path: root/gpsutils.c

/* gpsutils.c -- code shared between low-level and high-level interfaces
 *
 * This file is Copyright (c) 2010 by the GPSD project
 * BSD terms apply: see the file COPYING in the distribution root for details.
 */
#include <stdio.h>
#include <time.h>
#include <stdlib.h>
#include <math.h>

#include "gpsd.h"

#ifdef USE_QT
#include <QDateTime>
#include <QStringList>
#endif

#define MONTHSPERYEAR	12	/* months per calendar year */

void gps_clear_fix( /*@out@*/ struct gps_fix_t *fixp)
/* stuff a fix structure with recognizable out-of-band values */
{
    fixp->time = NAN;
    fixp->mode = MODE_NOT_SEEN;
    fixp->latitude = fixp->longitude = NAN;
    fixp->track = NAN;
    fixp->speed = NAN;
    fixp->climb = NAN;
    fixp->altitude = NAN;
    fixp->ept = NAN;
    fixp->epx = NAN;
    fixp->epy = NAN;
    fixp->epv = NAN;
    fixp->epd = NAN;
    fixp->eps = NAN;
    fixp->epc = NAN;
}

void gps_merge_fix( /*@ out @*/ struct gps_fix_t *to,
		   gps_mask_t transfer,
		   /*@ in @*/ struct gps_fix_t *from)
/* merge new data into an old fix */
{
    if ((NULL == to) || (NULL == from))
	return;
    if ((transfer & TIME_IS) != 0)
	to->time = from->time;
    if ((transfer & LATLON_IS) != 0) {
	to->latitude = from->latitude;
	to->longitude = from->longitude;
    }
    if ((transfer & MODE_IS) != 0)
	to->mode = from->mode;
    if ((transfer & ALTITUDE_IS) != 0)
	to->altitude = from->altitude;
    if ((transfer & TRACK_IS) != 0)
	to->track = from->track;
    if ((transfer & SPEED_IS) != 0)
	to->speed = from->speed;
    if ((transfer & CLIMB_IS) != 0)
	to->climb = from->climb;
    if ((transfer & TIMERR_IS) != 0)
	to->ept = from->ept;
    if ((transfer & HERR_IS) != 0) {
	to->epx = from->epx;
	to->epy = from->epy;
    }
    if ((transfer & VERR_IS) != 0)
	to->epv = from->epv;
    if ((transfer & SPEEDERR_IS) != 0)
	to->eps = from->eps;
}

double timestamp(void)
{
    struct timeval tv;
    (void)gettimeofday(&tv, NULL);
    /*@i1@*/ return (tv.tv_sec + tv.tv_usec * 1e-6);
}

time_t mkgmtime(register struct tm * t)
/* struct tm to seconds since Unix epoch */
{
    register int year;
    register time_t result;
    static const int cumdays[MONTHSPERYEAR] =
	{ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334 };

    /*@ +matchanyintegral @*/
    year = 1900 + t->tm_year + t->tm_mon / MONTHSPERYEAR;
    result = (year - 1970) * 365 + cumdays[t->tm_mon % MONTHSPERYEAR];
    result += (year - 1968) / 4;
    result -= (year - 1900) / 100;
    result += (year - 1600) / 400;
    if ((year % 4) == 0 && ((year % 100) != 0 || (year % 400) == 0) &&
	(t->tm_mon % MONTHSPERYEAR) < 2)
	result--;
    result += t->tm_mday - 1;
    result *= 24;
    result += t->tm_hour;
    result *= 60;
    result += t->tm_min;
    result *= 60;
    result += t->tm_sec;
    /*@ -matchanyintegral @*/
    return (result);
}

double iso8601_to_unix( /*@in@*/ char *isotime)
/* ISO8601 UTC to Unix UTC */
{
#ifndef USE_QT
    char *dp = NULL;
    double usec;
    struct tm tm;

    /*@i1@*/ dp = strptime(isotime, "%Y-%m-%dT%H:%M:%S", &tm);
    if (dp != NULL && *dp == '.')
	usec = strtod(dp, NULL);
    else
	usec = 0;
    return (double)mkgmtime(&tm) + usec;
#else
    double usec = 0;

    QString t(isotime);
    QDateTime d = QDateTime::fromString(isotime, Qt::ISODate);
    QStringList sl = t.split(".");
    if (sl.size() > 1)
	usec = sl[1].toInt() / pow(10., (double)sl[1].size());
    return d.toTime_t() + usec;
#endif
}

/* *INDENT-OFF* */
/*@observer@*/char *unix_to_iso8601(double fixtime, /*@ out @*/
				     char isotime[], size_t len)
/* Unix UTC time to ISO8601, no timezone adjustment */
/* example: 2007-12-11T23:38:51.0Z */
{
    struct tm when;
    double integral, fractional;
    time_t intfixtime;
    char timestr[30];
    char fractstr[10];

    fractional = modf(fixtime, &integral);
    intfixtime = (time_t) integral;
    (void)gmtime_r(&intfixtime, &when);

    (void)strftime(timestr, sizeof(timestr), "%Y-%m-%dT%H:%M:%S", &when);
    (void)snprintf(fractstr, sizeof(fractstr), "%.1f", fractional);
    /* add fractional part, ignore leading 0; "0.2" -> ".2" */
    (void)snprintf(isotime, len, "%s%sZ", timestr, fractstr + 1);
    return isotime;
}
/* *INDENT-ON* */

/*
 * The 'week' part of GPS dates are specified in weeks since 0000 on 06
 * January 1980, with a rollover at 1024.  At time of writing the last
 * rollover happened at 0000 22 August 1999.  Time-of-week is in seconds.
 *
 * This code copes with both conventional GPS weeks and the "extended"
 * 15-or-16-bit version with no wraparound that appears in Zodiac
 * chips and is supposed to appear in the Geodetic Navigation
 * Information (0x29) packet of SiRF chips.  Some SiRF firmware versions
 * (notably 231) actually ship the wrapped 10-bit week, despite what
 * the protocol reference claims.
 *
 * Note: This time will need to be corrected for leap seconds.
 */
#define SECS_PER_WEEK	(60*60*24*7)	/* seconds per week */
#define GPS_ROLLOVER	(1024*SECS_PER_WEEK)	/* rollover period */

double gpstime_to_unix(int week, double tow)
{
    double fixtime;

    if (week >= 1024)
	fixtime = GPS_EPOCH + (week * SECS_PER_WEEK) + tow;
    else {
	time_t now, last_rollover;
	(void)time(&now);
	last_rollover =
	    GPS_EPOCH + ((now - GPS_EPOCH) / GPS_ROLLOVER) * GPS_ROLLOVER;
	/*@i@*/ fixtime = last_rollover + (week * SECS_PER_WEEK) + tow;
    }
    return fixtime;
}

void unix_to_gpstime(double unixtime,
		     /*@out@*/ int *week,
		     /*@out@*/ double *tow)
{
    unixtime -= GPS_EPOCH;
    *week = (int)(unixtime / SECS_PER_WEEK);
    *tow = fmod(unixtime, SECS_PER_WEEK);
}

#define Deg2Rad(n)	((n) * DEG_2_RAD)

/* Distance in meters between two points specified in degrees, optionally
with initial and final bearings. */
/*@-mustdefine@*/
double earth_distance_and_bearings(double lat1, double lon1, double lat2, double lon2, double *ib, double *fb)
{
    /*
     * this is a translation of the javascript implementation of the
     * Vincenty distance formula by Chris Veness. See
     * http://www.movable-type.co.uk/scripts/latlong-vincenty.html
     */
    double a, b, f;		// WGS-84 ellipsoid params
    double L, L_P, U1, U2, s_U1, c_U1, s_U2, c_U2;
    double uSq, A, B, d_S, lambda;
    double s_L, c_L, s_S, C;
    double c_S, S, s_A, c_SqA, c_2SM;
    int i = 100;

    a = WGS84A;
    b = WGS84B;
    f = 1 / WGS84F;
    L = Deg2Rad(lon2 - lon1);
    U1 = atan((1 - f) * tan(Deg2Rad(lat1)));
    U2 = atan((1 - f) * tan(Deg2Rad(lat2)));
    s_U1 = sin(U1);
    c_U1 = cos(U1);
    s_U2 = sin(U2);
    c_U2 = cos(U2);
    lambda = L;

    do {
	s_L = sin(lambda);
	c_L = cos(lambda);
	s_S = sqrt((c_U2 * s_L) * (c_U2 * s_L) +
		   (c_U1 * s_U2 - s_U1 * c_U2 * c_L) *
		   (c_U1 * s_U2 - s_U1 * c_U2 * c_L));

	if (s_S == 0)
	    return 0;

	c_S = s_U1 * s_U2 + c_U1 * c_U2 * c_L;
	S = atan2(s_S, c_S);
	s_A = c_U1 * c_U2 * s_L / s_S;
	c_SqA = 1 - s_A * s_A;
	c_2SM = c_S - 2 * s_U1 * s_U2 / c_SqA;

	if (isnan(c_2SM))
	    c_2SM = 0;

	C = f / 16 * c_SqA * (4 + f * (4 - 3 * c_SqA));
	L_P = lambda;
	lambda = L + (1 - C) * f * s_A *
	    (S + C * s_S * (c_2SM + C * c_S * (2 * c_2SM * c_2SM - 1)));
    } while ((fabs(lambda - L_P) > 1.0e-12) && (--i > 0));

    if (i == 0)
	return NAN;		// formula failed to converge

    uSq = c_SqA * ((a * a) - (b * b)) / (b * b);
    A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
    B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
    d_S = B * s_S * (c_2SM + B / 4 *
		     (c_S * (-1 + 2 * c_2SM * c_2SM) - B / 6 * c_2SM *
		      (-3 + 4 * s_S * s_S) * (-3 + 4 * c_2SM * c_2SM)));

    if (ib != NULL)
	*ib = atan2(c_U2 * sin(lambda), c_U1 * s_U2 - s_U1 * c_U2 * cos(lambda));
    if (fb != NULL)
	*fb = atan2(c_U1 * sin(lambda), c_U1 * s_U2 * cos(lambda) - s_U1 * c_U2);

    return (WGS84B * A * (S - d_S));
}
/*@+mustdefine@*/

/* Distance in meters between two points specified in degrees. */
double earth_distance(double lat1, double lon1, double lat2, double lon2)
{
	return earth_distance_and_bearings(lat1, lon1, lat2, lon2, NULL, NULL);
}