encode27.c

来自「viterbi 1/2码率 长度k=7的编码译码程序」· C语言 代码 · 共 34 行

/* Encode standard input in the r=1/2 K=7 standard convolutional code.
 * Encoded output is big-endian, one byte per symbol, with 1 represented
 * by 255 and 0 by 0
 */

#include <stdio.h>
#include "viterbi27.h"

extern unsigned char Partab[];	/* Parity lookup table */

main(int argc,char *argv[])
{
  unsigned int encstate;
  int c,i;

  encstate = 0;
  while((c = getchar()) != EOF){
    for(i=7;i>=0;i--){
      encstate = (encstate << 1) | ((c >> 7) & 1);
      c <<= 1;
      /* 1-sym -> 255, 0-sym -> 0 */
      putchar(0 - Partab[encstate & POLYA]);
      putchar(0 - Partab[encstate & POLYB]);
    }
  }
  /* Generate tail */
  for(i=5;i>=0;i--){
    encstate = encstate << 1;
    putchar(0 - Partab[encstate & POLYA]);
    putchar(0 - Partab[encstate & POLYB]);
  }
  return 0;
}