#include <stdio.h>
#include <stdlib.h>
#define GEO_OK 1
#define GEO_ERROR -10000
#define GEO_INVALID_LAT -10001
#define GEO_INVALID_LON -10002
float check_longitude(float lon) {
if (lon < -180 || lon > 180)
return GEO_INVALID_LON;
return lon;
}
float check_latitude(float lat) {
if (lat <= -90 || lat > 90)
return GEO_INVALID_LAT;
return lat;
}
typedef struct {
float lat;
float lon;
} GeoPoint;
int geopoint_check_error(GeoPoint *geo) {
if (geo->lat < GEO_ERROR)
return GEO_INVALID_LAT;
if (geo->lon < GEO_ERROR)
return GEO_INVALID_LON;
return GEO_OK;
}
char *geopoint_error_message(int error) {
switch (error) {
case GEO_INVALID_LAT:
return "latitude is invalid";
case GEO_INVALID_LON:
return "longitude is invalid";
default:
return "OK";
}
}
void geopoint_init(GeoPoint *geo, float lat, float lon) {
geo->lat = check_latitude(lat);
geo->lon = check_longitude(lon);
}
void geopoint_set_lat(GeoPoint *geo, float lat) {
geo->lat = check_latitude(lat);
}
void geopoint_set_lon(GeoPoint *geo, float lon) {
geo->lon = check_longitude(lon);
}
char *geopoint_gist(char *out, size_t size, GeoPoint *geo) {
snprintf(out, size, "%s%f %s%f",
geo->lat >= 0 ? "N" : "S",
fabs(geo->lat),
geo->lon >= 0 ? "E" : "W",
fabs(geo->lon)
);
return out;
}
void die(char *msg) {
printf("%s", msg);
exit(1);
}
int main(void) {
GeoPoint geo;
geopoint_init(&geo, 39.1915045, -96.6070506);
int error = geopoint_check_error(&geo);
if (error != GEO_OK)
die(geopoint_error_message(error));
printf("%f\n", geo.lat);
printf("%f\n", geo.lon);
char *msg = malloc(255);
printf("%s\n", geopoint_gist(msg, 255, &geo));
free(msg);
return 0;
}
