fx: object: add clone() virtual function

fx/include/fx/object.h

@@ -22,6 +22,7 @@ typedef struct _fx_object_class {
 		FX_TYPE_FWDREF(fx_stream) *,
 		const char *);
 	fx_status (*hash)(const struct fx_value *, uint64_t *);
+	fx_status (*clone)(const struct fx_value *, struct fx_value *);
 } fx_object_class;
 
 FX_API fx_type_id fx_object_get_type(void);
@@ -46,6 +47,7 @@ FX_API fx_status fx_object_to_string(
 	const fx_object *p,
 	FX_TYPE_FWDREF(fx_stream) * out,
 	const char *format);
+FX_API fx_status fx_object_clone(const fx_object *src, fx_object **dest);
 FX_API bool fx_object_is_type(const fx_object *p, fx_type_id type);
 
 #endif

fx/object.c

@@ -98,6 +98,23 @@ fx_status fx_object_to_string(
 	return FX_SUCCESS;
 }
 
+fx_status fx_object_clone(const fx_object *src, fx_object **dest)
+{
+	fx_object_class *iface = fx_object_get_interface(src, FX_TYPE_OBJECT);
+	fx_value dest_v = FX_VALUE_EMPTY;
+	if (!iface || !iface->clone) {
+		return FX_ERR_NOT_SUPPORTED;
+	}
+
+	fx_status status = iface->clone(&FX_VALUE_OBJECT(src), &dest_v);
+	if (!FX_OK(status)) {
+		return status;
+	}
+
+	fx_value_get_object(&dest_v, dest);
+	return status;
+}
+
 bool fx_object_is_type(const struct _fx_object *p, fx_type_id type)
 {
 	if (!p) {