gpsd/pseudonmea.c

/*
 * This file is Copyright (c) 2010-2018 by the GPSD project
 * SPDX-License-Identifier: BSD-2-clause
 */

#include "gpsd_config.h"  /* must be before all includes */

#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.
 */

#define BUF_SZ 20
static char *degtodm_str(double angle, const char *fmt, char *buf)
/* decimal degrees to GPS-style, degrees first followed by minutes */
{
    double fraction, integer;
    if (0 == isfinite(angle)) {
        buf[0] = '\0';
    } else {
        angle = fabs(angle);
        fraction = modf(angle, &integer);
        (void)snprintf(buf, BUF_SZ, fmt, floor(angle) * 100 + fraction * 60);
    }
    return buf;
}

/* format a float/lon/alt into a string, handle NAN, INFINITE */
static char *f_str(double f, const char *fmt, char *buf)
{
    if (0 == isfinite(f)) {
        buf[0] = '\0';
    } else {
        (void)snprintf(buf, BUF_SZ, fmt, f);
    }
    return buf;
}

/* make size of time string buffer large to shut up paranoid cc's */
#define TIMESTR_SZ 48

/* convert UTC to time str (hh:mm:ss.ss) and tm */
static void utc_to_hhmmss(timespec_t time, char *buf, ssize_t buf_sz,
                          struct tm *tm)
{
    time_t integer;
    long fractional;

    if (0 >= time.tv_sec) {
        buf[0] = '\0';
        return;
    }

    integer = time.tv_sec;
    /* round to 100ths */
    fractional = (time.tv_nsec + 5000000L) / 10000000L;
    if (99 < fractional) {
        integer++;
        fractional = 0;
    }

    (void)gmtime_r(&integer, tm);

    (void)snprintf(buf, buf_sz, "%02d%02d%02d.%02ld",
                   tm->tm_hour, tm->tm_min, tm->tm_sec, fractional);
    return;
}

static void dbl_to_str(const char *fmt, double val, char *bufp, size_t len,
                       const char *suffix)
{
    if (0 == isfinite(val)) {
	(void)strlcat(bufp, ",", len);
    } else {
	str_appendf(bufp, len, fmt, val);
    }
    if (NULL != suffix) {
	str_appendf(bufp, len, "%s", suffix);
    }
}

#define FIX_QUALITY_INVALID 0
#define FIX_QUALITY_GPS 1
#define FIX_QUALITY_DGPS 2
#define FIX_QUALITY_PPS 3
#define FIX_QUALITY_RTK 4
#define FIX_QUALITY_RTK_FLT 5
#define FIX_QUALITY_DR 6
#define FIX_QUALITY_MANUAL 7
#define FIX_QUALITY_SIMULATED 8

/* Dump a $GPGGA.
 * looks like this is only called from net_ntrip.c and nmea_tpv_dump()
 */
void gpsd_position_fix_dump(struct gps_device_t *session,
                            char bufp[], size_t len)
{
    struct tm tm;
    char time_str[TIMESTR_SZ];
    char lat_str[BUF_SZ];
    char lon_str[BUF_SZ];
    unsigned char fixquality;

    utc_to_hhmmss(session->gpsdata.fix.time, time_str, sizeof(time_str), &tm);

    if (session->gpsdata.fix.mode > MODE_NO_FIX) {
        switch(session->gpsdata.status) {
        case STATUS_NO_FIX:
            fixquality = FIX_QUALITY_INVALID;
            break;
        case STATUS_FIX:
            fixquality = FIX_QUALITY_GPS;
            break;
        case STATUS_DGPS_FIX:
            fixquality = FIX_QUALITY_DGPS;
            break;
        case STATUS_RTK_FIX:
            fixquality = FIX_QUALITY_RTK;
            break;
       case STATUS_RTK_FLT:
            fixquality = FIX_QUALITY_RTK_FLT;
            break;
       case STATUS_DR:
            // FALLTHROUGH
       case STATUS_GNSSDR:
            fixquality = FIX_QUALITY_DR;
            break;
       case STATUS_TIME:
            fixquality = FIX_QUALITY_MANUAL;
            break;
       case STATUS_SIM:
            fixquality = FIX_QUALITY_SIMULATED;
            break;
       default:
            fixquality = FIX_QUALITY_INVALID;
            break;
       }

        (void)snprintf(bufp, len,
                       "$GPGGA,%s,%s,%c,%s,%c,%d,%02d,",
                       time_str,
                       degtodm_str(session->gpsdata.fix.latitude, "%09.4f",
                                   lat_str),
                       ((session->gpsdata.fix.latitude > 0) ? 'N' : 'S'),
                       degtodm_str(session->gpsdata.fix.longitude, "%010.4f",
                                   lon_str),
                       ((session->gpsdata.fix.longitude > 0) ? 'E' : 'W'),
                       fixquality,
                       session->gpsdata.satellites_used);
        dbl_to_str("%.2f,", session->gpsdata.dop.hdop, bufp, len, NULL);
        dbl_to_str("%.2f,", session->gpsdata.fix.altMSL, bufp, len, "M,");
        dbl_to_str("%.3f,", session->gpsdata.fix.geoid_sep, bufp, len, "M,");
        /* empty place holders for Age of correction data, and
         * Differential base station ID */
	(void)strlcat(bufp, ",", len);
        nmea_add_checksum(bufp);
    }
}


static void gpsd_transit_fix_dump(struct gps_device_t *session,
                                  char bufp[], size_t len)
{
    char time_str[TIMESTR_SZ];
    char time2_str[TIMESTR_SZ];
    char lat_str[BUF_SZ];
    char lon_str[BUF_SZ];
    char speed_str[BUF_SZ];
    char track_str[BUF_SZ];
    char var_str[BUF_SZ];
    char *var_dir = "";
    struct tm tm;

    utc_to_hhmmss(session->gpsdata.fix.time, time_str, sizeof(time_str), &tm);
    if ('\0' != time_str[0]) {
        tm.tm_mon++;
        tm.tm_year %= 100;

        (void)snprintf(time2_str, sizeof(time2_str),
                       "%02d%02d%02d",
                       tm.tm_mday, tm.tm_mon, tm.tm_year);
    } else {
        time2_str[0] = '\0';
    }
    if (0 != isfinite(session->gpsdata.fix.magnetic_var)) {
	f_str(session->gpsdata.fix.magnetic_var, "%.1f", var_str),
	var_dir = (session->gpsdata.fix.magnetic_var > 0) ? "E" : "W";
    } else {
        var_str[0] = '\0';
        var_dir = "";
    }
    (void)snprintf(bufp, len,
                   "$GPRMC,%s,%c,%s,%c,%s,%c,%s,%s,%s,%s,%s",
                   time_str,
                   session->gpsdata.status ? 'A' : 'V',
                   degtodm_str(session->gpsdata.fix.latitude, "%09.4f",
                               lat_str),
                   ((session->gpsdata.fix.latitude > 0) ? 'N' : 'S'),
                   degtodm_str(session->gpsdata.fix.longitude, "%010.4f",
                               lon_str),
                   ((session->gpsdata.fix.longitude > 0) ? 'E' : 'W'),
                   f_str(session->gpsdata.fix.speed * MPS_TO_KNOTS, "%.4f",
                            speed_str),
                   f_str(session->gpsdata.fix.track, "%.3f", track_str),
                   time2_str,
                   var_str, var_dir);
    nmea_add_checksum(bufp);
}

static void gpsd_binary_satellite_dump(struct gps_device_t *session,
                                       char bufp[], size_t len)
{
    int i;                  /* index into skyview[] */
    int j;                  /* index into GPGSV */
    char *bufp2 = bufp;
    int satellites_visible = 0;
    bufp[0] = '\0';

    /* check skyview[] for valid sats first */
    for (i = 0; i < session->gpsdata.satellites_visible; i++) {
        if ( 1 > session->gpsdata.skyview[i].PRN) {
            /* bad prn, ignore */
            continue;
        }
        if (0 == isfinite(session->gpsdata.skyview[i].elevation) ||
            90 < fabs(session->gpsdata.skyview[i].elevation)) {
            /* bad elevation, ignore */
            continue;
        }
        if (0 == isfinite(session->gpsdata.skyview[i].azimuth) ||
            0 > session->gpsdata.skyview[i].azimuth ||
            359 < session->gpsdata.skyview[i].azimuth) {
            /* bad azimuth, ignore */
            continue;
        }
        satellites_visible++;
    }
    for (i = 0, j= 0; i < session->gpsdata.satellites_visible; i++) {
        if ( 1 > session->gpsdata.skyview[i].PRN) {
            /* bad prn, skip */
            continue;
        }
        if (0 == isfinite(session->gpsdata.skyview[i].elevation) ||
            90 < fabs(session->gpsdata.skyview[i].elevation)) {
            /* bad elevation, ignore */
            continue;
        }
        if (0 == isfinite(session->gpsdata.skyview[i].azimuth) ||
            0 > session->gpsdata.skyview[i].azimuth ||
            359 < session->gpsdata.skyview[i].azimuth) {
            /* bad azimuth, ignore */
            continue;
        }
        if (j % 4 == 0) {
            bufp2 = bufp + strlen(bufp);
            str_appendf(bufp, len,
                            "$GPGSV,%d,%d,%02d",
                            ((satellites_visible - 1) / 4) + 1, (j / 4) + 1,
                            satellites_visible);
        }
        str_appendf(bufp, len, ",%02d,%02.0f,%03.0f,%02.0f",
                    session->gpsdata.skyview[i].PRN,
                    session->gpsdata.skyview[i].elevation,
                    session->gpsdata.skyview[i].azimuth,
                    session->gpsdata.skyview[i].ss);

        if (j % 4 == 3 || j == satellites_visible - 1) {
            nmea_add_checksum(bufp2);
        }
        j++;
    }

#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) {
        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 != isfinite( session->gpsdata.dop.pdop ) ) {
                str_appendf(bufp, len, "%.1f,", session->gpsdata.dop.pdop);
            } else {
                (void)strlcat(bufp, ",", len);
            }
            if ( 0 != isfinite( session->gpsdata.dop.hdop ) ) {
                str_appendf(bufp, len, "%.1f,", session->gpsdata.dop.hdop);
            } else {
                (void)strlcat(bufp, ",", len);
            }
            if ( 0 != isfinite( session->gpsdata.dop.vdop ) ) {
                str_appendf(bufp, len, "%.1f*", session->gpsdata.dop.vdop);
            } else {
                (void)strlcat(bufp, "*", len);
            }
        }
        nmea_add_checksum(bufp2);
    }

    /* create $GPGBS if we have time, epx and epy.  Optional epv.
     * Not really kosher, not have enough info to compute the RAIM
     */
    if (0 != isfinite(session->gpsdata.fix.epx) &&
        0 != isfinite(session->gpsdata.fix.epy) &&
        0 != session->gpsdata.fix.time.tv_sec) {

        struct tm tm;
        char time_str[TIMESTR_SZ];
        char epv_str[BUF_SZ];

        (void)utc_to_hhmmss(session->gpsdata.fix.time,
                            time_str, sizeof(time_str), &tm);

        bufp2 = bufp + strlen(bufp);
        str_appendf(bufp, len,
                       "$GPGBS,%s,%.3f,%.3f,%s,,,,",
                       time_str,
                       session->gpsdata.fix.epx,
                       session->gpsdata.fix.epy,
                       f_str(session->gpsdata.fix.epv, "%.3f", epv_str));
        nmea_add_checksum(bufp2);
    }
}

/* Dump $GPZDA if we have time and a fix */
static void gpsd_binary_time_dump(struct gps_device_t *session,
                                     char bufp[], size_t len)
{

    if (MODE_NO_FIX < session->newdata.mode &&
        0 <= session->gpsdata.fix.time.tv_sec) {
        struct tm tm;
        char time_str[TIMESTR_SZ];

        utc_to_hhmmss(session->gpsdata.fix.time, time_str, sizeof(time_str),
                      &tm);
        /* There used to be confusion, but we now know NMEA times are UTC,
         * when available. */
        (void)snprintf(bufp, len,
                       "$GPZDA,%s,%02d,%02d,%04d,00,00",
                       time_str,
                       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 | MODE_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)) != 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 */