pseudonmea.c

/*
 * This file is Copyright (c) 2010 by the GPSD project
 * SPDX-License-Identifier: BSD-2-clause
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>

#include "gpsd.h"
#include "strfuncs.h"

/*
 * Support for generic binary drivers.  These functions dump NMEA for passing
 * to the client in raw mode.  They assume that (a) the public gps.h structure
 * members are in a valid state, (b) that the private members hours, minutes,
 * and seconds have also been filled in, (c) that if the private member
 * mag_var is not NAN it is a magnetic variation in degrees that should be
 * passed on, and (d) if the private member separation does not have the
 * value NAN, it is a valid WGS84 geoidal separation in meters for the fix.
 */

static double degtodm(double angle)
/* decimal degrees to GPS-style, degrees first followed by minutes */
{
    double fraction, integer;
    fraction = modf(angle, &integer);
    return floor(angle) * 100 + fraction * 60;
}

void gpsd_position_fix_dump(struct gps_device_t *session,
			    char bufp[], size_t len)
{
    struct tm tm;
    time_t intfixtime;

    intfixtime = (time_t) session->gpsdata.fix.time;
    (void)gmtime_r(&intfixtime, &tm);
    if (session->gpsdata.fix.mode > MODE_NO_FIX) {
	(void)snprintf(bufp, len,
		       "$GPGGA,%02d%02d%02d,%09.4f,%c,%010.4f,%c,%d,%02d,",
		       tm.tm_hour,
		       tm.tm_min,
		       tm.tm_sec,
		       degtodm(fabs(session->gpsdata.fix.latitude)),
		       ((session->gpsdata.fix.latitude > 0) ? 'N' : 'S'),
		       degtodm(fabs(session->gpsdata.fix.longitude)),
		       ((session->gpsdata.fix.longitude > 0) ? 'E' : 'W'),
		       session->gpsdata.status,
		       session->gpsdata.satellites_used);
	if (isnan(session->gpsdata.dop.hdop))
	    (void)strlcat(bufp, ",", len);
	else
	    str_appendf(bufp, len, "%.2f,", session->gpsdata.dop.hdop);
	if (isnan(session->gpsdata.fix.altitude))
	    (void)strlcat(bufp, ",", len);
	else
	    str_appendf(bufp, len, "%.2f,M,", session->gpsdata.fix.altitude);
	if (isnan(session->gpsdata.separation))
	    (void)strlcat(bufp, ",", len);
	else
	    str_appendf(bufp, len, "%.3f,M,", session->gpsdata.separation);
	if (isnan(session->mag_var))
	    (void)strlcat(bufp, ",", len);
	else {
	    str_appendf(bufp, len, "%3.2f,", fabs(session->mag_var));
	    (void)strlcat(bufp, (session->mag_var > 0) ? "E" : "W", len);
	}
	nmea_add_checksum(bufp);
    }
}


static void gpsd_transit_fix_dump(struct gps_device_t *session,
				  char bufp[], size_t len)
{
    struct tm tm;
    time_t intfixtime;

    tm.tm_mday = tm.tm_mon = tm.tm_year = tm.tm_hour = tm.tm_min = tm.tm_sec =
	0;
    if (isnan(session->gpsdata.fix.time) == 0) {
	intfixtime = (time_t) session->gpsdata.fix.time;
	(void)gmtime_r(&intfixtime, &tm);
	tm.tm_mon++;
	tm.tm_year %= 100;
    }
#define ZEROIZE(x)	(isnan(x)!=0 ? 0.0 : x)
    (void)snprintf(bufp, len,
		   "$GPRMC,%02d%02d%02d,%c,%09.4f,%c,%010.4f,%c,%.4f,%.3f,%02d%02d%02d,,",
		   tm.tm_hour,
		   tm.tm_min,
		   tm.tm_sec,
		   session->gpsdata.status ? 'A' : 'V',
		   ZEROIZE(degtodm(fabs(session->gpsdata.fix.latitude))),
		   ((session->gpsdata.fix.latitude > 0) ? 'N' : 'S'),
		   ZEROIZE(degtodm(fabs(session->gpsdata.fix.longitude))),
		   ((session->gpsdata.fix.longitude > 0) ? 'E' : 'W'),
		   ZEROIZE(session->gpsdata.fix.speed * MPS_TO_KNOTS),
		   ZEROIZE(session->gpsdata.fix.track),
		   tm.tm_mday, tm.tm_mon, tm.tm_year);
#undef ZEROIZE
    nmea_add_checksum(bufp);
}

static void gpsd_binary_satellite_dump(struct gps_device_t *session,
				       char bufp[], size_t len)
{
    int i;
    char *bufp2 = bufp;
    bufp[0] = '\0';

    for (i = 0; i < session->gpsdata.satellites_visible; i++) {
	if (i % 4 == 0) {
	    bufp2 = bufp + strlen(bufp);
	    str_appendf(bufp, len,
			    "$GPGSV,%d,%d,%02d",
			    ((session->gpsdata.satellites_visible - 1) / 4) +
			    1, (i / 4) + 1,
			    session->gpsdata.satellites_visible);
	}
	if (i < session->gpsdata.satellites_visible)
	    str_appendf(bufp, len,
			    ",%02d,%02d,%03d,%02.0f",
			    session->gpsdata.skyview[i].PRN,
			    session->gpsdata.skyview[i].elevation,
			    session->gpsdata.skyview[i].azimuth,
			    session->gpsdata.skyview[i].ss);
	if (i % 4 == 3 || i == session->gpsdata.satellites_visible - 1) {
	    nmea_add_checksum(bufp2);
	}
    }

#ifdef ZODIAC_ENABLE
    if (session->lexer.type == ZODIAC_PACKET
	&& session->driver.zodiac.Zs[0] != 0) {
	bufp2 = bufp + strlen(bufp);
	str_appendf(bufp, len, "$PRWIZCH");
	for (i = 0; i < ZODIAC_CHANNELS; i++) {
	    str_appendf(bufp, len,
			    ",%02u,%X",
			    session->driver.zodiac.Zs[i],
			    session->driver.zodiac.Zv[i] & 0x0f);
	}
	nmea_add_checksum(bufp2);
    }
#endif /* ZODIAC_ENABLE */
}

static void gpsd_binary_quality_dump(struct gps_device_t *session,
				     char bufp[], size_t len)
{
    char *bufp2;
    bufp[0] = '\0';

    if (session->device_type != NULL && (session->gpsdata.set & MODE_SET) != 0) {
	int i, j;
	int max_channels = session->device_type->channels;

	/* GPGSA commonly has exactly 12 channels, enforce that as a MAX */
	if ( 12 < max_channels ) {
	    /* what to do with the excess channels? */
	    max_channels = 12;
	}

	bufp2 = bufp + strlen(bufp);
	(void)snprintf(bufp, len,
		       "$GPGSA,%c,%d,", 'A', session->gpsdata.fix.mode);
	j = 0;
	for (i = 0; i < max_channels; i++) {
	    if (session->gpsdata.skyview[i].used == true){
		str_appendf(bufp, len, "%d,", session->gpsdata.skyview[i].PRN);
	        j++;
	    }
	}
	for (i = j; i < max_channels; i++) {
	    /* fill out the empty slots */
	    (void)strlcat(bufp, ",", len);
	}
	if (session->gpsdata.fix.mode == MODE_NO_FIX)
	    (void)strlcat(bufp, ",,,", len);
	else {
            /* output the DOPs, NaN as blanks */
	    if ( 0 == isnan( session->gpsdata.dop.pdop ) ) {
		str_appendf(bufp, len, "%.1f,", session->gpsdata.dop.pdop);
	    } else {
		(void)strlcat(bufp, ",", len);
	    }
	    if ( 0 == isnan( session->gpsdata.dop.hdop ) ) {
		str_appendf(bufp, len, "%.1f,", session->gpsdata.dop.hdop);
	    } else {
		(void)strlcat(bufp, ",", len);
	    }
	    if ( 0 == isnan( session->gpsdata.dop.vdop ) ) {
		str_appendf(bufp, len, "%.1f*", session->gpsdata.dop.vdop);
	    } else {
		(void)strlcat(bufp, "*", len);
	    }
	}
	nmea_add_checksum(bufp2);
    }
    if (isfinite(session->gpsdata.fix.epx)!=0
	&& isfinite(session->gpsdata.fix.epy)!=0
	&& isfinite(session->gpsdata.fix.epv)!=0
	&& isfinite(session->gpsdata.epe)!=0) {
	struct tm tm;
	time_t intfixtime;

	tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
	if (isnan(session->gpsdata.fix.time) == 0) {
	    intfixtime = (time_t) session->gpsdata.fix.time;
	    (void)gmtime_r(&intfixtime, &tm);
	}
	bufp2 = bufp + strlen(bufp);
#define ZEROIZE(x)      (isnan(x)!=0 ? 0.0 : x)
	str_appendf(bufp, len,
		       "$GPGBS,%02d%02d%02d,%.2f,M,%.2f,M,%.2f,M",
		       tm.tm_hour, tm.tm_min, tm.tm_sec,
		       ZEROIZE(session->gpsdata.fix.epx),
		       ZEROIZE(session->gpsdata.fix.epy),
		       ZEROIZE(session->gpsdata.fix.epv));
	nmea_add_checksum(bufp2);
    }
#undef ZEROIZE
}

static void gpsd_binary_time_dump(struct gps_device_t *session,
				     char bufp[], size_t len)
{
    struct tm tm;
    double integral;
    time_t integral_time;

    if (session->newdata.mode > MODE_NO_FIX) {
	double fractional = modf(session->newdata.time, &integral);
	integral_time = (time_t) integral;
	(void)gmtime_r(&integral_time, &tm);
	/*
	 * We pin this report to the GMT/UTC timezone.  This may be technically
	 * incorrect; our sources on ZDA suggest that it should report local
	 * timezone. But no GPS we've ever seen actually does this, because it
	 * would require embedding a location-to-TZ database in the receiver.
	 * And even if we could do that, it would make our regression tests
	 * break any time they were run in a timezone different from the one
	 * where they were generated.
	 */
	(void)snprintf(bufp, len,
		       "$GPZDA,%02d%02d%05.2f,%02d,%02d,%04d,00,00",
		       tm.tm_hour,
		       tm.tm_min,
		       (double)tm.tm_sec + fractional,
		       tm.tm_mday,
		       tm.tm_mon + 1,
		       tm.tm_year + 1900);
	nmea_add_checksum(bufp);
    }
}

static void gpsd_binary_almanac_dump(struct gps_device_t *session,
				     char bufp[], size_t len)
{
    if ( session->gpsdata.subframe.is_almanac ) {
	(void)snprintf(bufp, len,
			"$GPALM,1,1,%02d,%04d,%02x,%04x,%02x,%04x,%04x,%05x,%06x,%06x,%06x,%03x,%03x",
		       (int)session->gpsdata.subframe.sub5.almanac.sv,
		       (int)session->context->gps_week % 1024,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.svh,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.e,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.toa,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.deltai,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.Omegad,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.sqrtA,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.omega,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.Omega0,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.M0,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.af0,
		       (unsigned int)session->gpsdata.subframe.sub5.almanac.af1);
	nmea_add_checksum(bufp);
    }
}

#ifdef AIVDM_ENABLE

#define GETLEFT(a) (((a%6) == 0) ? 0 : (6 - (a%6)))

static void gpsd_binary_ais_dump(struct gps_device_t *session,
				     char bufp[], size_t len)
{
    char type[8] = "!AIVDM";
    unsigned char data[256];
    unsigned int msg1, msg2;
    char numc[4];
    char channel;
    unsigned int left;
    unsigned int datalen;
    unsigned int offset;

    channel = 'A';
    if (session->driver.aivdm.ais_channel == 'B') {
        channel = 'B';
    }

    memset(data, 0, sizeof(data));
    datalen = ais_binary_encode(&session->gpsdata.ais, &data[0], 0);
    if (datalen > 6*60) {
	static int number1 = 0;
        msg1 = datalen / (6*60);
	if ((datalen % (6*60)) != 0) {
	    msg1 += 1;
	}
	numc[0] = '0' + (char)(number1 & 0x0f);
	numc[1] = '\0';
	number1 += 1;
	if (number1 > 9) {
	    number1 = 0;
	}
	offset = 0;
	for (msg2=1;msg2<=msg1;msg2++) {
	    unsigned char old;

	    old = '\0';
	    if (strlen((char *)&data[(msg2-1)*60]) > 60) {
	        old = data[(msg2-0)*60];
	        data[(msg2-0)*60] = '\0';
	    }
	    if (datalen >= (6*60)) {
	        left = 0;
		datalen -= 6*60;
	    } else {
	        left = GETLEFT(datalen);
	    }
	    (void)snprintf(&bufp[offset], len-offset,
			   "%s,%u,%u,%s,%c,%s,%u",
			   type,
			   msg1,
			   msg2,
			   numc,
			   channel,
			   (char *)&data[(msg2-1)*60],
			   left);

	    nmea_add_checksum(&bufp[offset]);
	    if (old != (unsigned char)'\0') {
		data[(msg2-0)*60] = old;
	    }
	    offset = (unsigned int) strlen(bufp);
	}
    } else if (datalen > 0) {
        msg1 = 1;
	msg2 = 1;
	numc[0] = '\0';
        left = GETLEFT(datalen);
	(void)snprintf(bufp, len,
		       "%s,%u,%u,%s,%c,%s,%u",
		       type,
		       msg1,
		       msg2,
		       numc,
		       channel,
		       (char *)data,
		       left);

	nmea_add_checksum(bufp);
    }

    if (session->gpsdata.ais.type == 24) {
        msg1 = 1;
	msg2 = 1;
	numc[0] = '\0';

        memset(data, 0, sizeof(data));
	datalen = ais_binary_encode(&session->gpsdata.ais, &data[0], 1);
	if (datalen > 0) {
	    left = GETLEFT(datalen);
	    offset = (unsigned int)strlen(bufp);
	    (void)snprintf(&bufp[offset], len-offset,
		           "%s,%u,%u,%s,%c,%s,%u",
		           type,
		           msg1,
		           msg2,
		           numc,
		           channel,
		           (char *)data,
		           left);
	nmea_add_checksum(bufp+offset);
	}
    }
}
#endif /* AIVDM_ENABLE */

/* *INDENT-OFF* */
void nmea_tpv_dump(struct gps_device_t *session,
		   char bufp[], size_t len)
{
    bufp[0] = '\0';
    if ((session->gpsdata.set & TIME_SET) != 0)
	gpsd_binary_time_dump(session, bufp + strlen(bufp),
			      len - strlen(bufp));
    if ((session->gpsdata.set & LATLON_SET) != 0) {
	gpsd_position_fix_dump(session, bufp + strlen(bufp),
			       len - strlen(bufp));
	gpsd_transit_fix_dump(session, bufp + strlen(bufp),
			      len - strlen(bufp));
    }
    if ((session->gpsdata.set
	 & (MODE_SET | DOP_SET | USED_IS | HERR_SET | VERR_SET)) != 0)
	gpsd_binary_quality_dump(session, bufp + strlen(bufp),
				 len - strlen(bufp));
}
/* *INDENT-ON* */

void nmea_sky_dump(struct gps_device_t *session,
		   char bufp[], size_t len)
{
    bufp[0] = '\0';
    if ((session->gpsdata.set & SATELLITE_SET) != 0)
	gpsd_binary_satellite_dump(session, bufp + strlen(bufp),
				   len - strlen(bufp));
}

void nmea_subframe_dump(struct gps_device_t *session,
		   char bufp[], size_t len)
{
    bufp[0] = '\0';
    if ((session->gpsdata.set & SUBFRAME_SET) != 0)
	gpsd_binary_almanac_dump(session, bufp + strlen(bufp),
				   len - strlen(bufp));
}

#ifdef AIVDM_ENABLE
void nmea_ais_dump(struct gps_device_t *session,
		   char bufp[], size_t len)
{
    bufp[0] = '\0';
    if ((session->gpsdata.set & AIS_SET) != 0)
	gpsd_binary_ais_dump(session, bufp + strlen(bufp),
				   len - strlen(bufp));
}
#endif /* AIVDM_ENABLE */


/* pseudonmea.c ends here */