2 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
4 * gstbus.c: GstBus subsystem
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
19 * Boston, MA 02110-1301, USA.
25 * @short_description: Asynchronous message bus subsystem
26 * @see_also: #GstMessage, #GstElement
28 * The #GstBus is an object responsible for delivering #GstMessage packets in
29 * a first-in first-out way from the streaming threads (see #GstTask) to the
32 * Since the application typically only wants to deal with delivery of these
33 * messages from one thread, the GstBus will marshall the messages between
34 * different threads. This is important since the actual streaming of media
35 * is done in another thread than the application.
37 * The GstBus provides support for #GSource based notifications. This makes it
38 * possible to handle the delivery in the glib #GMainLoop.
40 * The #GSource callback function gst_bus_async_signal_func() can be used to
41 * convert all bus messages into signal emissions.
43 * A message is posted on the bus with the gst_bus_post() method. With the
44 * gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a
45 * previously posted message.
47 * The bus can be polled with the gst_bus_poll() method. This methods blocks
48 * up to the specified timeout value until one of the specified messages types
49 * is posted on the bus. The application can then gst_bus_pop() the messages
50 * from the bus to handle them.
51 * Alternatively the application can register an asynchronous bus function
52 * using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will
53 * install a #GSource in the default glib main loop and will deliver messages
54 * a short while after they have been posted. Note that the main loop should
55 * be running for the asynchronous callbacks.
57 * It is also possible to get messages from the bus without any thread
58 * marshalling with the gst_bus_set_sync_handler() method. This makes it
59 * possible to react to a message in the same thread that posted the
60 * message on the bus. This should only be used if the application is able
61 * to deal with messages from different threads.
63 * Every #GstPipeline has one bus.
65 * Note that a #GstPipeline will set its bus into flushing state when changing
66 * from READY to NULL state.
69 #include "gst_private.h"
74 #include <sys/types.h>
76 #include "gstatomicqueue.h"
81 #include "glib-compat-private.h"
85 # define EWOULDBLOCK EAGAIN /* This is just to placate gcc */
87 #endif /* G_OS_WIN32 */
89 #define GST_CAT_DEFAULT GST_CAT_BUS
99 #define DEFAULT_ENABLE_ASYNC (TRUE)
107 static void gst_bus_dispose (GObject * object);
108 static void gst_bus_finalize (GObject * object);
110 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
114 GstBusSyncHandler handler;
116 GDestroyNotify destroy_notify;
121 sync_handler_ref (SyncHandler * handler)
123 g_atomic_int_inc (&handler->ref_count);
129 sync_handler_unref (SyncHandler * handler)
131 if (!g_atomic_int_dec_and_test (&handler->ref_count))
134 if (handler->destroy_notify)
135 handler->destroy_notify (handler->user_data);
140 struct _GstBusPrivate
142 GstAtomicQueue *queue;
145 SyncHandler *sync_handler;
147 guint num_signal_watchers;
149 guint num_sync_message_emitters;
152 gboolean enable_async;
157 #define gst_bus_parent_class parent_class
158 G_DEFINE_TYPE_WITH_PRIVATE (GstBus, gst_bus, GST_TYPE_OBJECT);
161 gst_bus_set_property (GObject * object,
162 guint prop_id, const GValue * value, GParamSpec * pspec)
164 GstBus *bus = GST_BUS_CAST (object);
167 case PROP_ENABLE_ASYNC:
168 bus->priv->enable_async = g_value_get_boolean (value);
171 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
177 gst_bus_constructed (GObject * object)
179 GstBus *bus = GST_BUS_CAST (object);
181 if (bus->priv->enable_async) {
182 bus->priv->poll = gst_poll_new_timer ();
183 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
186 G_OBJECT_CLASS (gst_bus_parent_class)->constructed (object);
190 gst_bus_class_init (GstBusClass * klass)
192 GObjectClass *gobject_class = (GObjectClass *) klass;
194 gobject_class->dispose = gst_bus_dispose;
195 gobject_class->finalize = gst_bus_finalize;
196 gobject_class->set_property = gst_bus_set_property;
197 gobject_class->constructed = gst_bus_constructed;
200 * GstBus:enable-async:
202 * Enables async message delivery support for bus watches,
203 * gst_bus_pop() and similar API. Without this only the
204 * synchronous message handlers are called.
206 * This property is used to create the child element buses
209 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
210 g_param_spec_boolean ("enable-async", "Enable Async",
211 "Enable async message delivery for bus watches and gst_bus_pop()",
212 DEFAULT_ENABLE_ASYNC,
213 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
216 * GstBus::sync-message:
217 * @self: the object which received the signal
218 * @message: the message that has been posted synchronously
220 * A message has been posted on the bus. This signal is emitted from the
221 * thread that posted the message so one has to be careful with locking.
223 * This signal will not be emitted by default, you have to call
224 * gst_bus_enable_sync_message_emission() before.
226 gst_bus_signals[SYNC_MESSAGE] =
227 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
228 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
229 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
230 NULL, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
234 * @self: the object which received the signal
235 * @message: the message that has been posted asynchronously
237 * A message has been posted on the bus. This signal is emitted from a
238 * #GSource added to the mainloop. this signal will only be emitted when
239 * there is a #GMainLoop running.
241 gst_bus_signals[ASYNC_MESSAGE] =
242 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
243 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
244 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
245 NULL, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
249 gst_bus_init (GstBus * bus)
251 bus->priv = gst_bus_get_instance_private (bus);
252 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
253 g_mutex_init (&bus->priv->queue_lock);
254 bus->priv->queue = gst_atomic_queue_new (32);
256 GST_DEBUG_OBJECT (bus, "created");
260 gst_bus_dispose (GObject * object)
262 GstBus *bus = GST_BUS (object);
264 if (bus->priv->queue) {
267 g_mutex_lock (&bus->priv->queue_lock);
269 message = gst_atomic_queue_pop (bus->priv->queue);
271 gst_message_unref (message);
272 } while (message != NULL);
273 gst_atomic_queue_unref (bus->priv->queue);
274 bus->priv->queue = NULL;
275 g_mutex_unlock (&bus->priv->queue_lock);
276 g_mutex_clear (&bus->priv->queue_lock);
279 gst_poll_free (bus->priv->poll);
280 bus->priv->poll = NULL;
283 G_OBJECT_CLASS (parent_class)->dispose (object);
287 gst_bus_finalize (GObject * object)
289 GstBus *bus = GST_BUS (object);
291 if (bus->priv->sync_handler)
292 sync_handler_unref (g_steal_pointer (&bus->priv->sync_handler));
294 G_OBJECT_CLASS (parent_class)->finalize (object);
300 * Creates a new #GstBus instance.
302 * Returns: (transfer full): a new #GstBus instance
309 result = g_object_new (gst_bus_get_type (), NULL);
310 GST_DEBUG_OBJECT (result, "created new bus");
312 /* clear floating flag */
313 gst_object_ref_sink (result);
320 * @bus: a #GstBus to post on
321 * @message: (transfer full): the #GstMessage to post
323 * Posts a message on the given bus. Ownership of the message
324 * is taken by the bus.
326 * Returns: %TRUE if the message could be posted, %FALSE if the bus is flushing.
329 gst_bus_post (GstBus * bus, GstMessage * message)
331 GstBusSyncReply reply = GST_BUS_PASS;
332 gboolean emit_sync_message;
333 SyncHandler *sync_handler = NULL;
335 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
336 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
338 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
341 /* check we didn't accidentally add a public flag that maps to same value */
342 g_assert (!GST_MINI_OBJECT_FLAG_IS_SET (message,
343 GST_MESSAGE_FLAG_ASYNC_DELIVERY));
345 GST_OBJECT_LOCK (bus);
346 /* check if the bus is flushing */
347 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
350 if (bus->priv->sync_handler)
351 sync_handler = sync_handler_ref (bus->priv->sync_handler);
352 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
353 GST_OBJECT_UNLOCK (bus);
355 /* first call the sync handler if it is installed */
357 reply = sync_handler->handler (bus, message, sync_handler->user_data);
359 /* emit sync-message if requested to do so via
360 gst_bus_enable_sync_message_emission. terrible but effective */
361 if (emit_sync_message && reply != GST_BUS_DROP
363 || sync_handler->handler != gst_bus_sync_signal_handler))
364 gst_bus_sync_signal_handler (bus, message, NULL);
366 g_clear_pointer (&sync_handler, sync_handler_unref);
368 /* If this is a bus without async message delivery
369 * always drop the message */
370 if (!bus->priv->poll)
371 reply = GST_BUS_DROP;
373 /* now see what we should do with the message */
376 /* drop the message */
377 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
380 /* pass the message to the async queue, refcount passed in the queue */
381 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
382 gst_atomic_queue_push (bus->priv->queue, message);
383 gst_poll_write_control (bus->priv->poll);
384 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
389 /* async delivery, we need a mutex and a cond to block
391 GCond *cond = GST_MESSAGE_GET_COND (message);
392 GMutex *lock = GST_MESSAGE_GET_LOCK (message);
397 GST_MINI_OBJECT_FLAG_SET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
399 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
401 /* now we lock the message mutex, send the message to the async
402 * queue. When the message is handled by the app and destroyed,
403 * the cond will be signalled and we can continue */
406 gst_atomic_queue_push (bus->priv->queue, message);
407 gst_poll_write_control (bus->priv->poll);
409 /* now block till the message is freed */
410 g_cond_wait (cond, lock);
412 /* we acquired a new ref from gst_message_dispose() so we can clean up */
413 g_mutex_unlock (lock);
415 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
417 GST_MINI_OBJECT_FLAG_UNSET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
419 g_mutex_clear (lock);
422 gst_message_unref (message);
426 g_warning ("invalid return from bus sync handler");
434 GST_DEBUG_OBJECT (bus, "bus is flushing");
435 GST_OBJECT_UNLOCK (bus);
436 gst_message_unref (message);
443 * gst_bus_have_pending:
444 * @bus: a #GstBus to check
446 * Checks if there are pending messages on the bus that
449 * Returns: %TRUE if there are messages on the bus to be handled, %FALSE
453 gst_bus_have_pending (GstBus * bus)
457 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
459 /* see if there is a message on the bus */
460 result = gst_atomic_queue_length (bus->priv->queue) != 0;
466 * gst_bus_set_flushing:
468 * @flushing: whether or not to flush the bus
470 * If @flushing, flushes out and unrefs any messages queued in the bus. Releases
471 * references to the message origin objects. Will flush future messages until
472 * gst_bus_set_flushing() sets @flushing to %FALSE.
475 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
478 GList *message_list = NULL;
480 g_return_if_fail (GST_IS_BUS (bus));
482 GST_OBJECT_LOCK (bus);
485 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
487 GST_DEBUG_OBJECT (bus, "set bus flushing");
489 while ((message = gst_bus_pop (bus)))
490 message_list = g_list_prepend (message_list, message);
492 GST_DEBUG_OBJECT (bus, "unset bus flushing");
493 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
496 GST_OBJECT_UNLOCK (bus);
498 g_list_free_full (message_list, (GDestroyNotify) gst_message_unref);
502 * gst_bus_timed_pop_filtered:
503 * @bus: a #GstBus to pop from
504 * @timeout: a timeout in nanoseconds, or %GST_CLOCK_TIME_NONE to wait forever
505 * @types: message types to take into account, %GST_MESSAGE_ANY for any type
507 * Gets a message from the bus whose type matches the message type mask @types,
508 * waiting up to the specified timeout (and discarding any messages that do not
509 * match the mask provided).
511 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
512 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
513 * matching message was posted on the bus.
515 * Returns: (transfer full) (nullable): a #GstMessage matching the
516 * filter in @types, or %NULL if no matching message was found on
517 * the bus until the timeout expired.
520 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
521 GstMessageType types)
525 gboolean first_round = TRUE;
526 GstClockTime elapsed = 0;
528 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
529 g_return_val_if_fail (types != 0, NULL);
530 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
532 g_mutex_lock (&bus->priv->queue_lock);
537 GST_LOG_OBJECT (bus, "have %d messages",
538 gst_atomic_queue_length (bus->priv->queue));
540 while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
541 if (bus->priv->poll) {
542 while (!gst_poll_read_control (bus->priv->poll)) {
543 if (errno == EWOULDBLOCK) {
544 /* Retry, this can happen if pushing to the queue has finished,
545 * popping here succeeded but writing control did not finish
546 * before we got to this line. */
547 /* Give other threads the chance to do something */
551 /* This is a real error and means that either the bus is in an
552 * inconsistent state, or the GstPoll is invalid. GstPoll already
553 * prints a critical warning about this, no need to do that again
560 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
561 message, GST_MESSAGE_TYPE_NAME (message),
562 GST_MESSAGE_SRC_NAME (message), (guint) types);
563 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
564 /* Extra check to ensure extended types don't get matched unless
566 if ((!GST_MESSAGE_TYPE_IS_EXTENDED (message))
567 || (types & GST_MESSAGE_EXTENDED)) {
568 /* exit the loop, we have a message */
573 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
574 gst_message_unref (message);
578 /* no need to wait, exit loop */
582 else if (timeout != GST_CLOCK_TIME_NONE) {
584 then = g_get_monotonic_time ();
587 now = g_get_monotonic_time ();
589 elapsed = (now - then) * GST_USECOND;
591 if (elapsed > timeout)
596 /* only here in timeout case */
597 g_assert (bus->priv->poll);
598 g_mutex_unlock (&bus->priv->queue_lock);
599 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
600 g_mutex_lock (&bus->priv->queue_lock);
603 GST_DEBUG_OBJECT (bus, "timed out, breaking loop");
606 GST_DEBUG_OBJECT (bus, "we got woken up, recheck for message");
612 g_mutex_unlock (&bus->priv->queue_lock);
620 * @bus: a #GstBus to pop
621 * @timeout: a timeout
623 * Gets a message from the bus, waiting up to the specified timeout.
625 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
626 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
629 * Returns: (transfer full) (nullable): the #GstMessage that is on the
630 * bus after the specified timeout or %NULL if the bus is empty
631 * after the timeout expired.
634 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
636 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
638 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
642 * gst_bus_pop_filtered:
643 * @bus: a #GstBus to pop
644 * @types: message types to take into account
646 * Gets a message matching @type from the bus. Will discard all messages on
647 * the bus that do not match @type and that have been posted before the first
648 * message that does match @type. If there is no message matching @type on
649 * the bus, all messages will be discarded. It is not possible to use message
650 * enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
652 * Returns: (transfer full) (nullable): the next #GstMessage matching
653 * @type that is on the bus, or %NULL if the bus is empty or there
654 * is no message matching @type.
657 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
659 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
660 g_return_val_if_fail (types != 0, NULL);
662 return gst_bus_timed_pop_filtered (bus, 0, types);
667 * @bus: a #GstBus to pop
669 * Gets a message from the bus.
671 * Returns: (transfer full) (nullable): the #GstMessage that is on the
672 * bus, or %NULL if the bus is empty.
675 gst_bus_pop (GstBus * bus)
677 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
679 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
686 * Peeks the message on the top of the bus' queue. The message will remain
687 * on the bus' message queue.
689 * Returns: (transfer full) (nullable): the #GstMessage that is on the
690 * bus, or %NULL if the bus is empty.
693 gst_bus_peek (GstBus * bus)
697 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
699 g_mutex_lock (&bus->priv->queue_lock);
700 message = gst_atomic_queue_peek (bus->priv->queue);
702 gst_message_ref (message);
703 g_mutex_unlock (&bus->priv->queue_lock);
705 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
711 * gst_bus_set_sync_handler:
712 * @bus: a #GstBus to install the handler on
713 * @func: (allow-none): The handler function to install
714 * @user_data: User data that will be sent to the handler function.
715 * @notify: called when @user_data becomes unused
717 * Sets the synchronous handler on the bus. The function will be called
718 * every time a new message is posted on the bus. Note that the function
719 * will be called in the same thread context as the posting object. This
720 * function is usually only called by the creator of the bus. Applications
721 * should handle messages asynchronously using the gst_bus watch and poll
724 * Before 1.16.3 it was not possible to replace an existing handler and
725 * clearing an existing handler with %NULL was not thread-safe.
728 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func,
729 gpointer user_data, GDestroyNotify notify)
731 SyncHandler *old_handler, *new_handler = NULL;
733 g_return_if_fail (GST_IS_BUS (bus));
736 new_handler = g_new0 (SyncHandler, 1);
737 new_handler->handler = func;
738 new_handler->user_data = user_data;
739 new_handler->destroy_notify = notify;
740 new_handler->ref_count = 1;
743 GST_OBJECT_LOCK (bus);
744 old_handler = g_steal_pointer (&bus->priv->sync_handler);
745 bus->priv->sync_handler = g_steal_pointer (&new_handler);
746 GST_OBJECT_UNLOCK (bus);
748 g_clear_pointer (&old_handler, sync_handler_unref);
752 * gst_bus_get_pollfd:
754 * @fd: (out): A GPollFD to fill
756 * Gets the file descriptor from the bus which can be used to get notified about
757 * messages being available with functions like g_poll(), and allows integration
758 * into other event loops based on file descriptors.
759 * Whenever a message is available, the POLLIN / %G_IO_IN event is set.
761 * Warning: NEVER read or write anything to the returned fd but only use it
762 * for getting notifications via g_poll() or similar and then use the normal
763 * GstBus API, e.g. gst_bus_pop().
768 gst_bus_get_pollfd (GstBus * bus, GPollFD * fd)
770 g_return_if_fail (GST_IS_BUS (bus));
771 g_return_if_fail (bus->priv->poll != NULL);
773 *fd = bus->priv->pollfd;
776 /* GSource for the bus
785 gst_bus_source_check (GSource * source)
787 GstBusSource *bsrc = (GstBusSource *) source;
789 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
793 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
796 GstBusFunc handler = (GstBusFunc) callback;
797 GstBusSource *bsource = (GstBusSource *) source;
802 g_return_val_if_fail (bsource != NULL, FALSE);
806 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
808 message = gst_bus_pop (bus);
810 /* The message queue might be empty if some other thread or callback set
811 * the bus to flushing between check/prepare and dispatch */
812 if (G_UNLIKELY (message == NULL))
818 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
821 keep = handler (bus, message, user_data);
822 gst_message_unref (message);
824 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
830 g_warning ("GstBus watch dispatched without callback\n"
831 "You must call g_source_set_callback().");
832 gst_message_unref (message);
837 #if GLIB_CHECK_VERSION(2,63,3)
839 gst_bus_source_dispose (GSource * source)
841 GstBusSource *bsource = (GstBusSource *) source;
846 GST_DEBUG_OBJECT (bus, "disposing source %p", source);
848 GST_OBJECT_LOCK (bus);
849 if (bus->priv->gsource == source)
850 bus->priv->gsource = NULL;
851 GST_OBJECT_UNLOCK (bus);
856 gst_bus_source_finalize (GSource * source)
858 GstBusSource *bsource = (GstBusSource *) source;
859 #if !GLIB_CHECK_VERSION(2,63,3)
860 GstBus *bus = bsource->bus;
862 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
864 GST_OBJECT_LOCK (bus);
865 if (bus->priv->gsource == source)
866 bus->priv->gsource = NULL;
867 GST_OBJECT_UNLOCK (bus);
870 gst_clear_object (&bsource->bus);
873 static GSourceFuncs gst_bus_source_funcs = {
875 gst_bus_source_check,
876 gst_bus_source_dispatch,
877 gst_bus_source_finalize
882 gst_bus_create_watch_unlocked (GstBus * bus)
884 GstBusSource *source;
886 if (bus->priv->gsource) {
887 GST_ERROR_OBJECT (bus,
888 "Tried to add new GSource while one was already there");
892 bus->priv->gsource = g_source_new (&gst_bus_source_funcs,
893 sizeof (GstBusSource));
894 source = (GstBusSource *) bus->priv->gsource;
896 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
897 #if GLIB_CHECK_VERSION(2,63,3)
898 g_source_set_dispose_function ((GSource *) source, gst_bus_source_dispose);
901 source->bus = gst_object_ref (bus);
902 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
904 return (GSource *) source;
908 * gst_bus_create_watch:
909 * @bus: a #GstBus to create the watch for
911 * Create watch for this bus. The #GSource will be dispatched whenever
912 * a message is on the bus. After the GSource is dispatched, the
913 * message is popped off the bus and unreffed.
915 * As with other watches, there can only be one watch on the bus, including
916 * any signal watch added with #gst_bus_add_signal_watch.
918 * Returns: (transfer full) (nullable): a #GSource that can be added to a #GMainLoop.
921 gst_bus_create_watch (GstBus * bus)
925 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
926 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
928 GST_OBJECT_LOCK (bus);
929 source = gst_bus_create_watch_unlocked (bus);
930 GST_OBJECT_UNLOCK (bus);
935 /* must be called with the bus OBJECT LOCK */
937 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
938 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
944 if (bus->priv->gsource) {
945 GST_ERROR_OBJECT (bus,
946 "Tried to add new watch while one was already there");
950 source = gst_bus_create_watch_unlocked (bus);
952 g_critical ("Creating bus watch failed");
956 if (priority != G_PRIORITY_DEFAULT)
957 g_source_set_priority (source, priority);
959 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
961 ctx = g_main_context_get_thread_default ();
962 id = g_source_attach (source, ctx);
963 g_source_unref (source);
966 bus->priv->gsource = source;
969 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
974 * gst_bus_add_watch_full: (rename-to gst_bus_add_watch)
975 * @bus: a #GstBus to create the watch for.
976 * @priority: The priority of the watch.
977 * @func: A function to call when a message is received.
978 * @user_data: user data passed to @func.
979 * @notify: the function to call when the source is removed.
981 * Adds a bus watch to the default main context with the given @priority (e.g.
982 * %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
983 * context set up using g_main_context_push_thread_default() (before
984 * one had to create a bus watch source and attach it to the desired main
985 * context 'manually').
987 * This function is used to receive asynchronous messages in the main loop.
988 * There can only be a single bus watch per bus, you must remove it before you
991 * The bus watch will only work if a #GMainLoop is being run.
993 * When @func is called, the message belongs to the caller; if you want to
994 * keep a copy of it, call gst_message_ref() before leaving @func.
996 * The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
997 * from @func. If the watch was added to the default main context it is also
998 * possible to remove the watch using g_source_remove().
1000 * The bus watch will take its own reference to the @bus, so it is safe to unref
1001 * @bus using gst_object_unref() after setting the bus watch.
1003 * Returns: The event source id or 0 if @bus already got an event source.
1006 gst_bus_add_watch_full (GstBus * bus, gint priority,
1007 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
1011 g_return_val_if_fail (GST_IS_BUS (bus), 0);
1013 GST_OBJECT_LOCK (bus);
1014 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
1015 GST_OBJECT_UNLOCK (bus);
1021 * gst_bus_add_watch: (skip)
1022 * @bus: a #GstBus to create the watch for
1023 * @func: A function to call when a message is received.
1024 * @user_data: user data passed to @func.
1026 * Adds a bus watch to the default main context with the default priority
1027 * ( %G_PRIORITY_DEFAULT ). It is also possible to use a non-default main
1028 * context set up using g_main_context_push_thread_default() (before
1029 * one had to create a bus watch source and attach it to the desired main
1030 * context 'manually').
1032 * This function is used to receive asynchronous messages in the main loop.
1033 * There can only be a single bus watch per bus, you must remove it before you
1034 * can set a new one.
1036 * The bus watch will only work if a #GMainLoop is being run.
1038 * The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
1039 * from @func. If the watch was added to the default main context it is also
1040 * possible to remove the watch using g_source_remove().
1042 * The bus watch will take its own reference to the @bus, so it is safe to unref
1043 * @bus using gst_object_unref() after setting the bus watch.
1045 * Returns: The event source id or 0 if @bus already got an event source.
1048 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
1050 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
1055 * gst_bus_remove_watch:
1056 * @bus: a #GstBus to remove the watch from.
1058 * Removes an installed bus watch from @bus.
1060 * Returns: %TRUE on success or %FALSE if @bus has no event source.
1066 gst_bus_remove_watch (GstBus * bus)
1070 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
1072 GST_OBJECT_LOCK (bus);
1074 if (bus->priv->gsource == NULL) {
1075 GST_ERROR_OBJECT (bus, "no bus watch was present");
1079 if (bus->priv->num_signal_watchers > 0) {
1080 GST_ERROR_OBJECT (bus,
1081 "trying to remove signal watch with gst_bus_remove_watch()");
1085 source = g_source_ref (bus->priv->gsource);
1086 bus->priv->gsource = NULL;
1088 GST_OBJECT_UNLOCK (bus);
1091 g_source_destroy (source);
1092 g_source_unref (source);
1098 GST_OBJECT_UNLOCK (bus);
1107 gboolean source_running;
1108 GstMessageType events;
1109 GstMessage *message;
1113 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
1115 GstMessageType type;
1117 if (!g_main_loop_is_running (poll_data->loop)) {
1118 GST_DEBUG ("mainloop %p not running", poll_data->loop);
1122 type = GST_MESSAGE_TYPE (message);
1124 if (type & poll_data->events) {
1125 g_assert (poll_data->message == NULL);
1126 /* keep ref to message */
1127 poll_data->message = gst_message_ref (message);
1128 GST_DEBUG ("mainloop %p quit", poll_data->loop);
1129 g_main_loop_quit (poll_data->loop);
1131 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
1136 poll_timeout (GstBusPollData * poll_data)
1138 GST_DEBUG ("mainloop %p quit", poll_data->loop);
1139 g_main_loop_quit (poll_data->loop);
1141 /* we don't remove the GSource as this would free our poll_data,
1142 * which we still need */
1147 poll_destroy (GstBusPollData * poll_data, gpointer unused)
1149 poll_data->source_running = FALSE;
1150 if (!poll_data->timeout_id) {
1151 g_main_loop_unref (poll_data->loop);
1152 g_slice_free (GstBusPollData, poll_data);
1157 poll_destroy_timeout (GstBusPollData * poll_data)
1159 poll_data->timeout_id = 0;
1160 if (!poll_data->source_running) {
1161 g_main_loop_unref (poll_data->loop);
1162 g_slice_free (GstBusPollData, poll_data);
1169 * @events: a mask of #GstMessageType, representing the set of message types to
1170 * poll for (note special handling of extended message types below)
1171 * @timeout: the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE to poll
1174 * Polls the bus for messages. Will block while waiting for messages to come.
1175 * You can specify a maximum time to poll with the @timeout parameter. If
1176 * @timeout is negative, this function will block indefinitely.
1178 * All messages not in @events will be popped off the bus and will be ignored.
1179 * It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
1182 * Because poll is implemented using the "message" signal enabled by
1183 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1184 * signal to be emitted for every message that poll sees. Thus a "message"
1185 * signal handler will see the same messages that this function sees -- neither
1186 * will steal messages from the other.
1188 * This function will run a #GMainLoop from the default main context when
1191 * You should never use this function, since it is pure evil. This is
1192 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1193 * other non-trivial application that uses the GLib main loop. As this function
1194 * runs a GLib main loop, any callback attached to the default GLib main
1195 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1196 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1197 * may do things you do not expect, e.g. destroy the main application window or
1198 * some other resource; change other application state; display a dialog and
1199 * run another main loop until the user clicks it away. In short, using this
1200 * function may add a lot of complexity to your code through unexpected
1201 * re-entrancy and unexpected changes to your application's state.
1203 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1204 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1205 * better handled by setting up an asynchronous bus watch and doing things
1208 * Returns: (transfer full) (nullable): the message that was received,
1209 * or %NULL if the poll timed out.
1212 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTime timeout)
1214 GstBusPollData *poll_data;
1218 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
1220 poll_data = g_slice_new (GstBusPollData);
1221 poll_data->source_running = TRUE;
1222 poll_data->loop = g_main_loop_new (NULL, FALSE);
1223 poll_data->events = events;
1224 poll_data->message = NULL;
1226 if (timeout != GST_CLOCK_TIME_NONE)
1227 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1228 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1229 (GDestroyNotify) poll_destroy_timeout);
1231 poll_data->timeout_id = 0;
1233 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1234 (GClosureNotify) poll_destroy, 0);
1236 /* these can be nested, so it's ok */
1237 gst_bus_add_signal_watch (bus);
1239 GST_DEBUG ("running mainloop %p", poll_data->loop);
1240 g_main_loop_run (poll_data->loop);
1241 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1243 gst_bus_remove_signal_watch (bus);
1246 ret = poll_data->message;
1248 if (poll_data->timeout_id)
1249 g_source_remove (poll_data->timeout_id);
1251 /* poll_data will be freed now */
1252 g_signal_handler_disconnect (bus, id);
1254 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1260 * gst_bus_async_signal_func:
1262 * @message: the #GstMessage received
1265 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1271 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1275 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1276 g_return_val_if_fail (message != NULL, TRUE);
1278 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1280 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1282 /* we never remove this source based on signal emission return values */
1287 * gst_bus_sync_signal_handler:
1289 * @message: the #GstMessage received
1292 * A helper #GstBusSyncHandler that can be used to convert all synchronous
1293 * messages into signals.
1295 * Returns: %GST_BUS_PASS
1298 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1302 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1303 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1305 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1307 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1309 return GST_BUS_PASS;
1313 * gst_bus_enable_sync_message_emission:
1314 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1316 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1317 * sync handler. This function is here so that code can ensure that they can
1318 * synchronously receive messages without having to affect what the bin's sync
1321 * This function may be called multiple times. To clean up, the caller is
1322 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1323 * as this function is called.
1325 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1326 * exactly the same -- this function enables *synchronous* emission of
1327 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1328 * to pop messages off the bus *asynchronously*. The sync-message signal
1329 * comes from the thread of whatever object posted the message; the "message"
1330 * signal is marshalled to the main thread via the #GMainLoop.
1333 gst_bus_enable_sync_message_emission (GstBus * bus)
1335 g_return_if_fail (GST_IS_BUS (bus));
1337 GST_OBJECT_LOCK (bus);
1338 bus->priv->num_sync_message_emitters++;
1339 GST_OBJECT_UNLOCK (bus);
1343 * gst_bus_disable_sync_message_emission:
1344 * @bus: a #GstBus on which you previously called
1345 * gst_bus_enable_sync_message_emission()
1347 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1348 * See gst_bus_enable_sync_message_emission() for more information.
1350 * In the event that multiple pieces of code have called
1351 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1352 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1353 * "cancelled" by calling this function. In this way the semantics are exactly
1354 * the same as gst_object_ref() that which calls enable should also call
1358 gst_bus_disable_sync_message_emission (GstBus * bus)
1360 g_return_if_fail (GST_IS_BUS (bus));
1361 g_return_if_fail (bus->priv->num_sync_message_emitters > 0);
1363 GST_OBJECT_LOCK (bus);
1364 bus->priv->num_sync_message_emitters--;
1365 GST_OBJECT_UNLOCK (bus);
1369 * gst_bus_add_signal_watch_full:
1370 * @bus: a #GstBus on which you want to receive the "message" signal
1371 * @priority: The priority of the watch.
1373 * Adds a bus signal watch to the default main context with the given @priority
1374 * (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
1375 * context set up using g_main_context_push_thread_default()
1376 * (before one had to create a bus watch source and attach it to the desired
1377 * main context 'manually').
1379 * After calling this statement, the bus will emit the "message" signal for each
1380 * message posted on the bus when the #GMainLoop is running.
1382 * This function may be called multiple times. To clean up, the caller is
1383 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1384 * function is called.
1386 * There can only be a single bus watch per bus, you must remove any signal
1387 * watch before you can set another type of watch.
1390 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1392 g_return_if_fail (GST_IS_BUS (bus));
1394 /* I know the callees don't take this lock, so go ahead and abuse it */
1395 GST_OBJECT_LOCK (bus);
1397 if (bus->priv->num_signal_watchers > 0)
1400 if (bus->priv->gsource)
1403 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1406 if (G_UNLIKELY (!bus->priv->gsource))
1411 bus->priv->num_signal_watchers++;
1413 GST_OBJECT_UNLOCK (bus);
1419 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1420 GST_OBJECT_UNLOCK (bus);
1425 g_critical ("Bus %s already has a GSource watch", GST_OBJECT_NAME (bus));
1426 GST_OBJECT_UNLOCK (bus);
1432 * gst_bus_add_signal_watch:
1433 * @bus: a #GstBus on which you want to receive the "message" signal
1435 * Adds a bus signal watch to the default main context with the default priority
1436 * ( %G_PRIORITY_DEFAULT ). It is also possible to use a non-default
1437 * main context set up using g_main_context_push_thread_default() (before
1438 * one had to create a bus watch source and attach it to the desired main
1439 * context 'manually').
1441 * After calling this statement, the bus will emit the "message" signal for each
1442 * message posted on the bus.
1444 * This function may be called multiple times. To clean up, the caller is
1445 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1446 * function is called.
1449 gst_bus_add_signal_watch (GstBus * bus)
1451 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1455 * gst_bus_remove_signal_watch:
1456 * @bus: a #GstBus you previously added a signal watch to
1458 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1461 gst_bus_remove_signal_watch (GstBus * bus)
1463 GSource *source = NULL;
1465 g_return_if_fail (GST_IS_BUS (bus));
1467 /* I know the callees don't take this lock, so go ahead and abuse it */
1468 GST_OBJECT_LOCK (bus);
1470 if (bus->priv->num_signal_watchers == 0)
1473 bus->priv->num_signal_watchers--;
1475 if (bus->priv->num_signal_watchers > 0)
1478 GST_DEBUG_OBJECT (bus, "removing gsource %u",
1479 g_source_get_id (bus->priv->gsource));
1481 g_assert (bus->priv->gsource);
1482 source = g_source_ref (bus->priv->gsource);
1483 bus->priv->gsource = NULL;
1486 GST_OBJECT_UNLOCK (bus);
1489 g_source_destroy (source);
1490 g_source_unref (source);
1498 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1499 GST_OBJECT_UNLOCK (bus);