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// SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause/* ****************************************************************** * FSE : Finite State Entropy decoder * Copyright (c) Meta Platforms, Inc. and affiliates. * *  You can contact the author at : *  - FSE source repository : https://github.com/Cyan4973/FiniteStateEntropy *  - Public forum : https://groups.google.com/forum/#!forum/lz4c * * 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.****************************************************************** */  /* ***************************************************************  Includes****************************************************************/#include "debug.h"      /* assert */#include "bitstream.h"#include "compiler.h"#define FSE_STATIC_LINKING_ONLY#include "fse.h"#include "error_private.h"#include "zstd_deps.h"  /* ZSTD_memcpy */#include "bits.h"       /* ZSTD_highbit32 */  /* ***************************************************************  Error Management****************************************************************/#define FSE_isError ERR_isError#define FSE_STATIC_ASSERT(c) DEBUG_STATIC_ASSERT(c)   /* use only *after* variable declarations */  /* ***************************************************************  Templates****************************************************************//*  designed to be included  for type-specific functions (template emulation in C)  Objective is to write these functions only once, for improved maintenance*/ /* safety checks */#ifndef FSE_FUNCTION_EXTENSION#  error "FSE_FUNCTION_EXTENSION must be defined"#endif#ifndef FSE_FUNCTION_TYPE#  error "FSE_FUNCTION_TYPE must be defined"#endif /* Function names */#define FSE_CAT(X,Y) X##Y#define FSE_FUNCTION_NAME(X,Y) FSE_CAT(X,Y)#define FSE_TYPE_NAME(X,Y) FSE_CAT(X,Y) static size_t FSE_buildDTable_internal(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize){    void* const tdPtr = dt+1;   /* because *dt is unsigned, 32-bits aligned on 32-bits */    FSE_DECODE_TYPE* const tableDecode = (FSE_DECODE_TYPE*) (tdPtr);    U16* symbolNext = (U16*)workSpace;    BYTE* spread = (BYTE*)(symbolNext + maxSymbolValue + 1);     U32 const maxSV1 = maxSymbolValue + 1;    U32 const tableSize = 1 << tableLog;    U32 highThreshold = tableSize-1;     /* Sanity Checks */    if (FSE_BUILD_DTABLE_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(maxSymbolValue_tooLarge);    if (maxSymbolValue > FSE_MAX_SYMBOL_VALUE) return ERROR(maxSymbolValue_tooLarge);    if (tableLog > FSE_MAX_TABLELOG) return ERROR(tableLog_tooLarge);     /* Init, lay down lowprob symbols */    {   FSE_DTableHeader DTableH;        DTableH.tableLog = (U16)tableLog;        DTableH.fastMode = 1;        {   S16 const largeLimit= (S16)(1 << (tableLog-1));            U32 s;            for (s=0; s<maxSV1; s++) {                if (normalizedCounter[s]==-1) {                    tableDecode[highThreshold--].symbol = (FSE_FUNCTION_TYPE)s;                    symbolNext[s] = 1;                } else {                    if (normalizedCounter[s] >= largeLimit) DTableH.fastMode=0;                    symbolNext[s] = (U16)normalizedCounter[s];        }   }   }        ZSTD_memcpy(dt, &DTableH, sizeof(DTableH));    }     /* Spread symbols */    if (highThreshold == tableSize - 1) {        size_t const tableMask = tableSize-1;        size_t const step = FSE_TABLESTEP(tableSize);        /* First lay down the symbols in order.         * We use a uint64_t to lay down 8 bytes at a time. This reduces branch         * misses since small blocks generally have small table logs, so nearly         * all symbols have counts <= 8. We ensure we have 8 bytes at the end of         * our buffer to handle the over-write.         */        {   U64 const add = 0x0101010101010101ull;            size_t pos = 0;            U64 sv = 0;            U32 s;            for (s=0; s<maxSV1; ++s, sv += add) {                int i;                int const n = normalizedCounter[s];                MEM_write64(spread + pos, sv);                for (i = 8; i < n; i += 8) {                    MEM_write64(spread + pos + i, sv);                }                pos += (size_t)n;        }   }        /* Now we spread those positions across the table.         * The benefit of doing it in two stages is that we avoid the         * variable size inner loop, which caused lots of branch misses.         * Now we can run through all the positions without any branch misses.         * We unroll the loop twice, since that is what empirically worked best.         */        {            size_t position = 0;            size_t s;            size_t const unroll = 2;            assert(tableSize % unroll == 0); /* FSE_MIN_TABLELOG is 5 */            for (s = 0; s < (size_t)tableSize; s += unroll) {                size_t u;                for (u = 0; u < unroll; ++u) {                    size_t const uPosition = (position + (u * step)) & tableMask;                    tableDecode[uPosition].symbol = spread[s + u];                }                position = (position + (unroll * step)) & tableMask;            }            assert(position == 0);        }    } else {        U32 const tableMask = tableSize-1;        U32 const step = FSE_TABLESTEP(tableSize);        U32 s, position = 0;        for (s=0; s<maxSV1; s++) {            int i;            for (i=0; i<normalizedCounter[s]; i++) {                tableDecode[position].symbol = (FSE_FUNCTION_TYPE)s;                position = (position + step) & tableMask;                while (position > highThreshold) position = (position + step) & tableMask;   /* lowprob area */        }   }        if (position!=0) return ERROR(GENERIC);   /* position must reach all cells once, otherwise normalizedCounter is incorrect */    }     /* Build Decoding table */    {   U32 u;        for (u=0; u<tableSize; u++) {            FSE_FUNCTION_TYPE const symbol = (FSE_FUNCTION_TYPE)(tableDecode[u].symbol);            U32 const nextState = symbolNext[symbol]++;            tableDecode[u].nbBits = (BYTE) (tableLog - ZSTD_highbit32(nextState) );            tableDecode[u].newState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize);    }   }     return 0;} size_t FSE_buildDTable_wksp(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog, void* workSpace, size_t wkspSize){    return FSE_buildDTable_internal(dt, normalizedCounter, maxSymbolValue, tableLog, workSpace, wkspSize);}  #ifndef FSE_COMMONDEFS_ONLY /*-********************************************************  Decompression (Byte symbols)*********************************************************/ FORCE_INLINE_TEMPLATE size_t FSE_decompress_usingDTable_generic(          void* dst, size_t maxDstSize,    const void* cSrc, size_t cSrcSize,    const FSE_DTable* dt, const unsigned fast){    BYTE* const ostart = (BYTE*) dst;    BYTE* op = ostart;    BYTE* const omax = op + maxDstSize;    BYTE* const olimit = omax-3;     BIT_DStream_t bitD;    FSE_DState_t state1;    FSE_DState_t state2;     /* Init */    CHECK_F(BIT_initDStream(&bitD, cSrc, cSrcSize));     FSE_initDState(&state1, &bitD, dt);    FSE_initDState(&state2, &bitD, dt);     RETURN_ERROR_IF(BIT_reloadDStream(&bitD)==BIT_DStream_overflow, corruption_detected, ""); #define FSE_GETSYMBOL(statePtr) fast ? FSE_decodeSymbolFast(statePtr, &bitD) : FSE_decodeSymbol(statePtr, &bitD)     /* 4 symbols per loop */    for ( ; (BIT_reloadDStream(&bitD)==BIT_DStream_unfinished) & (op<olimit) ; op+=4) {        op[0] = FSE_GETSYMBOL(&state1);         if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8)    /* This test must be static */            BIT_reloadDStream(&bitD);         op[1] = FSE_GETSYMBOL(&state2);         if (FSE_MAX_TABLELOG*4+7 > sizeof(bitD.bitContainer)*8)    /* This test must be static */            { if (BIT_reloadDStream(&bitD) > BIT_DStream_unfinished) { op+=2; break; } }         op[2] = FSE_GETSYMBOL(&state1);         if (FSE_MAX_TABLELOG*2+7 > sizeof(bitD.bitContainer)*8)    /* This test must be static */            BIT_reloadDStream(&bitD);         op[3] = FSE_GETSYMBOL(&state2);    }     /* tail */    /* note : BIT_reloadDStream(&bitD) >= FSE_DStream_partiallyFilled; Ends at exactly BIT_DStream_completed */    while (1) {        if (op>(omax-2)) return ERROR(dstSize_tooSmall);        *op++ = FSE_GETSYMBOL(&state1);        if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) {            *op++ = FSE_GETSYMBOL(&state2);            break;        }         if (op>(omax-2)) return ERROR(dstSize_tooSmall);        *op++ = FSE_GETSYMBOL(&state2);        if (BIT_reloadDStream(&bitD)==BIT_DStream_overflow) {            *op++ = FSE_GETSYMBOL(&state1);            break;    }   }     assert(op >= ostart);    return (size_t)(op-ostart);} typedef struct {    short ncount[FSE_MAX_SYMBOL_VALUE + 1];} FSE_DecompressWksp;  FORCE_INLINE_TEMPLATE size_t FSE_decompress_wksp_body(        void* dst, size_t dstCapacity,        const void* cSrc, size_t cSrcSize,        unsigned maxLog, void* workSpace, size_t wkspSize,        int bmi2){    const BYTE* const istart = (const BYTE*)cSrc;    const BYTE* ip = istart;    unsigned tableLog;    unsigned maxSymbolValue = FSE_MAX_SYMBOL_VALUE;    FSE_DecompressWksp* const wksp = (FSE_DecompressWksp*)workSpace;    size_t const dtablePos = sizeof(FSE_DecompressWksp) / sizeof(FSE_DTable);    FSE_DTable* const dtable = (FSE_DTable*)workSpace + dtablePos;     FSE_STATIC_ASSERT((FSE_MAX_SYMBOL_VALUE + 1) % 2 == 0);    if (wkspSize < sizeof(*wksp)) return ERROR(GENERIC);     /* correct offset to dtable depends on this property */    FSE_STATIC_ASSERT(sizeof(FSE_DecompressWksp) % sizeof(FSE_DTable) == 0);     /* normal FSE decoding mode */    {   size_t const NCountLength =            FSE_readNCount_bmi2(wksp->ncount, &maxSymbolValue, &tableLog, istart, cSrcSize, bmi2);        if (FSE_isError(NCountLength)) return NCountLength;        if (tableLog > maxLog) return ERROR(tableLog_tooLarge);        assert(NCountLength <= cSrcSize);        ip += NCountLength;        cSrcSize -= NCountLength;    }     if (FSE_DECOMPRESS_WKSP_SIZE(tableLog, maxSymbolValue) > wkspSize) return ERROR(tableLog_tooLarge);    assert(sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog) <= wkspSize);    workSpace = (BYTE*)workSpace + sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);    wkspSize -= sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);     CHECK_F( FSE_buildDTable_internal(dtable, wksp->ncount, maxSymbolValue, tableLog, workSpace, wkspSize) );     {        const void* ptr = dtable;        const FSE_DTableHeader* DTableH = (const FSE_DTableHeader*)ptr;        const U32 fastMode = DTableH->fastMode;         /* select fast mode (static) */        if (fastMode) return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 1);        return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, dtable, 0);    }} /* Avoids the FORCE_INLINE of the _body() function. */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){    return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 0);} #if DYNAMIC_BMI2BMI2_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){    return FSE_decompress_wksp_body(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, 1);}#endif 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){#if DYNAMIC_BMI2    if (bmi2) {        return FSE_decompress_wksp_body_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);    }#endif    (void)bmi2;    return FSE_decompress_wksp_body_default(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);} #endif   /* FSE_COMMONDEFS_ONLY */