42c66def54520ce2e021c2b575aaac25a4ce50e0
1 /* GStreamer
2 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
3 *
4 * gstbus.c: GstBus subsystem
5 *
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.
10 *
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.
15 *
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.
20 */
22 /**
23 * SECTION:gstbus
24 * @short_description: Asynchronous message bus subsystem
25 * @see_also: #GstMessage, #GstElement
26 *
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
29 * application.
30 *
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.
35 *
36 * The GstBus provides support for #GSource based notifications. This makes it
37 * possible to handle the delivery in the glib mainloop.
38 *
39 * The #GSource callback function gst_bus_async_signal_func() can be used to
40 * convert all bus messages into signal emissions.
41 *
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.
45 *
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.
55 *
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.
61 *
62 * Every #GstPipeline has one bus.
63 *
64 * Note that a #GstPipeline will set its bus into flushing state when changing
65 * from READY to NULL state.
66 *
67 * Last reviewed on 2006-03-12 (0.10.5)
68 */
70 #include "gst_private.h"
71 #include <errno.h>
72 #ifdef HAVE_UNISTD_H
73 # include <unistd.h>
74 #endif
75 #include <sys/types.h>
77 #include "gstinfo.h"
79 #include "gstbus.h"
81 #define GST_CAT_DEFAULT GST_CAT_BUS
82 /* bus signals */
83 enum
84 {
85 SYNC_MESSAGE,
86 ASYNC_MESSAGE,
87 /* add more above */
88 LAST_SIGNAL
89 };
91 static void gst_bus_dispose (GObject * object);
93 static void gst_bus_set_main_context (GstBus * bus, GMainContext * ctx);
95 static GstObjectClass *parent_class = NULL;
96 static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
98 struct _GstBusPrivate
99 {
100 guint num_sync_message_emitters;
101 GCond *queue_cond;
102 GSource *watch_id;
103 GMainContext *main_context;
104 };
106 G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
108 /* fixme: do something about this */
109 static void
110 marshal_VOID__MINIOBJECT (GClosure * closure, GValue * return_value,
111 guint n_param_values, const GValue * param_values, gpointer invocation_hint,
112 gpointer marshal_data)
113 {
114 typedef void (*marshalfunc_VOID__MINIOBJECT) (gpointer obj, gpointer arg1,
115 gpointer data2);
116 register marshalfunc_VOID__MINIOBJECT callback;
117 register GCClosure *cc = (GCClosure *) closure;
118 register gpointer data1, data2;
120 g_return_if_fail (n_param_values == 2);
122 if (G_CCLOSURE_SWAP_DATA (closure)) {
123 data1 = closure->data;
124 data2 = g_value_peek_pointer (param_values + 0);
125 } else {
126 data1 = g_value_peek_pointer (param_values + 0);
127 data2 = closure->data;
128 }
129 callback =
130 (marshalfunc_VOID__MINIOBJECT) (marshal_data ? marshal_data :
131 cc->callback);
133 callback (data1, gst_value_get_mini_object (param_values + 1), data2);
134 }
136 static void
137 gst_bus_class_init (GstBusClass * klass)
138 {
139 GObjectClass *gobject_class = (GObjectClass *) klass;
141 parent_class = g_type_class_peek_parent (klass);
143 gobject_class->dispose = gst_bus_dispose;
145 /**
146 * GstBus::sync-message:
147 * @bus: the object which received the signal
148 * @message: the message that has been posted synchronously
149 *
150 * A message has been posted on the bus. This signal is emitted from the
151 * thread that posted the message so one has to be careful with locking.
152 *
153 * This signal will not be emitted by default, you have to set up
154 * gst_bus_sync_signal_handler() as a sync handler if you want this
155 * signal to be emitted when a message is posted on the bus, like this:
156 * <programlisting>
157 * gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
158 * </programlisting>
159 */
160 gst_bus_signals[SYNC_MESSAGE] =
161 g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
162 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
163 G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
164 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
166 /**
167 * GstBus::message:
168 * @bus: the object which received the signal
169 * @message: the message that has been posted asynchronously
170 *
171 * A message has been posted on the bus. This signal is emitted from a
172 * GSource added to the mainloop. this signal will only be emitted when
173 * there is a mainloop running.
174 */
175 gst_bus_signals[ASYNC_MESSAGE] =
176 g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
177 G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
178 G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
179 marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
181 g_type_class_add_private (klass, sizeof (GstBusPrivate));
182 }
184 static void
185 gst_bus_init (GstBus * bus)
186 {
187 bus->queue = g_queue_new ();
188 bus->queue_lock = g_mutex_new ();
190 bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
191 bus->priv->queue_cond = g_cond_new ();
193 GST_DEBUG_OBJECT (bus, "created");
194 }
196 static void
197 gst_bus_dispose (GObject * object)
198 {
199 GstBus *bus = GST_BUS (object);
201 if (bus->queue) {
202 GstMessage *message;
204 g_mutex_lock (bus->queue_lock);
205 do {
206 message = g_queue_pop_head (bus->queue);
207 if (message)
208 gst_message_unref (message);
209 } while (message != NULL);
210 g_queue_free (bus->queue);
211 bus->queue = NULL;
212 g_mutex_unlock (bus->queue_lock);
213 g_mutex_free (bus->queue_lock);
214 bus->queue_lock = NULL;
215 g_cond_free (bus->priv->queue_cond);
216 bus->priv->queue_cond = NULL;
217 }
219 if (bus->priv->main_context) {
220 g_main_context_unref (bus->priv->main_context);
221 bus->priv->main_context = NULL;
222 }
224 G_OBJECT_CLASS (parent_class)->dispose (object);
225 }
227 static void
228 gst_bus_wakeup_main_context (GstBus * bus)
229 {
230 GMainContext *ctx;
232 GST_OBJECT_LOCK (bus);
233 if ((ctx = bus->priv->main_context))
234 g_main_context_ref (ctx);
235 GST_OBJECT_UNLOCK (bus);
237 g_main_context_wakeup (ctx);
239 if (ctx)
240 g_main_context_unref (ctx);
241 }
243 static void
244 gst_bus_set_main_context (GstBus * bus, GMainContext * ctx)
245 {
246 GST_OBJECT_LOCK (bus);
248 if (bus->priv->main_context != NULL) {
249 g_main_context_unref (bus->priv->main_context);
250 bus->priv->main_context = NULL;
251 }
253 if (ctx != NULL) {
254 bus->priv->main_context = g_main_context_ref (ctx);
255 }
257 GST_DEBUG_OBJECT (bus, "setting main context to %p, GLib default context: %p",
258 ctx, g_main_context_default ());
260 GST_OBJECT_UNLOCK (bus);
261 }
263 /**
264 * gst_bus_new:
265 *
266 * Creates a new #GstBus instance.
267 *
268 * Returns: (transfer full): a new #GstBus instance
269 */
270 GstBus *
271 gst_bus_new (void)
272 {
273 GstBus *result;
275 result = g_object_newv (gst_bus_get_type (), 0, NULL);
276 GST_DEBUG_OBJECT (result, "created new bus");
278 return result;
279 }
281 /**
282 * gst_bus_post:
283 * @bus: a #GstBus to post on
284 * @message: (transfer full): the #GstMessage to post
285 *
286 * Post a message on the given bus. Ownership of the message
287 * is taken by the bus.
288 *
289 * Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
290 *
291 * MT safe.
292 */
293 gboolean
294 gst_bus_post (GstBus * bus, GstMessage * message)
295 {
296 GstBusSyncReply reply = GST_BUS_PASS;
297 GstBusSyncHandler handler;
298 gboolean emit_sync_message;
299 gpointer handler_data;
301 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
302 g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
304 GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus, type %s, %" GST_PTR_FORMAT
305 " from source %" GST_PTR_FORMAT,
306 message, GST_MESSAGE_TYPE_NAME (message), message->structure,
307 message->src);
309 GST_OBJECT_LOCK (bus);
310 /* check if the bus is flushing */
311 if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
312 goto is_flushing;
314 handler = bus->sync_handler;
315 handler_data = bus->sync_handler_data;
316 emit_sync_message = bus->priv->num_sync_message_emitters > 0;
317 GST_OBJECT_UNLOCK (bus);
319 /* first call the sync handler if it is installed */
320 if (handler)
321 reply = handler (bus, message, handler_data);
323 /* emit sync-message if requested to do so via
324 gst_bus_enable_sync_message_emission. terrible but effective */
325 if (emit_sync_message && reply != GST_BUS_DROP
326 && handler != gst_bus_sync_signal_handler)
327 gst_bus_sync_signal_handler (bus, message, NULL);
329 /* now see what we should do with the message */
330 switch (reply) {
331 case GST_BUS_DROP:
332 /* drop the message */
333 GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
334 break;
335 case GST_BUS_PASS:
336 /* pass the message to the async queue, refcount passed in the queue */
337 GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
338 g_mutex_lock (bus->queue_lock);
339 g_queue_push_tail (bus->queue, message);
340 g_cond_broadcast (bus->priv->queue_cond);
341 g_mutex_unlock (bus->queue_lock);
342 GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
344 gst_bus_wakeup_main_context (bus);
346 break;
347 case GST_BUS_ASYNC:
348 {
349 /* async delivery, we need a mutex and a cond to block
350 * on */
351 GMutex *lock = g_mutex_new ();
352 GCond *cond = g_cond_new ();
354 GST_MESSAGE_COND (message) = cond;
355 GST_MESSAGE_GET_LOCK (message) = lock;
357 GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
359 /* now we lock the message mutex, send the message to the async
360 * queue. When the message is handled by the app and destroyed,
361 * the cond will be signalled and we can continue */
362 g_mutex_lock (lock);
363 g_mutex_lock (bus->queue_lock);
364 g_queue_push_tail (bus->queue, message);
365 g_cond_broadcast (bus->priv->queue_cond);
366 g_mutex_unlock (bus->queue_lock);
368 gst_bus_wakeup_main_context (bus);
370 /* now block till the message is freed */
371 g_cond_wait (cond, lock);
372 g_mutex_unlock (lock);
374 GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
376 g_mutex_free (lock);
377 g_cond_free (cond);
378 break;
379 }
380 default:
381 g_warning ("invalid return from bus sync handler");
382 break;
383 }
384 return TRUE;
386 /* ERRORS */
387 is_flushing:
388 {
389 GST_DEBUG_OBJECT (bus, "bus is flushing");
390 gst_message_unref (message);
391 GST_OBJECT_UNLOCK (bus);
393 return FALSE;
394 }
395 }
397 /**
398 * gst_bus_have_pending:
399 * @bus: a #GstBus to check
400 *
401 * Check if there are pending messages on the bus that
402 * should be handled.
403 *
404 * Returns: TRUE if there are messages on the bus to be handled, FALSE
405 * otherwise.
406 *
407 * MT safe.
408 */
409 gboolean
410 gst_bus_have_pending (GstBus * bus)
411 {
412 gboolean result;
414 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
416 g_mutex_lock (bus->queue_lock);
417 /* see if there is a message on the bus */
418 result = !g_queue_is_empty (bus->queue);
419 g_mutex_unlock (bus->queue_lock);
421 return result;
422 }
424 /**
425 * gst_bus_set_flushing:
426 * @bus: a #GstBus
427 * @flushing: whether or not to flush the bus
428 *
429 * If @flushing, flush out and unref any messages queued in the bus. Releases
430 * references to the message origin objects. Will flush future messages until
431 * gst_bus_set_flushing() sets @flushing to #FALSE.
432 *
433 * MT safe.
434 */
435 void
436 gst_bus_set_flushing (GstBus * bus, gboolean flushing)
437 {
438 GstMessage *message;
440 GST_OBJECT_LOCK (bus);
442 if (flushing) {
443 GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
445 GST_DEBUG_OBJECT (bus, "set bus flushing");
447 while ((message = gst_bus_pop (bus)))
448 gst_message_unref (message);
449 } else {
450 GST_DEBUG_OBJECT (bus, "unset bus flushing");
451 GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
452 }
454 GST_OBJECT_UNLOCK (bus);
455 }
457 /**
458 * gst_bus_timed_pop_filtered:
459 * @bus: a #GstBus to pop from
460 * @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
461 * @types: message types to take into account, GST_MESSAGE_ANY for any type
462 *
463 * Get a message from the bus whose type matches the message type mask @types,
464 * waiting up to the specified timeout (and discarding any messages that do not
465 * match the mask provided).
466 *
467 * If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
468 * @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
469 * matching message was posted on the bus.
470 *
471 * Returns: (transfer full): a #GstMessage matching the filter in @types,
472 * or NULL if no matching message was found on the bus until the timeout
473 * expired. The message is taken from the bus and needs to be unreffed
474 * with gst_message_unref() after usage.
475 *
476 * MT safe.
477 *
478 * Since: 0.10.15
479 */
480 GstMessage *
481 gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
482 GstMessageType types)
483 {
484 GstMessage *message;
485 GTimeVal *timeval, abstimeout;
486 gboolean first_round = TRUE;
488 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
489 g_return_val_if_fail (types != 0, NULL);
491 g_mutex_lock (bus->queue_lock);
493 while (TRUE) {
494 GST_LOG_OBJECT (bus, "have %d messages", g_queue_get_length (bus->queue));
496 while ((message = g_queue_pop_head (bus->queue))) {
497 GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
498 message, GST_MESSAGE_TYPE_NAME (message),
499 GST_MESSAGE_SRC_NAME (message), (guint) types);
500 if ((GST_MESSAGE_TYPE (message) & types) != 0) {
501 /* exit the loop, we have a message */
502 goto beach;
503 } else {
504 GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
505 gst_message_unref (message);
506 message = NULL;
507 }
508 }
510 /* no need to wait, exit loop */
511 if (timeout == 0)
512 break;
514 if (timeout == GST_CLOCK_TIME_NONE) {
515 /* wait forever */
516 timeval = NULL;
517 } else if (first_round) {
518 glong add = timeout / 1000;
520 if (add == 0)
521 /* no need to wait */
522 break;
524 /* make timeout absolute */
525 g_get_current_time (&abstimeout);
526 g_time_val_add (&abstimeout, add);
527 timeval = &abstimeout;
528 first_round = FALSE;
529 GST_DEBUG_OBJECT (bus, "blocking for message, timeout %ld", add);
530 } else {
531 /* calculated the absolute end time already, no need to do it again */
532 GST_DEBUG_OBJECT (bus, "blocking for message, again");
533 timeval = &abstimeout; /* fool compiler */
534 }
535 if (!g_cond_timed_wait (bus->priv->queue_cond, bus->queue_lock, timeval)) {
536 GST_INFO_OBJECT (bus, "timed out, breaking loop");
537 break;
538 } else {
539 GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
540 }
541 }
543 beach:
545 g_mutex_unlock (bus->queue_lock);
547 return message;
548 }
551 /**
552 * gst_bus_timed_pop:
553 * @bus: a #GstBus to pop
554 * @timeout: a timeout
555 *
556 * Get a message from the bus, waiting up to the specified timeout.
557 *
558 * If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
559 * #GST_CLOCK_TIME_NONE, this function will block forever until a message was
560 * posted on the bus.
561 *
562 * Returns: (transfer full): the #GstMessage that is on the bus after the
563 * specified timeout or NULL if the bus is empty after the timeout expired.
564 * The message is taken from the bus and needs to be unreffed with
565 * gst_message_unref() after usage.
566 *
567 * MT safe.
568 *
569 * Since: 0.10.12
570 */
571 GstMessage *
572 gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
573 {
574 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
576 return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
577 }
579 /**
580 * gst_bus_pop_filtered:
581 * @bus: a #GstBus to pop
582 * @types: message types to take into account
583 *
584 * Get a message matching @type from the bus. Will discard all messages on
585 * the bus that do not match @type and that have been posted before the first
586 * message that does match @type. If there is no message matching @type on
587 * the bus, all messages will be discarded.
588 *
589 * Returns: (transfer full): the next #GstMessage matching @type that is on
590 * the bus, or NULL if the bus is empty or there is no message matching
591 * @type. The message is taken from the bus and needs to be unreffed with
592 * gst_message_unref() after usage.
593 *
594 * MT safe.
595 *
596 * Since: 0.10.15
597 */
598 GstMessage *
599 gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
600 {
601 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
602 g_return_val_if_fail (types != 0, NULL);
604 return gst_bus_timed_pop_filtered (bus, 0, types);
605 }
607 /**
608 * gst_bus_pop:
609 * @bus: a #GstBus to pop
610 *
611 * Get a message from the bus.
612 *
613 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
614 * bus is empty. The message is taken from the bus and needs to be unreffed
615 * with gst_message_unref() after usage.
616 *
617 * MT safe.
618 */
619 GstMessage *
620 gst_bus_pop (GstBus * bus)
621 {
622 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
624 return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
625 }
627 /**
628 * gst_bus_peek:
629 * @bus: a #GstBus
630 *
631 * Peek the message on the top of the bus' queue. The message will remain
632 * on the bus' message queue. A reference is returned, and needs to be unreffed
633 * by the caller.
634 *
635 * Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
636 * bus is empty.
637 *
638 * MT safe.
639 */
640 GstMessage *
641 gst_bus_peek (GstBus * bus)
642 {
643 GstMessage *message;
645 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
647 g_mutex_lock (bus->queue_lock);
648 message = g_queue_peek_head (bus->queue);
649 if (message)
650 gst_message_ref (message);
651 g_mutex_unlock (bus->queue_lock);
653 GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
655 return message;
656 }
658 /**
659 * gst_bus_set_sync_handler:
660 * @bus: a #GstBus to install the handler on
661 * @func: The handler function to install
662 * @data: User data that will be sent to the handler function.
663 *
664 * Sets the synchronous handler on the bus. The function will be called
665 * every time a new message is posted on the bus. Note that the function
666 * will be called in the same thread context as the posting object. This
667 * function is usually only called by the creator of the bus. Applications
668 * should handle messages asynchronously using the gst_bus watch and poll
669 * functions.
670 *
671 * You cannot replace an existing sync_handler. You can pass NULL to this
672 * function, which will clear the existing handler.
673 */
674 void
675 gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
676 {
677 g_return_if_fail (GST_IS_BUS (bus));
679 GST_OBJECT_LOCK (bus);
681 /* Assert if the user attempts to replace an existing sync_handler,
682 * other than to clear it */
683 if (func != NULL && bus->sync_handler != NULL)
684 goto no_replace;
686 bus->sync_handler = func;
687 bus->sync_handler_data = data;
688 GST_OBJECT_UNLOCK (bus);
690 return;
692 no_replace:
693 {
694 GST_OBJECT_UNLOCK (bus);
695 g_warning ("cannot replace existing sync handler");
696 return;
697 }
698 }
700 /* GSource for the bus
701 */
702 typedef struct
703 {
704 GSource source;
705 GstBus *bus;
706 gboolean inited;
707 } GstBusSource;
709 static gboolean
710 gst_bus_source_prepare (GSource * source, gint * timeout)
711 {
712 GstBusSource *bsrc = (GstBusSource *) source;
714 /* we do this here now that we know that we're attached to a main context
715 * (we don't support detaching a source from a main context and then
716 * re-attaching it to a different main context) */
717 if (G_UNLIKELY (!bsrc->inited)) {
718 gst_bus_set_main_context (bsrc->bus, g_source_get_context (source));
719 bsrc->inited = TRUE;
720 }
722 *timeout = -1;
723 return gst_bus_have_pending (bsrc->bus);
724 }
726 static gboolean
727 gst_bus_source_check (GSource * source)
728 {
729 GstBusSource *bsrc = (GstBusSource *) source;
731 return gst_bus_have_pending (bsrc->bus);
732 }
734 static gboolean
735 gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
736 gpointer user_data)
737 {
738 GstBusFunc handler = (GstBusFunc) callback;
739 GstBusSource *bsource = (GstBusSource *) source;
740 GstMessage *message;
741 gboolean keep;
742 GstBus *bus;
744 g_return_val_if_fail (bsource != NULL, FALSE);
746 bus = bsource->bus;
748 g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
750 message = gst_bus_pop (bus);
752 /* The message queue might be empty if some other thread or callback set
753 * the bus to flushing between check/prepare and dispatch */
754 if (G_UNLIKELY (message == NULL))
755 return TRUE;
757 if (!handler)
758 goto no_handler;
760 GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %" GST_PTR_FORMAT,
761 source, message);
763 keep = handler (bus, message, user_data);
764 gst_message_unref (message);
766 GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
768 return keep;
770 no_handler:
771 {
772 g_warning ("GstBus watch dispatched without callback\n"
773 "You must call g_source_set_callback().");
774 gst_message_unref (message);
775 return FALSE;
776 }
777 }
779 static void
780 gst_bus_source_finalize (GSource * source)
781 {
782 GstBusSource *bsource = (GstBusSource *) source;
783 GstBus *bus;
785 bus = bsource->bus;
787 GST_DEBUG_OBJECT (bus, "finalize source %p", source);
789 GST_OBJECT_LOCK (bus);
790 if (bus->priv->watch_id == source)
791 bus->priv->watch_id = NULL;
792 GST_OBJECT_UNLOCK (bus);
794 gst_bus_set_main_context (bsource->bus, NULL);
795 gst_object_unref (bsource->bus);
796 bsource->bus = NULL;
797 }
799 static GSourceFuncs gst_bus_source_funcs = {
800 gst_bus_source_prepare,
801 gst_bus_source_check,
802 gst_bus_source_dispatch,
803 gst_bus_source_finalize
804 };
806 /**
807 * gst_bus_create_watch:
808 * @bus: a #GstBus to create the watch for
809 *
810 * Create watch for this bus. The GSource will be dispatched whenever
811 * a message is on the bus. After the GSource is dispatched, the
812 * message is popped off the bus and unreffed.
813 *
814 * Returns: (transfer full): a #GSource that can be added to a mainloop.
815 */
816 GSource *
817 gst_bus_create_watch (GstBus * bus)
818 {
819 GstBusSource *source;
821 g_return_val_if_fail (GST_IS_BUS (bus), NULL);
823 source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
824 sizeof (GstBusSource));
826 #if GLIB_CHECK_VERSION(2,26,0)
827 g_source_set_name ((GSource *) source, "GStreamer message bus watch");
828 #endif
830 source->bus = gst_object_ref (bus);
831 source->inited = FALSE;
833 return (GSource *) source;
834 }
836 /* must be called with the bus OBJECT LOCK */
837 static guint
838 gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
839 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
840 {
841 GMainContext *ctx;
842 guint id;
843 GSource *source;
845 if (bus->priv->watch_id) {
846 GST_ERROR_OBJECT (bus,
847 "Tried to add new watch while one was already there");
848 return 0;
849 }
851 source = gst_bus_create_watch (bus);
853 if (priority != G_PRIORITY_DEFAULT)
854 g_source_set_priority (source, priority);
856 g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
858 ctx = g_main_context_get_thread_default ();
859 id = g_source_attach (source, ctx);
860 g_source_unref (source);
862 if (id) {
863 bus->priv->watch_id = source;
864 }
866 GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
867 return id;
868 }
870 /**
871 * gst_bus_add_watch_full:
872 * @bus: a #GstBus to create the watch for.
873 * @priority: The priority of the watch.
874 * @func: A function to call when a message is received.
875 * @user_data: user data passed to @func.
876 * @notify: the function to call when the source is removed.
877 *
878 * Adds a bus watch to the default main context with the given @priority (e.g.
879 * %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
880 * main context set up using g_main_context_push_thread_default() (before
881 * one had to create a bus watch source and attach it to the desired main
882 * context 'manually').
883 *
884 * This function is used to receive asynchronous messages in the main loop.
885 * There can only be a single bus watch per bus, you must remove it before you
886 * can set a new one.
887 *
888 * When @func is called, the message belongs to the caller; if you want to
889 * keep a copy of it, call gst_message_ref() before leaving @func.
890 *
891 * The watch can be removed using g_source_remove() or by returning FALSE
892 * from @func.
893 *
894 * Returns: The event source id.
895 *
896 * MT safe.
897 */
898 guint
899 gst_bus_add_watch_full (GstBus * bus, gint priority,
900 GstBusFunc func, gpointer user_data, GDestroyNotify notify)
901 {
902 guint id;
904 g_return_val_if_fail (GST_IS_BUS (bus), 0);
906 GST_OBJECT_LOCK (bus);
907 id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
908 GST_OBJECT_UNLOCK (bus);
910 return id;
911 }
913 /**
914 * gst_bus_add_watch:
915 * @bus: a #GstBus to create the watch for
916 * @func: A function to call when a message is received.
917 * @user_data: user data passed to @func.
918 *
919 * Adds a bus watch to the default main context with the default priority
920 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
921 * main context set up using g_main_context_push_thread_default() (before
922 * one had to create a bus watch source and attach it to the desired main
923 * context 'manually').
924 *
925 * This function is used to receive asynchronous messages in the main loop.
926 * There can only be a single bus watch per bus, you must remove it before you
927 * can set a new one.
928 *
929 * The watch can be removed using g_source_remove() or by returning FALSE
930 * from @func.
931 *
932 * Returns: The event source id.
933 *
934 * MT safe.
935 */
936 guint
937 gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
938 {
939 return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
940 user_data, NULL);
941 }
943 typedef struct
944 {
945 GMainLoop *loop;
946 guint timeout_id;
947 gboolean source_running;
948 GstMessageType events;
949 GstMessage *message;
950 } GstBusPollData;
952 static void
953 poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
954 {
955 GstMessageType type;
957 if (!g_main_loop_is_running (poll_data->loop)) {
958 GST_DEBUG ("mainloop %p not running", poll_data->loop);
959 return;
960 }
962 type = GST_MESSAGE_TYPE (message);
964 if (type & poll_data->events) {
965 g_assert (poll_data->message == NULL);
966 /* keep ref to message */
967 poll_data->message = gst_message_ref (message);
968 GST_DEBUG ("mainloop %p quit", poll_data->loop);
969 g_main_loop_quit (poll_data->loop);
970 } else {
971 GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
972 }
973 }
975 static gboolean
976 poll_timeout (GstBusPollData * poll_data)
977 {
978 GST_DEBUG ("mainloop %p quit", poll_data->loop);
979 g_main_loop_quit (poll_data->loop);
981 /* we don't remove the GSource as this would free our poll_data,
982 * which we still need */
983 return TRUE;
984 }
986 static void
987 poll_destroy (GstBusPollData * poll_data, gpointer unused)
988 {
989 poll_data->source_running = FALSE;
990 if (!poll_data->timeout_id) {
991 g_main_loop_unref (poll_data->loop);
992 g_slice_free (GstBusPollData, poll_data);
993 }
994 }
996 static void
997 poll_destroy_timeout (GstBusPollData * poll_data)
998 {
999 poll_data->timeout_id = 0;
1000 if (!poll_data->source_running) {
1001 g_main_loop_unref (poll_data->loop);
1002 g_slice_free (GstBusPollData, poll_data);
1003 }
1004 }
1006 /**
1007 * gst_bus_poll:
1008 * @bus: a #GstBus
1009 * @events: a mask of #GstMessageType, representing the set of message types to
1010 * poll for.
1011 * @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
1012 * indefinitely.
1013 *
1014 * Poll the bus for messages. Will block while waiting for messages to come.
1015 * You can specify a maximum time to poll with the @timeout parameter. If
1016 * @timeout is negative, this function will block indefinitely.
1017 *
1018 * All messages not in @events will be popped off the bus and will be ignored.
1019 *
1020 * Because poll is implemented using the "message" signal enabled by
1021 * gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
1022 * signal to be emitted for every message that poll sees. Thus a "message"
1023 * signal handler will see the same messages that this function sees -- neither
1024 * will steal messages from the other.
1025 *
1026 * This function will run a main loop from the default main context when
1027 * polling.
1028 *
1029 * You should never use this function, since it is pure evil. This is
1030 * especially true for GUI applications based on Gtk+ or Qt, but also for any
1031 * other non-trivial application that uses the GLib main loop. As this function
1032 * runs a GLib main loop, any callback attached to the default GLib main
1033 * context may be invoked. This could be timeouts, GUI events, I/O events etc.;
1034 * even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
1035 * may do things you do not expect, e.g. destroy the main application window or
1036 * some other resource; change other application state; display a dialog and
1037 * run another main loop until the user clicks it away. In short, using this
1038 * function may add a lot of complexity to your code through unexpected
1039 * re-entrancy and unexpected changes to your application's state.
1040 *
1041 * For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
1042 * other short timeouts use gst_bus_timed_pop_filtered(); everything else is
1043 * better handled by setting up an asynchronous bus watch and doing things
1044 * from there.
1045 *
1046 * Returns: (transfer full): the message that was received, or NULL if the
1047 * poll timed out. The message is taken from the bus and needs to be
1048 * unreffed with gst_message_unref() after usage.
1049 */
1050 GstMessage *
1051 gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
1052 {
1053 GstBusPollData *poll_data;
1054 GstMessage *ret;
1055 gulong id;
1057 poll_data = g_slice_new (GstBusPollData);
1058 poll_data->source_running = TRUE;
1059 poll_data->loop = g_main_loop_new (NULL, FALSE);
1060 poll_data->events = events;
1061 poll_data->message = NULL;
1063 if (timeout >= 0)
1064 poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
1065 timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
1066 (GDestroyNotify) poll_destroy_timeout);
1067 else
1068 poll_data->timeout_id = 0;
1070 id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
1071 (GClosureNotify) poll_destroy, 0);
1073 /* these can be nested, so it's ok */
1074 gst_bus_add_signal_watch (bus);
1076 GST_DEBUG ("running mainloop %p", poll_data->loop);
1077 g_main_loop_run (poll_data->loop);
1078 GST_DEBUG ("mainloop stopped %p", poll_data->loop);
1080 gst_bus_remove_signal_watch (bus);
1082 /* holds a ref */
1083 ret = poll_data->message;
1085 if (poll_data->timeout_id)
1086 g_source_remove (poll_data->timeout_id);
1088 /* poll_data will be freed now */
1089 g_signal_handler_disconnect (bus, id);
1091 GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
1093 return ret;
1094 }
1096 /**
1097 * gst_bus_async_signal_func:
1098 * @bus: a #GstBus
1099 * @message: the #GstMessage received
1100 * @data: user data
1101 *
1102 * A helper #GstBusFunc that can be used to convert all asynchronous messages
1103 * into signals.
1104 *
1105 * Returns: TRUE
1106 */
1107 gboolean
1108 gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
1109 {
1110 GQuark detail = 0;
1112 g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
1113 g_return_val_if_fail (message != NULL, TRUE);
1115 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1117 g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
1119 /* we never remove this source based on signal emission return values */
1120 return TRUE;
1121 }
1123 /**
1124 * gst_bus_sync_signal_handler:
1125 * @bus: a #GstBus
1126 * @message: the #GstMessage received
1127 * @data: user data
1128 *
1129 * A helper GstBusSyncHandler that can be used to convert all synchronous
1130 * messages into signals.
1131 *
1132 * Returns: GST_BUS_PASS
1133 */
1134 GstBusSyncReply
1135 gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
1136 {
1137 GQuark detail = 0;
1139 g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
1140 g_return_val_if_fail (message != NULL, GST_BUS_DROP);
1142 detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
1144 g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
1146 return GST_BUS_PASS;
1147 }
1149 /**
1150 * gst_bus_enable_sync_message_emission:
1151 * @bus: a #GstBus on which you want to receive the "sync-message" signal
1152 *
1153 * Instructs GStreamer to emit the "sync-message" signal after running the bus's
1154 * sync handler. This function is here so that code can ensure that they can
1155 * synchronously receive messages without having to affect what the bin's sync
1156 * handler is.
1157 *
1158 * This function may be called multiple times. To clean up, the caller is
1159 * responsible for calling gst_bus_disable_sync_message_emission() as many times
1160 * as this function is called.
1161 *
1162 * While this function looks similar to gst_bus_add_signal_watch(), it is not
1163 * exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
1164 * signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
1165 * to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
1166 * comes from the thread of whatever object posted the message; the "message"
1167 * signal is marshalled to the main thread via the main loop.
1168 *
1169 * MT safe.
1170 */
1171 void
1172 gst_bus_enable_sync_message_emission (GstBus * bus)
1173 {
1174 g_return_if_fail (GST_IS_BUS (bus));
1176 GST_OBJECT_LOCK (bus);
1177 bus->priv->num_sync_message_emitters++;
1178 GST_OBJECT_UNLOCK (bus);
1179 }
1181 /**
1182 * gst_bus_disable_sync_message_emission:
1183 * @bus: a #GstBus on which you previously called
1184 * gst_bus_enable_sync_message_emission()
1185 *
1186 * Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
1187 * See gst_bus_enable_sync_message_emission() for more information.
1188 *
1189 * In the event that multiple pieces of code have called
1190 * gst_bus_enable_sync_message_emission(), the sync-message emissions will only
1191 * be stopped after all calls to gst_bus_enable_sync_message_emission() were
1192 * "cancelled" by calling this function. In this way the semantics are exactly
1193 * the same as gst_object_ref() that which calls enable should also call
1194 * disable.
1195 *
1196 * MT safe.
1197 */
1198 void
1199 gst_bus_disable_sync_message_emission (GstBus * bus)
1200 {
1201 g_return_if_fail (GST_IS_BUS (bus));
1202 g_return_if_fail (bus->num_signal_watchers == 0);
1204 GST_OBJECT_LOCK (bus);
1205 bus->priv->num_sync_message_emitters--;
1206 GST_OBJECT_UNLOCK (bus);
1207 }
1209 /**
1210 * gst_bus_add_signal_watch_full:
1211 * @bus: a #GstBus on which you want to receive the "message" signal
1212 * @priority: The priority of the watch.
1213 *
1214 * Adds a bus signal watch to the default main context with the given @priority
1215 * (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
1216 * non-default main context set up using g_main_context_push_thread_default()
1217 * (before one had to create a bus watch source and attach it to the desired
1218 * main context 'manually').
1219 *
1220 * After calling this statement, the bus will emit the "message" signal for each
1221 * message posted on the bus when the main loop is running.
1222 *
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.
1226 *
1227 * There can only be a single bus watch per bus, you must remove any signal
1228 * watch before you can set another type of watch.
1229 *
1230 * MT safe.
1231 */
1232 void
1233 gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
1234 {
1235 g_return_if_fail (GST_IS_BUS (bus));
1237 /* I know the callees don't take this lock, so go ahead and abuse it */
1238 GST_OBJECT_LOCK (bus);
1240 if (bus->num_signal_watchers > 0)
1241 goto done;
1243 /* this should not fail because the counter above takes care of it */
1244 g_assert (bus->signal_watch_id == 0);
1246 bus->signal_watch_id =
1247 gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
1248 NULL, NULL);
1250 if (G_UNLIKELY (bus->signal_watch_id == 0))
1251 goto add_failed;
1253 done:
1255 bus->num_signal_watchers++;
1257 GST_OBJECT_UNLOCK (bus);
1258 return;
1260 /* ERRORS */
1261 add_failed:
1262 {
1263 g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
1264 GST_OBJECT_UNLOCK (bus);
1265 return;
1266 }
1267 }
1269 /**
1270 * gst_bus_add_signal_watch:
1271 * @bus: a #GstBus on which you want to receive the "message" signal
1272 *
1273 * Adds a bus signal watch to the default main context with the default priority
1274 * (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
1275 * main context set up using g_main_context_push_thread_default() (before
1276 * one had to create a bus watch source and attach it to the desired main
1277 * context 'manually').
1278 *
1279 * After calling this statement, the bus will emit the "message" signal for each
1280 * message posted on the bus.
1281 *
1282 * This function may be called multiple times. To clean up, the caller is
1283 * responsible for calling gst_bus_remove_signal_watch() as many times as this
1284 * function is called.
1285 *
1286 * MT safe.
1287 */
1288 void
1289 gst_bus_add_signal_watch (GstBus * bus)
1290 {
1291 gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
1292 }
1294 /**
1295 * gst_bus_remove_signal_watch:
1296 * @bus: a #GstBus you previously added a signal watch to
1297 *
1298 * Removes a signal watch previously added with gst_bus_add_signal_watch().
1299 *
1300 * MT safe.
1301 */
1302 void
1303 gst_bus_remove_signal_watch (GstBus * bus)
1304 {
1305 guint id = 0;
1307 g_return_if_fail (GST_IS_BUS (bus));
1309 /* I know the callees don't take this lock, so go ahead and abuse it */
1310 GST_OBJECT_LOCK (bus);
1312 if (bus->num_signal_watchers == 0)
1313 goto error;
1315 bus->num_signal_watchers--;
1317 if (bus->num_signal_watchers > 0)
1318 goto done;
1320 id = bus->signal_watch_id;
1321 bus->signal_watch_id = 0;
1323 GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
1325 done:
1326 GST_OBJECT_UNLOCK (bus);
1328 if (id)
1329 g_source_remove (id);
1331 return;
1333 /* ERRORS */
1334 error:
1335 {
1336 g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
1337 GST_OBJECT_UNLOCK (bus);
1338 return;
1339 }
1340 }