path: root/libgpsd_core.c

/* libgpsd_core.c -- direct access to GPSes on serial or USB devices. */
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <netdb.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/time.h>
#include "config.h"
#ifdef HAVE_SYS_FILIO_H
#include <sys/filio.h>	/* for FIONREAD on BSD systems */
#endif

#include "gpsd.h"

#define NO_MAG_VAR	-999	/* must be out of band for degrees */

int gpsd_open_dgps(char *dgpsserver)
{
    char hn[256], buf[BUFSIZ];
    char *colon, *dgpsport = "rtcm-sc104";
    int dsock;

    if ((colon = strchr(dgpsserver, ':'))) {
	dgpsport = colon+1;
	*colon = '\0';
    }
    if (!getservbyname(dgpsport, "tcp"))
	dgpsport = "2101";

    dsock = netlib_connectsock(dgpsserver, dgpsport, "tcp");
    if (dsock >= 0) {
	gethostname(hn, sizeof(hn));
	sprintf(buf, "HELO %s gpsd %s\r\nR\r\n", hn, VERSION);
	write(dsock, buf, strlen(buf));
    }
    return dsock;
}

int gpsd_switch_driver(struct gps_device_t *session, char* typename)
{
    struct gps_type_t **dp;
    for (dp = gpsd_drivers; *dp; dp++)
	if (!strcmp((*dp)->typename, typename)) {
	    gpsd_report(3, "Selecting %s driver...\n", (*dp)->typename);
	    session->device_type = *dp;
	    if (session->device_type->initializer)
		session->device_type->initializer(session);
	    return 1;
	}
    gpsd_report(1, "invalid GPS type \"%s\".\n", typename);
    return 0;
}

struct gps_device_t *gpsd_init(char *device)
/* initialize GPS polling */
{
    struct gps_device_t *session = (struct gps_device_t *)calloc(sizeof(struct gps_device_t), 1);
    if (!session)
	return NULL;

    session->gpsd_device = strdup(device);
    session->device_type = gpsd_drivers[0];
    session->dsock = -1;

    /* mark GPS fd closed */
    session->gpsdata.gps_fd = -1;

#ifdef NTPSHM_ENABLE
    ntpshm_init(session);
#endif /* defined(SHM_H) && defined(IPC_H) */

    return session;
}

void gpsd_deactivate(struct gps_device_t *session)
/* temporarily release the GPS device */
{
    gpsd_report(1, "closing GPS=%s\n", session->gpsd_device);
    gpsd_close(session);
    session->gpsdata.gps_fd = -1;
    if (session->device_type->wrapup)
	session->device_type->wrapup(session);
}

int gpsd_activate(struct gps_device_t *session)
/* acquire a connection to the GPS device */
{
    if (gpsd_open(session) < 0)
	return -1;
    else {
	session->gpsdata.online = timestamp();
	session->counter = 0;
	gpsd_report(1, "gpsd_activate: opened GPS (%d)\n", session->gpsdata.gps_fd);
	if (session->packet_type == SIRF_PACKET)
	    gpsd_switch_driver(session, "SiRF-II binary");
	else if (session->packet_type == NMEA_PACKET)
	    gpsd_switch_driver(session, "Generic NMEA");
	else if (session->device_type->initializer)
	    session->device_type->initializer(session);

	session->gpsdata.online = 0;
	session->gpsdata.fix.mode = MODE_NOT_SEEN;
	session->gpsdata.status = STATUS_NO_FIX;
	session->gpsdata.fix.track = TRACK_NOT_VALID;
#ifdef BINARY_ENABLE
	session->mag_var = NO_MAG_VAR;
	session->separation = NO_SEPARATION;
#endif /* BINARY_ENABLE */

	return session->gpsdata.gps_fd;
    }
}

static int is_input_waiting(int fd)
{
    int	count;
    if (fd < 0 || ioctl(fd, FIONREAD, &count) < 0)
	return -1;
    return count;
}

int gpsd_poll(struct gps_device_t *session)
/* update the stuff in the scoreboard structure */
{
    int waiting;

    /* accept a DGPS correction if one is pending */
    if (is_input_waiting(session->dsock) > 0) {
	char buf[BUFSIZ];
	int rtcmbytes;

	if ((rtcmbytes=read(session->dsock,buf,sizeof(buf)))>0 && (session->gpsdata.gps_fd !=-1)) {
	    if (session->device_type->rtcm_writer(session, buf, rtcmbytes) <= 0)
		gpsd_report(1, "Write to rtcm sink failed\n");
	    else
		gpsd_report(2, "<= DGPS: %d bytes of RTCM relayed.\n", rtcmbytes);
	} else
	    gpsd_report(1, "Read from rtcm source failed\n");
    }

    /* update the scoreboard structure from the GPS */
    waiting = is_input_waiting(session->gpsdata.gps_fd);
    gpsd_report(7, "GPS has %d chars waiting\n", waiting);
    if (waiting < 0)
	return 0;
    else if (!waiting) {
	if (timestamp()>session->gpsdata.online+session->device_type->cycle+1){
	    session->gpsdata.online = 0;
	    return 0;
	} else
	    return ONLINE_SET;
    } else {

	session->gpsdata.online = timestamp();

	if (!session->inbuflen || session->packet_full) {
	    session->gpsdata.d_xmit_time = timestamp();
	    session->packet_full = 0;
	}

	/* can we get a full packet from the device? */
	if (!session->device_type->get_packet(session, waiting))
	    return ONLINE_SET;

	session->packet_full = 0;
	session->gpsdata.sentence_time = 0;
	session->gpsdata.sentence_length = session->outbuflen;
	session->gpsdata.d_recv_time = timestamp();

	session->gpsdata.valid = ONLINE_SET | session->device_type->parse_packet(session);

	/* count all packets and good fixes */
	session->counter++;
	if (session->gpsdata.status > STATUS_NO_FIX) 
	    session->fixcnt++;

	/*
	 * Compute derived quantities.  This is where the tricky error-
	 * modeling stuff goes. Presently we don't know how to derive 
	 * time or track error.
	 *
	 * Field reports match the theoretical prediction that
	 * expected time error should be half the resolution of
	 * the GPS clock, so we put the bound of the error
	 * in as a constant pending getting it from each driver.
	 *
	 * Some drivers set the position-error fields.  Only the Zodiacs 
	 * report speed error.  Nobody reports track error or climb error.
	 */
	session->gpsdata.fix.ept = 0.005;
#ifdef BINARY_ENABLE
	if (session->gpsdata.valid & LATLON_SET) {
	    if (!(session->gpsdata.valid & HERR_SET) 
	    	&& (session->gpsdata.valid & HDOP_SET)) {
		session->gpsdata.fix.eph = session->gpsdata.hdop*UERE(session);
		session->gpsdata.valid |= HERR_SET;
	    }
	    if (!(session->gpsdata.valid & VERR_SET) 
	    	&& (session->gpsdata.valid & VDOP_SET)) {
		session->gpsdata.fix.epv = session->gpsdata.vdop*UERE(session);
		session->gpsdata.valid |= VERR_SET;
	    }
	    if (!(session->gpsdata.valid & PERR_SET) 
	    	&& (session->gpsdata.valid & PDOP_SET)) {
		session->gpsdata.epe = session->gpsdata.pdop*UERE(session);
		session->gpsdata.valid |= PERR_SET;
	    }
	    if (!(session->gpsdata.valid & SPEEDERR_SET)) {
		session->gpsdata.fix.eps = 0.0;
		if (session->lastfix.mode > MODE_NO_FIX 
		    && session->gpsdata.fix.mode > MODE_NO_FIX) {
		    double t = session->gpsdata.fix.time-session->lastfix.time;
		    double e = session->lastfix.eph + session->gpsdata.fix.eph;
		    session->gpsdata.fix.eps = e/t;
		    if (session->gpsdata.fix.eps)
			session->gpsdata.valid |= SPEEDERR_SET;
		}
	    }
	    if (!(session->gpsdata.valid & CLIMBERR_SET)) {
		session->gpsdata.fix.epc = 0.0;
		if (session->lastfix.mode > MODE_3D 
		    && session->gpsdata.fix.mode > MODE_3D) {
		    double t = session->gpsdata.fix.time-session->lastfix.time;
		    double e = session->lastfix.epv + session->gpsdata.fix.epv;
		    /* if vertical uncertainties are zero this will be too */
		    session->gpsdata.fix.epc = e/t;
		    if (session->gpsdata.fix.epc)
			session->gpsdata.valid |= CLIMBERR_SET;
		}
	    }

	    /* save the old fix for later uncertainty computations */
	    memcpy(&session->lastfix, 
		   &session->gpsdata.fix, 
		   sizeof(struct gps_fix_t));
	}
#endif /* BINARY_ENABLE */

	session->gpsdata.d_decode_time = timestamp();

	/* may be time to ship a DGPS correction to the GPS */
	if (session->fixcnt > 10 && !session->sentdgps) {
	    session->sentdgps++;
	    if (session->dsock > -1) {
		char buf[BUFSIZ];
		sprintf(buf, "R %0.8f %0.8f %0.2f\r\n", 
			session->gpsdata.fix.latitude, 
			session->gpsdata.fix.longitude, 
			session->gpsdata.fix.altitude);
		write(session->dsock, buf, strlen(buf));
		gpsd_report(2, "=> dgps %s", buf);
	    }
	}
	return session->gpsdata.valid;
    }
}

void gpsd_wrap(struct gps_device_t *session)
/* end-of-session wrapup */
{
    gpsd_deactivate(session);
    free(session);
}

void gpsd_zero_satellites(struct gps_data_t *out)
{
    memset(out->PRN,       '\0', sizeof(out->PRN));
    memset(out->elevation, '\0', sizeof(out->elevation));
    memset(out->azimuth,   '\0', sizeof(out->azimuth));
    memset(out->ss,        '\0', sizeof(out->ss));
    out->satellites = 0;
}

void gpsd_raw_hook(struct gps_device_t *session, char *sentence)
{
    if (session->gpsdata.raw_hook) {
	session->gpsdata.raw_hook(&session->gpsdata, sentence);
    }
}

#ifdef BINARY_ENABLE
/*
 * 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 nonzero it is a magnetic variation in degrees that should be
 * passed on., and (d) if the private member separation does not have the
 * value NO_SEPARATION, it is a valid WGS84 geoidal separation in 
 * meters for the fix.
 */

static double degtodm(double a)
{
    double m, t;
    m = modf(a, &t);
    t = floor(a) * 100 + m * 60;
    return t;
}

void gpsd_binary_fix_dump(struct gps_device_t *session, char *bufp)
{
    char hdop_str[NMEA_MAX] = "";
    struct tm tm;
    time_t intfixtime;

    if (session->gpsdata.hdop)
	sprintf(hdop_str, "%.2f", session->gpsdata.hdop);

    intfixtime = (int)session->gpsdata.fix.time;
    gmtime_r(&intfixtime, &tm);
    if (session->gpsdata.fix.mode > 1) {
	sprintf(bufp,
		"$GPGGA,%02d%02d%02d,%.4f,%c,%.4f,%c,%d,%02d,%s,%.1f,%c,",
		tm.tm_hour,
		tm.tm_min,
		tm.tm_sec,
		degtodm(fabs(session->gpsdata.fix.latitude)),
		((session->gpsdata.fix.latitude > 0) ? 'N' : 'S'),
		degtodm(fabs(session->gpsdata.fix.longitude)),
		((session->gpsdata.fix.longitude > 0) ? 'E' : 'W'),
		session->gpsdata.fix.mode,
		session->gpsdata.satellites_used,
		hdop_str,
		session->gpsdata.fix.altitude, 'M');
	if (session->separation == NO_SEPARATION)
	    strcat(bufp, ",,");
	else
	    sprintf(bufp+strlen(bufp), "%.3f,M", session->separation);
	if (session->mag_var == NO_MAG_VAR) 
	    strcat(bufp, ",,");
	else {
	    sprintf(bufp+strlen(bufp), "%3.2f,", fabs(session->mag_var));
	    strcat(bufp, (session->mag_var > 0) ? "E": "W");
	}
	nmea_add_checksum(bufp);
	gpsd_raw_hook(session, bufp);
	bufp += strlen(bufp);
    }
    sprintf(bufp,
	    "$GPRMC,%02d%02d%02d,%c,%.4f,%c,%.4f,%c,%.4f,%.3f,%02d%02d%02d,,",
	    tm.tm_hour, 
	    tm.tm_min, 
	    tm.tm_sec,
	    session->gpsdata.status ? 'A' : 'V',
	    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.fix.speed,
	    session->gpsdata.fix.track,
	    tm.tm_mday,
	    tm.tm_mon + 1,
	    tm.tm_year % 100);
	nmea_add_checksum(bufp);
	gpsd_raw_hook(session, bufp);
}

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

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

void gpsd_binary_quality_dump(struct gps_device_t *session, char *bufp)
{
    int	i, j;
    char *bufp2 = bufp;

    sprintf(bufp, "$GPGSA,%c,%d,", 'A', session->gpsdata.fix.mode);
    j = 0;
    for (i = 0; i < MAXCHANNELS; i++) {
	if (session->gpsdata.used[i]) {
	    bufp += strlen(bufp);
	    sprintf(bufp, "%02d,", session->gpsdata.PRN[i]);
	    j++;
	}
    }
    for (i = j; i < MAXCHANNELS; i++) {
	bufp += strlen(bufp);
	sprintf(bufp, ",");
    }
    bufp += strlen(bufp);
    sprintf(bufp, "%.1f,%.1f,%.1f*", 
	    session->gpsdata.pdop, 
	    session->gpsdata.hdop,
	    session->gpsdata.vdop);
    nmea_add_checksum(bufp2);
    gpsd_raw_hook(session, bufp2);
    bufp += strlen(bufp);
    if ((session->gpsdata.fix.eph || session->gpsdata.fix.epv)
	&& finite(session->gpsdata.fix.eph)
	&& finite(session->gpsdata.fix.epv)
	&& finite(session->gpsdata.epe)
    ) {
        // output PGRME
        // only if realistic
        sprintf(bufp, "$PGRME,%.2f,%.2f,%.2f",
	    session->gpsdata.fix.eph, 
	    session->gpsdata.fix.epv, 
	    session->gpsdata.epe);
        nmea_add_checksum(bufp);
	gpsd_raw_hook(session, bufp);
	session->gpsdata.seen_sentences |= PGRME;
     }
}

#endif /* BINARY_ENABLE */