/* K=9 r=1/2 Viterbi decoder for MMX * Copyright Feb 2004, Phil Karn, KA9Q * May be used under the terms of the GNU Lesser General Public License (LGPL) */#include <stdio.h>#include <stdlib.h>#include <memory.h>#include <mmintrin.h>#include "fec.h"typedef union { char c[256]; __m64 v[32];} decision_t;typedef union { unsigned char c[256]; __m64 v[32];} metric_t;unsigned char Mettab29_1[256][128] __attribute__ ((aligned(8)));unsigned char Mettab29_2[256][128] __attribute__ ((aligned(8)));static int Init = 0;/* State info for instance of Viterbi decoder * Don't change this without also changing references in mmxbfly29.s! */struct v29 {  metric_t metrics1; /* path metric buffer 1 */  metric_t metrics2; /* path metric buffer 2 */  decision_t *dp;          /* Pointer to current decision */  metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */  decision_t *decisions;   /* Beginning of decisions for block */};/* Create a new instance of a Viterbi decoder */void *create_viterbi29_mmx(int len){  struct v29 *vp;  if(Init == 0){    int polys[2] = {V29POLYA,V29POLYB};    set_viterbi29_polynomial_mmx(polys);  }  if((vp = (struct v29 *)malloc(sizeof(struct v29))) == NULL)    return NULL;  if((vp->decisions = (decision_t *)malloc((len+8)*sizeof(decision_t))) == NULL){    free(vp);    return NULL;  }  init_viterbi29(vp,0);  return vp;}void set_viterbi29_polynomial_mmx(int polys[2]){  int state;  for(state=0;state < 128;state++){    int symbol;    for(symbol = 0;symbol < 256;symbol++){      int sym;      sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0);      Mettab29_1[symbol][state] = (sym ? (255-symbol):symbol) / 16;      sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0);      Mettab29_2[symbol][state] = (sym ? (255-symbol):symbol) / 16;    }  }  Init++;}/* Initialize Viterbi decoder for start of new frame */int init_viterbi29_mmx(void *p,int starting_state){  struct v29 *vp = p;  int i;  if(p == NULL)    return -1;  for(i=0;i<256;i++)    vp->metrics1.c[i] = 63;  vp->old_metrics = &vp->metrics1;  vp->new_metrics = &vp->metrics2;  vp->dp = vp->decisions;  vp->old_metrics->c[starting_state & 255] = 0; /* Bias known start state */  return 0;}/* Viterbi chainback */int chainback_viterbi29_mmx(      void *p,      unsigned char *data, /* Decoded output data */      unsigned int nbits, /* Number of data bits */      unsigned int endstate){ /* Terminal encoder state */  struct v29 *vp = (struct v29 *)p;  decision_t *d;  if(p == NULL)    return -1;  d = (decision_t *)vp->decisions;  endstate &= 255;  d += 8; /* Look past tail */  while(nbits-- != 0){    int k;    k = d[nbits].c[endstate] & 1;    data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);  }  return 0;}/* Delete instance of a Viterbi decoder */void delete_viterbi29_mmx(void *p){  struct v29 *vp = p;  if(vp != NULL){    free(vp->decisions);    free(vp);  }}