gstreamer/gst/gstbus.c
Wim Taymans 14d7db1b52 bus: make the bus almost lockfree
Use new GstPoll functionality to wakeup the mainloop.
Use an atomic queue on the writer side to post the messages.
The reader side it protected with the lock still because we don't want multiple
concurrent readers.
2011-02-16 17:56:39 +01:00

1281 lines
36 KiB
C

/* GStreamer
* Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
*
* gstbus.c: GstBus subsystem
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* SECTION:gstbus
* @short_description: Asynchronous message bus subsystem
* @see_also: #GstMessage, #GstElement
*
* The #GstBus is an object responsible for delivering #GstMessage packets in
* a first-in first-out way from the streaming threads (see #GstTask) to the
* application.
*
* Since the application typically only wants to deal with delivery of these
* messages from one thread, the GstBus will marshall the messages between
* different threads. This is important since the actual streaming of media
* is done in another thread than the application.
*
* The GstBus provides support for #GSource based notifications. This makes it
* possible to handle the delivery in the glib mainloop.
*
* The #GSource callback function gst_bus_async_signal_func() can be used to
* convert all bus messages into signal emissions.
*
* A message is posted on the bus with the gst_bus_post() method. With the
* gst_bus_peek() and gst_bus_pop() methods one can look at or retrieve a
* previously posted message.
*
* The bus can be polled with the gst_bus_poll() method. This methods blocks
* up to the specified timeout value until one of the specified messages types
* is posted on the bus. The application can then gst_bus_pop() the messages
* from the bus to handle them.
* Alternatively the application can register an asynchronous bus function
* using gst_bus_add_watch_full() or gst_bus_add_watch(). This function will
* install a #GSource in the default glib main loop and will deliver messages
* a short while after they have been posted. Note that the main loop should
* be running for the asynchronous callbacks.
*
* It is also possible to get messages from the bus without any thread
* marshalling with the gst_bus_set_sync_handler() method. This makes it
* possible to react to a message in the same thread that posted the
* message on the bus. This should only be used if the application is able
* to deal with messages from different threads.
*
* Every #GstPipeline has one bus.
*
* Note that a #GstPipeline will set its bus into flushing state when changing
* from READY to NULL state.
*
* Last reviewed on 2006-03-12 (0.10.5)
*/
#include "gst_private.h"
#include <errno.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <sys/types.h>
#include "gstinfo.h"
#include "gstpoll.h"
#include "gstbus.h"
#define GST_CAT_DEFAULT GST_CAT_BUS
/* bus signals */
enum
{
SYNC_MESSAGE,
ASYNC_MESSAGE,
/* add more above */
LAST_SIGNAL
};
static void gst_bus_dispose (GObject * object);
static GstObjectClass *parent_class = NULL;
static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
struct _GstBusPrivate
{
guint num_sync_message_emitters;
GCond *queue_cond;
GSource *watch_id;
GstPoll *poll;
GPollFD pollfd;
};
G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
/* fixme: do something about this */
static void
marshal_VOID__MINIOBJECT (GClosure * closure, GValue * return_value,
guint n_param_values, const GValue * param_values, gpointer invocation_hint,
gpointer marshal_data)
{
typedef void (*marshalfunc_VOID__MINIOBJECT) (gpointer obj, gpointer arg1,
gpointer data2);
register marshalfunc_VOID__MINIOBJECT callback;
register GCClosure *cc = (GCClosure *) closure;
register gpointer data1, data2;
g_return_if_fail (n_param_values == 2);
if (G_CCLOSURE_SWAP_DATA (closure)) {
data1 = closure->data;
data2 = g_value_peek_pointer (param_values + 0);
} else {
data1 = g_value_peek_pointer (param_values + 0);
data2 = closure->data;
}
callback =
(marshalfunc_VOID__MINIOBJECT) (marshal_data ? marshal_data :
cc->callback);
callback (data1, gst_value_get_mini_object (param_values + 1), data2);
}
static void
gst_bus_class_init (GstBusClass * klass)
{
GObjectClass *gobject_class = (GObjectClass *) klass;
parent_class = g_type_class_peek_parent (klass);
gobject_class->dispose = gst_bus_dispose;
/**
* GstBus::sync-message:
* @bus: the object which received the signal
* @message: the message that has been posted synchronously
*
* A message has been posted on the bus. This signal is emitted from the
* thread that posted the message so one has to be careful with locking.
*
* This signal will not be emitted by default, you have to set up
* gst_bus_sync_signal_handler() as a sync handler if you want this
* signal to be emitted when a message is posted on the bus, like this:
* <programlisting>
* gst_bus_set_sync_handler (bus, gst_bus_sync_signal_handler, yourdata);
* </programlisting>
*/
gst_bus_signals[SYNC_MESSAGE] =
g_signal_new ("sync-message", G_TYPE_FROM_CLASS (klass),
G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
G_STRUCT_OFFSET (GstBusClass, sync_message), NULL, NULL,
marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
/**
* GstBus::message:
* @bus: the object which received the signal
* @message: the message that has been posted asynchronously
*
* A message has been posted on the bus. This signal is emitted from a
* GSource added to the mainloop. this signal will only be emitted when
* there is a mainloop running.
*/
gst_bus_signals[ASYNC_MESSAGE] =
g_signal_new ("message", G_TYPE_FROM_CLASS (klass),
G_SIGNAL_RUN_LAST | G_SIGNAL_DETAILED,
G_STRUCT_OFFSET (GstBusClass, message), NULL, NULL,
marshal_VOID__MINIOBJECT, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
g_type_class_add_private (klass, sizeof (GstBusPrivate));
}
static void
gst_bus_init (GstBus * bus)
{
bus->queue = gst_atomic_queue_new (32);
bus->queue_lock = g_mutex_new ();
bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
bus->priv->queue_cond = g_cond_new ();
bus->priv->poll = gst_poll_new_timer ();
gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
GST_DEBUG_OBJECT (bus, "created");
}
static void
gst_bus_dispose (GObject * object)
{
GstBus *bus = GST_BUS (object);
if (bus->queue) {
GstMessage *message;
g_mutex_lock (bus->queue_lock);
do {
message = gst_atomic_queue_pop (bus->queue);
if (message)
gst_message_unref (message);
} while (message != NULL);
gst_atomic_queue_unref (bus->queue);
bus->queue = NULL;
g_mutex_unlock (bus->queue_lock);
g_mutex_free (bus->queue_lock);
bus->queue_lock = NULL;
g_cond_free (bus->priv->queue_cond);
bus->priv->queue_cond = NULL;
gst_poll_free (bus->priv->poll);
}
G_OBJECT_CLASS (parent_class)->dispose (object);
}
/**
* gst_bus_new:
*
* Creates a new #GstBus instance.
*
* Returns: (transfer full): a new #GstBus instance
*/
GstBus *
gst_bus_new (void)
{
GstBus *result;
result = g_object_newv (gst_bus_get_type (), 0, NULL);
GST_DEBUG_OBJECT (result, "created new bus");
return result;
}
/**
* gst_bus_post:
* @bus: a #GstBus to post on
* @message: (transfer full): the #GstMessage to post
*
* Post a message on the given bus. Ownership of the message
* is taken by the bus.
*
* Returns: TRUE if the message could be posted, FALSE if the bus is flushing.
*
* MT safe.
*/
gboolean
gst_bus_post (GstBus * bus, GstMessage * message)
{
GstBusSyncReply reply = GST_BUS_PASS;
GstBusSyncHandler handler;
gboolean emit_sync_message;
gpointer handler_data;
g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
g_return_val_if_fail (GST_IS_MESSAGE (message), FALSE);
GST_DEBUG_OBJECT (bus, "[msg %p] posting on bus, type %s, %" GST_PTR_FORMAT
" from source %" GST_PTR_FORMAT,
message, GST_MESSAGE_TYPE_NAME (message), message->structure,
message->src);
GST_OBJECT_LOCK (bus);
/* check if the bus is flushing */
if (GST_OBJECT_FLAG_IS_SET (bus, GST_BUS_FLUSHING))
goto is_flushing;
handler = bus->sync_handler;
handler_data = bus->sync_handler_data;
emit_sync_message = bus->priv->num_sync_message_emitters > 0;
GST_OBJECT_UNLOCK (bus);
/* first call the sync handler if it is installed */
if (handler)
reply = handler (bus, message, handler_data);
/* emit sync-message if requested to do so via
gst_bus_enable_sync_message_emission. terrible but effective */
if (emit_sync_message && reply != GST_BUS_DROP
&& handler != gst_bus_sync_signal_handler)
gst_bus_sync_signal_handler (bus, message, NULL);
/* now see what we should do with the message */
switch (reply) {
case GST_BUS_DROP:
/* drop the message */
GST_DEBUG_OBJECT (bus, "[msg %p] dropped", message);
break;
case GST_BUS_PASS:
/* pass the message to the async queue, refcount passed in the queue */
GST_DEBUG_OBJECT (bus, "[msg %p] pushing on async queue", message);
gst_atomic_queue_push (bus->queue, message);
gst_poll_write_control (bus->priv->poll);
GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
break;
case GST_BUS_ASYNC:
{
/* async delivery, we need a mutex and a cond to block
* on */
GMutex *lock = g_mutex_new ();
GCond *cond = g_cond_new ();
GST_MESSAGE_COND (message) = cond;
GST_MESSAGE_GET_LOCK (message) = lock;
GST_DEBUG_OBJECT (bus, "[msg %p] waiting for async delivery", message);
/* now we lock the message mutex, send the message to the async
* queue. When the message is handled by the app and destroyed,
* the cond will be signalled and we can continue */
g_mutex_lock (lock);
gst_atomic_queue_push (bus->queue, message);
gst_poll_write_control (bus->priv->poll);
/* now block till the message is freed */
g_cond_wait (cond, lock);
g_mutex_unlock (lock);
GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
g_mutex_free (lock);
g_cond_free (cond);
break;
}
default:
g_warning ("invalid return from bus sync handler");
break;
}
return TRUE;
/* ERRORS */
is_flushing:
{
GST_DEBUG_OBJECT (bus, "bus is flushing");
gst_message_unref (message);
GST_OBJECT_UNLOCK (bus);
return FALSE;
}
}
/**
* gst_bus_have_pending:
* @bus: a #GstBus to check
*
* Check if there are pending messages on the bus that
* should be handled.
*
* Returns: TRUE if there are messages on the bus to be handled, FALSE
* otherwise.
*
* MT safe.
*/
gboolean
gst_bus_have_pending (GstBus * bus)
{
gboolean result;
g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
/* see if there is a message on the bus */
result = gst_atomic_queue_length (bus->queue) != 0;
return result;
}
/**
* gst_bus_set_flushing:
* @bus: a #GstBus
* @flushing: whether or not to flush the bus
*
* If @flushing, flush out and unref any messages queued in the bus. Releases
* references to the message origin objects. Will flush future messages until
* gst_bus_set_flushing() sets @flushing to #FALSE.
*
* MT safe.
*/
void
gst_bus_set_flushing (GstBus * bus, gboolean flushing)
{
GstMessage *message;
GST_OBJECT_LOCK (bus);
if (flushing) {
GST_OBJECT_FLAG_SET (bus, GST_BUS_FLUSHING);
GST_DEBUG_OBJECT (bus, "set bus flushing");
while ((message = gst_bus_pop (bus)))
gst_message_unref (message);
} else {
GST_DEBUG_OBJECT (bus, "unset bus flushing");
GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
}
GST_OBJECT_UNLOCK (bus);
}
/**
* gst_bus_timed_pop_filtered:
* @bus: a #GstBus to pop from
* @timeout: a timeout in nanoseconds, or GST_CLOCK_TIME_NONE to wait forever
* @types: message types to take into account, GST_MESSAGE_ANY for any type
*
* Get a message from the bus whose type matches the message type mask @types,
* waiting up to the specified timeout (and discarding any messages that do not
* match the mask provided).
*
* If @timeout is 0, this function behaves like gst_bus_pop_filtered(). If
* @timeout is #GST_CLOCK_TIME_NONE, this function will block forever until a
* matching message was posted on the bus.
*
* Returns: (transfer full): a #GstMessage matching the filter in @types,
* or NULL if no matching message was found on the bus until the timeout
* expired. The message is taken from the bus and needs to be unreffed
* with gst_message_unref() after usage.
*
* MT safe.
*
* Since: 0.10.15
*/
GstMessage *
gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
GstMessageType types)
{
GstMessage *message;
GTimeVal now, then;
gboolean first_round = TRUE;
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
g_return_val_if_fail (types != 0, NULL);
g_mutex_lock (bus->queue_lock);
while (TRUE) {
gint ret;
GST_LOG_OBJECT (bus, "have %d messages",
gst_atomic_queue_length (bus->queue));
while ((message = gst_atomic_queue_pop (bus->queue))) {
gst_poll_read_control (bus->priv->poll);
GST_DEBUG_OBJECT (bus, "got message %p, %s, type mask is %u",
message, GST_MESSAGE_TYPE_NAME (message), (guint) types);
if ((GST_MESSAGE_TYPE (message) & types) != 0) {
/* exit the loop, we have a message */
goto beach;
} else {
GST_DEBUG_OBJECT (bus, "discarding message, does not match mask");
gst_message_unref (message);
message = NULL;
}
}
/* no need to wait, exit loop */
if (timeout == 0)
break;
else if (timeout != GST_CLOCK_TIME_NONE) {
if (first_round) {
g_get_current_time (&then);
first_round = FALSE;
} else {
GstClockTime elapsed;
g_get_current_time (&now);
elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
if (timeout > elapsed)
timeout -= elapsed;
else
timeout = 0;
}
}
g_mutex_unlock (bus->queue_lock);
ret = gst_poll_wait (bus->priv->poll, timeout);
g_mutex_lock (bus->queue_lock);
if (ret == 0) {
GST_INFO_OBJECT (bus, "timed out, breaking loop");
break;
} else {
GST_INFO_OBJECT (bus, "we got woken up, recheck for message");
}
}
beach:
g_mutex_unlock (bus->queue_lock);
return message;
}
/**
* gst_bus_timed_pop:
* @bus: a #GstBus to pop
* @timeout: a timeout
*
* Get a message from the bus, waiting up to the specified timeout.
*
* If @timeout is 0, this function behaves like gst_bus_pop(). If @timeout is
* #GST_CLOCK_TIME_NONE, this function will block forever until a message was
* posted on the bus.
*
* Returns: (transfer full): the #GstMessage that is on the bus after the
* specified timeout or NULL if the bus is empty after the timeout expired.
* The message is taken from the bus and needs to be unreffed with
* gst_message_unref() after usage.
*
* MT safe.
*
* Since: 0.10.12
*/
GstMessage *
gst_bus_timed_pop (GstBus * bus, GstClockTime timeout)
{
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
return gst_bus_timed_pop_filtered (bus, timeout, GST_MESSAGE_ANY);
}
/**
* gst_bus_pop_filtered:
* @bus: a #GstBus to pop
* @types: message types to take into account
*
* Get a message matching @type from the bus. Will discard all messages on
* the bus that do not match @type and that have been posted before the first
* message that does match @type. If there is no message matching @type on
* the bus, all messages will be discarded.
*
* Returns: (transfer full): the next #GstMessage matching @type that is on
* the bus, or NULL if the bus is empty or there is no message matching
* @type. The message is taken from the bus and needs to be unreffed with
* gst_message_unref() after usage.
*
* MT safe.
*
* Since: 0.10.15
*/
GstMessage *
gst_bus_pop_filtered (GstBus * bus, GstMessageType types)
{
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
g_return_val_if_fail (types != 0, NULL);
return gst_bus_timed_pop_filtered (bus, 0, types);
}
/**
* gst_bus_pop:
* @bus: a #GstBus to pop
*
* Get a message from the bus.
*
* Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
* bus is empty. The message is taken from the bus and needs to be unreffed
* with gst_message_unref() after usage.
*
* MT safe.
*/
GstMessage *
gst_bus_pop (GstBus * bus)
{
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
return gst_bus_timed_pop_filtered (bus, 0, GST_MESSAGE_ANY);
}
/**
* gst_bus_peek:
* @bus: a #GstBus
*
* Peek the message on the top of the bus' queue. The message will remain
* on the bus' message queue. A reference is returned, and needs to be unreffed
* by the caller.
*
* Returns: (transfer full): the #GstMessage that is on the bus, or NULL if the
* bus is empty.
*
* MT safe.
*/
GstMessage *
gst_bus_peek (GstBus * bus)
{
GstMessage *message;
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
g_mutex_lock (bus->queue_lock);
message = gst_atomic_queue_peek (bus->queue);
if (message)
gst_message_ref (message);
g_mutex_unlock (bus->queue_lock);
GST_DEBUG_OBJECT (bus, "peek on bus, got message %p", message);
return message;
}
/**
* gst_bus_set_sync_handler:
* @bus: a #GstBus to install the handler on
* @func: The handler function to install
* @data: User data that will be sent to the handler function.
*
* Sets the synchronous handler on the bus. The function will be called
* every time a new message is posted on the bus. Note that the function
* will be called in the same thread context as the posting object. This
* function is usually only called by the creator of the bus. Applications
* should handle messages asynchronously using the gst_bus watch and poll
* functions.
*
* You cannot replace an existing sync_handler. You can pass NULL to this
* function, which will clear the existing handler.
*/
void
gst_bus_set_sync_handler (GstBus * bus, GstBusSyncHandler func, gpointer data)
{
g_return_if_fail (GST_IS_BUS (bus));
GST_OBJECT_LOCK (bus);
/* Assert if the user attempts to replace an existing sync_handler,
* other than to clear it */
if (func != NULL && bus->sync_handler != NULL)
goto no_replace;
bus->sync_handler = func;
bus->sync_handler_data = data;
GST_OBJECT_UNLOCK (bus);
return;
no_replace:
{
GST_OBJECT_UNLOCK (bus);
g_warning ("cannot replace existing sync handler");
return;
}
}
/* GSource for the bus
*/
typedef struct
{
GSource source;
GstBus *bus;
} GstBusSource;
static gboolean
gst_bus_source_prepare (GSource * source, gint * timeout)
{
*timeout = -1;
return FALSE;
}
static gboolean
gst_bus_source_check (GSource * source)
{
GstBusSource *bsrc = (GstBusSource *) source;
return bsrc->bus->priv->pollfd.revents & (G_IO_IN | G_IO_HUP | G_IO_ERR);
}
static gboolean
gst_bus_source_dispatch (GSource * source, GSourceFunc callback,
gpointer user_data)
{
GstBusFunc handler = (GstBusFunc) callback;
GstBusSource *bsource = (GstBusSource *) source;
GstMessage *message;
gboolean keep;
GstBus *bus;
g_return_val_if_fail (bsource != NULL, FALSE);
bus = bsource->bus;
g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
message = gst_bus_pop (bus);
/* The message queue might be empty if some other thread or callback set
* the bus to flushing between check/prepare and dispatch */
if (G_UNLIKELY (message == NULL))
return TRUE;
if (!handler)
goto no_handler;
GST_DEBUG_OBJECT (bus, "source %p calling dispatch with %p", source, message);
keep = handler (bus, message, user_data);
gst_message_unref (message);
GST_DEBUG_OBJECT (bus, "source %p handler returns %d", source, keep);
return keep;
no_handler:
{
g_warning ("GstBus watch dispatched without callback\n"
"You must call g_source_set_callback().");
gst_message_unref (message);
return FALSE;
}
}
static void
gst_bus_source_finalize (GSource * source)
{
GstBusSource *bsource = (GstBusSource *) source;
GstBus *bus;
bus = bsource->bus;
GST_DEBUG_OBJECT (bus, "finalize source %p", source);
GST_OBJECT_LOCK (bus);
if (bus->priv->watch_id == source)
bus->priv->watch_id = NULL;
GST_OBJECT_UNLOCK (bus);
gst_object_unref (bsource->bus);
bsource->bus = NULL;
}
static GSourceFuncs gst_bus_source_funcs = {
gst_bus_source_prepare,
gst_bus_source_check,
gst_bus_source_dispatch,
gst_bus_source_finalize
};
/**
* gst_bus_create_watch:
* @bus: a #GstBus to create the watch for
*
* Create watch for this bus. The GSource will be dispatched whenever
* a message is on the bus. After the GSource is dispatched, the
* message is popped off the bus and unreffed.
*
* Returns: (transfer full): a #GSource that can be added to a mainloop.
*/
GSource *
gst_bus_create_watch (GstBus * bus)
{
GstBusSource *source;
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
sizeof (GstBusSource));
source->bus = gst_object_ref (bus);
g_source_add_poll ((GSource *) source, &bus->priv->pollfd);
return (GSource *) source;
}
/* must be called with the bus OBJECT LOCK */
static guint
gst_bus_add_watch_full_unlocked (GstBus * bus, gint priority,
GstBusFunc func, gpointer user_data, GDestroyNotify notify)
{
GMainContext *ctx;
guint id;
GSource *source;
if (bus->priv->watch_id) {
GST_ERROR_OBJECT (bus,
"Tried to add new watch while one was already there");
return 0;
}
source = gst_bus_create_watch (bus);
if (priority != G_PRIORITY_DEFAULT)
g_source_set_priority (source, priority);
g_source_set_callback (source, (GSourceFunc) func, user_data, notify);
ctx = g_main_context_get_thread_default ();
id = g_source_attach (source, ctx);
g_source_unref (source);
if (id) {
bus->priv->watch_id = source;
}
GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
return id;
}
/**
* gst_bus_add_watch_full:
* @bus: a #GstBus to create the watch for.
* @priority: The priority of the watch.
* @func: A function to call when a message is received.
* @user_data: user data passed to @func.
* @notify: the function to call when the source is removed.
*
* Adds a bus watch to the default main context with the given @priority (e.g.
* %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
* main context set up using g_main_context_push_thread_default() (before
* one had to create a bus watch source and attach it to the desired main
* context 'manually').
*
* This function is used to receive asynchronous messages in the main loop.
* There can only be a single bus watch per bus, you must remove it before you
* can set a new one.
*
* When @func is called, the message belongs to the caller; if you want to
* keep a copy of it, call gst_message_ref() before leaving @func.
*
* The watch can be removed using g_source_remove() or by returning FALSE
* from @func.
*
* Returns: The event source id.
*
* MT safe.
*/
guint
gst_bus_add_watch_full (GstBus * bus, gint priority,
GstBusFunc func, gpointer user_data, GDestroyNotify notify)
{
guint id;
g_return_val_if_fail (GST_IS_BUS (bus), 0);
GST_OBJECT_LOCK (bus);
id = gst_bus_add_watch_full_unlocked (bus, priority, func, user_data, notify);
GST_OBJECT_UNLOCK (bus);
return id;
}
/**
* gst_bus_add_watch:
* @bus: a #GstBus to create the watch for
* @func: A function to call when a message is received.
* @user_data: user data passed to @func.
*
* Adds a bus watch to the default main context with the default priority
* (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
* main context set up using g_main_context_push_thread_default() (before
* one had to create a bus watch source and attach it to the desired main
* context 'manually').
*
* This function is used to receive asynchronous messages in the main loop.
* There can only be a single bus watch per bus, you must remove it before you
* can set a new one.
*
* The watch can be removed using g_source_remove() or by returning FALSE
* from @func.
*
* Returns: The event source id.
*
* MT safe.
*/
guint
gst_bus_add_watch (GstBus * bus, GstBusFunc func, gpointer user_data)
{
return gst_bus_add_watch_full (bus, G_PRIORITY_DEFAULT, func,
user_data, NULL);
}
typedef struct
{
GMainLoop *loop;
guint timeout_id;
gboolean source_running;
GstMessageType events;
GstMessage *message;
} GstBusPollData;
static void
poll_func (GstBus * bus, GstMessage * message, GstBusPollData * poll_data)
{
GstMessageType type;
if (!g_main_loop_is_running (poll_data->loop)) {
GST_DEBUG ("mainloop %p not running", poll_data->loop);
return;
}
type = GST_MESSAGE_TYPE (message);
if (type & poll_data->events) {
g_assert (poll_data->message == NULL);
/* keep ref to message */
poll_data->message = gst_message_ref (message);
GST_DEBUG ("mainloop %p quit", poll_data->loop);
g_main_loop_quit (poll_data->loop);
} else {
GST_DEBUG ("type %08x does not match %08x", type, poll_data->events);
}
}
static gboolean
poll_timeout (GstBusPollData * poll_data)
{
GST_DEBUG ("mainloop %p quit", poll_data->loop);
g_main_loop_quit (poll_data->loop);
/* we don't remove the GSource as this would free our poll_data,
* which we still need */
return TRUE;
}
static void
poll_destroy (GstBusPollData * poll_data, gpointer unused)
{
poll_data->source_running = FALSE;
if (!poll_data->timeout_id) {
g_main_loop_unref (poll_data->loop);
g_slice_free (GstBusPollData, poll_data);
}
}
static void
poll_destroy_timeout (GstBusPollData * poll_data)
{
poll_data->timeout_id = 0;
if (!poll_data->source_running) {
g_main_loop_unref (poll_data->loop);
g_slice_free (GstBusPollData, poll_data);
}
}
/**
* gst_bus_poll:
* @bus: a #GstBus
* @events: a mask of #GstMessageType, representing the set of message types to
* poll for.
* @timeout: the poll timeout, as a #GstClockTimeDiff, or -1 to poll
* indefinitely.
*
* Poll the bus for messages. Will block while waiting for messages to come.
* You can specify a maximum time to poll with the @timeout parameter. If
* @timeout is negative, this function will block indefinitely.
*
* All messages not in @events will be popped off the bus and will be ignored.
*
* Because poll is implemented using the "message" signal enabled by
* gst_bus_add_signal_watch(), calling gst_bus_poll() will cause the "message"
* signal to be emitted for every message that poll sees. Thus a "message"
* signal handler will see the same messages that this function sees -- neither
* will steal messages from the other.
*
* This function will run a main loop from the default main context when
* polling.
*
* You should never use this function, since it is pure evil. This is
* especially true for GUI applications based on Gtk+ or Qt, but also for any
* other non-trivial application that uses the GLib main loop. As this function
* runs a GLib main loop, any callback attached to the default GLib main
* context may be invoked. This could be timeouts, GUI events, I/O events etc.;
* even if gst_bus_poll() is called with a 0 timeout. Any of these callbacks
* may do things you do not expect, e.g. destroy the main application window or
* some other resource; change other application state; display a dialog and
* run another main loop until the user clicks it away. In short, using this
* function may add a lot of complexity to your code through unexpected
* re-entrancy and unexpected changes to your application's state.
*
* For 0 timeouts use gst_bus_pop_filtered() instead of this function; for
* other short timeouts use gst_bus_timed_pop_filtered(); everything else is
* better handled by setting up an asynchronous bus watch and doing things
* from there.
*
* Returns: (transfer full): the message that was received, or NULL if the
* poll timed out. The message is taken from the bus and needs to be
* unreffed with gst_message_unref() after usage.
*/
GstMessage *
gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
{
GstBusPollData *poll_data;
GstMessage *ret;
gulong id;
poll_data = g_slice_new (GstBusPollData);
poll_data->source_running = TRUE;
poll_data->loop = g_main_loop_new (NULL, FALSE);
poll_data->events = events;
poll_data->message = NULL;
if (timeout >= 0)
poll_data->timeout_id = g_timeout_add_full (G_PRIORITY_DEFAULT_IDLE,
timeout / GST_MSECOND, (GSourceFunc) poll_timeout, poll_data,
(GDestroyNotify) poll_destroy_timeout);
else
poll_data->timeout_id = 0;
id = g_signal_connect_data (bus, "message", G_CALLBACK (poll_func), poll_data,
(GClosureNotify) poll_destroy, 0);
/* these can be nested, so it's ok */
gst_bus_add_signal_watch (bus);
GST_DEBUG ("running mainloop %p", poll_data->loop);
g_main_loop_run (poll_data->loop);
GST_DEBUG ("mainloop stopped %p", poll_data->loop);
gst_bus_remove_signal_watch (bus);
/* holds a ref */
ret = poll_data->message;
if (poll_data->timeout_id)
g_source_remove (poll_data->timeout_id);
/* poll_data will be freed now */
g_signal_handler_disconnect (bus, id);
GST_DEBUG_OBJECT (bus, "finished poll with message %p", ret);
return ret;
}
/**
* gst_bus_async_signal_func:
* @bus: a #GstBus
* @message: the #GstMessage received
* @data: user data
*
* A helper #GstBusFunc that can be used to convert all asynchronous messages
* into signals.
*
* Returns: TRUE
*/
gboolean
gst_bus_async_signal_func (GstBus * bus, GstMessage * message, gpointer data)
{
GQuark detail = 0;
g_return_val_if_fail (GST_IS_BUS (bus), TRUE);
g_return_val_if_fail (message != NULL, TRUE);
detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
g_signal_emit (bus, gst_bus_signals[ASYNC_MESSAGE], detail, message);
/* we never remove this source based on signal emission return values */
return TRUE;
}
/**
* gst_bus_sync_signal_handler:
* @bus: a #GstBus
* @message: the #GstMessage received
* @data: user data
*
* A helper GstBusSyncHandler that can be used to convert all synchronous
* messages into signals.
*
* Returns: GST_BUS_PASS
*/
GstBusSyncReply
gst_bus_sync_signal_handler (GstBus * bus, GstMessage * message, gpointer data)
{
GQuark detail = 0;
g_return_val_if_fail (GST_IS_BUS (bus), GST_BUS_DROP);
g_return_val_if_fail (message != NULL, GST_BUS_DROP);
detail = gst_message_type_to_quark (GST_MESSAGE_TYPE (message));
g_signal_emit (bus, gst_bus_signals[SYNC_MESSAGE], detail, message);
return GST_BUS_PASS;
}
/**
* gst_bus_enable_sync_message_emission:
* @bus: a #GstBus on which you want to receive the "sync-message" signal
*
* Instructs GStreamer to emit the "sync-message" signal after running the bus's
* sync handler. This function is here so that code can ensure that they can
* synchronously receive messages without having to affect what the bin's sync
* handler is.
*
* This function may be called multiple times. To clean up, the caller is
* responsible for calling gst_bus_disable_sync_message_emission() as many times
* as this function is called.
*
* While this function looks similar to gst_bus_add_signal_watch(), it is not
* exactly the same -- this function enables <emphasis>synchronous</emphasis> emission of
* signals when messages arrive; gst_bus_add_signal_watch() adds an idle callback
* to pop messages off the bus <emphasis>asynchronously</emphasis>. The sync-message signal
* comes from the thread of whatever object posted the message; the "message"
* signal is marshalled to the main thread via the main loop.
*
* MT safe.
*/
void
gst_bus_enable_sync_message_emission (GstBus * bus)
{
g_return_if_fail (GST_IS_BUS (bus));
GST_OBJECT_LOCK (bus);
bus->priv->num_sync_message_emitters++;
GST_OBJECT_UNLOCK (bus);
}
/**
* gst_bus_disable_sync_message_emission:
* @bus: a #GstBus on which you previously called
* gst_bus_enable_sync_message_emission()
*
* Instructs GStreamer to stop emitting the "sync-message" signal for this bus.
* See gst_bus_enable_sync_message_emission() for more information.
*
* In the event that multiple pieces of code have called
* gst_bus_enable_sync_message_emission(), the sync-message emissions will only
* be stopped after all calls to gst_bus_enable_sync_message_emission() were
* "cancelled" by calling this function. In this way the semantics are exactly
* the same as gst_object_ref() that which calls enable should also call
* disable.
*
* MT safe.
*/
void
gst_bus_disable_sync_message_emission (GstBus * bus)
{
g_return_if_fail (GST_IS_BUS (bus));
g_return_if_fail (bus->num_signal_watchers == 0);
GST_OBJECT_LOCK (bus);
bus->priv->num_sync_message_emitters--;
GST_OBJECT_UNLOCK (bus);
}
/**
* gst_bus_add_signal_watch_full:
* @bus: a #GstBus on which you want to receive the "message" signal
* @priority: The priority of the watch.
*
* Adds a bus signal watch to the default main context with the given @priority
* (e.g. %G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a
* non-default main context set up using g_main_context_push_thread_default()
* (before one had to create a bus watch source and attach it to the desired
* main context 'manually').
*
* After calling this statement, the bus will emit the "message" signal for each
* message posted on the bus when the main loop is running.
*
* This function may be called multiple times. To clean up, the caller is
* responsible for calling gst_bus_remove_signal_watch() as many times as this
* function is called.
*
* There can only be a single bus watch per bus, you most remove all signal watch
* before you can set another type of watch.
*
* MT safe.
*/
void
gst_bus_add_signal_watch_full (GstBus * bus, gint priority)
{
g_return_if_fail (GST_IS_BUS (bus));
/* I know the callees don't take this lock, so go ahead and abuse it */
GST_OBJECT_LOCK (bus);
if (bus->num_signal_watchers > 0)
goto done;
/* this should not fail because the counter above takes care of it */
g_assert (bus->signal_watch_id == 0);
bus->signal_watch_id =
gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
NULL, NULL);
if (G_UNLIKELY (bus->signal_watch_id == 0))
goto add_failed;
done:
bus->num_signal_watchers++;
GST_OBJECT_UNLOCK (bus);
return;
/* ERRORS */
add_failed:
{
g_critical ("Could not add signal watch to bus %s", GST_OBJECT_NAME (bus));
GST_OBJECT_UNLOCK (bus);
return;
}
}
/**
* gst_bus_add_signal_watch:
* @bus: a #GstBus on which you want to receive the "message" signal
*
* Adds a bus signal watch to the default main context with the default priority
* (%G_PRIORITY_DEFAULT). Since 0.10.33 it is also possible to use a non-default
* main context set up using g_main_context_push_thread_default() (before
* one had to create a bus watch source and attach it to the desired main
* context 'manually').
*
* After calling this statement, the bus will emit the "message" signal for each
* message posted on the bus.
*
* This function may be called multiple times. To clean up, the caller is
* responsible for calling gst_bus_remove_signal_watch() as many times as this
* function is called.
*
* MT safe.
*/
void
gst_bus_add_signal_watch (GstBus * bus)
{
gst_bus_add_signal_watch_full (bus, G_PRIORITY_DEFAULT);
}
/**
* gst_bus_remove_signal_watch:
* @bus: a #GstBus you previously added a signal watch to
*
* Removes a signal watch previously added with gst_bus_add_signal_watch().
*
* MT safe.
*/
void
gst_bus_remove_signal_watch (GstBus * bus)
{
guint id = 0;
g_return_if_fail (GST_IS_BUS (bus));
/* I know the callees don't take this lock, so go ahead and abuse it */
GST_OBJECT_LOCK (bus);
if (bus->num_signal_watchers == 0)
goto error;
bus->num_signal_watchers--;
if (bus->num_signal_watchers > 0)
goto done;
id = bus->signal_watch_id;
bus->signal_watch_id = 0;
GST_DEBUG_OBJECT (bus, "removing signal watch %u", id);
done:
GST_OBJECT_UNLOCK (bus);
if (id)
g_source_remove (id);
return;
/* ERRORS */
error:
{
g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
GST_OBJECT_UNLOCK (bus);
return;
}
}