lzmadecode.c

一个7ZIP的解压源码。比较详细。里面含有四种语言的实现代码。

        + globalPos
        #endif
        )
        & literalPosMask) << lc) + (previousByte >> (8 - lc))));

      if (state >= kNumLitStates)
      {
        int matchByte;
        #ifdef _LZMA_OUT_READ
        UInt32 pos = dictionaryPos - rep0;
        if (pos >= dictionarySize)
          pos += dictionarySize;
        matchByte = dictionary[pos];
        #else
        matchByte = outStream[nowPos - rep0];
        #endif
        do
        {
          int bit;
          CProb *probLit;
          matchByte <<= 1;
          bit = (matchByte & 0x100);
          probLit = prob + 0x100 + bit + symbol;
          RC_GET_BIT2(probLit, symbol, if (bit != 0) break, if (bit == 0) break)
        }
        while (symbol < 0x100);
      }
      while (symbol < 0x100)
      {
        CProb *probLit = prob + symbol;
        RC_GET_BIT(probLit, symbol)
      }
      previousByte = (Byte)symbol;

      outStream[nowPos++] = previousByte;
      #ifdef _LZMA_OUT_READ
      if (distanceLimit < dictionarySize)
        distanceLimit++;

      dictionary[dictionaryPos] = previousByte;
      if (++dictionaryPos == dictionarySize)
        dictionaryPos = 0;
      #endif
      if (state < 4) state = 0;
      else if (state < 10) state -= 3;
      else state -= 6;
    }
    else             
    {
      UpdateBit1(prob);
      prob = p + IsRep + state;
      IfBit0(prob)
      {
        UpdateBit0(prob);
        rep3 = rep2;
        rep2 = rep1;
        rep1 = rep0;
        state = state < kNumLitStates ? 0 : 3;
        prob = p + LenCoder;
      }
      else
      {
        UpdateBit1(prob);
        prob = p + IsRepG0 + state;
        IfBit0(prob)
        {
          UpdateBit0(prob);
          prob = p + IsRep0Long + (state << kNumPosBitsMax) + posState;
          IfBit0(prob)
          {
            #ifdef _LZMA_OUT_READ
            UInt32 pos;
            #endif
            UpdateBit0(prob);
            
            #ifdef _LZMA_OUT_READ
            if (distanceLimit == 0)
            #else
            if (nowPos == 0)
            #endif
              return LZMA_RESULT_DATA_ERROR;
            
            state = state < kNumLitStates ? 9 : 11;
            #ifdef _LZMA_OUT_READ
            pos = dictionaryPos - rep0;
            if (pos >= dictionarySize)
              pos += dictionarySize;
            previousByte = dictionary[pos];
            dictionary[dictionaryPos] = previousByte;
            if (++dictionaryPos == dictionarySize)
              dictionaryPos = 0;
            #else
            previousByte = outStream[nowPos - rep0];
            #endif
            outStream[nowPos++] = previousByte;
            #ifdef _LZMA_OUT_READ
            if (distanceLimit < dictionarySize)
              distanceLimit++;
            #endif

            continue;
          }
          else
          {
            UpdateBit1(prob);
          }
        }
        else
        {
          UInt32 distance;
          UpdateBit1(prob);
          prob = p + IsRepG1 + state;
          IfBit0(prob)
          {
            UpdateBit0(prob);
            distance = rep1;
          }
          else 
          {
            UpdateBit1(prob);
            prob = p + IsRepG2 + state;
            IfBit0(prob)
            {
              UpdateBit0(prob);
              distance = rep2;
            }
            else
            {
              UpdateBit1(prob);
              distance = rep3;
              rep3 = rep2;
            }
            rep2 = rep1;
          }
          rep1 = rep0;
          rep0 = distance;
        }
        state = state < kNumLitStates ? 8 : 11;
        prob = p + RepLenCoder;
      }
      {
        int numBits, offset;
        CProb *probLen = prob + LenChoice;
        IfBit0(probLen)
        {
          UpdateBit0(probLen);
          probLen = prob + LenLow + (posState << kLenNumLowBits);
          offset = 0;
          numBits = kLenNumLowBits;
        }
        else
        {
          UpdateBit1(probLen);
          probLen = prob + LenChoice2;
          IfBit0(probLen)
          {
            UpdateBit0(probLen);
            probLen = prob + LenMid + (posState << kLenNumMidBits);
            offset = kLenNumLowSymbols;
            numBits = kLenNumMidBits;
          }
          else
          {
            UpdateBit1(probLen);
            probLen = prob + LenHigh;
            offset = kLenNumLowSymbols + kLenNumMidSymbols;
            numBits = kLenNumHighBits;
          }
        }
        RangeDecoderBitTreeDecode(probLen, numBits, len);
        len += offset;
      }

      if (state < 4)
      {
        int posSlot;
        state += kNumLitStates;
        prob = p + PosSlot +
            ((len < kNumLenToPosStates ? len : kNumLenToPosStates - 1) << 
            kNumPosSlotBits);
        RangeDecoderBitTreeDecode(prob, kNumPosSlotBits, posSlot);
        if (posSlot >= kStartPosModelIndex)
        {
          int numDirectBits = ((posSlot >> 1) - 1);
          rep0 = (2 | ((UInt32)posSlot & 1));
          if (posSlot < kEndPosModelIndex)
          {
            rep0 <<= numDirectBits;
            prob = p + SpecPos + rep0 - posSlot - 1;
          }
          else
          {
            numDirectBits -= kNumAlignBits;
            do
            {
              RC_NORMALIZE
              Range >>= 1;
              rep0 <<= 1;
              if (Code >= Range)
              {
                Code -= Range;
                rep0 |= 1;
              }
            }
            while (--numDirectBits != 0);
            prob = p + Align;
            rep0 <<= kNumAlignBits;
            numDirectBits = kNumAlignBits;
          }
          {
            int i = 1;
            int mi = 1;
            do
            {
              CProb *prob3 = prob + mi;
              RC_GET_BIT2(prob3, mi, ; , rep0 |= i);
              i <<= 1;
            }
            while(--numDirectBits != 0);
          }
        }
        else
          rep0 = posSlot;
        if (++rep0 == (UInt32)(0))
        {
          /* it's for stream version */
          len = kLzmaStreamWasFinishedId;
          break;
        }
      }

      len += kMatchMinLen;
      #ifdef _LZMA_OUT_READ
      if (rep0 > distanceLimit) 
      #else
      if (rep0 > nowPos)
      #endif
        return LZMA_RESULT_DATA_ERROR;

      #ifdef _LZMA_OUT_READ
      if (dictionarySize - distanceLimit > (UInt32)len)
        distanceLimit += len;
      else
        distanceLimit = dictionarySize;
      #endif

      do
      {
        #ifdef _LZMA_OUT_READ
        UInt32 pos = dictionaryPos - rep0;
        if (pos >= dictionarySize)
          pos += dictionarySize;
        previousByte = dictionary[pos];
        dictionary[dictionaryPos] = previousByte;
        if (++dictionaryPos == dictionarySize)
          dictionaryPos = 0;
        #else
        previousByte = outStream[nowPos - rep0];
        #endif
        len--;
        outStream[nowPos++] = previousByte;
      }
      while(len != 0 && nowPos < outSize);
    }
  }
  RC_NORMALIZE;

  #ifdef _LZMA_OUT_READ
  vs->Range = Range;
  vs->Code = Code;
  vs->DictionaryPos = dictionaryPos;
  vs->GlobalPos = globalPos + (UInt32)nowPos;
  vs->DistanceLimit = distanceLimit;
  vs->Reps[0] = rep0;
  vs->Reps[1] = rep1;
  vs->Reps[2] = rep2;
  vs->Reps[3] = rep3;
  vs->State = state;
  vs->RemainLen = len;
  vs->TempDictionary[0] = tempDictionary[0];
  #endif

  #ifdef _LZMA_IN_CB
  vs->Buffer = Buffer;
  vs->BufferLim = BufferLim;
  #else
  *inSizeProcessed = (SizeT)(Buffer - inStream);
  #endif
  *outSizeProcessed = nowPos;
  return LZMA_RESULT_OK;
}