1/* K=9 r=1/2 Viterbi decoder for SSE
2 * Copyright Feb 2004, Phil Karn, KA9Q
3 * May be used under the terms of the GNU Lesser General Public License (LGPL)
4 */
5#include <stdio.h>
6#include <stdlib.h>
7#include <memory.h>
8#include <xmmintrin.h>
9#include "fec.h"
10
11typedef union { unsigned char w[256]; __m64 v[32];} metric_t;
12typedef union { unsigned long w[8]; unsigned char c[32]; __m64 v[4];} decision_t;
13
14union branchtab29 { unsigned char c[128]; } Branchtab29_sse[2];
15static int Init = 0;
16
17/* State info for instance of Viterbi decoder
18 * Don't change this without also changing references in [mmx|sse|sse2]bfly29.s!
19 */
20struct v29 {
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/* Create a new instance of a Viterbi decoder */
29void *create_viterbi29_sse(int len){
30  struct v29 *vp;
31
32  if(!Init){
33    int polys[2] = { V29POLYA,V29POLYB };
34
35    set_viterbi29_polynomial_sse(polys);
36  }
37  if((vp = (struct v29 *)malloc(sizeof(struct v29))) == NULL)
38    return NULL;
39  if((vp->decisions = (decision_t *)malloc((len+8)*sizeof(decision_t))) == NULL){
40    free(vp);
41    return NULL;
42  }
43  init_viterbi29(vp,0);
44  return vp;
45}
46
47void set_viterbi29_polynomial_sse(int polys[2]){
48  int state;
49
50  for(state=0;state < 128;state++){
51    Branchtab29_sse[0].c[state] = (polys[0] < 0) ^ parity((2*state) & abs(polys[0])) ? 255 : 0;
52    Branchtab29_sse[1].c[state] = (polys[1] < 0) ^ parity((2*state) & abs(polys[1])) ? 255 : 0;
53  }
54  Init++;
55}
56
57/* Initialize Viterbi decoder for start of new frame */
58int init_viterbi29_sse(void *p,int starting_state){
59  struct v29 *vp = p;
60  int i;
61
62  if(p == NULL)
63    return -1;
64  for(i=0;i<256;i++)
65    vp->metrics1.w[i] = 200;
66
67  vp->old_metrics = &vp->metrics1;
68  vp->new_metrics = &vp->metrics2;
69  vp->dp = vp->decisions;
70  vp->old_metrics->w[starting_state & 255] = 0; /* Bias known start state */
71  return 0;
72}
73
74/* Viterbi chainback */
75int chainback_viterbi29_sse(
76      void *p,
77      unsigned char *data, /* Decoded output data */
78      unsigned int nbits, /* Number of data bits */
79      unsigned int endstate){ /* Terminal encoder state */
80  struct v29 *vp = p;
81  decision_t *d;
82
83  if(p == NULL)
84    return -1;
85  d = vp->decisions;
86  /* Make room beyond the end of the encoder register so we can
87   * accumulate a full byte of decoded data
88   */
89  endstate %= 256;
90
91  /* The store into data[] only needs to be done every 8 bits.
92   * But this avoids a conditional branch, and the writes will
93   * combine in the cache anyway
94   */
95  d += 8; /* Look past tail */
96  while(nbits-- != 0){
97    int k;
98
99    k = (d[nbits].c[endstate/8] >> (endstate%8)) & 1;
100    data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
101  }
102  return 0;
103}
104
105
106/* Delete instance of a Viterbi decoder */
107void delete_viterbi29_sse(void *p){
108  struct v29 *vp = p;
109
110  if(vp != NULL){
111    free(vp->decisions);
112    free(vp);
113  }
114}
115