314 lines
12 KiB
C
314 lines
12 KiB
C
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/* ******************************************************************
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* FSE : Finite State Entropy decoder
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* You can contact the author at :
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* - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy
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* - Public forum : https://groups.google.com/forum/#!forum/lz4c
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*
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* This source code is licensed under both the BSD-style license (found in the
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* LICENSE file in the root directory of this source tree) and the GPLv2 (found
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* in the COPYING file in the root directory of this source tree).
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* You may select, at your option, one of the above-listed licenses.
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****************************************************************** */
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/* **************************************************************
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* Includes
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****************************************************************/
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#include "debug.h" /* assert */
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#include "bitstream.h"
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#include "compiler.h"
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#define FSE_STATIC_LINKING_ONLY
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#include "fse.h"
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#include "error_private.h"
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#include "zstd_deps.h" /* ZSTD_memcpy */
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#include "bits.h" /* ZSTD_highbit32 */
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/* **************************************************************
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* Error Management
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****************************************************************/
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#define FSE_isError ERR_isError
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#define FSE_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c) /* use only *after* variable declarations */
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/* **************************************************************
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* Templates
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****************************************************************/
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/*
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designed to be included
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for type-specific functions (template emulation in C)
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Objective is to write these functions only once, for improved maintenance
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*/
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/* safety checks */
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#ifndef FSE_FUNCTION_EXTENSION
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# error "FSE_FUNCTION_EXTENSION must be defined"
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#endif
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#ifndef FSE_FUNCTION_TYPE
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# error "FSE_FUNCTION_TYPE must be defined"
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#endif
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/* Function names */
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#define FSE_CAT(X,Y) X##Y
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#define FSE_FUNCTION_NAME(X,Y) FSE_CAT(X,Y)
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#define FSE_TYPE_NAME(X,Y) FSE_CAT(X,Y)
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static size_t FSE_buildDTable_internal(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize)
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{
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void* const tdPtr = dt+1; /* because *dt is unsigned, 32-bits aligned on 32-bits */
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FSE_DECODE_TYPE* const tableDecode = (FSE_DECODE_TYPE*) (tdPtr);
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U16* symbolNext = (U16*)workSpace;
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BYTE* spread = (BYTE*)(symbolNext + maxSymbolValue + 1);
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U32 const maxSV1 = maxSymbolValue + 1;
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U32 const tableSize = 1 << tableLog;
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U32 highThreshold = tableSize-1;
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/* Sanity Checks */
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if (FSE_BUILD_DTABLE_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(maxSymbolValue_tooLarge);
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if (maxSymbolValue > FSE_MAX_SYMBOL_VALUE) return ERROR(maxSymbolValue_tooLarge);
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if (tableLog > FSE_MAX_TABLELOG) return ERROR(tableLog_tooLarge);
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/* Init, lay down lowprob symbols */
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{ FSE_DTableHeader DTableH;
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DTableH.tableLog = (U16)tableLog;
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DTableH.fastMode = 1;
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{ S16 const largeLimit= (S16)(1 << (tableLog-1));
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U32 s;
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for (s=0; s<maxSV1; s++) {
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if (normalizedCounter[s]==-1) {
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tableDecode[highThreshold--].symbol = (FSE_FUNCTION_TYPE)s;
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symbolNext[s] = 1;
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} else {
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if (normalizedCounter[s] >= largeLimit) DTableH.fastMode=0;
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symbolNext[s] = (U16)normalizedCounter[s];
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} } }
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ZSTD_memcpy(dt, &DTableH, sizeof(DTableH));
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}
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/* Spread symbols */
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if (highThreshold == tableSize - 1) {
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size_t const tableMask = tableSize-1;
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size_t const step = FSE_TABLESTEP(tableSize);
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/* First lay down the symbols in order.
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* We use a uint64_t to lay down 8 bytes at a time. This reduces branch
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* misses since small blocks generally have small table logs, so nearly
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* all symbols have counts <= 8. We ensure we have 8 bytes at the end of
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* our buffer to handle the over-write.
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*/
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{ U64 const add = 0x0101010101010101ull;
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size_t pos = 0;
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U64 sv = 0;
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U32 s;
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for (s=0; s<maxSV1; ++s, sv += add) {
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int i;
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int const n = normalizedCounter[s];
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MEM_write64(spread + pos, sv);
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for (i = 8; i < n; i += 8) {
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MEM_write64(spread + pos + i, sv);
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}
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pos += (size_t)n;
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} }
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/* Now we spread those positions across the table.
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* The benefit of doing it in two stages is that we avoid the
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* variable size inner loop, which caused lots of branch misses.
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* Now we can run through all the positions without any branch misses.
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* We unroll the loop twice, since that is what empirically worked best.
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*/
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{
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size_t position = 0;
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size_t s;
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size_t const unroll = 2;
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assert(tableSize % unroll == 0); /* FSE_MIN_TABLELOG is 5 */
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for (s = 0; s < (size_t)tableSize; s += unroll) {
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size_t u;
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for (u = 0; u < unroll; ++u) {
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size_t const uPosition = (position + (u * step)) & tableMask;
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tableDecode[uPosition].symbol = spread[s + u];
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}
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position = (position + (unroll * step)) & tableMask;
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}
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assert(position == 0);
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}
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} else {
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U32 const tableMask = tableSize-1;
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U32 const step = FSE_TABLESTEP(tableSize);
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U32 s, position = 0;
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for (s=0; s<maxSV1; s++) {
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int i;
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for (i=0; i<normalizedCounter[s]; i++) {
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tableDecode[position].symbol = (FSE_FUNCTION_TYPE)s;
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position = (position + step) & tableMask;
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while (position > highThreshold) position = (position + step) & tableMask; /* lowprob area */
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} }
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if (position!=0) return ERROR(GENERIC); /* position must reach all cells once, otherwise normalizedCounter is incorrect */
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}
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/* Build Decoding table */
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{ U32 u;
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for (u=0; u<tableSize; u++) {
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FSE_FUNCTION_TYPE const symbol = (FSE_FUNCTION_TYPE)(tableDecode[u].symbol);
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U32 const nextState = symbolNext[symbol]++;
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tableDecode[u].nbBits = (BYTE) (tableLog - ZSTD_highbit32(nextState) );
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tableDecode[u].newState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize);
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} }
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return 0;
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}
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size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize)
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{
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return FSE_buildDTable_internal(dt, normalizedCounter, maxSymbolValue, tableLog, workSpace, wkspSize);
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}
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#ifndef FSE_COMMONDEFS_ONLY
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/*-*******************************************************
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* Decompression (Byte symbols)
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*********************************************************/
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FORCE_INLINE_TEMPLATE size_t FSE_decompress_usingDTable_generic(
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void* dst, size_t maxDstSize,
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const void* cSrc, size_t cSrcSize,
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const FSE_DTable* dt, const unsigned fast)
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{
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BYTE* const ostart = (BYTE*) dst;
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BYTE* op = ostart;
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BYTE* const omax = op + maxDstSize;
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BYTE* const olimit = omax-3;
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BIT_DStream_t bitD;
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FSE_DState_t state1;
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FSE_DState_t state2;
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/* Init */
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CHECK_F(BIT_initDStream(&bitD, cSrc, cSrcSize));
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FSE_initDState(&state1, &bitD, dt);
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FSE_initDState(&state2, &bitD, dt);
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#define FSE_GETSYMBOL(statePtr) fast ? FSE_decodeSymbolFast(statePtr, &bitD) : FSE_decodeSymbol(statePtr, &bitD)
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/* 4 symbols per loop */
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for ( ; (BIT_reloadDStream(&bitD)==BIT_DStream_unfinished) & (op<olimit) ; op+=4) {
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op[0] = FSE_GETSYMBOL(&state1);
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if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */
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BIT_reloadDStream(&bitD);
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op[1] = FSE_GETSYMBOL(&state2);
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if (FSE_MAX_TABLELOG*4+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */
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{ if (BIT_reloadDStream(&bitD) > BIT_DStream_unfinished) { op+=2; break; } }
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op[2] = FSE_GETSYMBOL(&state1);
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if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8) /* This test must be static */
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BIT_reloadDStream(&bitD);
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op[3] = FSE_GETSYMBOL(&state2);
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}
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/* tail */
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/* note : BIT_reloadDStream(&bitD) >= FSE_DStream_partiallyFilled; Ends at exactly BIT_DStream_completed */
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while (1) {
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if (op>(omax-2)) return ERROR(dstSize_tooSmall);
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*op++ = FSE_GETSYMBOL(&state1);
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if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) {
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*op++ = FSE_GETSYMBOL(&state2);
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break;
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}
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if (op>(omax-2)) return ERROR(dstSize_tooSmall);
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*op++ = FSE_GETSYMBOL(&state2);
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if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) {
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*op++ = FSE_GETSYMBOL(&state1);
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break;
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} }
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assert(op >= ostart);
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return (size_t)(op-ostart);
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}
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typedef struct {
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short ncount[FSE_MAX_SYMBOL_VALUE + 1];
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} FSE_DecompressWksp;
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FORCE_INLINE_TEMPLATE size_t FSE_decompress_wksp_body(
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void* dst, size_t dstCapacity,
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const void* cSrc, size_t cSrcSize,
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unsigned maxLog, void* workSpace, size_t wkspSize,
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int bmi2)
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{
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const BYTE* const istart = (const BYTE*)cSrc;
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const BYTE* ip = istart;
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unsigned tableLog;
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unsigned maxSymbolValue = FSE_MAX_SYMBOL_VALUE;
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FSE_DecompressWksp* const wksp = (FSE_DecompressWksp*)workSpace;
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size_t const dtablePos = sizeof(FSE_DecompressWksp) / sizeof(FSE_DTable);
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FSE_DTable* const dtable = (FSE_DTable*)workSpace + dtablePos;
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FSE_STATIC_ASSERT((FSE_MAX_SYMBOL_VALUE + 1) % 2 == 0);
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if (wkspSize < sizeof(*wksp)) return ERROR(GENERIC);
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/* correct offset to dtable depends on this property */
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FSE_STATIC_ASSERT(sizeof(FSE_DecompressWksp) % sizeof(FSE_DTable) == 0);
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/* normal FSE decoding mode */
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{ size_t const NCountLength =
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FSE_readNCount_bmi2(wksp->ncount, &maxSymbolValue, &tableLog, istart, cSrcSize, bmi2);
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if (FSE_isError(NCountLength)) return NCountLength;
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if (tableLog > maxLog) return ERROR(tableLog_tooLarge);
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assert(NCountLength <= cSrcSize);
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ip += NCountLength;
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cSrcSize -= NCountLength;
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}
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if (FSE_DECOMPRESS_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(tableLog_tooLarge);
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assert(sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog) <= wkspSize);
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workSpace = (BYTE*)workSpace + sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);
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wkspSize -= sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);
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CHECK_F( FSE_buildDTable_internal(dtable, wksp->ncount, maxSymbolValue, tableLog, workSpace, wkspSize) );
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{
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const void* ptr = dtable;
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const FSE_DTableHeader* DTableH = (const FSE_DTableHeader*)ptr;
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const U32 fastMode = DTableH->fastMode;
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/* select fast mode (static) */
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if (fastMode) return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 1);
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return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 0);
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}
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}
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/* Avoids the FORCE_INLINE of the _body() function. */
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static 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)
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{
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return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 0);
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}
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#if DYNAMIC_BMI2
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BMI2_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)
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{
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return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 1);
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}
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#endif
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size_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)
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{
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#if DYNAMIC_BMI2
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if (bmi2) {
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return FSE_decompress_wksp_body_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
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}
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#endif
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(void)bmi2;
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return FSE_decompress_wksp_body_default(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
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}
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#endif /* FSE_COMMONDEFS_ONLY */
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