add ability to call interface methods with return value

include/class.h

@@ -40,8 +40,7 @@
  * @TODO: actually i use gcc feature ## for variadoc... think about
  * a way to make this standard.
  */
-#define CALL(object,_iface,method,...)                                            \
-	do {                                                                          \
+#define _CALL(object,_iface,method,...)                                       \
 	class_ptr           class = class_getClass((object));                     \
 	struct i_##_iface * iface;                                                \
 	if (class->init)	class->init();                                        \
@@ -51,10 +50,20 @@
 		if (class->init)	class->init();                                    \
 		iface = (struct i_##_iface *)class_getInterface(&class, &i_##_iface); \
 	};                                                                        \
-		assert(NULL != iface->method);                                            \
+	assert(NULL != iface->method);
+
+#define CALL(object,_iface,method,...)               \
+	do {                                             \
+		_CALL(object, _iface, method, ##__VA_ARGS__); \
 		iface->method(object, ##__VA_ARGS__);        \
 	} while(0)
 
+#define RETCALL(object,_iface,method,ret,...)        \
+	do {                                             \
+		_CALL(object, _iface, method, ##__VA_ARGS__); \
+		ret = iface->method(object, ##__VA_ARGS__);  \
+	} while(0)
+
 
 #define IFACE_GET(class,iface)		(interfaceGet(&((class)->impl),(iface)))
 #define IFACE_EXISTS(class,iface)	(NULL != IFACE_GET((class),(iface)))