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
10typedef union { char c[64]; __m64 v[8];} decision_t;
11typedef union { unsigned char c[64]; __m64 v[8];} metric_t;
12
13unsigned char Mettab27_1[256][32] __attribute__ ((aligned(16)));
14unsigned char Mettab27_2[256][32] __attribute__ ((aligned(16)));
15static 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 */
20struct 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 */
29int 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
45void 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 */
65void *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 */
84int 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 */
108void 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