bus: add sd_bus_emit_object_{added/removed}()

This implements two new helpers, discussed on systemd-devel about 1 year
ago:
    sd_bus_emit_object_added()
    sd_bus_emit_object_removed()

Both calls are equivalent to their respective counterpart
sd_bus_emit_interfaces_{added/removed}(), but can figure out the list of
interfaces themselves, instead of requiring the caller to provide them.
Furthermore, both calls properly deal with builtin interfaces provided via
org.freedesktop.DBus.* and alike.

Both calls simply traverse a node and all its parent nodes to figure out a
list of all interfaces registered as vtable or fallback. It then appends
each of them, similar to the interfaces_{added/removed}() helpers.

Note that interfaces_{added/removed}() runs a parent traversal for *each*
passed interface. Therefore, it can simply bail out, once it found a
parent node that implements a given interface.
With object_{added/removed}() we cannot know the registered interfaces in
advance, thus, we cannot run one traversal per node. Instead, we run a
single traversal and remember all interfaces that we added. Therefore, a
child-interface overrides all conflicting parent-interfaces. We keep a
"Set *s" context to track those while climbing up the tree.

1 files changed, 48 insertions, 0 deletions

diff --git a/src/libsystemd/sd-bus/test-bus-objects.c b/src/libsystemd/sd-bus/test-bus-objects.c
index 06b8904f13..acf67a52b3 100644
--- a/src/libsystemd/sd-bus/test-bus-objects.c
+++ b/src/libsystemd/sd-bus/test-bus-objects.c
@@ -176,6 +176,28 @@ static int emit_interfaces_removed(sd_bus *bus, sd_bus_message *m, void *userdat
         return 1;
 }
 
+static int emit_object_added(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
+        int r;
+
+        assert_se(sd_bus_emit_object_added(bus, m->path) >= 0);
+
+        r = sd_bus_reply_method_return(m, NULL);
+        assert_se(r >= 0);
+
+        return 1;
+}
+
+static int emit_object_removed(sd_bus *bus, sd_bus_message *m, void *userdata, sd_bus_error *error) {
+        int r;
+
+        assert_se(sd_bus_emit_object_removed(bus, m->path) >= 0);
+
+        r = sd_bus_reply_method_return(m, NULL);
+        assert_se(r >= 0);
+
+        return 1;
+}
+
 static const sd_bus_vtable vtable[] = {
         SD_BUS_VTABLE_START(0),
         SD_BUS_METHOD("AlterSomething", "s", "s", something_handler, 0),
@@ -186,6 +208,8 @@ static const sd_bus_vtable vtable[] = {
         SD_BUS_METHOD("NoOperation", NULL, NULL, NULL, 0),
         SD_BUS_METHOD("EmitInterfacesAdded", NULL, NULL, emit_interfaces_added, 0),
         SD_BUS_METHOD("EmitInterfacesRemoved", NULL, NULL, emit_interfaces_removed, 0),
+        SD_BUS_METHOD("EmitObjectAdded", NULL, NULL, emit_object_added, 0),
+        SD_BUS_METHOD("EmitObjectRemoved", NULL, NULL, emit_object_removed, 0),
         SD_BUS_VTABLE_END
 };
 
@@ -456,6 +480,30 @@ static int client(struct context *c) {
         sd_bus_message_unref(reply);
         reply = NULL;
 
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitObjectAdded", &error, NULL, "");
+        assert_se(r >= 0);
+
+        r = sd_bus_process(bus, &reply);
+        assert_se(r > 0);
+
+        assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.ObjectManager", "InterfacesAdded"));
+        bus_message_dump(reply, stdout, BUS_MESSAGE_DUMP_WITH_HEADER);
+
+        sd_bus_message_unref(reply);
+        reply = NULL;
+
+        r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "EmitObjectRemoved", &error, NULL, "");
+        assert_se(r >= 0);
+
+        r = sd_bus_process(bus, &reply);
+        assert_se(r > 0);
+
+        assert_se(sd_bus_message_is_signal(reply, "org.freedesktop.DBus.ObjectManager", "InterfacesRemoved"));
+        bus_message_dump(reply, stdout, BUS_MESSAGE_DUMP_WITH_HEADER);
+
+        sd_bus_message_unref(reply);
+        reply = NULL;
+
         r = sd_bus_call_method(bus, "org.freedesktop.systemd.test", "/foo", "org.freedesktop.systemd.test", "Exit", &error, NULL, "");
         assert_se(r >= 0);