Added 5th argument for distance type. mi,km, or ft

Makefile

@@ -0,0 +1,8 @@
+CC=gcc
+CFLAGS=-shared -fPIC -o lib_mysqludf_haversine.so 
+MYSQLCONFIG=$$(mysql_config --cflags) -lm -DMYSQL_DYNAMIC_PLUGIN 
+main: 
+	$(CC) $(CFLAGS) lib_mysqludf_haversine.c $(MYSQLCONFIG)
+
+clean:
+	rm -f lib_mysqludf_haversine.so

README.md

@@ -8,12 +8,14 @@ Returns the haversine distance from two points
 Input parameters
 ----------------
 
-lat1 (real), lng1 (real), lat2 (real), lng2 (real)
+lat1 (real), lng1 (real), lat2 (real), lng2 (real), type (string - optinal - 'km', 'ft', 'mi')
 
 Output
 ------
 
-Distance in kilometers (real)
+Distance between the two points. The measurement is returned in kilometers (real)
+by default, however if you specify the 5th *type* argument you may return in other
+measurements.
 
 Install
 =======
@@ -70,3 +72,6 @@ Once installed, to calculate distance between two Latitude/Longitude points:
 
 The `SELECT` will return all the records with a distance less then 40 kilometers.
 
+    SELECT id, name FROM MY_PLACES WHERE haversine_distance(lat1, lng1, lat2, lng2, 'ft') < 25;
+
+The `SELET` will return all the records with a distance less then 25 feet.

lib_mysqludf_haversine.c

@@ -25,10 +25,11 @@
  * 			lng1 (real)
  * 			lat2 (real)
  * 			lng2 (real)
+ * 			type (string - 'km', 'ft', 'mi')
  *
  *
  * 		output:
- * 			distance in kilometers (real)
+ * 			distance in type of measurement (real)
  *
  *
  * To register this function:
@@ -92,12 +93,15 @@ haversine_distance_deinit( UDF_INIT* initid );
 double 
 haversine_distance( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error );
 
+void
+str_to_lowercase( char* src );
+
 
 
 my_bool 
 haversine_distance_init( UDF_INIT* initid, UDF_ARGS* args, char* message ) {
 
-	if ( args->arg_count != 4 ) {
+	if ( args->arg_count < 4 ) {
 		strcpy(message,"wrong number of arguments: haversine_distance() requires four arguments");
     	return 1;
   	}
@@ -122,6 +126,15 @@ haversine_distance_init( UDF_INIT* initid, UDF_ARGS* args, char* message ) {
 		args->arg_type[3] = REAL_RESULT;
   	}
 
+  	/*
+  	 * The 5th argument is the type of distance to return. It is
+  	 * optional. Valid arguments are 'km', 'ft', 'mi'
+  	 */
+  	if ( (args->arg_type[4] != STRING_RESULT) ) {
+		//strcpy( message, "haversine_distance() requires string as parameters 5" ); return 1;
+		args->arg_type[4] = STRING_RESULT;
+  	}
+
   	double *dist = malloc( sizeof(double) );
 	if ( dist == NULL ) {
 		strcpy(message, "haversine_distance() allocation error");
@@ -168,8 +181,24 @@ haversine_distance( UDF_INIT* initid, UDF_ARGS* args, char* is_null, char *error
 
 	result = ( R * c );
 
+	/*
+	 * If we have a 5th distance type argument...
+	 */
+	if (args->arg_count == 5) {
+		str_to_lowercase(args->args[4]);
+
+		if (strcmp(args->args[4], "ft") == 0) result *= 3280.8399;
+		if (strcmp(args->args[4], "mi") == 0) result *= 0.621371192;
+	}
+
 	return result;
 }
 
 
+void
+str_to_lowercase( char* src ) {
+	for (; *src; src++) *src = tolower(*src);
+}
+
+
 #endif