lencoder.h

经过项目量产验证的代码.开发环境是sparc+vxworks. 这个LZMA是专门为sparc做的优化压缩,性能是最好的.

// LenCoder.h


#ifndef __LENCODER_H
#define __LENCODER_H

#include "BitTreeCoder.h"

const int kLenNumPosStatesBitsMax = 4;
const int kLenNumPosStatesMax = (1 << kLenNumPosStatesBitsMax);

const int kLenNumPosStatesBitsEncodingMax = 4;
const int kLenNumPosStatesEncodingMax = (1 << kLenNumPosStatesBitsEncodingMax);

const int kLenNumLowBits = 3;
const int kLenNumLowSymbols = 1 << kLenNumLowBits;
const int kLenNumMidBits = 3;
const int kLenNumMidSymbols = 1 << kLenNumMidBits;

const int kLenNumHighBits = 8;

const int kLenNumSymbolsTotal = kLenNumLowSymbols + kLenNumMidSymbols + (1 << kLenNumHighBits);

const int kLenNumSpecSymbols = kLenNumLowSymbols + kLenNumMidSymbols;

class CLenDecoder
{
  CBitDecoder m_Choice;
  CBitTreeDecoder3  m_LowCoder[kLenNumPosStatesMax];
  CBitDecoder m_Choice2;
  CBitTreeDecoder3  m_MidCoder[kLenNumPosStatesMax];
  CBitTreeDecoder8 m_HighCoder; 
  int m_NumPosStates;
public:
  void Create(int numPosStates)
    { m_NumPosStates = numPosStates; }
  void Init()
  {
    m_Choice.Init();
    for (int posState = 0; posState < m_NumPosStates; posState++)
    {
      m_LowCoder[posState].Init();
      m_MidCoder[posState].Init();
    }
    m_Choice2.Init();
    m_HighCoder.Init();
  }
  int Decode(CRangeDecoder *aRangeDecoder, int posState)
  {
    if(m_Choice.Decode(aRangeDecoder) == 0)
      return m_LowCoder[posState].Decode(aRangeDecoder);
    else
    {
      int symbol = kLenNumLowSymbols;
      if(m_Choice2.Decode(aRangeDecoder) == 0)
        symbol += m_MidCoder[posState].Decode(aRangeDecoder);
      else
      {
        symbol += kLenNumMidSymbols;
        symbol += m_HighCoder.Decode(aRangeDecoder);
      }
      return symbol;
    }
  }

};


#endif