139 lines
3.2 KiB
C
139 lines
3.2 KiB
C
/* K=9 r=1/2 Viterbi decoder for SSE2
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* Copyright Feb 2004, Phil Karn, KA9Q
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* May be used under the terms of the GNU Lesser General Public License (LGPL)
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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 <emmintrin.h>
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#include "fec.h"
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typedef union {
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unsigned char c[256];
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__m128i v[16];
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} metric_t;
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typedef union {
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unsigned long w[8];
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unsigned char c[32];
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} decision_t;
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union branchtab29 {
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unsigned char c[128];
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} Branchtab29_sse2[2];
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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 sse2bfly29.s!
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*/
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struct v29 {
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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_viterbi29_sse2(void *p, int starting_state)
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{
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struct v29 *vp = p;
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int i;
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for (i = 0; i < 256; 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 & 255] = 0; /* Bias known start state */
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return 0;
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}
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void set_viterbi29_polynomial_sse2(int polys[2])
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{
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int state;
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for (state = 0; state < 128; state++) {
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Branchtab29_sse2[0].c[state] = (polys[0] < 0) ^ parity((2 * state) & abs(
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polys[0])) ? 255 : 0;
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Branchtab29_sse2[1].c[state] = (polys[1] < 0) ^ parity((2 * state) & abs(
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polys[1])) ? 255 : 0;
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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_viterbi29_sse2(int len)
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{
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void *p;
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struct v29 *vp;
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if (!Init) {
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int polys[2] = {V29POLYA, V29POLYB};
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set_viterbi29_polynomial(polys);
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}
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/* Ordinary malloc() only returns 8-byte alignment, we need 16 */
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if (posix_memalign(&p, sizeof(__m128i), sizeof(struct v29))) {
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return NULL;
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}
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vp = (struct v29 *)p;
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if ((p = malloc((len + 8) * sizeof(decision_t))) == NULL) {
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free(vp);
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return NULL;
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}
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vp->decisions = (decision_t *)p;
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init_viterbi29_sse2(vp, 0);
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return vp;
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}
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/* Viterbi chainback */
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int chainback_viterbi29_sse2(
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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 v29 *vp = 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 = vp->decisions;
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/* Make room beyond the end of the encoder register so we can
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* accumulate a full byte of decoded data
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*/
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endstate %= 256;
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/* The store into data[] only needs to be done every 8 bits.
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* But this avoids a conditional branch, and the writes will
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* combine in the cache anyway
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*/
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d += 8; /* 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 / 8] >> (endstate % 8)) & 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_viterbi29_sse2(void *p)
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{
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struct v29 *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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