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.
24 * @short_description: Asynchronous message bus subsystem
25 * @see_also: #GstMessage, #GstElement
27 * The #GstBus is an object responsible for delivering #GstMessage packets in
28 * a first-in first-out way from the streaming threads (see #GstTask) to the
31 * Since the application typically only wants to deal with delivery of these
32 * messages from one thread, the GstBus will marshall the messages between
33 * different threads. This is important since the actual streaming of media
34 * is done in another thread than the application.
36 * The GstBus provides support for #GSource based notifications. This makes it
37 * possible to handle the delivery in the glib mainloop.
39 * The #GSource callback function gst_bus_async_signal_func() can be used to
40 * convert all bus messages into signal emissions.
42 * A message is posted on the bus with the gst_bus_post() method. With the
43 * gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a
44 * previously posted message.
46 * The bus can be polled with the gst_bus_poll() method. This methods blocks
47 * up to the specified timeout value until one of the specified messages types
48 * is posted on the bus. The application can then gst_bus_pop() the messages
49 * from the bus to handle them.
50 * Alternatively the application can register an asynchronous bus function
51 * using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will
52 * install a #GSource in the default glib main loop and will deliver messages
53 * a short while after they have been posted. Note that the main loop should
54 * be running for the asynchronous callbacks.
56 * It is also possible to get messages from the bus without any thread
57 * marshalling with the gst_bus_set_sync_handler() method. This makes it
58 * possible to react to a message in the same thread that posted the
59 * message on the bus. This should only be used if the application is able
60 * to deal with messages from different threads.
62 * Every #GstPipeline has one bus.
64 * Note that a #GstPipeline will set its bus into flushing state when changing
65 * from READY to NULL state.
68 #include "gst_private.h"
73 #include <sys/types.h>
75 #include "gstatomicqueue.h"
80 #include "glib-compat-private.h"
84 # define EWOULDBLOCK EAGAIN /* This is just to placate gcc */
86 #endif /* G_OS_WIN32 */
88 #define GST_CAT_DEFAULT GST_CAT_BUS
98 #define DEFAULT_ENABLE_ASYNC (TRUE)
106 static void gst_bus_dispose (GObject * object);
107 static void gst_bus_finalize (GObject * object);
109 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
111 struct _GstBusPrivate
113 GstAtomicQueue *queue;
116 GstBusSyncHandler sync_handler;
117 gpointer sync_handler_data;
118 GDestroyNotify sync_handler_notify;
120 guint num_signal_watchers;
122 guint num_sync_message_emitters;
123 GSource *signal_watch;
125 gboolean enable_async;
130 #define gst_bus_parent_class parent_class
131 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
134 gst_bus_set_property (GObject * object,
135 guint prop_id, const GValue * value, GParamSpec * pspec)
137 GstBus *bus = GST_BUS_CAST (object);
140 case PROP_ENABLE_ASYNC:
141 bus->priv->enable_async = g_value_get_boolean (value);
144 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
150 gst_bus_constructed (GObject * object)
152 GstBus *bus = GST_BUS_CAST (object);
154 if (bus->priv->enable_async) {
155 bus->priv->poll = gst_poll_new_timer ();
156 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
159 G_OBJECT_CLASS (gst_bus_parent_class)->constructed (object);
163 gst_bus_class_init (GstBusClass * klass)
165 GObjectClass *gobject_class = (GObjectClass *) klass;
167 gobject_class->dispose = gst_bus_dispose;
168 gobject_class->finalize = gst_bus_finalize;
169 gobject_class->set_property = gst_bus_set_property;
170 gobject_class->constructed = gst_bus_constructed;
173 * GstBus::enable-async:
175 * Enable async message delivery support for bus watches,
176 * gst_bus_pop() and similar API. Without this only the
177 * synchronous message handlers are called.
179 * This property is used to create the child element buses
182 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
183 g_param_spec_boolean ("enable-async", "Enable Async",
184 "Enable async message delivery for bus watches and gst_bus_pop()",
185 DEFAULT_ENABLE_ASYNC,
186 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
189 * GstBus::sync-message:
190 * @bus: the object which received the signal
191 * @message: the message that has been posted synchronously
193 * A message has been posted on the bus. This signal is emitted from the
194 * thread that posted the message so one has to be careful with locking.
196 * This signal will not be emitted by default, you have to call
197 * gst_bus_enable_sync_message_emission() before.
199 gst_bus_signals[SYNC_MESSAGE] =
200 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
201 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
202 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
203 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
207 * @bus: the object which received the signal
208 * @message: the message that has been posted asynchronously
210 * A message has been posted on the bus. This signal is emitted from a
211 * GSource added to the mainloop. this signal will only be emitted when
212 * there is a mainloop running.
214 gst_bus_signals[ASYNC_MESSAGE] =
215 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
216 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
217 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
218 g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
220 g_type_class_add_private (klass, sizeof (GstBusPrivate));
224 gst_bus_init (GstBus * bus)
226 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
227 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
228 g_mutex_init (&bus->priv->queue_lock);
229 bus->priv->queue = gst_atomic_queue_new (32);
231 /* clear floating flag */
232 gst_object_ref_sink (bus);
234 GST_DEBUG_OBJECT (bus, "created");
238 gst_bus_dispose (GObject * object)
240 GstBus *bus = GST_BUS (object);
242 if (bus->priv->queue) {
245 g_mutex_lock (&bus->priv->queue_lock);
247 message = gst_atomic_queue_pop (bus->priv->queue);
249 gst_message_unref (message);
250 } while (message != NULL);
251 gst_atomic_queue_unref (bus->priv->queue);
252 bus->priv->queue = NULL;
253 g_mutex_unlock (&bus->priv->queue_lock);
254 g_mutex_clear (&bus->priv->queue_lock);
257 gst_poll_free (bus->priv->poll);
258 bus->priv->poll = NULL;
261 G_OBJECT_CLASS (parent_class)->dispose (object);
265 gst_bus_finalize (GObject * object)
267 GstBus *bus = GST_BUS (object);
269 if (bus->priv->sync_handler_notify)
270 bus->priv->sync_handler_notify (bus->priv->sync_handler_data);
272 G_OBJECT_CLASS (parent_class)->finalize (object);
278 * Creates a new #GstBus instance.
280 * Returns: (transfer full): a new #GstBus instance
287 result = g_object_newv (gst_bus_get_type (), 0, NULL);
288 GST_DEBUG_OBJECT (result, "created new bus");
295 * @bus: a #GstBus to post on
296 * @message: (transfer full): the #GstMessage to post
298 * Post a message on the given bus. Ownership of the message
299 * is taken by the bus.
301 * Returns: %TRUE if the message could be posted, %FALSE if the bus is flushing.
306 gst_bus_post (GstBus * bus, GstMessage * message)
308 GstBusSyncReply reply = GST_BUS_PASS;
309 GstBusSyncHandler handler;
310 gboolean emit_sync_message;
311 gpointer handler_data;
313 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
314 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
316 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus %" GST_PTR_FORMAT, message,
319 /* check we didn't accidentally add a public flag that maps to same value */
320 g_assert (!GST_MINI_OBJECT_FLAG_IS_SET (message,
321 GST_MESSAGE_FLAG_ASYNC_DELIVERY));
323 GST_OBJECT_LOCK (bus);
324 /* check if the bus is flushing */
325 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
328 handler = bus->priv->sync_handler;
329 handler_data = bus->priv->sync_handler_data;
330 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
331 GST_OBJECT_UNLOCK (bus);
333 /* first call the sync handler if it is installed */
335 reply = handler (bus, message, handler_data);
337 /* emit sync-message if requested to do so via
338 gst_bus_enable_sync_message_emission. terrible but effective */
339 if (emit_sync_message && reply != GST_BUS_DROP
340 && handler != gst_bus_sync_signal_handler)
341 gst_bus_sync_signal_handler (bus, message, NULL);
343 /* If this is a bus without async message delivery
344 * always drop the message */
345 if (!bus->priv->poll)
346 reply = GST_BUS_DROP;
348 /* now see what we should do with the message */
351 /* drop the message */
352 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
355 /* pass the message to the async queue, refcount passed in the queue */
356 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
357 gst_atomic_queue_push (bus->priv->queue, message);
358 gst_poll_write_control (bus->priv->poll);
359 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
364 /* async delivery, we need a mutex and a cond to block
366 GCond *cond = GST_MESSAGE_GET_COND (message);
367 GMutex *lock = GST_MESSAGE_GET_LOCK (message);
372 GST_MINI_OBJECT_FLAG_SET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
374 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
376 /* now we lock the message mutex, send the message to the async
377 * queue. When the message is handled by the app and destroyed,
378 * the cond will be signalled and we can continue */
381 gst_atomic_queue_push (bus->priv->queue, message);
382 gst_poll_write_control (bus->priv->poll);
384 /* now block till the message is freed */
385 g_cond_wait (cond, lock);
387 /* we acquired a new ref from gst_message_dispose() so we can clean up */
388 g_mutex_unlock (lock);
390 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
392 GST_MINI_OBJECT_FLAG_UNSET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
394 g_mutex_clear (lock);
397 gst_message_unref (message);
401 g_warning ("invalid return from bus sync handler");
409 GST_DEBUG_OBJECT (bus, "bus is flushing");
410 GST_OBJECT_UNLOCK (bus);
411 gst_message_unref (message);
418 * gst_bus_have_pending:
419 * @bus: a #GstBus to check
421 * Check if there are pending messages on the bus that
424 * Returns: %TRUE if there are messages on the bus to be handled, %FALSE
430 gst_bus_have_pending (GstBus * bus)
434 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
436 /* see if there is a message on the bus */
437 result = gst_atomic_queue_length (bus->priv->queue) != 0;
443 * gst_bus_set_flushing:
445 * @flushing: whether or not to flush the bus
447 * If @flushing, flush out and unref any messages queued in the bus. Releases
448 * references to the message origin objects. Will flush future messages until
449 * gst_bus_set_flushing() sets @flushing to %FALSE.
454 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
457 GList *message_list = NULL;
459 g_return_if_fail (GST_IS_BUS (bus));
461 GST_OBJECT_LOCK (bus);
464 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
466 GST_DEBUG_OBJECT (bus, "set bus flushing");
468 while ((message = gst_bus_pop (bus)))
469 message_list = g_list_prepend (message_list, message);
471 GST_DEBUG_OBJECT (bus, "unset bus flushing");
472 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
475 GST_OBJECT_UNLOCK (bus);
477 g_list_free_full (message_list, (GDestroyNotify) gst_message_unref);
481 * gst_bus_timed_pop_filtered:
482 * @bus: a #GstBus to pop from
483 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
484 * @types: message types to take into account, GST_MESSAGE_ANY for any type
486 * Get a message from the bus whose type matches the message type mask @types,
487 * waiting up to the specified timeout (and discarding any messages that do not
488 * match the mask provided).
490 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
491 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
492 * matching message was posted on the bus.
494 * Returns: (transfer full) (nullable): a #GstMessage matching the
495 * filter in @types, or %NULL if no matching message was found on
496 * the bus until the timeout expired. The message is taken from
497 * the bus and needs to be unreffed with gst_message_unref() after
503 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
504 GstMessageType types)
508 gboolean first_round = TRUE;
509 GstClockTime elapsed = 0;
511 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
512 g_return_val_if_fail (types != 0, NULL);
513 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
515 g_mutex_lock (&bus->priv->queue_lock);
520 GST_LOG_OBJECT (bus, "have %d messages",
521 gst_atomic_queue_length (bus->priv->queue));
523 while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
524 if (bus->priv->poll) {
525 while (!gst_poll_read_control (bus->priv->poll)) {
526 if (errno == EWOULDBLOCK) {
527 /* Retry, this can happen if pushing to the queue has finished,
528 * popping here succeeded but writing control did not finish
529 * before we got to this line. */
530 /* Give other threads the chance to do something */
534 /* This is a real error and means that either the bus is in an
535 * inconsistent state, or the GstPoll is invalid. GstPoll already
536 * prints a critical warning about this, no need to do that again
543 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
544 message, GST_MESSAGE_TYPE_NAME (message),
545 GST_MESSAGE_SRC_NAME (message), (guint) types);
546 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
547 /* Extra check to ensure extended types don't get matched unless
549 if ((!GST_MESSAGE_TYPE_IS_EXTENDED (message))
550 || (types & GST_MESSAGE_EXTENDED)) {
551 /* exit the loop, we have a message */
556 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
557 gst_message_unref (message);
561 /* no need to wait, exit loop */
565 else if (timeout != GST_CLOCK_TIME_NONE) {
567 g_get_current_time (&then);
570 g_get_current_time (&now);
572 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
574 if (elapsed > timeout)
579 /* only here in timeout case */
580 g_assert (bus->priv->poll);
581 g_mutex_unlock (&bus->priv->queue_lock);
582 ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
583 g_mutex_lock (&bus->priv->queue_lock);
586 GST_INFO_OBJECT (bus, "timed out, breaking loop");
589 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
595 g_mutex_unlock (&bus->priv->queue_lock);
603 * @bus: a #GstBus to pop
604 * @timeout: a timeout
606 * Get a message from the bus, waiting up to the specified timeout.
608 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
609 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
612 * Returns: (transfer full) (nullable): the #GstMessage that is on the
613 * bus after the specified timeout or %NULL if the bus is empty
614 * after the timeout expired. The message is taken from the bus
615 * and needs to be unreffed with gst_message_unref() after usage.
620 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
622 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
624 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
628 * gst_bus_pop_filtered:
629 * @bus: a #GstBus to pop
630 * @types: message types to take into account
632 * Get a message matching @type from the bus. Will discard all messages on
633 * the bus that do not match @type and that have been posted before the first
634 * message that does match @type. If there is no message matching @type on
635 * the bus, all messages will be discarded. It is not possible to use message
636 * enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
638 * Returns: (transfer full) (nullable): the next #GstMessage matching
639 * @type that is on the bus, or %NULL if the bus is empty or there
640 * is no message matching @type. The message is taken from the bus
641 * and needs to be unreffed with gst_message_unref() after usage.
646 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
648 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
649 g_return_val_if_fail (types != 0, NULL);
651 return gst_bus_timed_pop_filtered (bus, 0, types);
656 * @bus: a #GstBus to pop
658 * Get a message from the bus.
660 * Returns: (transfer full) (nullable): the #GstMessage that is on the
661 * bus, or %NULL if the bus is empty. The message is taken from
662 * the bus and needs to be unreffed with gst_message_unref() after
668 gst_bus_pop (GstBus * bus)
670 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
672 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
679 * Peek the message on the top of the bus' queue. The message will remain
680 * on the bus' message queue. A reference is returned, and needs to be unreffed
683 * Returns: (transfer full) (nullable): the #GstMessage that is on the
684 * bus, or %NULL if the bus is empty.
689 gst_bus_peek (GstBus * bus)
693 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
695 g_mutex_lock (&bus->priv->queue_lock);
696 message = gst_atomic_queue_peek (bus->priv->queue);
698 gst_message_ref (message);
699 g_mutex_unlock (&bus->priv->queue_lock);
701 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
707 * gst_bus_set_sync_handler:
708 * @bus: a #GstBus to install the handler on
709 * @func: (allow-none): The handler function to install
710 * @user_data: User data that will be sent to the handler function.
711 * @notify: called when @user_data becomes unused
713 * Sets the synchronous handler on the bus. The function will be called
714 * every time a new message is posted on the bus. Note that the function
715 * will be called in the same thread context as the posting object. This
716 * function is usually only called by the creator of the bus. Applications
717 * should handle messages asynchronously using the gst_bus watch and poll
720 * You cannot replace an existing sync_handler. You can pass %NULL to this
721 * function, which will clear the existing handler.
724 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func,
725 gpointer user_data, GDestroyNotify notify)
727 GDestroyNotify old_notify;
729 g_return_if_fail (GST_IS_BUS (bus));
731 GST_OBJECT_LOCK (bus);
732 /* Assert if the user attempts to replace an existing sync_handler,
733 * other than to clear it */
734 if (func != NULL && bus->priv->sync_handler != NULL)
737 if ((old_notify = bus->priv->sync_handler_notify)) {
738 gpointer old_data = bus->priv->sync_handler_data;
740 bus->priv->sync_handler_data = NULL;
741 bus->priv->sync_handler_notify = NULL;
742 GST_OBJECT_UNLOCK (bus);
744 old_notify (old_data);
746 GST_OBJECT_LOCK (bus);
748 bus->priv->sync_handler = func;
749 bus->priv->sync_handler_data = user_data;
750 bus->priv->sync_handler_notify = notify;
751 GST_OBJECT_UNLOCK (bus);
757 GST_OBJECT_UNLOCK (bus);
758 g_warning ("cannot replace existing sync handler");
763 /* GSource for the bus
772 gst_bus_source_prepare (GSource * source, gint * timeout)
779 gst_bus_source_check (GSource * source)
781 GstBusSource *bsrc = (GstBusSource *) source;
783 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
787 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
790 GstBusFunc handler = (GstBusFunc) callback;
791 GstBusSource *bsource = (GstBusSource *) source;
796 g_return_val_if_fail (bsource != NULL, FALSE);
800 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
802 message = gst_bus_pop (bus);
804 /* The message queue might be empty if some other thread or callback set
805 * the bus to flushing between check/prepare and dispatch */
806 if (G_UNLIKELY (message == NULL))
812 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
815 keep = handler (bus, message, user_data);
816 gst_message_unref (message);
818 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
824 g_warning ("GstBus watch dispatched without callback\n"
825 "You must call g_source_set_callback().");
826 gst_message_unref (message);
832 gst_bus_source_finalize (GSource * source)
834 GstBusSource *bsource = (GstBusSource *) source;
839 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
841 GST_OBJECT_LOCK (bus);
842 if (bus->priv->signal_watch == source)
843 bus->priv->signal_watch = NULL;
844 GST_OBJECT_UNLOCK (bus);
846 gst_object_unref (bsource->bus);
850 static GSourceFuncs gst_bus_source_funcs = {
851 gst_bus_source_prepare,
852 gst_bus_source_check,
853 gst_bus_source_dispatch,
854 gst_bus_source_finalize
858 * gst_bus_create_watch:
859 * @bus: a #GstBus to create the watch for
861 * Create watch for this bus. The GSource will be dispatched whenever
862 * a message is on the bus. After the GSource is dispatched, the
863 * message is popped off the bus and unreffed.
865 * Returns: (transfer full): a #GSource that can be added to a mainloop.
868 gst_bus_create_watch (GstBus * bus)
870 GstBusSource *source;
872 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
873 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
875 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
876 sizeof (GstBusSource));
878 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
880 source->bus = gst_object_ref (bus);
881 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
883 return (GSource *) source;
886 /* must be called with the bus OBJECT LOCK */
888 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
889 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
895 if (bus->priv->signal_watch) {
896 GST_ERROR_OBJECT (bus,
897 "Tried to add new watch while one was already there");
901 source = gst_bus_create_watch (bus);
903 g_critical ("Creating bus watch failed");
907 if (priority != G_PRIORITY_DEFAULT)
908 g_source_set_priority (source, priority);
910 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
912 ctx = g_main_context_get_thread_default ();
913 id = g_source_attach (source, ctx);
914 g_source_unref (source);
917 bus->priv->signal_watch = source;
920 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
925 * gst_bus_add_watch_full: (rename-to gst_bus_add_watch)
926 * @bus: a #GstBus to create the watch for.
927 * @priority: The priority of the watch.
928 * @func: A function to call when a message is received.
929 * @user_data: user data passed to @func.
930 * @notify: the function to call when the source is removed.
932 * Adds a bus watch to the default main context with the given @priority (e.g.
933 * %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
934 * context set up using g_main_context_push_thread_default() (before
935 * one had to create a bus watch source and attach it to the desired main
936 * context 'manually').
938 * This function is used to receive asynchronous messages in the main loop.
939 * There can only be a single bus watch per bus, you must remove it before you
942 * The bus watch will only work if a GLib main loop is being run.
944 * When @func is called, the message belongs to the caller; if you want to
945 * keep a copy of it, call gst_message_ref() before leaving @func.
947 * The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
948 * from @func. If the watch was added to the default main context it is also
949 * possible to remove the watch using g_source_remove().
953 * Returns: The event source id or 0 if @bus already got an event source.
956 gst_bus_add_watch_full (GstBus * bus, gint priority,
957 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
961 g_return_val_if_fail (GST_IS_BUS (bus), 0);
963 GST_OBJECT_LOCK (bus);
964 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
965 GST_OBJECT_UNLOCK (bus);
971 * gst_bus_add_watch: (skip)
972 * @bus: a #GstBus to create the watch for
973 * @func: A function to call when a message is received.
974 * @user_data: user data passed to @func.
976 * Adds a bus watch to the default main context with the default priority
977 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default main
978 * context set up using g_main_context_push_thread_default() (before
979 * one had to create a bus watch source and attach it to the desired main
980 * context 'manually').
982 * This function is used to receive asynchronous messages in the main loop.
983 * There can only be a single bus watch per bus, you must remove it before you
986 * The bus watch will only work if a GLib main loop is being run.
988 * The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
989 * from @func. If the watch was added to the default main context it is also
990 * possible to remove the watch using g_source_remove().
992 * Returns: The event source id or 0 if @bus already got an event source.
997 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
999 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
1004 * gst_bus_remove_watch:
1005 * @bus: a #GstBus to remove the watch from.
1007 * Removes an installed bus watch from @bus.
1009 * Returns: %TRUE on success or %FALSE if @bus has no event source.
1015 gst_bus_remove_watch (GstBus * bus)
1019 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
1021 GST_OBJECT_LOCK (bus);
1023 if (bus->priv->signal_watch == NULL) {
1024 GST_ERROR_OBJECT (bus, "no bus watch was present");
1028 watch_id = bus->priv->signal_watch;
1030 GST_OBJECT_UNLOCK (bus);
1032 g_source_destroy (watch_id);
1037 GST_OBJECT_UNLOCK (bus);
1046 gboolean source_running;
1047 GstMessageType events;
1048 GstMessage *message;
1052 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
1054 GstMessageType type;
1056 if (!g_main_loop_is_running (poll_data->loop)) {
1057 GST_DEBUG ("mainloop %p not running", poll_data->loop);
1061 type = GST_MESSAGE_TYPE (message);
1063 if (type & poll_data->events) {
1064 g_assert (poll_data->message == NULL);
1065 /* keep ref to message */
1066 poll_data->message = gst_message_ref (message);
1067 GST_DEBUG ("mainloop %p quit", poll_data->loop);
1068 g_main_loop_quit (poll_data->loop);
1070 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
1075 poll_timeout (GstBusPollData * poll_data)
1077 GST_DEBUG ("mainloop %p quit", poll_data->loop);
1078 g_main_loop_quit (poll_data->loop);
1080 /* we don't remove the GSource as this would free our poll_data,
1081 * which we still need */
1086 poll_destroy (GstBusPollData * poll_data, gpointer unused)
1088 poll_data->source_running = FALSE;
1089 if (!poll_data->timeout_id) {
1090 g_main_loop_unref (poll_data->loop);
1091 g_slice_free (GstBusPollData, poll_data);
1096 poll_destroy_timeout (GstBusPollData * poll_data)
1098 poll_data->timeout_id = 0;
1099 if (!poll_data->source_running) {
1100 g_main_loop_unref (poll_data->loop);
1101 g_slice_free (GstBusPollData, poll_data);
1108 * @events: a mask of #GstMessageType, representing the set of message types to
1109 * poll for (note special handling of extended message types below)
1110 * @timeout: the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE to poll
1113 * Poll the bus for messages. Will block while waiting for messages to come.
1114 * You can specify a maximum time to poll with the @timeout parameter. If
1115 * @timeout is negative, this function will block indefinitely.
1117 * All messages not in @events will be popped off the bus and will be ignored.
1118 * It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
1121 * Because poll is implemented using the "message" signal enabled by
1122 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1123 * signal to be emitted for every message that poll sees. Thus a "message"
1124 * signal handler will see the same messages that this function sees -- neither
1125 * will steal messages from the other.
1127 * This function will run a main loop from the default main context when
1130 * You should never use this function, since it is pure evil. This is
1131 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1132 * other non-trivial application that uses the GLib main loop. As this function
1133 * runs a GLib main loop, any callback attached to the default GLib main
1134 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1135 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1136 * may do things you do not expect, e.g. destroy the main application window or
1137 * some other resource; change other application state; display a dialog and
1138 * run another main loop until the user clicks it away. In short, using this
1139 * function may add a lot of complexity to your code through unexpected
1140 * re-entrancy and unexpected changes to your application's state.
1142 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1143 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1144 * better handled by setting up an asynchronous bus watch and doing things
1147 * Returns: (transfer full) (nullable): the message that was received,
1148 * or %NULL if the poll timed out. The message is taken from the
1149 * bus and needs to be unreffed with gst_message_unref() after
1153 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTime timeout)
1155 GstBusPollData *poll_data;
1159 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
1161 poll_data = g_slice_new (GstBusPollData);
1162 poll_data->source_running = TRUE;
1163 poll_data->loop = g_main_loop_new (NULL, FALSE);
1164 poll_data->events = events;
1165 poll_data->message = NULL;
1167 if (timeout != GST_CLOCK_TIME_NONE)
1168 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1169 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1170 (GDestroyNotify) poll_destroy_timeout);
1172 poll_data->timeout_id = 0;
1174 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1175 (GClosureNotify) poll_destroy, 0);
1177 /* these can be nested, so it's ok */
1178 gst_bus_add_signal_watch (bus);
1180 GST_DEBUG ("running mainloop %p", poll_data->loop);
1181 g_main_loop_run (poll_data->loop);
1182 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1184 gst_bus_remove_signal_watch (bus);
1187 ret = poll_data->message;
1189 if (poll_data->timeout_id)
1190 g_source_remove (poll_data->timeout_id);
1192 /* poll_data will be freed now */
1193 g_signal_handler_disconnect (bus, id);
1195 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1201 * gst_bus_async_signal_func:
1203 * @message: the #GstMessage received
1206 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1212 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1216 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1217 g_return_val_if_fail (message != NULL, TRUE);
1219 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1221 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1223 /* we never remove this source based on signal emission return values */
1228 * gst_bus_sync_signal_handler:
1230 * @message: the #GstMessage received
1233 * A helper GstBusSyncHandler that can be used to convert all synchronous
1234 * messages into signals.
1236 * Returns: GST_BUS_PASS
1239 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1243 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1244 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1246 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1248 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1250 return GST_BUS_PASS;
1254 * gst_bus_enable_sync_message_emission:
1255 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1257 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1258 * sync handler. This function is here so that code can ensure that they can
1259 * synchronously receive messages without having to affect what the bin's sync
1262 * This function may be called multiple times. To clean up, the caller is
1263 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1264 * as this function is called.
1266 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1267 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1268 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1269 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1270 * comes from the thread of whatever object posted the message; the "message"
1271 * signal is marshalled to the main thread via the main loop.
1276 gst_bus_enable_sync_message_emission (GstBus * bus)
1278 g_return_if_fail (GST_IS_BUS (bus));
1280 GST_OBJECT_LOCK (bus);
1281 bus->priv->num_sync_message_emitters++;
1282 GST_OBJECT_UNLOCK (bus);
1286 * gst_bus_disable_sync_message_emission:
1287 * @bus: a #GstBus on which you previously called
1288 * gst_bus_enable_sync_message_emission()
1290 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1291 * See gst_bus_enable_sync_message_emission() for more information.
1293 * In the event that multiple pieces of code have called
1294 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1295 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1296 * "cancelled" by calling this function. In this way the semantics are exactly
1297 * the same as gst_object_ref() that which calls enable should also call
1303 gst_bus_disable_sync_message_emission (GstBus * bus)
1305 g_return_if_fail (GST_IS_BUS (bus));
1306 g_return_if_fail (bus->priv->num_sync_message_emitters > 0);
1308 GST_OBJECT_LOCK (bus);
1309 bus->priv->num_sync_message_emitters--;
1310 GST_OBJECT_UNLOCK (bus);
1314 * gst_bus_add_signal_watch_full:
1315 * @bus: a #GstBus on which you want to receive the "message" signal
1316 * @priority: The priority of the watch.
1318 * Adds a bus signal watch to the default main context with the given @priority
1319 * (e.g. %G_PRIORITY_DEFAULT). It is also possible to use a non-default main
1320 * context set up using g_main_context_push_thread_default()
1321 * (before one had to create a bus watch source and attach it to the desired
1322 * main context 'manually').
1324 * After calling this statement, the bus will emit the "message" signal for each
1325 * message posted on the bus when the main loop is running.
1327 * This function may be called multiple times. To clean up, the caller is
1328 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1329 * function is called.
1331 * There can only be a single bus watch per bus, you must remove any signal
1332 * watch before you can set another type of watch.
1337 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1339 g_return_if_fail (GST_IS_BUS (bus));
1341 /* I know the callees don't take this lock, so go ahead and abuse it */
1342 GST_OBJECT_LOCK (bus);
1344 if (bus->priv->num_signal_watchers > 0)
1347 /* this should not fail because the counter above takes care of it */
1348 g_assert (!bus->priv->signal_watch);
1350 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1353 if (G_UNLIKELY (!bus->priv->signal_watch))
1358 bus->priv->num_signal_watchers++;
1360 GST_OBJECT_UNLOCK (bus);
1366 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1367 GST_OBJECT_UNLOCK (bus);
1373 * gst_bus_add_signal_watch:
1374 * @bus: a #GstBus on which you want to receive the "message" signal
1376 * Adds a bus signal watch to the default main context with the default priority
1377 * (%G_PRIORITY_DEFAULT). It is also possible to use a non-default
1378 * main context set up using g_main_context_push_thread_default() (before
1379 * one had to create a bus watch source and attach it to the desired main
1380 * context 'manually').
1382 * After calling this statement, the bus will emit the "message" signal for each
1383 * message posted on the bus.
1385 * This function may be called multiple times. To clean up, the caller is
1386 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1387 * function is called.
1392 gst_bus_add_signal_watch (GstBus * bus)
1394 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1398 * gst_bus_remove_signal_watch:
1399 * @bus: a #GstBus you previously added a signal watch to
1401 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1406 gst_bus_remove_signal_watch (GstBus * bus)
1408 GSource *source = NULL;
1410 g_return_if_fail (GST_IS_BUS (bus));
1412 /* I know the callees don't take this lock, so go ahead and abuse it */
1413 GST_OBJECT_LOCK (bus);
1415 if (bus->priv->num_signal_watchers == 0)
1418 bus->priv->num_signal_watchers--;
1420 if (bus->priv->num_signal_watchers > 0)
1423 GST_DEBUG_OBJECT (bus, "removing signal watch %u",
1424 g_source_get_id (bus->priv->signal_watch));
1426 source = bus->priv->signal_watch;
1429 GST_OBJECT_UNLOCK (bus);
1432 g_source_destroy (source);
1439 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1440 GST_OBJECT_UNLOCK (bus);