rar2decoder.cpp

7-Zip 是一款号称有着现今最高压缩比的压缩软件

// Rar2Decoder.cpp
// According to unRAR license, this code may not be used to develop
// a program that creates RAR archives
 
#include "StdAfx.h"

#include "Rar2Decoder.h"

namespace NCompress {
namespace NRar2 {

namespace NMultimedia {

Byte CFilter::Decode(int &channelDelta, Byte deltaByte)
{
  D4 = D3;
  D3 = D2;
  D2 = LastDelta - D1;
  D1 = LastDelta;
  int predictedValue = ((8 * LastChar + K1 * D1 + K2 * D2 + K3 * D3 + K4 * D4 + K5 * channelDelta) >> 3);

  Byte realValue = (Byte)(predictedValue - deltaByte);
  int i = ((int)(signed char)deltaByte) << 3;

  Dif[0] += abs(i);
  Dif[1] += abs(i - D1);
  Dif[2] += abs(i + D1);
  Dif[3] += abs(i - D2);
  Dif[4] += abs(i + D2);
  Dif[5] += abs(i - D3);
  Dif[6] += abs(i + D3);
  Dif[7] += abs(i - D4);
  Dif[8] += abs(i + D4);
  Dif[9] += abs(i - channelDelta);
  Dif[10] += abs(i + channelDelta);

  channelDelta = LastDelta = (signed char)(realValue - LastChar);
  LastChar = realValue;

  if (((++ByteCount) & 0x1F) == 0)
  {
    UInt32 minDif = Dif[0];
    UInt32 numMinDif = 0;
    Dif[0] = 0;
    for (i = 1; i < sizeof(Dif) / sizeof(Dif[0]); i++)
    {
      if (Dif[i] < minDif)
      {
        minDif = Dif[i];
        numMinDif = i;
      }
      Dif[i] = 0;
    }
    switch(numMinDif)
    {
      case 1: if (K1 >= -16) K1--; break;
      case 2: if (K1 <   16) K1++; break;
      case 3: if (K2 >= -16) K2--; break;
      case 4: if (K2 <   16) K2++; break;
      case 5: if (K3 >= -16) K3--; break;
      case 6: if (K3 <   16) K3++; break;
      case 7: if (K4 >= -16) K4--; break;
      case 8: if (K4 <   16) K4++; break;
      case 9: if (K5 >= -16) K5--; break;
      case 10:if (K5 <   16) K5++; break;
    }
  }
  return realValue;
}
}

static const char *kNumberErrorMessage = "Number error";

static const UInt32 kHistorySize = 1 << 20;

static const int kNumStats = 11;

static const UInt32 kWindowReservSize = (1 << 22) + 256;

CDecoder::CDecoder():
  m_IsSolid(false)
{
}

void CDecoder::InitStructures()
{
  m_MmFilter.Init();
  for(int i = 0; i < kNumRepDists; i++)
    m_RepDists[i] = 0;
  m_RepDistPtr = 0;
  m_LastLength = 0;
  memset(m_LastLevels, 0, kMaxTableSize);
}

UInt32 CDecoder::ReadBits(int numBits) { return m_InBitStream.ReadBits(numBits); }

#define RIF(x) { if (!(x)) return false; }

bool CDecoder::ReadTables(void)
{
  Byte levelLevels[kLevelTableSize];
  Byte newLevels[kMaxTableSize];
  m_AudioMode = (ReadBits(1) == 1);

  if (ReadBits(1) == 0)
    memset(m_LastLevels, 0, kMaxTableSize);
  int numLevels;
  if (m_AudioMode)
  {
    m_NumChannels = ReadBits(2) + 1;
    if (m_MmFilter.CurrentChannel >= m_NumChannels)
      m_MmFilter.CurrentChannel = 0;
    numLevels = m_NumChannels * kMMTableSize;
  }
  else
    numLevels = kHeapTablesSizesSum;
 
  int i;
  for (i = 0; i < kLevelTableSize; i++)
    levelLevels[i] = (Byte)ReadBits(4);
  RIF(m_LevelDecoder.SetCodeLengths(levelLevels));
  i = 0;
  while (i < numLevels)
  {
    UInt32 number = m_LevelDecoder.DecodeSymbol(&m_InBitStream);
    if (number < kTableDirectLevels)
    {
      newLevels[i] = (Byte)((number + m_LastLevels[i]) & kLevelMask);
      i++;
    }
    else
    {
      if (number == kTableLevelRepNumber)
      {
        int t = ReadBits(2) + 3;
        for (int reps = t; reps > 0 && i < numLevels ; reps--, i++)
          newLevels[i] = newLevels[i - 1];
      }
      else
      {
        int num;
        if (number == kTableLevel0Number)
          num = ReadBits(3) + 3;
        else if (number == kTableLevel0Number2)
          num = ReadBits(7) + 11;
        else
          return false;
        for (;num > 0 && i < numLevels; num--)
          newLevels[i++] = 0;
      }
    }
  }
  if (m_AudioMode)
    for (i = 0; i < m_NumChannels; i++)
    {
      RIF(m_MMDecoders[i].SetCodeLengths(&newLevels[i * kMMTableSize]));
    }
  else
  {
    RIF(m_MainDecoder.SetCodeLengths(&newLevels[0]));
    RIF(m_DistDecoder.SetCodeLengths(&newLevels[kMainTableSize]));
    RIF(m_LenDecoder.SetCodeLengths(&newLevels[kMainTableSize + kDistTableSize]));
  }
  memcpy(m_LastLevels, newLevels, kMaxTableSize);
  return true;
}

bool CDecoder::ReadLastTables()
{
  // it differs a little from pure RAR sources;
  // UInt64 ttt = m_InBitStream.GetProcessedSize() + 2;
  // + 2 works for: return 0xFF; in CInBuffer::ReadByte.
  if (m_InBitStream.GetProcessedSize() + 7 <= m_PackSize) // test it: probably incorrect;
  // if (m_InBitStream.GetProcessedSize() + 2 <= m_PackSize) // test it: probably incorrect;
    if (m_AudioMode)
    {
      UInt32 symbol = m_MMDecoders[m_MmFilter.CurrentChannel].DecodeSymbol(&m_InBitStream);
      if (symbol == 256)
        return ReadTables();
      if (symbol >= kMMTableSize)
        return false;
    }
    else
    {
      UInt32 number = m_MainDecoder.DecodeSymbol(&m_InBitStream);
      if (number == kReadTableNumber)
        return ReadTables();
      if (number >= kMainTableSize)
        return false;
    }
  return true;
}

class CCoderReleaser
{
  CDecoder *m_Coder;
public:
  CCoderReleaser(CDecoder *coder): m_Coder(coder) {}
  ~CCoderReleaser()
  {
    m_Coder->ReleaseStreams();
  }
};

bool CDecoder::DecodeMm(UInt32 pos)
{
  while (pos-- > 0)
  {
    UInt32 symbol = m_MMDecoders[m_MmFilter.CurrentChannel].DecodeSymbol(&m_InBitStream);
    if (symbol == 256)
      return true;
    if (symbol >= kMMTableSize)
      return false;
    /*
    Byte byPredict = m_Predictor.Predict();
    Byte byReal = (Byte)(byPredict - (Byte)symbol);
    m_Predictor.Update(byReal, byPredict);
    */
    Byte byReal = m_MmFilter.Decode((Byte)symbol);
    m_OutWindowStream.PutByte(byReal);
    if (++m_MmFilter.CurrentChannel == m_NumChannels)
      m_MmFilter.CurrentChannel = 0;
  }
  return true;
}

bool CDecoder::DecodeLz(Int32 pos)
{
  while (pos > 0)
  {
    UInt32 number = m_MainDecoder.DecodeSymbol(&m_InBitStream);
    UInt32 length, distance;
    if (number < 256)
    {
      m_OutWindowStream.PutByte(Byte(number));
      pos--;
      continue;
    }
    else if (number >= kMatchNumber)
    {
      number -= kMatchNumber;
      length = kNormalMatchMinLen + UInt32(kLenStart[number]) +
        m_InBitStream.ReadBits(kLenDirectBits[number]);
      number = m_DistDecoder.DecodeSymbol(&m_InBitStream);
      if (number >= kDistTableSize)
        return false;
      distance = kDistStart[number] + m_InBitStream.ReadBits(kDistDirectBits[number]);
      if (distance >= kDistLimit3)
      {
        length += 2 - ((distance - kDistLimit4) >> 31);
        // length++;
        // if (distance >= kDistLimit4)
        //  length++;
      }
    }
    else if (number == kRepBothNumber)
    {
      length = m_LastLength;
      distance = m_RepDists[(m_RepDistPtr + 4 - 1) & 3];
    }
    else if (number < kLen2Number)
    {
      distance = m_RepDists[(m_RepDistPtr - (number - kRepNumber + 1)) & 3];
      number = m_LenDecoder.DecodeSymbol(&m_InBitStream);
      if (number >= kLenTableSize)
        return false;
      length = 2 + kLenStart[number] + m_InBitStream.ReadBits(kLenDirectBits[number]);
      if (distance >= kDistLimit2)
      {
        length++;
        if (distance >= kDistLimit3)
        {
          length += 2 - ((distance - kDistLimit4) >> 31);
          // length++;
          // if (distance >= kDistLimit4)
          //   length++;
        }
      }
    }
    else if (number < kReadTableNumber)
    {
      number -= kLen2Number;
      distance = kLen2DistStarts[number] +
        m_InBitStream.ReadBits(kLen2DistDirectBits[number]);
      length = 2;
    }
    else if (number == kReadTableNumber)
      return true;
    else
      return false;
    m_RepDists[m_RepDistPtr++ & 3] = distance;
    m_LastLength = length;
    if (!m_OutWindowStream.CopyBlock(distance, length))
      return false;
    pos -= length;
  }
  return true;
}

HRESULT CDecoder::CodeReal(ISequentialInStream *inStream,
    ISequentialOutStream *outStream, const UInt64 *inSize, const UInt64 *outSize,
    ICompressProgressInfo *progress)
{
  if (inSize == NULL || outSize == NULL)
    return E_INVALIDARG;

  if (!m_OutWindowStream.Create(kHistorySize))
    return E_OUTOFMEMORY;
  if (!m_InBitStream.Create(1 << 20))
    return E_OUTOFMEMORY;

  m_PackSize = *inSize;

  UInt64 pos = 0, unPackSize = *outSize;
  
  m_OutWindowStream.SetStream(outStream);
  m_OutWindowStream.Init(m_IsSolid);
  m_InBitStream.SetStream(inStream);
  m_InBitStream.Init();

  CCoderReleaser coderReleaser(this);
  if (!m_IsSolid)
  {
    InitStructures();
    if (unPackSize == 0)
    {
      if (m_InBitStream.GetProcessedSize() + 2 <= m_PackSize) // test it: probably incorrect;
        if (!ReadTables())
          return S_FALSE;
      return S_OK;
    }
    if (!ReadTables())
      return S_FALSE;
  }

  UInt64 startPos = m_OutWindowStream.GetProcessedSize();
  while(pos < unPackSize)
  {
    UInt32 blockSize = 1 << 20;
    if (blockSize > unPackSize - pos)
      blockSize = (UInt32)(unPackSize - pos);
    UInt64 blockStartPos = m_OutWindowStream.GetProcessedSize();
    if (m_AudioMode)
    {
      if (!DecodeMm(blockSize))
        return S_FALSE;
    }
    else
    {
      if (!DecodeLz((Int32)blockSize))
        return S_FALSE;
    }
    UInt64 globalPos = m_OutWindowStream.GetProcessedSize();
    pos = globalPos - blockStartPos;
    if (pos < blockSize)
      if (!ReadTables())
        return S_FALSE;
    pos = globalPos - startPos;
    if (progress != 0)
    {
      UInt64 packSize = m_InBitStream.GetProcessedSize();
      RINOK(progress->SetRatioInfo(&packSize, &pos));
    }
  }
  if (pos > unPackSize)
    return S_FALSE;

  if (!ReadLastTables())
    return S_FALSE;
  return m_OutWindowStream.Flush();
}

STDMETHODIMP CDecoder::Code(ISequentialInStream *inStream,
    ISequentialOutStream *outStream, const UInt64 *inSize, const UInt64 *outSize,
    ICompressProgressInfo *progress)
{
  try { return CodeReal(inStream, outStream, inSize, outSize, progress); }
  catch(const CInBufferException &e) { return e.ErrorCode; }
  catch(const CLZOutWindowException &e) { return e.ErrorCode; }
  catch(...) { return S_FALSE; }
}

STDMETHODIMP CDecoder::SetDecoderProperties2(const Byte *data, UInt32 size)
{
  if (size < 1)
    return E_INVALIDARG;
  m_IsSolid = (data[0] != 0);
  return S_OK;
}

}}