adaarithcoder.h

自适应算术编码的实现

//  AdaArithCoder.h : 自适应算术编码器和解码器的类定义
// 
//  Author:    Shen Hongwei
//  Date:      Nov.10, 2005
//  Location:  Beijing, China
// 

#pragma once
#include "DataCompression.h"

//#define BYTE_TAG    
#define SHORT_TAG
// #define LONG_TAG

#ifdef BYTE_TAG
	typedef unsigned char TagType;
    #define MSB_MASK 0x80
    #define MSB2_MASK 0x40
    #define TAG_LENG 8
    #define LSB_MASK 0x01
    #define AND_LSB_MASK 0xfe
    #define TOP_VALUE 0xff
#endif

#ifdef SHORT_TAG
	typedef unsigned short TagType;
    #define MSB_MASK 0x8000
    #define MSB2_MASK 0x4000
    #define TAG_LENG 16
    #define LSB_MASK 0x0001
    #define AND_LSB_MASK 0xfffe
    #define TOP_VALUE 0xffff
#endif

#ifdef LONG_TAG
	typedef unsigned long TagType;
    #define MSB_MASK 0x80000000
    #define MSB2_MASK 0x40000000
    #define TAG_LENG 32
    #define LSB_MASK 0x00000001
    #define AND_LSB_MASK 0xfffffffe
    #define TOP_VALUE 0xffffffff
#endif


class AdaArithCoder :
	public Coder
{
public:
	AdaArithCoder(void);
	~AdaArithCoder(void);
	void  Init(BitIO * bit_in, BitIO * bit_out);
    void  Init(BitIO * in, BitIO * out, unsigned long i_leng); 
	int   Run(void);
	bool  GenNextCode();
    void  SetDebugMode(int mode);
private:
	const static tbSize = 256;     // unsigned char的表示范围 
	const static tagSize = sizeof(TagType); 
	TagType  L, U;
	TagType  CumCount[tbSize+1];
	TagType  TotalCount;
	void     Count(unsigned char c);   // 统计各个字符出现的次数
	inline bool CheckE3(void) { return(!(L&MSB_MASK) && L&MSB2_MASK && U&MSB_MASK && !(U&MSB2_MASK)); };  // 检查是否满足condition 3
	inline char MSB(TagType number) { return ( (number & MSB_MASK) >> (TAG_LENG-1) ); }                   // 取number的最高位
};

class AdaArithDecoder :
	public Coder
{
public:
	AdaArithDecoder(void);
	~AdaArithDecoder(void);
	bool  GenNextCode();
	void  Init(BitIO * bit_in, BitIO * bit_out);
    void  Init(BitIO * in, BitIO * out, unsigned long i_leng); 
	int   Run(void);
    void  SetDebugMode(int mode);
private:
	const static tbSize = 256;              // unsigned char的表示范围 
	const static tagSize = sizeof(TagType); 
	TagType  L, U;
	TagType  CumCount[tbSize+1];
	TagType  TotalCount;
	bool     ReadATag(TagType & tag);
	void     Count(unsigned char c);             // 统计各个字符出现的次数
	void     CompareWithOriginal(char * value);  // for debug
	inline bool CheckE3(void) { return(!(L&MSB_MASK) && L&MSB2_MASK && U&MSB_MASK && !(U&MSB2_MASK)); }; // 检查是否满足condition 3
	inline char MSB(TagType number) { return ( (number & MSB_MASK) >> (TAG_LENG-1) ); }                  // 取number的最高位
};