text: ﻿/* ******************************************************************
   * FSE : Finite State Entropy decoder
   * Copyright (c) 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 "debug.h"      /* assert */
  #include "bitstream.h"
  #include "compiler.h"
  #define FSE_STATIC_LINKING_ONLY
  #include "fse.h"
  #include "error_private.h"
  #define ZSTD_DEPS_NEED_MALLOC
  #include "zstd_deps.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 */
  FSE_DTable* FSE_createDTable (unsigned tableLog)
  {
      if (tableLog > FSE_TABLELOG_ABSOLUTE_MAX) tableLog = FSE_TABLELOG_ABSOLUTE_MAX;
      return (FSE_DTable*)ZSTD_malloc( FSE_DTABLE_SIZE_U32(tableLog) * sizeof (U32) );
  }
  
  void FSE_freeDTable (FSE_DTable* dt)
  {
      ZSTD_free(dt);
  }
  
  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] = 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 += n;
              }
          }
          /* Now we spread those positions across the table.
           * The benefit of doing it in two stages is that we avoid the 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 emperically 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 - BIT_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)
  *********************************************************/
  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, unsigned maxLog, void* workSpace, size_t wkspSize)
  {
      return FSE_decompress_wksp_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize, /* bmi2 */ 0);
  }
  
  typedef struct {
      short ncount[FSE_MAX_SYMBOL_VALUE + 1];
      FSE_DTable dtable[1]; /* Dynamically sized */
  } 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;
  
      DEBUG_STATIC_ASSERT((FSE_MAX_SYMBOL_VALUE + 1) % 2 == 0);
      if (wkspSize < sizeof(*wksp)) return ERROR(GENERIC);
  
      /* 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);
      workSpace = wksp->dtable + FSE_DTABLE_SIZE_U32(tableLog);
      wkspSize -= sizeof(*wksp) + FSE_DTABLE_SIZE(tableLog);
  
      CHECK_F( FSE_buildDTable_internal(wksp->dtable, wksp->ncount, maxSymbolValue, tableLog, workSpace, wkspSize) );
  
      {
          const void* ptr = wksp->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, wksp->dtable, 1);
          return FSE_decompress_usingDTable_generic(dst, dstCapacity, ip, cSrcSize, wksp->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_BMI2
  TARGET_ATTRIBUTE("bmi2") 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);
  }
  
  
  typedef FSE_DTable DTable_max_t[FSE_DTABLE_SIZE_U32(FSE_MAX_TABLELOG)];
  
  #ifndef ZSTD_NO_UNUSED_FUNCTIONS
  size_t FSE_buildDTable(FSE_DTable* dt, const short* normalizedCounter, unsigned maxSymbolValue, unsigned tableLog) {
      U32 wksp[FSE_BUILD_DTABLE_WKSP_SIZE_U32(FSE_TABLELOG_ABSOLUTE_MAX, FSE_MAX_SYMBOL_VALUE)];
      return FSE_buildDTable_wksp(dt, normalizedCounter, maxSymbolValue, tableLog, wksp, sizeof(wksp));
  }
  
  size_t FSE_decompress(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize)
  {
      /* Static analyzer seems unable to understand this table will be properly initialized later */
      U32 wksp[FSE_DECOMPRESS_WKSP_SIZE_U32(FSE_MAX_TABLELOG, FSE_MAX_SYMBOL_VALUE)];
      return FSE_decompress_wksp(dst, dstCapacity, cSrc, cSrcSize, FSE_MAX_TABLELOG, wksp, sizeof(wksp));
  }
  #endif
  
  
  #endif   /* FSE_COMMONDEFS_ONLY */
  