FreeCalypso > hg > freecalypso-tools
annotate miscutil/fc-tch2fr.c @ 465:003e48f8ebe1
rvinterf/etmsync/fsnew.c: cast 0 to (char *) for execl sentinel
I generally don't use NULL and use plain 0 instead, based on a "NULL
considered harmful" discussion on the classiccmp mailing list many aeons
ago (I couldn't find it, and I reason that it must have been 2005 or
earlier), but a recent complaint by a packager sent me searching, and I
found this:
https://ewontfix.com/11/
While I don't give a @#$% about "modern" systems and code-nazi tools,
I realized that passing a plain 0 as a pointer sentinel in execl is wrong
because it will break on systems where pointers are longer than the plain
int type. Again, I don't give a @#$% about the abomination of x86_64 and
the like, but if anyone ever manages to port my code to something like a
PDP-11 (16-bit int, 32-bit long and pointers), then passing a plain 0
as a function argument where a pointer is expected most definitely won't
work: if the most natural stack slot and SP alignment unit is 16 bits,
fitting an int, with longs and pointers taking up two such slots, then
the call stack will be totally wrong with a plain 0 passed for a pointer.
Casting the 0 to (char *) ought to be the most kosher solution for the
most retro systems possible.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Mon, 11 Feb 2019 00:00:19 +0000 |
parents | d57f68d0568d |
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fc-tch2fr utility written, added under miscutil
Mychaela Falconia <falcon@freecalypso.org>
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1 /* |
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fc-tch2fr utility written, added under miscutil
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2 * Our experimental Calypso firmware enables us to capture the output of |
d57f68d0568d
fc-tch2fr utility written, added under miscutil
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3 * the GSM 05.03 channel decoder in the DSP, i.e., the bits leaving the |
d57f68d0568d
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4 * channel decoder and going into the speech decoder. Our fc-shell utility |
d57f68d0568d
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5 * allows saving this capture to a file; the captured booty includes not only |
d57f68d0568d
fc-tch2fr utility written, added under miscutil
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6 * the expected 260 bits per frame, but also some DSP status words which are |
d57f68d0568d
fc-tch2fr utility written, added under miscutil
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7 * not fully understood, but which are believed to contain indications as to |
d57f68d0568d
fc-tch2fr utility written, added under miscutil
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8 * whether the decoded speech frame is good or bad. |
d57f68d0568d
fc-tch2fr utility written, added under miscutil
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9 * |
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10 * My first naive thought was to save the captured speech frames in libgsm |
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11 * format so I could then play them with the 'play' command (SoX package) |
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12 * under Linux, but the problem with this naive approach is that the bad frames |
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fc-tch2fr utility written, added under miscutil
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13 * indication is lost, and some of the saved "speech" frames will contain |
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14 * utter garbage, resulting in very unkind-on-ears noises if that file is |
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15 * then played. I don't know what the proper solution should be; I don't know |
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16 * what the commercial cellphone implementations of the GSM 06.10 speech decoder |
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17 * (buried in black box DSPs) do when they get bad frames from the channel |
d57f68d0568d
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18 * decoder. |
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19 * |
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20 * The present utility reproduces the naive behaviour of my previous |
d57f68d0568d
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21 * implementation of fc-shell's tch record command: it takes hex files written |
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22 * by the current implementation of tch record in fc-shell, DISREGARDS the |
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23 * DSP status words, and blindly converts each 260-bit frame (good or bad) |
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24 * into libgsm format. |
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25 */ |
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26 |
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27 #include <sys/types.h> |
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28 #include <ctype.h> |
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29 #include <stdio.h> |
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30 #include <stdlib.h> |
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31 |
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32 static |
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33 decode_hex_digit(ch) |
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34 { |
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35 if (isdigit(ch)) |
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36 return(ch - '0'); |
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37 else if (isupper(ch)) |
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38 return(ch - 'A' + 10); |
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39 else |
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40 return(ch - 'a' + 10); |
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41 } |
d57f68d0568d
fc-tch2fr utility written, added under miscutil
Mychaela Falconia <falcon@freecalypso.org>
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42 |
d57f68d0568d
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43 main(argc, argv) |
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44 char **argv; |
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45 { |
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46 FILE *inf, *outf; |
d57f68d0568d
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47 char linebuf[128]; |
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48 int lineno; |
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49 char *cp; |
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50 int i, j; |
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51 u_char tidsp_bytes[33], libgsm_bytes[33]; |
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52 |
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53 if (argc != 3) { |
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54 fprintf(stderr, "usage: %s infile outfile\n", argv[0]); |
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55 exit(1); |
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56 } |
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57 inf = fopen(argv[1], "r"); |
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58 if (!inf) { |
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59 perror(argv[1]); |
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60 exit(1); |
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61 } |
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62 outf = fopen(argv[2], "w"); |
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63 if (!outf) { |
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64 perror(argv[2]); |
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65 exit(1); |
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66 } |
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67 for (lineno = 1; fgets(linebuf, sizeof linebuf, inf); lineno++) { |
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68 /* skip DSP status words */ |
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69 cp = linebuf; |
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70 for (i = 0; i < 3; i++) { |
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71 for (j = 0; j < 4; j++) { |
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72 if (!isxdigit(*cp++)) { |
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73 invalid: fprintf(stderr, |
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74 "error: %s is not in the expected format\n", |
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75 argv[1]); |
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76 exit(1); |
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77 } |
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78 } |
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79 if (*cp++ != ' ') |
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80 goto invalid; |
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81 } |
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82 /* read the frame bits */ |
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83 for (i = 0; i < 33; i++) { |
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84 if (!isxdigit(cp[0]) || !isxdigit(cp[1])) |
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85 goto invalid; |
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86 tidsp_bytes[i] = (decode_hex_digit(cp[0]) << 4) | |
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87 decode_hex_digit(cp[1]); |
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88 cp += 2; |
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89 } |
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90 gsm0610_tidsp_to_libgsm(tidsp_bytes, libgsm_bytes); |
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91 fwrite(libgsm_bytes, 1, 33, outf); |
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92 } |
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93 exit(0); |
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94 } |