rangedecoder.h

对浮点型数据进行压缩

/*
===============================================================================

  FILE:  rangedecoder.h
  
  CONTENTS:
      
  PROGRAMMERS:
  
    martin [e-mail]
  
  COPYRIGHT:
  
    Copyright (C) 2003 Martin Isenburg ([e-mail])
    
    This software 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.
  
  CHANGE HISTORY:
  
    14 January 2003 -- adapted from michael schindler's code before SIGGRAPH
  
===============================================================================
*/
#ifndef RANGEDECODER_H
#define RANGEDECODER_H

#include <stdio.h>

#include <iostream>

using namespace std;

#include "rangemodel.h"

class RangeDecoder
{
public:

/* Start the decoder                                         */
  RangeDecoder(unsigned char* chars, int number_chars);
  RangeDecoder(FILE* fp);

  ~RangeDecoder();

/* Decode with modelling                                     */
  unsigned int decode(RangeModel* rm);

/* Decode a range without modelling                          */
  unsigned int decode(unsigned int range);

/* Decode an unsigned char without modelling                 */
  unsigned char decodeByte();

/* Decode an unsigned short without modelling                */
  unsigned short decodeShort();

/* Decode an unsigned int without modelling                  */
  unsigned int decodeInt();

/* Decode a float without modelling (endian-ness dependent)  */
  float decodeFloat();

/* Finish decoding                                           */
  void done();

private:
/* Calculate culmulative frequency for next symbol. Does NO update!*/
/* tot_f is the total frequency                              */
/* or: totf is 1<<shift                                      */
/* returns the <= culmulative frequency                      */
  unsigned int culshift( unsigned int shift );

/* Update decoding state                                     */
/* sy_f is the interval length (frequency of the symbol)     */
/* lt_f is the lower end (frequency sum of < symbols)        */
/* tot_f is the total interval length (total frequency sum)  */
  void update( unsigned int sy_f, unsigned int lt_f, unsigned int tot_f);

  inline void normalize();
  inline unsigned int inbyte();

  FILE* fp;

  unsigned char* chars;
  int current_char;
  int number_chars;

  unsigned int low;         /* low end of interval */
  unsigned int range;       /* length of interval */
  unsigned int help;        /* bytes_to_follow resp. intermediate value */
  unsigned char buffer;      /* buffer for output */
};

#endif