gstreamer/gst/gstbus.h

/* GStreamer
 * Copyright (C) 2004 Wim Taymans <wim@fluendo.com>
 *
 * gstbus.h: Header for 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.
 */

#ifndef __GST_BUS_H__
#define __GST_BUS_H__

typedef struct _GstBus GstBus;
typedef struct _GstBusPrivate GstBusPrivate;
typedef struct _GstBusClass GstBusClass;

#include <gst/gstmessage.h>
#include <gst/gstclock.h>

G_BEGIN_DECLS

/* --- standard type macros --- */
#define GST_TYPE_BUS              (gst_bus_get_type ())
#define GST_BUS(bus)              (G_TYPE_CHECK_INSTANCE_CAST ((bus), GST_TYPE_BUS, GstBus))
#define GST_IS_BUS(bus)           (G_TYPE_CHECK_INSTANCE_TYPE ((bus), GST_TYPE_BUS))
#define GST_BUS_CLASS(bclass)     (G_TYPE_CHECK_CLASS_CAST ((bclass), GST_TYPE_BUS, GstBusClass))
#define GST_IS_BUS_CLASS(bclass)  (G_TYPE_CHECK_CLASS_TYPE ((bclass), GST_TYPE_BUS))
#define GST_BUS_GET_CLASS(bus)    (G_TYPE_INSTANCE_GET_CLASS ((bus), GST_TYPE_BUS, GstBusClass))
#define GST_BUS_CAST(bus)         ((GstBus*)(bus))

/**
 * GstBusFlags:
 * @GST_BUS_FLUSHING: The bus is currently dropping all messages
 * @GST_BUS_FLAG_LAST: offset to define more flags
 *
 * The standard flags that a bus may have.
 */
typedef enum {
  GST_BUS_FLUSHING      = (GST_OBJECT_FLAG_LAST << 0),
  /* padding */
  GST_BUS_FLAG_LAST     = (GST_OBJECT_FLAG_LAST << 1)
} GstBusFlags;

/**
 * GstBusSyncReply:
 * @GST_BUS_DROP: drop the message
 * @GST_BUS_PASS: pass the message to the async queue
 * @GST_BUS_ASYNC: pass message to async queue, continue if message is handled
 *
 * The result values for a GstBusSyncHandler.
 */
typedef enum
{
  GST_BUS_DROP = 0,
  GST_BUS_PASS = 1,
  GST_BUS_ASYNC = 2,
} GstBusSyncReply;

/**
 * GstBusSyncHandler:
 * @bus: the #GstBus that sent the message
 * @message: the #GstMessage
 * @data: user data that has been given, when registering the handler
 *
 * Handler will be invoked synchronously, when a new message has been injected
 * into the bus. This function is mostly used internally. Only one sync handler
 * can be attached to a given bus.
 *
 * If the handler returns GST_BUS_DROP, it should unref the message, else the
 * message should not be unreffed by the sync handler.
 *
 * Returns: #GstBusSyncReply stating what to do with the message
 */
typedef GstBusSyncReply (*GstBusSyncHandler) 	(GstBus * bus, GstMessage * message, gpointer data);

/**
 * GstBusFunc:
 * @bus: the #GstBus that sent the message
 * @message: the #GstMessage
 * @data: user data that has been given, when registering the handler
 *
 * Specifies the type of function passed to gst_bus_add_watch() or
 * gst_bus_add_watch_full(), which is called from the mainloop when a message
 * is available on the bus.
 *
 * The message passed to the function will be unreffed after execution of this
 * function so it should not be freed in the function.
 *
 * Note that this function is used as a GSourceFunc which means that returning
 * FALSE will remove the GSource from the mainloop.
 *
 * Returns: %FALSE if the event source should be removed.
 */
typedef gboolean 	(*GstBusFunc)	 	(GstBus * bus, GstMessage * message, gpointer data);

/**
 * GstBus:
 *
 * The opaque #GstBus data structure.
 */
struct _GstBus
{
  GstObject 	    object;

  /*< private > */
  GQueue           *queue;
  GMutex           *queue_lock;

  GstBusSyncHandler sync_handler;
  gpointer 	    sync_handler_data;

  guint             signal_watch_id;
  guint             num_signal_watchers;

  /*< private > */
  GstBusPrivate    *priv;
  gpointer _gst_reserved[GST_PADDING - 1];
};

struct _GstBusClass
{
  GstObjectClass parent_class;

  /* signals */
  void (*message)  	(GstBus *bus, GstMessage *message);
  void (*sync_message)  (GstBus *bus, GstMessage *message);

  /*< private > */
  gpointer _gst_reserved[GST_PADDING];
};

GType 			gst_bus_get_type 		(void);

GstBus*			gst_bus_new	 		(void);

gboolean 		gst_bus_post 			(GstBus * bus, GstMessage * message);

gboolean 		gst_bus_have_pending 		(GstBus * bus);
GstMessage *		gst_bus_peek 			(GstBus * bus);
GstMessage *		gst_bus_pop 			(GstBus * bus);
void			gst_bus_set_flushing		(GstBus * bus, gboolean flushing);

/* synchronous dispatching */
void 			gst_bus_set_sync_handler 	(GstBus * bus, GstBusSyncHandler func,
    							 gpointer data);
/* GSource based dispatching */
GSource *		gst_bus_create_watch 		(GstBus * bus);
guint 			gst_bus_add_watch_full 		(GstBus * bus,
    							 gint priority,
    							 GstBusFunc func,
							 gpointer user_data,
							 GDestroyNotify notify);
guint 			gst_bus_add_watch 		(GstBus * bus,
    							 GstBusFunc func,
							 gpointer user_data);

/* polling the bus */
GstMessage*		gst_bus_poll			(GstBus *bus, GstMessageType events,
                                                         GstClockTimeDiff timeout);

/* signal based dispatching helper functions. */
gboolean		gst_bus_async_signal_func	(GstBus *bus, GstMessage *message,
							 gpointer data);
GstBusSyncReply		gst_bus_sync_signal_handler	(GstBus *bus, GstMessage *message,
							 gpointer data);

/* convenience api to add/remove a gsource that emits the async signals */
void 			gst_bus_add_signal_watch 	(GstBus * bus);
void 			gst_bus_add_signal_watch_full 	(GstBus * bus, gint priority);
void 			gst_bus_remove_signal_watch 	(GstBus * bus);

void			gst_bus_enable_sync_message_emission (GstBus * bus);
void			gst_bus_disable_sync_message_emission (GstBus * bus);

G_END_DECLS

#endif /* __GST_BUS_H__ */