--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gstreamer_core/gst/gstbus.c	Thu Dec 17 08:53:32 2009 +0200
@@ -0,0 +1,1346 @@
+/* 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 #GstMessages in
+ * a first-in first-out way from the streaming threads 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 _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 "gstbus.h"
+
+#ifdef __SYMBIAN32__
+#include <glib_global.h>
+#endif
+
+#define GST_CAT_DEFAULT GST_CAT_BUS
+/* bus signals */
+enum
+{
+  SYNC_MESSAGE,
+  ASYNC_MESSAGE,
+  /* add more above */
+  LAST_SIGNAL
+};
+
+static void gst_bus_class_init (GstBusClass * klass);
+static void gst_bus_init (GstBus * bus);
+static void gst_bus_dispose (GObject * object);
+
+static void gst_bus_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec);
+static void gst_bus_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec);
+
+static GstObjectClass *parent_class = NULL;
+static guint gst_bus_signals[LAST_SIGNAL] = { 0 };
+
+/* the context we wakeup when we posted a message on the bus */
+static GMainContext *main_context;
+
+struct _GstBusPrivate
+{
+  guint num_sync_message_emitters;
+
+  GCond *queue_cond;
+};
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+
+GType
+gst_bus_get_type (void)
+{
+  static GType bus_type = 0;
+
+  if (G_UNLIKELY (bus_type == 0)) {
+    static const GTypeInfo bus_info = {
+      sizeof (GstBusClass),
+      NULL,
+      NULL,
+      (GClassInitFunc) gst_bus_class_init,
+      NULL,
+      NULL,
+      sizeof (GstBus),
+      0,
+      (GInstanceInitFunc) gst_bus_init,
+      NULL
+    };
+
+    bus_type = g_type_register_static (GST_TYPE_OBJECT, "GstBus", &bus_info, 0);
+  }
+  return bus_type;
+}
+
+/* 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;
+  GstObjectClass *gstobject_class;
+
+  gobject_class = (GObjectClass *) klass;
+  gstobject_class = (GstObjectClass *) klass;
+
+  parent_class = g_type_class_peek_parent (klass);
+
+  if (!g_thread_supported ())
+    g_thread_init (NULL);
+
+  gobject_class->dispose = GST_DEBUG_FUNCPTR (gst_bus_dispose);
+  gobject_class->set_property = GST_DEBUG_FUNCPTR (gst_bus_set_property);
+  gobject_class->get_property = GST_DEBUG_FUNCPTR (gst_bus_get_property);
+
+  /**
+   * 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);
+
+  main_context = g_main_context_default ();
+
+  g_type_class_add_private (klass, sizeof (GstBusPrivate));
+}
+
+static void
+gst_bus_init (GstBus * bus)
+{
+  bus->queue = g_queue_new ();
+  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 ();
+
+  GST_DEBUG_OBJECT (bus, "created");
+}
+
+static void
+gst_bus_dispose (GObject * object)
+{
+  GstBus *bus;
+
+  bus = GST_BUS (object);
+
+  if (bus->queue) {
+    GstMessage *message;
+
+    g_mutex_lock (bus->queue_lock);
+    do {
+      message = g_queue_pop_head (bus->queue);
+      if (message)
+        gst_message_unref (message);
+    } while (message != NULL);
+    g_queue_free (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;
+  }
+
+  G_OBJECT_CLASS (parent_class)->dispose (object);
+}
+
+static void
+gst_bus_set_property (GObject * object, guint prop_id,
+    const GValue * value, GParamSpec * pspec)
+{
+  GstBus *bus;
+
+  bus = GST_BUS (object);
+
+  switch (prop_id) {
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+static void
+gst_bus_get_property (GObject * object, guint prop_id,
+    GValue * value, GParamSpec * pspec)
+{
+  GstBus *bus;
+
+  bus = GST_BUS (object);
+
+  switch (prop_id) {
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+  }
+}
+
+/**
+ * gst_bus_new:
+ *
+ * Creates a new #GstBus instance.
+ *
+ * Returns: a new #GstBus instance
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstBus *
+gst_bus_new (void)
+{
+  GstBus *result;
+
+  result = g_object_new (gst_bus_get_type (), NULL);
+  GST_DEBUG_OBJECT (result, "created new bus");
+
+  return result;
+}
+
+/**
+ * gst_bus_post:
+ * @bus: a #GstBus to post on
+ * @message: 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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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);
+      g_mutex_lock (bus->queue_lock);
+      g_queue_push_tail (bus->queue, message);
+      g_cond_broadcast (bus->priv->queue_cond);
+      g_mutex_unlock (bus->queue_lock);
+      GST_DEBUG_OBJECT (bus, "[msg %p] pushed on async queue", message);
+
+      /* FIXME cannot assume sources are only in the default context */
+      g_main_context_wakeup (main_context);
+
+      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);
+      g_mutex_lock (bus->queue_lock);
+      g_queue_push_tail (bus->queue, message);
+      g_cond_broadcast (bus->priv->queue_cond);
+      g_mutex_unlock (bus->queue_lock);
+
+      /* FIXME cannot assume sources are only in the default context */
+      g_main_context_wakeup (main_context);
+
+      /* 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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+gboolean
+gst_bus_have_pending (GstBus * bus)
+{
+  gboolean result;
+
+  g_return_val_if_fail (GST_IS_BUS (bus), FALSE);
+
+  g_mutex_lock (bus->queue_lock);
+  /* see if there is a message on the bus */
+  result = !g_queue_is_empty (bus->queue);
+  g_mutex_unlock (bus->queue_lock);
+
+  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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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: 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
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstMessage *
+gst_bus_timed_pop_filtered (GstBus * bus, GstClockTime timeout,
+    GstMessageType types)
+{
+  GstMessage *message;
+  GTimeVal *timeval, abstimeout;
+  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) {
+    GST_LOG_OBJECT (bus, "have %d messages", g_queue_get_length (bus->queue));
+
+    while ((message = g_queue_pop_head (bus->queue))) {
+      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;
+
+    if (timeout == GST_CLOCK_TIME_NONE) {
+      /* wait forever */
+      timeval = NULL;
+    } else if (first_round) {
+      glong add = timeout / 1000;
+
+      if (add == 0)
+        /* no need to wait */
+        break;
+
+      /* make timeout absolute */
+      g_get_current_time (&abstimeout);
+      g_time_val_add (&abstimeout, add);
+      timeval = &abstimeout;
+      first_round = FALSE;
+      GST_DEBUG_OBJECT (bus, "blocking for message, timeout %ld", add);
+    } else {
+      /* calculated the absolute end time already, no need to do it again */
+      GST_DEBUG_OBJECT (bus, "blocking for message, again");
+      timeval = &abstimeout;    /* fool compiler */
+    }
+    if (!g_cond_timed_wait (bus->priv->queue_cond, bus->queue_lock, timeval)) {
+      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: 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
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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: 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
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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: 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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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: The #GstMessage that is on the bus, or NULL if the bus is empty.
+ *
+ * MT safe.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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 = g_queue_peek_head (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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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)
+{
+  GstBusSource *bsrc = (GstBusSource *) source;
+
+  *timeout = -1;
+  return gst_bus_have_pending (bsrc->bus);
+}
+
+static gboolean
+gst_bus_source_check (GSource * source)
+{
+  GstBusSource *bsrc = (GstBusSource *) source;
+
+  return gst_bus_have_pending (bsrc->bus);
+}
+
+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);
+  g_return_val_if_fail (message != NULL, FALSE);
+
+  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;
+
+  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: A #GSource that can be added to a mainloop.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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));
+  gst_object_ref (bus);
+  source->bus = bus;
+
+  return (GSource *) source;
+}
+
+/**
+ * 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.
+ * This function is used to receive asynchronous messages in the main loop.
+ *
+ * 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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+guint
+gst_bus_add_watch_full (GstBus * bus, gint priority,
+    GstBusFunc func, gpointer user_data, GDestroyNotify notify)
+{
+  guint id;
+  GSource *source;
+
+  g_return_val_if_fail (GST_IS_BUS (bus), 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);
+
+  id = g_source_attach (source, NULL);
+  g_source_unref (source);
+
+  GST_DEBUG_OBJECT (bus, "New source %p", source);
+  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.
+ * This function is used to receive asynchronous messages in the main loop.
+ *
+ * The watch can be removed using g_source_remove() or by returning FALSE
+ * from @func.
+ *
+ * Returns: The event source id.
+ *
+ * MT safe.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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_return_if_fail (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_free (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_free (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.
+ *
+ * Returns: 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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+GstMessage *
+gst_bus_poll (GstBus * bus, GstMessageType events, GstClockTimeDiff timeout)
+{
+  GstBusPollData *poll_data;
+  GstMessage *ret;
+  gulong id;
+
+  poll_data = g_new0 (GstBusPollData, 1);
+  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
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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.
+ * 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.
+ *
+ * MT safe.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+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;
+
+  g_assert (bus->signal_watch_id == 0);
+
+  bus->signal_watch_id =
+      gst_bus_add_watch_full (bus, priority, gst_bus_async_signal_func, NULL,
+      NULL);
+
+done:
+
+  bus->num_signal_watchers++;
+
+  GST_OBJECT_UNLOCK (bus);
+}
+
+/**
+ * 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.
+ * 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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+ 
+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.
+ */
+#ifdef __SYMBIAN32__
+EXPORT_C
+#endif
+
+void
+gst_bus_remove_signal_watch (GstBus * bus)
+{
+  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;
+
+  g_source_remove (bus->signal_watch_id);
+  bus->signal_watch_id = 0;
+
+done:
+  GST_OBJECT_UNLOCK (bus);
+  return;
+
+error:
+  {
+    g_critical ("Bus %s has no signal watches attached", GST_OBJECT_NAME (bus));
+    GST_OBJECT_UNLOCK (bus);
+    return;
+  }
+}