FreeCalypso > hg > fc-sim-sniff

annotate sw/sniff-dec/pps.c @ 56:966a54303d68

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simsniff-dec: factor out high-level decoding
author Mychaela Falconia <falcon@freecalypso.org>
date Wed, 04 Oct 2023 01:18:50 +0000
parents 2855330ab96f
children
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Mychaela Falconia <falcon@freecalypso.org>
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1 /*
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2 * Here we implement PPS request/response message decoding.
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3 */
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4
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5 #include <sys/types.h>
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6 #include <stdio.h>
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7 #include <stdlib.h>
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8 #include <string.h>
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9 #include <strings.h>
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10 #include "state.h"
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11
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12 extern char linebuf[];
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13 extern int lineno;
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14 extern unsigned rx_byte;
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15 extern int state;
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16
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17 #define SUBST_PPS0 0
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18 #define SUBST_PPS1 1
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19 #define SUBST_PPS2 2
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20 #define SUBST_PPS3 3
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21 #define SUBST_PCK 4
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22
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23 static char pps_start_timestamp[18];
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24 static int pps_start_line;
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25 static int substate;
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26 static u_char pps_bytes[6];
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27 static unsigned byte_count;
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28
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29 void
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30 start_pps_msg()
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31 {
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32 strcpy(pps_start_timestamp, linebuf);
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33 pps_start_line = lineno;
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34 pps_bytes[0] = rx_byte;
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35 byte_count = 1;
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36 state = STATE_PPS_MSG;
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37 substate = SUBST_PPS0;
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38 }
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39
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40 static void
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41 advance_state()
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42 {
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43 if (substate == SUBST_PPS1) {
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44 if (pps_bytes[1] & 0x10)
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45 return;
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46 substate = SUBST_PPS2;
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47 }
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48 if (substate == SUBST_PPS2) {
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49 if (pps_bytes[1] & 0x20)
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50 return;
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51 substate = SUBST_PPS3;
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52 }
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53 if (substate == SUBST_PPS3) {
54
2855330ab96f simsniff-dec: bug in PPS decoder
Mychaela Falconia <falcon@freecalypso.org>
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54 if (pps_bytes[1] & 0x40)
41
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55 return;
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56 substate = SUBST_PCK;
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57 }
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58 if (substate == SUBST_PCK)
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59 return;
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60 fprintf(stderr, "BUG in PPS decoder: bad state in advance_state()\n");
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61 abort();
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62 }
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63
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64 static void
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65 check_pck()
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66 {
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67 unsigned n, xor;
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68
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69 xor = 0;
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70 for (n = 0; n < byte_count; n++)
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71 xor ^= pps_bytes[n];
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72 printf(" PCK is %s\n", xor ? "bad!" : "correct");
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73 }
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74
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75 static void
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76 pps_finish()
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77 {
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78 unsigned n;
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79
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80 printf("%s line %d: PPS", pps_start_timestamp, pps_start_line);
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81 for (n = 0; n < byte_count; n++)
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82 printf(" %02X", pps_bytes[n]);
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83 putchar('\n');
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84 check_pck();
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85 state = STATE_READY_FOR_CMD;
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86 }
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87
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88 void
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89 pps_byte_in()
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90 {
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91 pps_bytes[byte_count++] = rx_byte;
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92 switch (substate) {
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93 case SUBST_PPS0:
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94 substate = SUBST_PPS1;
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95 advance_state();
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96 return;
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97 case SUBST_PPS1:
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98 substate = SUBST_PPS2;
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99 advance_state();
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100 return;
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101 case SUBST_PPS2:
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102 substate = SUBST_PPS3;
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103 advance_state();
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104 return;
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105 case SUBST_PPS3:
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106 substate = SUBST_PCK;
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107 return;
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108 case SUBST_PCK:
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109 pps_finish();
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110 return;
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111 default:
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112 fprintf(stderr,
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113 "BUG in PPS decoder: bad state in pps_byte_in()\n");
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114 abort();
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115 }
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116 }