parity.h

Viterbi编码解码算法

#ifndef _PARITY_H_
#define _PARITY_H_
#ifdef __i386__
static inline int parityb(unsigned char x){
  __asm__ __volatile__ ("test $0xff,%1;setpo %0" : "=r"(x) : "g" (x));
  return x;
}
#else
static inline int parityb(unsigned char x){
  extern unsigned char Partab[256];
  extern int P_init;
  if(!P_init){
    partab_init();
  }
  return Partab[x];
}
#endif


static inline int parity(int x){
  /* Fold down to one byte */
  x ^= (x >> 16);
  x ^= (x >> 8);
  return parityb(x);
}

#endif /* _PARITY_H_ */