Owning Bus Names

Owning Bus Names — Simple API for owning bus names

Synopsis

#include <gio/gio.h>

void                (*GBusAcquiredCallback)             (GDBusConnection *connection,
                                                         const gchar *name,
                                                         gpointer user_data);
void                (*GBusNameAcquiredCallback)         (GDBusConnection *connection,
                                                         const gchar *name,
                                                         gpointer user_data);
void                (*GBusNameLostCallback)             (GDBusConnection *connection,
                                                         const gchar *name,
                                                         gpointer user_data);
enum                GBusNameOwnerFlags;
guint               g_bus_own_name                      (GBusType bus_type,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GBusAcquiredCallback bus_acquired_handler,
                                                         GBusNameAcquiredCallback name_acquired_handler,
                                                         GBusNameLostCallback name_lost_handler,
                                                         gpointer user_data,
                                                         GDestroyNotify user_data_free_func);
guint               g_bus_own_name_on_connection        (GDBusConnection *connection,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GBusNameAcquiredCallback name_acquired_handler,
                                                         GBusNameLostCallback name_lost_handler,
                                                         gpointer user_data,
                                                         GDestroyNotify user_data_free_func);
void                g_bus_unown_name                    (guint owner_id);
guint               g_bus_own_name_with_closures        (GBusType bus_type,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GClosure *bus_acquired_closure,
                                                         GClosure *name_acquired_closure,
                                                         GClosure *name_lost_closure);
guint               g_bus_own_name_on_connection_with_closures
                                                        (GDBusConnection *connection,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GClosure *name_acquired_closure,
                                                         GClosure *name_lost_closure);

Description

Convenience API for owning bus names.

Example 8. Simple application owning a name

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#include <gio/gio.h>

static void
on_bus_acquired (GDBusConnection *connection,
                 const gchar     *name,
                 gpointer         user_data)
{
  /* This is where we'd export some objects on the bus */
}

static void
on_name_acquired (GDBusConnection *connection,
                  const gchar     *name,
                  gpointer         user_data)
{
  g_print ("Acquired the name %s on the session bus\n", name);
}

static void
on_name_lost (GDBusConnection *connection,
              const gchar     *name,
              gpointer         user_data)
{
  g_print ("Lost the name %s on the session bus\n", name);
}

int
main (int argc, char *argv[])
{
  guint owner_id;
  GMainLoop *loop;
  GBusNameOwnerFlags flags;
  gboolean opt_replace;
  gboolean opt_allow_replacement;
  gchar *opt_name;
  GOptionContext *opt_context;
  GError *error;
  GOptionEntry opt_entries[] =
    {
      { "replace", 'r', 0, G_OPTION_ARG_NONE, &opt_replace, "Replace existing name if possible", NULL },
      { "allow-replacement", 'a', 0, G_OPTION_ARG_NONE, &opt_allow_replacement, "Allow replacement", NULL },
      { "name", 'n', 0, G_OPTION_ARG_STRING, &opt_name, "Name to acquire", NULL },
      { NULL}
    };

  g_type_init ();

  error = NULL;
  opt_name = NULL;
  opt_replace = FALSE;
  opt_allow_replacement = FALSE;
  opt_context = g_option_context_new ("g_bus_own_name() example");
  g_option_context_add_main_entries (opt_context, opt_entries, NULL);
  if (!g_option_context_parse (opt_context, &argc, &argv, &error))
    {
      g_printerr ("Error parsing options: %s", error->message);
      return 1;
    }
  if (opt_name == NULL)
    {
      g_printerr ("Incorrect usage, try --help.\n");
      return 1;
    }

  flags = G_BUS_NAME_OWNER_FLAGS_NONE;
  if (opt_replace)
    flags |= G_BUS_NAME_OWNER_FLAGS_REPLACE;
  if (opt_allow_replacement)
    flags |= G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT;

  owner_id = g_bus_own_name (G_BUS_TYPE_SESSION,
                             opt_name,
                             flags,
                             on_bus_acquired,
                             on_name_acquired,
                             on_name_lost,
                             NULL,
                             NULL);

  loop = g_main_loop_new (NULL, FALSE);
  g_main_loop_run (loop);

  g_bus_unown_name (owner_id);

  return 0;
}


Details

GBusAcquiredCallback ()

void                (*GBusAcquiredCallback)             (GDBusConnection *connection,
                                                         const gchar *name,
                                                         gpointer user_data);

Invoked when a connection to a message bus has been obtained.

connection :

The GDBusConnection to a message bus.

name :

The name that is requested to be owned.

user_data :

User data passed to g_bus_own_name().

Since 2.26


GBusNameAcquiredCallback ()

void                (*GBusNameAcquiredCallback)         (GDBusConnection *connection,
                                                         const gchar *name,
                                                         gpointer user_data);

Invoked when the name is acquired.

connection :

The GDBusConnection on which to acquired the name.

name :

The name being owned.

user_data :

User data passed to g_bus_own_name() or g_bus_own_name_on_connection().

Since 2.26


GBusNameLostCallback ()

void                (*GBusNameLostCallback)             (GDBusConnection *connection,
                                                         const gchar *name,
                                                         gpointer user_data);

Invoked when the name is lost or connection has been closed.

connection :

The GDBusConnection on which to acquire the name or NULL if the connection was disconnected.

name :

The name being owned.

user_data :

User data passed to g_bus_own_name() or g_bus_own_name_on_connection().

Since 2.26


enum GBusNameOwnerFlags

typedef enum {
  G_BUS_NAME_OWNER_FLAGS_NONE = 0,                    /*< nick=none >*/
  G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT = (1<<0),  /*< nick=allow-replacement >*/
  G_BUS_NAME_OWNER_FLAGS_REPLACE = (1<<1)            /*< nick=replace >*/
} GBusNameOwnerFlags;

Flags used in g_bus_own_name().

G_BUS_NAME_OWNER_FLAGS_NONE

No flags set.

G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT

Allow another message bus connection to claim the the name.

G_BUS_NAME_OWNER_FLAGS_REPLACE

If another message bus connection owns the name and have specified G_BUS_NAME_OWNER_FLAGS_ALLOW_REPLACEMENT, then take the name from the other connection.

Since 2.26


g_bus_own_name ()

guint               g_bus_own_name                      (GBusType bus_type,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GBusAcquiredCallback bus_acquired_handler,
                                                         GBusNameAcquiredCallback name_acquired_handler,
                                                         GBusNameLostCallback name_lost_handler,
                                                         gpointer user_data,
                                                         GDestroyNotify user_data_free_func);

Starts acquiring name on the bus specified by bus_type and calls name_acquired_handler and name_lost_handler when the name is acquired respectively lost. Callbacks will be invoked in the thread-default main loop of the thread you are calling this function from.

You are guaranteed that one of the name_acquired_handler and name_lost_handler callbacks will be invoked after calling this function - there are three possible cases:

  • name_lost_handler with a NULL connection (if a connection to the bus can't be made).

  • bus_acquired_handler then name_lost_handler (if the name can't be obtained)

  • bus_acquired_handler then name_acquired_handler (if the name was obtained).

When you are done owning the name, just call g_bus_unown_name() with the owner id this function returns.

If the name is acquired or lost (for example another application could acquire the name if you allow replacement or the application currently owning the name exits), the handlers are also invoked. If the GDBusConnection that is used for attempting to own the name closes, then name_lost_handler is invoked since it is no longer possible for other processes to access the process.

You cannot use g_bus_own_name() several times for the same name (unless interleaved with calls to g_bus_unown_name()) - only the first call will work.

Another guarantee is that invocations of name_acquired_handler and name_lost_handler are guaranteed to alternate; that is, if name_acquired_handler is invoked then you are guaranteed that the next time one of the handlers is invoked, it will be name_lost_handler. The reverse is also true.

If you plan on exporting objects (using e.g. g_dbus_connection_register_object()), note that it is generally too late to export the objects in name_acquired_handler. Instead, you can do this in bus_acquired_handler since you are guaranteed that this will run before name is requested from the bus.

This behavior makes it very simple to write applications that wants to own names and export objects, see Example 8, “Simple application owning a name”. Simply register objects to be exported in bus_acquired_handler and unregister the objects (if any) in name_lost_handler.

bus_type :

The type of bus to own a name on.

name :

The well-known name to own.

flags :

A set of flags from the GBusNameOwnerFlags enumeration.

bus_acquired_handler :

Handler to invoke when connected to the bus of type bus_type or NULL. [allow-none]

name_acquired_handler :

Handler to invoke when name is acquired or NULL. [allow-none]

name_lost_handler :

Handler to invoke when name is lost or NULL. [allow-none]

user_data :

User data to pass to handlers.

user_data_free_func :

Function for freeing user_data or NULL. [allow-none]

Returns :

An identifier (never 0) that an be used with g_bus_unown_name() to stop owning the name.

Since 2.26


g_bus_own_name_on_connection ()

guint               g_bus_own_name_on_connection        (GDBusConnection *connection,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GBusNameAcquiredCallback name_acquired_handler,
                                                         GBusNameLostCallback name_lost_handler,
                                                         gpointer user_data,
                                                         GDestroyNotify user_data_free_func);

Like g_bus_own_name() but takes a GDBusConnection instead of a GBusType.

connection :

A GDBusConnection.

name :

The well-known name to own.

flags :

A set of flags from the GBusNameOwnerFlags enumeration.

name_acquired_handler :

Handler to invoke when name is acquired or NULL. [allow-none]

name_lost_handler :

Handler to invoke when name is lost or NULL. [allow-none]

user_data :

User data to pass to handlers.

user_data_free_func :

Function for freeing user_data or NULL. [allow-none]

Returns :

An identifier (never 0) that an be used with g_bus_unown_name() to stop owning the name.

Since 2.26


g_bus_unown_name ()

void                g_bus_unown_name                    (guint owner_id);

Stops owning a name.

owner_id :

An identifier obtained from g_bus_own_name()

Since 2.26


g_bus_own_name_with_closures ()

guint               g_bus_own_name_with_closures        (GBusType bus_type,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GClosure *bus_acquired_closure,
                                                         GClosure *name_acquired_closure,
                                                         GClosure *name_lost_closure);

Version of g_bus_own_name() using closures instead of callbacks for easier binding in other languages.

bus_type :

The type of bus to own a name on.

name :

The well-known name to own.

flags :

A set of flags from the GBusNameOwnerFlags enumeration.

bus_acquired_closure :

GClosure to invoke when connected to the bus of type bus_type or NULL. [allow-none]

name_acquired_closure :

GClosure to invoke when name is acquired or NULL. [allow-none]

name_lost_closure :

GClosure to invoke when name is lost or NULL. [allow-none]

Returns :

An identifier (never 0) that an be used with g_bus_unown_name() to stop owning the name. Rename to: g_bus_own_name

Since 2.26


g_bus_own_name_on_connection_with_closures ()

guint               g_bus_own_name_on_connection_with_closures
                                                        (GDBusConnection *connection,
                                                         const gchar *name,
                                                         GBusNameOwnerFlags flags,
                                                         GClosure *name_acquired_closure,
                                                         GClosure *name_lost_closure);

Version of g_bus_own_name_on_connection() using closures instead of callbacks for easier binding in other languages.

connection :

A GDBusConnection.

name :

The well-known name to own.

flags :

A set of flags from the GBusNameOwnerFlags enumeration.

name_acquired_closure :

GClosure to invoke when name is acquired or NULL. [allow-none]

name_lost_closure :

GClosure to invoke when name is lost or NULL. [allow-none]

Returns :

An identifier (never 0) that an be used with g_bus_unown_name() to stop owning the name. Rename to: g_bus_own_name_on_connection

Since 2.26