Add ability to produce WireShark-compatible PCAP packet logging. #38
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,32 @@ | ||
| #ifndef _LORA_PKTFWD_LORA_PCAP_H | ||
| #define _LORA_PKTFWD_LORA_PCAP_H | ||
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| #define __USE_POSIX199309 1 /* Have time.h emit struct timespec */ | ||
| /* fix an issue between POSIX and C99 */ | ||
| #if __STDC_VERSION__ >= 199901L | ||
| #define _XOPEN_SOURCE 600 | ||
| #else | ||
| #define _XOPEN_SOURCE 500 | ||
| #endif | ||
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| #include <sys/time.h> | ||
| #include <time.h> | ||
| #include "loragw_hal.h" | ||
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| struct lora_pcap_session_struct; | ||
| typedef struct lora_pcap_session_struct lora_pcap_session; | ||
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| lora_pcap_session *lora_pcap_session_new(const char *path, uint64_t gw_eui); | ||
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| int lora_pcap_session_start(lora_pcap_session *ps); | ||
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| int lora_pcap_session_write(lora_pcap_session *ps, | ||
| const struct lgw_pkt_rx_s *p, const struct timespec *ts); | ||
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| int lora_pcap_session_flush(lora_pcap_session *ps); | ||
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| int lora_pcap_session_stop(lora_pcap_session *ps); | ||
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| void lora_pcap_session_free(lora_pcap_session *ps); | ||
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| #endif | ||
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| Original file line number | Diff line number | Diff line change | ||||||
|---|---|---|---|---|---|---|---|---|
| @@ -0,0 +1,355 @@ | ||||||||
| /* fix an issue between POSIX and C99 */ | ||||||||
| #if __STDC_VERSION__ >= 199901L | ||||||||
| #define _XOPEN_SOURCE 600 | ||||||||
| #else | ||||||||
| #define _XOPEN_SOURCE 500 | ||||||||
| #endif | ||||||||
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| #include <arpa/inet.h> | ||||||||
| #include <sys/types.h> | ||||||||
| #include <stdio.h> | ||||||||
| #include <stdlib.h> | ||||||||
| #include <string.h> | ||||||||
| #include <assert.h> | ||||||||
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| #include "loragw_hal.h" | ||||||||
| #include "lora_pcap.h" | ||||||||
| #include "cursor/cursor.h" | ||||||||
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| #define LINKTYPE_LORATAP 270 | ||||||||
| #define LW_SYNC 0x34 | ||||||||
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||||||||
| /* | ||||||||
| * The PCAP file header. Using clever runtime checking of the | ||||||||
| * magic number field, this structure can be written to disk | ||||||||
|
There was a problem hiding this comment. I see a write method for this struct, but no 'read'. Is that done elsewhere? Sorry if dump question, I don't know a whole lot about pcap |
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| * directly without care of the native CPU byte order. | ||||||||
| */ | ||||||||
| struct pcap_header { | ||||||||
| uint32_t magic_number; | ||||||||
| uint16_t version_major; | ||||||||
| uint16_t version_minor; | ||||||||
| int32_t this_zone; | ||||||||
| uint32_t sigfigs; | ||||||||
| uint32_t snaplen; | ||||||||
| uint32_t network; | ||||||||
| }; | ||||||||
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| struct pcap_packet_header_ns { | ||||||||
| uint32_t tm_s; | ||||||||
| uint32_t tm_ns; | ||||||||
| uint32_t packet_length; | ||||||||
| uint32_t capture_length; | ||||||||
| }; | ||||||||
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||||||||
| /* | ||||||||
| * This is the _packed_ representation of the LoRa TAP V1 | ||||||||
| * encoding scheme used by WireShark. Unfortunately, it places | ||||||||
| * wider fields at misaligned offsets, making it unsafe to fill and | ||||||||
| * then serialize this structure to disk. As such, it is unused by | ||||||||
| * this code, but provided here for reference. | ||||||||
| */ | ||||||||
| struct pcap_lora_tap_header { | ||||||||
| uint8_t lt_version; | ||||||||
| uint8_t lt_padding; | ||||||||
| uint16_t lt_length; | ||||||||
| uint32_t channel_frequency_hz; | ||||||||
| uint8_t channel_bandwidth; | ||||||||
| uint8_t channel_spreading_factor; | ||||||||
| int8_t rssi_packet; | ||||||||
| int8_t rssi_max; | ||||||||
| int8_t rssi_current; | ||||||||
| int8_t rssi_snr; | ||||||||
| uint8_t sync_word; | ||||||||
| /* Additions v1 */ | ||||||||
| uint8_t gw_eui[8]; | ||||||||
| uint32_t timestamp_1mhz; /* !MISALIGNED */ | ||||||||
| uint8_t flags; | ||||||||
| uint8_t coding_rate; | ||||||||
| uint16_t data_rate; /* !MISALIGNED */ | ||||||||
| uint8_t if_channel; | ||||||||
| uint8_t rf_chain; | ||||||||
| uint16_t tag; /* !MISALIGNED */ | ||||||||
| }; | ||||||||
| static size_t kLoRaTapHeaderSize = 35; | ||||||||
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There was a problem hiding this comment. I like that you use a literal for the size above (I dislike having to do math when reading code), but I always like to add a static assert in these situations:
Suggested change
There was a problem hiding this comment. I add the static assert suggestion from memory, so please double check syntax/usage before using if you chose to do so. |
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| struct lora_pcap_session_struct { | ||||||||
| char *path; | ||||||||
| FILE *fp; | ||||||||
| /* Cached copy of serialized gateway EUI */ | ||||||||
| uint8_t eui[8]; | ||||||||
| }; | ||||||||
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||||||||
| static int write_header(FILE *f, uint32_t caplen); | ||||||||
| static int write_rx_packet(FILE *f, const uint8_t gw_eui[8], | ||||||||
| const struct lgw_pkt_rx_s *p, const struct timespec *ts); | ||||||||
| static int8_t encode_lora_tap_rssi_dbm(float rssi_dbm); | ||||||||
| static int8_t encode_lora_tap_snr_db(float db_snr); | ||||||||
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| lora_pcap_session * | ||||||||
| lora_pcap_session_new(const char *path, uint64_t eui) | ||||||||
| { | ||||||||
| FILE *fp; | ||||||||
| char *path_copy; | ||||||||
| lora_pcap_session *ps; | ||||||||
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| if ((fp = fopen(path, "ab")) == NULL) | ||||||||
| goto OpenFailed; | ||||||||
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| if ((ps = malloc(sizeof(lora_pcap_session))) == NULL) | ||||||||
| goto MallocFailed; | ||||||||
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| if ((path_copy = strdup(path)) == NULL) | ||||||||
| goto StrDupFailed; | ||||||||
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| ps->fp = fp; | ||||||||
| ps->path = path_copy; | ||||||||
| ps->eui[0] = (eui >> 56) & 0xff; | ||||||||
| ps->eui[1] = (eui >> 48) & 0xff; | ||||||||
| ps->eui[2] = (eui >> 40) & 0xff; | ||||||||
| ps->eui[3] = (eui >> 32) & 0xff; | ||||||||
| ps->eui[4] = (eui >> 24) & 0xff; | ||||||||
| ps->eui[5] = (eui >> 16) & 0xff; | ||||||||
| ps->eui[6] = (eui >> 8) & 0xff; | ||||||||
| ps->eui[7] = (eui ) & 0xff; | ||||||||
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| return ps; | ||||||||
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| StrDupFailed: | ||||||||
| free(ps); | ||||||||
| MallocFailed: | ||||||||
| fclose(fp); | ||||||||
| OpenFailed: | ||||||||
| return NULL; | ||||||||
| } | ||||||||
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| int | ||||||||
| lora_pcap_session_start(lora_pcap_session *ps) | ||||||||
| { | ||||||||
| assert(ps->fp != NULL); | ||||||||
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||||||||
| /* | ||||||||
| * We may have opened an existing pcap file, in which case the | ||||||||
| * header will already be present and we need not write a new one. | ||||||||
| * Test for this by checking the file size. | ||||||||
| */ | ||||||||
| if (fseek(ps->fp, 0, SEEK_END) != 0) | ||||||||
| return -1; | ||||||||
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| if (ftell(ps->fp) == 0) | ||||||||
| return write_header(ps->fp, 65536); | ||||||||
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| return 0; | ||||||||
| } | ||||||||
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| int | ||||||||
| lora_pcap_session_write(lora_pcap_session *ps, | ||||||||
| const struct lgw_pkt_rx_s *p, const struct timespec *tm) | ||||||||
| { | ||||||||
| assert(ps->fp != NULL); | ||||||||
| return write_rx_packet(ps->fp, ps->eui, p, tm); | ||||||||
| } | ||||||||
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| int | ||||||||
| lora_pcap_session_flush(lora_pcap_session *ps) | ||||||||
| { | ||||||||
| assert(ps->fp != NULL); | ||||||||
| return fflush(ps->fp); | ||||||||
| } | ||||||||
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| int | ||||||||
| lora_pcap_session_stop(lora_pcap_session *ps) | ||||||||
| { | ||||||||
| assert(ps->fp != NULL); | ||||||||
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| fclose(ps->fp); | ||||||||
| ps->fp = NULL; | ||||||||
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| return 0; | ||||||||
| } | ||||||||
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| void | ||||||||
| lora_pcap_session_free(lora_pcap_session *ps) | ||||||||
| { | ||||||||
| free(ps->path); | ||||||||
| free(ps); | ||||||||
| } | ||||||||
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| static int | ||||||||
| write_header(FILE *f, uint32_t caplen) | ||||||||
| { | ||||||||
| struct pcap_header h; | ||||||||
| int num; | ||||||||
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| h.magic_number = 0xa1b23c4d; /* Nanosecond-resolution type */ | ||||||||
| h.version_major = 2; | ||||||||
| h.version_minor = 4; | ||||||||
| h.this_zone = 0; | ||||||||
| h.sigfigs = 0; | ||||||||
| h.snaplen = caplen; | ||||||||
| h.network = LINKTYPE_LORATAP; | ||||||||
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| num = fwrite(&h, sizeof(h), 1, f); | ||||||||
| fflush(f); | ||||||||
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| return (num == 1) ? 0 : -1; | ||||||||
| } | ||||||||
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| static int | ||||||||
| write_rx_packet(FILE *f, const uint8_t gw_eui[8], const struct lgw_pkt_rx_s *p, | ||||||||
| const struct timespec *ts) | ||||||||
| { | ||||||||
| struct pcap_packet_header_ns ph; | ||||||||
| uint8_t buf[kLoRaTapHeaderSize]; | ||||||||
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| if (p->modulation != MOD_LORA) | ||||||||
| /* We can only dump LoRa packets */ | ||||||||
| return 0; | ||||||||
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| /* Fill in a LoRa TAP header from the packet meta-data */ | ||||||||
| struct cursor cur = cursor_new(buf, sizeof(buf)); | ||||||||
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| cursor_pack_be_u8(&cur, 1); /* lt_version */ | ||||||||
| cursor_pack_be_u8(&cur, 0); /* lt_padding */ | ||||||||
| cursor_pack_be_u16(&cur, kLoRaTapHeaderSize); /* lt_length */ | ||||||||
| cursor_pack_be_u32(&cur, p->freq_hz); | ||||||||
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| /* | ||||||||
| * The HAL encodes bandwidth in a manner incompatible with | ||||||||
| * the PCAP link format. | ||||||||
| * pcap: bw = bandwidth / 125kHz | ||||||||
| * hal : bw = enumeration(1=500kHz, 2=250kHz, 3=125kHz, ...) | ||||||||
| */ | ||||||||
| uint8_t channel_bandwidth; | ||||||||
| switch (p->bandwidth) { | ||||||||
| case BW_125KHZ: channel_bandwidth = 1; break; | ||||||||
| case BW_250KHZ: channel_bandwidth = 2; break; | ||||||||
| case BW_500KHZ: channel_bandwidth = 4; break; | ||||||||
| default: channel_bandwidth = 0; break; | ||||||||
| } | ||||||||
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| cursor_pack_be_u8(&cur, channel_bandwidth); | ||||||||
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| /* | ||||||||
| * The HAL and the PCAP format agree exactly (currently) on | ||||||||
| * the encoding of channel spreading factors. On a good compiler | ||||||||
| * this switch statement should be a no-op. Nonetheless, good | ||||||||
| * coding practice dictates an explicit translation. | ||||||||
| */ | ||||||||
| uint8_t channel_spreading_factor; | ||||||||
| switch (p->datarate) { | ||||||||
| case DR_LORA_SF7: channel_spreading_factor = 7; break; | ||||||||
| case DR_LORA_SF8: channel_spreading_factor = 8; break; | ||||||||
| case DR_LORA_SF9: channel_spreading_factor = 9; break; | ||||||||
| case DR_LORA_SF10: channel_spreading_factor = 10; break; | ||||||||
| case DR_LORA_SF11: channel_spreading_factor = 11; break; | ||||||||
| case DR_LORA_SF12: channel_spreading_factor = 12; break; | ||||||||
| default: channel_spreading_factor = 0; break; | ||||||||
| } | ||||||||
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| cursor_pack_be_u8(&cur, channel_spreading_factor); | ||||||||
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| /* This is an SX1302 radio. It only reports two RSSI values. */ | ||||||||
| const int8_t rssic_tap_encoded = encode_lora_tap_rssi_dbm(p->rssic); | ||||||||
| const int8_t rssis_tap_encoded = encode_lora_tap_rssi_dbm(p->rssis); | ||||||||
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| cursor_pack_be_i8(&cur, rssis_tap_encoded); /* rssi_packet */ | ||||||||
| cursor_pack_be_i8(&cur, rssic_tap_encoded); /* rssi_max */ | ||||||||
| cursor_pack_be_i8(&cur, rssic_tap_encoded); /* rssi_current */ | ||||||||
| cursor_pack_be_i8(&cur, encode_lora_tap_snr_db(p->snr)); /* rssi_snr */ | ||||||||
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| cursor_pack_be_u8(&cur, LW_SYNC); /* sync_word */ | ||||||||
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| /* V1 additions */ | ||||||||
| cursor_put(&cur, gw_eui, 8); | ||||||||
| cursor_pack_be_u32(&cur, p->count_us); /* timestamp_1mhz */ | ||||||||
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||||||||
| /* | ||||||||
| * LoRa TAP V1 flags: | ||||||||
| * | ||||||||
| * 00000001 = FSK modulation (not implemented yet) | ||||||||
| * 00000010 = Symbol I/Q is inverted (not implemented yet) | ||||||||
| * 00000100 = Implicit header (not implemented yet) | ||||||||
| * 00001000 = CRC OK | ||||||||
| * 00010000 = CRC Bad | ||||||||
| * 00100000 = CRC Not Present | ||||||||
| */ | ||||||||
| uint8_t flags = 0; | ||||||||
| switch (p->status) { | ||||||||
| case STAT_NO_CRC: flags |= 0x20; break; | ||||||||
| case STAT_CRC_BAD: flags |= 0x10; break; | ||||||||
| case STAT_CRC_OK: flags |= 0x80; break; | ||||||||
| } | ||||||||
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| cursor_pack_be_u8(&cur, flags); /* coding_rate */ | ||||||||
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| uint8_t coding_rate; | ||||||||
| switch (p->coderate) { | ||||||||
| case CR_LORA_4_5: coding_rate = 5; break; | ||||||||
| case CR_LORA_4_6: coding_rate = 6; break; | ||||||||
| case CR_LORA_4_7: coding_rate = 7; break; | ||||||||
| case CR_LORA_4_8: coding_rate = 8; break; | ||||||||
| default: coding_rate = 0; break; | ||||||||
| } | ||||||||
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| cursor_pack_be_u8(&cur, coding_rate); /* coding_rate */ | ||||||||
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| /* This next field, data_rate, is redundant. Skip computing it */ | ||||||||
| cursor_pack_be_u16(&cur, 0); /* data_rate (bits/sec) */ | ||||||||
| cursor_pack_be_u8(&cur, p->if_chain); /* if_channel */ | ||||||||
| cursor_pack_be_u8(&cur, p->rf_chain); /* rf_chain */ | ||||||||
| cursor_pack_be_u16(&cur, 0); /* "tag". Unknown use */ | ||||||||
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| assert(cursor_remaining(&cur) == 0); | ||||||||
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| ph.tm_s = ts->tv_sec; | ||||||||
| ph.tm_ns = ts->tv_nsec; | ||||||||
| /* | ||||||||
| * The maximum LoRa packet size is 256 bytes in this library, so all | ||||||||
| * packets fit, all the time. | ||||||||
| */ | ||||||||
| ph.capture_length = sizeof(buf) + p->size; | ||||||||
| ph.packet_length = ph.capture_length; | ||||||||
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||||||||
| int res1 = fwrite(&ph, sizeof(ph), 1, f) == 1; | ||||||||
| int res2 = fwrite(buf, sizeof(buf), 1, f) == 1; | ||||||||
| int res3 = fwrite(p->payload, p->size, 1, f) == 1; | ||||||||
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||||||||
| return (res1 && res2 && res3) ? 0 : -1; | ||||||||
| } | ||||||||
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| static int8_t | ||||||||
| encode_lora_tap_rssi_dbm(float rssi_dbm) | ||||||||
| { | ||||||||
| float rval = rssi_dbm + 139; | ||||||||
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| if (rval > 127.0) | ||||||||
| return 127; | ||||||||
| if (rval < -128.0) | ||||||||
| return -128; | ||||||||
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||||||||
| return (int8_t) rval; | ||||||||
| } | ||||||||
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||||||||
| /* | ||||||||
| * Encode an SNR value (in dB) in a fixed-point, signed 8-bit format. | ||||||||
| * | ||||||||
| * This function encodes the SNR according to the specification. Earlier | ||||||||
| * versions of WireShark, however, have a decoder bug, as such, the SNR | ||||||||
| * will not be displayed properly there. Later versions fix it. | ||||||||
| * (Example buggy version: 2021-03-26) | ||||||||
| */ | ||||||||
| static int8_t | ||||||||
| encode_lora_tap_snr_db(float db_snr) | ||||||||
| { | ||||||||
| if (db_snr == 0.0) | ||||||||
| return 0; | ||||||||
| if (db_snr < 0) { | ||||||||
| float rval = db_snr * 4.0; | ||||||||
| if (rval < -128.0) | ||||||||
| return -128; | ||||||||
| return (int8_t) rval; | ||||||||
| } | ||||||||
| if (db_snr > 127.0) | ||||||||
| return 127; | ||||||||
| return (int8_t) db_snr; | ||||||||
| } | ||||||||
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This pattern is something I've accepted in C source, but never understood. Or at least can't remember