arithmetic_coding.h

学过数据压缩的朋友都知道, arithmetic encode是为了弥补哈夫曼编码对浮点数压缩的问题而提出的, 希望对大家有帮助

/* DECLARATIONS USED FOR ARITHMETIC ENCODING AND DECODING */

/* (C) Copyright 1987, Radford Neal. 

   Permission is granted to use this program for research purposes. Please
   note that this code was written to provide performance figures. I am
   well aware that it is not documented to the standards of production
   code. You're on your own. */


/* SIZE OF ARITHMETIC CODE VALUES. */

#define Code_value_bits 16		/* Number of bits in a code value   */
typedef long code_value;		/* Type of an arithmetic code value */

#define Top_value (((long)1<<Code_value_bits)-1)      /* Largest code value */


/* HALF AND QUARTER POINTS IN THE CODE VALUE RANGE. */

#define First_qtr (Top_value/4+1)	/* Point after first quarter        */
#define Half	  (2*First_qtr)		/* Point after first half           */
#define Third_qtr (3*First_qtr)		/* Point after third quarter        */