1 /* K=7 r=1/2 Viterbi decoder for MMX 2 * Copyright Feb 2004, Phil Karn, KA9Q 3 */ 4 #include <stdio.h> 5 #include <stdlib.h> 6 #include <memory.h> 7 #include <mmintrin.h> 8 #include "fec.h" 9 10 typedef union { char c[64]; __m64 v[8];} decision_t; 11 typedef union { unsigned char c[64]; __m64 v[8];} metric_t; 12 13 unsigned char Mettab27_1[256][32] __attribute__ ((aligned(16))); 14 unsigned char Mettab27_2[256][32] __attribute__ ((aligned(16))); 15 static int Init = 0; 16 17 /* State info for instance of Viterbi decoder 18 * Don't change this without also changing references in mmxbfly27.s! 19 */ 20 struct v27 { 21 metric_t metrics1; /* path metric buffer 1 */ 22 metric_t metrics2; /* path metric buffer 2 */ 23 decision_t *dp; /* Pointer to current decision */ 24 metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */ 25 decision_t *decisions; /* Beginning of decisions for block */ 26 }; 27 28 /* Initialize Viterbi decoder for start of new frame */ 29 int init_viterbi27_mmx(void *p,int starting_state){ 30 struct v27 *vp = (struct v27 *)p; 31 int i; 32 33 if(p == NULL) 34 return -1; 35 for(i=0;i<64;i++) 36 vp->metrics1.c[i] = 63; 37 38 vp->old_metrics = &vp->metrics1; 39 vp->new_metrics = &vp->metrics2; 40 vp->dp = vp->decisions; 41 vp->old_metrics->c[starting_state & 63] = 0; /* Bias known start state */ 42 return 0; 43 } 44 45 void set_viterbi27_polynomial_mmx(int polys[2]){ 46 int state; 47 48 for(state=0;state < 32;state++){ 49 int symbol; 50 for(symbol = 0;symbol < 256;symbol++){ 51 int sym; 52 53 sym = parity((2*state) & abs(polys[0])) ^ (polys[0] < 0); 54 Mettab27_1[symbol][state] = (sym ? (255-symbol):symbol) / 16; 55 56 sym = parity((2*state) & abs(polys[1])) ^ (polys[1] < 0); 57 Mettab27_2[symbol][state] = (sym ? (255-symbol):symbol) / 16; 58 } 59 } 60 Init++; 61 } 62 63 64 /* Create a new instance of a Viterbi decoder */ 65 void *create_viterbi27_mmx(int len){ 66 struct v27 *vp; 67 int polys[2] = { V27POLYA, V27POLYB }; 68 69 if(Init == 0){ 70 set_viterbi27_polynomial_mmx(polys); 71 } 72 if((vp = (struct v27 *)malloc(sizeof(struct v27))) == NULL) 73 return NULL; 74 75 if((vp->decisions = (decision_t *)malloc((len+6)*sizeof(decision_t))) == NULL){ 76 free(vp); 77 return NULL; 78 } 79 init_viterbi27_mmx(vp,0); 80 return vp; 81 } 82 83 /* Viterbi chainback */ 84 int chainback_viterbi27_mmx( 85 void *p, 86 unsigned char *data, /* Decoded output data */ 87 unsigned int nbits, /* Number of data bits */ 88 unsigned int endstate){ /* Terminal encoder state */ 89 90 struct v27 *vp = (struct v27 *)p; 91 decision_t *d; 92 93 if(p == NULL) 94 return -1; 95 d = (decision_t *)vp->decisions; 96 endstate &= 63; 97 d += 6; /* Look past tail */ 98 while(nbits-- != 0){ 99 int k; 100 101 k = d[nbits].c[endstate>>2] & 1; 102 data[nbits>>3] = endstate = (endstate >> 1) | (k << 7); 103 } 104 return 0; 105 } 106 107 /* Delete instance of a Viterbi decoder */ 108 void delete_viterbi27_mmx(void *p){ 109 struct v27 *vp = p; 110 111 if(vp != NULL){ 112 free(vp->decisions); 113 free(vp); 114 } 115 } 116
