133 lines
3.0 KiB
C
133 lines
3.0 KiB
C
/* K=7 r=1/2 Viterbi decoder for MMX
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* Copyright Feb 2004, Phil Karn, KA9Q
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <memory.h>
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#include <mmintrin.h>
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#include "fec.h"
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typedef union {
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char c[64];
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__m64 v[8];
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} decision_t;
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typedef union {
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unsigned char c[64];
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__m64 v[8];
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} metric_t;
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unsigned char Mettab27_1[256][32] __attribute__((aligned(16)));
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unsigned char Mettab27_2[256][32] __attribute__((aligned(16)));
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static int Init = 0;
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/* State info for instance of Viterbi decoder
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* Don't change this without also changing references in mmxbfly27.s!
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*/
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struct v27 {
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metric_t metrics1; /* path metric buffer 1 */
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metric_t metrics2; /* path metric buffer 2 */
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decision_t *dp; /* Pointer to current decision */
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metric_t *old_metrics,
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*new_metrics; /* Pointers to path metrics, swapped on every bit */
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decision_t *decisions; /* Beginning of decisions for block */
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};
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/* Initialize Viterbi decoder for start of new frame */
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int init_viterbi27_mmx(void *p, int starting_state)
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{
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struct v27 *vp = (struct v27 *)p;
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int i;
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if (p == NULL) {
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return -1;
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}
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for (i = 0; i < 64; i++) {
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vp->metrics1.c[i] = 63;
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}
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vp->old_metrics = &vp->metrics1;
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vp->new_metrics = &vp->metrics2;
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vp->dp = vp->decisions;
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vp->old_metrics->c[starting_state & 63] = 0; /* Bias known start state */
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return 0;
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}
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void set_viterbi27_polynomial_mmx(int polys[2])
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{
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int state;
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for (state = 0; state < 32; state++) {
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int symbol;
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for (symbol = 0; symbol < 256; symbol++) {
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int sym;
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sym = parity((2 * state) & abs(polys[0])) ^ (polys[0] < 0);
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Mettab27_1[symbol][state] = (sym ? (255 - symbol) : symbol) / 16;
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sym = parity((2 * state) & abs(polys[1])) ^ (polys[1] < 0);
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Mettab27_2[symbol][state] = (sym ? (255 - symbol) : symbol) / 16;
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}
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}
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Init++;
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}
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/* Create a new instance of a Viterbi decoder */
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void *create_viterbi27_mmx(int len)
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{
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struct v27 *vp;
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int polys[2] = { V27POLYA, V27POLYB };
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if (Init == 0) {
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set_viterbi27_polynomial_mmx(polys);
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}
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if ((vp = (struct v27 *)malloc(sizeof(struct v27))) == NULL) {
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return NULL;
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}
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if ((vp->decisions = (decision_t *)malloc((len + 6) * sizeof(
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decision_t))) == NULL) {
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free(vp);
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return NULL;
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}
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init_viterbi27_mmx(vp, 0);
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return vp;
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}
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/* Viterbi chainback */
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int chainback_viterbi27_mmx(
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void *p,
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unsigned char *data, /* Decoded output data */
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unsigned int nbits, /* Number of data bits */
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unsigned int endstate) /* Terminal encoder state */
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{
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struct v27 *vp = (struct v27 *)p;
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decision_t *d;
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if (p == NULL) {
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return -1;
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}
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d = (decision_t *)vp->decisions;
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endstate &= 63;
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d += 6; /* Look past tail */
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while (nbits-- != 0) {
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int k;
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k = d[nbits].c[endstate >> 2] & 1;
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data[nbits >> 3] = endstate = (endstate >> 1) | (k << 7);
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}
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return 0;
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}
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/* Delete instance of a Viterbi decoder */
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void delete_viterbi27_mmx(void *p)
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{
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struct v27 *vp = p;
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if (vp != NULL) {
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free(vp->decisions);
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free(vp);
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}
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}
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