Bill Yi | 4e213d5 | 2015-06-23 13:53:11 -0700 | [diff] [blame] | 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 | |
| 11 | typedef union { unsigned char w[256]; __m64 v[32];} metric_t; |
| 12 | typedef union { unsigned long w[8]; unsigned char c[32]; __m64 v[4];} decision_t; |
| 13 | |
| 14 | union branchtab29 { unsigned char c[128]; } Branchtab29_sse[2]; |
| 15 | static 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 | */ |
| 20 | struct 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 */ |
| 29 | void *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 | |
| 47 | void 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 */ |
| 58 | int 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 */ |
| 75 | int 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 */ |
| 107 | void delete_viterbi29_sse(void *p){ |
| 108 | struct v29 *vp = p; |
| 109 | |
| 110 | if(vp != NULL){ |
| 111 | free(vp->decisions); |
| 112 | free(vp); |
| 113 | } |
| 114 | } |