spOSMroute/main/gps.c

/***************************************************************************
 *            gps.c
 *
 *  Copyright  2010 - Steffen Pohle
 *  steffen@gulpe.de
 ****************************************************************************/

/*
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include "osmroute.h"
#include "gui.h"

#ifdef HAVE_LOCALE_H
  #include <locale.h>
#endif

#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>

#include "gps.h"
#include "memoryleak.h"
#include "draw.h"
#include "system.h"

int gps_getdatatime (char *text);
float gps_getlon (char *text);
float gps_getlat (char *text);
int gps_convert_line (char *line, struct gps_data *data);

struct gps_data gpspos;
struct gps_data gpsposvalid;

#if !defined(__MINGW32CE__) && !defined(_WIN32_WCE) && !defined(__MINGW32__)
char gpsdevice[GPS_DEVICELEN] = "serial:/dev/rfcomm0";
#else
char gpsdevice[GPS_DEVICELEN] = "serial:com1,38400";
#endif

int gpsflags = GPSF_LOG;
char gpsdata[GPS_INBUFSIZE];
int gpsdatalen = 0;
int gpsstatus = 0;				/* status: 0 = not running, 1 = running, -1 = error */
time_t gpsstarttime;			/* timestamp when we started to get gps informations */
int gpsdevtime = 0;				/* gps device time */
int gpslasttype = GPS_T_NONE;	/* type of the last opened device GPS_T_SERIAL, GPS_T_FILE */
struct gps_route *gpsroute;
char logfile[LEN_FILENAME] = "gpslog.nmea";


/*********************************************************************************************
 *
 * gpsroute stuff
 */
void gpsroute_free (struct gps_route *gr) {
	if (gr == gpsroute) gpsroute = NULL;
	if (gr->data) ml_free (gr->data);
	if (gr->pdata) ml_free (gr->pdata);
	ml_free (gr);
};


struct gps_route *gpsroute_new () {
	struct gps_route *gr = (struct gps_route*) ml_malloc (sizeof (struct gps_route));
	gr->max = 0;
	gr->cnt = 0;
	gr->data = NULL;
	gr->pmax = 0;
	gr->pcnt = 0;
	gr->pdata = NULL;
	return gr;
};


void gpsroute_addpos (struct gps_route *gr, float lon, float lat, float speed, time_t t) {
	if (gr == NULL) return;
	
	if (gr->cnt+1 >= gr->max) {
		struct gps_routedata *tmp;

		gr->max = gr->max + 1024;
		tmp = (struct gps_routedata*) ml_malloc (sizeof (struct gps_routedata) * (gr->max));
		ml_addinfo (tmp, "gpsroute");
		if (gr->data) {
			memcpy (tmp, gr->data, sizeof (struct gps_routedata) * gr->cnt);
			ml_free (gr->data);
		}
		gr->data = tmp;
	}
	gr->data[gr->cnt].lon = lon;
	gr->data[gr->cnt].lat = lat;
	gr->data[gr->cnt].speed = speed;
	gr->data[gr->cnt].time = t;
	gr->cnt++;
};


void gpsroute_addpoi (struct gps_route *gr, float lon, float lat, char *text) {
	if (gr == NULL) return;

	if (gr->pcnt+1 >= gr->pmax) {
		struct gps_routepoidata *tmp;

		gr->pmax = gr->pmax + 1024;
		tmp = (struct gps_routepoidata*) ml_malloc (sizeof (struct gps_routepoidata) * (gr->pmax));
		ml_addinfo (tmp, "gpspoiroute");
		if (gr->pdata) {
			memcpy (tmp, gr->pdata, sizeof (struct gps_routepoidata) * gr->pcnt);
			ml_free (gr->pdata);
		}
		gr->pdata = tmp;
	}
	gr->pdata[gr->pcnt].lon = lon;
	gr->pdata[gr->pcnt].lat = lat;
	strncpy (gr->pdata[gr->pcnt].name, text, GPS_ROUTEPOILEN);
	gr->pcnt++;
};


void gpsroute_exportgpx (struct gps_route *gr, char *filename) {
	int i;
	float olon = 0.0, olat = 0.0;
	char tt[128];
	FILE *f;
	
	if (gr) {
		f = fopen (filename, "w");
		fprintf (f, "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?>\n");
		fprintf (f, "  <gpx xmlns=\"http://www.topografix.com/GPX/1/1\" creator=\"sposmroute - http://sposmroute.gulpe.de\">\n");

		fprintf (f, "    <trk><name>noname</name>\n");
		for (i = 0; i < gr->cnt; i++) {
			if (i == 0 || (olon != gr->data[i].lon && olat != gr->data[i].lat)) {
				strftime (tt, 32, "%Y-%m-%dT%H:%M:%SZ", localtime(&gr->data[i].time));
				fprintf (f, "      <trkpt lat=\"%f\" lon=\"%f\"><time>%s</time></trkpt>\n", gr->data[i].lat, gr->data[i].lon, tt);
				olon = gr->data[i].lon;
				olat = gr->data[i].lat;
			}
		}
		fprintf (f, "    </trk>\n");
		for (i = 0; i < gr->pcnt; i++) {
			fprintf (f, "    <wpt lat=\"%f\" lon=\"%f\">\n", gr->pdata[i].lat, gr->pdata[i].lon);
			fprintf (f, "       <name>%s</name>\n", gr->pdata[i].name);
			fprintf (f, "    </wpt>\n");			         
		}
		fprintf (f, "  </gpx>\n");
		fclose (f);
	}
};


/*
void gpsroute_saveroute (struct gps_route *gr, char *filename) {
	int i;
	float olon = 0.0, olat = 0.0;
	FILE *f;
	char tt[32];
	
	if (gr) {
		f = fopen (filename, "w");
		for (i = 0; i < gr->cnt; i++) {
			if (i == 0 || (olon != gr->data[i].lon && olat != gr->data[i].lat)) {
				strftime (tt, 32, "%Y-%m-%dT%H:%M:%SZ", localtime(&gr->data[i].time));
				fprintf (f, "%s lon:%7.4f lat:%7.4f\n", tt, gr->data[i].lon, gr->data[i].lat);
				olon = gr->data[i].lon;
				olat = gr->data[i].lat;
			}
		}
		fclose (f);
	}
};
*/

/*********************************************************************************************
 *
 * variables and functions needed by all gps_file_device_ functions.
 * gps_file_device* will be used to simulate gps log files, this makes it possible to playback
 * driving on the street without going out.
 *
 */
char *gps_file_buffer = NULL;		// buffer to keep the data inside
int gps_file_buflen;				// bytes inside the buffer
int gps_file_fd = 0;				// file descriptor
int gps_file_size = 0;				// file size
char gps_file_fn[GPS_DEVICELEN];	// currently open file
/* the times will be used to detect when we need to send another line, so we can simulate the 
 * whole gps stream also with simulated time */
time_t gps_file_hosttime;			// daytime when we started to read the log file (in seconds)
int gps_file_filetime;				// daytime of the first time found (we use $GPRMC for time) (in seconds)
int gps_file_state;					// simulation?


int gps_file_get_state () { return gps_file_state; };

void gps_file_set_state (int state) {
	if (state == GPSF_RUN || state == GPSF_INIT)  gps_file_state = GPSF_INIT;
	else gps_file_state = GPSF_PAUSE; 
};

void gps_file_set_pos (int newpos) {
	if (newpos >= gps_file_size) lseek (gps_file_fd, 0, SEEK_END);
	else if (newpos < 0) lseek (gps_file_fd, 0, SEEK_SET);
	else lseek (gps_file_fd, newpos, SEEK_SET);
	gps_file_state = GPSF_INIT;
};

int gps_file_get_pos () {
	int i;
	
	i = lseek (gps_file_fd, 0, SEEK_CUR);

	return i;
};

int gps_file_get_size () { return gps_file_size; };


int gps_file_device_open () {
	/* copy filename */
	strncpy (gps_file_fn, gpsdevice+5, GPS_DEVICELEN);
	
#if defined(__MINGW32CE__) || defined(_WIN32_WCE) || defined(__MINGW32__)
	gps_file_fd = open (gps_file_fn, O_RDONLY | _O_BINARY);
#else
	gps_file_fd = open (gps_file_fn, O_RDONLY);
#endif
	if (gps_file_fd == -1) {
		d_printf ("%s:%d gps_file_device_open could not open file:%s   gpsdevice:%s", __FILE__, __LINE__, 
				gps_file_fn, gpsdevice);
		return 0;
	}
	if (gps_file_buffer) ml_free (gps_file_buffer);
	gps_file_size = lseek (gps_file_fd, 0, SEEK_END);
	lseek (gps_file_fd, 0, SEEK_SET);
	gps_file_buffer = (char *) ml_malloc (GPS_INBUFSIZE);
	gps_file_state = GPSF_INIT;
	gpswin_show ();
	return 1;
};


void gps_file_device_close () {
	if (gps_file_fd > 0) close (gps_file_fd);
	gps_file_size = 0;
	gps_file_fd = 0;
	gps_file_state = GPSF_NONE;
	gps_file_fn[0] = 0;
	if (gps_file_buffer) ml_free (gps_file_buffer);
	gps_file_buffer = NULL;
	gps_file_buflen = 0;
};


int gps_file_device_read (char *ptr, int ptrsize) {
	int i, nr = 0, datatime;
	time_t curtime;
	int eof = 0;

	/*
	 * test if we are in state init
	 */
	if (gps_file_state == GPSF_INIT) {
		gps_file_hosttime = time (NULL);
		gps_file_filetime = -1; /* we still don't have any data to get the time */
		gps_file_buflen = 0;
		gps_file_state = GPSF_RUN;
	}		
	
	if (gps_file_state == GPSF_RUN) {
		/*
		 * refill the buffer
		 */
		if (gps_file_buflen < GPS_INBUFSIZE) {
			i = read (gps_file_fd, gps_file_buffer + gps_file_buflen, GPS_INBUFSIZE-gps_file_buflen);
			gps_file_buflen += i;
			if (i == 0) eof = 1;
		}

		/* 
		 * check if we can send a new line
		 */
		curtime = time (NULL);
		if (strncmp (gps_file_buffer, "$GPRMC,", 7) == 0) {
			datatime = gps_getdatatime (gps_file_buffer+7);
			if (gps_file_filetime == -1) gps_file_filetime = datatime;
		}

		if (strncmp (gps_file_buffer, "$GPRMC,", 7) != 0 || (curtime-gps_file_hosttime >= datatime-gps_file_filetime)) {
			for (i = 0; i < (ptrsize-1) && i < gps_file_buflen; i++) {
				ptr[i] = gps_file_buffer[i];
				if (gps_file_buffer[i] == '\r' || gps_file_buffer[i] == '\n') {
					i++;
					ptr[i] = 0;
					break;
				}
			}
	
			/* move the leftover inside the buffer to the beginning */
			if (i >= 0) {
				if (gps_file_buflen > 0) {
					memmove (gps_file_buffer, gps_file_buffer+i, GPS_INBUFSIZE-i);
					gps_file_buflen = gps_file_buflen - i;
				}
				nr = i;
			}
		}

		if (gps_file_buflen < GPS_INBUFSIZE && eof) gps_file_state = GPSF_END;
	}
	
	return nr;
};


/********************************************************************************************
 * convert text "173436.000" into time in seconds form 00:00:00
 */
int gps_getdatatime (char *text) {
	char c_hms[3][3];  /* hours, mins, secs */
	int i;

	for (i = 0; i < 2; i++) {
		c_hms[0][i] = text[i];
		c_hms[1][i] = text[2+i];
		c_hms[2][i] = text[4+i];
	}	
	c_hms[0][i] = '\0';
	c_hms[1][i] = '\0';
	c_hms[2][i] = '\0';

	return (atoi (c_hms[0]) * 3600 + atoi (c_hms[1]) * 60 + atoi (c_hms[2]));
};


float gps_getlon (char *text) {
	// GGGMM.mmmm
	float ret;
	char g[4];

	memcpy (g, text, 3);
	g[3] = 0;

	ret = atof (text+3)/60.0 + (float) atoi (g);
	
	return ret;
};


float gps_getlat (char *text) {
	// GGMM.mmmm
	float ret;
	char g[3];

	memcpy (g, text, 2);
	g[2] = 0;

	ret = atof (text+2)/60.0 + (float) atoi (g);
	
	return ret;
};


/********************************************************************************************
 *
 * other gps stuff
 *
 */

/*
 * return type of currently set up gps device
 */
int gps_get_devicetype () {
	if (strncmp (gpsdevice, "serial:", 7) == 0) return GPS_T_SERIAL;
	else if (strncmp (gpsdevice, "file:", 5) == 0) return GPS_T_FILE;
	else return GPS_T_NONE;
};


/*
 * setup the new device and reinit device if it was running
 */
void gps_set_device (char *device) {
	int oldstatus = gpsstatus;

	d_printf ("%s:%d gps_set_device (%s)", __FILE__, __LINE__, device);
	gps_stop ();
	strncpy (gpsdevice, device, GPS_DEVICELEN);
	if (oldstatus == 1 || oldstatus == -1)
		gps_start ();
};


char *gps_get_device () {
	d_printf ("%s:%d gps_get_device (%s)", __FILE__, __LINE__, gpsdevice);
	return gpsdevice;
};


void gps_start () {
	int error = 0;
	char fn[LEN_FILENAME];

	d_printf ("%s:%d gps_start device(%s)", __FILE__, __LINE__, gpsdevice);
	gpsstarttime = time (NULL);

	strftime (fn, LEN_FILENAME, "%F-%H-%M%S.nmea", localtime(&gpsstarttime));
	snprintf (logfile, LEN_FILENAME, "%s%s", cfg.logpath, fn);

	d_printf ("gps-logfile set to:%s", logfile);
	gpsdevtime = -1;

	if (gpsroute == NULL) gpsroute = gpsroute_new();
	else {
		gpsroute->cnt = 0;	
		gpsroute->pcnt = 0;
	}

	gpslasttype = gps_get_devicetype ();
	if (gpslasttype == GPS_T_SERIAL) error = gps_serial_device_open ();
	else if (gpslasttype == GPS_T_FILE) error = gps_file_device_open ();
	else error = 0;

	if (error) {
		d_printf ("%s:%d gps_start : ok", __FILE__, __LINE__);
		gpsstatus = 1;
		draw_set_flag (DRAW_GPS);
	}
	else {
		d_printf ("%s:%d gps_start : error", __FILE__, __LINE__);
		gpsstatus = -1;
		draw_del_flag (DRAW_GPS);
	}

	gpsdatalen = 0;
};


void gps_stop () {
	d_printf ("%s:%d gps_stop", __FILE__, __LINE__);
	if (gpslasttype == GPS_T_SERIAL) gps_serial_device_close ();
	else if (gpslasttype == GPS_T_FILE) gps_file_device_close ();
	gpsstatus = 0;
	gpsdatalen = 0;
	draw_del_flag (DRAW_GPS);
	d_printf ("gps is clean now.");
};


/*
 * convert the givin line into the gps_data struct, the valid flag will
 * not been deleted first, only if there is no active flag
 */
int gps_convert_line (char *line, struct gps_data *data) {
	char *pos;
	float lon, lat;
	int i;

	/* reset poi data */
	data->poi.name[0] = 0;
	
	/* kick the checksum away */
	if ((pos = strchr (line, '*'))) {
		pos[0] = 0;
	}

	/*
	 * read the gps line
	 */
	pos = line;
	if (strncmp (pos, "$GPRMC", 6) == 0) {
		data->time = gpsstarttime;
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// Time
		pos++;
		i = gps_getdatatime (pos);
		if (gpsdevtime == -1) gpsdevtime = i;
		if (gpsdevtime > i) i = i + (3600*24);
		data->time += (i - gpsdevtime);
			
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// Active
		pos++;
		if (pos[0] == 'A') data->valid = 1;
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// North-South
		pos++;
		data->lat = gps_getlat (pos);
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// N|S
		pos++;
		if (pos[0] == 'S') data->lat = -data->lat;
		else if (pos[0] != 'N') return 0;
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// East-West
		pos++;
		data->lon = gps_getlon (pos);
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// E|W
		pos++;
		if (pos[0] == 'W') data->lon = -data->lon;
		else if (pos[0] != 'E') return 0;
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// Speed
		pos++;
		data->speed = atof (pos) * GPS_KNOTEN2KMH;
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// direction
		pos++;
		if (data->speed > 1.5) data->direction = atof (pos);
	}
	else if (strncmp (pos, "$POI,", 5) == 0) {
		if ((pos = strchr (pos, ',')) == NULL) return 0;
		pos++;
		lon = atof (pos);
		if ((pos = strchr (pos, ',')) == NULL) return 0;
		pos++;
		lat = atof (pos);
		if ((pos = strchr (pos, ',')) == NULL) return 0;
		pos++;
		strncpy (data->poi.name, pos, GPS_ROUTEPOILEN);
		data->poi.lon = lon;
		data->poi.lat = lat;
	}
	else if (strncmp (pos, "$GPGGA", 6) == 0) {
		data->time = gpsstarttime;
		if ((pos = strchr (pos, ',')) == NULL) return 0; // Time
		pos++;
		
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// North-South
		pos++;
		data->lat = gps_getlat (pos);
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// N|S
		pos++;
		if (pos[0] == 'S') data->lat = -data->lat;
		
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// East-West
		pos++;
		data->lon = gps_getlon (pos);

		if ((pos = strchr (pos, ',')) == NULL) return 0;	// E|W
		pos++;
		if (pos[0] == 'W') data->lon = -data->lon;

		if ((pos = strchr (pos, ',')) == NULL) return 0;	// Quallity
		pos++;
		data->quality = atoi (pos);

		if ((pos = strchr (pos, ',')) == NULL) return 0;	// Numer of Satelites
		pos++;
		data->numofsatelites = atoi (pos);

		if ((pos = strchr (pos, ',')) == NULL) return 0;	// HDOP
		pos++;
		data->hdop = atof (pos);
			
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// Height in m
		pos++;
		data->height = atof (pos);
	}
	else if (strncmp (pos, "$GPGSV", 6) == 0) {
		int n, satnr;
	
		data->time = gpsstarttime;
		if ((pos = strchr (pos, ',')) == NULL) return 0; // max data blocks
		pos++;
		
		if ((pos = strchr (pos, ',')) == NULL) return 0;	// current data block
		pos++;
		satnr = atoi (pos);
		if (satnr == 1) for (n = 0; n < 32; n++) {
			data->sat[n].deg_elev = 0;
			data->sat[n].deg_north = 0;
			data->sat[n].quality = 0;
		}

		if ((pos = strchr (pos, ',')) == NULL) return 0;	// number of sats
		pos++;

		if ((pos = strchr (pos, ',')) == NULL) return 0;	// first data
		n = 0;
		while (pos && n < 4) {
			n++;
			pos++;
			satnr = atoi (pos);								// satnr;
			if (satnr > 32 || satnr < 0) {
				d_printf ("%s:%d satnr invlid: %d Line:'%s'", __FILE__, __LINE__, satnr, line);
				return 0;
			}
			if ((pos = strchr (pos, ',')) == NULL) return 0;	// elev in deg
			pos++;
			if (satnr != 0)	data->sat[satnr-1].deg_elev = atoi (pos);
			if ((pos = strchr (pos, ',')) == NULL) return 0;	// position in deg from north
			pos++;
			if (satnr != 0)	data->sat[satnr-1].deg_north = atoi (pos);
			if ((pos = strchr (pos, ',')) == NULL) return 0;	// quality
			pos++;
			if (pos[0] != '*' && satnr != 0)
				data->sat[satnr-1].quality = atoi (pos);
			pos = strchr (pos, ','); // next data
		}
	}
	return 1;
};


/*
 * returns the pointer of the last know datablock (actually only a pointer to position)
 * or returns NULL if gps is not started correctly
 */
struct gps_data *gps_loop () {
	int dataread = 0, i;
	int to = GPS_LOOP_TIMEOUT;
	char line[2*GPS_LINELEN];
    time_t call;
    
#ifdef HAVE_LOCALE_H
	setlocale(LC_ALL, "C");
#endif

	gpspos.valid = gpsposvalid.valid = 0;
    call = time (NULL);
	/*
	 * read all completed lines
	 */
	do {
        if (time (NULL) - call > 3) d_printf ("time??????");
		/* 
		 * check if gps is open and fillup the buffer
		 */
		if (gpsstatus <= 0) return NULL;
		if (gpslasttype == GPS_T_SERIAL) dataread = gps_serial_device_read (gpsdata + gpsdatalen, GPS_INBUFSIZE - gpsdatalen);
		else if (gpslasttype == GPS_T_FILE) dataread = gps_file_device_read (gpsdata + gpsdatalen, GPS_INBUFSIZE - gpsdatalen);
		else dataread = -1;
		
		if (dataread < 0) {
			gps_stop();
			gpsstatus = -1;
		}
		else if (dataread+gpsdatalen > GPS_INBUFSIZE) {
			d_printf ("%s:%d gps_loop: ERROR datapos(%d) > GPS_INBUFSIZE(%d)", __FILE__, __LINE__, gpsdatalen + dataread, GPS_INBUFSIZE);
			gpsdatalen = GPS_INBUFSIZE;
			gps_stop ();
		}
		else gpsdatalen += dataread;
	
		for (i = 0; i < GPS_LINELEN*2 && i < gpsdatalen && gpsdata[i] != '\n' && gpsdata[i] != '\r' && gpsdata[i] != '\0'; i++) {
			line[i] = gpsdata[i];
		}

		if (gpsdata[i] == '\n' || gpsdata[i] == '\r' || gpsdata[i] == '\0') {
			if (gpsdatalen - (i+1) > 0) {
				memmove (gpsdata, gpsdata+i+1, gpsdatalen - (i+1));
				gpsdatalen = gpsdatalen - (i+1);
			} 
			else gpsdatalen = 0;
		}
		else if (i == gpsdatalen || i >= GPS_LINELEN*2) {
			break;
		}
		line[i] = 0;

		/* write into logfile */
		if (i > 0) {
			if (gpslasttype != GPS_T_FILE && gpsflags & GPSF_LOG) gps_save_log (logfile, line);
			if (gps_convert_line (line, &gpspos) == 0) gpspos.valid = 0;
			else {
				if (gpspos.quality == 1) gpspos.valid = 1;
			}

			if (gpspos.valid == 1) {
				gpsposvalid = gpspos;
				gpsroute_addpos (gpsroute, gpspos.lon, gpspos.lat, gpspos.speed, gpspos.time);
			}
		}
	} while (gpsstatus > 0 && gpsdatalen > 0 && --to > 0);

#ifdef HAVE_LOCALE_H
	setlocale(LC_ALL, NULL);
#endif

	if (gpsposvalid.valid == 1) return &gpsposvalid;
	else return NULL;
};



/*********************************************************************
 * returns TRUE (1) if gps is running
 */
int gps_isrunning () {
	return (gpsstatus);
};


struct gps_data *gps_getposition () {
	if (gpsposvalid.valid == 1) return &gpsposvalid;
	else  return &gpspos;
};


/*
 * open logfile and add one line to the end. 
 * If fname==NULL the file name stored in logfile will be used.
 */
void gps_save_log (char *fname, char *text) {
	int f;
	
	if (fname == NULL && gpsstatus == 1 && logfile[0] != 0) 
		f = open (logfile, O_RDWR | O_CREAT, 0644);
	else 
		f = open (fname, O_RDWR | O_CREAT, 0644);

	if (f) {
		lseek (f, 0, SEEK_END);
		write (f, text, strlen (text));
#if !defined(__MINGW32CE__) && !defined(_WIN32_WCE) && !defined(__MINGW32__)
		write (f, "\n", 1);
#else
		write (f, "\n\r", 2);
#endif
		close (f);
	}
};


void gps_load_log (char *fn) {
	float minlon, minlat;
	float maxlon, maxlat;
	int start;
	struct gps_data *pos;
	char oldgps_dev[GPS_DEVICELEN];
	
	gps_stop ();
	strncpy (oldgps_dev, gpsdevice, GPS_DEVICELEN);
	snprintf (gpsdevice, GPS_DEVICELEN, "file:%s", fn);
	gps_start ();
	start = 1;
	while (gpsstatus == 1) {
		pos = gps_loop ();
		if (pos) if (pos->valid) { 
			if (start) {
				minlon = maxlon = pos->lon;
				minlat = maxlat = pos->lat;
				start = 0;
			}
			else if (pos->lon < minlon) minlon = pos->lon;
			else if (pos->lon > maxlon) maxlon = pos->lon;
			else if (pos->lat < minlat) minlat = pos->lat;
			else if (pos->lat > maxlat) maxlat = pos->lat;
		}
	}
	gps_stop ();
	strncpy (gpsdevice, oldgps_dev, GPS_DEVICELEN);
	if (start == 0) {
		view_lon = minlon+(maxlon-minlon)/2.0;
		view_lat = minlat+(maxlat-minlat)/2.0;
		draw();
	}
};