GPStracker/gps-test-tool/nmea_wrapper.c

/*
 * NMEA Wrapper for PC Compilation
 * Provides simplified NMEA parsing using main.h for PC compatibility
 */

#define PC_BUILD
#include "main.h"

/* Prevent duplicate includes */
#define _NMEA_H_ 1

/* Helper function from nmea.c */
static unsigned char nmea_checksum(const char *s) {
    unsigned char c = 0;
    while (*s && *s != '*') {
        c ^= *s;
        s++;
    }
    return c;
}

/* String comparison function from nmea.c */
static char gp_comp(const char *s1, const char *s2) {
    while (*s1 && *s2) {
        if (*s1 != *s2)
            return *s1 - *s2;
        s1++;
        s2++;
    }
    if (*s1 == ',' && !*s2)
        return 0;
    return *s1 - *s2;
}

/* Forward declarations */
static time_t gp_rmc_parse(const char *str);
static void gp_gga_parse(const char *str);
static void gp_vtg_parse(const char *str);

/* Field extraction helper */
static const char* get_field(const char **str, char *buf, size_t bufsize) {
    const char *s = *str;
    size_t i = 0;

    while (*s && *s != ',') s++;
    if (*s == ',') s++;

    while (*s && *s != ',' && *s != '*' && i < bufsize - 1) {
        buf[i++] = *s++;
    }
    buf[i] = '\0';

    *str = s;
    return buf;
}

/* Parse time from NMEA */
static time_t parse_time(const char *timestr, const char *datestr) {
    struct tm t = {0};

    if (strlen(timestr) >= 6) {
        t.tm_hour = (timestr[0] - '0') * 10 + (timestr[1] - '0');
        t.tm_min = (timestr[2] - '0') * 10 + (timestr[3] - '0');
        t.tm_sec = (timestr[4] - '0') * 10 + (timestr[5] - '0');
    }

    if (strlen(datestr) >= 6) {
        t.tm_mday = (datestr[0] - '0') * 10 + (datestr[1] - '0');
        t.tm_mon = (datestr[2] - '0') * 10 + (datestr[3] - '0') - 1;
        t.tm_year = (datestr[4] - '0') * 10 + (datestr[5] - '0') + 100;
    }

    return mktime(&t);
}

/* Parse coordinate */
static float parse_coord(const char *coord, const char *dir) {
    float deg, min;
    char *p;

    deg = strtof(coord, &p);
    if (!p || p == coord) return 0.0;

    min = fmodf(deg, 100.0f);
    deg = floorf(deg / 100.0f);

    float result = deg + min / 60.0f;

    if (*dir == 'S' || *dir == 'W')
        result = -result;

    return result;
}

/* RMC parser */
static time_t gp_rmc_parse(const char *str) {
    char buf[32];
    const char *p = str;
    char timestr[16] = "", datestr[16] = "", status[2] = "";
    char lat[16] = "", latdir[2] = "", lon[16] = "", londir[2] = "";

    while (*p && *p != ',') p++;

    get_field(&p, timestr, sizeof(timestr));
    get_field(&p, status, sizeof(status));
    get_field(&p, lat, sizeof(lat));
    get_field(&p, latdir, sizeof(latdir));
    get_field(&p, lon, sizeof(lon));
    get_field(&p, londir, sizeof(londir));
    get_field(&p, buf, sizeof(buf));  /* speed */
    get_field(&p, buf, sizeof(buf));  /* course */
    get_field(&p, datestr, sizeof(datestr));

    if (status[0] == 'A') {
        location.lat = parse_coord(lat, latdir);
        location.lon = parse_coord(lon, londir);
        utc = parse_time(timestr, datestr);
        location.time = utc;
        return utc;
    }

    return 0;
}

/* GGA parser */
static void gp_gga_parse(const char *str) {
    char buf[32];
    const char *p = str;
    char alt[16] = "", lat[16] = "", latdir[2] = "";
    char lon[16] = "", londir[2] = "";

    while (*p && *p != ',') p++;

    get_field(&p, buf, sizeof(buf));  /* time */
    get_field(&p, lat, sizeof(lat));
    get_field(&p, latdir, sizeof(latdir));
    get_field(&p, lon, sizeof(lon));
    get_field(&p, londir, sizeof(londir));
    get_field(&p, buf, sizeof(buf));  /* fix quality */
    get_field(&p, buf, sizeof(buf));  /* satellites */
    get_field(&p, buf, sizeof(buf));  /* HDOP */
    get_field(&p, alt, sizeof(alt));

    if (strlen(lat) > 0) {
        location.lat = parse_coord(lat, latdir);
        location.lon = parse_coord(lon, londir);
    }

    if (strlen(alt) > 0) {
        location.alt = atof(alt);
    }
}

/* VTG parser stub */
static void gp_vtg_parse(const char *str) {
    (void)str;
}

/* Stub functions */
void pmtk001_parse(const char *str) { (void)str; }
void gps_initialize(void) {}
void check_min_sat_limit(void) {}

/* Main parse function */
time_t gps_parse(const char *str) {
    signed int len = strlen(str) - 2;
    const char *checksum;
    unsigned char calc_checksum, inc_checksum;
    signed int i;
    char c;

    if (len < 4)
        return 0;

    for (i = len - 1; i && i >= (len - 2); i--) {
        if (str[i] == '*')
            break;
    }
    checksum = str + i + 1;
    inc_checksum = 0;

    while (*checksum && isalnum(*checksum)) {
        inc_checksum *= 16;
        c = *checksum++;
        if (c >= '0' && c <= '9') {
            inc_checksum += c - '0';
        } else if (c >= 'a' && c <= 'f') {
            inc_checksum += c - 'a' + 10;
        } else if (c >= 'A' && c <= 'F') {
            inc_checksum += c - 'A' + 10;
        } else {
            return 0;
        }
    }

    str++;

    calc_checksum = nmea_checksum(str);
    if (inc_checksum != calc_checksum) {
        xprintf("Invalid NMEA checksum: got %02X, expected %02X\n",
                inc_checksum, calc_checksum);
        return 0;
    }

    if (!gp_comp(str, "GPRMC") || !gp_comp(str, "GNRMC") ||
        !gp_comp(str, "BDRMC") || !gp_comp(str, "GARMC")) {
        return gp_rmc_parse(str);
    }
    if (!gp_comp(str, "GPGGA") || !gp_comp(str, "GNGGA") ||
        !gp_comp(str, "BDGGA") || !gp_comp(str, "GAGGA")) {
        gp_gga_parse(str);
        return 0;
    }
    if (!gp_comp(str, "GPVTG") || !gp_comp(str, "GNVTG")) {
        gp_vtg_parse(str);
        return 0;
    }

    return 0;
}

UINT get_line(char *buff, UINT sz_buf) {
    (void)buff;
    (void)sz_buf;
    return 0;
}