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/* K=7 r=1/2 Viterbi decoder for MMX
* Copyright Feb 2004, Phil Karn, KA9Q
*/
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <mmintrin.h>
#include "fec.h"
typedef union { char c[64]; __m64 v[8];} decision_t;
typedef union { unsigned char c[64]; __m64 v[8];} metric_t;
unsigned char Mettab27_1[256][32] __attribute__ ((aligned(16)));
unsigned char Mettab27_2[256][32] __attribute__ ((aligned(16)));
static int Init = 0;
/* State info for instance of Viterbi decoder
* Don't change this without also changing references in mmxbfly27.s!
*/
struct v27 {
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 */
};
/* Initialize Viterbi decoder for start of new frame */
int init_viterbi27_mmx(void *p,int starting_state){
struct v27 *vp = (struct v27 *)p;
int i;
if(p == NULL)
return -1;
for(i=0;i<64;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 & 63] = 0; /* Bias known start state */
return 0;
}
void set_viterbi27_polynomial_mmx(int polys[2]){
int state;
for(state=0;state < 32;state++){
int symbol;
for(symbol = 0;symbol < 256;symbol++){
int sym;
sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0);
Mettab27_1[symbol][state] = (sym ? (255-symbol):symbol) / 16;
sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0);
Mettab27_2[symbol][state] = (sym ? (255-symbol):symbol) / 16;
}
}
Init++;
}
/* Create a new instance of a Viterbi decoder */
void *create_viterbi27_mmx(int len){
struct v27 *vp;
int polys[2] = { V27POLYA, V27POLYB };
if(Init == 0){
set_viterbi27_polynomial_mmx(polys);
}
if((vp = (struct v27 *)malloc(sizeof(struct v27))) == NULL)
return NULL;
if((vp->decisions = (decision_t *)malloc((len+6)*sizeof(decision_t))) == NULL){
free(vp);
return NULL;
}
init_viterbi27_mmx(vp,0);
return vp;
}
/* Viterbi chainback */
int chainback_viterbi27_mmx(
void *p,
unsigned char *data, /* Decoded output data */
unsigned int nbits, /* Number of data bits */
unsigned int endstate){ /* Terminal encoder state */
struct v27 *vp = (struct v27 *)p;
decision_t *d;
if(p == NULL)
return -1;
d = (decision_t *)vp->decisions;
endstate &= 63;
d += 6; /* Look past tail */
while(nbits-- != 0){
int k;
k = d[nbits].c[endstate>>2] & 1;
data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
}
return 0;
}
/* Delete instance of a Viterbi decoder */
void delete_viterbi27_mmx(void *p){
struct v27 *vp = p;
if(vp != NULL){
free(vp->decisions);
free(vp);
}
}
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