FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/zstd/lib/common/fse_decompress.c

     /* ******************************************************************
      * FSE : Finite State Entropy decoder
      * Copyright (c) 2013-2020, Yann Collet, Facebook, Inc.
      *
      *  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 <stdlib.h>     /* malloc, free, qsort */
    #include <string.h>     /* memcpy, memset */
    #include "bitstream.h"
    #include "compiler.h"
    #define FSE_STATIC_LINKING_ONLY
    #include "fse.h"
    #include "error_private.h"
    
    
    /* **************************************************************
    *  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)
    
    
    /* Function templates */
    size_t FSE_buildDTable(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog)
    {
        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[FSE_MAX_SYMBOL_VALUE+1];
    
        U32 const maxSV1 = maxSymbolValue + 1;
        U32 const tableSize = 1 << tableLog;
        U32 highThreshold = tableSize-1;
    
        /* Sanity Checks */
        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] = normalizedCounter[s];
            }   }   }
            memcpy(dt, &DTableH, sizeof(DTableH));
        }
    
        /* Spread symbols */
        {   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 - BIT_highbit32(nextState) );
               tableDecode[u].newState = (U16) ( (nextState << tableDecode[u].nbBits) - tableSize);
       }   }
   
       return 0;
   }
   
   
   #ifndef FSE_COMMONDEFS_ONLY
   
   /*-*******************************************************
   *  Decompression (Byte symbols)
   *********************************************************/
   size_t FSE_buildDTable_rle (FSE_DTable* dt, BYTE symbolValue)
   {
       void* ptr = dt;
       FSE_DTableHeader* const DTableH = (FSE_DTableHeader*)ptr;
       void* dPtr = dt + 1;
       FSE_decode_t* const cell = (FSE_decode_t*)dPtr;
   
       DTableH->tableLog = 0;
       DTableH->fastMode = 0;
   
       cell->newState = 0;
       cell->symbol = symbolValue;
       cell->nbBits = 0;
   
       return 0;
   }
   
   
   size_t FSE_buildDTable_raw (FSE_DTable* dt, unsigned nbBits)
   {
       void* ptr = dt;
       FSE_DTableHeader* const DTableH = (FSE_DTableHeader*)ptr;
       void* dPtr = dt + 1;
       FSE_decode_t* const dinfo = (FSE_decode_t*)dPtr;
       const unsigned tableSize = 1 << nbBits;
       const unsigned tableMask = tableSize - 1;
       const unsigned maxSV1 = tableMask+1;
       unsigned s;
   
       /* Sanity checks */
       if (nbBits < 1) return ERROR(GENERIC);         /* min size */
   
       /* Build Decoding Table */
       DTableH->tableLog = (U16)nbBits;
       DTableH->fastMode = 1;
       for (s=0; s<maxSV1; s++) {
           dinfo[s].newState = 0;
           dinfo[s].symbol = (BYTE)s;
           dinfo[s].nbBits = (BYTE)nbBits;
       }
   
       return 0;
   }
   
   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);
   
   #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;
       }   }
   
       return op-ostart;
   }
   
   
   size_t FSE_decompress_usingDTable(void* dst, size_t originalSize,
                               const void* cSrc, size_t cSrcSize,
                               const FSE_DTable* dt)
   {
       const void* ptr = dt;
       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, originalSize, cSrc, cSrcSize, dt, 1);
       return FSE_decompress_usingDTable_generic(dst, originalSize, cSrc, cSrcSize, dt, 0);
   }
   
   
   size_t FSE_decompress_wksp(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, FSE_DTable* workSpace, unsigned maxLog)
   {
       const BYTE* const istart = (const BYTE*)cSrc;
       const BYTE* ip = istart;
       short counting[FSE_MAX_SYMBOL_VALUE+1];
       unsigned tableLog;
       unsigned maxSymbolValue = FSE_MAX_SYMBOL_VALUE;
   
       /* normal FSE decoding mode */
       size_t const NCountLength = FSE_readNCount (counting, &maxSymbolValue, &tableLog, istart, cSrcSize);
       if (FSE_isError(NCountLength)) return NCountLength;
       /* if (NCountLength >= cSrcSize) return ERROR(srcSize_wrong); */  /* too small input size; supposed to be already checked in NCountLength, only remaining case : NCountLength==cSrcSize */
       if (tableLog > maxLog) return ERROR(tableLog_tooLarge);
       ip += NCountLength;
       cSrcSize -= NCountLength;
   
       CHECK_F( FSE_buildDTable (workSpace, counting, maxSymbolValue, tableLog) );
   
       return FSE_decompress_usingDTable (dst, dstCapacity, ip, cSrcSize, workSpace);   /* always return, even if it is an error code */
   }
   
   
   typedef FSE_DTable DTable_max_t[FSE_DTABLE_SIZE_U32(FSE_MAX_TABLELOG)];
   
   size_t FSE_decompress(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize)
   {
       DTable_max_t dt;   /* Static analyzer seems unable to understand this table will be properly initialized later */
       return FSE_decompress_wksp(dst, dstCapacity, cSrc, cSrcSize, dt, FSE_MAX_TABLELOG);
   }
   
   
   
   #endif   /* FSE_COMMONDEFS_ONLY */

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