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parse_aprs.c
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parse_aprs.c
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/********************************************************************
* APRX -- 2nd generation APRS-i-gate with *
* minimal requirement of esoteric facilities or *
* libraries of any kind beyond UNIX system libc. *
* *
* (c) Matti Aarnio - OH2MQK, 2007-2014 *
* *
********************************************************************/
/*
* Some parts of this code are copied from:
*
* aprsc
*
* (c) Heikki Hannikainen, OH7LZB <[email protected]>
*
* This program is licensed under the BSD license, which can be found
* in the file LICENSE.
*
*/
/*
* A simple APRS parser from aprsc. Translated from Ham::APRS::FAP
* perl module (by OH2KKU).
*
* Only needs to get lat/lng out of the packet, other features would
* be unnecessary in this application, and slow down the parser.
* ... but lets still classify the packet, output filter needs that.
*
*/
#include "aprx.h"
#include <math.h>
#define DEBUG_LOG(...) if(debug)printf(__VA_ARGS__)
/*
* Check if the given character is a valid symbol table identifier
* or an overlay character. The set is different for compressed
* and uncompressed packets - the former has the overlaid number (0-9)
* replaced with n-j.
*/
static int valid_sym_table_compressed(char c)
{
return (c == '/' || c == '\\' || (c >= 0x41 && c <= 0x5A)
|| (c >= 0x61 && c <= 0x6A)); /* [\/\\A-Za-j] */
}
static int valid_sym_table_uncompressed(char c)
{
return (c == '/' || c == '\\' || (c >= 0x41 && c <= 0x5A)
|| (c >= 0x30 && c <= 0x39)); /* [\/\\A-Z0-9] */
}
/*
* Fill the pbuf_t structure with a parsed position and
* symbol table & code. Also does range checking for lat/lng
* and pre-calculates cosf(lat) for range filters.
*/
static int pbuf_fill_pos(struct pbuf_t *pb, const float lat, const float lng, const char sym_table, const char sym_code)
{
int bad = 0;
/* symbol table and code */
pb->symbol[0] = sym_table;
pb->symbol[1] = sym_code;
pb->symbol[2] = 0;
/* Is it perhaps a weather report ? */
if (sym_code == '_' && (sym_table == '/' || sym_table == '\\'))
pb->packettype |= T_WX;
if (sym_code == '@' && (sym_table == '/' || sym_table == '\\'))
pb->packettype |= T_WX; /* Hurricane */
bad |= (lat < -89.9 && -0.0001 <= lng && lng <= 0.0001);
bad |= (lat > 89.9 && -0.0001 <= lng && lng <= 0.0001);
if (-0.0001 <= lat && lat <= 0.0001) {
bad |= ( -0.0001 <= lng && lng <= 0.0001);
bad |= ( -90.01 <= lng && lng <= -89.99);
bad |= ( 89.99 <= lng && lng <= 90.01);
}
if (bad || lat < -90.0 || lat > 90.0 || lng < -180.0 || lng > 180.0) {
if (debug)
printf("\tposition out of range: lat %.3f lng %.3f", lat, lng);
return 0; /* out of range */
}
if (debug)
printf("\tposition ok: lat %.3f lng %.3f", lat, lng);
/* Pre-calculations for A/R/F/M-filter tests */
pb->lat = filter_lat2rad(lat); /* deg-to-radians */
pb->cos_lat = cosf(pb->lat); /* used in range filters */
pb->lng = filter_lon2rad(lng); /* deg-to-radians */
pb->flags |= F_HASPOS; /* the packet has positional data */
return 1;
}
/*
* Parse symbol from destination callsign
*/
static int get_symbol_from_dstcall_twochar(const char c1, const char c2, char *sym_table, char *sym_code)
{
//hlog(LOG_DEBUG, "\ttwochar %c %c", c1, c2);
if (c1 == 'B') {
if (c2 >= 'B' && c2 <= 'P') {
*sym_table = '/';
*sym_code = c2 - 'B' + '!';
return 1;
}
return 0;
}
if (c1 == 'P') {
if (c2 >= '0' && c2 <= '9') {
*sym_table = '/';
*sym_code = c2;
return 1;
}
if (c2 >= 'A' && c2 <= 'Z') {
*sym_table = '/';
*sym_code = c2;
return 1;
}
return 0;
}
if (c1 == 'M') {
if (c2 >= 'R' && c2 <= 'X') {
*sym_table = '/';
*sym_code = c2 - 'R' + ':';
return 1;
}
return 0;
}
if (c1 == 'H') {
if (c2 >= 'S' && c2 <= 'X') {
*sym_table = '/';
*sym_code = c2 - 'S' + '[';
return 1;
}
return 0;
}
if (c1 == 'L') {
if (c2 >= 'A' && c2 <= 'Z') {
*sym_table = '/';
*sym_code = c2 - 'A' + 'a';
return 1;
}
return 0;
}
if (c1 == 'J') {
if (c2 >= '1' && c2 <= '4') {
*sym_table = '/';
*sym_code = c2 - '1' + '{';
return 1;
}
return 0;
}
if (c1 == 'O') {
if (c2 >= 'B' && c2 <= 'P') {
*sym_table = '\\';
*sym_code = c2 - 'B' + '!';
return 1;
}
return 0;
}
if (c1 == 'A') {
if (c2 >= '0' && c2 <= '9') {
*sym_table = '\\';
*sym_code = c2;
return 1;
}
if (c2 >= 'A' && c2 <= 'Z') {
*sym_table = '\\';
*sym_code = c2;
return 1;
}
return 0;
}
if (c1 == 'N') {
if (c2 >= 'R' && c2 <= 'X') {
*sym_table = '\\';
*sym_code = c2 - 'R' + ':';
return 1;
}
return 0;
}
if (c1 == 'D') {
if (c2 >= 'S' && c2 <= 'X') {
*sym_table = '\\';
*sym_code = c2 - 'S' + '[';
return 1;
}
return 0;
}
if (c1 == 'S') {
if (c2 >= 'A' && c2 <= 'Z') {
*sym_table = '\\';
*sym_code = c2 - 'A' + 'a';
return 1;
}
return 0;
}
if (c1 == 'Q') {
if (c2 >= '1' && c2 <= '4') {
*sym_table = '\\';
*sym_code = c2 - '1' + '{';
return 1;
}
return 0;
}
return 0;
}
static int get_symbol_from_dstcall(struct pbuf_t *pb, char *sym_table, char *sym_code)
{
const char *d_start;
char type;
char overlay;
int sublength;
int numberid;
/* check that the destination call exists and is of the right size for symbol */
d_start = pb->srccall_end+1;
if (pb->dstcall_end_or_ssid - d_start < 5)
return 0; /* too short */
/* length of the parsed string */
sublength = pb->dstcall_end_or_ssid - d_start - 3;
if (sublength > 3)
sublength = 3;
#ifdef DEBUG_PARSE_APRS
if (debug)
printf("\tget_symbol_from_dstcall: %.*s (%d)", (int)(pb->dstcall_end_or_ssid - d_start), d_start, sublength);
#endif
if (strncmp(d_start, "GPS", 3) != 0 && strncmp(d_start, "SPC", 3) != 0 && strncmp(d_start, "SYM", 3) != 0)
return 0;
// hlog(LOG_DEBUG, "\ttesting %c %c %c", d_start[3], d_start[4], d_start[5]);
if (!isalnum(d_start[3]) || !isalnum(d_start[4]))
return 0;
if (sublength == 3 && !isalnum(d_start[5]))
return 0;
type = d_start[3];
if (sublength == 3) {
if (type == 'C' || type == 'E') {
if (!isdigit(d_start[4]))
return 0;
if (!isdigit(d_start[5]))
return 0;
numberid = (d_start[4] - 48) * 10 + (d_start[5] - 48);
*sym_code = numberid + 32;
if (type == 'C')
*sym_table = '/';
else
*sym_table = '\\';
#ifdef DEBUG_PARSE_APRS
if (debug)
printf("\tnumeric symbol id in dstcall: %.*s: table %c code %c",
(int)(pb->dstcall_end_or_ssid - d_start - 3), d_start + 3, *sym_table, *sym_code);
#endif
return 1;
} else {
/* secondary symbol table, with overlay
* Check first that we really are in the secondary symbol table
*/
overlay = d_start[5];
if ((type == 'O' || type == 'A' || type == 'N' ||
type == 'D' || type == 'S' || type == 'Q')
&& isalnum(overlay)) {
return get_symbol_from_dstcall_twochar(d_start[3], d_start[4], sym_table, sym_code);
}
return 0;
}
} else {
// primary or secondary table, no overlay
return get_symbol_from_dstcall_twochar(d_start[3], d_start[4], sym_table, sym_code);
}
return 0;
}
/*
* Parse NMEA position packets.
*/
static int parse_aprs_nmea(struct pbuf_t *pb, const char *body, const char *body_end)
{
float lat, lng;
const char *latp, *lngp;
int i, la, lo;
char lac, loc;
char sym_table, sym_code;
if (memcmp(body,"ULT",3) == 0) {
/* Ah.. "$ULT..." - that is, Ultimeter 2000 weather instrument */
pb->packettype |= T_WX;
return 1;
}
lat = lng = 0.0;
latp = lngp = NULL;
/* NMEA sentences to understand:
$GPGGA Global Positioning System Fix Data
$GPGLL Geographic Position, Latitude/Longitude Data
$GPRMC Remommended Minimum Specific GPS/Transit Data
$GPWPT Way Point Location ?? (bug in APRS specs ?)
$GPWPL Waypoint Load (not in APRS specs, but in NMEA specs)
$PNTS Seen on APRS-IS, private sentense based on NMEA..
$xxTLL Not seen on radio network, usually $RATLL - Target positions
reported by RAdar.
*/
if (memcmp(body, "GPGGA,", 6) == 0) {
/* GPGGA,175059,3347.4969,N,11805.7319,W,2,12,1.0,6.8,M,-32.1,M,,*7D
// v=1, looks fine
// GPGGA,000000,5132.038,N,11310.221,W,1,09,0.8,940.0,M,-17.7,,
// v=1, timestamp odd, coords look fine
// GPGGA,,,,,,0,00,,,,,,,*66
// v=0, invalid
// GPGGA,121230,4518.7931,N,07322.3202,W,2,08,1.0,40.0,M,-32.4,M,,*46
// v=2, looks valid ?
// GPGGA,193115.00,3302.50182,N,11651.22581,W,1,08,01.6,00465.90,M,-32.891,M,,*5F
// $GPGGA,hhmmss.dd,xxmm.dddd,<N|S>,yyymm.dddd,<E|W>,v,
// ss,d.d,h.h,M,g.g,M,a.a,xxxx*hh<CR><LF>
*/
latp = body+6; // over the keyword
while (latp < body_end && *latp != ',')
latp++; // scan over the timestamp
if (*latp == ',')
latp++; // .. and into latitude.
lngp = latp;
while (lngp < body_end && *lngp != ',')
lngp++;
if (*lngp == ',')
lngp++;
if (*lngp != ',')
lngp++;
if (*lngp == ',')
lngp++;
/* latp, and lngp point to start of latitude and longitude substrings
// respectively.
*/
} else if (memcmp(body, "GPGLL,", 6) == 0) {
/* $GPGLL,xxmm.dddd,<N|S>,yyymm.dddd,<E|W>,hhmmss.dd,S,M*hh<CR><LF> */
latp = body+6; // over the keyword
lngp = latp;
while (lngp < body_end && *lngp != ',') // over latitude
lngp++;
if (*lngp == ',')
lngp++; // and lat designator
if (*lngp != ',')
lngp++; // and lat designator
if (*lngp == ',')
lngp++;
/* latp, and lngp point to start of latitude and longitude substrings
// respectively
*/
} else if (memcmp(body, "GPRMC,", 6) == 0) {
/* $GPRMC,hhmmss.dd,S,xxmm.dddd,<N|S>,yyymm.dddd,<E|W>,s.s,h.h,ddmmyy,d.d, <E|W>,M*hh<CR><LF>
// ,S, = Status: 'A' = Valid, 'V' = Invalid
//
// GPRMC,175050,A,4117.8935,N,10535.0871,W,0.0,324.3,100208,10.0,E,A*3B
// GPRMC,000000,V,0000.0000,0,00000.0000,0,000,000,000000,,*01/It wasn't me :)
// invalid..
// GPRMC,000043,V,4411.7761,N,07927.0448,W,0.000,0.0,290697,10.7,W*57
// GPRMC,003803,A,3347.1727,N,11812.7184,W,000.0,000.0,140208,013.7,E*67
// GPRMC,050058,A,4609.1143,N,12258.8184,W,0.000,0.0,100208,18.0,E*5B
*/
latp = body+6; // over the keyword
while (latp < body_end && *latp != ',')
latp++; // scan over the timestamp
if (*latp == ',')
latp++; // .. and into VALIDITY
if (*latp != 'A' && *latp != 'V')
return 0; // INVALID !
if (*latp != ',')
latp++;
if (*latp == ',')
latp++;
/* now it points to latitude substring */
lngp = latp;
while (lngp < body_end && *lngp != ',')
lngp++;
if (*lngp == ',')
lngp++;
if (*lngp != ',')
lngp++;
if (*lngp == ',')
lngp++;
/* latp, and lngp point to start of latitude and longitude substrings
// respectively.
*/
} else if (memcmp(body, "GPWPL,", 6) == 0) {
/* $GPWPL,4610.586,N,00607.754,E,4*70
// $GPWPL,4610.452,N,00607.759,E,5*74
*/
latp = body+6;
} else if (memcmp(body, "PNTS,1,", 7) == 0) { /* PNTS version 1 */
/* $PNTS,1,0,11,01,2002,231932,3539.687,N,13944.480,E,0,000,5,Roppongi UID RELAY,000,1*35
// $PNTS,1,0,14,01,2007,131449,3535.182,N,13941.200,E,0,0.0,6,Oota-Ku KissUIDigi,000,1*1D
// $PNTS,1,0,17,02,2008,120824,3117.165,N,13036.481,E,49,059,1,Kagoshima,000,1*71
// $PNTS,1,0,17,02,2008,120948,3504.283,N,13657.933,E,00,000.0,6,,000,1*36
//
// From Alinco EJ-41U Terminal Node Controller manual:
//
// 5-4-7 $PNTS
// This is a private-sentence based on NMEA-0183. The data contains date,
// time, latitude, longitude, moving speed, direction, altitude plus a short
// message, group codes, and icon numbers. The EJ-41U does not analyze this
// format but can re-structure it.
// The data contains the following information:
// l $PNTS Starts the $PNTS sentence
// l version
// l the registered information. [0]=normal geographical location data.
// This is the only data EJ-41U can re-structure. [s]=Initial position
// for the course setting [E]=ending position for the course setting
// [1]=the course data between initial and ending [P]=the check point
// registration [A]=check data when the automatic position transmission
// is set OFF [R]=check data when the course data or check point data is
// received.
// l dd,mm,yyyy,hhmmss: Date and time indication.
// l Latitude in DMD followed by N or S
// l Longitude in DMD followed by E or W
// l Direction: Shown with the number 360 degrees divided by 64.
// 00 stands for true north, 16 for east. Speed in Km/h
// l One of 15 characters [0] to [9], [A] to [E].
// NTSMRK command determines this character when EJ-41U is used.
// l A short message up to 20 bites. Use NTSMSG command to determine this message.
// l A group code: 3 letters with a combination of [0] to [9], [A] to [Z].
// Use NTSGRP command to determine.
// l Status: [1] for usable information, [0] for non-usable information.
// l *hh<CR><LF> the check-sum and end of PNTS sentence.
*/
if (body+55 > body_end) {
DEBUG_LOG("body too short");
return 0; /* Too short.. */
}
latp = body+7; /* Over the keyword */
/* Accept any registered information code */
if (*latp++ == ',') return 0;
if (*latp++ != ',') return 0;
/* Scan over date+time info */
while (*latp != ',' && latp <= body_end) ++latp;
if (*latp == ',') ++latp;
while (*latp != ',' && latp <= body_end) ++latp;
if (*latp == ',') ++latp;
while (*latp != ',' && latp <= body_end) ++latp;
if (*latp == ',') ++latp;
while (*latp != ',' && latp <= body_end) ++latp;
if (*latp == ',') ++latp;
/* now it points to latitude substring */
lngp = latp;
while (lngp < body_end && *lngp != ',')
lngp++;
if (*lngp == ',')
lngp++;
if (*lngp != ',')
lngp++;
if (*lngp == ',')
lngp++;
/* latp, and lngp point to start of latitude and longitude substrings
// respectively.
*/
#if 1
} else if (memcmp(body, "GPGSA,", 6) == 0 ||
memcmp(body, "GPVTG,", 6) == 0 ||
memcmp(body, "GPGSV,", 6) == 0) {
/* Recognized but ignored */
return 1;
#endif
}
if (!latp || !lngp) {
if (debug)
fprintf(stderr, "Unknown NMEA: '%.11s' %.*s", pb->data, (int)(body_end - body), body);
return 0; /* Well.. Not NMEA frame */
}
// hlog(LOG_DEBUG, "NMEA parsing: %.*s", (int)(body_end - body), body);
// hlog(LOG_DEBUG, " lat=%.10s lng=%.10s", latp, lngp);
i = sscanf(latp, "%2d%f,%c,", &la, &lat, &lac);
if (i != 3)
return 0; // parse failure
i = sscanf(lngp, "%3d%f,%c,", &lo, &lng, &loc);
if (i != 3)
return 0; // parse failure
if (lac != 'N' && lac != 'S' && lac != 'n' && lac != 's')
return 0; // bad indicator value
if (loc != 'E' && loc != 'W' && loc != 'e' && loc != 'w')
return 0; // bad indicator value
// hlog(LOG_DEBUG, " lat: %c %2d %7.4f lng: %c %2d %7.4f",
// lac, la, lat, loc, lo, lng);
lat = (float)la + lat/60.0;
lng = (float)lo + lng/60.0;
if (lac == 'S' || lac == 's')
lat = -lat;
if (loc == 'W' || loc == 'w')
lng = -lng;
pb->packettype |= T_POSITION;
// Parse symbol from destination callsign
get_symbol_from_dstcall(pb, &sym_table, &sym_code);
#ifdef DEBUG_PARSE_APRS
if (debug) {
printf("\tget_symbol_from_dstcall: %.*s => %c%c",
(int)(pb->dstcall_end_or_ssid - pb->srccall_end-1), pb->srccall_end+1, sym_table, sym_code);
}
#endif
return pbuf_fill_pos(pb, lat, lng, sym_table, sym_code);
}
static int parse_aprs_telem(struct pbuf_t *pb, const char *body, const char *body_end)
{
// float lat = 0.0, lng = 0.0;
DEBUG_LOG("parse_aprs_telem");
//pbuf_fill_pos(pb, lat, lng, 0, 0);
return 1; // okay
}
/*
* Parse a MIC-E position packet
*
* APRS PROTOCOL REFERENCE 1.0.1 Chapter 10, page 42 (52 in PDF)
*
*/
static int parse_aprs_mice(struct pbuf_t *pb, const unsigned char *body, const unsigned char *body_end)
{
float lat = 0.0, lng = 0.0;
unsigned int lat_deg = 0, lat_min = 0, lat_min_frag = 0, lng_deg = 0, lng_min = 0, lng_min_frag = 0;
const char *d_start;
char dstcall[7];
char *p;
char sym_table, sym_code;
int posambiguity = 0;
int i;
DEBUG_LOG("parse_aprs_mice: %.*s", pb->packet_len-2, pb->data);
/* check packet length */
if (body_end - body < 8)
return 0;
/* check that the destination call exists and is of the right size for mic-e */
d_start = pb->srccall_end+1;
if (pb->dstcall_end_or_ssid - d_start != 6) {
DEBUG_LOG(".. bad destcall length! ");
return 0; /* eh...? */
}
/* validate destination call:
* A-K characters are not used in the last 3 characters
* and MNO are never used
*/
if (debug)printf(" destcall='%6.6s'",d_start);
for (i = 0; i < 3; i++)
if (!((d_start[i] >= '0' && d_start[i] <= '9')
|| (d_start[i] >= 'A' && d_start[i] <= 'L')
|| (d_start[i] >= 'P' && d_start[i] <= 'Z'))) {
DEBUG_LOG(".. bad destcall characters in posits 1..3");
return 0;
}
for (i = 3; i < 6; i++)
if (!((d_start[i] >= '0' && d_start[i] <= '9')
|| (d_start[i] == 'L')
|| (d_start[i] >= 'P' && d_start[i] <= 'Z'))) {
DEBUG_LOG(".. bad destcall characters in posits 4..6");
return 0;
}
DEBUG_LOG("\tpassed dstcall format check");
/* validate information field (longitude, course, speed and
* symbol table and code are checked). Not bullet proof..
*
* 0 1 23 4 5 6 7
* /^[\x26-\x7f][\x26-\x61][\x1c-\x7f]{2}[\x1c-\x7d][\x1c-\x7f][\x21-\x7b\x7d][\/\\A-Z0-9]/
*/
if (body[0] < 0x26 || body[0] > 0x7f) {
DEBUG_LOG("..bad infofield column 1");
return 0;
}
if (body[1] < 0x26 || body[1] > 0x61) {
DEBUG_LOG("..bad infofield column 2");
return 0;
}
if (body[2] < 0x1c || body[2] > 0x7f) {
DEBUG_LOG("..bad infofield column 3");
return 0;
}
if (body[3] < 0x1c || body[3] > 0x7f) {
DEBUG_LOG("..bad infofield column 4");
return 0;
}
if (body[4] < 0x1c || body[4] > 0x7d) {
DEBUG_LOG("..bad infofield column 5");
return 0;
}
if (body[5] < 0x1c || body[5] > 0x7f) {
DEBUG_LOG("..bad infofield column 6");
return 0;
}
if ((body[6] < 0x21 || body[6] > 0x7b)
&& body[6] != 0x7d) {
DEBUG_LOG("..bad infofield column 7");
return 0;
}
if (!valid_sym_table_uncompressed(body[7])) {
DEBUG_LOG("..bad symbol table entry on column 8");
return 0;
}
DEBUG_LOG("\tpassed info format check");
/* make a local copy, we're going to modify it */
strncpy(dstcall, d_start, 6);
dstcall[6] = 0;
/* First do the destination callsign
* (latitude, message bits, N/S and W/E indicators and long. offset)
*
* Translate the characters to get the latitude
*/
//fprintf(stderr, "\tuntranslated dstcall: %s\n", dstcall);
for (p = dstcall; *p; p++) {
if (*p >= 'A' && *p <= 'J')
*p -= 'A' - '0';
else if (*p >= 'P' && *p <= 'Y')
*p -= 'P' - '0';
else if (*p == 'K' || *p == 'L' || *p == 'Z')
*p = '_';
}
//fprintf(stderr, "\ttranslated dstcall: %s\n", dstcall);
// position ambiquity is going to get ignored now,
// it's not needed in this application.
if (dstcall[5] == '_') { dstcall[5] = '5'; posambiguity = 1; }
if (dstcall[4] == '_') { dstcall[4] = '5'; posambiguity = 2; }
if (dstcall[3] == '_') { dstcall[3] = '5'; posambiguity = 3; }
if (dstcall[2] == '_') { dstcall[2] = '3'; posambiguity = 4; }
if (dstcall[1] == '_' || dstcall[0] == '_') {
DEBUG_LOG("..bad pos-ambiguity on destcall");
return 0;
} // cannot use posamb here
// convert to degrees, minutes and decimal degrees,
// and then to a float lat
if (sscanf(dstcall, "%2u%2u%2u",
&lat_deg, &lat_min, &lat_min_frag) != 3) {
DEBUG_LOG("\tsscanf failed");
return 0;
}
lat = (float)lat_deg + (float)lat_min / 60.0 + (float)lat_min_frag / 6000.0;
// check the north/south direction and correct the latitude if necessary
if (d_start[3] <= 0x4c)
lat = 0 - lat;
/* Decode the longitude, the first three bytes of the body
* after the data type indicator. First longitude degrees,
* remember the longitude offset.
*/
lng_deg = body[0] - 28;
if (d_start[4] >= 0x50)
lng_deg += 100;
if (lng_deg >= 180 && lng_deg <= 189)
lng_deg -= 80;
else if (lng_deg >= 190 && lng_deg <= 199)
lng_deg -= 190;
/* Decode the longitude minutes */
lng_min = body[1] - 28;
if (lng_min >= 60)
lng_min -= 60;
/* ... and minute decimals */
lng_min_frag = body[2] - 28;
/* apply position ambiguity to longitude */
switch (posambiguity) {
case 0:
/* use everything */
lng = (float)lng_deg + (float)lng_min / 60.0
+ (float)lng_min_frag / 6000.0;
break;
case 1:
/* ignore last number of lng_min_frag */
lng = (float)lng_deg + (float)lng_min / 60.0
+ (float)(lng_min_frag - lng_min_frag % 10 + 5) / 6000.0;
break;
case 2:
/* ignore lng_min_frag */
lng = (float)lng_deg + ((float)lng_min + 0.5) / 60.0;
break;
case 3:
/* ignore lng_min_frag and last number of lng_min */
lng = (float)lng_deg + (float)(lng_min - lng_min % 10 + 5) / 60.0;
break;
case 4:
/* minute is unused -> add 0.5 degrees to longitude */
lng = (float)lng_deg + 0.5;
break;
default:
DEBUG_LOG(".. posambiguity code BUG!");
return 0;
}
/* check the longitude E/W sign */
if (d_start[5] >= 0x50)
lng = 0 - lng;
/* save the symbol table and code */
sym_code = body[6];
sym_table = body[7];
/* ok, we're done */
/*
fprintf(stderr, "\tlat %u %u.%u (%.4f) lng %u %u.%u (%.4f)\n",
lat_deg, lat_min, lat_min_frag, lat,
lng_deg, lng_min, lng_min_frag, lng);
fprintf(stderr, "\tsym '%c' '%c'\n", sym_table, sym_code);
*/
return pbuf_fill_pos(pb, lat, lng, sym_table, sym_code);
}
/*
* Parse a compressed APRS position packet
*
* APRS PROTOCOL REFERENCE 1.0.1 Chapter 9, page 36 (46 in PDF)
*
*/
static int parse_aprs_compressed(struct pbuf_t *pb, const char *body, const char *body_end)
{
char sym_table, sym_code;
int i;
int lat1, lat2, lat3, lat4;
int lng1, lng2, lng3, lng4;
float lat, lng;
DEBUG_LOG("parse_aprs_compressed");
/* A compressed position is always 13 characters long.
* Make sure we get at least 13 characters and that they are ok.
* Also check the allowed base-91 characters at the same time.
*/
if (body_end - body < 13) {
DEBUG_LOG("\ttoo short");
return 0; /* too short. */
}
sym_table = body[0]; /* has been validated before entering this function */
sym_code = body[9];
/* base-91 check */
for (i = 1; i <= 8; i++)
if (body[i] < 0x21 || body[i] > 0x7b)
return 0;
// fprintf(stderr, "\tpassed length and format checks, sym %c%c\n", sym_table, sym_code);
/* decode */
lat1 = (body[1] - 33);
lat2 = (body[2] - 33);
lat3 = (body[3] - 33);
lat4 = (body[4] - 33);
lat1 = ((((lat1 * 91) + lat2) * 91) + lat3) * 91 + lat4;
lng1 = (body[5] - 33);
lng2 = (body[6] - 33);
lng3 = (body[7] - 33);
lng4 = (body[8] - 33);
lng1 = ((((lng1 * 91) + lng2) * 91) + lng3) * 91 + lng4;
/* calculate latitude and longitude */
lat = 90.0F - ((float)(lat1) / 380926.0F);
lng = -180.0F + ((float)(lng1) / 190463.0F);
return pbuf_fill_pos(pb, lat, lng, sym_table, sym_code);
}
/*
* Parse an uncompressed "normal" APRS packet
*
* APRS PROTOCOL REFERENCE 1.0.1 Chapter 8, page 32 (42 in PDF)
*
*/
static int parse_aprs_uncompressed(struct pbuf_t *pb, const char *body, const char *body_end)
{
char posbuf[20];
unsigned int lat_deg = 0, lat_min = 0, lat_min_frag = 0, lng_deg = 0, lng_min = 0, lng_min_frag = 0;
float lat, lng;
char lat_hemi, lng_hemi;
char sym_table, sym_code;
int issouth = 0;
int iswest = 0;
DEBUG_LOG("parse_aprs_uncompressed");
if (body_end - body < 19) {
DEBUG_LOG("\ttoo short");
return 0;
}
/* make a local copy, so we can overwrite it at will. */
memcpy(posbuf, body, 19);
posbuf[19] = 0;
// fprintf(stderr, "\tposbuf: %s\n", posbuf);
// position ambiquity is going to get ignored now,
// it's not needed in this application.
/* lat */
if (posbuf[2] == ' ') posbuf[2] = '3';
if (posbuf[3] == ' ') posbuf[3] = '5';
if (posbuf[5] == ' ') posbuf[5] = '5';
if (posbuf[6] == ' ') posbuf[6] = '5';
/* lng */
if (posbuf[12] == ' ') posbuf[12] = '3';
if (posbuf[13] == ' ') posbuf[13] = '5';
if (posbuf[15] == ' ') posbuf[15] = '5';
if (posbuf[16] == ' ') posbuf[16] = '5';
// fprintf(stderr, "\tafter filling amb: %s\n", posbuf);
/* 3210.70N/13132.15E# */
if (sscanf(posbuf, "%2u%2u.%2u%c%c%3u%2u.%2u%c%c",
&lat_deg, &lat_min, &lat_min_frag, &lat_hemi, &sym_table,
&lng_deg, &lng_min, &lng_min_frag, &lng_hemi, &sym_code) != 10) {
DEBUG_LOG("\tsscanf failed");
return 0;
}
if (!valid_sym_table_uncompressed(sym_table))
sym_table = 0;
if (lat_hemi == 'S' || lat_hemi == 's')
issouth = 1;
else if (lat_hemi != 'N' && lat_hemi != 'n')
return 0; /* neither north or south? bail out... */
if (lng_hemi == 'W' || lng_hemi == 'w')
iswest = 1;
else if (lng_hemi != 'E' && lng_hemi != 'e')
return 0; /* neither west or east? bail out ... */
if (lat_deg > 89 || lng_deg > 179)
return 0; /* too large values for lat/lng degrees */
lat = (float)lat_deg + (float)lat_min / 60.0 + (float)lat_min_frag / 6000.0;
lng = (float)lng_deg + (float)lng_min / 60.0 + (float)lng_min_frag / 6000.0;
/* Finally apply south/west indicators */
if (issouth)
lat = 0.0 - lat;
if (iswest)
lng = 0.0 - lng;
// fprintf(stderr, "\tlat %u %u.%u %c (%.3f) lng %u %u.%u %c (%.3f)\n",
// lat_deg, lat_min, lat_min_frag, (int)lat_hemi, lat,
// lng_deg, lng_min, lng_min_frag, (int)lng_hemi, lng);
// fprintf(stderr, "\tsym '%c' '%c'\n", sym_table, sym_code);
return pbuf_fill_pos(pb, lat, lng, sym_table, sym_code);
}
/*
* Parse an APRS object
*
* APRS PROTOCOL REFERENCE 1.0.1 Chapter 11, page 58 (68 in PDF)
*
*/
static int parse_aprs_object(struct pbuf_t *pb, const char *body, const char *body_end)
{
int i;
int namelen = -1;
pb->packettype |= T_OBJECT;
DEBUG_LOG("parse_aprs_object");
/* check that the object name ends with either * or _ */
if (*(body + 9) != '*' && *(body + 9) != '_') {
DEBUG_LOG("\tinvalid object kill character");
return 0;
}
/* check that the timestamp ends with one of the valid timestamp type IDs */
char tz_end = body[16];
if (tz_end != 'z' && tz_end != 'h' && tz_end != '/') {
DEBUG_LOG("\tinvalid object timestamp character: '%c'", tz_end);
return 0;
}
/* check object's name - scan for non-printable characters and the last
* non-space character
*/
for (i = 0; i < 9; i++) {
if (body[i] < 0x20 || body[i] > 0x7e) {
DEBUG_LOG("\tobject name has unprintable characters");
return 0; // non-printable
}
if (body[i] != ' ')
namelen = i;
}
if (namelen < 0) {
DEBUG_LOG("\tobject has empty name");
return 0;
}
pb->srcname = body;
pb->srcname_len = namelen+1;
DEBUG_LOG("object name: '%.*s'\n", pb->srcname_len, pb->srcname);
/* Forward the location parsing onwards */
if (valid_sym_table_compressed(body[17]))
return parse_aprs_compressed(pb, body + 17, body_end);
if (body[17] >= '0' && body[17] <= '9')
return parse_aprs_uncompressed(pb, body + 17, body_end);
DEBUG_LOG("no valid position in object");
return 0;
}
/*
* Parse an APRS item
*
* APRS PROTOCOL REFERENCE 1.0.1 Chapter 11, page 59 (69 in PDF)
*
*/
static int parse_aprs_item(struct pbuf_t *pb, const char *body, const char *body_end)
{
int i;