parity.c

Viterbi编码解码算法

#include <stdio.h>

unsigned char Partab[256];
extern int P_init;

/* Create 256-entry odd-parity lookup table
 * Needed only on non-ia32 machines
 */
void partab_init(void){
  int i,cnt,ti;

  /* Initialize parity lookup table */
  for(i=0;i<256;i++){
    cnt = 0;
    ti = i;
    while(ti){
      if(ti & 1)
	cnt++;
      ti >>= 1;
    }
    Partab[i] = cnt & 1;
  }
  P_init=1;
}