lzmadecodesize.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。

/*
  LzmaDecodeSize.c
  LZMA Decoder (optimized for Size version)
  
  LZMA SDK 4.40 Copyright (c) 1999-2006 Igor Pavlov (2006-05-01)
  http://www.7-zip.org/

  LZMA SDK is licensed under two licenses:
  1) GNU Lesser General Public License (GNU LGPL)
  2) Common Public License (CPL)
  It means that you can select one of these two licenses and 
  follow rules of that license.

  SPECIAL EXCEPTION:
  Igor Pavlov, as the author of this code, expressly permits you to 
  statically or dynamically link your code (or bind by name) to the 
  interfaces of this file without subjecting your linked code to the 
  terms of the CPL or GNU LGPL. Any modifications or additions 
  to this file, however, are subject to the LGPL or CPL terms.
*/

#include "LzmaDecode.h"

#define kNumTopBits 24
#define kTopValue ((UInt32)1 << kNumTopBits)

#define kNumBitModelTotalBits 11
#define kBitModelTotal (1 << kNumBitModelTotalBits)
#define kNumMoveBits 5

typedef struct _CRangeDecoder
{
  const Byte *Buffer;
  const Byte *BufferLim;
  UInt32 Range;
  UInt32 Code;
  #ifdef _LZMA_IN_CB
  ILzmaInCallback *InCallback;
  int Result;
  #endif
  int ExtraBytes;
} CRangeDecoder;

Byte RangeDecoderReadByte(CRangeDecoder *rd)
{
  if (rd->Buffer == rd->BufferLim)
  {
    #ifdef _LZMA_IN_CB
    SizeT size;
    rd->Result = rd->InCallback->Read(rd->InCallback, &rd->Buffer, &size);
    rd->BufferLim = rd->Buffer + size;
    if (size == 0)
    #endif
    {
      rd->ExtraBytes = 1;
      return 0xFF;
    }
  }
  return (*rd->Buffer++);
}

/* #define ReadByte (*rd->Buffer++) */
#define ReadByte (RangeDecoderReadByte(rd))

void RangeDecoderInit(CRangeDecoder *rd
  #ifndef _LZMA_IN_CB
    , const Byte *stream, SizeT bufferSize
  #endif
    )
{
  int i;
  #ifdef _LZMA_IN_CB
  rd->Buffer = rd->BufferLim = 0;
  #else
  rd->Buffer = stream;
  rd->BufferLim = stream + bufferSize;
  #endif
  rd->ExtraBytes = 0;
  rd->Code = 0;
  rd->Range = (0xFFFFFFFF);
  for(i = 0; i < 5; i++)
    rd->Code = (rd->Code << 8) | ReadByte;
}

#define RC_INIT_VAR UInt32 range = rd->Range; UInt32 code = rd->Code;        
#define RC_FLUSH_VAR rd->Range = range; rd->Code = code;
#define RC_NORMALIZE if (range < kTopValue) { range <<= 8; code = (code << 8) | ReadByte; }

UInt32 RangeDecoderDecodeDirectBits(CRangeDecoder *rd, int numTotalBits)
{
  RC_INIT_VAR
  UInt32 result = 0;
  int i;
  for (i = numTotalBits; i != 0; i--)
  {
    /* UInt32 t; */
    range >>= 1;

    result <<= 1;
    if (code >= range)
    {
      code -= range;
      result |= 1;
    }
    /*
    t = (code - range) >> 31;
    t &= 1;
    code -= range & (t - 1);
    result = (result + result) | (1 - t);
    */
    RC_NORMALIZE
  }
  RC_FLUSH_VAR
  return result;
}

int RangeDecoderBitDecode(CProb *prob, CRangeDecoder *rd)
{
  UInt32 bound = (rd->Range >> kNumBitModelTotalBits) * *prob;
  if (rd->Code < bound)
  {
    rd->Range = bound;
    *prob += (kBitModelTotal - *prob) >> kNumMoveBits;
    if (rd->Range < kTopValue)
    {
      rd->Code = (rd->Code << 8) | ReadByte;
      rd->Range <<= 8;
    }
    return 0;
  }
  else
  {
    rd->Range -= bound;
    rd->Code -= bound;
    *prob -= (*prob) >> kNumMoveBits;
    if (rd->Range < kTopValue)
    {
      rd->Code = (rd->Code << 8) | ReadByte;
      rd->Range <<= 8;
    }
    return 1;
  }
}

#define RC_GET_BIT2(prob, mi, A0, A1) \
  UInt32 bound = (range >> kNumBitModelTotalBits) * *prob; \
  if (code < bound) \
    { A0; range = bound; *prob += (kBitModelTotal - *prob) >> kNumMoveBits; mi <<= 1; } \
  else \
    { A1; range -= bound; code -= bound; *prob -= (*prob) >> kNumMoveBits; mi = (mi + mi) + 1; } \
  RC_NORMALIZE

#define RC_GET_BIT(prob, mi) RC_GET_BIT2(prob, mi, ; , ;)               

int RangeDecoderBitTreeDecode(CProb *probs, int numLevels, CRangeDecoder *rd)
{
  int mi = 1;
  int i;
  #ifdef _LZMA_LOC_OPT
  RC_INIT_VAR
  #endif
  for(i = numLevels; i != 0; i--)
  {
    #ifdef _LZMA_LOC_OPT
    CProb *prob = probs + mi;
    RC_GET_BIT(prob, mi)
    #else
    mi = (mi + mi) + RangeDecoderBitDecode(probs + mi, rd);
    #endif
  }
  #ifdef _LZMA_LOC_OPT
  RC_FLUSH_VAR
  #endif
  return mi - (1 << numLevels);
}

int RangeDecoderReverseBitTreeDecode(CProb *probs, int numLevels, CRangeDecoder *rd)
{
  int mi = 1;
  int i;
  int symbol = 0;
  #ifdef _LZMA_LOC_OPT
  RC_INIT_VAR
  #endif
  for(i = 0; i < numLevels; i++)
  {
    #ifdef _LZMA_LOC_OPT
    CProb *prob = probs + mi;
    RC_GET_BIT2(prob, mi, ; , symbol |= (1 << i))
    #else
    int bit = RangeDecoderBitDecode(probs + mi, rd);
    mi = mi + mi + bit;
    symbol |= (bit << i);
    #endif
  }
  #ifdef _LZMA_LOC_OPT
  RC_FLUSH_VAR
  #endif
  return symbol;
}

Byte LzmaLiteralDecode(CProb *probs, CRangeDecoder *rd)
{ 
  int symbol = 1;
  #ifdef _LZMA_LOC_OPT
  RC_INIT_VAR
  #endif
  do
  {
    #ifdef _LZMA_LOC_OPT
    CProb *prob = probs + symbol;
    RC_GET_BIT(prob, symbol)
    #else
    symbol = (symbol + symbol) | RangeDecoderBitDecode(probs + symbol, rd);
    #endif
  }
  while (symbol < 0x100);
  #ifdef _LZMA_LOC_OPT
  RC_FLUSH_VAR
  #endif
  return symbol;
}

Byte LzmaLiteralDecodeMatch(CProb *probs, CRangeDecoder *rd, Byte matchByte)
{ 
  int symbol = 1;
  #ifdef _LZMA_LOC_OPT
  RC_INIT_VAR
  #endif
  do
  {
    int bit;
    int matchBit = (matchByte >> 7) & 1;
    matchByte <<= 1;
    #ifdef _LZMA_LOC_OPT
    {
      CProb *prob = probs + 0x100 + (matchBit << 8) + symbol;
      RC_GET_BIT2(prob, symbol, bit = 0, bit = 1)
    }
    #else
    bit = RangeDecoderBitDecode(probs + 0x100 + (matchBit << 8) + symbol, rd);
    symbol = (symbol << 1) | bit;
    #endif
    if (matchBit != bit)
    {
      while (symbol < 0x100)
      {
        #ifdef _LZMA_LOC_OPT
        CProb *prob = probs + symbol;
        RC_GET_BIT(prob, symbol)
        #else
        symbol = (symbol + symbol) | RangeDecoderBitDecode(probs + symbol, rd);
        #endif
      }
      break;
    }
  }
  while (symbol < 0x100);
  #ifdef _LZMA_LOC_OPT
  RC_FLUSH_VAR
  #endif
  return symbol;
}

#define kNumPosBitsMax 4
#define kNumPosStatesMax (1 << kNumPosBitsMax)

#define kLenNumLowBits 3
#define kLenNumLowSymbols (1 << kLenNumLowBits)
#define kLenNumMidBits 3
#define kLenNumMidSymbols (1 << kLenNumMidBits)
#define kLenNumHighBits 8
#define kLenNumHighSymbols (1 << kLenNumHighBits)

#define LenChoice 0
#define LenChoice2 (LenChoice + 1)
#define LenLow (LenChoice2 + 1)
#define LenMid (LenLow + (kNumPosStatesMax << kLenNumLowBits))
#define LenHigh (LenMid + (kNumPosStatesMax << kLenNumMidBits))
#define kNumLenProbs (LenHigh + kLenNumHighSymbols) 

int LzmaLenDecode(CProb *p, CRangeDecoder *rd, int posState)
{
  if(RangeDecoderBitDecode(p + LenChoice, rd) == 0)
    return RangeDecoderBitTreeDecode(p + LenLow +
        (posState << kLenNumLowBits), kLenNumLowBits, rd);
  if(RangeDecoderBitDecode(p + LenChoice2, rd) == 0)
    return kLenNumLowSymbols + RangeDecoderBitTreeDecode(p + LenMid +
        (posState << kLenNumMidBits), kLenNumMidBits, rd);
  return kLenNumLowSymbols + kLenNumMidSymbols + 
      RangeDecoderBitTreeDecode(p + LenHigh, kLenNumHighBits, rd);
}

#define kNumStates 12
#define kNumLitStates 7

#define kStartPosModelIndex 4
#define kEndPosModelIndex 14
#define kNumFullDistances (1 << (kEndPosModelIndex >> 1))

#define kNumPosSlotBits 6
#define kNumLenToPosStates 4

#define kNumAlignBits 4
#define kAlignTableSize (1 << kNumAlignBits)

#define kMatchMinLen 2

#define IsMatch 0
#define IsRep (IsMatch + (kNumStates << kNumPosBitsMax))
#define IsRepG0 (IsRep + kNumStates)
#define IsRepG1 (IsRepG0 + kNumStates)
#define IsRepG2 (IsRepG1 + kNumStates)
#define IsRep0Long (IsRepG2 + kNumStates)
#define PosSlot (IsRep0Long + (kNumStates << kNumPosBitsMax))
#define SpecPos (PosSlot + (kNumLenToPosStates << kNumPosSlotBits))
#define Align (SpecPos + kNumFullDistances - kEndPosModelIndex)
#define LenCoder (Align + kAlignTableSize)
#define RepLenCoder (LenCoder + kNumLenProbs)
#define Literal (RepLenCoder + kNumLenProbs)

#if Literal != LZMA_BASE_SIZE
StopCompilingDueBUG
#endif

int LzmaDecodeProperties(CLzmaProperties *propsRes, const unsigned char *propsData, int size)
{
  unsigned char prop0;
  if (size < LZMA_PROPERTIES_SIZE)
    return LZMA_RESULT_DATA_ERROR;
  prop0 = propsData[0];
  if (prop0 >= (9 * 5 * 5))
    return LZMA_RESULT_DATA_ERROR;
  {
    for (propsRes->pb = 0; prop0 >= (9 * 5); propsRes->pb++, prop0 -= (9 * 5));
    for (propsRes->lp = 0; prop0 >= 9; propsRes->lp++, prop0 -= 9);
    propsRes->lc = prop0;
    /*
    unsigned char remainder = (unsigned char)(prop0 / 9);
    propsRes->lc = prop0 % 9;
    propsRes->pb = remainder / 5;
    propsRes->lp = remainder % 5;
    */
  }

  #ifdef _LZMA_OUT_READ
  {
    int i;
    propsRes->DictionarySize = 0;
    for (i = 0; i < 4; i++)
      propsRes->DictionarySize += (UInt32)(propsData[1 + i]) << (i * 8);
    if (propsRes->DictionarySize == 0)
      propsRes->DictionarySize = 1;
  }
  #endif
  return LZMA_RESULT_OK;
}