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decode_aprs.c
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//
// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2011, 2012, 2013, 2014, 2015, 2017, 2022 John Langner, WB2OSZ
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
/*------------------------------------------------------------------
*
* File: decode_aprs.c
*
* Purpose: Decode the information part of APRS frame.
*
* Description: Present the packet contents in human readable format.
* This is a fairly complete implementation with error messages
* pointing out various specification violations.
*
* Assumptions: ax25_from_frame() has been called to
* separate the header and information.
*
*------------------------------------------------------------------*/
#include "direwolf.h"
#include <stdio.h>
#include <time.h>
#include <assert.h>
#include <stdlib.h> /* for atof */
#include <string.h> /* for strtok */
#include <math.h> /* for pow */
#include <ctype.h> /* for isdigit */
#include <fcntl.h>
#include "regex.h"
#include "ax25_pad.h"
#include "textcolor.h"
#include "symbols.h"
#include "latlong.h"
#include "dwgpsnmea.h"
#include "decode_aprs.h"
#include "telemetry.h"
#include "ais.h"
#define TRUE 1
#define FALSE 0
/* Position & symbol fields common to several message formats. */
typedef struct {
char lat[8];
char sym_table_id; /* / \ 0-9 A-Z */
char lon[9];
char symbol_code;
} position_t;
typedef struct {
char sym_table_id; /* / \ a-j A-Z */
/* "The presence of the leading Symbol Table Identifier */
/* instead of a digit indicates that this is a compressed */
/* Position Report and not a normal lat/long report." */
/* "a-j" is not a typographical error. */
/* The first 10 lower case letters represent the overlay */
/* characters of 0-9 in the compressed format. */
char y[4]; /* Compressed Latitude. */
char x[4]; /* Compressed Longitude. */
char symbol_code;
char c; /* Course/speed or altitude. */
char s;
char t ; /* Compression type. */
} compressed_position_t;
/* Range of digits for Base 91 representation. */
#define B91_MIN '!'
#define B91_MAX '{'
#define isdigit91(c) ((c) >= B91_MIN && (c) <= B91_MAX)
//static void print_decoded (decode_aprs_t *A);
static void aprs_ll_pos (decode_aprs_t *A, unsigned char *, int);
static void aprs_ll_pos_time (decode_aprs_t *A, unsigned char *, int);
static void aprs_raw_nmea (decode_aprs_t *A, unsigned char *, int);
static void aprs_mic_e (decode_aprs_t *A, packet_t, unsigned char *, int);
//static void aprs_compressed_pos (decode_aprs_t *A, unsigned char *, int);
static void aprs_message (decode_aprs_t *A, unsigned char *, int, int quiet);
static void aprs_object (decode_aprs_t *A, unsigned char *, int);
static void aprs_item (decode_aprs_t *A, unsigned char *, int);
static void aprs_station_capabilities (decode_aprs_t *A, char *, int);
static void aprs_status_report (decode_aprs_t *A, char *, int);
static void aprs_general_query (decode_aprs_t *A, char *, int, int quiet);
static void aprs_directed_station_query (decode_aprs_t *A, char *addressee, char *query, int quiet);
static void aprs_telemetry (decode_aprs_t *A, char *info, int info_len, int quiet);
static void aprs_user_defined (decode_aprs_t *A, char *, int);
static void aprs_raw_touch_tone (decode_aprs_t *A, char *, int);
static void aprs_morse_code (decode_aprs_t *A, char *, int);
static void aprs_positionless_weather_report (decode_aprs_t *A, unsigned char *, int);
static void weather_data (decode_aprs_t *A, char *wdata, int wind_prefix);
static void aprs_ultimeter (decode_aprs_t *A, char *, int);
static void decode_position (decode_aprs_t *A, position_t *ppos);
static void decode_compressed_position (decode_aprs_t *A, compressed_position_t *ppos);
static double get_latitude_8 (char *p, int quiet);
static double get_longitude_9 (char *p, int quiet);
static time_t get_timestamp (decode_aprs_t *A, char *p);
static int get_maidenhead (decode_aprs_t *A, char *p);
static int data_extension_comment (decode_aprs_t *A, char *pdext);
static void decode_tocall (decode_aprs_t *A, char *dest);
//static void get_symbol (decode_aprs_t *A, char dti, char *src, char *dest);
static void process_comment (decode_aprs_t *A, char *pstart, int clen);
/*------------------------------------------------------------------
*
* Function: decode_aprs
*
* Purpose: Split APRS packet into separate properties that it contains.
*
* Inputs: pp - APRS packet object.
*
* quiet - Suppress error messages.
*
* third_party_src - Specify when parsing a third party header.
* (decode_aprs is called recursively.)
* This is mostly found when an IGate transmits a message
* that came via APRS-IS.
* NULL when not third party payload.
*
* Outputs: A-> g_symbol_table, g_symbol_code,
* g_lat, g_lon,
* g_speed_mph, g_course, g_altitude_ft,
* g_comment
* ... and many others...
*
* Major Revisions: 1.1 Reorganized so parts are returned in a structure.
* Print function is now called separately.
*
*------------------------------------------------------------------*/
void decode_aprs (decode_aprs_t *A, packet_t pp, int quiet, char *third_party_src)
{
//dw_printf ("DEBUG decode_aprs quiet=%d, third_party=%p\n", quiet, third_party_src);
unsigned char *pinfo;
int info_len;
info_len = ax25_get_info (pp, &pinfo);
//dw_printf ("DEBUG decode_aprs info=\"%s\"\n", pinfo);
memset (A, 0, sizeof (*A));
A->g_quiet = quiet;
if (isprint(*pinfo)) {
snprintf (A->g_data_type_desc, sizeof(A->g_data_type_desc), "ERROR!!! Unknown APRS Data Type Indicator \"%c\"", *pinfo);
}
else {
snprintf (A->g_data_type_desc, sizeof(A->g_data_type_desc), "ERROR!!! Unknown APRS Data Type Indicator: unprintable 0x%02x", *pinfo);
}
A->g_symbol_table = '/'; /* Default to primary table. */
A->g_symbol_code = ' '; /* What should we have for default symbol? */
A->g_lat = G_UNKNOWN;
A->g_lon = G_UNKNOWN;
A->g_speed_mph = G_UNKNOWN;
A->g_course = G_UNKNOWN;
A->g_power = G_UNKNOWN;
A->g_height = G_UNKNOWN;
A->g_gain = G_UNKNOWN;
A->g_range = G_UNKNOWN;
A->g_altitude_ft = G_UNKNOWN;
A->g_freq = G_UNKNOWN;
A->g_tone = G_UNKNOWN;
A->g_dcs = G_UNKNOWN;
A->g_offset = G_UNKNOWN;
A->g_footprint_lat = G_UNKNOWN;
A->g_footprint_lon = G_UNKNOWN;
A->g_footprint_radius = G_UNKNOWN;
// TODO: Complain if obsolete WIDE or RELAY is found in via path.
// TODO: complain if unused WIDEn is see in path.
// There is a report of UIDIGI decrementing ssid 1 to 0 and not marking it used.
// http://lists.tapr.org/pipermail/aprssig_lists.tapr.org/2022-May/049397.html
// TODO: Complain if used digi is found after unused. Should never happen.
// If third-party header, try to decode just the payload.
if (*pinfo == '}') {
//dw_printf ("DEBUG decode_aprs recursively process third party header\n");
// This must not be strict because the addresses in third party payload doesn't
// need to adhere to the AX.25 address format (i.e. 6 upper case alphanumeric.)
// SSID can be 2 alphanumeric characters.
// Addresses can include lower case, e.g. q construct.
// e.g. WR2X-2>APRS,WA1PLE-13*:}
// K1BOS-B>APOSB,TCPIP,WR2X-2*:@122015z4221.42ND07111.93W&/A=000000SharkRF openSPOT3 MMDVM446.025 MA/SW
packet_t pp_payload = ax25_from_text ((char*)pinfo+1, 0);
if (pp_payload != NULL) {
char payload_src[AX25_MAX_ADDR_LEN];
memset(payload_src, 0, sizeof(payload_src));
memcpy(payload_src, (char*)pinfo+1, sizeof(payload_src)-1);
char *q = strchr(payload_src, '>');
if (q != NULL) *q = '\0';
decode_aprs (A, pp_payload, quiet, payload_src); // 1 means used recursively
ax25_delete (pp_payload);
return;
}
else {
strlcpy (A->g_data_type_desc, "Third Party Header: Unable to parse payload.", sizeof(A->g_data_type_desc));
ax25_get_addr_with_ssid (pp, AX25_SOURCE, A->g_src);
ax25_get_addr_with_ssid (pp, AX25_DESTINATION, A->g_dest);
}
}
/*
* Extract source and destination including the SSID.
*/
if (third_party_src != NULL) {
strlcpy (A->g_src, third_party_src, sizeof(A->g_src));
}
else {
ax25_get_addr_with_ssid (pp, AX25_SOURCE, A->g_src);
}
ax25_get_addr_with_ssid (pp, AX25_DESTINATION, A->g_dest);
//dw_printf ("DEBUG decode_aprs source=%s, dest=%s\n", A->g_src, A->g_dest);
/*
* Report error if the information part contains a nul character.
* There are two known cases where this can happen.
*
* - The Kenwood TM-D710A sometimes sends packets like this:
*
* VA3AJ-9>T2QU6X,VE3WRC,WIDE1,K8UNS,WIDE2*:4P<0x00><0x0f>4T<0x00><0x0f>4X<0x00><0x0f>4\<0x00>`nW<0x1f>oS8>/]"6M}driving fast=
* K4JH-9>S5UQ6X,WR4AGC-3*,WIDE1*:4P<0x00><0x0f>4T<0x00><0x0f>4X<0x00><0x0f>4\<0x00>`jP}l"&>/]"47}QRV from the EV =
*
* Notice that the data type indicator of "4" is not valid. If we remove
* 4P<0x00><0x0f>4T<0x00><0x0f>4X<0x00><0x0f>4\<0x00> we are left with a good MIC-E format.
* This same thing has been observed from others and is intermittent.
*
* - AGW Tracker can send UTF-16 if an option is selected. This can introduce nul bytes.
* This is wrong, it should be using UTF-8.
*/
if ( ( ! A->g_quiet ) && ( (int)strlen((char*)pinfo) != info_len) ) {
text_color_set(DW_COLOR_ERROR);
dw_printf("'nul' character found in Information part. This should never happen with APRS.\n");
dw_printf("If this is meant to be APRS, %s is transmitting with defective software.\n", A->g_src);
if (strcmp((char*)pinfo, "4P") == 0) {
dw_printf("The TM-D710 will do this intermittently. A firmware upgrade is needed to fix it.\n");
}
}
/*
* Application might be in the destination field for most message types.
* MIC-E format has part of location in the destination field.
*/
switch (*pinfo) { /* "DTI" data type identifier. */
case '\'': /* Old Mic-E Data */
case '`': /* Current Mic-E Data */
break;
default:
decode_tocall (A, A->g_dest);
break;
}
switch (*pinfo) { /* "DTI" data type identifier. */
case '!': /* Position without timestamp (no APRS messaging). */
/* or Ultimeter 2000 WX Station */
case '=': /* Position without timestamp (with APRS messaging). */
if (strncmp((char*)pinfo, "!!", 2) == 0)
{
aprs_ultimeter (A, (char*)pinfo, info_len); // TODO: produce obsolete error.
}
else
{
aprs_ll_pos (A, pinfo, info_len);
}
break;
//case '#': /* Peet Bros U-II Weather station */ // TODO: produce obsolete error.
//case '*': /* Peet Bros U-II Weather station */
//break;
case '$': /* Raw GPS data or Ultimeter 2000 */
if (strncmp((char*)pinfo, "$ULTW", 5) == 0)
{
aprs_ultimeter (A, (char*)pinfo, info_len); // TODO: produce obsolete error.
}
else
{
aprs_raw_nmea (A, pinfo, info_len);
}
break;
case '\'': /* Old Mic-E Data (but Current data for TM-D700) */
case '`': /* Current Mic-E Data (not used in TM-D700) */
aprs_mic_e (A, pp, pinfo, info_len);
break;
case ')': /* Item. */
aprs_item (A, pinfo, info_len);
break;
case '/': /* Position with timestamp (no APRS messaging) */
case '@': /* Position with timestamp (with APRS messaging) */
aprs_ll_pos_time (A, pinfo, info_len);
break;
case ':': /* "Message" (special APRS meaning): for one person, a group, or a bulletin. */
/* Directed Station Query */
/* Telemetry metadata. */
aprs_message (A, pinfo, info_len, quiet);
break;
case ';': /* Object */
aprs_object (A, pinfo, info_len);
break;
case '<': /* Station Capabilities */
aprs_station_capabilities (A, (char*)pinfo, info_len);
break;
case '>': /* Status Report */
aprs_status_report (A, (char*)pinfo, info_len);
break;
case '?': /* General Query */
aprs_general_query (A, (char*)pinfo, info_len, quiet);
break;
case 'T': /* Telemetry */
aprs_telemetry (A, (char*)pinfo, info_len, quiet);
break;
case '_': /* Positionless Weather Report */
aprs_positionless_weather_report (A, pinfo, info_len);
break;
case '{': /* user defined data */
aprs_user_defined (A, (char*)pinfo, info_len);
break;
case 't': /* Raw touch tone data - NOT PART OF STANDARD */
/* Used to convey raw touch tone sequences to */
/* to an application that might want to interpret them. */
/* Might move into user defined data, above. */
aprs_raw_touch_tone (A, (char*)pinfo, info_len);
break;
case 'm': /* Morse Code data - NOT PART OF STANDARD */
/* Used by APRStt gateway to put audible responses */
/* into the transmit queue. Could potentially find */
/* other uses such as CW ID for station. */
/* Might move into user defined data, above. */
aprs_morse_code (A, (char*)pinfo, info_len);
break;
//case '}': /* third party header */
// was already caught earlier.
//case '\r': /* CR or LF? */
//case '\n':
//break;
default:
break;
}
/*
* Priority order for determining the symbol is:
* - Information part, where appropriate. Already done above.
* - Destination field starting with GPS, SPC, or SYM.
* - Source SSID - Confusing to most people. Even I forgot about it when
* someone questioned where the symbol came from. It's in the APRS
* protocol spec, end of Chapter 20.
*/
if (A->g_symbol_table == ' ' || A->g_symbol_code == ' ') {
// A symbol on a "message" makes no sense and confuses people.
// Third party too. Set from the payload.
// Maybe eliminate for a couple others.
//dw_printf ("DEBUG decode_aprs@end1 third_party=%d, symbol_table=%c, symbol_code=%c, *pinfo=%c\n", third_party, A->g_symbol_table, A->g_symbol_code, *pinfo);
if (*pinfo != ':' && *pinfo != '}') {
symbols_from_dest_or_src (*pinfo, A->g_src, A->g_dest, &A->g_symbol_table, &A->g_symbol_code);
}
//dw_printf ("DEBUG decode_aprs@end2 third_party=%d, symbol_table=%c, symbol_code=%c, *pinfo=%c\n", third_party, A->g_symbol_table, A->g_symbol_code, *pinfo);
}
} /* end decode_aprs */
void decode_aprs_print (decode_aprs_t *A) {
char stemp[500];
double absll;
char news;
int deg;
double min;
char s_lat[30];
char s_lon[30];
int n;
/*
* First line has:
* - packet type
* - object name
* - symbol
* - manufacturer/application
* - mic-e status
* - power/height/gain, range
*/
strlcpy (stemp, A->g_data_type_desc, sizeof(stemp));
//dw_printf ("DEBUG decode_aprs_print stemp1=%s\n", stemp);
if (strlen(A->g_name) > 0) {
strlcat (stemp, ", \"", sizeof(stemp));
strlcat (stemp, A->g_name, sizeof(stemp));
strlcat (stemp, "\"", sizeof(stemp));
}
//dw_printf ("DEBUG decode_aprs_print stemp2=%s\n", stemp);
//dw_printf ("DEBUG decode_aprs_print symbol_code=%c=0x%02x\n", A->g_symbol_code, A->g_symbol_code);
if (A->g_symbol_code != ' ') {
char symbol_description[100];
symbols_get_description (A->g_symbol_table, A->g_symbol_code, symbol_description, sizeof(symbol_description));
//dw_printf ("DEBUG decode_aprs_print symbol_description_description=%s\n", symbol_description);
strlcat (stemp, ", ", sizeof(stemp));
strlcat (stemp, symbol_description, sizeof(stemp));
}
//dw_printf ("DEBUG decode_aprs_print stemp3=%s mfr=%s\n", stemp, A->g_mfr);
if (strlen(A->g_mfr) > 0) {
if (strcmp(A->g_dest, "APRS") == 0) {
strlcat (stemp, "\nUse of \"APRS\" in the destination field is obsolete.", sizeof(stemp));
strlcat (stemp, " You can help to improve the quality of APRS signals.", sizeof(stemp));
strlcat (stemp, "\nTell the sender (", sizeof(stemp));
strlcat (stemp, A->g_src, sizeof(stemp));
strlcat (stemp, ") to use the proper product code from", sizeof(stemp));
strlcat (stemp, " http://www.aprs.org/aprs11/tocalls.txt", sizeof(stemp));
}
else {
strlcat (stemp, ", ", sizeof(stemp));
strlcat (stemp, A->g_mfr, sizeof(stemp));
}
}
//dw_printf ("DEBUG decode_aprs_print stemp4=%s\n", stemp);
if (strlen(A->g_mic_e_status) > 0) {
strlcat (stemp, ", ", sizeof(stemp));
strlcat (stemp, A->g_mic_e_status, sizeof(stemp));
}
//dw_printf ("DEBUG decode_aprs_print stemp5=%s\n", stemp);
if (A->g_power > 0) {
char phg[100];
/* Protocol spec doesn't mention whether this is dBd or dBi. */
/* Clarified later. */
/* http://eng.usna.navy.mil/~bruninga/aprs/aprs11.html */
/* "The Antenna Gain in the PHG format on page 28 is in dBi." */
snprintf (phg, sizeof(phg), ", %d W height=%d %ddBi %s", A->g_power, A->g_height, A->g_gain, A->g_directivity);
strlcat (stemp, phg, sizeof(stemp));
}
if (A->g_range > 0) {
char rng[100];
snprintf (rng, sizeof(rng), ", range=%.1f", A->g_range);
strlcat (stemp, rng, sizeof(stemp));
}
if (strncmp(stemp, "ERROR", 5) == 0) {
text_color_set(DW_COLOR_ERROR);
}
else {
text_color_set(DW_COLOR_DECODED);
}
dw_printf("%s\n", stemp);
/*
* Second line has:
* - Latitude
* - Longitude
* - speed
* - direction
* - altitude
* - frequency
*/
/*
* Convert Maidenhead locator to latitude and longitude.
*
* Any example was checked for each hemihemisphere using
* http://www.amsat.org/cgi-bin/gridconv
*/
if (strlen(A->g_maidenhead) > 0) {
if (A->g_lat == G_UNKNOWN && A->g_lon == G_UNKNOWN) {
ll_from_grid_square (A->g_maidenhead, &(A->g_lat), &(A->g_lon));
}
dw_printf("Grid square = %s, ", A->g_maidenhead);
}
strlcpy (stemp, "", sizeof(stemp));
if (A->g_lat != G_UNKNOWN || A->g_lon != G_UNKNOWN) {
// Have location but it is possible one part is invalid.
if (A->g_lat != G_UNKNOWN) {
if (A->g_lat >= 0) {
absll = A->g_lat;
news = 'N';
}
else {
absll = - A->g_lat;
news = 'S';
}
deg = (int) absll;
min = (absll - deg) * 60.0;
snprintf (s_lat, sizeof(s_lat), "%c %02d%s%07.4f", news, deg, CH_DEGREE, min);
}
else {
strlcpy (s_lat, "Invalid Latitude", sizeof(s_lat));
}
if (A->g_lon != G_UNKNOWN) {
if (A->g_lon >= 0) {
absll = A->g_lon;
news = 'E';
}
else {
absll = - A->g_lon;
news = 'W';
}
deg = (int) absll;
min = (absll - deg) * 60.0;
snprintf (s_lon, sizeof(s_lon), "%c %03d%s%07.4f", news, deg, CH_DEGREE, min);
}
else {
strlcpy (s_lon, "Invalid Longitude", sizeof(s_lon));
}
snprintf (stemp, sizeof(stemp), "%s, %s", s_lat, s_lon);
}
if (strlen(A->g_aprstt_loc) > 0) {
if (strlen(stemp) > 0) strlcat (stemp, ", ", sizeof(stemp));
strlcat (stemp, A->g_aprstt_loc, sizeof(stemp));
};
if (A->g_speed_mph != G_UNKNOWN) {
char spd[32];
if (strlen(stemp) > 0) strlcat (stemp, ", ", sizeof(stemp));
snprintf (spd, sizeof(spd), "%.0f km/h (%.0f MPH)", DW_MILES_TO_KM(A->g_speed_mph), A->g_speed_mph);
strlcat (stemp, spd, sizeof(stemp));
};
if (A->g_course != G_UNKNOWN) {
char cse[20];
if (strlen(stemp) > 0) strlcat (stemp, ", ", sizeof(stemp));
snprintf (cse, sizeof(cse), "course %.0f", A->g_course);
strlcat (stemp, cse, sizeof(stemp));
};
if (A->g_altitude_ft != G_UNKNOWN) {
char alt[32];
if (strlen(stemp) > 0) strlcat (stemp, ", ", sizeof(stemp));
snprintf (alt, sizeof(alt), "alt %.0f m (%.0f ft)", DW_FEET_TO_METERS(A->g_altitude_ft), A->g_altitude_ft);
strlcat (stemp, alt, sizeof(stemp));
};
if (A->g_freq != G_UNKNOWN) {
char ftemp[30];
snprintf (ftemp, sizeof(ftemp), ", %.3f MHz", A->g_freq);
strlcat (stemp, ftemp, sizeof(stemp));
}
if (A->g_offset != G_UNKNOWN) {
char ftemp[30];
if (A->g_offset % 1000 == 0) {
snprintf (ftemp, sizeof(ftemp), ", %+dM", A->g_offset/1000);
}
else {
snprintf (ftemp, sizeof(ftemp), ", %+dk", A->g_offset);
}
strlcat (stemp, ftemp, sizeof(stemp));
}
if (A->g_tone != G_UNKNOWN) {
if (A->g_tone == 0) {
strlcat (stemp, ", no PL", sizeof(stemp));
}
else {
char ftemp[30];
snprintf (ftemp, sizeof(ftemp), ", PL %.1f", A->g_tone);
strlcat (stemp, ftemp, sizeof(stemp));
}
}
if (A->g_dcs != G_UNKNOWN) {
char ftemp[30];
snprintf (ftemp, sizeof(ftemp), ", DCS %03o", A->g_dcs);
strlcat (stemp, ftemp, sizeof(stemp));
}
if (strlen (stemp) > 0) {
text_color_set(DW_COLOR_DECODED);
dw_printf("%s\n", stemp);
}
/*
* Finally, any weather and/or comment.
*
* Non-printable characters are changed to safe hexadecimal representations.
* For example, carriage return is displayed as <0x0d>.
*
* Drop annoying trailing CR LF. Anyone who cares can see it in the raw datA->
*/
n = strlen(A->g_weather);
if (n >= 1 && A->g_weather[n-1] == '\n') {
A->g_weather[n-1] = '\0';
n--;
}
if (n >= 1 && A->g_weather[n-1] == '\r') {
A->g_weather[n-1] = '\0';
n--;
}
if (n > 0) {
ax25_safe_print (A->g_weather, -1, 0);
dw_printf("\n");
}
if (strlen(A->g_telemetry) > 0) {
ax25_safe_print (A->g_telemetry, -1, 0);
dw_printf("\n");
}
n = strlen(A->g_comment);
if (n >= 1 && A->g_comment[n-1] == '\n') {
A->g_comment[n-1] = '\0';
n--;
}
if (n >= 1 && A->g_comment[n-1] == '\r') {
A->g_comment[n-1] = '\0';
n--;
}
if (n > 0) {
int j;
ax25_safe_print (A->g_comment, -1, 0);
dw_printf("\n");
/*
* Point out incorrect attempts a degree symbol.
* 0xb0 is degree in ISO Latin1.
* To be part of a valid UTF-8 sequence, it would need to be preceded by 11xxxxxx or 10xxxxxx.
* 0xf8 is degree in Microsoft code page 437.
* To be part of a valid UTF-8 sequence, it would need to be followed by 10xxxxxx.
*/
// For values 00-7F, ASCII, Unicode, and ISO Latin-1 are all the same.
// ISO Latin-1 adds 80-FF range with a few common symbols, such as degree, and
// letters, with diacritical marks, for many European languages.
// Unicode range 80-FF is called "Latin-1 Supplement." Exactly the same as ISO Latin-1.
// For UTF-8, an additional byte is inserted.
// Unicode UTF-8
// ------- -----
// 8x C2 8x Insert C2, keep original
// 9x C2 9x "
// Ax C2 Ax "
// Bx C2 Bx "
// Cx C3 8x Insert C3, subtract 40 from original
// Dx C3 9x "
// Ex C3 Ax "
// Fx C3 Bx "
//
// Can we use this knowledge to provide guidance on other ISO Latin-1 characters besides degree?
// Should we?
// Reference: https://www.fileformat.info/info/unicode/utf8test.htm
if ( ! A->g_quiet) {
for (j=0; j<n; j++) {
if ((unsigned char)(A->g_comment[j]) == 0xb0 && (j == 0 || ! (A->g_comment[j-1] & 0x80))) {
text_color_set(DW_COLOR_ERROR);
dw_printf("Character code 0xb0 is probably an attempt at a degree symbol.\n");
dw_printf("The correct encoding is 0xc2 0xb0 in UTF-8.\n");
}
}
for (j=0; j<n; j++) {
if ((unsigned char)(A->g_comment[j]) == 0xf8 && (j == n-1 || (A->g_comment[j+1] & 0xc0) != 0xc0)) {
text_color_set(DW_COLOR_ERROR);
dw_printf("Character code 0xf8 is probably an attempt at a degree symbol.\n");
dw_printf("The correct encoding is 0xc2 0xb0 in UTF-8.\n");
}
}
}
}
}
/*------------------------------------------------------------------
*
* Function: aprs_ll_pos
*
* Purpose: Decode "Lat/Long Position Report - without Timestamp"
*
* Reports without a timestamp can be regarded as real-time.
*
* Inputs: info - Pointer to Information field.
* ilen - Information field length.
*
* Outputs: A->g_lat, A->g_lon, A->g_symbol_table, A->g_symbol_code, A->g_speed_mph, A->g_course, A->g_altitude_ft.
*
* Description: Type identifier '=' has APRS messaging.
* Type identifier '!' does not have APRS messaging.
*
* The location can be in either compressed or human-readable form.
*
* When the symbol code is '_' this is a weather report.
*
* Examples: !4309.95NS07307.13W#PHG3320 W2,NY2 Mt Equinox VT k2lm@arrl.net
* !4237.14NS07120.83W#
* =4246.40N/07115.15W# {UIV32}
*
* TODO: (?) Special case, DF report when sym table id = '/' and symbol code = '\'.
*
* =4903.50N/07201.75W\088/036/270/729
*
*------------------------------------------------------------------*/
static void aprs_ll_pos (decode_aprs_t *A, unsigned char *info, int ilen)
{
struct aprs_ll_pos_s {
char dti; /* ! or = */
position_t pos;
char comment[43]; /* Start of comment could be data extension(s). */
} *p;
struct aprs_compressed_pos_s {
char dti; /* ! or = */
compressed_position_t cpos;
char comment[40]; /* No data extension allowed for compressed location. */
} *q;
strlcpy (A->g_data_type_desc, "Position", sizeof(A->g_data_type_desc));
p = (struct aprs_ll_pos_s *)info;
q = (struct aprs_compressed_pos_s *)info;
if (isdigit((unsigned char)(p->pos.lat[0]))) /* Human-readable location. */
{
decode_position (A, &(p->pos));
if (A->g_symbol_code == '_') {
/* Symbol code indidates it is a weather report. */
/* In this case, we expect 7 byte "data extension" */
/* for the wind direction and speed. */
strlcpy (A->g_data_type_desc, "Weather Report", sizeof(A->g_data_type_desc));
weather_data (A, p->comment, TRUE);
/*
Here is an interesting case.
The protocol spec states that a position report with symbol _ is a special case
and the information part must contain wxnow.txt format weather data.
But, here we see it being generated like a normal position report.
N8VIM>BEACON,AB1OC-10*,WIDE2-1:!4240.85N/07133.99W_PHG72604/ Pepperell, MA. WX. 442.9+ PL100<0x0d>
Didn't find wind direction in form c999.
Didn't find wind speed in form s999.
Didn't find wind gust in form g999.
Didn't find temperature in form t999.
Weather Report, WEATHER Station (blue)
N 42 40.8500, W 071 33.9900
, "PHG72604/ Pepperell, MA. WX. 442.9+ PL100"
It seems, to me, that this is a violation of the protocol spec.
Then, immediately following, we have a positionless weather report in Ultimeter format.
N8VIM>APN391,AB1OC-10*,WIDE2-1:$ULTW006F00CA01421C52275800008A00000102FA000F04A6000B002A<0x0d><0x0a>
Ultimeter, Kantronics KPC-3 rom versions
wind 6.9 mph, direction 284, temperature 32.2, barometer 29.75, humidity 76
aprs.fi merges these two together. Is that anywhere in the protocol spec or
just a heuristic added after noticing a pair of packets like this?
*/
}
else {
/* Regular position report. */
data_extension_comment (A, p->comment);
}
}
else /* Compressed location. */
{
decode_compressed_position (A, &(q->cpos));
if (A->g_symbol_code == '_') {
/* Symbol code indidates it is a weather report. */
/* In this case, the wind direction and speed are in the */
/* compressed data so we don't expect a 7 byte "data */
/* extension" for them. */
strlcpy (A->g_data_type_desc, "Weather Report", sizeof(A->g_data_type_desc));
weather_data (A, q->comment, FALSE);
}
else {
/* Regular position report. */
process_comment (A, q->comment, -1);
}
}
}
/*------------------------------------------------------------------
*
* Function: aprs_ll_pos_time
*
* Purpose: Decode "Lat/Long Position Report - with Timestamp"
*
* Reports sent with a timestamp might contain very old information.
*
* Otherwise, same as above.
*
* Inputs: info - Pointer to Information field.
* ilen - Information field length.
*
* Outputs: A->g_lat, A->g_lon, A->g_symbol_table, A->g_symbol_code, A->g_speed_mph, A->g_course, A->g_altitude_ft.
*
* Description: Type identifier '@' has APRS messaging.
* Type identifier '/' does not have APRS messaging.
*
* The location can be in either compressed or human-readable form.
*
* When the symbol code is '_' this is a weather report.
*
* Examples: @041025z4232.32N/07058.81W_124/000g000t036r000p000P000b10229h65/wx rpt
* @281621z4237.55N/07120.20W_017/002g006t022r000p000P000h85b10195.Dvs
* /092345z4903.50N/07201.75W>Test1234
*
* I think the symbol code of "_" indicates weather report.
*
* (?) Special case, DF report when sym table id = '/' and symbol code = '\'.
*
* @092345z4903.50N/07201.75W\088/036/270/729
* /092345z4903.50N/07201.75W\000/000/270/729
*
*------------------------------------------------------------------*/
static void aprs_ll_pos_time (decode_aprs_t *A, unsigned char *info, int ilen)
{
struct aprs_ll_pos_time_s {
char dti; /* / or @ */
char time_stamp[7];
position_t pos;
char comment[43]; /* First 7 bytes could be data extension. */
} *p;
struct aprs_compressed_pos_time_s {
char dti; /* / or @ */
char time_stamp[7];
compressed_position_t cpos;
char comment[40]; /* No data extension in this case. */
} *q;
strlcpy (A->g_data_type_desc, "Position with time", sizeof(A->g_data_type_desc));
time_t ts = 0;
p = (struct aprs_ll_pos_time_s *)info;
q = (struct aprs_compressed_pos_time_s *)info;
if (isdigit((unsigned char)(p->pos.lat[0]))) /* Human-readable location. */
{
ts = get_timestamp (A, p->time_stamp);
decode_position (A, &(p->pos));
if (A->g_symbol_code == '_') {
/* Symbol code indidates it is a weather report. */
/* In this case, we expect 7 byte "data extension" */
/* for the wind direction and speed. */
strlcpy (A->g_data_type_desc, "Weather Report", sizeof(A->g_data_type_desc));
weather_data (A, p->comment, TRUE);
}
else {
/* Regular position report. */
data_extension_comment (A, p->comment);
}