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., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, 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.
67 * Last reviewed on 2006-03-12 (0.10.5)
70 #include "gst_private.h"
75 #include <sys/types.h>
82 #define GST_CAT_DEFAULT GST_CAT_BUS
92 #define DEFAULT_ENABLE_ASYNC (TRUE)
100 static void gst_bus_dispose (GObject * object);
102 static GstObjectClass *parent_class = NULL;
103 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
105 struct _GstBusPrivate
107 guint num_sync_message_emitters;
110 gboolean enable_async;
115 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
118 gst_bus_set_property (GObject * object,
119 guint prop_id, const GValue * value, GParamSpec * pspec)
121 GstBus *bus = GST_BUS_CAST (object);
124 case PROP_ENABLE_ASYNC:
125 bus->priv->enable_async = g_value_get_boolean (value);
128 G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
134 gst_bus_constructed (GObject * object)
136 GstBus *bus = GST_BUS_CAST (object);
138 if (bus->priv->enable_async) {
139 bus->priv->poll = gst_poll_new_timer ();
140 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
145 gst_bus_class_init (GstBusClass * klass)
147 GObjectClass *gobject_class = (GObjectClass *) klass;
149 parent_class = g_type_class_peek_parent (klass);
151 gobject_class->dispose = gst_bus_dispose;
152 gobject_class->set_property = gst_bus_set_property;
153 gobject_class->constructed = gst_bus_constructed;
155 /* GstBus:enable-async:
157 * Enable async message delivery support for bus watches,
158 * gst_bus_pop() and similar API. Without this only the
159 * synchronous message handlers are called.
161 * This property is used to create the child element buses
166 g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
167 g_param_spec_boolean ("enable-async", "Enable Async",
168 "Enable async message delivery for bus watches and gst_bus_pop()",
169 DEFAULT_ENABLE_ASYNC,
170 G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
173 * GstBus::sync-message:
174 * @bus: the object which received the signal
175 * @message: the message that has been posted synchronously
177 * A message has been posted on the bus. This signal is emitted from the
178 * thread that posted the message so one has to be careful with locking.
180 * This signal will not be emitted by default, you have to set up
181 * gst_bus_sync_signal_handler() as a sync handler if you want this
182 * signal to be emitted when a message is posted on the bus, like this:
184 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
187 gst_bus_signals[SYNC_MESSAGE] =
188 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
189 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
190 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
191 g_cclosure_marshal_VOID__BOXED, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
195 * @bus: the object which received the signal
196 * @message: the message that has been posted asynchronously
198 * A message has been posted on the bus. This signal is emitted from a
199 * GSource added to the mainloop. this signal will only be emitted when
200 * there is a mainloop running.
202 gst_bus_signals[ASYNC_MESSAGE] =
203 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
204 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
205 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
206 g_cclosure_marshal_VOID__BOXED, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
208 g_type_class_add_private (klass, sizeof (GstBusPrivate));
212 gst_bus_init (GstBus * bus)
214 bus->queue = gst_atomic_queue_new (32);
215 bus->queue_lock = g_mutex_new ();
217 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
218 bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
220 GST_DEBUG_OBJECT (bus, "created");
224 gst_bus_dispose (GObject * object)
226 GstBus *bus = GST_BUS (object);
231 g_mutex_lock (bus->queue_lock);
233 message = gst_atomic_queue_pop (bus->queue);
235 gst_message_unref (message);
236 } while (message != NULL);
237 gst_atomic_queue_unref (bus->queue);
239 g_mutex_unlock (bus->queue_lock);
240 g_mutex_free (bus->queue_lock);
241 bus->queue_lock = NULL;
244 gst_poll_free (bus->priv->poll);
245 bus->priv->poll = NULL;
248 G_OBJECT_CLASS (parent_class)->dispose (object);
254 * Creates a new #GstBus instance.
256 * Returns: (transfer full): a new #GstBus instance
263 result = g_object_newv (gst_bus_get_type (), 0, NULL);
264 GST_DEBUG_OBJECT (result, "created new bus");
271 * @bus: a #GstBus to post on
272 * @message: (transfer full): the #GstMessage to post
274 * Post a message on the given bus. Ownership of the message
275 * is taken by the bus.
277 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
282 gst_bus_post (GstBus * bus, GstMessage * message)
284 GstBusSyncReply reply = GST_BUS_PASS;
285 GstBusSyncHandler handler;
286 gboolean emit_sync_message;
287 gpointer handler_data;
289 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
290 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
292 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus, type %s, %" GST_PTR_FORMAT
293 " from source %" GST_PTR_FORMAT,
294 message, GST_MESSAGE_TYPE_NAME (message), message->structure,
297 GST_OBJECT_LOCK (bus);
298 /* check if the bus is flushing */
299 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
302 handler = bus->sync_handler;
303 handler_data = bus->sync_handler_data;
304 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
305 GST_OBJECT_UNLOCK (bus);
307 /* first call the sync handler if it is installed */
309 reply = handler (bus, message, handler_data);
311 /* emit sync-message if requested to do so via
312 gst_bus_enable_sync_message_emission. terrible but effective */
313 if (emit_sync_message && reply != GST_BUS_DROP
314 && handler != gst_bus_sync_signal_handler)
315 gst_bus_sync_signal_handler (bus, message, NULL);
317 /* If this is a bus without async message delivery
318 * always drop the message */
319 if (!bus->priv->poll)
320 reply = GST_BUS_DROP;
322 /* now see what we should do with the message */
325 /* drop the message */
326 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
329 /* pass the message to the async queue, refcount passed in the queue */
330 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
331 gst_atomic_queue_push (bus->queue, message);
332 gst_poll_write_control (bus->priv->poll);
333 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
338 /* async delivery, we need a mutex and a cond to block
340 GMutex *lock = g_mutex_new ();
341 GCond *cond = g_cond_new ();
343 GST_MESSAGE_COND (message) = cond;
344 GST_MESSAGE_GET_LOCK (message) = lock;
346 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
348 /* now we lock the message mutex, send the message to the async
349 * queue. When the message is handled by the app and destroyed,
350 * the cond will be signalled and we can continue */
353 gst_atomic_queue_push (bus->queue, message);
354 gst_poll_write_control (bus->priv->poll);
356 /* now block till the message is freed */
357 g_cond_wait (cond, lock);
358 g_mutex_unlock (lock);
360 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
367 g_warning ("invalid return from bus sync handler");
375 GST_DEBUG_OBJECT (bus, "bus is flushing");
376 gst_message_unref (message);
377 GST_OBJECT_UNLOCK (bus);
384 * gst_bus_have_pending:
385 * @bus: a #GstBus to check
387 * Check if there are pending messages on the bus that
390 * Returns: TRUE if there are messages on the bus to be handled, FALSE
396 gst_bus_have_pending (GstBus * bus)
400 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
402 /* see if there is a message on the bus */
403 result = gst_atomic_queue_length (bus->queue) != 0;
409 * gst_bus_set_flushing:
411 * @flushing: whether or not to flush the bus
413 * If @flushing, flush out and unref any messages queued in the bus. Releases
414 * references to the message origin objects. Will flush future messages until
415 * gst_bus_set_flushing() sets @flushing to #FALSE.
420 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
424 GST_OBJECT_LOCK (bus);
427 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
429 GST_DEBUG_OBJECT (bus, "set bus flushing");
431 while ((message = gst_bus_pop (bus)))
432 gst_message_unref (message);
434 GST_DEBUG_OBJECT (bus, "unset bus flushing");
435 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
438 GST_OBJECT_UNLOCK (bus);
442 * gst_bus_timed_pop_filtered:
443 * @bus: a #GstBus to pop from
444 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
445 * @types: message types to take into account, GST_MESSAGE_ANY for any type
447 * Get a message from the bus whose type matches the message type mask @types,
448 * waiting up to the specified timeout (and discarding any messages that do not
449 * match the mask provided).
451 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
452 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
453 * matching message was posted on the bus.
455 * Returns: (transfer full): a #GstMessage matching the filter in @types,
456 * or NULL if no matching message was found on the bus until the timeout
457 * expired. The message is taken from the bus and needs to be unreffed
458 * with gst_message_unref() after usage.
465 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
466 GstMessageType types)
470 gboolean first_round = TRUE;
472 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
473 g_return_val_if_fail (types != 0, NULL);
474 g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
476 g_mutex_lock (bus->queue_lock);
481 GST_LOG_OBJECT (bus, "have %d messages",
482 gst_atomic_queue_length (bus->queue));
484 while ((message = gst_atomic_queue_pop (bus->queue))) {
486 gst_poll_read_control (bus->priv->poll);
487 GST_DEBUG_OBJECT (bus, "got message %p, %s, type mask is %u",
488 message, GST_MESSAGE_TYPE_NAME (message), (guint) types);
489 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
490 /* exit the loop, we have a message */
493 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
494 gst_message_unref (message);
499 /* no need to wait, exit loop */
503 else if (timeout != GST_CLOCK_TIME_NONE) {
505 g_get_current_time (&then);
508 GstClockTime elapsed;
510 g_get_current_time (&now);
512 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
513 if (timeout > elapsed)
520 /* only here in timeout case */
521 g_assert (bus->priv->poll);
522 g_mutex_unlock (bus->queue_lock);
523 ret = gst_poll_wait (bus->priv->poll, timeout);
524 g_mutex_lock (bus->queue_lock);
527 GST_INFO_OBJECT (bus, "timed out, breaking loop");
530 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
536 g_mutex_unlock (bus->queue_lock);
544 * @bus: a #GstBus to pop
545 * @timeout: a timeout
547 * Get a message from the bus, waiting up to the specified timeout.
549 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
550 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
553 * Returns: (transfer full): the #GstMessage that is on the bus after the
554 * specified timeout or NULL if the bus is empty after the timeout expired.
555 * The message is taken from the bus and needs to be unreffed with
556 * gst_message_unref() after usage.
563 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
565 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
567 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
571 * gst_bus_pop_filtered:
572 * @bus: a #GstBus to pop
573 * @types: message types to take into account
575 * Get a message matching @type from the bus. Will discard all messages on
576 * the bus that do not match @type and that have been posted before the first
577 * message that does match @type. If there is no message matching @type on
578 * the bus, all messages will be discarded.
580 * Returns: (transfer full): the next #GstMessage matching @type that is on
581 * the bus, or NULL if the bus is empty or there is no message matching
582 * @type. The message is taken from the bus and needs to be unreffed with
583 * gst_message_unref() after usage.
590 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
592 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
593 g_return_val_if_fail (types != 0, NULL);
595 return gst_bus_timed_pop_filtered (bus, 0, types);
600 * @bus: a #GstBus to pop
602 * Get a message from the bus.
604 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
605 * bus is empty. The message is taken from the bus and needs to be unreffed
606 * with gst_message_unref() after usage.
611 gst_bus_pop (GstBus * bus)
613 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
615 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
622 * Peek the message on the top of the bus' queue. The message will remain
623 * on the bus' message queue. A reference is returned, and needs to be unreffed
626 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
632 gst_bus_peek (GstBus * bus)
636 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
638 g_mutex_lock (bus->queue_lock);
639 message = gst_atomic_queue_peek (bus->queue);
641 gst_message_ref (message);
642 g_mutex_unlock (bus->queue_lock);
644 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
650 * gst_bus_set_sync_handler:
651 * @bus: a #GstBus to install the handler on
652 * @func: The handler function to install
653 * @data: User data that will be sent to the handler function.
655 * Sets the synchronous handler on the bus. The function will be called
656 * every time a new message is posted on the bus. Note that the function
657 * will be called in the same thread context as the posting object. This
658 * function is usually only called by the creator of the bus. Applications
659 * should handle messages asynchronously using the gst_bus watch and poll
662 * You cannot replace an existing sync_handler. You can pass NULL to this
663 * function, which will clear the existing handler.
666 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
668 g_return_if_fail (GST_IS_BUS (bus));
670 GST_OBJECT_LOCK (bus);
672 /* Assert if the user attempts to replace an existing sync_handler,
673 * other than to clear it */
674 if (func != NULL && bus->sync_handler != NULL)
677 bus->sync_handler = func;
678 bus->sync_handler_data = data;
679 GST_OBJECT_UNLOCK (bus);
685 GST_OBJECT_UNLOCK (bus);
686 g_warning ("cannot replace existing sync handler");
691 /* GSource for the bus
700 gst_bus_source_prepare (GSource * source, gint * timeout)
707 gst_bus_source_check (GSource * source)
709 GstBusSource *bsrc = (GstBusSource *) source;
711 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
715 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
718 GstBusFunc handler = (GstBusFunc) callback;
719 GstBusSource *bsource = (GstBusSource *) source;
724 g_return_val_if_fail (bsource != NULL, FALSE);
728 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
730 message = gst_bus_pop (bus);
732 /* The message queue might be empty if some other thread or callback set
733 * the bus to flushing between check/prepare and dispatch */
734 if (G_UNLIKELY (message == NULL))
740 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %p", source, message);
742 keep = handler (bus, message, user_data);
743 gst_message_unref (message);
745 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
751 g_warning ("GstBus watch dispatched without callback\n"
752 "You must call g_source_set_callback().");
753 gst_message_unref (message);
759 gst_bus_source_finalize (GSource * source)
761 GstBusSource *bsource = (GstBusSource *) source;
766 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
768 GST_OBJECT_LOCK (bus);
769 if (bus->priv->watch_id == source)
770 bus->priv->watch_id = NULL;
771 GST_OBJECT_UNLOCK (bus);
773 gst_object_unref (bsource->bus);
777 static GSourceFuncs gst_bus_source_funcs = {
778 gst_bus_source_prepare,
779 gst_bus_source_check,
780 gst_bus_source_dispatch,
781 gst_bus_source_finalize
785 * gst_bus_create_watch:
786 * @bus: a #GstBus to create the watch for
788 * Create watch for this bus. The GSource will be dispatched whenever
789 * a message is on the bus. After the GSource is dispatched, the
790 * message is popped off the bus and unreffed.
792 * Returns: (transfer full): a #GSource that can be added to a mainloop.
795 gst_bus_create_watch (GstBus * bus)
797 GstBusSource *source;
799 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
800 g_return_val_if_fail (bus->priv->poll != NULL, NULL);
802 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
803 sizeof (GstBusSource));
804 source->bus = gst_object_ref (bus);
805 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
807 return (GSource *) source;
810 /* must be called with the bus OBJECT LOCK */
812 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
813 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
819 if (bus->priv->watch_id) {
820 GST_ERROR_OBJECT (bus,
821 "Tried to add new watch while one was already there");
825 source = gst_bus_create_watch (bus);
827 if (priority != G_PRIORITY_DEFAULT)
828 g_source_set_priority (source, priority);
830 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
832 ctx = g_main_context_get_thread_default ();
833 id = g_source_attach (source, ctx);
834 g_source_unref (source);
837 bus->priv->watch_id = source;
840 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
845 * gst_bus_add_watch_full:
846 * @bus: a #GstBus to create the watch for.
847 * @priority: The priority of the watch.
848 * @func: A function to call when a message is received.
849 * @user_data: user data passed to @func.
850 * @notify: the function to call when the source is removed.
852 * Adds a bus watch to the default main context with the given @priority (e.g.
853 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
854 * main context set up using g_main_context_push_thread_default() (before
855 * one had to create a bus watch source and attach it to the desired main
856 * context 'manually').
858 * This function is used to receive asynchronous messages in the main loop.
859 * There can only be a single bus watch per bus, you must remove it before you
862 * When @func is called, the message belongs to the caller; if you want to
863 * keep a copy of it, call gst_message_ref() before leaving @func.
865 * The watch can be removed using g_source_remove() or by returning FALSE
868 * Returns: The event source id.
873 gst_bus_add_watch_full (GstBus * bus, gint priority,
874 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
878 g_return_val_if_fail (GST_IS_BUS (bus), 0);
880 GST_OBJECT_LOCK (bus);
881 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
882 GST_OBJECT_UNLOCK (bus);
889 * @bus: a #GstBus to create the watch for
890 * @func: A function to call when a message is received.
891 * @user_data: user data passed to @func.
893 * Adds a bus watch to the default main context with the default priority
894 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
895 * main context set up using g_main_context_push_thread_default() (before
896 * one had to create a bus watch source and attach it to the desired main
897 * context 'manually').
899 * This function is used to receive asynchronous messages in the main loop.
900 * There can only be a single bus watch per bus, you must remove it before you
903 * The watch can be removed using g_source_remove() or by returning FALSE
906 * Returns: The event source id.
911 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
913 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
921 gboolean source_running;
922 GstMessageType events;
927 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
931 if (!g_main_loop_is_running (poll_data->loop)) {
932 GST_DEBUG ("mainloop %p not running", poll_data->loop);
936 type = GST_MESSAGE_TYPE (message);
938 if (type & poll_data->events) {
939 g_assert (poll_data->message == NULL);
940 /* keep ref to message */
941 poll_data->message = gst_message_ref (message);
942 GST_DEBUG ("mainloop %p quit", poll_data->loop);
943 g_main_loop_quit (poll_data->loop);
945 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
950 poll_timeout (GstBusPollData * poll_data)
952 GST_DEBUG ("mainloop %p quit", poll_data->loop);
953 g_main_loop_quit (poll_data->loop);
955 /* we don't remove the GSource as this would free our poll_data,
956 * which we still need */
961 poll_destroy (GstBusPollData * poll_data, gpointer unused)
963 poll_data->source_running = FALSE;
964 if (!poll_data->timeout_id) {
965 g_main_loop_unref (poll_data->loop);
966 g_slice_free (GstBusPollData, poll_data);
971 poll_destroy_timeout (GstBusPollData * poll_data)
973 poll_data->timeout_id = 0;
974 if (!poll_data->source_running) {
975 g_main_loop_unref (poll_data->loop);
976 g_slice_free (GstBusPollData, poll_data);
983 * @events: a mask of #GstMessageType, representing the set of message types to
985 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
988 * Poll the bus for messages. Will block while waiting for messages to come.
989 * You can specify a maximum time to poll with the @timeout parameter. If
990 * @timeout is negative, this function will block indefinitely.
992 * All messages not in @events will be popped off the bus and will be ignored.
994 * Because poll is implemented using the "message" signal enabled by
995 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
996 * signal to be emitted for every message that poll sees. Thus a "message"
997 * signal handler will see the same messages that this function sees -- neither
998 * will steal messages from the other.
1000 * This function will run a main loop from the default main context when
1003 * You should never use this function, since it is pure evil. This is
1004 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1005 * other non-trivial application that uses the GLib main loop. As this function
1006 * runs a GLib main loop, any callback attached to the default GLib main
1007 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1008 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1009 * may do things you do not expect, e.g. destroy the main application window or
1010 * some other resource; change other application state; display a dialog and
1011 * run another main loop until the user clicks it away. In short, using this
1012 * function may add a lot of complexity to your code through unexpected
1013 * re-entrancy and unexpected changes to your application's state.
1015 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1016 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1017 * better handled by setting up an asynchronous bus watch and doing things
1020 * Returns: (transfer full): the message that was received, or NULL if the
1021 * poll timed out. The message is taken from the bus and needs to be
1022 * unreffed with gst_message_unref() after usage.
1025 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1027 GstBusPollData *poll_data;
1031 poll_data = g_slice_new (GstBusPollData);
1032 poll_data->source_running = TRUE;
1033 poll_data->loop = g_main_loop_new (NULL, FALSE);
1034 poll_data->events = events;
1035 poll_data->message = NULL;
1038 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1039 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1040 (GDestroyNotify) poll_destroy_timeout);
1042 poll_data->timeout_id = 0;
1044 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1045 (GClosureNotify) poll_destroy, 0);
1047 /* these can be nested, so it's ok */
1048 gst_bus_add_signal_watch (bus);
1050 GST_DEBUG ("running mainloop %p", poll_data->loop);
1051 g_main_loop_run (poll_data->loop);
1052 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1054 gst_bus_remove_signal_watch (bus);
1057 ret = poll_data->message;
1059 if (poll_data->timeout_id)
1060 g_source_remove (poll_data->timeout_id);
1062 /* poll_data will be freed now */
1063 g_signal_handler_disconnect (bus, id);
1065 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1071 * gst_bus_async_signal_func:
1073 * @message: the #GstMessage received
1076 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1082 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1086 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1087 g_return_val_if_fail (message != NULL, TRUE);
1089 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1091 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1093 /* we never remove this source based on signal emission return values */
1098 * gst_bus_sync_signal_handler:
1100 * @message: the #GstMessage received
1103 * A helper GstBusSyncHandler that can be used to convert all synchronous
1104 * messages into signals.
1106 * Returns: GST_BUS_PASS
1109 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1113 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1114 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1116 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1118 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1120 return GST_BUS_PASS;
1124 * gst_bus_enable_sync_message_emission:
1125 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1127 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1128 * sync handler. This function is here so that code can ensure that they can
1129 * synchronously receive messages without having to affect what the bin's sync
1132 * This function may be called multiple times. To clean up, the caller is
1133 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1134 * as this function is called.
1136 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1137 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1138 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1139 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1140 * comes from the thread of whatever object posted the message; the "message"
1141 * signal is marshalled to the main thread via the main loop.
1146 gst_bus_enable_sync_message_emission (GstBus * bus)
1148 g_return_if_fail (GST_IS_BUS (bus));
1150 GST_OBJECT_LOCK (bus);
1151 bus->priv->num_sync_message_emitters++;
1152 GST_OBJECT_UNLOCK (bus);
1156 * gst_bus_disable_sync_message_emission:
1157 * @bus: a #GstBus on which you previously called
1158 * gst_bus_enable_sync_message_emission()
1160 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1161 * See gst_bus_enable_sync_message_emission() for more information.
1163 * In the event that multiple pieces of code have called
1164 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1165 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1166 * "cancelled" by calling this function. In this way the semantics are exactly
1167 * the same as gst_object_ref() that which calls enable should also call
1173 gst_bus_disable_sync_message_emission (GstBus * bus)
1175 g_return_if_fail (GST_IS_BUS (bus));
1176 g_return_if_fail (bus->num_signal_watchers == 0);
1178 GST_OBJECT_LOCK (bus);
1179 bus->priv->num_sync_message_emitters--;
1180 GST_OBJECT_UNLOCK (bus);
1184 * gst_bus_add_signal_watch_full:
1185 * @bus: a #GstBus on which you want to receive the "message" signal
1186 * @priority: The priority of the watch.
1188 * Adds a bus signal watch to the default main context with the given @priority
1189 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1190 * non-default main context set up using g_main_context_push_thread_default()
1191 * (before one had to create a bus watch source and attach it to the desired
1192 * main context 'manually').
1194 * After calling this statement, the bus will emit the "message" signal for each
1195 * message posted on the bus when the main loop is running.
1197 * This function may be called multiple times. To clean up, the caller is
1198 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1199 * function is called.
1201 * There can only be a single bus watch per bus, you most remove all signal watch
1202 * before you can set another type of watch.
1207 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1209 g_return_if_fail (GST_IS_BUS (bus));
1211 /* I know the callees don't take this lock, so go ahead and abuse it */
1212 GST_OBJECT_LOCK (bus);
1214 if (bus->num_signal_watchers > 0)
1217 /* this should not fail because the counter above takes care of it */
1218 g_assert (bus->signal_watch_id == 0);
1220 bus->signal_watch_id =
1221 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1224 if (G_UNLIKELY (bus->signal_watch_id == 0))
1229 bus->num_signal_watchers++;
1231 GST_OBJECT_UNLOCK (bus);
1237 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1238 GST_OBJECT_UNLOCK (bus);
1244 * gst_bus_add_signal_watch:
1245 * @bus: a #GstBus on which you want to receive the "message" signal
1247 * Adds a bus signal watch to the default main context with the default priority
1248 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1249 * main context set up using g_main_context_push_thread_default() (before
1250 * one had to create a bus watch source and attach it to the desired main
1251 * context 'manually').
1253 * After calling this statement, the bus will emit the "message" signal for each
1254 * message posted on the bus.
1256 * This function may be called multiple times. To clean up, the caller is
1257 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1258 * function is called.
1263 gst_bus_add_signal_watch (GstBus * bus)
1265 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1269 * gst_bus_remove_signal_watch:
1270 * @bus: a #GstBus you previously added a signal watch to
1272 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1277 gst_bus_remove_signal_watch (GstBus * bus)
1281 g_return_if_fail (GST_IS_BUS (bus));
1283 /* I know the callees don't take this lock, so go ahead and abuse it */
1284 GST_OBJECT_LOCK (bus);
1286 if (bus->num_signal_watchers == 0)
1289 bus->num_signal_watchers--;
1291 if (bus->num_signal_watchers > 0)
1294 id = bus->signal_watch_id;
1295 bus->signal_watch_id = 0;
1297 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1300 GST_OBJECT_UNLOCK (bus);
1303 g_source_remove (id);
1310 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1311 GST_OBJECT_UNLOCK (bus);