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 mainloop.
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 };
112 struct _GstBusPrivate
114 GstAtomicQueue *queue;
117 GstBusSyncHandler sync_handler;
118 gpointer sync_handler_data;
119 GDestroyNotify sync_handler_notify;
121 guint num_signal_watchers;
123 guint num_sync_message_emitters;
124 GSource *signal_watch;
126 gboolean enable_async;
131 #define gst_bus_parent_class parent_class
132 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
135 gst_bus_set_property (GObject * object,
136 guint prop_id, const GValue * value, GParamSpec * pspec)
138 GstBus *bus = GST_BUS_CAST (object);
141 case PROP_ENABLE_ASYNC:
142 bus->priv->enable_async = g_value_get_boolean (value);
145 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
151 gst_bus_constructed (GObject * object)
153 GstBus *bus = GST_BUS_CAST (object);
155 if (bus->priv->enable_async) {
156 bus->priv->poll = gst_poll_new_timer ();
157 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
160 G_OBJECT_CLASS (gst_bus_parent_class)->constructed (object);
164 gst_bus_class_init (GstBusClass * klass)
166 GObjectClass *gobject_class = (GObjectClass *) klass;
168 gobject_class->dispose = gst_bus_dispose;
169 gobject_class->finalize = gst_bus_finalize;
170 gobject_class->set_property = gst_bus_set_property;
171 gobject_class->constructed = gst_bus_constructed;
174 * GstBus::enable-async:
176 * Enable async message delivery support for bus watches,
177 * gst_bus_pop() and similar API. Without this only the
178 * synchronous message handlers are called.
180 * This property is used to create the child element buses
183 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
184 g_param_spec_boolean ("enable-async", "Enable Async",
185 "Enable async message delivery for bus watches and gst_bus_pop()",
186 DEFAULT_ENABLE_ASYNC,
187 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
190 * GstBus::sync-message:
191 * @bus: the object which received the signal
192 * @message: the message that has been posted synchronously
194 * A message has been posted on the bus. This signal is emitted from the
195 * thread that posted the message so one has to be careful with locking.
197 * This signal will not be emitted by default, you have to call
198 * gst_bus_enable_sync_message_emission() before.
200 gst_bus_signals[SYNC_MESSAGE] =
201 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
202 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
203 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
204 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
208 * @bus: the object which received the signal
209 * @message: the message that has been posted asynchronously
211 * A message has been posted on the bus. This signal is emitted from a
212 * GSource added to the mainloop. this signal will only be emitted when
213 * there is a mainloop running.
215 gst_bus_signals[ASYNC_MESSAGE] =
216 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
217 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
218 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
219 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
221 g_type_class_add_private (klass, sizeof (GstBusPrivate));
225 gst_bus_init (GstBus * bus)
227 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
228 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
229 g_mutex_init (&bus->priv->queue_lock);
230 bus->priv->queue = gst_atomic_queue_new (32);
232 /* clear floating flag */
233 gst_object_ref_sink (bus);
235 GST_DEBUG_OBJECT (bus, "created");
239 gst_bus_dispose (GObject * object)
241 GstBus *bus = GST_BUS (object);
243 if (bus->priv->queue) {
246 g_mutex_lock (&bus->priv->queue_lock);
248 message = gst_atomic_queue_pop (bus->priv->queue);
250 gst_message_unref (message);
251 } while (message != NULL);
252 gst_atomic_queue_unref (bus->priv->queue);
253 bus->priv->queue = NULL;
254 g_mutex_unlock (&bus->priv->queue_lock);
255 g_mutex_clear (&bus->priv->queue_lock);
258 gst_poll_free (bus->priv->poll);
259 bus->priv->poll = NULL;
262 G_OBJECT_CLASS (parent_class)->dispose (object);
266 gst_bus_finalize (GObject * object)
268 GstBus *bus = GST_BUS (object);
270 if (bus->priv->sync_handler_notify)
271 bus->priv->sync_handler_notify (bus->priv->sync_handler_data);
273 G_OBJECT_CLASS (parent_class)->finalize (object);
279 * Creates a new #GstBus instance.
281 * Returns: (transfer full): a new #GstBus instance
288 result = g_object_newv (gst_bus_get_type (), 0, NULL);
289 GST_DEBUG_OBJECT (result, "created new bus");
296 * @bus: a #GstBus to post on
297 * @message: (transfer full): the #GstMessage to post
299 * Post a message on the given bus. Ownership of the message
300 * is taken by the bus.
302 * Returns: %TRUE if the message could be posted, %FALSE if the bus is flushing.
307 gst_bus_post (GstBus * bus, GstMessage * message)
309 GstBusSyncReply reply = GST_BUS_PASS;
310 GstBusSyncHandler handler;
311 gboolean emit_sync_message;
312 gpointer handler_data;
314 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
315 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
317 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
320 /* check we didn't accidentally add a public flag that maps to same value */
321 g_assert (!GST_MINI_OBJECT_FLAG_IS_SET (message,
322 GST_MESSAGE_FLAG_ASYNC_DELIVERY));
324 GST_OBJECT_LOCK (bus);
325 /* check if the bus is flushing */
326 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
329 handler = bus->priv->sync_handler;
330 handler_data = bus->priv->sync_handler_data;
331 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
332 GST_OBJECT_UNLOCK (bus);
334 /* first call the sync handler if it is installed */
336 reply = handler (bus, message, handler_data);
338 /* emit sync-message if requested to do so via
339 gst_bus_enable_sync_message_emission. terrible but effective */
340 if (emit_sync_message && reply != GST_BUS_DROP
341 && handler != gst_bus_sync_signal_handler)
342 gst_bus_sync_signal_handler (bus, message, NULL);
344 /* If this is a bus without async message delivery
345 * always drop the message */
346 if (!bus->priv->poll)
347 reply = GST_BUS_DROP;
349 /* now see what we should do with the message */
352 /* drop the message */
353 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
356 /* pass the message to the async queue, refcount passed in the queue */
357 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
358 gst_atomic_queue_push (bus->priv->queue, message);
359 gst_poll_write_control (bus->priv->poll);
360 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
365 /* async delivery, we need a mutex and a cond to block
367 GCond *cond = GST_MESSAGE_GET_COND (message);
368 GMutex *lock = GST_MESSAGE_GET_LOCK (message);
373 GST_MINI_OBJECT_FLAG_SET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
375 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
377 /* now we lock the message mutex, send the message to the async
378 * queue. When the message is handled by the app and destroyed,
379 * the cond will be signalled and we can continue */
382 gst_atomic_queue_push (bus->priv->queue, message);
383 gst_poll_write_control (bus->priv->poll);
385 /* now block till the message is freed */
386 g_cond_wait (cond, lock);
388 /* we acquired a new ref from gst_message_dispose() so we can clean up */
389 g_mutex_unlock (lock);
391 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
393 GST_MINI_OBJECT_FLAG_UNSET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
395 g_mutex_clear (lock);
398 gst_message_unref (message);
402 g_warning ("invalid return from bus sync handler");
410 GST_DEBUG_OBJECT (bus, "bus is flushing");
411 GST_OBJECT_UNLOCK (bus);
412 gst_message_unref (message);
419 * gst_bus_have_pending:
420 * @bus: a #GstBus to check
422 * Check if there are pending messages on the bus that
425 * Returns: %TRUE if there are messages on the bus to be handled, %FALSE
431 gst_bus_have_pending (GstBus * bus)
435 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
437 /* see if there is a message on the bus */
438 result = gst_atomic_queue_length (bus->priv->queue) != 0;
444 * gst_bus_set_flushing:
446 * @flushing: whether or not to flush the bus
448 * If @flushing, flush out and unref any messages queued in the bus. Releases
449 * references to the message origin objects. Will flush future messages until
450 * gst_bus_set_flushing() sets @flushing to %FALSE.
455 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
458 GList *message_list = NULL;
460 g_return_if_fail (GST_IS_BUS (bus));
462 GST_OBJECT_LOCK (bus);
465 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
467 GST_DEBUG_OBJECT (bus, "set bus flushing");
469 while ((message = gst_bus_pop (bus)))
470 message_list = g_list_prepend (message_list, message);
472 GST_DEBUG_OBJECT (bus, "unset bus flushing");
473 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
476 GST_OBJECT_UNLOCK (bus);
478 g_list_free_full (message_list, (GDestroyNotify) gst_message_unref);
482 * gst_bus_timed_pop_filtered:
483 * @bus: a #GstBus to pop from
484 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
485 * @types: message types to take into account, GST_MESSAGE_ANY for any type
487 * Get a message from the bus whose type matches the message type mask @types,
488 * waiting up to the specified timeout (and discarding any messages that do not
489 * match the mask provided).
491 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
492 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
493 * matching message was posted on the bus.
495 * Returns: (transfer full) (nullable): a #GstMessage matching the
496 * filter in @types, or %NULL if no matching message was found on
497 * the bus until the timeout expired. The message is taken from
498 * the bus and needs to be unreffed with gst_message_unref() after
504 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
505 GstMessageType types)
509 gboolean first_round = TRUE;
510 GstClockTime elapsed = 0;
512 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
513 g_return_val_if_fail (types != 0, NULL);
514 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
516 g_mutex_lock (&bus->priv->queue_lock);
521 GST_LOG_OBJECT (bus, "have %d messages",
522 gst_atomic_queue_length (bus->priv->queue));
524 while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
525 if (bus->priv->poll) {
526 while (!gst_poll_read_control (bus->priv->poll)) {
527 if (errno == EWOULDBLOCK) {
528 /* Retry, this can happen if pushing to the queue has finished,
529 * popping here succeeded but writing control did not finish
530 * before we got to this line. */
531 /* Give other threads the chance to do something */
535 /* This is a real error and means that either the bus is in an
536 * inconsistent state, or the GstPoll is invalid. GstPoll already
537 * prints a critical warning about this, no need to do that again
544 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
545 message, GST_MESSAGE_TYPE_NAME (message),
546 GST_MESSAGE_SRC_NAME (message), (guint) types);
547 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
548 /* Extra check to ensure extended types don't get matched unless
550 if ((!GST_MESSAGE_TYPE_IS_EXTENDED (message))
551 || (types & GST_MESSAGE_EXTENDED)) {
552 /* exit the loop, we have a message */
557 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
558 gst_message_unref (message);
562 /* no need to wait, exit loop */
566 else if (timeout != GST_CLOCK_TIME_NONE) {
568 g_get_current_time (&then);
571 g_get_current_time (&now);
573 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
575 if (elapsed > timeout)
580 /* only here in timeout case */
581 g_assert (bus->priv->poll);
582 g_mutex_unlock (&bus->priv->queue_lock);
583 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
584 g_mutex_lock (&bus->priv->queue_lock);
587 GST_INFO_OBJECT (bus, "timed out, breaking loop");
590 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
596 g_mutex_unlock (&bus->priv->queue_lock);
604 * @bus: a #GstBus to pop
605 * @timeout: a timeout
607 * Get a message from the bus, waiting up to the specified timeout.
609 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
610 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
613 * Returns: (transfer full) (nullable): the #GstMessage that is on the
614 * bus after the specified timeout or %NULL if the bus is empty
615 * after the timeout expired. The message is taken from the bus
616 * and needs to be unreffed with gst_message_unref() after usage.
621 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
623 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
625 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
629 * gst_bus_pop_filtered:
630 * @bus: a #GstBus to pop
631 * @types: message types to take into account
633 * Get a message matching @type from the bus. Will discard all messages on
634 * the bus that do not match @type and that have been posted before the first
635 * message that does match @type. If there is no message matching @type on
636 * the bus, all messages will be discarded. It is not possible to use message
637 * enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
639 * Returns: (transfer full) (nullable): the next #GstMessage matching
640 * @type that is on the bus, or %NULL if the bus is empty or there
641 * is no message matching @type. The message is taken from the bus
642 * and needs to be unreffed with gst_message_unref() after usage.
647 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
649 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
650 g_return_val_if_fail (types != 0, NULL);
652 return gst_bus_timed_pop_filtered (bus, 0, types);
657 * @bus: a #GstBus to pop
659 * Get a message from the bus.
661 * Returns: (transfer full) (nullable): the #GstMessage that is on the
662 * bus, or %NULL if the bus is empty. The message is taken from
663 * the bus and needs to be unreffed with gst_message_unref() after
669 gst_bus_pop (GstBus * bus)
671 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
673 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
680 * Peek the message on the top of the bus' queue. The message will remain
681 * on the bus' message queue. A reference is returned, and needs to be unreffed
684 * Returns: (transfer full) (nullable): the #GstMessage that is on the
685 * bus, or %NULL if the bus is empty.
690 gst_bus_peek (GstBus * bus)
694 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
696 g_mutex_lock (&bus->priv->queue_lock);
697 message = gst_atomic_queue_peek (bus->priv->queue);
699 gst_message_ref (message);
700 g_mutex_unlock (&bus->priv->queue_lock);
702 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
708 * gst_bus_set_sync_handler:
709 * @bus: a #GstBus to install the handler on
710 * @func: (allow-none): The handler function to install
711 * @user_data: User data that will be sent to the handler function.
712 * @notify: called when @user_data becomes unused
714 * Sets the synchronous handler on the bus. The function will be called
715 * every time a new message is posted on the bus. Note that the function
716 * will be called in the same thread context as the posting object. This
717 * function is usually only called by the creator of the bus. Applications
718 * should handle messages asynchronously using the gst_bus watch and poll
721 * You cannot replace an existing sync_handler. You can pass %NULL to this
722 * function, which will clear the existing handler.
725 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func,
726 gpointer user_data, GDestroyNotify notify)
728 GDestroyNotify old_notify;
730 g_return_if_fail (GST_IS_BUS (bus));
732 GST_OBJECT_LOCK (bus);
733 /* Assert if the user attempts to replace an existing sync_handler,
734 * other than to clear it */
735 if (func != NULL && bus->priv->sync_handler != NULL)
738 if ((old_notify = bus->priv->sync_handler_notify)) {
739 gpointer old_data = bus->priv->sync_handler_data;
741 bus->priv->sync_handler_data = NULL;
742 bus->priv->sync_handler_notify = NULL;
743 GST_OBJECT_UNLOCK (bus);
745 old_notify (old_data);
747 GST_OBJECT_LOCK (bus);
749 bus->priv->sync_handler = func;
750 bus->priv->sync_handler_data = user_data;
751 bus->priv->sync_handler_notify = notify;
752 GST_OBJECT_UNLOCK (bus);
758 GST_OBJECT_UNLOCK (bus);
759 g_warning ("cannot replace existing sync handler");
764 /* GSource for the bus
773 gst_bus_source_prepare (GSource * source, gint * timeout)
780 gst_bus_source_check (GSource * source)
782 GstBusSource *bsrc = (GstBusSource *) source;
784 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
788 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
791 GstBusFunc handler = (GstBusFunc) callback;
792 GstBusSource *bsource = (GstBusSource *) source;
797 g_return_val_if_fail (bsource != NULL, FALSE);
801 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
803 message = gst_bus_pop (bus);
805 /* The message queue might be empty if some other thread or callback set
806 * the bus to flushing between check/prepare and dispatch */
807 if (G_UNLIKELY (message == NULL))
813 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
816 keep = handler (bus, message, user_data);
817 gst_message_unref (message);
819 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
825 g_warning ("GstBus watch dispatched without callback\n"
826 "You must call g_source_set_callback().");
827 gst_message_unref (message);
833 gst_bus_source_finalize (GSource * source)
835 GstBusSource *bsource = (GstBusSource *) source;
840 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
842 GST_OBJECT_LOCK (bus);
843 if (bus->priv->signal_watch == source)
844 bus->priv->signal_watch = NULL;
845 GST_OBJECT_UNLOCK (bus);
847 gst_object_unref (bsource->bus);
851 static GSourceFuncs gst_bus_source_funcs = {
852 gst_bus_source_prepare,
853 gst_bus_source_check,
854 gst_bus_source_dispatch,
855 gst_bus_source_finalize
859 * gst_bus_create_watch:
860 * @bus: a #GstBus to create the watch for
862 * Create watch for this bus. The GSource will be dispatched whenever
863 * a message is on the bus. After the GSource is dispatched, the
864 * message is popped off the bus and unreffed.
866 * Returns: (transfer full): a #GSource that can be added to a mainloop.
869 gst_bus_create_watch (GstBus * bus)
871 GstBusSource *source;
873 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
874 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
876 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
877 sizeof (GstBusSource));
879 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
881 source->bus = gst_object_ref (bus);
882 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
884 return (GSource *) source;
887 /* must be called with the bus OBJECT LOCK */
889 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
890 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
896 if (bus->priv->signal_watch) {
897 GST_ERROR_OBJECT (bus,
898 "Tried to add new watch while one was already there");
902 source = gst_bus_create_watch (bus);
904 g_critical ("Creating bus watch failed");
908 if (priority != G_PRIORITY_DEFAULT)
909 g_source_set_priority (source, priority);
911 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
913 ctx = g_main_context_get_thread_default ();
914 id = g_source_attach (source, ctx);
915 g_source_unref (source);
918 bus->priv->signal_watch = source;
921 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
926 * gst_bus_add_watch_full: (rename-to gst_bus_add_watch)
927 * @bus: a #GstBus to create the watch for.
928 * @priority: The priority of the watch.
929 * @func: A function to call when a message is received.
930 * @user_data: user data passed to @func.
931 * @notify: the function to call when the source is removed.
933 * Adds a bus watch to the default main context with the given @priority (e.g.
934 * %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
935 * context set up using g_main_context_push_thread_default() (before
936 * one had to create a bus watch source and attach it to the desired main
937 * context 'manually').
939 * This function is used to receive asynchronous messages in the main loop.
940 * There can only be a single bus watch per bus, you must remove it before you
943 * The bus watch will only work if a GLib main loop is being run.
945 * When @func is called, the message belongs to the caller; if you want to
946 * keep a copy of it, call gst_message_ref() before leaving @func.
948 * The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
949 * from @func. If the watch was added to the default main context it is also
950 * possible to remove the watch using g_source_remove().
954 * Returns: The event source id or 0 if @bus already got an event source.
957 gst_bus_add_watch_full (GstBus * bus, gint priority,
958 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
962 g_return_val_if_fail (GST_IS_BUS (bus), 0);
964 GST_OBJECT_LOCK (bus);
965 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
966 GST_OBJECT_UNLOCK (bus);
972 * gst_bus_add_watch: (skip)
973 * @bus: a #GstBus to create the watch for
974 * @func: A function to call when a message is received.
975 * @user_data: user data passed to @func.
977 * Adds a bus watch to the default main context with the default priority
978 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default main
979 * context set up using g_main_context_push_thread_default() (before
980 * one had to create a bus watch source and attach it to the desired main
981 * context 'manually').
983 * This function is used to receive asynchronous messages in the main loop.
984 * There can only be a single bus watch per bus, you must remove it before you
987 * The bus watch will only work if a GLib main loop is being run.
989 * The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
990 * from @func. If the watch was added to the default main context it is also
991 * possible to remove the watch using g_source_remove().
993 * Returns: The event source id or 0 if @bus already got an event source.
998 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
1000 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
1005 * gst_bus_remove_watch:
1006 * @bus: a #GstBus to remove the watch from.
1008 * Removes an installed bus watch from @bus.
1010 * Returns: %TRUE on success or %FALSE if @bus has no event source.
1016 gst_bus_remove_watch (GstBus * bus)
1020 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
1022 GST_OBJECT_LOCK (bus);
1024 if (bus->priv->signal_watch == NULL) {
1025 GST_ERROR_OBJECT (bus, "no bus watch was present");
1029 watch_id = bus->priv->signal_watch;
1031 GST_OBJECT_UNLOCK (bus);
1033 g_source_destroy (watch_id);
1038 GST_OBJECT_UNLOCK (bus);
1047 gboolean source_running;
1048 GstMessageType events;
1049 GstMessage *message;
1053 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
1055 GstMessageType type;
1057 if (!g_main_loop_is_running (poll_data->loop)) {
1058 GST_DEBUG ("mainloop %p not running", poll_data->loop);
1062 type = GST_MESSAGE_TYPE (message);
1064 if (type & poll_data->events) {
1065 g_assert (poll_data->message == NULL);
1066 /* keep ref to message */
1067 poll_data->message = gst_message_ref (message);
1068 GST_DEBUG ("mainloop %p quit", poll_data->loop);
1069 g_main_loop_quit (poll_data->loop);
1071 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
1076 poll_timeout (GstBusPollData * poll_data)
1078 GST_DEBUG ("mainloop %p quit", poll_data->loop);
1079 g_main_loop_quit (poll_data->loop);
1081 /* we don't remove the GSource as this would free our poll_data,
1082 * which we still need */
1087 poll_destroy (GstBusPollData * poll_data, gpointer unused)
1089 poll_data->source_running = FALSE;
1090 if (!poll_data->timeout_id) {
1091 g_main_loop_unref (poll_data->loop);
1092 g_slice_free (GstBusPollData, poll_data);
1097 poll_destroy_timeout (GstBusPollData * poll_data)
1099 poll_data->timeout_id = 0;
1100 if (!poll_data->source_running) {
1101 g_main_loop_unref (poll_data->loop);
1102 g_slice_free (GstBusPollData, poll_data);
1109 * @events: a mask of #GstMessageType, representing the set of message types to
1110 * poll for (note special handling of extended message types below)
1111 * @timeout: the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE to poll
1114 * Poll the bus for messages. Will block while waiting for messages to come.
1115 * You can specify a maximum time to poll with the @timeout parameter. If
1116 * @timeout is negative, this function will block indefinitely.
1118 * All messages not in @events will be popped off the bus and will be ignored.
1119 * It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
1122 * Because poll is implemented using the "message" signal enabled by
1123 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1124 * signal to be emitted for every message that poll sees. Thus a "message"
1125 * signal handler will see the same messages that this function sees -- neither
1126 * will steal messages from the other.
1128 * This function will run a main loop from the default main context when
1131 * You should never use this function, since it is pure evil. This is
1132 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1133 * other non-trivial application that uses the GLib main loop. As this function
1134 * runs a GLib main loop, any callback attached to the default GLib main
1135 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1136 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1137 * may do things you do not expect, e.g. destroy the main application window or
1138 * some other resource; change other application state; display a dialog and
1139 * run another main loop until the user clicks it away. In short, using this
1140 * function may add a lot of complexity to your code through unexpected
1141 * re-entrancy and unexpected changes to your application's state.
1143 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1144 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1145 * better handled by setting up an asynchronous bus watch and doing things
1148 * Returns: (transfer full) (nullable): the message that was received,
1149 * or %NULL if the poll timed out. The message is taken from the
1150 * bus and needs to be unreffed with gst_message_unref() after
1154 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTime timeout)
1156 GstBusPollData *poll_data;
1160 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
1162 poll_data = g_slice_new (GstBusPollData);
1163 poll_data->source_running = TRUE;
1164 poll_data->loop = g_main_loop_new (NULL, FALSE);
1165 poll_data->events = events;
1166 poll_data->message = NULL;
1168 if (timeout != GST_CLOCK_TIME_NONE)
1169 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1170 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1171 (GDestroyNotify) poll_destroy_timeout);
1173 poll_data->timeout_id = 0;
1175 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1176 (GClosureNotify) poll_destroy, 0);
1178 /* these can be nested, so it's ok */
1179 gst_bus_add_signal_watch (bus);
1181 GST_DEBUG ("running mainloop %p", poll_data->loop);
1182 g_main_loop_run (poll_data->loop);
1183 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1185 gst_bus_remove_signal_watch (bus);
1188 ret = poll_data->message;
1190 if (poll_data->timeout_id)
1191 g_source_remove (poll_data->timeout_id);
1193 /* poll_data will be freed now */
1194 g_signal_handler_disconnect (bus, id);
1196 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1202 * gst_bus_async_signal_func:
1204 * @message: the #GstMessage received
1207 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1213 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1217 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1218 g_return_val_if_fail (message != NULL, TRUE);
1220 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1222 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1224 /* we never remove this source based on signal emission return values */
1229 * gst_bus_sync_signal_handler:
1231 * @message: the #GstMessage received
1234 * A helper GstBusSyncHandler that can be used to convert all synchronous
1235 * messages into signals.
1237 * Returns: GST_BUS_PASS
1240 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1244 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1245 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1247 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1249 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1251 return GST_BUS_PASS;
1255 * gst_bus_enable_sync_message_emission:
1256 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1258 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1259 * sync handler. This function is here so that code can ensure that they can
1260 * synchronously receive messages without having to affect what the bin's sync
1263 * This function may be called multiple times. To clean up, the caller is
1264 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1265 * as this function is called.
1267 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1268 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1269 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1270 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1271 * comes from the thread of whatever object posted the message; the "message"
1272 * signal is marshalled to the main thread via the main loop.
1277 gst_bus_enable_sync_message_emission (GstBus * bus)
1279 g_return_if_fail (GST_IS_BUS (bus));
1281 GST_OBJECT_LOCK (bus);
1282 bus->priv->num_sync_message_emitters++;
1283 GST_OBJECT_UNLOCK (bus);
1287 * gst_bus_disable_sync_message_emission:
1288 * @bus: a #GstBus on which you previously called
1289 * gst_bus_enable_sync_message_emission()
1291 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1292 * See gst_bus_enable_sync_message_emission() for more information.
1294 * In the event that multiple pieces of code have called
1295 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1296 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1297 * "cancelled" by calling this function. In this way the semantics are exactly
1298 * the same as gst_object_ref() that which calls enable should also call
1304 gst_bus_disable_sync_message_emission (GstBus * bus)
1306 g_return_if_fail (GST_IS_BUS (bus));
1307 g_return_if_fail (bus->priv->num_sync_message_emitters > 0);
1309 GST_OBJECT_LOCK (bus);
1310 bus->priv->num_sync_message_emitters--;
1311 GST_OBJECT_UNLOCK (bus);
1315 * gst_bus_add_signal_watch_full:
1316 * @bus: a #GstBus on which you want to receive the "message" signal
1317 * @priority: The priority of the watch.
1319 * Adds a bus signal watch to the default main context with the given @priority
1320 * (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
1321 * context set up using g_main_context_push_thread_default()
1322 * (before one had to create a bus watch source and attach it to the desired
1323 * main context 'manually').
1325 * After calling this statement, the bus will emit the "message" signal for each
1326 * message posted on the bus when the main loop is running.
1328 * This function may be called multiple times. To clean up, the caller is
1329 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1330 * function is called.
1332 * There can only be a single bus watch per bus, you must remove any signal
1333 * watch before you can set another type of watch.
1338 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1340 g_return_if_fail (GST_IS_BUS (bus));
1342 /* I know the callees don't take this lock, so go ahead and abuse it */
1343 GST_OBJECT_LOCK (bus);
1345 if (bus->priv->num_signal_watchers > 0)
1348 /* this should not fail because the counter above takes care of it */
1349 g_assert (!bus->priv->signal_watch);
1351 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1354 if (G_UNLIKELY (!bus->priv->signal_watch))
1359 bus->priv->num_signal_watchers++;
1361 GST_OBJECT_UNLOCK (bus);
1367 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1368 GST_OBJECT_UNLOCK (bus);
1374 * gst_bus_add_signal_watch:
1375 * @bus: a #GstBus on which you want to receive the "message" signal
1377 * Adds a bus signal watch to the default main context with the default priority
1378 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default
1379 * main context set up using g_main_context_push_thread_default() (before
1380 * one had to create a bus watch source and attach it to the desired main
1381 * context 'manually').
1383 * After calling this statement, the bus will emit the "message" signal for each
1384 * message posted on the bus.
1386 * This function may be called multiple times. To clean up, the caller is
1387 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1388 * function is called.
1393 gst_bus_add_signal_watch (GstBus * bus)
1395 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1399 * gst_bus_remove_signal_watch:
1400 * @bus: a #GstBus you previously added a signal watch to
1402 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1407 gst_bus_remove_signal_watch (GstBus * bus)
1409 GSource *source = NULL;
1411 g_return_if_fail (GST_IS_BUS (bus));
1413 /* I know the callees don't take this lock, so go ahead and abuse it */
1414 GST_OBJECT_LOCK (bus);
1416 if (bus->priv->num_signal_watchers == 0)
1419 bus->priv->num_signal_watchers--;
1421 if (bus->priv->num_signal_watchers > 0)
1424 GST_DEBUG_OBJECT (bus, "removing signal watch %u",
1425 g_source_get_id (bus->priv->signal_watch));
1427 source = bus->priv->signal_watch;
1430 GST_OBJECT_UNLOCK (bus);
1433 g_source_destroy (source);
1440 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1441 GST_OBJECT_UNLOCK (bus);