/* 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., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstbus
* @title: 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.
*/
#include "gst_private.h"
#include <errno.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <sys/types.h>
#include "gstatomicqueue.h"
#include "gstinfo.h"
#include "gstpoll.h"
#include "gstbus.h"
#include "glib-compat-private.h"
#ifdef G_OS_WIN32
# ifndef EWOULDBLOCK
# define EWOULDBLOCK EAGAIN /* This is just to placate gcc */
# endif
#endif /* G_OS_WIN32 */
#define GST_CAT_DEFAULT GST_CAT_BUS
/* bus signals */
enum
{
SYNC_MESSAGE,
ASYNC_MESSAGE,
/* add more above */
LAST_SIGNAL
};
#define DEFAULT_ENABLE_ASYNC (TRUE)
enum
{
PROP_0,
PROP_ENABLE_ASYNC
};
static void gst_bus_dispose (GObject * object);
static void gst_bus_finalize (GObject * object);
static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
struct _GstBusPrivate
{
GstAtomicQueue *queue;
GMutex queue_lock;
GstBusSyncHandler sync_handler;
gpointer sync_handler_data;
GDestroyNotify sync_handler_notify;
guint num_signal_watchers;
guint num_sync_message_emitters;
GSource *signal_watch;
gboolean enable_async;
GstPoll *poll;
GPollFD pollfd;
};
#define gst_bus_parent_class parent_class
G_DEFINE_TYPE (GstBus, gst_bus, GST_TYPE_OBJECT);
static void
gst_bus_set_property (GObject * object,
guint prop_id, const GValue * value, GParamSpec * pspec)
{
GstBus *bus = GST_BUS_CAST (object);
switch (prop_id) {
case PROP_ENABLE_ASYNC:
bus->priv->enable_async = g_value_get_boolean (value);
break;
default:
G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
break;
}
}
static void
gst_bus_constructed (GObject * object)
{
GstBus *bus = GST_BUS_CAST (object);
if (bus->priv->enable_async) {
bus->priv->poll = gst_poll_new_timer ();
gst_poll_get_read_gpollfd (bus->priv->poll, &bus->priv->pollfd);
}
G_OBJECT_CLASS (gst_bus_parent_class)->constructed (object);
}
static void
gst_bus_class_init (GstBusClass * klass)
{
GObjectClass *gobject_class = (GObjectClass *) klass;
gobject_class->dispose = gst_bus_dispose;
gobject_class->finalize = gst_bus_finalize;
gobject_class->set_property = gst_bus_set_property;
gobject_class->constructed = gst_bus_constructed;
/**
* GstBus::enable-async:
*
* Enable async message delivery support for bus watches,
* gst_bus_pop() and similar API. Without this only the
* synchronous message handlers are called.
*
* This property is used to create the child element buses
* in #GstBin.
*/
g_object_class_install_property (gobject_class, PROP_ENABLE_ASYNC,
g_param_spec_boolean ("enable-async", "Enable Async",
"Enable async message delivery for bus watches and gst_bus_pop()",
DEFAULT_ENABLE_ASYNC,
G_PARAM_CONSTRUCT_ONLY | G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS));
/**
* 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 call
* gst_bus_enable_sync_message_emission() before.
*/
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,
g_cclosure_marshal_generic, 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,
g_cclosure_marshal_generic, G_TYPE_NONE, 1, GST_TYPE_MESSAGE);
g_type_class_add_private (klass, sizeof (GstBusPrivate));
}
static void
gst_bus_init (GstBus * bus)
{
bus->priv = G_TYPE_INSTANCE_GET_PRIVATE (bus, GST_TYPE_BUS, GstBusPrivate);
bus->priv->enable_async = DEFAULT_ENABLE_ASYNC;
g_mutex_init (&bus->priv->queue_lock);
bus->priv->queue = gst_atomic_queue_new (32);
GST_DEBUG_OBJECT (bus, "created");
}
static void
gst_bus_dispose (GObject * object)
{
GstBus *bus = GST_BUS (object);
if (bus->priv->queue) {
GstMessage *message;
g_mutex_lock (&bus->priv->queue_lock);
do {
message = gst_atomic_queue_pop (bus->priv->queue);
if (message)
gst_message_unref (message);
} while (message != NULL);
gst_atomic_queue_unref (bus->priv->queue);
bus->priv->queue = NULL;
g_mutex_unlock (&bus->priv->queue_lock);
g_mutex_clear (&bus->priv->queue_lock);
if (bus->priv->poll)
gst_poll_free (bus->priv->poll);
bus->priv->poll = NULL;
}
G_OBJECT_CLASS (parent_class)->dispose (object);
}
static void
gst_bus_finalize (GObject * object)
{
GstBus *bus = GST_BUS (object);
if (bus->priv->sync_handler_notify)
bus->priv->sync_handler_notify (bus->priv->sync_handler_data);
G_OBJECT_CLASS (parent_class)->finalize (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_new (gst_bus_get_type (), NULL);
GST_DEBUG_OBJECT (result, "created new bus");
/* clear floating flag */
gst_object_ref_sink (result);
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 %" GST_PTR_FORMAT, message,
message);
/* check we didn't accidentally add a public flag that maps to same value */
g_assert (!GST_MINI_OBJECT_FLAG_IS_SET (message,
GST_MESSAGE_FLAG_ASYNC_DELIVERY));
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->priv->sync_handler;
handler_data = bus->priv->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);
/* If this is a bus without async message delivery
* always drop the message */
if (!bus->priv->poll)
reply = GST_BUS_DROP;
/* 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->priv->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 */
GCond *cond = GST_MESSAGE_GET_COND (message);
GMutex *lock = GST_MESSAGE_GET_LOCK (message);
g_cond_init (cond);
g_mutex_init (lock);
GST_MINI_OBJECT_FLAG_SET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
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->priv->queue, message);
gst_poll_write_control (bus->priv->poll);
/* now block till the message is freed */
g_cond_wait (cond, lock);
/* we acquired a new ref from gst_message_dispose() so we can clean up */
g_mutex_unlock (lock);
GST_DEBUG_OBJECT (bus, "[msg %p] delivered asynchronously", message);
GST_MINI_OBJECT_FLAG_UNSET (message, GST_MESSAGE_FLAG_ASYNC_DELIVERY);
g_mutex_clear (lock);
g_cond_clear (cond);
gst_message_unref (message);
break;
}
default:
g_warning ("invalid return from bus sync handler");
break;
}
return TRUE;
/* ERRORS */
is_flushing:
{
GST_DEBUG_OBJECT (bus, "bus is flushing");
GST_OBJECT_UNLOCK (bus);
gst_message_unref (message);
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->priv->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;
GList *message_list = NULL;
g_return_if_fail (GST_IS_BUS (bus));
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)))
message_list = g_list_prepend (message_list, message);
} else {
GST_DEBUG_OBJECT (bus, "unset bus flushing");
GST_OBJECT_FLAG_UNSET (bus, GST_BUS_FLUSHING);
}
GST_OBJECT_UNLOCK (bus);
g_list_free_full (message_list, (GDestroyNotify) gst_message_unref);
}
/**
* 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) (nullable): 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.
*/
GstMessage *
gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
GstMessageType types)
{
GstMessage *message;
GTimeVal now, then;
gboolean first_round = TRUE;
GstClockTime elapsed = 0;
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
g_return_val_if_fail (types != 0, NULL);
g_return_val_if_fail (timeout == 0 || bus->priv->poll != NULL, NULL);
g_mutex_lock (&bus->priv->queue_lock);
while (TRUE) {
gint ret;
GST_LOG_OBJECT (bus, "have %d messages",
gst_atomic_queue_length (bus->priv->queue));
while ((message = gst_atomic_queue_pop (bus->priv->queue))) {
if (bus->priv->poll) {
while (!gst_poll_read_control (bus->priv->poll)) {
if (errno == EWOULDBLOCK) {
/* Retry, this can happen if pushing to the queue has finished,
* popping here succeeded but writing control did not finish
* before we got to this line. */
/* Give other threads the chance to do something */
g_thread_yield ();
continue;
} else {
/* This is a real error and means that either the bus is in an
* inconsistent state, or the GstPoll is invalid. GstPoll already
* prints a critical warning about this, no need to do that again
* ourselves */
break;
}
}
}
GST_DEBUG_OBJECT (bus, "got message %p, %s from %s, type mask is %u",
message, GST_MESSAGE_TYPE_NAME (message),
GST_MESSAGE_SRC_NAME (message), (guint) types);
if ((GST_MESSAGE_TYPE (message) & types) != 0) {
/* Extra check to ensure extended types don't get matched unless
* asked for */
if ((!GST_MESSAGE_TYPE_IS_EXTENDED (message))
|| (types & GST_MESSAGE_EXTENDED)) {
/* exit the loop, we have a message */
goto beach;
}
}
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 {
g_get_current_time (&now);
elapsed = GST_TIMEVAL_TO_TIME (now) - GST_TIMEVAL_TO_TIME (then);
if (elapsed > timeout)
break;
}
}
/* only here in timeout case */
g_assert (bus->priv->poll);
g_mutex_unlock (&bus->priv->queue_lock);
ret = gst_poll_wait (bus->priv->poll, timeout - elapsed);
g_mutex_lock (&bus->priv->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->priv->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) (nullable): 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.
*/
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. It is not possible to use message
* enums beyond #GST_MESSAGE_EXTENDED in the @events mask.
*
* Returns: (transfer full) (nullable): 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.
*/
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) (nullable): 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) (nullable): 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->priv->queue_lock);
message = gst_atomic_queue_peek (bus->priv->queue);
if (message)
gst_message_ref (message);
g_mutex_unlock (&bus->priv->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: (allow-none): The handler function to install
* @user_data: User data that will be sent to the handler function.
* @notify: called when @user_data becomes unused
*
* 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 user_data, GDestroyNotify notify)
{
GDestroyNotify old_notify;
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->priv->sync_handler != NULL)
goto no_replace;
if ((old_notify = bus->priv->sync_handler_notify)) {
gpointer old_data = bus->priv->sync_handler_data;
bus->priv->sync_handler_data = NULL;
bus->priv->sync_handler_notify = NULL;
GST_OBJECT_UNLOCK (bus);
old_notify (old_data);
GST_OBJECT_LOCK (bus);
}
bus->priv->sync_handler = func;
bus->priv->sync_handler_data = user_data;
bus->priv->sync_handler_notify = notify;
GST_OBJECT_UNLOCK (bus);
return;
no_replace:
{
GST_OBJECT_UNLOCK (bus);
g_warning ("cannot replace existing sync handler");
return;
}
}
/**
* gst_bus_get_pollfd:
* @bus: A #GstBus
* @fd: A GPollFD to fill
*
* Gets the file descriptor from the bus which can be used to get notified about
* messages being available with functions like g_poll(), and allows integration
* into other event loops based on file descriptors.
* Whenever a message is available, the POLLIN / %G_IO_IN event is set.
*
* Warning: NEVER read or write anything to the returned fd but only use it
* for getting notifications via g_poll() or similar and then use the normal
* GstBus API, e.g. gst_bus_pop().
*
* Since: 1.14
*/
void
gst_bus_get_pollfd (GstBus * bus, GPollFD * fd)
{
g_return_if_fail (GST_IS_BUS (bus));
g_return_if_fail (bus->priv->poll != NULL);
*fd = bus->priv->pollfd;
}
/* 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 %" GST_PTR_FORMAT,
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->signal_watch == source)
bus->priv->signal_watch = 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) (nullable): 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);
g_return_val_if_fail (bus->priv->poll != NULL, NULL);
source = (GstBusSource *) g_source_new (&gst_bus_source_funcs,
sizeof (GstBusSource));
g_source_set_name ((GSource *) source, "GStreamer message bus watch");
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->signal_watch) {
GST_ERROR_OBJECT (bus,
"Tried to add new watch while one was already there");
return 0;
}
source = gst_bus_create_watch (bus);
if (!source) {
g_critical ("Creating bus watch failed");
return 0;
}
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->signal_watch = source;
}
GST_DEBUG_OBJECT (bus, "New source %p with id %u", source, id);
return id;
}
/**
* gst_bus_add_watch_full: (rename-to gst_bus_add_watch)
* @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). 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 bus watch will only work if a GLib main loop is being run.
*
* 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 gst_bus_remove_watch() or by returning %FALSE
* from @func. If the watch was added to the default main context it is also
* possible to remove the watch using g_source_remove().
*
* The bus watch will take its own reference to the @bus, so it is safe to unref
* @bus using gst_object_unref() after setting the bus watch.
*
* MT safe.
*
* Returns: The event source id or 0 if @bus already got an event source.
*/
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: (skip)
* @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). 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 bus watch will only work if a GLib main loop is being run.
*
* The watch can be removed using gst_bus_remove_watch() or by returning %FALSE
* from @func. If the watch was added to the default main context it is also
* possible to remove the watch using g_source_remove().
*
* The bus watch will take its own reference to the @bus, so it is safe to unref
* @bus using gst_object_unref() after setting the bus watch.
*
* MT safe.
*
* Returns: The event source id or 0 if @bus already got an event source.
*/
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);
}
/**
* gst_bus_remove_watch:
* @bus: a #GstBus to remove the watch from.
*
* Removes an installed bus watch from @bus.
*
* Returns: %TRUE on success or %FALSE if @bus has no event source.
*
* Since: 1.6
*
*/
gboolean
gst_bus_remove_watch (GstBus * bus)
{
GSource *watch_id;
g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
GST_OBJECT_LOCK (bus);
if (bus->priv->signal_watch == NULL) {
GST_ERROR_OBJECT (bus, "no bus watch was present");
goto no_watch;
}
watch_id = bus->priv->signal_watch;
GST_OBJECT_UNLOCK (bus);
g_source_destroy (watch_id);
return TRUE;
no_watch:
GST_OBJECT_UNLOCK (bus);
return FALSE;
}
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 (note special handling of extended message types below)
* @timeout: the poll timeout, as a #GstClockTime, or #GST_CLOCK_TIME_NONE 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.
* It is not possible to use message enums beyond #GST_MESSAGE_EXTENDED in the
* @events mask
*
* 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) (nullable): 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, GstClockTime timeout)
{
GstBusPollData *poll_data;
GstMessage *ret;
gulong id;
g_return_val_if_fail (GST_IS_BUS (bus), NULL);
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 != GST_CLOCK_TIME_NONE)
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->priv->num_sync_message_emitters > 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). 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 must remove any 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->priv->num_signal_watchers > 0)
goto done;
/* this should not fail because the counter above takes care of it */
g_assert (!bus->priv->signal_watch);
gst_bus_add_watch_full_unlocked (bus, priority, gst_bus_async_signal_func,
NULL, NULL);
if (G_UNLIKELY (!bus->priv->signal_watch))
goto add_failed;
done:
bus->priv->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). 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)
{
GSource *source = NULL;
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->priv->num_signal_watchers == 0)
goto error;
bus->priv->num_signal_watchers--;
if (bus->priv->num_signal_watchers > 0)
goto done;
GST_DEBUG_OBJECT (bus, "removing signal watch %u",
g_source_get_id (bus->priv->signal_watch));
source = bus->priv->signal_watch;
done:
GST_OBJECT_UNLOCK (bus);
if (source)
g_source_destroy (source);
return;
/* ERRORS */
error:
{
g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
GST_OBJECT_UNLOCK (bus);
return;
}
}