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annotate libgsmhr1/sid_detect.c @ 494:aaf4dec8bee0

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libgsmhr1: implement perfect SID detection
author Mychaela Falconia <falcon@freecalypso.org>
date Mon, 17 Jun 2024 23:14:19 +0000
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494
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
Mychaela Falconia <falcon@freecalypso.org>
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1 /*
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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2 * The function in this module implements detection of perfect, error-free
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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3 * HRv1 SID frames in TS 101 318 raw packed format. If SID is detected,
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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4 * the return value is 2: the code for valid SID per GSM 06.41.
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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5 */
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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6
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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7 #include <stdint.h>
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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8 #include <string.h>
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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9 #include "tw_gsmhr.h"
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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10
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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11 int gsmhr_ts101318_is_perfect_sid(const uint8_t *payload)
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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12 {
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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13 static const uint8_t all_ff_bytes[9] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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14 0xFF, 0xFF, 0xFF, 0xFF};
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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15
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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16 if ((payload[4] & 0x7F) != 0x7F)
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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17 return 0;
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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18 if (memcmp(payload + 5, all_ff_bytes, 9) == 0)
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19 return 2;
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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20 else
aaf4dec8bee0 libgsmhr1: implement perfect SID detection
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21 return 0;
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22 }