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114 lines
2.9 KiB
114 lines
2.9 KiB
4 months ago
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/* K=7 r=1/2 Viterbi decoder for SSE
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* 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 <xmmintrin.h>
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#include "fec.h"
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typedef union { unsigned char c[64]; } metric_t;
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typedef union { unsigned long w[2]; unsigned char c[8]; __m64 v[1];} decision_t;
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union branchtab27 { unsigned char c[32]; __m64 v[4];} Branchtab27_sse[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 ssebfly27.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,*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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/* Create a new instance of a Viterbi decoder */
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void *create_viterbi27_sse(int len){
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struct v27 *vp;
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if(!Init){
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int polys[2] = { V27POLYA, V27POLYB };
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set_viterbi27_polynomial_sse(polys);
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}
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if((vp = malloc(sizeof(struct v27))) == NULL)
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return NULL;
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if((vp->decisions = malloc((len+6)*sizeof(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(vp,0);
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return vp;
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}
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void set_viterbi27_polynomial_sse(int polys[2]){
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int state;
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for(state=0;state < 32;state++){
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Branchtab27_sse[0].c[state] = (polys[0] < 0) ^ parity((2*state) & abs(polys[0])) ? 255 : 0;
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Branchtab27_sse[1].c[state] = (polys[1] < 0) ^ parity((2*state) & abs(polys[1])) ? 255 : 0;
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}
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Init++;
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}
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/* Initialize Viterbi decoder for start of new frame */
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int init_viterbi27_sse(void *p,int starting_state){
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struct v27 *vp = p;
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int i;
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if(p == NULL)
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return -1;
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for(i=0;i<64;i++)
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vp->metrics1.c[i] = 63;
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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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/* Viterbi chainback */
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int chainback_viterbi27_sse(
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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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struct v27 *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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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 %= 64;
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endstate <<= 2;
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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 += 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)/8] >> ((endstate>>2)%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_viterbi27_sse(void *p){
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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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