gobject: Add experimental GBoxed<->JSON transformation

Serializing and deserializing GBoxed types is fairly complicated
currently. If a GObject implements JsonSerializable it is possible
for the class to intercept the JsonNode, parse it manually and
then set the value to the property.

This leaves a hole opened for:

  • manual (de)serialization of GBoxed types
  • (de)serialization of GBoxed properties in classes not
    implementing JsonSerializable

In order to serialize and deserialize a GBoxed JSON-GLib should
provide a mechanism similar to the GValue transformation functions:
when registering the boxed type the developer should also be able
to register a serialization and a deserialization functions pair
matching the tuple:

  (GBoxed type, JSON type)

The serialization function would be:

  JsonNode *(* JsonBoxedSerializeFunc) (gconstpointer boxed);

And, conversely, the deserialization function would be:

  gpointer (* JsonBoxedDeserializeFunc) (JsonNode *node);

Obviously, the whole machinery works only for GBoxed types that
register the serialization and deserialization functions.

1 files changed, 37 insertions, 0 deletions

diff --git a/json-glib/json-gobject.h b/json-glib/json-gobject.h
index 8eacc58..207db52 100644
--- a/json-glib/json-gobject.h
+++ b/json-glib/json-gobject.h
@@ -79,6 +79,43 @@ gboolean  json_serializable_deserialize_property (JsonSerializable *serializable
                                                   GParamSpec       *pspec,
                                                   JsonNode         *property_node);
 
+/**
+ * JsonBoxedSerializeFunc:
+ * @boxed: a #GBoxed
+ *
+ * Serializes the passed #GBoxed and stores it inside a #JsonNode
+ *
+ * Return value: the newly created #JsonNode
+ *
+ * Since: 0.10
+ */
+typedef JsonNode *(* JsonBoxedSerializeFunc) (gconstpointer boxed);
+
+/**
+ * JsonBoxedDeserializeFunc:
+ * @node: a #JsonNode
+ *
+ * Deserializes the contents of the passed #JsonNode into a #GBoxed
+ *
+ * Return value: the newly created boxed type
+ *
+ * Since: 0.10
+ */
+typedef gpointer (* JsonBoxedDeserializeFunc) (JsonNode *node);
+
+void      json_boxed_register_transform_func (GType                     gboxed_type,
+                                              JsonNodeType              node_type,
+                                              JsonBoxedSerializeFunc    serialize_func,
+                                              JsonBoxedDeserializeFunc  deserialize_func);
+gboolean  json_boxed_can_serialize           (GType                     gboxed_type,
+                                              JsonNodeType             *node_type);
+gboolean  json_boxed_can_deserialize         (GType                     gboxed_type,
+                                              JsonNodeType              node_type);
+JsonNode *json_boxed_serialize               (GType                     gboxed_type,
+                                              JsonNodeType              node_type,
+                                              gconstpointer             boxed);
+gpointer  json_boxed_deserialize             (GType                     gboxed_type,
+                                              JsonNode                 *node);
 
 GObject *json_construct_gobject (GType         gtype,
                                  const gchar  *data,