lencoder.h

SFC游戏模拟器 snes9x 1.43 的原代码

/*
Copyright (C) 2002 Andrea Mazzoleni ( http://advancemame.sf.net )
Copyright (C) 2001-4 Igor Pavlov ( http://www.7-zip.org )

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#ifndef __LENCODER_H
#define __LENCODER_H

#include "btreecd.h"

namespace NLength {

const UINT32 kNumPosStatesBitsMax = 4;
const int kNumPosStatesMax = (1 << kNumPosStatesBitsMax);


const int kNumPosStatesBitsEncodingMax = 4;
const int kNumPosStatesEncodingMax = (1 << kNumPosStatesBitsEncodingMax);


const int kNumMoveBits = 5;

const int kNumLenBits = 3;
const int kNumLowSymbols = 1 << kNumLenBits;
const int kNumMidBits = 3;
const int kNumMidSymbols = 1 << kNumMidBits;

const int kNumHighBits = 8;

const int kNumSymbolsTotal = kNumLowSymbols + kNumMidSymbols + (1 << kNumHighBits);

const int kNumSpecSymbols = kNumLowSymbols + kNumMidSymbols;

class CDecoder
{
  CMyBitDecoder<kNumMoveBits> m_Choice;
  CBitTreeDecoder<kNumMoveBits, kNumLenBits>  m_LowCoder[kNumPosStatesMax];
  CMyBitDecoder<kNumMoveBits> m_Choice2;
  CBitTreeDecoder<kNumMoveBits, kNumMidBits>  m_MidCoder[kNumPosStatesMax];
  CBitTreeDecoder<kNumMoveBits, kNumHighBits> m_HighCoder; 
  UINT32 m_NumPosStates;
public:
  void Create(UINT32 aNumPosStates)
    { m_NumPosStates = aNumPosStates; }
  void Init()
  {
    m_Choice.Init();
    for (UINT32 aPosState = 0; aPosState < m_NumPosStates; aPosState++)
    {
      m_LowCoder[aPosState].Init();
      m_MidCoder[aPosState].Init();
    }
    m_Choice2.Init();
    m_HighCoder.Init();
  }
  UINT32 Decode(CMyRangeDecoder *aRangeDecoder, UINT32 aPosState)
  {
    if(m_Choice.Decode(aRangeDecoder) == 0)
      return m_LowCoder[aPosState].Decode(aRangeDecoder);
    else
    {
      UINT32 aSymbol = kNumLowSymbols;
      if(m_Choice2.Decode(aRangeDecoder) == 0)
        aSymbol += m_MidCoder[aPosState].Decode(aRangeDecoder);
      else
      {
        aSymbol += kNumMidSymbols;
        aSymbol += m_HighCoder.Decode(aRangeDecoder);
      }
      return aSymbol;
    }
  }

};

}


#endif