetBits, ofCodeTable, 372 CTable_LitLength, llCodeTable, 373 sequences, nbSeq, longOffsets); 374 } 375 376 377 #if DYNAMIC_BMI2 378 379 static TARGET_ATTRIBUTE("bmi2") size_t 380 ZSTD_encodeSequences_bmi2( 381 void* dst, size_t dstCapacity, 382 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 383 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 384 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 385 seqDef const* sequences, size_t nbSeq, int longOffsets) 386 { 387 return ZSTD_encodeSequences_body(dst, dstCapacity, 388 CTable_MatchLength, mlCodeTable, 389 CTable_OffsetBits, ofCodeTable, 390 CTable_LitLength, llCodeTable, 391 sequences, nbSeq, longOffsets); 392 } 393 394 #endif 395 396 size_t ZSTD_encodeSequences( 397 void* dst, size_t dstCapacity, 398 FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, 399 FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, 400 FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, 401 seqDef const* sequences, size_t nbSeq, int longOffsets, int bmi2) 402 { 403 DEBUGLOG(5, "ZSTD_encodeSequences: dstCapacity = %u", (unsigned)dstCapacity); 404 #if DYNAMIC_BMI2 405 if (bmi2) { 406 return ZSTD_encodeSequences_bmi2(dst, dstCapacity, 407 CTable_MatchLength, mlCodeTable, 408 CTable_OffsetBits, ofCodeTable, 409 CTable_LitLength, llCodeTable, 410 sequences, nbSeq, longOffsets); 411 } 412 #endif 413 (void)bmi2; 414 return ZSTD_encodeSequences_default(dst, dstCapacity, 415 CTable_MatchLength, mlCodeTable, 416 CTable_OffsetBits, ofCodeTable, 417 CTable_LitLength, llCodeTable, 418 sequences, nbSeq, longOffsets); 419 }
Cache object: ea3ec003e52e12137d81970be5af4bae
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