/* * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc. * All rights reserved. * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). * You may select, at your option, one of the above-listed licenses. */ /*-************************************* * Dependencies ***************************************/ #include "zstd_compress_sequences.h" /** * -log2(x / 256) lookup table for x in [0, 256). * If x == 0: Return 0 * Else: Return floor(-log2(x / 256) * 256) */ static unsigned const kInverseProbabilityLog256[256] = { 0, 2048, 1792, 1642, 1536, 1453, 1386, 1329, 1280, 1236, 1197, 1162, 1130, 1100, 1073, 1047, 1024, 1001, 980, 960, 941, 923, 906, 889, 874, 859, 844, 830, 817, 804, 791, 779, 768, 756, 745, 734, 724, 714, 704, 694, 685, 676, 667, 658, 650, 642, 633, 626, 618, 610, 603, 595, 588, 581, 574, 567, 561, 554, 548, 542, 535, 529, 523, 517, 512, 506, 500, 495, 489, 484, 478, 473, 468, 463, 458, 453, 448, 443, 438, 434, 429, 424, 420, 415, 411, 407, 402, 398, 394, 390, 386, 382, 377, 373, 370, 366, 362, 358, 354, 350, 347, 343, 339, 336, 332, 329, 325, 322, 318, 315, 311, 308, 305, 302, 298, 295, 292, 289, 286, 282, 279, 276, 273, 270, 267, 264, 261, 258, 256, 253, 250, 247, 244, 241, 239, 236, 233, 230, 228, 225, 222, 220, 217, 215, 212, 209, 207, 204, 202, 199, 197, 194, 192, 190, 187, 185, 182, 180, 178, 175, 173, 171, 168, 166, 164, 162, 159, 157, 155, 153, 151, 149, 146, 144, 142, 140, 138, 136, 134, 132, 130, 128, 126, 123, 121, 119, 117, 115, 114, 112, 110, 108, 106, 104, 102, 100, 98, 96, 94, 93, 91, 89, 87, 85, 83, 82, 80, 78, 76, 74, 73, 71, 69, 67, 66, 64, 62, 61, 59, 57, 55, 54, 52, 50, 49, 47, 46, 44, 42, 41, 39, 37, 36, 34, 33, 31, 30, 28, 26, 25, 23, 22, 20, 19, 17, 16, 14, 13, 11, 10, 8, 7, 5, 4, 2, 1, }; static unsigned ZSTD_getFSEMaxSymbolValue(FSE_CTable const* ctable) { void const* ptr = ctable; U16 const* u16ptr = (U16 const*)ptr; U32 const maxSymbolValue = MEM_read16(u16ptr + 1); return maxSymbolValue; } /** * Returns the cost in bytes of encoding the normalized count header. * Returns an error if any of the helper functions return an error. */ static size_t ZSTD_NCountCost(unsigned const* count, unsigned const max, size_t const nbSeq, unsigned const FSELog) { BYTE wksp[FSE_NCOUNTBOUND]; S16 norm[MaxSeq + 1]; const U32 tableLog = FSE_optimalTableLog(FSELog, nbSeq, max); FORWARD_IF_ERROR(FSE_normalizeCount(norm, tableLog, count, nbSeq, max), ""); return FSE_writeNCount(wksp, sizeof(wksp), norm, max, tableLog); } /** * Returns the cost in bits of encoding the distribution described by count * using the entropy bound. */ static size_t ZSTD_entropyCost(unsigned const* count, unsigned const max, size_t const total) { unsigned cost = 0; unsigned s; for (s = 0; s <= max; ++s) { unsigned norm = (unsigned)((256 * count[s]) / total); if (count[s] != 0 && norm == 0) norm = 1; assert(count[s] < total); cost += count[s] * kInverseProbabilityLog256[norm]; } return cost >> 8; } /** * Returns the cost in bits of encoding the distribution in count using ctable. * Returns an error if ctable cannot represent all the symbols in count. */ size_t ZSTD_fseBitCost( FSE_CTable const* ctable, unsigned const* count, unsigned const max) { unsigned const kAccuracyLog = 8; size_t cost = 0; unsigned s; FSE_CState_t cstate; FSE_initCState(&cstate, ctable); if (ZSTD_getFSEMaxSymbolValue(ctable) < max) { DEBUGLOG(5, "Repeat FSE_CTable has maxSymbolValue %u < %u", ZSTD_getFSEMaxSymbolValue(ctable), max); return ERROR(GENERIC); } for (s = 0; s <= max; ++s) { unsigned const tableLog = cstate.stateLog; unsigned const badCost = (tableLog + 1) << kAccuracyLog; unsigned const bitCost = FSE_bitCost(cstate.symbolTT, tableLog, s, kAccuracyLog); if (count[s] == 0) continue; if (bitCost >= badCost) { DEBUGLOG(5, "Repeat FSE_CTable has Prob[%u] == 0", s); return ERROR(GENERIC); } cost += (size_t)count[s] * bitCost; } return cost >> kAccuracyLog; } /** * Returns the cost in bits of encoding the distribution in count using the * table described by norm. The max symbol support by norm is assumed >= max. * norm must be valid for every symbol with non-zero probability in count. */ size_t ZSTD_crossEntropyCost(short const* norm, unsigned accuracyLog, unsigned const* count, unsigned const max) { unsigned const shift = 8 - accuracyLog; size_t cost = 0; unsigned s; assert(accuracyLog <= 8); for (s = 0; s <= max; ++s) { unsigned const normAcc = (norm[s] != -1) ? (unsigned)norm[s] : 1; unsigned const norm256 = normAcc << shift; assert(norm256 > 0); assert(norm256 < 256); cost += count[s] * kInverseProbabilityLog256[norm256]; } return cost >> 8; } symbolEncodingType_e ZSTD_selectEncodingType( FSE_repeat* repeatMode, unsigned const* count, unsigned const max, size_t const mostFrequent, size_t nbSeq, unsigned const FSELog, FSE_CTable const* prevCTable, short const* defaultNorm, U32 defaultNormLog, ZSTD_defaultPolicy_e const isDefaultAllowed, ZSTD_strategy const strategy) { ZSTD_STATIC_ASSERT(ZSTD_defaultDisallowed == 0 && ZSTD_defaultAllowed != 0); if (mostFrequent == nbSeq) { *repeatMode = FSE_repeat_none; if (isDefaultAllowed && nbSeq <= 2) { /* Prefer set_basic over set_rle when there are 2 or less symbols, * since RLE uses 1 byte, but set_basic uses 5-6 bits per symbol. * If basic encoding isn't possible, always choose RLE. */ DEBUGLOG(5, "Selected set_basic"); return set_basic; } DEBUGLOG(5, "Selected set_rle"); return set_rle; } if (strategy < ZSTD_lazy) { if (isDefaultAllowed) { size_t const staticFse_nbSeq_max = 1000; size_t const mult = 10 - strategy; size_t const baseLog = 3; size_t const dynamicFse_nbSeq_min = (((size_t)1 << defaultNormLog) * mult) >> baseLog; /* 28-36 for offset, 56-72 for lengths */ assert(defaultNormLog >= 5 && defaultNormLog <= 6); /* xx_DEFAULTNORMLOG */ assert(mult <= 9 && mult >= 7); if ( (*repeatMode == FSE_repeat_valid) && (nbSeq < staticFse_nbSeq_max) ) { DEBUGLOG(5, "Selected set_repeat"); return set_repeat; } if ( (nbSeq < dynamicFse_nbSeq_min) || (mostFrequent < (nbSeq >> (defaultNormLog-1))) ) { DEBUGLOG(5, "Selected set_basic"); /* The format allows default tables to be repeated, but it isn't useful. * When using simple heuristics to select encoding type, we don't want * to confuse these tables with dictionaries. When running more careful * analysis, we don't need to waste time checking both repeating tables * and default tables. */ *repeatMode = FSE_repeat_none; return set_basic; } } } else { size_t const basicCost = isDefaultAllowed ? ZSTD_crossEntropyCost(defaultNorm, defaultNormLog, count, max) : ERROR(GENERIC); size_t const repeatCost = *repeatMode != FSE_repeat_none ? ZSTD_fseBitCost(prevCTable, count, max) : ERROR(GENERIC); size_t const NCountCost = ZSTD_NCountCost(count, max, nbSeq, FSELog); size_t const compressedCost = (NCountCost << 3) + ZSTD_entropyCost(count, max, nbSeq); if (isDefaultAllowed) { assert(!ZSTD_isError(basicCost)); assert(!(*repeatMode == FSE_repeat_valid && ZSTD_isError(repeatCost))); } assert(!ZSTD_isError(NCountCost)); assert(compressedCost < ERROR(maxCode)); DEBUGLOG(5, "Estimated bit costs: basic=%u\trepeat=%u\tcompressed=%u", (unsigned)basicCost, (unsigned)repeatCost, (unsigned)compressedCost); if (basicCost <= repeatCost && basicCost <= compressedCost) { DEBUGLOG(5, "Selected set_basic"); assert(isDefaultAllowed); *repeatMode = FSE_repeat_none; return set_basic; } if (repeatCost <= compressedCost) { DEBUGLOG(5, "Selected set_repeat"); assert(!ZSTD_isError(repeatCost)); return set_repeat; } assert(compressedCost < basicCost && compressedCost < repeatCost); } DEBUGLOG(5, "Selected set_compressed"); *repeatMode = FSE_repeat_check; return set_compressed; } size_t ZSTD_buildCTable(void* dst, size_t dstCapacity, FSE_CTable* nextCTable, U32 FSELog, symbolEncodingType_e type, unsigned* count, U32 max, const BYTE* codeTable, size_t nbSeq, const S16* defaultNorm, U32 defaultNormLog, U32 defaultMax, const FSE_CTable* prevCTable, size_t prevCTableSize, void* entropyWorkspace, size_t entropyWorkspaceSize) { BYTE* op = (BYTE*)dst; const BYTE* const oend = op + dstCapacity; DEBUGLOG(6, "ZSTD_buildCTable (dstCapacity=%u)", (unsigned)dstCapacity); switch (type) { case set_rle: FORWARD_IF_ERROR(FSE_buildCTable_rle(nextCTable, (BYTE)max), ""); RETURN_ERROR_IF(dstCapacity==0, dstSize_tooSmall, "not enough space"); *op = codeTable[0]; return 1; case set_repeat: memcpy(nextCTable, prevCTable, prevCTableSize); return 0; case set_basic: FORWARD_IF_ERROR(FSE_buildCTable_wksp(nextCTable, defaultNorm, defaultMax, defaultNormLog, entropyWorkspace, entropyWorkspaceSize), ""); /* note : could be pre-calculated */ return 0; case set_compressed: { S16 norm[MaxSeq + 1]; size_t nbSeq_1 = nbSeq; const U32 tableLog = FSE_optimalTableLog(FSELog, nbSeq, max); if (count[codeTable[nbSeq-1]] > 1) { count[codeTable[nbSeq-1]]--; nbSeq_1--; } assert(nbSeq_1 > 1); FORWARD_IF_ERROR(FSE_normalizeCount(norm, tableLog, count, nbSeq_1, max), ""); { size_t const NCountSize = FSE_writeNCount(op, oend - op, norm, max, tableLog); /* overflow protected */ FORWARD_IF_ERROR(NCountSize, "FSE_writeNCount failed"); FORWARD_IF_ERROR(FSE_buildCTable_wksp(nextCTable, norm, max, tableLog, entropyWorkspace, entropyWorkspaceSize), ""); return NCountSize; } } default: assert(0); RETURN_ERROR(GENERIC, "impossible to reach"); } } FORCE_INLINE_TEMPLATE size_t ZSTD_encodeSequences_body( void* dst, size_t dstCapacity, FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, seqDef const* sequences, size_t nbSeq, int longOffsets) { BIT_CStream_t blockStream; FSE_CState_t stateMatchLength; FSE_CState_t stateOffsetBits; FSE_CState_t stateLitLength; RETURN_ERROR_IF( ERR_isError(BIT_initCStream(&blockStream, dst, dstCapacity)), dstSize_tooSmall, "not enough space remaining"); DEBUGLOG(6, "available space for bitstream : %i (dstCapacity=%u)", (int)(blockStream.endPtr - blockStream.startPtr), (unsigned)dstCapacity); /* first symbols */ FSE_initCState2(&stateMatchLength, CTable_MatchLength, mlCodeTable[nbSeq-1]); FSE_initCState2(&stateOffsetBits, CTable_OffsetBits, ofCodeTable[nbSeq-1]); FSE_initCState2(&stateLitLength, CTable_LitLength, llCodeTable[nbSeq-1]); BIT_addBits(&blockStream, sequences[nbSeq-1].litLength, LL_bits[llCodeTable[nbSeq-1]]); if (MEM_32bits()) BIT_flushBits(&blockStream); BIT_addBits(&blockStream, sequences[nbSeq-1].matchLength, ML_bits[mlCodeTable[nbSeq-1]]); if (MEM_32bits()) BIT_flushBits(&blockStream); if (longOffsets) { U32 const ofBits = ofCodeTable[nbSeq-1]; unsigned const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN-1); if (extraBits) { BIT_addBits(&blockStream, sequences[nbSeq-1].offset, extraBits); BIT_flushBits(&blockStream); } BIT_addBits(&blockStream, sequences[nbSeq-1].offset >> extraBits, ofBits - extraBits); } else { BIT_addBits(&blockStream, sequences[nbSeq-1].offset, ofCodeTable[nbSeq-1]); } BIT_flushBits(&blockStream); { size_t n; for (n=nbSeq-2 ; n= 64-7-(LLFSELog+MLFSELog+OffFSELog))) BIT_flushBits(&blockStream); /* (7)*/ BIT_addBits(&blockStream, sequences[n].litLength, llBits); if (MEM_32bits() && ((llBits+mlBits)>24)) BIT_flushBits(&blockStream); BIT_addBits(&blockStream, sequences[n].matchLength, mlBits); if (MEM_32bits() || (ofBits+mlBits+llBits > 56)) BIT_flushBits(&blockStream); if (longOffsets) { unsigned const extraBits = ofBits - MIN(ofBits, STREAM_ACCUMULATOR_MIN-1); if (extraBits) { BIT_addBits(&blockStream, sequences[n].offset, extraBits); BIT_flushBits(&blockStream); /* (7)*/ } BIT_addBits(&blockStream, sequences[n].offset >> extraBits, ofBits - extraBits); /* 31 */ } else { BIT_addBits(&blockStream, sequences[n].offset, ofBits); /* 31 */ } BIT_flushBits(&blockStream); /* (7)*/ DEBUGLOG(7, "remaining space : %i", (int)(blockStream.endPtr - blockStream.ptr)); } } DEBUGLOG(6, "ZSTD_encodeSequences: flushing ML state with %u bits", stateMatchLength.stateLog); FSE_flushCState(&blockStream, &stateMatchLength); DEBUGLOG(6, "ZSTD_encodeSequences: flushing Off state with %u bits", stateOffsetBits.stateLog); FSE_flushCState(&blockStream, &stateOffsetBits); DEBUGLOG(6, "ZSTD_encodeSequences: flushing LL state with %u bits", stateLitLength.stateLog); FSE_flushCState(&blockStream, &stateLitLength); { size_t const streamSize = BIT_closeCStream(&blockStream); RETURN_ERROR_IF(streamSize==0, dstSize_tooSmall, "not enough space"); return streamSize; } } static size_t ZSTD_encodeSequences_default( void* dst, size_t dstCapacity, FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, seqDef const* sequences, size_t nbSeq, int longOffsets) { return ZSTD_encodeSequences_body(dst, dstCapacity, CTable_MatchLength, mlCodeTable, CTable_OffsetBits, ofCodeTable, CTable_LitLength, llCodeTable, sequences, nbSeq, longOffsets); } #if DYNAMIC_BMI2 static TARGET_ATTRIBUTE("bmi2") size_t ZSTD_encodeSequences_bmi2( void* dst, size_t dstCapacity, FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, seqDef const* sequences, size_t nbSeq, int longOffsets) { return ZSTD_encodeSequences_body(dst, dstCapacity, CTable_MatchLength, mlCodeTable, CTable_OffsetBits, ofCodeTable, CTable_LitLength, llCodeTable, sequences, nbSeq, longOffsets); } #endif size_t ZSTD_encodeSequences( void* dst, size_t dstCapacity, FSE_CTable const* CTable_MatchLength, BYTE const* mlCodeTable, FSE_CTable const* CTable_OffsetBits, BYTE const* ofCodeTable, FSE_CTable const* CTable_LitLength, BYTE const* llCodeTable, seqDef const* sequences, size_t nbSeq, int longOffsets, int bmi2) { DEBUGLOG(5, "ZSTD_encodeSequences: dstCapacity = %u", (unsigned)dstCapacity); #if DYNAMIC_BMI2 if (bmi2) { return ZSTD_encodeSequences_bmi2(dst, dstCapacity, CTable_MatchLength, mlCodeTable, CTable_OffsetBits, ofCodeTable, CTable_LitLength, llCodeTable, sequences, nbSeq, longOffsets); } #endif (void)bmi2; return ZSTD_encodeSequences_default(dst, dstCapacity, CTable_MatchLength, mlCodeTable, CTable_OffsetBits, ofCodeTable, CTable_LitLength, llCodeTable, sequences, nbSeq, longOffsets); }