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, 14 insertions, 8 deletions

diff --git a/src/hostname/hostnamed.c b/src/hostname/hostnamed.c
index f3b2c94173..1340c29dd5 100644
--- a/src/hostname/hostnamed.c
+++ b/src/hostname/hostnamed.c
@@ -280,18 +280,24 @@ static int bus_hostname_append_icon_name(DBusMessageIter *i, const char *propert
         return bus_property_append_string(i, property, (void*) name);
 }
 
+static const BusProperty bus_hostname_properties[] = {
+        { "Hostname",       bus_property_append_string,    "s", sizeof(data[0])*PROP_HOSTNAME,        true },
+        { "StaticHostname", bus_property_append_string,    "s", sizeof(data[0])*PROP_STATIC_HOSTNAME, true },
+        { "PrettyHostname", bus_property_append_string,    "s", sizeof(data[0])*PROP_PRETTY_HOSTNAME, true },
+        { "IconName",       bus_hostname_append_icon_name, "s", sizeof(data[0])*PROP_ICON_NAME,       true },
+        { NULL, }
+};
+
+static const BusBoundProperties bps[] = {
+        { "org.freedesktop.hostname1", bus_hostname_properties, data },
+        { NULL, }
+};
+
 static DBusHandlerResult hostname_message_handler(
                 DBusConnection *connection,
                 DBusMessage *message,
                 void *userdata) {
 
-        const BusProperty properties[] = {
-                { "org.freedesktop.hostname1", "Hostname",       bus_property_append_string,    "s", data[PROP_HOSTNAME]},
-                { "org.freedesktop.hostname1", "StaticHostname", bus_property_append_string,    "s", data[PROP_STATIC_HOSTNAME]},
-                { "org.freedesktop.hostname1", "PrettyHostname", bus_property_append_string,    "s", data[PROP_PRETTY_HOSTNAME]},
-                { "org.freedesktop.hostname1", "IconName",       bus_hostname_append_icon_name, "s", data[PROP_ICON_NAME]},
-                { NULL, NULL, NULL, NULL, NULL }
-        };
 
         DBusMessage *reply = NULL, *changed = NULL;
         DBusError error;
@@ -470,7 +476,7 @@ static DBusHandlerResult hostname_message_handler(
                 }
 
         } else
-                return bus_default_message_handler(connection, message, INTROSPECTION, INTERFACES_LIST, properties);
+                return bus_default_message_handler(connection, message, INTROSPECTION, INTERFACES_LIST, bps);
 
         if (!(reply = dbus_message_new_method_return(message)))
                 goto oom;