[Qemu-devel] [PATCH v4 1/7] qom: introduce ObjectPropertyIterator struct for iteration

[Daniel P. Berrange]

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;
  ObjectProperty *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 <address@hidden>
---
 include/qom/object.h       | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 qom/object.c               | 31 ++++++++++++++++++++++++++++
 tests/check-qom-proplist.c | 46 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 127 insertions(+)

diff --git a/include/qom/object.h b/include/qom/object.h
index be7280c..761ffec 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -960,6 +960,56 @@ void object_property_del(Object *obj, const char *name, 
Error **errp);
 ObjectProperty *object_property_find(Object *obj, const char *name,
                                      Error **errp);
 
+typedef struct ObjectPropertyIterator ObjectPropertyIterator;
+
+/**
+ * object_property_iter_init:
+ * @obj: the object
+ *
+ * Initializes an iterator for traversing all properties
+ * registered against an object instance.
+ *
+ * It is forbidden to modify the property list while iterating,
+ * whether removing or adding properties.
+ *
+ * Typical usage pattern would be
+ *
+ * <example>
+ *   <title>Using object property iterators</title>
+ *   <programlisting>
+ *   ObjectProperty *prop;
+ *   ObjectProperty *iter;
+ *
+ *   iter = object_property_iter_init(obj);
+ *   while ((prop = object_property_iter_next(iter))) {
+ *     ... do something with prop ...
+ *   }
+ *   object_property_iter_free(iter);
+ *   </programlisting>
+ * </example>
+ *
+ * Returns the new iterator
+ */
+ObjectPropertyIterator *object_property_iter_init(Object *obj);
+
+
+/**
+ * object_property_iter_free:
+ * @iter: the iterator instance
+ *
+ * Release any resources associated with the iterator
+ */
+void object_property_iter_free(ObjectPropertyIterator *iter);
+
+/**
+ * object_property_iter_next:
+ * @iter: the iterator instance
+ *
+ * Returns the next property, or NULL when all properties
+ * have been traversed.
+ */
+ObjectProperty *object_property_iter_next(ObjectPropertyIterator *iter);
+
 void object_unparent(Object *obj);
 
 /**
diff --git a/qom/object.c b/qom/object.c
index 4805328..7dace59 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 +921,33 @@ 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);
diff --git a/tests/check-qom-proplist.c b/tests/check-qom-proplist.c
index 7400b1f..1be8b9e 100644
--- a/tests/check-qom-proplist.c
+++ b/tests/check-qom-proplist.c
@@ -283,6 +283,51 @@ static void test_dummy_getenum(void)
                                    &err);
     g_assert(err != NULL);
     error_free(err);
+
+    object_unparent(OBJECT(dobj));
+}
+
+
+static void test_dummy_iterator(void)
+{
+    Object *parent = object_get_objects_root();
+    DummyObject *dobj = DUMMY_OBJECT(
+        object_new_with_props(TYPE_DUMMY,
+                              parent,
+                              "dummy0",
+                              &error_abort,
+                              "bv", "yes",
+                              "sv", "Hiss hiss hiss",
+                              "av", "platypus",
+                              NULL));
+
+    ObjectProperty *prop;
+    ObjectPropertyIterator *iter;
+    bool seenbv = false, seensv = false, seenav = false, seentype;
+
+    iter = object_property_iter_init(OBJECT(dobj));
+    while ((prop = object_property_iter_next(iter))) {
+        if (g_str_equal(prop->name, "bv")) {
+            seenbv = true;
+        } else if (g_str_equal(prop->name, "sv")) {
+            seensv = true;
+        } else if (g_str_equal(prop->name, "av")) {
+            seenav = true;
+        } else if (g_str_equal(prop->name, "type")) {
+            /* This prop comes from the base Object class */
+            seentype = true;
+        } else {
+            g_printerr("Found prop '%s'\n", prop->name);
+            g_assert_not_reached();
+        }
+    }
+    object_property_iter_free(iter);
+    g_assert(seenbv);
+    g_assert(seenav);
+    g_assert(seensv);
+    g_assert(seentype);
+
+    object_unparent(OBJECT(dobj));
 }
 
 
@@ -297,6 +342,7 @@ int main(int argc, char **argv)
     g_test_add_func("/qom/proplist/createv", test_dummy_createv);
     g_test_add_func("/qom/proplist/badenum", test_dummy_badenum);
     g_test_add_func("/qom/proplist/getenum", test_dummy_getenum);
+    g_test_add_func("/qom/proplist/iterator", test_dummy_iterator);
 
     return g_test_run();
 }
-- 
2.4.3