dbus: more efficient implementation of properties

The way the various properties[] arrays are initialized is inefficient:
 - only the .data members change at runtime, yet the whole arrays of
   properties with all the fields are constructed on the stack one by
   one by the code.
 - there's duplication, eg. the properties of "org.freedesktop.systemd1.Unit"
   are repeated in several unit types.

Fix it by moving the information about properties into static const
sections. Instead of storing the .data directly in the property, store
a constant offset from a run-time base.
The small arrays of struct BusBoundProperties bind together the constant
information with the right runtime information (the base pointer).

On my system the code shrinks by 60 KB, data increases by 10 KB.

1 files changed, 21 insertions, 16 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index efbc040ad3..42dd54dc35 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -706,6 +706,20 @@ static int flush_devices(Manager *m) {
         return trigger_device(m, NULL);
 }
 
+static const BusProperty bus_login_manager_properties[] = {
+        { "ControlGroupHierarchy",  bus_property_append_string,         "s",  offsetof(Manager, cgroup_path),        true },
+        { "Controllers",            bus_property_append_strv,           "as", offsetof(Manager, controllers),        true },
+        { "ResetControllers",       bus_property_append_strv,           "as", offsetof(Manager, reset_controllers),  true },
+        { "NAutoVTs",               bus_property_append_unsigned,       "u",  offsetof(Manager, n_autovts)           },
+        { "KillOnlyUsers",          bus_property_append_strv,           "as", offsetof(Manager, kill_only_users),    true },
+        { "KillExcludeUsers",       bus_property_append_strv,           "as", offsetof(Manager, kill_exclude_users), true },
+        { "KillUserProcesses",      bus_property_append_bool,           "b",  offsetof(Manager, kill_user_processes) },
+        { "IdleHint",               bus_manager_append_idle_hint,       "b",  0 },
+        { "IdleSinceHint",          bus_manager_append_idle_hint_since, "t",  0 },
+        { "IdleSinceHintMonotonic", bus_manager_append_idle_hint_since, "t",  0 },
+        { NULL, }
+};
+
 static DBusHandlerResult manager_message_handler(
                 DBusConnection *connection,
                 DBusMessage *message,
@@ -713,20 +727,6 @@ static DBusHandlerResult manager_message_handler(
 
         Manager *m = userdata;
 
-        const BusProperty properties[] = {
-                { "org.freedesktop.login1.Manager", "ControlGroupHierarchy",  bus_property_append_string,   "s",  m->cgroup_path          },
-                { "org.freedesktop.login1.Manager", "Controllers",            bus_property_append_strv,     "as", m->controllers          },
-                { "org.freedesktop.login1.Manager", "ResetControllers",       bus_property_append_strv,     "as", m->reset_controllers    },
-                { "org.freedesktop.login1.Manager", "NAutoVTs",               bus_property_append_unsigned, "u",  &m->n_autovts           },
-                { "org.freedesktop.login1.Manager", "KillOnlyUsers",          bus_property_append_strv,     "as", m->kill_only_users      },
-                { "org.freedesktop.login1.Manager", "KillExcludeUsers",       bus_property_append_strv,     "as", m->kill_exclude_users   },
-                { "org.freedesktop.login1.Manager", "KillUserProcesses",      bus_property_append_bool,     "b",  &m->kill_user_processes },
-                { "org.freedesktop.login1.Manager", "IdleHint",               bus_manager_append_idle_hint, "b",  m                       },
-                { "org.freedesktop.login1.Manager", "IdleSinceHint",          bus_manager_append_idle_hint_since, "t", m                  },
-                { "org.freedesktop.login1.Manager", "IdleSinceHintMonotonic", bus_manager_append_idle_hint_since, "t", m                  },
-                { NULL, NULL, NULL, NULL, NULL }
-        };
-
         DBusError error;
         DBusMessage *reply = NULL;
         int r;
@@ -1426,8 +1426,13 @@ static DBusHandlerResult manager_message_handler(
                 }
 
                 free(introspection);
-        } else
-                return bus_default_message_handler(connection, message, NULL, INTERFACES_LIST, properties);
+        } else {
+                const BusBoundProperties bps[] = {
+                        { "org.freedesktop.login1.Manager", bus_login_manager_properties, m },
+                        { NULL, }
+                };
+                return bus_default_message_handler(connection, message, NULL, INTERFACES_LIST, bps);
+        }
 
         if (reply) {
                 if (!dbus_connection_send(connection, reply, NULL))