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 static void gst_bus_dispose (GObject * object);
94 static GstObjectClass *parent_class = NULL;
95 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
99 guint num_sync_message_emitters;
107 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
109 /* fixme: do something about this */
111 marshal_VOID__MINIOBJECT (GClosure * closure, GValue * return_value,
112 guint n_param_values, const GValue * param_values, gpointer invocation_hint,
113 gpointer marshal_data)
115 typedef void (*marshalfunc_VOID__MINIOBJECT) (gpointer obj, gpointer arg1,
117 register marshalfunc_VOID__MINIOBJECT callback;
118 register GCClosure *cc = (GCClosure *) closure;
119 register gpointer data1, data2;
121 g_return_if_fail (n_param_values == 2);
123 if (G_CCLOSURE_SWAP_DATA (closure)) {
124 data1 = closure->data;
125 data2 = g_value_peek_pointer (param_values + 0);
127 data1 = g_value_peek_pointer (param_values + 0);
128 data2 = closure->data;
131 (marshalfunc_VOID__MINIOBJECT) (marshal_data ? marshal_data :
134 callback (data1, gst_value_get_mini_object (param_values + 1), data2);
138 gst_bus_class_init (GstBusClass * klass)
140 GObjectClass *gobject_class = (GObjectClass *) klass;
142 parent_class = g_type_class_peek_parent (klass);
144 gobject_class->dispose = gst_bus_dispose;
147 * GstBus::sync-message:
148 * @bus: the object which received the signal
149 * @message: the message that has been posted synchronously
151 * A message has been posted on the bus. This signal is emitted from the
152 * thread that posted the message so one has to be careful with locking.
154 * This signal will not be emitted by default, you have to set up
155 * gst_bus_sync_signal_handler() as a sync handler if you want this
156 * signal to be emitted when a message is posted on the bus, like this:
158 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
161 gst_bus_signals[SYNC_MESSAGE] =
162 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
163 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
164 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
165 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
169 * @bus: the object which received the signal
170 * @message: the message that has been posted asynchronously
172 * A message has been posted on the bus. This signal is emitted from a
173 * GSource added to the mainloop. this signal will only be emitted when
174 * there is a mainloop running.
176 gst_bus_signals[ASYNC_MESSAGE] =
177 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
178 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
179 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
180 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
182 g_type_class_add_private (klass, sizeof (GstBusPrivate));
186 gst_bus_init (GstBus * bus)
188 bus->queue = gst_atomic_queue_new (32);
189 bus->queue_lock = g_mutex_new ();
191 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
192 bus->priv->queue_cond = g_cond_new ();
194 bus->priv->poll = gst_poll_new_timer ();
195 gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
197 GST_DEBUG_OBJECT (bus, "created");
201 gst_bus_dispose (GObject * object)
203 GstBus *bus = GST_BUS (object);
208 g_mutex_lock (bus->queue_lock);
210 message = gst_atomic_queue_pop (bus->queue);
212 gst_message_unref (message);
213 } while (message != NULL);
214 gst_atomic_queue_unref (bus->queue);
216 g_mutex_unlock (bus->queue_lock);
217 g_mutex_free (bus->queue_lock);
218 bus->queue_lock = NULL;
219 g_cond_free (bus->priv->queue_cond);
220 bus->priv->queue_cond = NULL;
222 gst_poll_free (bus->priv->poll);
225 G_OBJECT_CLASS (parent_class)->dispose (object);
231 * Creates a new #GstBus instance.
233 * Returns: (transfer full): a new #GstBus instance
240 result = g_object_newv (gst_bus_get_type (), 0, NULL);
241 GST_DEBUG_OBJECT (result, "created new bus");
248 * @bus: a #GstBus to post on
249 * @message: (transfer full): the #GstMessage to post
251 * Post a message on the given bus. Ownership of the message
252 * is taken by the bus.
254 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
259 gst_bus_post (GstBus * bus, GstMessage * message)
261 GstBusSyncReply reply = GST_BUS_PASS;
262 GstBusSyncHandler handler;
263 gboolean emit_sync_message;
264 gpointer handler_data;
266 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
267 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
269 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus, type %s, %" GST_PTR_FORMAT
270 " from source %" GST_PTR_FORMAT,
271 message, GST_MESSAGE_TYPE_NAME (message), message->structure,
274 GST_OBJECT_LOCK (bus);
275 /* check if the bus is flushing */
276 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
279 handler = bus->sync_handler;
280 handler_data = bus->sync_handler_data;
281 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
282 GST_OBJECT_UNLOCK (bus);
284 /* first call the sync handler if it is installed */
286 reply = handler (bus, message, handler_data);
288 /* emit sync-message if requested to do so via
289 gst_bus_enable_sync_message_emission. terrible but effective */
290 if (emit_sync_message && reply != GST_BUS_DROP
291 && handler != gst_bus_sync_signal_handler)
292 gst_bus_sync_signal_handler (bus, message, NULL);
294 /* now see what we should do with the message */
297 /* drop the message */
298 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
301 /* pass the message to the async queue, refcount passed in the queue */
302 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
303 gst_atomic_queue_push (bus->queue, message);
304 gst_poll_write_control (bus->priv->poll);
305 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
310 /* async delivery, we need a mutex and a cond to block
312 GMutex *lock = g_mutex_new ();
313 GCond *cond = g_cond_new ();
315 GST_MESSAGE_COND (message) = cond;
316 GST_MESSAGE_GET_LOCK (message) = lock;
318 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
320 /* now we lock the message mutex, send the message to the async
321 * queue. When the message is handled by the app and destroyed,
322 * the cond will be signalled and we can continue */
325 gst_atomic_queue_push (bus->queue, message);
326 gst_poll_write_control (bus->priv->poll);
328 /* now block till the message is freed */
329 g_cond_wait (cond, lock);
330 g_mutex_unlock (lock);
332 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
339 g_warning ("invalid return from bus sync handler");
347 GST_DEBUG_OBJECT (bus, "bus is flushing");
348 gst_message_unref (message);
349 GST_OBJECT_UNLOCK (bus);
356 * gst_bus_have_pending:
357 * @bus: a #GstBus to check
359 * Check if there are pending messages on the bus that
362 * Returns: TRUE if there are messages on the bus to be handled, FALSE
368 gst_bus_have_pending (GstBus * bus)
372 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
374 /* see if there is a message on the bus */
375 result = gst_atomic_queue_length (bus->queue) != 0;
381 * gst_bus_set_flushing:
383 * @flushing: whether or not to flush the bus
385 * If @flushing, flush out and unref any messages queued in the bus. Releases
386 * references to the message origin objects. Will flush future messages until
387 * gst_bus_set_flushing() sets @flushing to #FALSE.
392 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
396 GST_OBJECT_LOCK (bus);
399 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
401 GST_DEBUG_OBJECT (bus, "set bus flushing");
403 while ((message = gst_bus_pop (bus)))
404 gst_message_unref (message);
406 GST_DEBUG_OBJECT (bus, "unset bus flushing");
407 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
410 GST_OBJECT_UNLOCK (bus);
414 * gst_bus_timed_pop_filtered:
415 * @bus: a #GstBus to pop from
416 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
417 * @types: message types to take into account, GST_MESSAGE_ANY for any type
419 * Get a message from the bus whose type matches the message type mask @types,
420 * waiting up to the specified timeout (and discarding any messages that do not
421 * match the mask provided).
423 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
424 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
425 * matching message was posted on the bus.
427 * Returns: (transfer full): a #GstMessage matching the filter in @types,
428 * or NULL if no matching message was found on the bus until the timeout
429 * expired. The message is taken from the bus and needs to be unreffed
430 * with gst_message_unref() after usage.
437 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
438 GstMessageType types)
442 gboolean first_round = TRUE;
444 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
445 g_return_val_if_fail (types != 0, NULL);
447 g_mutex_lock (bus->queue_lock);
452 GST_LOG_OBJECT (bus, "have %d messages",
453 gst_atomic_queue_length (bus->queue));
455 while ((message = gst_atomic_queue_pop (bus->queue))) {
456 gst_poll_read_control (bus->priv->poll);
457 GST_DEBUG_OBJECT (bus, "got message %p, %s, type mask is %u",
458 message, GST_MESSAGE_TYPE_NAME (message), (guint) types);
459 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
460 /* exit the loop, we have a message */
463 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
464 gst_message_unref (message);
469 /* no need to wait, exit loop */
473 else if (timeout != GST_CLOCK_TIME_NONE) {
475 g_get_current_time (&then);
478 GstClockTime elapsed;
480 g_get_current_time (&now);
482 elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
483 if (timeout > elapsed)
490 g_mutex_unlock (bus->queue_lock);
491 ret = gst_poll_wait (bus->priv->poll, timeout);
492 g_mutex_lock (bus->queue_lock);
495 GST_INFO_OBJECT (bus, "timed out, breaking loop");
498 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
504 g_mutex_unlock (bus->queue_lock);
512 * @bus: a #GstBus to pop
513 * @timeout: a timeout
515 * Get a message from the bus, waiting up to the specified timeout.
517 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
518 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
521 * Returns: (transfer full): the #GstMessage that is on the bus after the
522 * specified timeout or NULL if the bus is empty after the timeout expired.
523 * The message is taken from the bus and needs to be unreffed with
524 * gst_message_unref() after usage.
531 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
533 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
535 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
539 * gst_bus_pop_filtered:
540 * @bus: a #GstBus to pop
541 * @types: message types to take into account
543 * Get a message matching @type from the bus. Will discard all messages on
544 * the bus that do not match @type and that have been posted before the first
545 * message that does match @type. If there is no message matching @type on
546 * the bus, all messages will be discarded.
548 * Returns: (transfer full): the next #GstMessage matching @type that is on
549 * the bus, or NULL if the bus is empty or there is no message matching
550 * @type. The message is taken from the bus and needs to be unreffed with
551 * gst_message_unref() after usage.
558 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
560 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
561 g_return_val_if_fail (types != 0, NULL);
563 return gst_bus_timed_pop_filtered (bus, 0, types);
568 * @bus: a #GstBus to pop
570 * Get a message from the bus.
572 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
573 * bus is empty. The message is taken from the bus and needs to be unreffed
574 * with gst_message_unref() after usage.
579 gst_bus_pop (GstBus * bus)
581 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
583 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
590 * Peek the message on the top of the bus' queue. The message will remain
591 * on the bus' message queue. A reference is returned, and needs to be unreffed
594 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
600 gst_bus_peek (GstBus * bus)
604 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
606 g_mutex_lock (bus->queue_lock);
607 message = gst_atomic_queue_peek (bus->queue);
609 gst_message_ref (message);
610 g_mutex_unlock (bus->queue_lock);
612 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
618 * gst_bus_set_sync_handler:
619 * @bus: a #GstBus to install the handler on
620 * @func: The handler function to install
621 * @data: User data that will be sent to the handler function.
623 * Sets the synchronous handler on the bus. The function will be called
624 * every time a new message is posted on the bus. Note that the function
625 * will be called in the same thread context as the posting object. This
626 * function is usually only called by the creator of the bus. Applications
627 * should handle messages asynchronously using the gst_bus watch and poll
630 * You cannot replace an existing sync_handler. You can pass NULL to this
631 * function, which will clear the existing handler.
634 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
636 g_return_if_fail (GST_IS_BUS (bus));
638 GST_OBJECT_LOCK (bus);
640 /* Assert if the user attempts to replace an existing sync_handler,
641 * other than to clear it */
642 if (func != NULL && bus->sync_handler != NULL)
645 bus->sync_handler = func;
646 bus->sync_handler_data = data;
647 GST_OBJECT_UNLOCK (bus);
653 GST_OBJECT_UNLOCK (bus);
654 g_warning ("cannot replace existing sync handler");
659 /* GSource for the bus
668 gst_bus_source_prepare (GSource * source, gint * timeout)
675 gst_bus_source_check (GSource * source)
677 GstBusSource *bsrc = (GstBusSource *) source;
679 return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
683 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
686 GstBusFunc handler = (GstBusFunc) callback;
687 GstBusSource *bsource = (GstBusSource *) source;
692 g_return_val_if_fail (bsource != NULL, FALSE);
696 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
698 message = gst_bus_pop (bus);
700 /* The message queue might be empty if some other thread or callback set
701 * the bus to flushing between check/prepare and dispatch */
702 if (G_UNLIKELY (message == NULL))
708 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %p", source, message);
710 keep = handler (bus, message, user_data);
711 gst_message_unref (message);
713 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
719 g_warning ("GstBus watch dispatched without callback\n"
720 "You must call g_source_set_callback().");
721 gst_message_unref (message);
727 gst_bus_source_finalize (GSource * source)
729 GstBusSource *bsource = (GstBusSource *) source;
734 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
736 GST_OBJECT_LOCK (bus);
737 if (bus->priv->watch_id == source)
738 bus->priv->watch_id = NULL;
739 GST_OBJECT_UNLOCK (bus);
741 gst_object_unref (bsource->bus);
745 static GSourceFuncs gst_bus_source_funcs = {
746 gst_bus_source_prepare,
747 gst_bus_source_check,
748 gst_bus_source_dispatch,
749 gst_bus_source_finalize
753 * gst_bus_create_watch:
754 * @bus: a #GstBus to create the watch for
756 * Create watch for this bus. The GSource will be dispatched whenever
757 * a message is on the bus. After the GSource is dispatched, the
758 * message is popped off the bus and unreffed.
760 * Returns: (transfer full): a #GSource that can be added to a mainloop.
763 gst_bus_create_watch (GstBus * bus)
765 GstBusSource *source;
767 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
769 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
770 sizeof (GstBusSource));
771 source->bus = gst_object_ref (bus);
772 g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
774 return (GSource *) source;
777 /* must be called with the bus OBJECT LOCK */
779 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
780 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
786 if (bus->priv->watch_id) {
787 GST_ERROR_OBJECT (bus,
788 "Tried to add new watch while one was already there");
792 source = gst_bus_create_watch (bus);
794 if (priority != G_PRIORITY_DEFAULT)
795 g_source_set_priority (source, priority);
797 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
799 ctx = g_main_context_get_thread_default ();
800 id = g_source_attach (source, ctx);
801 g_source_unref (source);
804 bus->priv->watch_id = source;
807 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
812 * gst_bus_add_watch_full:
813 * @bus: a #GstBus to create the watch for.
814 * @priority: The priority of the watch.
815 * @func: A function to call when a message is received.
816 * @user_data: user data passed to @func.
817 * @notify: the function to call when the source is removed.
819 * Adds a bus watch to the default main context with the given @priority (e.g.
820 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
821 * main context set up using g_main_context_push_thread_default() (before
822 * one had to create a bus watch source and attach it to the desired main
823 * context 'manually').
825 * This function is used to receive asynchronous messages in the main loop.
826 * There can only be a single bus watch per bus, you must remove it before you
829 * When @func is called, the message belongs to the caller; if you want to
830 * keep a copy of it, call gst_message_ref() before leaving @func.
832 * The watch can be removed using g_source_remove() or by returning FALSE
835 * Returns: The event source id.
840 gst_bus_add_watch_full (GstBus * bus, gint priority,
841 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
845 g_return_val_if_fail (GST_IS_BUS (bus), 0);
847 GST_OBJECT_LOCK (bus);
848 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
849 GST_OBJECT_UNLOCK (bus);
856 * @bus: a #GstBus to create the watch for
857 * @func: A function to call when a message is received.
858 * @user_data: user data passed to @func.
860 * Adds a bus watch to the default main context with the default priority
861 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
862 * main context set up using g_main_context_push_thread_default() (before
863 * one had to create a bus watch source and attach it to the desired main
864 * context 'manually').
866 * This function is used to receive asynchronous messages in the main loop.
867 * There can only be a single bus watch per bus, you must remove it before you
870 * The watch can be removed using g_source_remove() or by returning FALSE
873 * Returns: The event source id.
878 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
880 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
888 gboolean source_running;
889 GstMessageType events;
894 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
898 if (!g_main_loop_is_running (poll_data->loop)) {
899 GST_DEBUG ("mainloop %p not running", poll_data->loop);
903 type = GST_MESSAGE_TYPE (message);
905 if (type & poll_data->events) {
906 g_assert (poll_data->message == NULL);
907 /* keep ref to message */
908 poll_data->message = gst_message_ref (message);
909 GST_DEBUG ("mainloop %p quit", poll_data->loop);
910 g_main_loop_quit (poll_data->loop);
912 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
917 poll_timeout (GstBusPollData * poll_data)
919 GST_DEBUG ("mainloop %p quit", poll_data->loop);
920 g_main_loop_quit (poll_data->loop);
922 /* we don't remove the GSource as this would free our poll_data,
923 * which we still need */
928 poll_destroy (GstBusPollData * poll_data, gpointer unused)
930 poll_data->source_running = FALSE;
931 if (!poll_data->timeout_id) {
932 g_main_loop_unref (poll_data->loop);
933 g_slice_free (GstBusPollData, poll_data);
938 poll_destroy_timeout (GstBusPollData * poll_data)
940 poll_data->timeout_id = 0;
941 if (!poll_data->source_running) {
942 g_main_loop_unref (poll_data->loop);
943 g_slice_free (GstBusPollData, poll_data);
950 * @events: a mask of #GstMessageType, representing the set of message types to
952 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
955 * Poll the bus for messages. Will block while waiting for messages to come.
956 * You can specify a maximum time to poll with the @timeout parameter. If
957 * @timeout is negative, this function will block indefinitely.
959 * All messages not in @events will be popped off the bus and will be ignored.
961 * Because poll is implemented using the "message" signal enabled by
962 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
963 * signal to be emitted for every message that poll sees. Thus a "message"
964 * signal handler will see the same messages that this function sees -- neither
965 * will steal messages from the other.
967 * This function will run a main loop from the default main context when
970 * You should never use this function, since it is pure evil. This is
971 * especially true for GUI applications based on Gtk+ or Qt, but also for any
972 * other non-trivial application that uses the GLib main loop. As this function
973 * runs a GLib main loop, any callback attached to the default GLib main
974 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
975 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
976 * may do things you do not expect, e.g. destroy the main application window or
977 * some other resource; change other application state; display a dialog and
978 * run another main loop until the user clicks it away. In short, using this
979 * function may add a lot of complexity to your code through unexpected
980 * re-entrancy and unexpected changes to your application's state.
982 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
983 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
984 * better handled by setting up an asynchronous bus watch and doing things
987 * Returns: (transfer full): the message that was received, or NULL if the
988 * poll timed out. The message is taken from the bus and needs to be
989 * unreffed with gst_message_unref() after usage.
992 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
994 GstBusPollData *poll_data;
998 poll_data = g_slice_new (GstBusPollData);
999 poll_data->source_running = TRUE;
1000 poll_data->loop = g_main_loop_new (NULL, FALSE);
1001 poll_data->events = events;
1002 poll_data->message = NULL;
1005 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1006 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1007 (GDestroyNotify) poll_destroy_timeout);
1009 poll_data->timeout_id = 0;
1011 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1012 (GClosureNotify) poll_destroy, 0);
1014 /* these can be nested, so it's ok */
1015 gst_bus_add_signal_watch (bus);
1017 GST_DEBUG ("running mainloop %p", poll_data->loop);
1018 g_main_loop_run (poll_data->loop);
1019 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1021 gst_bus_remove_signal_watch (bus);
1024 ret = poll_data->message;
1026 if (poll_data->timeout_id)
1027 g_source_remove (poll_data->timeout_id);
1029 /* poll_data will be freed now */
1030 g_signal_handler_disconnect (bus, id);
1032 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1038 * gst_bus_async_signal_func:
1040 * @message: the #GstMessage received
1043 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1049 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1053 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1054 g_return_val_if_fail (message != NULL, TRUE);
1056 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1058 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1060 /* we never remove this source based on signal emission return values */
1065 * gst_bus_sync_signal_handler:
1067 * @message: the #GstMessage received
1070 * A helper GstBusSyncHandler that can be used to convert all synchronous
1071 * messages into signals.
1073 * Returns: GST_BUS_PASS
1076 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1080 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1081 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1083 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1085 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1087 return GST_BUS_PASS;
1091 * gst_bus_enable_sync_message_emission:
1092 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1094 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1095 * sync handler. This function is here so that code can ensure that they can
1096 * synchronously receive messages without having to affect what the bin's sync
1099 * This function may be called multiple times. To clean up, the caller is
1100 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1101 * as this function is called.
1103 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1104 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1105 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1106 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1107 * comes from the thread of whatever object posted the message; the "message"
1108 * signal is marshalled to the main thread via the main loop.
1113 gst_bus_enable_sync_message_emission (GstBus * bus)
1115 g_return_if_fail (GST_IS_BUS (bus));
1117 GST_OBJECT_LOCK (bus);
1118 bus->priv->num_sync_message_emitters++;
1119 GST_OBJECT_UNLOCK (bus);
1123 * gst_bus_disable_sync_message_emission:
1124 * @bus: a #GstBus on which you previously called
1125 * gst_bus_enable_sync_message_emission()
1127 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1128 * See gst_bus_enable_sync_message_emission() for more information.
1130 * In the event that multiple pieces of code have called
1131 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1132 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1133 * "cancelled" by calling this function. In this way the semantics are exactly
1134 * the same as gst_object_ref() that which calls enable should also call
1140 gst_bus_disable_sync_message_emission (GstBus * bus)
1142 g_return_if_fail (GST_IS_BUS (bus));
1143 g_return_if_fail (bus->num_signal_watchers == 0);
1145 GST_OBJECT_LOCK (bus);
1146 bus->priv->num_sync_message_emitters--;
1147 GST_OBJECT_UNLOCK (bus);
1151 * gst_bus_add_signal_watch_full:
1152 * @bus: a #GstBus on which you want to receive the "message" signal
1153 * @priority: The priority of the watch.
1155 * Adds a bus signal watch to the default main context with the given @priority
1156 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1157 * non-default main context set up using g_main_context_push_thread_default()
1158 * (before one had to create a bus watch source and attach it to the desired
1159 * main context 'manually').
1161 * After calling this statement, the bus will emit the "message" signal for each
1162 * message posted on the bus when the main loop is running.
1164 * This function may be called multiple times. To clean up, the caller is
1165 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1166 * function is called.
1168 * There can only be a single bus watch per bus, you most remove all signal watch
1169 * before you can set another type of watch.
1174 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1176 g_return_if_fail (GST_IS_BUS (bus));
1178 /* I know the callees don't take this lock, so go ahead and abuse it */
1179 GST_OBJECT_LOCK (bus);
1181 if (bus->num_signal_watchers > 0)
1184 /* this should not fail because the counter above takes care of it */
1185 g_assert (bus->signal_watch_id == 0);
1187 bus->signal_watch_id =
1188 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1191 if (G_UNLIKELY (bus->signal_watch_id == 0))
1196 bus->num_signal_watchers++;
1198 GST_OBJECT_UNLOCK (bus);
1204 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1205 GST_OBJECT_UNLOCK (bus);
1211 * gst_bus_add_signal_watch:
1212 * @bus: a #GstBus on which you want to receive the "message" signal
1214 * Adds a bus signal watch to the default main context with the default priority
1215 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1216 * main context set up using g_main_context_push_thread_default() (before
1217 * one had to create a bus watch source and attach it to the desired main
1218 * context 'manually').
1220 * After calling this statement, the bus will emit the "message" signal for each
1221 * message posted on the bus.
1223 * This function may be called multiple times. To clean up, the caller is
1224 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1225 * function is called.
1230 gst_bus_add_signal_watch (GstBus * bus)
1232 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1236 * gst_bus_remove_signal_watch:
1237 * @bus: a #GstBus you previously added a signal watch to
1239 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1244 gst_bus_remove_signal_watch (GstBus * bus)
1248 g_return_if_fail (GST_IS_BUS (bus));
1250 /* I know the callees don't take this lock, so go ahead and abuse it */
1251 GST_OBJECT_LOCK (bus);
1253 if (bus->num_signal_watchers == 0)
1256 bus->num_signal_watchers--;
1258 if (bus->num_signal_watchers > 0)
1261 id = bus->signal_watch_id;
1262 bus->signal_watch_id = 0;
1264 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1267 GST_OBJECT_UNLOCK (bus);
1270 g_source_remove (id);
1277 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1278 GST_OBJECT_UNLOCK (bus);