/*   Multiply-free Arithmetic Coding Implementation - Compression version 0.0.0
 
 
     Copyright Feb. 1993
              
     Gordon V. Cormack  Feb. 1993
     University of Waterloo
     cormack@uwaterloo.ca
 
 
     All rights reserved.
 
     This code and the algorithms herein are the property of Gordon V. Cormack.
 
     Neither the code nor any algorithm herein may be included in any software,
     device, or process which is sold, exchanged for profit, or for which a 
     licence or royalty fee is charged.
 
     Permission is granted to use this code for educational, research, or
     commercial purposes, provided this notice is included, and provided this
     code is not used as described in the above paragraph.
 
*/
 
/* 
     This code uses a one-byte finite state predictor to drive an arithmetic
     coder for data compression.  It should give compression nearly identical
     to one-byte huffman coding.
 
     Find a better predictor, and you'll have a better compressor!

     It uses no floating point, no multiplies, no divides during compression.

     ***EOF is handled in a non-general way; (char)EOF is stuffed into the
     compressed stream.
 
*/
 
#define THRESH 0

#include <stdio.h>

typedef int shrt;

shrt diff[0x10000];

shrt inc0tab [0x10000];
shrt inc1tab [0x10000];

shrt cnt[0x100];


#define INC0(x) pinc0tab[(unsigned shrt)(x)]
#define INC1(x) pinc1tab[(unsigned shrt)(x)]
#define DIFF(x) pdiff[(unsigned shrt)(x)]
#define CNT1(x) ((x&0xff)+1)
#define CNT0(x) ((x>>8)+1)

init() {
   int i,j;
   for (i=0;i<256;i++) for (j=0;j<256;j++) {
     if (i != 255)
        inc0tab[(i<<8)+j] = ((i+1)<<8) + j;
     else
        inc0tab[(i<<8)+j] = (127<<8) + (j>>1);
     if (j != 255)
        inc1tab[(i<<8)+j] = (i<<8) + j + 1;
     else
        inc1tab[(i<<8)+j] = ((i>>1)<<8) + 127;
     if (i < j) {
        diff[(i<<8)+j] = 175.0 * (i+1) / (i+j+2);
        if (!diff[(i<<8)+j]) diff[(i<<8)+j]++;
     }else{
        diff[(i<<8)+j] = -175.0 * (j+1) / (i+j+2);
        if (!diff[(i<<8)+j]) diff[(i<<8)+j]--;
     }
   }
}


main(){

register shrt *pinc0tab, *pinc1tab, *pdiff; 


register int space = 0xff,
    min = 0,
   index,
    i;
unsigned register char c = 0;

unsigned register last = 0;
register count = -24;

init();

pinc0tab = inc0tab;
pinc1tab = inc1tab;
pdiff = diff;

do{
   register mask;

   c = 0xff & getchar();
   index = 1;
   for (mask = 0x80;mask;mask>>=1){
         register l = last  + index;
         register a = cnt[l];
         register x = DIFF(a);
         if (x>0) 
            if (c & mask) { 
               space -=x;
               cnt[l] = INC1(a);
               index += index + 1;
            }else { 
               min += space-x;
               space = x;
               cnt[l] = INC0(a);
               index += index;
            }
         else 
            if (!(c & mask)) {
               space +=x; 
               cnt[l] = INC0(a);
               index += index;
            } else { 
              min += space+x; 
              space = -x;
              cnt[l] = INC1(a);
              index += index+1;
            }
      while ((space) < 128) {
         space <<= 1;
         min <<= 1;
         if (!++count) {
            count = -8;
            putchar(min >> 24);
            min &= 0xffffff;
            if (0xffffff - min < space){
                space = 0xffffff - min;
                }
            }
         }
      }
   }
while (c != (unsigned char)EOF);
fprintf(stderr,"count %d min %x minshift %x\n",count&7,min,min<<(8-(count&0x7)));
min <<= 8-(count&7);
putchar(min>>24);
putchar((min>>16) & 0xff);
putchar((min>>8) & 0xff);
putchar(min & 0x00ff);

}