1 /*
2 * Copyright (c) 2007 - 2015 Joseph Gaeddert
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a copy
5 * of this software and associated documentation files (the "Software"), to deal
6 * in the Software without restriction, including without limitation the rights
7 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 * copies of the Software, and to permit persons to whom the Software is
9 * furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice shall be included in
12 * all copies or substantial portions of the Software.
13 *
14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 * THE SOFTWARE.
21 */
22
23 //
24 // FEC, repeat code
25 //
26
27 #include <stdio.h>
28 #include <stdlib.h>
29 #include <string.h>
30 #include "liquid.internal.h"
31
32 // create rep5 codec object
fec_rep5_create(void * _opts)33 fec fec_rep5_create(void * _opts)
34 {
35 fec q = (fec) malloc(sizeof(struct fec_s));
36
37 q->scheme = LIQUID_FEC_REP5;
38 q->rate = fec_get_rate(q->scheme);
39
40 q->encode_func = &fec_rep5_encode;
41 q->decode_func = &fec_rep5_decode;
42 q->decode_soft_func = &fec_rep5_decode_soft;
43
44 return q;
45 }
46
47 // destroy rep5 object
fec_rep5_destroy(fec _q)48 void fec_rep5_destroy(fec _q)
49 {
50 free(_q);
51 }
52
53 // print rep5 object
fec_rep5_print(fec _q)54 void fec_rep5_print(fec _q)
55 {
56 printf("fec_rep5 [r: %3.2f]\n", _q->rate);
57 }
58
59 // encode block of data using rep5 encoder
60 //
61 // _q : encoder/decoder object
62 // _dec_msg_len : decoded message length (number of bytes)
63 // _msg_dec : decoded message [size: 1 x _dec_msg_len]
64 // _msg_enc : encoded message [size: 1 x 5*_dec_msg_len]
fec_rep5_encode(fec _q,unsigned int _dec_msg_len,unsigned char * _msg_dec,unsigned char * _msg_enc)65 void fec_rep5_encode(fec _q,
66 unsigned int _dec_msg_len,
67 unsigned char *_msg_dec,
68 unsigned char *_msg_enc)
69 {
70 unsigned int i;
71 for (i=0; i<5; i++) {
72 memcpy(&_msg_enc[i*_dec_msg_len], _msg_dec, _dec_msg_len);
73 }
74 }
75
76 // decode block of data using rep5 decoder
77 //
78 // _q : encoder/decoder object
79 // _dec_msg_len : decoded message length (number of bytes)
80 // _msg_enc : encoded message [size: 1 x 5*_dec_msg_len]
81 // _msg_dec : decoded message [size: 1 x _dec_msg_len]
fec_rep5_decode(fec _q,unsigned int _dec_msg_len,unsigned char * _msg_enc,unsigned char * _msg_dec)82 void fec_rep5_decode(fec _q,
83 unsigned int _dec_msg_len,
84 unsigned char *_msg_enc,
85 unsigned char *_msg_dec)
86 {
87 unsigned char s0, s1, s2, s3, s4;
88 unsigned int i, num_errors=0;
89 for (i=0; i<_dec_msg_len; i++) {
90 s0 = _msg_enc[i ];
91 s1 = _msg_enc[i + _dec_msg_len];
92 s2 = _msg_enc[i + 2*_dec_msg_len];
93 s3 = _msg_enc[i + 3*_dec_msg_len];
94 s4 = _msg_enc[i + 4*_dec_msg_len];
95
96 // compute all triplet combinations
97 _msg_dec[i] = (s0 & s1 & s2) |
98 (s0 & s1 & s3) |
99 (s0 & s1 & s4) |
100 (s0 & s2 & s3) |
101 (s0 & s2 & s4) |
102 (s0 & s3 & s4) |
103 (s1 & s2 & s3) |
104 (s1 & s2 & s4) |
105 (s1 & s3 & s4) |
106 (s2 & s3 & s4);
107
108 //num_errors += (s0 ^ s1) | (s0 ^ s2) | (s1 ^ s2) ? 1 : 0;
109 num_errors += 0;
110 }
111 //return num_errors;
112 }
113
114 // decode block of data using rep5 decoder (soft metrics)
115 //
116 // _q : encoder/decoder object
117 // _dec_msg_len : decoded message length (number of bytes)
118 // _msg_enc : encoded message [size: 1 x 5*_dec_msg_len]
119 // _msg_dec : decoded message [size: 1 x _dec_msg_len]
fec_rep5_decode_soft(fec _q,unsigned int _dec_msg_len,unsigned char * _msg_enc,unsigned char * _msg_dec)120 void fec_rep5_decode_soft(fec _q,
121 unsigned int _dec_msg_len,
122 unsigned char * _msg_enc,
123 unsigned char * _msg_dec)
124 {
125 unsigned char s0, s1, s2, s3, s4;
126 unsigned int i;
127 unsigned int j;
128 unsigned int s_hat;
129 //unsigned int num_errors=0;
130 for (i=0; i<_dec_msg_len; i++) {
131
132 // clear decoded message
133 _msg_dec[i] = 0x00;
134
135 for (j=0; j<8; j++) {
136 s0 = _msg_enc[8*i + j];
137 s1 = _msg_enc[8*(i + _dec_msg_len) + j];
138 s2 = _msg_enc[8*(i + 2*_dec_msg_len) + j];
139 s3 = _msg_enc[8*(i + 3*_dec_msg_len) + j];
140 s4 = _msg_enc[8*(i + 4*_dec_msg_len) + j];
141
142 // average three symbols and make decision
143 s_hat = (s0 + s1 + s2 + s3 + s4)/5;
144
145 _msg_dec[i] |= (s_hat > LIQUID_SOFTBIT_ERASURE) ? (1 << (8-j-1)) : 0x00;
146
147 }
148
149 }
150 }
151