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fse_decompress.c
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linux-6.19.14/lib/zstd/common/fse_decompress.c
1// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause 2/* ****************************************************************** 3 * FSE : Finite State Entropy decoder 4 * Copyright (c) Meta Platforms, Inc. and affiliates. 5 * 6 * You can contact the author at : 7 * - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy 8 * - Public forum : https://groups.google.com/forum/#!forum/lz4c 9 * 10 * This source code is licensed under both the BSD-style license (found in the 11 * LICENSE file in the root directory of this source tree) and the GPLv2 (found 12 * in the COPYING file in the root directory of this source tree). 13 * You may select, at your option, one of the above-listed licenses. 14****************************************************************** */ 15 16 17/* ************************************************************** 18* Includes 19****************************************************************/ 20#include "debug.h" /* assert */ 21#include "bitstream.h" 22#include "compiler.h" 23#define FSE_STATIC_LINKING_ONLY 24#include "fse.h" 25#include "error_private.h" 26#include "zstd_deps.h" /* ZSTD_memcpy */ 27#include "bits.h" /* ZSTD_highbit32 */ 28 29 30/* ************************************************************** 31* Error Management 32****************************************************************/ 33#define FSE_isError ERR_isError 34#define FSE_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c) /* use only *after* variable declarations */ 35 36 37/* ************************************************************** 38* Templates 39****************************************************************/ 40/* 41 designed to be included 42 for type-specific functions (template emulation in C) 43 Objective is to write these functions only once, for improved maintenance 44*/ 45 46/* safety checks */ 47#ifndef FSE_FUNCTION_EXTENSION 48# error "FSE_FUNCTION_EXTENSION must be defined" 49#endif 50#ifndef FSE_FUNCTION_TYPE 51# error "FSE_FUNCTION_TYPE must be defined" 52#endif 53 54/* Function names */ 55#define FSE_CAT(X,Y) X##Y 56#define FSE_FUNCTION_NAME(X,Y) FSE_CAT(X,Y) 57#define FSE_TYPE_NAME(X,Y) FSE_CAT(X,Y) 58 59static size_t FSE_buildDTable_internal(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize) 60{ 61 void* const tdPtr = dt+1; /* because *dt is unsigned, 32-bits aligned on 32-bits */ 62 FSE_DECODE_TYPE* const tableDecode = (FSE_DECODE_TYPE*) (tdPtr); 63 U16* symbolNext = (U16*)workSpace; 64 BYTE* spread = (BYTE*)(symbolNext + maxSymbolValue + 1); 65 66 U32 const maxSV1 = maxSymbolValue + 1; 67 U32 const tableSize = 1 << tableLog; 68 U32 highThreshold = tableSize-1; 69 70 /* Sanity Checks */ 71 if (FSE_BUILD_DTABLE_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(maxSymbolValue_tooLarge); 72 if (maxSymbolValue > FSE_MAX_SYMBOL_VALUE) return ERROR(maxSymbolValue_tooLarge); 73 if (tableLog > FSE_MAX_TABLELOG) return ERROR(tableLog_tooLarge); 74 75 /* Init, lay down lowprob symbols */ 76 { FSE_DTableHeader DTableH; 77 DTableH.tableLog = (U16)tableLog; 78 DTableH.fastMode = 1; 79 { S16 const largeLimit= (S16)(1 << (tableLog-1)); 80 U32 s; 81 for (s=0; s<maxSV1; s++) { 82 if (normalizedCounter[s]==-1) { 83 tableDecode[highThreshold--].symbol = (FSE_FUNCTION_TYPE)s; 84 symbolNext[s] = 1; 85 } else { 86 if (normalizedCounter[s] >= largeLimit) DTableH.fastMode=0; 87 symbolNext[s] = (U16)normalizedCounter[s]; 88 } } } 89 ZSTD_memcpy(dt, &DTableH, sizeof(DTableH)); 90 } 91 92 /* Spread symbols */ 93 if (highThreshold == tableSize - 1) { 94 size_t const tableMask = tableSize-1; 95 size_t const step = FSE_TABLESTEP(tableSize); 96 /* First lay down the symbols in order. 97 * We use a uint64_t to lay down 8 bytes at a time. This reduces branch 98 * misses since small blocks generally have small table logs, so nearly 99 * all symbols have counts <= 8. We ensure we have 8 bytes at the end of 100 * our buffer to handle the over-write. 101 */ 102 { U64 const add = 0x0101010101010101ull; 103 size_t pos = 0; 104 U64 sv = 0; 105 U32 s; 106 for (s=0; s<maxSV1; ++s, sv += add) { 107 int i; 108 int const n = normalizedCounter[s]; 109 MEM_write64(spread + pos, sv); 110 for (i = 8; i < n; i += 8) { 111 MEM_write64(spread + pos + i, sv); 112 } 113 pos += (size_t)n; 114 } } 115 /* Now we spread those positions across the table. 116 * The benefit of doing it in two stages is that we avoid the 117 * variable size inner loop, which caused lots of branch misses. 118 * Now we can run through all the positions without any branch misses. 119 * We unroll the loop twice, since that is what empirically worked best. 120 */ 121 { 122 size_t position = 0; 123 size_t s; 124 size_t const unroll = 2; 125 assert(tableSize % unroll == 0); /* FSE_MIN_TABLELOG is 5 */ 126 for (s = 0; s < (size_t)tableSize; s += unroll) { 127 size_t u; 128 for (u = 0; u < unroll; ++u) { 129 size_t const uPosition = (position + (u * step)) & tableMask; 130 tableDecode[uPosition].symbol = spread[s + u]; 131 } 132 position = (position + (unroll * step)) & tableMask; 133 } 134 assert(position == 0); 135 } 136 } else { 137 U32 const tableMask = tableSize-1; 138 U32 const step = FSE_TABLESTEP(tableSize); 139 U32 s, position = 0; 140 for (s=0; s<maxSV1; s++) { 141 int i; 142 for (i=0; i<normalizedCounter[s]; i++) { 143 tableDecode[position].symbol = (FSE_FUNCTION_TYPE)s; 144 position = (position + step) & tableMask; 145 while (position > highThreshold) position = (position + step) & tableMask; /* lowprob area */ 146 } } 147 if (position!=0) return ERROR(GENERIC); /* position must reach all cells once, otherwise normalizedCounter is incorrect */ 148 } 149 150 /* Build Decoding table */ 151 { U32 u; 152 for (u=0; u<tableSize; u++) { 153 FSE_FUNCTION_TYPE const symbol = (FSE_FUNCTION_TYPE)(tableDecode[u].symbol); 154 U32 const nextState = symbolNext[symbol]++; 155 tableDecode[u].nbBits = (BYTE) (tableLog - ZSTD_highbit32(nextState) ); 156 tableDecode[u].newState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize); 157 } } 158 159 return 0; 160} 161 162size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize) 163{ 164 return FSE_buildDTable_internal(dt, normalizedCounter, maxSymbolValue, tableLog, workSpace, wkspSize); 165} 166 167 168#ifndef FSE_COMMONDEFS_ONLY 169 170/*-******************************************************* 171* Decompression (Byte symbols) 172*********************************************************/ 173 174FORCE_INLINE_TEMPLATE size_t FSE_decompress_usingDTable_generic( 175 void* dst, size_t maxDstSize, 176 const void* cSrc, size_t cSrcSize, 177 const FSE_DTable* dt, const unsigned fast) 178{ 179 BYTE* const ostart = (BYTE*) dst; 180 BYTE* op = ostart; 181 BYTE* const omax = op + maxDstSize; 182 BYTE* const olimit = omax-3; 183 184 BIT_DStream_t bitD; 185 FSE_DState_t state1; 186 FSE_DState_t state2; 187 188 /* Init */ 189 CHECK_F(BIT_initDStream(&bitD, cSrc, cSrcSize)); 190 191 FSE_initDState(&state1, &bitD, dt); 192 FSE_initDState(&state2, &bitD, dt); 193 194 RETURN_ERROR_IF(BIT_reloadDStream(&bitD)==BIT_DStream_overflow, corruption_detected, ""); 195 196#define FSE_GETSYMBOL(statePtr) fast ? FSE_decodeSymbolFast(statePtr, &bitD) : FSE_decodeSymbol(statePtr, &bitD) 197 198 /* 4 symbols per loop */ 199 for ( ; (BIT_reloadDStream(&bitD)==BIT_DStream_unfinished) & (op<olimit) ; op+=4) { 200 op[0] = FSE_GETSYMBOL(&state1); 201 202 if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */ 203 BIT_reloadDStream(&bitD); 204 205 op[1] = FSE_GETSYMBOL(&state2); 206 207 if (FSE_MAX_TABLELOG*4+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */ 208 { if (BIT_reloadDStream(&bitD) > BIT_DStream_unfinished) { op+=2; break; } } 209 210 op[2] = FSE_GETSYMBOL(&state1); 211 212 if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */ 213 BIT_reloadDStream(&bitD); 214 215 op[3] = FSE_GETSYMBOL(&state2); 216 } 217 218 /* tail */ 219 /* note : BIT_reloadDStream(&bitD) >= FSE_DStream_partiallyFilled; Ends at exactly BIT_DStream_completed */ 220 while (1) { 221 if (op>(omax-2)) return ERROR(dstSize_tooSmall); 222 *op++ = FSE_GETSYMBOL(&state1); 223 if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) { 224 *op++ = FSE_GETSYMBOL(&state2); 225 break; 226 } 227 228 if (op>(omax-2)) return ERROR(dstSize_tooSmall); 229 *op++ = FSE_GETSYMBOL(&state2); 230 if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) { 231 *op++ = FSE_GETSYMBOL(&state1); 232 break; 233 } } 234 235 assert(op >= ostart); 236 return (size_t)(op-ostart); 237} 238 239typedef struct { 240 short ncount[FSE_MAX_SYMBOL_VALUE + 1]; 241} FSE_DecompressWksp; 242 243 244FORCE_INLINE_TEMPLATE size_t FSE_decompress_wksp_body( 245 void* dst, size_t dstCapacity, 246 const void* cSrc, size_t cSrcSize, 247 unsigned maxLog, void* workSpace, size_t wkspSize, 248 int bmi2) 249{ 250 const BYTE* const istart = (const BYTE*)cSrc; 251 const BYTE* ip = istart; 252 unsigned tableLog; 253 unsigned maxSymbolValue = FSE_MAX_SYMBOL_VALUE; 254 FSE_DecompressWksp* const wksp = (FSE_DecompressWksp*)workSpace; 255 size_t const dtablePos = sizeof(FSE_DecompressWksp) / sizeof(FSE_DTable); 256 FSE_DTable* const dtable = (FSE_DTable*)workSpace + dtablePos; 257 258 FSE_STATIC_ASSERT((FSE_MAX_SYMBOL_VALUE + 1) % 2 == 0); 259 if (wkspSize < sizeof(*wksp)) return ERROR(GENERIC); 260 261 /* correct offset to dtable depends on this property */ 262 FSE_STATIC_ASSERT(sizeof(FSE_DecompressWksp) % sizeof(FSE_DTable) == 0); 263 264 /* normal FSE decoding mode */ 265 { size_t const NCountLength = 266 FSE_readNCount_bmi2(wksp->ncount, &maxSymbolValue, &tableLog, istart, cSrcSize, bmi2); 267 if (FSE_isError(NCountLength)) return NCountLength; 268 if (tableLog > maxLog) return ERROR(tableLog_tooLarge); 269 assert(NCountLength <= cSrcSize); 270 ip += NCountLength; 271 cSrcSize -= NCountLength; 272 } 273 274 if (FSE_DECOMPRESS_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(tableLog_tooLarge); 275 assert(sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog) <= wkspSize); 276 workSpace = (BYTE*)workSpace + sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog); 277 wkspSize -= sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog); 278 279 CHECK_F( FSE_buildDTable_internal(dtable, wksp->ncount, maxSymbolValue, tableLog, workSpace, wkspSize) ); 280 281 { 282 const void* ptr = dtable; 283 const FSE_DTableHeader* DTableH = (const FSE_DTableHeader*)ptr; 284 const U32 fastMode = DTableH->fastMode; 285 286 /* select fast mode (static) */ 287 if (fastMode) return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 1); 288 return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 0); 289 } 290} 291 292/* Avoids the FORCE_INLINE of the _body() function. */ 293static size_t FSE_decompress_wksp_body_default(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize) 294{ 295 return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 0); 296} 297 298#if DYNAMIC_BMI2 299BMI2_TARGET_ATTRIBUTE static size_t FSE_decompress_wksp_body_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize) 300{ 301 return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 1); 302} 303#endif 304 305size_t FSE_decompress_wksp_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize, int bmi2) 306{ 307#if DYNAMIC_BMI2 308 if (bmi2) { 309 return FSE_decompress_wksp_body_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize); 310 } 311#endif 312 (void)bmi2; 313 return FSE_decompress_wksp_body_default(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize); 314} 315 316#endif /* FSE_COMMONDEFS_ONLY */
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