[PATCH v2 3/5] qom: object_child_foreach_recursive_type()

[Peter Xu <peterx@redhat.com>]

Add this sister helper besides object_child_foreach_recursive() to loop over
child objects only if the object can be casted to a specific type.

Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 include/qom/object.h | 20 ++++++++++++++++++++
 qom/object.c         | 27 +++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/include/qom/object.h b/include/qom/object.h
index faae0d841f..355277db40 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1926,6 +1926,26 @@ int object_child_foreach(Object *obj, int (*fn)(Object *child, void *opaque),
 int object_child_foreach_recursive(Object *obj,
                                    int (*fn)(Object *child, void *opaque),
                                    void *opaque);
+
+/**
+ * object_child_foreach_recursive_type:
+ * @obj: the object whose children will be navigated
+ * @type: the typename string to scan
+ * @fn: the iterator function to be called
+ * @opaque: an opaque value that will be passed to the iterator
+ *
+ * This is a special version of object_child_foreach_recursive() so that we
+ * only call the fn() if the child can be casted to the @typename specified.
+ * Please refer to the comments above object_child_foreach_recursive() for
+ * more details.
+ *
+ * Returns: The last value returned by @fn, or 0 if there is no child.
+ */
+int object_child_foreach_recursive_type(Object *obj,
+                                        const char *typename,
+                                        int (*fn)(Object *child, void *opaque),
+                                        void *opaque);
+
 /**
  * container_get:
  * @root: root of the #path, e.g., object_get_root()
diff --git a/qom/object.c b/qom/object.c
index 6be710bc40..d25ca09b1d 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1134,6 +1134,33 @@ int object_child_foreach_recursive(Object *obj,
     return do_object_child_foreach(obj, fn, opaque, true);
 }
 
+typedef struct {
+    const char *typename;
+    int (*fn)(Object *child, void *opaque);
+    void *opaque;
+} ObjectTypeArgs;
+
+static int object_child_hook(Object *child, void *opaque)
+{
+    ObjectTypeArgs *args = opaque;
+
+    if (object_dynamic_cast(child, args->typename)) {
+        return args->fn(child, args->opaque);
+    }
+
+    return 0;
+}
+
+int object_child_foreach_recursive_type(Object *obj,
+                                        const char *typename,
+                                        int (*fn)(Object *child, void *opaque),
+                                        void *opaque)
+{
+    ObjectTypeArgs args = { .typename = typename, .fn = fn, .opaque = opaque };
+
+    return object_child_foreach_recursive(obj, object_child_hook, &args);
+}
+
 static void object_class_get_list_tramp(ObjectClass *klass, void *opaque)
 {
     GSList **list = opaque;
-- 
2.32.0