[gxml] * add support for detecthing duplicate objects at deserialisation

[Richard Hans Schwarting <rschwart src gnome org>]

commit cf5eda34ef85450ffa75e50e3a8c2ac82b758779
Author: Richard Schwarting <aquarichy gmail com>
Date:   Mon Aug 13 15:50:23 2012 -0400

    * add support for detecthing duplicate objects at deserialisation

 gxml/Serialization.vala |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)
---
diff --git a/gxml/Serialization.vala b/gxml/Serialization.vala
index f8ddf11..79ae485 100644
--- a/gxml/Serialization.vala
+++ b/gxml/Serialization.vala
@@ -192,6 +192,7 @@ namespace GXml {
 				root = doc.create_element ("Object");
 				doc.append_child (root);
 				root.set_attribute ("otype", object.get_type ().name ());
+				root.set_attribute ("oid", "%p".printf (object));
 
 				/* TODO: make sure we don't use an out param for our returned list
 				   size in our interface's list_properties (), using
@@ -318,6 +319,7 @@ namespace GXml {
 			Element obj_elem;
 
 			string otype;
+			string oid;
 			Type type;
 			Object obj;
 			unowned ObjectClass obj_class;
@@ -327,6 +329,15 @@ namespace GXml {
 
 			obj_elem = (Element)node;
 
+			oid = obj_elem.get_attribute ("oid");
+
+			if (Serialization.cache == null) {
+				Serialization.cache = new HashTable<string,Object> (str_hash, str_equal);
+			}
+			if (Serialization.cache.contains (oid)) {
+				return Serialization.cache.get (oid);
+			}
+
 			// Get the object's type
 			// TODO: wish there was a g_object_class_from_name () method
 			otype = obj_elem.get_attribute ("otype");
@@ -339,6 +350,8 @@ namespace GXml {
 			obj = Object.newv (type, new Parameter[] {}); // TODO: causes problems with Enums when 0 isn't a valid enum value (e.g. starts from 2 or something)
 			obj_class = obj.get_class ();
 
+			cache.set (oid, obj);
+
 			if (type.is_a (typeof (Serializable))) {
 				serializable = (Serializable)obj;
 			}