How to make D-Bus server side call as asynchronous ?

[Nitin Jain <nitin e gmail com>]

Hi,

For my project , I am using DBUS as IPC to interact between QT application
( Client Side ) and my service daemon (Server-Side - GIO / GDBUS ). At
client side , methods are invoked asynchronously using
QDBusPendingCallWatcher.

However at server side , how to make method call as async ? . Async call is
required as function invoked,take long time to service request e.g in FM
radio whole band scan.

As per my understanding , "g_dbus_method_invocation_return_value" will
return response with output parameters making method invocation as sync.

One way I can think of is to return intermediate response using
g_dbus_method_invocation_return_value and then once final response is
received emit the final response as signal.

Sample Code :-

//Method invocation

static void handle_method_call(GDBusConnection *conn,

                               const gchar *sender,

                               const gchar *object_path,

                               const gchar *interface_name,

                               const gchar *method_name,

                               GVariant *parameters,

                               GDBusMethodInvocation *invocation,

                               gpointer user_data)

{

if (!g_strcmp0(method_name, "Scan")) {

guint8 radiotype = 0;

guint8temp_resp = 0 ;

g_variant_get(parameters, "(y)", radiotype);

temp_resp = RadioScan(radiotype); // Async Function Call and takes very
long time to return final response as needs to scan whole radio band

g_dbus_method_invocation_return_value(invocation, g_variant_new("(y",
temp_resp)); // return intermediate response to client  and when final
response is received                   //then  emit the signal

g_free(response);

}

}


//Emit the signal once final response is received

static gboolean

on_scanfinalresponse_cb (gpointer user_data)

{

  GDBusConnection *connection = G_DBUS_CONNECTION (user_data);

  GVariantBuilder *builder;

  GVariantBuilder *invalidated_builder;

  GError *error;

  g_dbus_connection_emit_signal (connection,

                                 NULL,

                                 "/org/example/test",

                                 "org.example.test",

                                 "ScanFinalResponse",

                                 g_variant_new ("(s)",

                                  builder),

                                 &error);

  g_assert_no_error (error);

  return TRUE;

}


Please let me know is it right approach or better way to achieve async call
for the above case .