qom: Introduce ObjectPropertyIterator struct for iteration

Some users of QOM need to be able to iterate over properties
defined against an object instance. Currently they are just
directly using the QTAIL macros against the object properties
data structure.

This is bad because it exposes them to changes in the data
structure used to store properties, as well as changes in
functionality such as ability to register properties against
the class.

This provides an ObjectPropertyIterator struct which will
insulate the callers from the particular data structure
used to store properties. It can be used thus

  ObjectProperty *prop;
  ObjectPropertyIterator *iter;

  iter = object_property_iter_init(obj);
  while ((prop = object_property_iter_next(iter))) {
      ... do something with prop ...
  }
  object_property_iter_free(iter);

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Tested-by: Pavel Fedin <p.fedin@samsung.com>
[AF: Fixed examples, style cleanups]
Signed-off-by: Andreas Färber <afaerber@suse.de>

1 files changed, 28 insertions, 0 deletions

diff --git a/qom/object.c b/qom/object.c
index c0decb6e96..1c926ceea1 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -67,6 +67,10 @@ struct TypeImpl
     InterfaceImpl interfaces[MAX_INTERFACES];
 };
 
+struct ObjectPropertyIterator {
+    ObjectProperty *next;
+};
+
 static Type type_interface;
 
 static GHashTable *type_table_get(void)
@@ -917,6 +921,30 @@ ObjectProperty *object_property_find(Object *obj, const char *name,
     return NULL;
 }
 
+ObjectPropertyIterator *object_property_iter_init(Object *obj)
+{
+    ObjectPropertyIterator *ret = g_new0(ObjectPropertyIterator, 1);
+    ret->next = QTAILQ_FIRST(&obj->properties);
+    return ret;
+}
+
+void object_property_iter_free(ObjectPropertyIterator *iter)
+{
+    if (!iter) {
+        return;
+    }
+    g_free(iter);
+}
+
+ObjectProperty *object_property_iter_next(ObjectPropertyIterator *iter)
+{
+    ObjectProperty *ret = iter->next;
+    if (ret) {
+        iter->next = QTAILQ_NEXT(iter->next, node);
+    }
+    return ret;
+}
+
 void object_property_del(Object *obj, const char *name, Error **errp)
 {
     ObjectProperty *prop = object_property_find(obj, name, errp);