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comparison hr-sid/sidgen.c @ 45:5c82f2e56d56

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hr-sid: hack created
author Mychaela Falconia <falcon@freecalypso.org>
date Sun, 09 Jun 2024 08:57:28 +0000
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44:0b1c4960e5e9 45:5c82f2e56d56
1 /*
2 * This program generates a sequence of GSM-HR codec frames in raw packed
3 * format (aka TS 101 318) that aims to reverse-engineer the logic of
4 * the SID detector in TI Calypso DSP, and maybe later in historical
5 * E1 BTS implementations too.
6 */
7
8 #include <stdio.h>
9 #include <stdint.h>
10 #include <stdlib.h>
11 #include <string.h>
12 #include <strings.h>
13
14 static const uint8_t perfect_sid[14] = {
15 0x11, 0x22, 0x33, 0x44, 0xFF, 0xFF, 0xFF,
16 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
17 };
18
19 static void
20 clear_bit(buf, num)
21 uint8_t *buf;
22 unsigned num;
23 {
24 unsigned nbyte = num / 8;
25 unsigned nbit = num % 8;
26 unsigned mask = 0x80 >> nbit;
27
28 buf[nbyte] &= ~mask;
29 }
30
31 static void
32 corrupt_class1_bit(buf, num)
33 uint8_t *buf;
34 unsigned num;
35 {
36 clear_bit(buf, num + 36);
37 }
38
39 static void
40 corrupt_class2_bit(buf, num)
41 uint8_t *buf;
42 unsigned num;
43 {
44 if (num < 8)
45 clear_bit(buf, num + 81);
46 else
47 clear_bit(buf, (num - 8) + 98);
48 }
49
50 main(argc, argv)
51 char **argv;
52 {
53 FILE *outf;
54 uint8_t class1[14], class2[14];
55 unsigned n1, n2;
56
57 if (argc != 2) {
58 fprintf(stderr, "usage: %s outfile\n", argv[0]);
59 exit(1);
60 }
61 outf = fopen(argv[1], "w");
62 if (!outf) {
63 perror(argv[1]);
64 exit(1);
65 }
66 bcopy(perfect_sid, class1, 14);
67 for (n1 = 0; n1 < 20; n1++) {
68 bcopy(class1, class2, 14);
69 for (n2 = 0; n2 < 17; n2++) {
70 fwrite(class2, 1, 14, outf);
71 corrupt_class2_bit(class2, n2);
72 }
73 fwrite(class2, 1, 14, outf);
74 corrupt_class1_bit(class1, n1);
75 }
76 fclose(outf);
77 exit(0);
78 }