gstreamer/gst/gstpad.c

/* GStreamer
 * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
 *                    2000 Wim Taymans <wtay@chello.be>
 *
 * gstpad.c: Pads for linking elements together
 *
 * 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.
 */

/* #define GST_DEBUG_ENABLED */
#include "gst_private.h"

#include "gstpad.h"
#include "gstutils.h"
#include "gstelement.h"
#include "gsttype.h"
#include "gstbin.h"
#include "gstscheduler.h"
#include "gstevent.h"
#include "gstlog.h"

enum {
  TEMPL_PAD_CREATED,
  /* FILL ME */
  TEMPL_LAST_SIGNAL
};

static GstObject *padtemplate_parent_class = NULL;
static guint gst_pad_template_signals[TEMPL_LAST_SIGNAL] = { 0 };

GType _gst_pad_type = 0;

/***** Start with the base GstPad class *****/
static void		gst_pad_class_init		(GstPadClass *klass);
static void		gst_pad_init			(GstPad *pad);

static gboolean 	gst_pad_try_relink_filtered_func (GstRealPad *srcpad, GstRealPad *sinkpad, 
							 GstCaps *caps, gboolean clear);

#ifndef GST_DISABLE_LOADSAVE
static xmlNodePtr	gst_pad_save_thyself		(GstObject *object, xmlNodePtr parent);
#endif

static GstObject *pad_parent_class = NULL;

GType
gst_pad_get_type (void) 
{
  if (!_gst_pad_type) {
    static const GTypeInfo pad_info = {
      sizeof (GstPadClass), NULL, NULL,
      (GClassInitFunc) gst_pad_class_init, NULL, NULL,
      sizeof (GstPad), 
      32,
      (GInstanceInitFunc) gst_pad_init, NULL
    };
    _gst_pad_type = g_type_register_static (GST_TYPE_OBJECT, "GstPad", 
	                                    &pad_info, 0);
  }
  return _gst_pad_type;
}

static void
gst_pad_class_init (GstPadClass *klass)
{
  pad_parent_class = g_type_class_ref (GST_TYPE_OBJECT);
}

static void
gst_pad_init (GstPad *pad)
{
  pad->element_private = NULL;

  pad->padtemplate = NULL;
}



/***** Then do the Real Pad *****/
/* Pad signals and args */
enum {
  REAL_CAPS_NEGO_FAILED,
  REAL_LINKED,
  REAL_UNLINKED,
  /* FILL ME */
  REAL_LAST_SIGNAL
};

enum {
  REAL_ARG_0,
  REAL_ARG_CAPS,
  REAL_ARG_ACTIVE,
  /* FILL ME */
};

static void	gst_real_pad_class_init		(GstRealPadClass *klass);
static void	gst_real_pad_init		(GstRealPad *pad);

static void	gst_real_pad_set_property	(GObject *object, guint prop_id,
                                                 const GValue *value, 
						 GParamSpec *pspec);
static void	gst_real_pad_get_property	(GObject *object, guint prop_id,
                                                 GValue *value, 
						 GParamSpec *pspec);

static void	gst_real_pad_dispose		(GObject *object);

GType _gst_real_pad_type = 0;

static GstPad *real_pad_parent_class = NULL;
static guint gst_real_pad_signals[REAL_LAST_SIGNAL] = { 0 };

GType
gst_real_pad_get_type (void) {
  if (!_gst_real_pad_type) {
    static const GTypeInfo pad_info = {
      sizeof (GstRealPadClass), NULL, NULL,
      (GClassInitFunc) gst_real_pad_class_init, NULL, NULL,
      sizeof (GstRealPad),
      32,
      (GInstanceInitFunc) gst_real_pad_init, NULL
    };
    _gst_real_pad_type = g_type_register_static (GST_TYPE_PAD, "GstRealPad", 
	                                         &pad_info, 0);
  }
  return _gst_real_pad_type;
}

static void
gst_real_pad_class_init (GstRealPadClass *klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;

  gobject_class = (GObjectClass*) klass;
  gstobject_class = (GstObjectClass*) klass;

  real_pad_parent_class = g_type_class_ref (GST_TYPE_PAD);

  gobject_class->dispose  = GST_DEBUG_FUNCPTR (gst_real_pad_dispose);
  gobject_class->set_property  = GST_DEBUG_FUNCPTR (gst_real_pad_set_property);
  gobject_class->get_property  = GST_DEBUG_FUNCPTR (gst_real_pad_get_property);

  gst_real_pad_signals[REAL_CAPS_NEGO_FAILED] =
    g_signal_new ("caps_nego_failed", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstRealPadClass, caps_nego_failed), NULL, NULL,
                  gst_marshal_VOID__POINTER, G_TYPE_NONE, 1,
                  G_TYPE_POINTER);
  gst_real_pad_signals[REAL_LINKED] =
    g_signal_new ("linked", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstRealPadClass, linked), NULL, NULL,
                  gst_marshal_VOID__POINTER, G_TYPE_NONE, 1,
                  G_TYPE_POINTER);
  gst_real_pad_signals[REAL_UNLINKED] =
    g_signal_new ("unlinked", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstRealPadClass, unlinked), NULL, NULL,
                  gst_marshal_VOID__POINTER, G_TYPE_NONE, 1,
                  G_TYPE_POINTER);

/*  gtk_object_add_arg_type ("GstRealPad::active", G_TYPE_BOOLEAN, */
/*                           GTK_ARG_READWRITE, REAL_ARG_ACTIVE); */
  g_object_class_install_property (G_OBJECT_CLASS (klass), REAL_ARG_ACTIVE,
    g_param_spec_boolean ("active", "Active", "Whether the pad is active.",
                          TRUE, G_PARAM_READWRITE));
  g_object_class_install_property (G_OBJECT_CLASS (klass), REAL_ARG_CAPS,
    g_param_spec_boxed ("caps", "Caps", "The capabilities of the pad",
                        GST_TYPE_CAPS, G_PARAM_READABLE));

#ifndef GST_DISABLE_LOADSAVE
  gstobject_class->save_thyself = GST_DEBUG_FUNCPTR (gst_pad_save_thyself);
#endif
  gstobject_class->path_string_separator = ".";
}

static void
gst_real_pad_init (GstRealPad *pad)
{
  pad->direction = GST_PAD_UNKNOWN;
  pad->peer = NULL;

  pad->chainfunc = NULL;
  pad->getfunc = NULL;

  pad->chainhandler = NULL;
  pad->gethandler = NULL;

  pad->bufferpoolfunc = NULL;
  pad->ghostpads = NULL;
  pad->caps = NULL;

  pad->linkfunc = NULL;
  pad->getcapsfunc = NULL;

  pad->convertfunc 	= gst_pad_convert_default;
  pad->eventfunc 	= gst_pad_event_default;
  pad->convertfunc 	= gst_pad_convert_default;
  pad->queryfunc 	= gst_pad_query_default;
  pad->intlinkfunc 	= gst_pad_get_internal_links_default;

  pad->eventmaskfunc 	= gst_pad_get_event_masks_default;
  pad->formatsfunc 	= gst_pad_get_formats_default;
  pad->querytypefunc 	= gst_pad_get_query_types_default;

  GST_FLAG_SET (pad, GST_PAD_DISABLED);
  GST_FLAG_UNSET (pad, GST_PAD_NEGOTIATING);
  
  gst_probe_dispatcher_init (&pad->probedisp);
}

static void
gst_real_pad_set_property (GObject *object, guint prop_id, 
                           const GValue *value, GParamSpec *pspec)
{
  g_return_if_fail (GST_IS_PAD (object));

  switch (prop_id) {
    case REAL_ARG_ACTIVE:
      gst_pad_set_active (GST_PAD (object), g_value_get_boolean (value));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}

static void
gst_real_pad_get_property (GObject *object, guint prop_id, 
                           GValue *value, GParamSpec *pspec)
{
  g_return_if_fail (GST_IS_PAD (object));

  switch (prop_id) {
    case REAL_ARG_ACTIVE:
      g_value_set_boolean (value, !GST_FLAG_IS_SET (object, GST_PAD_DISABLED));
      break;
    case REAL_ARG_CAPS:
      g_value_set_boxed (value, GST_PAD_CAPS (GST_REAL_PAD (object)));
      break;
    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
      break;
  }
}


/**
 * gst_pad_custom_new:
 * @type: the #Gtype of the pad.
 * @name: the name of the new pad.
 * @direction: the #GstPadDirection of the pad.
 *
 * Creates a new pad with the given name and type in the given direction.
 * If name is NULL, a guaranteed unique name (across all pads) 
 * will be assigned.
 *
 * Returns: a new #GstPad, or NULL in case of an error.
 */
GstPad*
gst_pad_custom_new (GType type, const gchar *name,
	            GstPadDirection direction)
{
  GstRealPad *pad;

  g_return_val_if_fail (direction != GST_PAD_UNKNOWN, NULL);

  pad = g_object_new (type, NULL);
  gst_object_set_name (GST_OBJECT (pad), name);
  GST_RPAD_DIRECTION (pad) = direction;

  return GST_PAD (pad);
}

/**
 * gst_pad_new:
 * @name: the name of the new pad.
 * @direction: the #GstPadDirection of the pad.
 *
 * Creates a new real pad with the given name in the given direction.
 * If name is NULL, a guaranteed unique name (across all pads) 
 * will be assigned.
 *
 * Returns: a new #GstPad, or NULL in case of an error.
 */
GstPad*
gst_pad_new (const gchar *name,
	     GstPadDirection direction)
{
  return gst_pad_custom_new (gst_real_pad_get_type (), name, direction);
}

/**
 * gst_pad_custom_new_from_template:
 * @type: the custom #GType of the pad.
 * @templ: the #GstPadTemplate to instantiate from.
 * @name: the name of the new pad.
 *
 * Creates a new custom pad with the given name from the given template.
 * If name is NULL, a guaranteed unique name (across all pads) 
 * will be assigned.
 *
 * Returns: a new #GstPad, or NULL in case of an error.
 */
GstPad*
gst_pad_custom_new_from_template (GType type, GstPadTemplate *templ,
		           	  const gchar *name)
{
  GstPad *pad;

  g_return_val_if_fail (templ != NULL, NULL);

  pad = gst_pad_new (name, templ->direction);
  
  gst_object_ref (GST_OBJECT (templ));
  GST_PAD_PAD_TEMPLATE (pad) = templ;

  g_signal_emit (G_OBJECT (templ), gst_pad_template_signals[TEMPL_PAD_CREATED], 0, pad);
  
  return pad;
}

/**
 * gst_pad_new_from_template:
 * @templ: the pad template to use
 * @name: the name of the element
 *
 * Creates a new real pad with the given name from the given template.
 * If name is NULL, a guaranteed unique name (across all pads) 
 * will be assigned.
 *
 * Returns: a new #GstPad, or NULL in case of an error.
 */
GstPad*
gst_pad_new_from_template (GstPadTemplate *templ, const gchar *name)
{
  return gst_pad_custom_new_from_template (gst_real_pad_get_type (), 
                                           templ, name);
}

/**
 * gst_pad_get_direction:
 * @pad: a #GstPad to get the direction of.
 *
 * Gets the direction of the pad.
 *
 * Returns: the #GstPadDirection of the pad.
 */
GstPadDirection
gst_pad_get_direction (GstPad *pad)
{
  g_return_val_if_fail (GST_IS_PAD (pad), GST_PAD_UNKNOWN);

  return GST_PAD_DIRECTION (pad);
}

/**
 * gst_pad_set_active:
 * @pad: the #GstPad to activate or deactivate.
 * @active: TRUE to activate the pad.
 *
 * Activates or deactivates the given pad.
 */
void
gst_pad_set_active (GstPad *pad, gboolean active)
{
  GstRealPad *realpad;
  gboolean old;

  g_return_if_fail (GST_IS_PAD (pad));

  old = GST_PAD_IS_ACTIVE (pad);

  if (old == active)
    return;

  realpad = GST_PAD_REALIZE (pad);

  if (active) {
    GST_DEBUG (GST_CAT_PADS, "activating pad %s:%s", 
	       GST_DEBUG_PAD_NAME (realpad));
    GST_FLAG_UNSET (realpad, GST_PAD_DISABLED);
  } else {
    GST_DEBUG (GST_CAT_PADS, "de-activating pad %s:%s", 
	       GST_DEBUG_PAD_NAME (realpad));
    GST_FLAG_SET (realpad, GST_PAD_DISABLED);
  }
  if (old != active)
    g_object_notify (G_OBJECT (realpad), "active");
}

/**
 * gst_pad_is_active:
 * @pad: the #GstPad to query
 *
 * Query if a pad is active
 *
 * Returns: TRUE if the pad is active.
 */
gboolean
gst_pad_is_active (GstPad *pad)
{
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  return !GST_FLAG_IS_SET (pad, GST_PAD_DISABLED);
}

/**
 * gst_pad_set_name:
 * @pad: a #GstPad to set the name of.
 * @name: the name of the pad.
 *
 * Sets the name of a pad.  If name is NULL, then a guaranteed unique
 * name will be assigned.
 */
void
gst_pad_set_name (GstPad *pad, const gchar *name)
{
  g_return_if_fail (GST_IS_PAD (pad));

  gst_object_set_name (GST_OBJECT (pad), name);
}

/**
 * gst_pad_get_name:
 * @pad: a #GstPad to get the name of.
 *
 * Gets the name of a pad.
 *
 * Returns: the name of the pad.  This is not a newly allocated pointer
 * so you must not free it.
 */
const gchar*
gst_pad_get_name (GstPad *pad)
{
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  return GST_OBJECT_NAME (pad);
}

/**
 * gst_pad_set_chain_function:
 * @pad: a #GstPad to set the chain function for.
 * @chain: the #GstPadChainFunction to set.
 *
 * Sets the given chain function for the pad.
 */
void 
gst_pad_set_chain_function (GstPad *pad, GstPadChainFunction chain)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_CHAINFUNC (pad) = chain;
  GST_DEBUG (GST_CAT_PADS, "chainfunc for %s:%s set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (chain));
}

/**
 * gst_pad_set_get_function:
 * @pad: a #GstPad to set the get function for.
 * @get: the #GstPadGetFunction to set.
 *
 * Sets the given get function for the pad.
 */
void
gst_pad_set_get_function (GstPad *pad,
			  GstPadGetFunction get)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_GETFUNC (pad) = get;
  
  GST_DEBUG (GST_CAT_PADS, "getfunc for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (get));
}

/**
 * gst_pad_set_event_function:
 * @pad: a #GstPad to set the event handler for.
 * @event: the #GstPadEventFunction to set.
 *
 * Sets the given event handler for the pad.
 */
void
gst_pad_set_event_function (GstPad *pad,
                            GstPadEventFunction event)
{
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_EVENTFUNC (pad) = event;

  GST_DEBUG (GST_CAT_PADS, "eventfunc for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (event));
}

/**
 * gst_pad_set_event_mask_function:
 * @pad: a #GstPad to set the event mask function for.
 * @mask_func: the #GstPadEventMaskFunction to set.
 *
 * Sets the given event mask function for the pad.
 */
void
gst_pad_set_event_mask_function (GstPad *pad, 
                                 GstPadEventMaskFunction mask_func)
{
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_EVENTMASKFUNC (pad) = mask_func;

  GST_DEBUG (GST_CAT_PADS, "eventmaskfunc for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (mask_func));
}

/**
 * gst_pad_get_event_masks:
 * @pad: a #GstPad to get the event mask for.
 *
 * Gets the array of eventmasks from the given pad.
 *
 * Returns: an array with eventmasks, the list is ended 
 * with 0
 */
const GstEventMask*
gst_pad_get_event_masks (GstPad *pad)
{
  GstRealPad *rpad;
  
  if (pad == NULL)
    return FALSE;

  rpad = GST_PAD_REALIZE (pad);

  g_return_val_if_fail (rpad, FALSE);

  if (GST_RPAD_EVENTMASKFUNC (rpad))
    return GST_RPAD_EVENTMASKFUNC (rpad) (GST_PAD_CAST (pad));

  return NULL;
}

static gboolean
gst_pad_get_event_masks_dispatcher (GstPad *pad, const GstEventMask **data)
{
  *data = gst_pad_get_event_masks (pad);

  return TRUE;
}

/**
 * gst_pad_get_event_masks_default:
 * @pad: a #GstPad to get the event mask for.
 *
 * Invokes the default event masks dispatcher on the pad.
 *
 * Returns: an array with eventmasks, the list is ended 
 * with 0
 */
const GstEventMask* 
gst_pad_get_event_masks_default (GstPad *pad)
{
  GstEventMask *result = NULL;

  gst_pad_dispatcher (pad, (GstPadDispatcherFunction) 
                           gst_pad_get_event_masks_dispatcher, &result);

  return result;
}

/**
 * gst_pad_set_convert_function:
 * @pad: a #GstPad to set the convert function for.
 * @convert: the #GstPadConvertFunction to set.
 *
 * Sets the given convert function for the pad.
 */
void
gst_pad_set_convert_function (GstPad *pad,
                              GstPadConvertFunction convert)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_CONVERTFUNC (pad) = convert;

  GST_DEBUG (GST_CAT_PADS, "convertfunc for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (convert));
}

/**
 * gst_pad_set_query_function:
 * @pad: the #GstPad to set the query function for.
 * @query: the #GstPadQueryFunction to set.
 *
 * Set the given query function for the pad.
 */
void
gst_pad_set_query_function (GstPad *pad, GstPadQueryFunction query)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_QUERYFUNC (pad) = query;

  GST_DEBUG (GST_CAT_PADS, "queryfunc for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (query));
}

/**
 * gst_pad_set_query_type_function:
 * @pad: the #GstPad to set the query type function for.
 * @type_func: the #GstPadQueryTypeFunction to set.
 *
 * Set the given query type function for the pad.
 */
void
gst_pad_set_query_type_function (GstPad *pad, GstPadQueryTypeFunction type_func)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_QUERYTYPEFUNC (pad) = type_func;

  GST_DEBUG (GST_CAT_PADS, "querytypefunc for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (type_func));
}

/**
 * gst_pad_get_query_types:
 * @pad: the #GstPad to query
 *
 * Get an array of supported queries that can be performed
 * on this pad.
 *
 * Returns: an array of querytypes anded with 0.
 */
const GstQueryType*
gst_pad_get_query_types (GstPad *pad)
{
  GstRealPad *rpad;
  
  if (pad == NULL)
    return FALSE;

  rpad = GST_PAD_REALIZE (pad);

  g_return_val_if_fail (rpad, FALSE);

  if (GST_RPAD_QUERYTYPEFUNC (rpad))
    return GST_RPAD_QUERYTYPEFUNC (rpad) (GST_PAD_CAST (pad));

  return NULL;
}

static gboolean
gst_pad_get_query_types_dispatcher (GstPad *pad, const GstQueryType **data)
{
  *data = gst_pad_get_query_types (pad);

  return TRUE;
}

/**
 * gst_pad_get_query_types_default:
 * @pad: the #GstPad to query
 *
 * Invoke the default dispatcher for the query types on
 * the pad.
 *
 * Returns: an array of querytypes anded with 0.
 */
const GstQueryType*
gst_pad_get_query_types_default (GstPad *pad)
{
  GstQueryType *result = NULL;

  gst_pad_dispatcher (pad, (GstPadDispatcherFunction) 
                           gst_pad_get_query_types_dispatcher, &result);

  return result;
}

/**
 * gst_pad_set_internal_link_function:
 * @pad: a #GstPad to set the internal link function for.
 * @intlink: the #GstPadIntLinkFunction to set.
 *
 * Sets the given internal link function for the pad.
 */
void
gst_pad_set_internal_link_function (GstPad *pad, 
                                          GstPadIntLinkFunction intlink)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_INTLINKFUNC (pad) = intlink;
  GST_DEBUG (GST_CAT_PADS, "internal link for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (intlink));
}

/**
 * gst_pad_set_formats_function:
 * @pad: the #GstPad to set the formats function for.
 * @formats: the #GstPadFormatsFunction to set.
 *
 * Sets the given formats function for the pad.
 */
void
gst_pad_set_formats_function (GstPad *pad, GstPadFormatsFunction formats)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_FORMATSFUNC (pad) = formats;
  GST_DEBUG (GST_CAT_PADS, "formats function for %s:%s  set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (formats));
}

/**
 * gst_pad_set_link_function:
 * @pad: a #GstPad to set the link function for.
 * @link: the #GstPadLinkFunction to set.
 *
 * Sets the given link function for the pad. It will be called
 * when the pad is linked or relinked with caps.
 */
void
gst_pad_set_link_function (GstPad *pad,
		              GstPadLinkFunction link)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_LINKFUNC (pad) = link;
  GST_DEBUG (GST_CAT_PADS, "linkfunc for %s:%s set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (link));
}

/**
 * gst_pad_set_getcaps_function:
 * @pad: a #GstPad to set the getcaps function for.
 * @getcaps: the #GstPadGetCapsFunction to set.
 *
 * Sets the given getcaps function for the pad.
 */
void
gst_pad_set_getcaps_function (GstPad *pad,
		              GstPadGetCapsFunction getcaps)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));

  GST_RPAD_GETCAPSFUNC (pad) = getcaps;
  GST_DEBUG (GST_CAT_PADS, "getcapsfunc for %s:%s set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (getcaps));
}
/**
 * gst_pad_set_bufferpool_function:
 * @pad: a #GstPad to set the bufferpool function for.
 * @bufpool: the #GstPadBufferPoolFunction to set.
 *
 * Sets the given bufferpool function for the pad. Note that the
 * bufferpool function can only be set on sinkpads.
 */
void
gst_pad_set_bufferpool_function (GstPad *pad,
		                 GstPadBufferPoolFunction bufpool)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_REAL_PAD (pad));
  g_return_if_fail (GST_PAD_IS_SINK (pad));

  GST_RPAD_BUFFERPOOLFUNC (pad) = bufpool;
  GST_DEBUG (GST_CAT_PADS, "bufferpoolfunc for %s:%s set to %s",
             GST_DEBUG_PAD_NAME (pad), GST_DEBUG_FUNCPTR_NAME (bufpool));
}

/**
 * gst_pad_unlink:
 * @srcpad: the source #GstPad to unlink.
 * @sinkpad: the sink #GstPad to unlink.
 *
 * Unlinks the source pad from the sink pad.
 */
void
gst_pad_unlink (GstPad *srcpad,
		    GstPad *sinkpad)
{
  GstRealPad *realsrc, *realsink;
  GstScheduler *src_sched, *sink_sched;

  /* generic checks */
  g_return_if_fail (srcpad != NULL);
  g_return_if_fail (GST_IS_PAD (srcpad));
  g_return_if_fail (sinkpad != NULL);
  g_return_if_fail (GST_IS_PAD (sinkpad));

  GST_INFO (GST_CAT_ELEMENT_PADS, "unlinking %s:%s(%p) and %s:%s(%p)",
            GST_DEBUG_PAD_NAME (srcpad), srcpad, 
	    GST_DEBUG_PAD_NAME (sinkpad), sinkpad);

  /* now we need to deal with the real/ghost stuff */
  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  g_return_if_fail (GST_RPAD_PEER (realsrc) != NULL);
  g_return_if_fail (GST_RPAD_PEER (realsink) == realsrc);

  if ((GST_RPAD_DIRECTION (realsrc) == GST_PAD_SINK) &&
      (GST_RPAD_DIRECTION (realsink) == GST_PAD_SRC)) {
    GstRealPad *temppad;

    temppad = realsrc;
    realsrc = realsink;
    realsink = temppad;
  }
  g_return_if_fail ((GST_RPAD_DIRECTION (realsrc) == GST_PAD_SRC) &&
                    (GST_RPAD_DIRECTION (realsink) == GST_PAD_SINK));

  /* get the schedulers before we unlink */
  src_sched = gst_pad_get_scheduler (GST_PAD_CAST (realsrc));
  sink_sched = gst_pad_get_scheduler (GST_PAD_CAST (realsink));

  /* first clear peers */
  GST_RPAD_PEER (realsrc) = NULL;
  GST_RPAD_PEER (realsink) = NULL;

  /* reset the filters, both filters are refcounted once */
  if (GST_RPAD_FILTER (realsrc)) {
    gst_caps_replace (&GST_RPAD_FILTER (realsink), NULL);
    gst_caps_replace (&GST_RPAD_FILTER (realsrc), NULL);
  }

  /* now tell the scheduler */
  if (src_sched && src_sched == sink_sched) {
    gst_scheduler_pad_unlink (src_sched, 
	                      GST_PAD_CAST (realsrc), 
			      GST_PAD_CAST (realsink));
  }

  /* hold a reference, as they can go away in the signal handlers */
  gst_object_ref (GST_OBJECT (realsrc));
  gst_object_ref (GST_OBJECT (realsink));

  /* fire off a signal to each of the pads telling them 
   * that they've been unlinked */
  g_signal_emit (G_OBJECT (realsrc), gst_real_pad_signals[REAL_UNLINKED], 
                 0, realsink);
  g_signal_emit (G_OBJECT (realsink), gst_real_pad_signals[REAL_UNLINKED], 
                 0, realsrc);

  GST_INFO (GST_CAT_ELEMENT_PADS, "unlinked %s:%s and %s:%s",
            GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  gst_object_unref (GST_OBJECT (realsrc));
  gst_object_unref (GST_OBJECT (realsink));
}

static gboolean
gst_pad_check_schedulers (GstRealPad *realsrc, GstRealPad *realsink)
{
  GstScheduler *src_sched, *sink_sched;
  gint num_decoupled = 0;

  src_sched = gst_pad_get_scheduler (GST_PAD_CAST (realsrc));
  sink_sched = gst_pad_get_scheduler (GST_PAD_CAST (realsink));

  if (src_sched && sink_sched) {
    if (GST_FLAG_IS_SET (GST_PAD_PARENT (realsrc), GST_ELEMENT_DECOUPLED))
      num_decoupled++;
    if (GST_FLAG_IS_SET (GST_PAD_PARENT (realsink), GST_ELEMENT_DECOUPLED))
      num_decoupled++;

    if (src_sched != sink_sched && num_decoupled != 1) {
      return FALSE;
    }
  }
  return TRUE;
}

/**
 * gst_pad_can_link_filtered:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 * @filtercaps: the filter #GstCaps.
 *
 * Checks if the source pad and the sink pad can be linked when constrained
 * by the given filter caps.
 *
 * Returns: TRUE if the pads can be linked, FALSE otherwise.
 */
gboolean
gst_pad_can_link_filtered (GstPad *srcpad, GstPad *sinkpad,
                           GstCaps *filtercaps)
{
  GstRealPad *realsrc, *realsink;

  /* generic checks */
  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (srcpad), FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), FALSE);

  /* now we need to deal with the real/ghost stuff */
  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  g_return_val_if_fail (GST_RPAD_PEER (realsrc) == NULL, FALSE);
  g_return_val_if_fail (GST_RPAD_PEER (realsink) == NULL, FALSE);
  g_return_val_if_fail (GST_PAD_PARENT (realsrc) != NULL, FALSE);
  g_return_val_if_fail (GST_PAD_PARENT (realsink) != NULL, FALSE);

  if (!gst_pad_check_schedulers (realsrc, realsink)) {
    g_warning ("linking pads with different scheds requires "
               "exactly one decoupled element (queue)");
    return FALSE;
  }

  /* check if the directions are compatible */
  if (!(((GST_RPAD_DIRECTION (realsrc) == GST_PAD_SINK) &&
         (GST_RPAD_DIRECTION (realsink) == GST_PAD_SRC)) ||
        ((GST_RPAD_DIRECTION (realsrc) == GST_PAD_SRC) &&
         (GST_RPAD_DIRECTION (realsink) == GST_PAD_SINK))))
    return FALSE;

  return TRUE;
}
/**
 * gst_pad_can_link:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 *
 * Checks if the source pad and the sink pad can be link.
 *
 * Returns: TRUE if the pads can be linked, FALSE otherwise.
 */
gboolean
gst_pad_can_link (GstPad *srcpad, GstPad *sinkpad)
{
  return gst_pad_can_link_filtered (srcpad, sinkpad, NULL);
}

/**
 * gst_pad_link_filtered:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 * @filtercaps: the filter #GstCaps.
 *
 * Links the source pad and the sink pad, constrained
 * by the given filter caps.
 *
 * Returns: TRUE if the pads have been linked, FALSE otherwise.
 */
gboolean
gst_pad_link_filtered (GstPad *srcpad, GstPad *sinkpad, GstCaps *filtercaps)
{
  GstRealPad *realsrc, *realsink;
  GstScheduler *src_sched, *sink_sched;

  /* generic checks */
  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (srcpad), FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), FALSE);

  GST_INFO (GST_CAT_PADS, "trying to link %s:%s and %s:%s",
            GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  /* now we need to deal with the real/ghost stuff */
  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  if ((GST_PAD (realsrc) != srcpad) || (GST_PAD (realsink) != sinkpad)) {
    GST_INFO (GST_CAT_PADS, "*actually* linking %s:%s and %s:%s",
              GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));
  }
  if (GST_RPAD_PEER (realsrc) != NULL) {
    GST_INFO (GST_CAT_PADS, "Real source pad %s:%s has a peer, failed",
	      GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }
  if (GST_RPAD_PEER (realsink) != NULL) {
    GST_INFO (GST_CAT_PADS, "Real sink pad %s:%s has a peer, failed",
	      GST_DEBUG_PAD_NAME (realsink));
    return FALSE;
  }
  if (GST_PAD_PARENT (realsrc) == NULL) {
    GST_INFO (GST_CAT_PADS, "Real src pad %s:%s has no parent, failed",
	      GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }
  if (GST_PAD_PARENT (realsink) == NULL) {
    GST_INFO (GST_CAT_PADS, "Real src pad %s:%s has no parent, failed",
	      GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }

  if (!gst_pad_check_schedulers (realsrc, realsink)) {
    g_warning ("linking pads with different scheds requires "
               "exactly one decoupled element (such as queue)");
    return FALSE;
  }
  
  /* check for reversed directions and swap if necessary */
  if ((GST_RPAD_DIRECTION (realsrc) == GST_PAD_SINK) &&
      (GST_RPAD_DIRECTION (realsink) == GST_PAD_SRC)) {
    GstRealPad *temppad;

    temppad = realsrc;
    realsrc = realsink;
    realsink = temppad;
  }
  if (GST_RPAD_DIRECTION (realsrc) != GST_PAD_SRC) {
    GST_INFO (GST_CAT_PADS, "Real src pad %s:%s is not a source pad, failed",
	      GST_DEBUG_PAD_NAME (realsrc));
    return FALSE;
  }    
  if (GST_RPAD_DIRECTION (realsink) != GST_PAD_SINK) {
    GST_INFO (GST_CAT_PADS, "Real sink pad %s:%s is not a sink pad, failed",
	      GST_DEBUG_PAD_NAME (realsink));
    return FALSE;
  }    
  /* first set peers */
  GST_RPAD_PEER (realsrc) = realsink;
  GST_RPAD_PEER (realsink) = realsrc;

  /* try to negotiate the pads, we don't need to clear the caps here */
  if (!gst_pad_try_relink_filtered_func (realsrc, realsink,
	                                 filtercaps, FALSE)) {
    GST_DEBUG (GST_CAT_CAPS, "relink_filtered_func failed, can't link");

    GST_RPAD_PEER (realsrc) = NULL;
    GST_RPAD_PEER (realsink) = NULL;

    return FALSE;
  }

  /* fire off a signal to each of the pads telling them 
   * that they've been linked */
  g_signal_emit (G_OBJECT (realsrc), gst_real_pad_signals[REAL_LINKED], 
                 0, realsink);
  g_signal_emit (G_OBJECT (realsink), gst_real_pad_signals[REAL_LINKED], 
                 0, realsrc);

  src_sched = gst_pad_get_scheduler (GST_PAD_CAST (realsrc));
  sink_sched = gst_pad_get_scheduler (GST_PAD_CAST (realsink));

  /* now tell the scheduler */
  if (src_sched && src_sched == sink_sched) {
    gst_scheduler_pad_link (src_sched, 
	                    GST_PAD_CAST (realsrc), GST_PAD_CAST (realsink));
  }

  GST_INFO (GST_CAT_PADS, "linked %s:%s and %s:%s, successful",
            GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad));

  return TRUE;
}

/**
 * gst_pad_link:
 * @srcpad: the source #GstPad to link.
 * @sinkpad: the sink #GstPad to link.
 *
 * Links the source pad to the sink pad.
 *
 * Returns: TRUE if the pad could be linked, FALSE otherwise.
 */
gboolean
gst_pad_link (GstPad *srcpad, GstPad *sinkpad)
{
  return gst_pad_link_filtered (srcpad, sinkpad, NULL);
}

/**
 * gst_pad_set_parent:
 * @pad: a #GstPad to set the parent of.
 * @parent: the new parent #GstElement.
 *
 * Sets the parent object of a pad.
 */
void
gst_pad_set_parent (GstPad *pad, GstElement *parent)
{
  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (GST_PAD_PARENT (pad) == NULL);
  g_return_if_fail (parent != NULL);
  g_return_if_fail (GST_IS_OBJECT (parent));
  g_return_if_fail ((gpointer) pad != (gpointer) parent);

  gst_object_set_parent (GST_OBJECT (pad), GST_OBJECT (parent));
}

/**
 * gst_pad_get_parent:
 * @pad: the #GstPad to get the parent of.
 *
 * Gets the parent object of this pad.
 *
 * Returns: the parent #GstElement.
 */
GstElement*
gst_pad_get_parent (GstPad *pad)
{
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  return GST_PAD_PARENT (pad);
}

/**
 * gst_pad_get_pad_template:
 * @pad: a #GstPad to get the pad template of.
 *
 * Gets the pad template object of this pad.
 *
 * Returns: the #GstPadTemplate from which this pad was instantiated.
 */
GstPadTemplate*
gst_pad_get_pad_template (GstPad *pad)
{
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  return GST_PAD_PAD_TEMPLATE (pad); 
}


/**
 * gst_pad_get_scheduler:
 * @pad: a #GstPad to get the scheduler of.
 *
 * Gets the scheduler of the pad. Since the pad does not
 * have a scheduler of its own, the scheduler of the parent
 * is taken. For decoupled pads, the scheduler of the peer
 * parent is taken.
 *
 * Returns: the #GstScheduler of the pad.
 */
GstScheduler*
gst_pad_get_scheduler (GstPad *pad)
{
  GstScheduler *scheduler = NULL;
  GstElement *parent;
  
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  
  parent = gst_pad_get_parent (pad);
  if (parent) {
    if (GST_FLAG_IS_SET (parent, GST_ELEMENT_DECOUPLED)) {
      GstRealPad *peer = GST_RPAD_PEER (pad);

      if (peer) {
        scheduler = gst_element_get_scheduler (gst_pad_get_parent (GST_PAD_CAST (peer)));
      }
    }
    else {
      scheduler = gst_element_get_scheduler (parent);
    }
  }
 
  return scheduler;
}

/**
 * gst_pad_get_real_parent:
 * @pad: a #GstPad to get the real parent of.
 *
 * Gets the real parent object of this pad. If the pad
 * is a ghost pad, the actual owner of the real pad is
 * returned, as opposed to #gst_pad_get_parent().
 *
 * Returns: the parent #GstElement.
 */
GstElement*
gst_pad_get_real_parent (GstPad *pad)
{
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  return GST_PAD_PARENT (GST_PAD (GST_PAD_REALIZE (pad)));
}

/**
 * gst_pad_add_ghost_pad:
 * @pad: a #GstPad to attach the ghost pad to.
 * @ghostpad: the ghost #GstPad to to the pad.
 *
 * Adds a ghost pad to a pad.
 */
void
gst_pad_add_ghost_pad (GstPad *pad,
		       GstPad *ghostpad)
{
  GstRealPad *realpad;

  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (ghostpad != NULL);
  g_return_if_fail (GST_IS_GHOST_PAD (ghostpad));

  realpad = GST_PAD_REALIZE (pad);

  realpad->ghostpads = g_list_prepend (realpad->ghostpads, ghostpad);
}


/**
 * gst_pad_remove_ghost_pad:
 * @pad: a #GstPad to remove the ghost pad from.
 * @ghostpad: the ghost #GstPad to remove from the pad.
 *
 * Removes a ghost pad from a pad.
 */
void
gst_pad_remove_ghost_pad (GstPad *pad,
		          GstPad *ghostpad)
{
  GstRealPad *realpad;

  g_return_if_fail (pad != NULL);
  g_return_if_fail (GST_IS_PAD (pad));
  g_return_if_fail (ghostpad != NULL);
  g_return_if_fail (GST_IS_GHOST_PAD (ghostpad));

  realpad = GST_PAD_REALIZE (pad);

  realpad->ghostpads = g_list_remove (realpad->ghostpads, ghostpad);
}

/**
 * gst_pad_get_ghost_pad_list:
 * @pad: a #GstPad to get the ghost pads of.
 *
 * Gets the ghost pads of this pad.
 *
 * Returns: a #GList of ghost pads.
 */
GList*
gst_pad_get_ghost_pad_list (GstPad *pad)
{
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  return GST_PAD_REALIZE(pad)->ghostpads;
}

/* an internal caps negotiation helper function:
 * 
 * 1. optionally calls the pad link function with the provided caps
 * 2. deals with the result code of the link function
 * 3. sets fixed caps on the pad.
 */
static GstPadLinkReturn
gst_pad_try_set_caps_func (GstRealPad *pad, GstCaps *caps, gboolean notify)
{
  GstCaps *allowed = NULL;
  GstPadTemplate *template;
  GstElement *parent = GST_PAD_PARENT (pad);

  g_return_val_if_fail (pad != NULL, GST_PAD_LINK_REFUSED);
  g_return_val_if_fail (GST_IS_PAD (pad), GST_PAD_LINK_REFUSED);

  /* if this pad has a parent and the parent is not READY, delay the
   * negotiation */
  if (parent && GST_STATE (parent) < GST_STATE_READY)
  {
    GST_DEBUG (GST_CAT_CAPS, "parent %s of pad %s:%s is not READY",
	       GST_ELEMENT_NAME (parent), GST_DEBUG_PAD_NAME (pad));
    return GST_PAD_LINK_DELAYED;
  }
	  
  GST_INFO (GST_CAT_CAPS, "trying to set caps %p on pad %s:%s",
            caps, GST_DEBUG_PAD_NAME (pad));

  /* first see if we have to check against a filter, we ref the caps here as we're
   * going to unref it later on */
  if (!(allowed = gst_caps_ref (GST_RPAD_FILTER (pad)))) {
    /* no filter, make sure we check against the padtemplate then */
    if ((template = gst_pad_get_pad_template (GST_PAD_CAST (pad)))) {
      allowed = gst_pad_template_get_caps (template);
    }
  }
  
  /* do we have to check the caps against something? */
  if (allowed) {
    GstCaps *intersection;

    /* check against calculated caps */
    intersection = gst_caps_intersect (caps, allowed);

    /* oops, empty intersection, caps don"t have anything in common */
    if (!intersection) {
      GST_INFO (GST_CAT_CAPS, "caps did not intersect with %s:%s's allowed caps",
                GST_DEBUG_PAD_NAME (pad));
      gst_caps_debug (caps, "caps themselves (attemped to set)");
      gst_caps_debug (allowed,
                      "allowed caps that did not agree with caps");
      gst_caps_unref (allowed);
      return GST_PAD_LINK_REFUSED;
    }
    /* caps checks out fine, we can unref the intersection now */
    gst_caps_unref (intersection);
    gst_caps_unref (allowed);
    /* given that the caps are fixed, we know that their intersection with the
     * padtemplate caps is the same as caps itself */
  }

  /* we need to notify the link function */
  if (notify && GST_RPAD_LINKFUNC (pad)) {
    GstPadLinkReturn res;
    gchar *debug_string;
    gboolean negotiating;

    GST_INFO (GST_CAT_CAPS, "calling link function on pad %s:%s",
            GST_DEBUG_PAD_NAME (pad));

    negotiating = GST_FLAG_IS_SET (pad, GST_PAD_NEGOTIATING);

    /* set the NEGOTIATING flag if not already done */
    if (!negotiating)
      GST_FLAG_SET (pad, GST_PAD_NEGOTIATING);
    
    /* call the link function */
    res = GST_RPAD_LINKFUNC (pad) (GST_PAD (pad), caps);

    /* unset again after negotiating only if we set it  */
    if (!negotiating)
      GST_FLAG_UNSET (pad, GST_PAD_NEGOTIATING);

    switch (res) {
      case GST_PAD_LINK_REFUSED:
	debug_string = "REFUSED";
	break;
      case GST_PAD_LINK_OK:
	debug_string = "OK";
	break;
      case GST_PAD_LINK_DONE:
	debug_string = "DONE";
	break;
      case GST_PAD_LINK_DELAYED:
	debug_string = "DELAYED";
	break;
      default:
	g_warning ("unknown return code from link function of pad %s:%s %d",
                   GST_DEBUG_PAD_NAME (pad), res);
        return GST_PAD_LINK_REFUSED;
    }

    GST_INFO (GST_CAT_CAPS, 
	      "got reply %s (%d) from link function on pad %s:%s",
              debug_string, res, GST_DEBUG_PAD_NAME (pad));

    /* done means the link function called another caps negotiate function
     * on this pad that succeeded, we dont need to continue */
    if (res == GST_PAD_LINK_DONE) {
      GST_INFO (GST_CAT_CAPS, "pad %s:%s is done", GST_DEBUG_PAD_NAME (pad));
      return GST_PAD_LINK_DONE;
    }
    if (res == GST_PAD_LINK_REFUSED) {
      GST_INFO (GST_CAT_CAPS, "pad %s:%s doesn't accept caps",
		GST_DEBUG_PAD_NAME (pad));
      return GST_PAD_LINK_REFUSED;
    }
  }
  /* we can only set caps on the pad if they are fixed */
  if (GST_CAPS_IS_FIXED (caps)) {

    GST_INFO (GST_CAT_CAPS, "setting caps on pad %s:%s",
              GST_DEBUG_PAD_NAME (pad));
    /* if we got this far all is ok, remove the old caps, set the new one */
    gst_caps_replace_sink (&GST_PAD_CAPS (pad), caps);

    g_object_notify (G_OBJECT (pad), "caps");
  }
  else {
    GST_INFO (GST_CAT_CAPS, 
	      "caps are not fixed on pad %s:%s, not setting them yet",
              GST_DEBUG_PAD_NAME (pad));

    return GST_PAD_LINK_DELAYED;
  }
  return GST_PAD_LINK_OK;
}

/**
 * gst_pad_try_set_caps:
 * @pad: a #GstPad to try to set the caps on.
 * @caps: the #GstCaps to set.
 *
 * Tries to set the caps on the given pad. Ownership is always taken 
 * of the caps, so you will need to unref non-floating caps.
 *
 * Returns: A #GstPadLinkReturn value indicating whether the caps
 * 		could be set.
 */
GstPadLinkReturn
gst_pad_try_set_caps (GstPad *pad, GstCaps *caps)
{
  GstRealPad *peer, *realpad;
  GstPadLinkReturn set_retval;

  realpad = GST_PAD_REALIZE (pad);
  peer = GST_RPAD_PEER (realpad);

  GST_INFO (GST_CAT_CAPS, "trying to set caps %p on pad %s:%s",
            caps, GST_DEBUG_PAD_NAME (realpad));

  gst_caps_debug (caps, "caps that we are trying to set");

  /* try to take ownership */
  gst_caps_ref (caps);
  gst_caps_sink (caps);

  /* setting non fixed caps on a pad is not allowed */
  if (!GST_CAPS_IS_FIXED (caps)) {
    GST_INFO (GST_CAT_CAPS, 
              "trying to set unfixed caps on pad %s:%s, not allowed",
	      GST_DEBUG_PAD_NAME (realpad));
    g_warning ("trying to set non fixed caps on pad %s:%s, not allowed",
               GST_DEBUG_PAD_NAME (realpad));

    gst_caps_debug (caps, "unfixed caps");
    set_retval = GST_PAD_LINK_DELAYED;
    goto done;
  }

  /* if we have a peer try to set the caps, notifying the peerpad
   * if it has a link function */
  if (peer && ((set_retval = gst_pad_try_set_caps_func (peer, caps, TRUE)) <= 0))
  {
    GST_INFO (GST_CAT_CAPS, "tried to set caps on peerpad %s:%s but couldn't, return value %d",
	      GST_DEBUG_PAD_NAME (peer), set_retval);
    goto done;
  }

  /* then try to set our own caps, we don't need to be notified */
  if ((set_retval = gst_pad_try_set_caps_func (realpad, caps, FALSE)) <= 0)
  {
    GST_INFO (GST_CAT_CAPS, "tried to set own caps on pad %s:%s but couldn't, return value %d",
	      GST_DEBUG_PAD_NAME (realpad), set_retval);
    goto done;
  }
  GST_INFO (GST_CAT_CAPS, "succeeded setting caps %p on pad %s:%s, return value %d",
	    caps, GST_DEBUG_PAD_NAME (realpad), set_retval);
  g_assert (GST_PAD_CAPS (pad));

done:			  
  /* if we took ownership, the caps will be freed */
  gst_caps_unref (caps);

  return set_retval;
}

/* this is a caps negotiation convenience routine, it:
 *
 * 1. optionally clears any pad caps.
 * 2. calculates the intersection between the two pad tamplate/getcaps caps.
 * 3. calculates the intersection with the (optional) filtercaps.
 * 4. stores the intersection in the pad filter.
 * 5. stores the app filtercaps in the pad appfilter.
 * 6. starts the caps negotiation.
 */
static gboolean
gst_pad_try_relink_filtered_func (GstRealPad *srcpad, GstRealPad *sinkpad, 
                                  GstCaps *filtercaps, gboolean clear)
{
  GstCaps *srccaps, *sinkcaps;
  GstCaps *intersection = NULL;
  GstRealPad *realsrc, *realsink;

  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  g_return_val_if_fail (GST_RPAD_PEER (realsrc) != NULL, FALSE);
  g_return_val_if_fail (GST_RPAD_PEER (realsink) == realsrc, FALSE);

  /* optinally clear the caps */
  if (clear) {
    GST_INFO (GST_CAT_PADS, 
	      "start relink filtered %s:%s and %s:%s, clearing caps",
              GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));

    /* FIXME does this leak? */
    gst_caps_replace (&GST_PAD_CAPS (GST_PAD (realsrc)), NULL);
    gst_caps_replace (&GST_PAD_CAPS (GST_PAD (realsink)), NULL);
    gst_caps_replace (&GST_RPAD_FILTER (realsrc), NULL); 
    gst_caps_replace (&GST_RPAD_FILTER (realsink), NULL); 
  }
  else {
    GST_INFO (GST_CAT_PADS, "start relink filtered %s:%s and %s:%s",
        GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));
  }

  srccaps = gst_pad_get_caps (GST_PAD (realsrc));
  GST_DEBUG (GST_CAT_PADS, "dumping caps of pad %s:%s", 
             GST_DEBUG_PAD_NAME (realsrc));
  gst_caps_debug (srccaps, "caps of src pad (pre-relink)");
  sinkcaps = gst_pad_get_caps (GST_PAD (realsink));
  GST_DEBUG (GST_CAT_PADS, "dumping caps of pad %s:%s", 
             GST_DEBUG_PAD_NAME (realsink));
  gst_caps_debug (sinkcaps, "caps of sink pad (pre-relink)");

  /* first take the intersection of the pad caps */
  intersection = gst_caps_intersect (srccaps, sinkcaps);
  gst_caps_debug (intersection, "caps of intersection");

  /* if we have no intersection but one of the caps was not NULL.. */
  if (!intersection && (srccaps || sinkcaps)) {
    /* the intersection is NULL but the pad caps were not both NULL,
     * this means they have no common format */
    GST_INFO (GST_CAT_PADS, "pads %s:%s and %s:%s have no common type",
              GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));
    /* make sure any floating caps from gst_pad_get_caps are freed here */
    gst_caps_sink (srccaps);
    gst_caps_sink (sinkcaps);
    return FALSE;
  } else  {
    GST_INFO (GST_CAT_PADS, "pads %s:%s and %s:%s intersected to %s caps",
       GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink), 
       (intersection ?
	   (GST_CAPS_IS_FIXED (intersection) ? "fixed" : "variable") :
	   "NULL"));

    /* we don't need those anymore, as the caps can be floating */
    gst_caps_sink (srccaps);
    gst_caps_sink (sinkcaps);

    /* then filter this against the app filter */
    if (filtercaps) {
      GstCaps *filtered_intersection;
      
      filtered_intersection = gst_caps_intersect (intersection, 
	                                          filtercaps);

      gst_caps_unref (intersection);

      if (!filtered_intersection) {
        GST_INFO (GST_CAT_PADS, 
	          "filtered link between pads %s:%s and %s:%s is empty",
                  GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));
        return FALSE;
      }
      intersection = filtered_intersection;

      /* keep a reference to the app caps */
      gst_caps_replace_sink (&GST_RPAD_APPFILTER (realsink), filtercaps);
      gst_caps_replace_sink (&GST_RPAD_APPFILTER (realsrc), filtercaps);
    }
  }
  GST_DEBUG (GST_CAT_CAPS, "setting filter for link to:");
  gst_caps_debug (intersection, "filter for link");

  /* both the app filter and the filter, while stored on both peer pads, 
   * are equal to the same thing on both */
  gst_caps_replace_sink (&GST_RPAD_FILTER (realsrc), intersection); 
  gst_caps_replace_sink (&GST_RPAD_FILTER (realsink), intersection); 
  gst_caps_unref (intersection);

  return gst_pad_perform_negotiate (GST_PAD (realsrc), GST_PAD (realsink));
}

/**
 * gst_pad_perform_negotiate:
 * @srcpad: the source #GstPad.
 * @sinkpad: the sink #GstPad.
 *
 * Tries to negotiate the pads.
 *
 * Returns: TRUE if the pads were succesfully negotiated, FALSE otherwise.
 */
gboolean
gst_pad_perform_negotiate (GstPad *srcpad, GstPad *sinkpad) 
{
  GstCaps *intersection, *filtered_intersection;
  GstRealPad *realsrc, *realsink;
  GstCaps *srccaps, *sinkcaps, *filter;
  gboolean res = TRUE;
  GstElement *parent;
  

  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);
  
  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);
    
  g_return_val_if_fail (GST_RPAD_PEER (realsrc) != NULL, FALSE);
  g_return_val_if_fail (GST_RPAD_PEER (realsink) == realsrc, FALSE);

  /* shortcut negotiation */
  parent = GST_PAD_PARENT (realsrc);
  if (parent && GST_STATE (parent) < GST_STATE_READY) {
    GST_DEBUG (GST_CAT_CAPS, "parent %s of pad %s:%s is not READY",
	       GST_ELEMENT_NAME (parent), GST_DEBUG_PAD_NAME (realsrc));
    return TRUE;
  }
  parent = GST_PAD_PARENT (realsink);
  if (parent && GST_STATE (parent) < GST_STATE_READY) {
    GST_DEBUG (GST_CAT_CAPS, "parent %s of pad %s:%s is not READY",
	       GST_ELEMENT_NAME (parent), GST_DEBUG_PAD_NAME (realsink));
    return TRUE;
  }

  GST_INFO (GST_CAT_PADS, "perform negotiate for link %s:%s-%s:%s",
              GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));

  filter = GST_RPAD_APPFILTER (realsrc);
  if (filter) {
    GST_INFO (GST_CAT_PADS, "dumping filter for link %s:%s-%s:%s",
              GST_DEBUG_PAD_NAME (realsrc), GST_DEBUG_PAD_NAME (realsink));
    gst_caps_debug (filter, "link filter caps");
  }

  /* calculate the new caps here */
  srccaps = gst_pad_get_caps (GST_PAD (realsrc));
  GST_DEBUG (GST_CAT_PADS, "dumping caps of pad %s:%s", 
             GST_DEBUG_PAD_NAME (realsrc));
  gst_caps_debug (srccaps, 
                  "src caps, awaiting negotiation, after applying filter");
  sinkcaps = gst_pad_get_caps (GST_PAD (realsink));
  GST_DEBUG (GST_CAT_PADS, "dumping caps of pad %s:%s", 
             GST_DEBUG_PAD_NAME (realsink));
  gst_caps_debug (sinkcaps, 
                  "sink caps, awaiting negotiation, after applying filter");
  intersection = gst_caps_intersect (srccaps, sinkcaps);
  filtered_intersection = gst_caps_intersect (intersection, filter);
  gst_caps_unref (intersection);

  /* no negotiation is performed if the pads have filtercaps */
  if (filtered_intersection) {
    GstPadLinkReturn link_res;

    link_res = gst_pad_try_set_caps_func (realsrc, filtered_intersection, TRUE);
    if (link_res == GST_PAD_LINK_REFUSED) 
      goto error;
    if (link_res == GST_PAD_LINK_DONE) 
      goto success;

    link_res = gst_pad_try_set_caps_func (realsink, filtered_intersection, TRUE);
    if (link_res == GST_PAD_LINK_REFUSED) 
      goto error;
    if (link_res == GST_PAD_LINK_DONE) 
      goto success;
  }
  /* no filtered_intersection, some pads had caps and ther was a filter */
  else if ((srccaps || sinkcaps) && filter) {
    goto error;
  }

success:
cleanup:
  gst_caps_sink (srccaps);
  gst_caps_sink (sinkcaps);
  gst_caps_unref (filtered_intersection);
  return res;

error:
  res = FALSE;
  goto cleanup;
}

/**
 * gst_pad_try_relink_filtered:
 * @srcpad: the source #GstPad to relink.
 * @sinkpad: the sink #GstPad to relink.
 * @filtercaps: the #GstPad to use as a filter in the relink.
 *
 * Tries to relink the given source and sink pad, constrained by the given
 * capabilities.
 *
 * Returns: TRUE if the pads were succesfully renegotiated, FALSE otherwise.
 */
gboolean
gst_pad_try_relink_filtered (GstPad *srcpad, GstPad *sinkpad, 
                                GstCaps *filtercaps)
{
  GstRealPad *realsrc, *realsink;

  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);

  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  g_return_val_if_fail (GST_RPAD_PEER (realsrc) != NULL, FALSE);
  g_return_val_if_fail (GST_RPAD_PEER (realsink) == realsrc, FALSE);
  
  return gst_pad_try_relink_filtered_func (realsrc, realsink, 
                                           filtercaps, TRUE);
}

/**
 * gst_pad_relink_filtered:
 * @srcpad: the source #GstPad to relink.
 * @sinkpad: the sink #GstPad to relink.
 * @filtercaps: the #GstPad to use as a filter in the relink.
 *
 * Relinks the given source and sink pad, constrained by the given
 * capabilities.  If the relink fails, the pads are unlinked
 * and FALSE is returned.
 *
 * Returns: TRUE if the pads were succesfully relinked, FALSE otherwise.
 */
gboolean
gst_pad_relink_filtered (GstPad *srcpad, GstPad *sinkpad, 
                            GstCaps *filtercaps)
{
  GstRealPad *realsrc, *realsink;

  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);

  realsrc = GST_PAD_REALIZE (srcpad);
  realsink = GST_PAD_REALIZE (sinkpad);

  g_return_val_if_fail (GST_RPAD_PEER (realsrc) != NULL, FALSE);
  g_return_val_if_fail (GST_RPAD_PEER (realsink) == realsrc, FALSE);
  
  if (!gst_pad_try_relink_filtered_func (realsrc, realsink, 
	                                 filtercaps, TRUE)) 
  {
    gst_pad_unlink (srcpad, GST_PAD (GST_PAD_PEER (srcpad)));
    return FALSE;
  }
  return TRUE;
}

/**
 * gst_pad_proxy_link:
 * @pad: a #GstPad to proxy to.
 * @caps: the #GstCaps to use in proxying.
 *
 * Proxies the link function to the specified pad.
 *
 * Returns: TRUE if the peer pad accepted the caps, FALSE otherwise.
 */
GstPadLinkReturn
gst_pad_proxy_link (GstPad *pad, GstCaps *caps)
{
  GstRealPad *peer, *realpad;

  realpad = GST_PAD_REALIZE (pad);

  peer = GST_RPAD_PEER (realpad);

  GST_INFO (GST_CAT_CAPS, "proxy link to pad %s:%s",
            GST_DEBUG_PAD_NAME (realpad));

  if (peer && gst_pad_try_set_caps_func (peer, caps, TRUE) < 0)
    return GST_PAD_LINK_REFUSED;
  if (gst_pad_try_set_caps_func (realpad, caps, FALSE) < 0)
    return GST_PAD_LINK_REFUSED;

  return GST_PAD_LINK_OK;
}

/**
 * gst_pad_get_caps:
 * @pad: a  #GstPad to get the capabilities of.
 *
 * Gets the capabilities of this pad.
 *
 * Returns: the #GstCaps of this pad. This function potentially
 * returns a floating caps, so use gst_caps_sink to get rid of
 * it.
 */
GstCaps*
gst_pad_get_caps (GstPad *pad)
{
  GstRealPad *realpad;

  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  realpad = GST_PAD_REALIZE (pad);

  GST_DEBUG (GST_CAT_CAPS, "get pad caps of %s:%s (%p)",
            GST_DEBUG_PAD_NAME (realpad), realpad);

  /* note that we will not _ref the caps here as this function might be 
   * called recursively */
  if (GST_PAD_CAPS (realpad)) {
    GST_DEBUG (GST_CAT_CAPS, "using pad real caps %p", GST_PAD_CAPS (realpad));
    return GST_PAD_CAPS (realpad);
  }
  else if GST_RPAD_GETCAPSFUNC (realpad) {
    GST_DEBUG (GST_CAT_CAPS, "using pad get function");
    return GST_RPAD_GETCAPSFUNC (realpad) (GST_PAD_CAST (realpad), NULL);
  }
  else if (GST_PAD_PAD_TEMPLATE (realpad)) {
    GstPadTemplate *templ = GST_PAD_PAD_TEMPLATE (realpad);
    GST_DEBUG (GST_CAT_CAPS, "using pad template %p with caps %p", 
	       templ, GST_PAD_TEMPLATE_CAPS (templ));
    return GST_PAD_TEMPLATE_CAPS (templ);
  }
  GST_DEBUG (GST_CAT_CAPS, "pad has no caps");

  return NULL;
}

/**
 * gst_pad_get_pad_template_caps:
 * @pad: a #GstPad to get the template capabilities from.
 *
 * Gets the template capabilities of this pad.
 *
 * Returns: the template #GstCaps of this pad, unref the caps
 * if you no longer need it.
 */
GstCaps*
gst_pad_get_pad_template_caps (GstPad *pad)
{
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  if (GST_PAD_PAD_TEMPLATE (pad))
    return gst_caps_ref (GST_PAD_TEMPLATE_CAPS (GST_PAD_PAD_TEMPLATE (pad)));

  return NULL;
}

/**
 * gst_pad_template_get_caps_by_name:
 * @templ: a #GstPadTemplate to get the capabilities of.
 * @name: the name of the capability to get.
 *
 * Gets the capability with the given name from this pad template.
 *
 * Returns: the #GstCaps, or NULL if not found or in case of an error. unref 
 * the caps if you no longer need it.
 */
GstCaps*
gst_pad_template_get_caps_by_name (GstPadTemplate *templ, const gchar *name)
{
  GstCaps *caps;

  g_return_val_if_fail (templ != NULL, NULL);

  caps = GST_PAD_TEMPLATE_CAPS (templ);
  if (!caps) 
    return NULL;

  return gst_caps_ref (gst_caps_get_by_name (caps, name));
}

/**
 * gst_pad_check_compatibility:
 * @srcpad: the source #GstPad to check.
 * @sinkpad: the sink #GstPad to check against.
 *
 * Checks if two pads have compatible capabilities.
 *
 * Returns: TRUE if they are compatible or if the capabilities
 * could not be checked
 */
gboolean
gst_pad_check_compatibility (GstPad *srcpad, GstPad *sinkpad)
{
  g_return_val_if_fail (srcpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (srcpad), FALSE);
  g_return_val_if_fail (sinkpad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (sinkpad), FALSE);

  if (GST_PAD_CAPS (srcpad) && GST_PAD_CAPS (sinkpad)) {
    if (!gst_caps_is_always_compatible (GST_PAD_CAPS (srcpad), 
	                                GST_PAD_CAPS (sinkpad))) {
      return FALSE;
    }
    else {
      return TRUE;
    }
  }
  else {
    GST_DEBUG (GST_CAT_PADS, 
	       "could not check capabilities of pads (%s:%s) and (%s:%s) %p %p",
	       GST_DEBUG_PAD_NAME (srcpad), GST_DEBUG_PAD_NAME (sinkpad), 
	       GST_PAD_CAPS (srcpad), GST_PAD_CAPS (sinkpad));
    return TRUE;
  }
}

/**
 * gst_pad_get_peer:
 * @pad: a #GstPad to get the peer of.
 *
 * Gets the peer pad of this pad.
 *
 * Returns: the peer #GstPad.
 */
GstPad*
gst_pad_get_peer (GstPad *pad)
{
  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  return GST_PAD (GST_PAD_PEER (pad));
}

/**
 * gst_pad_get_allowed_caps:
 * @pad: a #GstPad to get the allowed caps of.
 *
 * Gets the capabilities of the allowed media types that can
 * flow through this pad.  The caller must free the resulting caps.
 *
 * Returns: the allowed #GstCaps of the pad link. unref the caps if
 * you no longer need it.
 */
GstCaps*
gst_pad_get_allowed_caps (GstPad *pad)
{
  GstCaps *caps;

  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  GST_DEBUG (GST_CAT_PROPERTIES, "get allowed caps of %s:%s", 
             GST_DEBUG_PAD_NAME (pad));

  caps = gst_caps_ref (GST_RPAD_FILTER (pad));

  return caps;
}

/**
 * gst_pad_recalc_allowed_caps:
 * @pad: a #GstPad to recalculate the capablities of.
 *
 * Attempts to relink the pad to its peer through its filter, 
 * set with gst_pad_[re]link_filtered. This function is useful when a
 * plug-in has new capabilities on a pad and wants to notify the peer.
 *
 * Returns: TRUE on success, FALSE otherwise.
 */
gboolean
gst_pad_recalc_allowed_caps (GstPad *pad)
{
  GstRealPad *peer;

  g_return_val_if_fail (pad != NULL, FALSE);
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  GST_DEBUG (GST_CAT_PROPERTIES, "set allowed caps of %s:%s", 
             GST_DEBUG_PAD_NAME (pad));


  peer = GST_RPAD_PEER (pad);
  if (peer)
    return gst_pad_try_relink_filtered (pad, GST_PAD (peer), 
	                                GST_RPAD_APPFILTER (pad));

  return TRUE;
}

/**
 * gst_pad_get_bufferpool:
 * @pad: a #GstPad to get the bufferpool from.
 *
 * Gets the bufferpool of the peer pad of the given pad.Note that
 * a bufferpool can only be obtained from a srcpad.
 *
 * Returns: the #GstBufferPool, or NULL in case of an error.
 */
GstBufferPool*          
gst_pad_get_bufferpool (GstPad *pad)
{
  GstRealPad *peer;

  g_return_val_if_fail (pad != NULL, NULL);
  g_return_val_if_fail (GST_IS_PAD (pad), NULL);
  g_return_val_if_fail (GST_PAD_IS_SRC (pad), NULL);
   
  peer = GST_RPAD_PEER (pad);

  if (!peer)
    return NULL;

  GST_DEBUG_ENTER ("(%s:%s)", GST_DEBUG_PAD_NAME (pad));

  if (peer->bufferpoolfunc) {
    GST_DEBUG (GST_CAT_PADS, 
	       "calling bufferpoolfunc &%s (@%p) of peer pad %s:%s",
               GST_DEBUG_FUNCPTR_NAME (peer->bufferpoolfunc), 
	       &peer->bufferpoolfunc, GST_DEBUG_PAD_NAME (((GstPad*) peer)));
    return (peer->bufferpoolfunc) (((GstPad*) peer));
  } else {
    GST_DEBUG (GST_CAT_PADS, "no bufferpoolfunc for peer pad %s:%s at %p",
	       GST_DEBUG_PAD_NAME (((GstPad*) peer)), &peer->bufferpoolfunc);
    return NULL;
  }
}

static void
gst_real_pad_dispose (GObject *object)
{
  GstPad *pad = GST_PAD (object);
  
  /* No linked pad can ever be disposed.
   * It has to have a parent to be linked 
   * and a parent would hold a reference */
  g_assert (GST_PAD_PEER (pad) == NULL);

  GST_DEBUG (GST_CAT_REFCOUNTING, "dispose %s:%s", GST_DEBUG_PAD_NAME(pad));

  if (GST_PAD_PAD_TEMPLATE (pad)){
    GST_DEBUG (GST_CAT_REFCOUNTING, "unreffing padtemplate'%s'", 
	       GST_OBJECT_NAME (GST_PAD_PAD_TEMPLATE (pad)));
    gst_object_unref (GST_OBJECT (GST_PAD_PAD_TEMPLATE (pad)));
    GST_PAD_PAD_TEMPLATE (pad) = NULL;
  }
  
  /* we destroy the ghostpads, because they are nothing without the real pad */
  if (GST_REAL_PAD (pad)->ghostpads) {
    GList *orig, *ghostpads;

    orig = ghostpads = g_list_copy (GST_REAL_PAD (pad)->ghostpads);

    while (ghostpads) {
      GstPad *ghostpad = GST_PAD (ghostpads->data);

      if (GST_IS_ELEMENT (GST_OBJECT_PARENT (ghostpad))){
        GST_DEBUG (GST_CAT_REFCOUNTING, "removing ghost pad from element '%s'", 
		   GST_OBJECT_NAME (GST_OBJECT_PARENT (ghostpad)));

        gst_element_remove_ghost_pad (GST_ELEMENT (GST_OBJECT_PARENT (ghostpad)), GST_PAD (ghostpad));
      }
      ghostpads = g_list_next (ghostpads);
    }
    g_list_free (orig);
    g_list_free (GST_REAL_PAD(pad)->ghostpads);
  }

  gst_caps_replace (&GST_PAD_CAPS (pad), NULL);
  gst_caps_replace (&GST_RPAD_APPFILTER (pad), NULL);

  if (GST_IS_ELEMENT (GST_OBJECT_PARENT (pad))) {
    GST_DEBUG (GST_CAT_REFCOUNTING, "removing pad from element '%s'",
               GST_OBJECT_NAME (GST_OBJECT (GST_ELEMENT (GST_OBJECT_PARENT (pad)))));
    
    gst_element_remove_pad (GST_ELEMENT (GST_OBJECT_PARENT (pad)), pad);
  }
  
  G_OBJECT_CLASS (real_pad_parent_class)->dispose (object);
}


#ifndef GST_DISABLE_LOADSAVE
/* FIXME: why isn't this on a GstElement ? */
/**
 * gst_pad_load_and_link:
 * @self: an #xmlNodePtr to read the description from.
 * @parent: the #GstObject element that owns the pad.
 *
 * Reads the pad definition from the XML node and links the given pad
 * in the element to a pad of an element up in the hierarchy.
 */
void
gst_pad_load_and_link (xmlNodePtr self, GstObject *parent)
{
  xmlNodePtr field = self->xmlChildrenNode;
  GstPad *pad = NULL, *targetpad;
  gchar *peer = NULL;
  gchar **split;
  GstElement *target;
  GstObject *grandparent;

  while (field) {
    if (!strcmp (field->name, "name")) {
      pad = gst_element_get_pad (GST_ELEMENT (parent), 
	                         xmlNodeGetContent (field));
    }
    else if (!strcmp(field->name, "peer")) {
      peer = xmlNodeGetContent (field);
    }
    field = field->next;
  }
  g_return_if_fail (pad != NULL);

  if (peer == NULL) return;

  split = g_strsplit (peer, ".", 2);

  if (split[0] == NULL || split[1] == NULL) {
    GST_DEBUG (GST_CAT_XML, 
	       "Could not parse peer '%s' for pad %s:%s, leaving unlinked",
               peer, GST_DEBUG_PAD_NAME (pad));
    return;
  }
  
  g_return_if_fail (split[0] != NULL);
  g_return_if_fail (split[1] != NULL);

  grandparent = gst_object_get_parent (parent);

  if (grandparent && GST_IS_BIN (grandparent)) {
    target = gst_bin_get_by_name_recurse_up (GST_BIN (grandparent), split[0]);
  }
  else
    goto cleanup;

  if (target == NULL) goto cleanup;

  targetpad = gst_element_get_pad (target, split[1]);

  if (targetpad == NULL) goto cleanup;

  gst_pad_link (pad, targetpad);

cleanup:
  g_strfreev (split);
}

/**
 * gst_pad_save_thyself:
 * @pad: a #GstPad to save.
 * @parent: the parent #xmlNodePtr to save the description in.
 *
 * Saves the pad into an xml representation.
 *
 * Returns: the #xmlNodePtr representation of the pad.
 */
static xmlNodePtr
gst_pad_save_thyself (GstObject *object, xmlNodePtr parent)
{
  GstRealPad *realpad;
  GstPad *peer;

  g_return_val_if_fail (GST_IS_REAL_PAD (object), NULL);

  realpad = GST_REAL_PAD (object);

  xmlNewChild (parent, NULL, "name", GST_PAD_NAME (realpad));
  if (GST_RPAD_PEER (realpad) != NULL) {
    gchar *content;
    
    peer = GST_PAD (GST_RPAD_PEER (realpad));
    /* first check to see if the peer's parent's parent is the same */
    /* we just save it off */
    content = g_strdup_printf ("%s.%s",
			       GST_OBJECT_NAME (GST_PAD_PARENT (peer)),
			       GST_PAD_NAME (peer));
    xmlNewChild (parent, NULL, "peer", content);
    g_free (content);
  } else
    xmlNewChild (parent, NULL, "peer", "");

  return parent;
}

/* FIXME: shouldn't pad and ghost be switched ?
 */
/**
 * gst_ghost_pad_save_thyself:
 * @pad: a ghost #GstPad to save.
 * @parent: the parent #xmlNodePtr to save the description in.
 *
 * Saves the ghost pad into an xml representation.
 *
 * Returns: the #xmlNodePtr representation of the pad.
 */
xmlNodePtr
gst_ghost_pad_save_thyself (GstPad *pad, xmlNodePtr parent)
{
  xmlNodePtr self;

  g_return_val_if_fail (GST_IS_GHOST_PAD (pad), NULL);

  self = xmlNewChild (parent, NULL, "ghostpad", NULL);
  xmlNewChild (self, NULL, "name", GST_PAD_NAME (pad));
  xmlNewChild (self, NULL, "parent", GST_OBJECT_NAME (GST_PAD_PARENT (pad)));

  /* FIXME FIXME FIXME! */

  return self;
}
#endif /* GST_DISABLE_LOADSAVE */

/**
 * gst_pad_push:
 * @pad: a #GstPad to push the buffer out of.
 * @buf: the #GstBuffer to push.
 *
 * Pushes a buffer to the peer of the pad.
 */
void 
gst_pad_push (GstPad *pad, GstBuffer *buf) 
{
  GstRealPad *peer;

  GST_DEBUG_ENTER ("(%s:%s)", GST_DEBUG_PAD_NAME (pad));

  g_return_if_fail (GST_PAD_DIRECTION (pad) == GST_PAD_SRC);

  if (!gst_probe_dispatcher_dispatch (&(GST_REAL_PAD (pad)->probedisp), (GstData **) &buf))
    return;

  peer = GST_RPAD_PEER (pad);

  if (!peer) {
    g_warning ("push on pad %s:%s but it is unlinked", 
	       GST_DEBUG_PAD_NAME (pad));
  }
  else {
    if (!GST_IS_EVENT (buf) && !GST_PAD_IS_ACTIVE (pad)) {
      g_warning ("push on pad %s:%s but it is not active", 
	         GST_DEBUG_PAD_NAME (pad));
      return;
    }

    if (peer->chainhandler) {
      if (buf) {
        GST_DEBUG (GST_CAT_DATAFLOW, 
	           "calling chainhandler &%s of peer pad %s:%s",
                   GST_DEBUG_FUNCPTR_NAME (peer->chainhandler), 
		   GST_DEBUG_PAD_NAME (GST_PAD (peer)));
        if (!gst_probe_dispatcher_dispatch (&peer->probedisp, (GstData **) &buf))
          return;

        (peer->chainhandler) (GST_PAD_CAST (peer), buf);
	return;
      }
      else {
        g_warning ("trying to push a NULL buffer on pad %s:%s", 
	           GST_DEBUG_PAD_NAME (peer));
	return;
      }
    } 
    else {
      g_warning ("internal error: push on pad %s:%s but it has no chainhandler",
	         GST_DEBUG_PAD_NAME (peer));
    }
  }
  /* clean up the mess here */
  if (buf != NULL) gst_data_unref (GST_DATA (buf));
}

/**
 * gst_pad_pull:
 * @pad: a #GstPad to pull a buffer from.
 *
 * Pulls a buffer from the peer pad.
 *
 * Returns: a new #GstBuffer from the peer pad.
 */
GstBuffer*
gst_pad_pull (GstPad *pad) 
{
  GstRealPad *peer;
  
  GST_DEBUG_ENTER("(%s:%s)",GST_DEBUG_PAD_NAME(pad));

  g_return_val_if_fail (GST_PAD_DIRECTION (pad) == GST_PAD_SINK, 
          	        GST_BUFFER (gst_event_new (GST_EVENT_INTERRUPT)));

  peer = GST_RPAD_PEER (pad);

  if (!peer) {
    gst_element_error (GST_PAD_PARENT (pad), 
		       "pull on pad %s:%s but it was unlinked", 
		       GST_ELEMENT_NAME (GST_PAD_PARENT (pad)), 
		       GST_PAD_NAME (pad), NULL);
  }
  else {
restart:
    if (peer->gethandler) {
      GstBuffer *buf;
      gboolean active = GST_PAD_IS_ACTIVE (peer);

      GST_DEBUG (GST_CAT_DATAFLOW, "calling gethandler %s of peer pad %s:%s",
                 GST_DEBUG_FUNCPTR_NAME (peer->gethandler), 
		 GST_DEBUG_PAD_NAME (peer));

      buf = (peer->gethandler) (GST_PAD_CAST (peer));

      if (buf) {
        if (!gst_probe_dispatcher_dispatch (&peer->probedisp, (GstData **) &buf))
          goto restart;

        if (!GST_IS_EVENT (buf) && !active) {
          g_warning ("pull on pad %s:%s but it is not active", 
	         GST_DEBUG_PAD_NAME (peer));
          return GST_BUFFER (gst_event_new (GST_EVENT_INTERRUPT));
        }
        return buf;
      }

      /* no null buffers allowed */
      gst_element_error (GST_PAD_PARENT (pad), 
	                 "NULL buffer during pull on %s:%s", 
			 GST_DEBUG_PAD_NAME (pad), NULL);
	  
    } else {
      gst_element_error (GST_PAD_PARENT (pad), 
		         "internal error: pull on pad %s:%s "
			 "but the peer pad %s:%s has no gethandler", 
		         GST_DEBUG_PAD_NAME (pad), GST_DEBUG_PAD_NAME (peer),
		         NULL);
    }
  }
  return GST_BUFFER (gst_event_new (GST_EVENT_INTERRUPT));
}

/**
 * gst_pad_select:
 * @padlist: a #GList of pads.
 *
 * Waits for a buffer on any of the list of pads.
 *
 * Returns: the #GstPad that has a buffer available. 
 * Use #gst_pad_pull() to get the buffer.
 */
GstPad*
gst_pad_select (GList *padlist)
{
  GstPad *pad;

  pad = gst_scheduler_pad_select (GST_PAD_PARENT (padlist->data)->sched, 
                                  padlist);
  return pad;
}

/**
 * gst_pad_selectv:
 * @pad: a first #GstPad to perform the select on.
 * @...: A NULL-terminated list of more pads to select on.
 *
 * Waits for a buffer on the given set of pads.
 *
 * Returns: the #GstPad that has a buffer available.
 * Use #gst_pad_pull() to get the buffer.
 */
GstPad*
gst_pad_selectv (GstPad *pad, ...)
{
  GstPad *result;
  GList *padlist = NULL;
  va_list var_args;

  if (pad == NULL)
    return NULL;

  va_start (var_args, pad);

  while (pad) {
    padlist = g_list_prepend (padlist, pad);
    pad = va_arg (var_args, GstPad *);
  }
  result = gst_pad_select (padlist);
  g_list_free (padlist);

  va_end (var_args);
  
  return result;
}

/************************************************************************
 *
 * templates
 *
 */
static void		gst_pad_template_class_init	(GstPadTemplateClass *klass);
static void		gst_pad_template_init		(GstPadTemplate *templ);
static void 		gst_pad_template_dispose 	(GObject *object);

GType
gst_pad_template_get_type (void)
{
  static GType padtemplate_type = 0;

  if (!padtemplate_type) {
    static const GTypeInfo padtemplate_info = {
      sizeof (GstPadTemplateClass), NULL, NULL,
      (GClassInitFunc) gst_pad_template_class_init, NULL, NULL,
      sizeof (GstPadTemplate),
      32,
      (GInstanceInitFunc) gst_pad_template_init, NULL
    };
    padtemplate_type = g_type_register_static(GST_TYPE_OBJECT, "GstPadTemplate",
                                              &padtemplate_info, 0);
  }
  return padtemplate_type;
}

static void
gst_pad_template_class_init (GstPadTemplateClass *klass)
{
  GObjectClass *gobject_class;
  GstObjectClass *gstobject_class;

  gobject_class = (GObjectClass*) klass;
  gstobject_class = (GstObjectClass*) klass;

  padtemplate_parent_class = g_type_class_ref (GST_TYPE_OBJECT);

  gst_pad_template_signals[TEMPL_PAD_CREATED] =
    g_signal_new ("pad_created", G_TYPE_FROM_CLASS (klass), G_SIGNAL_RUN_LAST,
                  G_STRUCT_OFFSET (GstPadTemplateClass, pad_created), 
		  NULL, NULL, gst_marshal_VOID__POINTER, G_TYPE_NONE, 1,
                  G_TYPE_POINTER);

  gobject_class->dispose = gst_pad_template_dispose;

  gstobject_class->path_string_separator = "*";
}

static void
gst_pad_template_init (GstPadTemplate *templ)
{
}

static void
gst_pad_template_dispose (GObject *object)
{
  GstPadTemplate *templ = GST_PAD_TEMPLATE (object);

  g_free (GST_PAD_TEMPLATE_NAME_TEMPLATE (templ));
  gst_caps_unref (GST_PAD_TEMPLATE_CAPS (templ));

  G_OBJECT_CLASS (padtemplate_parent_class)->dispose (object);
}

/* ALWAYS padtemplates cannot have conversion specifications, it doesn't make
 * sense.
 * SOMETIMES padtemplates can do whatever they want, they are provided by the
 * element.
 * REQUEST padtemplates can be reverse-parsed (the user asks for 'sink1', the
 * 'sink%d' template is automatically selected), so we need to restrict their
 * naming.
 */
static gboolean
name_is_valid (const gchar *name, GstPadPresence presence)
{
  const gchar *str;
  
  if (presence == GST_PAD_ALWAYS) {
    if (strchr (name, '%')) {
      g_warning ("invalid name template %s: conversion specifications are not"
                 " allowed for GST_PAD_ALWAYS padtemplates", name);
      return FALSE;
    }
  } else if (presence == GST_PAD_REQUEST) {
    if ((str = strchr (name, '%')) && strchr (str + 1, '%')) {
      g_warning ("invalid name template %s: only one conversion specification"
                 " allowed in GST_PAD_REQUEST padtemplate", name);
      return FALSE;
    }
    if (str && (*(str+1) != 's' && *(str+1) != 'd')) {
      g_warning ("invalid name template %s: conversion specification must be of"
                 " type '%%d' or '%%s' for GST_PAD_REQUEST padtemplate", name);
      return FALSE;
    }
    if (str && (*(str+2) != '\0')) {
      g_warning ("invalid name template %s: conversion specification must"
                 " appear at the end of the GST_PAD_REQUEST padtemplate name", 
		 name);
      return FALSE;
    }
  }
  
  return TRUE;
}

/**
 * gst_pad_template_new:
 * @name_template: the name template.
 * @direction: the #GstPadDirection of the template.
 * @presence: the #GstPadPresence of the pad.
 * @caps: a #GstCaps set for the template.
 * @...: a NULL-terminated list of #GstCaps.
 *
 * Creates a new pad template with a name according to the given template
 * and with the given arguments.
 *
 * Returns: a new #GstPadTemplate.
 */
GstPadTemplate*
gst_pad_template_new (const gchar *name_template,
		     GstPadDirection direction, GstPadPresence presence,
		     GstCaps *caps, ...)
{
  GstPadTemplate *new;
  va_list var_args;
  GstCaps *thecaps = NULL;

  g_return_val_if_fail (name_template != NULL, NULL);

  if (!name_is_valid (name_template, presence))
    return NULL;

  new = g_object_new (gst_pad_template_get_type (),
                      "name", name_template,
                      NULL);

  GST_PAD_TEMPLATE_NAME_TEMPLATE (new) = g_strdup (name_template);
  GST_PAD_TEMPLATE_DIRECTION (new) = direction;
  GST_PAD_TEMPLATE_PRESENCE (new) = presence;

  va_start (var_args, caps);

  GST_FLAG_SET (GST_OBJECT (new), GST_PAD_TEMPLATE_FIXED);
  while (caps) {
    if (!GST_CAPS_IS_FIXED (caps)) {
      GST_FLAG_UNSET (GST_OBJECT (new), GST_PAD_TEMPLATE_FIXED);
    }
    thecaps = gst_caps_append (thecaps, caps);
    caps = va_arg (var_args, GstCaps*);
  }
  va_end (var_args);
  
  GST_PAD_TEMPLATE_CAPS (new) = thecaps;
  gst_caps_ref (thecaps);
  gst_caps_sink (thecaps);

  return new;
}

/**
 * gst_pad_template_get_caps:
 * @templ: a #GstPadTemplate to get capabilities of.
 *
 * Gets the capabilities of the pad template.
 *
 * Returns: the #GstCaps of the pad template. unref the caps
 * after use.
 */
GstCaps*
gst_pad_template_get_caps (GstPadTemplate *templ)
{
  g_return_val_if_fail (templ != NULL, NULL);

  return gst_caps_ref (GST_PAD_TEMPLATE_CAPS (templ));
}

/**
 * gst_pad_set_element_private:
 * @pad: the #GstPad to set the private data of.
 * @priv: The private data to attach to the pad.
 *
 * Set the given private data gpointer on the pad. 
 * This function can only be used by the element that owns the pad.
 */
void
gst_pad_set_element_private (GstPad *pad, gpointer priv)
{
  pad->element_private = priv;
}

/**
 * gst_pad_get_element_private:
 * @pad: the #GstPad to get the private data of.
 *
 * Gets the private data of a pad.
 *
 * Returns: a #gpointer to the private data.
 */
gpointer
gst_pad_get_element_private (GstPad *pad)
{
  return pad->element_private;
}


/***** ghost pads *****/
GType _gst_ghost_pad_type = 0;

static void     gst_ghost_pad_class_init         (GstGhostPadClass *klass);
static void     gst_ghost_pad_init               (GstGhostPad *pad);

static GstPad *ghost_pad_parent_class = NULL;
/* static guint gst_ghost_pad_signals[LAST_SIGNAL] = { 0 }; */

GType
gst_ghost_pad_get_type (void) 
{
  if (!_gst_ghost_pad_type) {
    static const GTypeInfo pad_info = {
      sizeof (GstGhostPadClass), NULL, NULL,
      (GClassInitFunc) gst_ghost_pad_class_init, NULL, NULL,
      sizeof (GstGhostPad),
      8,
      (GInstanceInitFunc) gst_ghost_pad_init,
      NULL
    };
    _gst_ghost_pad_type = g_type_register_static (GST_TYPE_PAD, "GstGhostPad", 
	                                          &pad_info, 0);
  }
  return _gst_ghost_pad_type;
}

static void
gst_ghost_pad_class_init (GstGhostPadClass *klass)
{
  GObjectClass *gobject_class;

  gobject_class = (GObjectClass*) klass;

  ghost_pad_parent_class = g_type_class_ref (GST_TYPE_PAD);
}

static void
gst_ghost_pad_init (GstGhostPad *pad)
{
  pad->realpad = NULL;
}

/**
 * gst_ghost_pad_new:
 * @name: the name of the new ghost pad.
 * @pad: the #GstPad to create a ghost pad for.
 *
 * Creates a new ghost pad associated with the given pad, and names it with
 * the given name.  If name is NULL, a guaranteed unique name (across all
 * ghost pads) will be assigned (most likely of the form ghostpad&perc;d).
 *
 * Returns: a new ghost #GstPad, or NULL in case of an error.
 */

GstPad*
gst_ghost_pad_new (const gchar *name,
                   GstPad *pad)
{
  GstGhostPad *ghostpad;
  GstRealPad *realpad;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  ghostpad = g_object_new (gst_ghost_pad_get_type () ,NULL);
  gst_pad_set_name (GST_PAD (ghostpad), name);

  realpad = (GstRealPad *) pad;

  while (!GST_IS_REAL_PAD (realpad)) {
    realpad = GST_PAD_REALIZE (realpad);
  }
  GST_GPAD_REALPAD (ghostpad) = realpad;
  GST_PAD_PAD_TEMPLATE (ghostpad) = GST_PAD_PAD_TEMPLATE (pad);

  /* add ourselves to the real pad's list of ghostpads */
  gst_pad_add_ghost_pad (pad, GST_PAD (ghostpad));

  /* FIXME need to ref the real pad here... ? */

  GST_DEBUG (GST_CAT_PADS, "created ghost pad \"%s\"", 
             gst_pad_get_name (GST_PAD (ghostpad)));

  return GST_PAD (ghostpad);
}

/**
 * gst_pad_get_internal_links_default:
 * @pad: the #GstPad to get the internal links of.
 *
 * Gets a list of pads to which the given pad is linked to
 * inside of the parent element.
 * This is the default handler, and thus returns a list of all of the
 * pads inside the parent element with opposite direction.
 * The caller must free this list after use.
 *
 * Returns: a newly allocated #GList of pads.
 */
GList*
gst_pad_get_internal_links_default (GstPad *pad)
{
  GList *res = NULL;
  GstElement *parent;
  GList *parent_pads;
  GstPadDirection direction;
  GstRealPad *rpad;
  
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  rpad = GST_PAD_REALIZE (pad);
  direction = rpad->direction;

  parent = GST_PAD_PARENT (rpad);
  parent_pads = parent->pads;

  while (parent_pads) {
    GstRealPad *parent_pad = GST_PAD_REALIZE (parent_pads->data);
    
    if (parent_pad->direction != direction) {
      res = g_list_prepend (res, parent_pad);
    }
    
    parent_pads = g_list_next (parent_pads);
  }

  return res;
}

/**
 * gst_pad_get_internal_links:
 * @pad: the #GstPad to get the internal links of.
 *
 * Gets a list of pads to which the given pad is linked to
 * inside of the parent element.
 * The caller must free this list after use.
 *
 * Returns: a newly allocated #GList of pads.
 */
GList*
gst_pad_get_internal_links (GstPad *pad)
{
  GList *res = NULL;
  GstRealPad *rpad;

  g_return_val_if_fail (GST_IS_PAD (pad), NULL);

  rpad = GST_PAD_REALIZE (pad);

  if (GST_RPAD_INTLINKFUNC (rpad))
    res = GST_RPAD_INTLINKFUNC (rpad) (GST_PAD_CAST (rpad));

  return res;
}


static gboolean 
gst_pad_event_default_dispatch (GstPad *pad, GstElement *element, 
                                GstEvent *event)
{
  GList *pads = element->pads;

  while (pads) {
    GstPad *eventpad = GST_PAD (pads->data);
    pads = g_list_next (pads);

    /* for all pads in the opposite direction that are linked */
    if (GST_PAD_DIRECTION (eventpad) != GST_PAD_DIRECTION (pad) 
     && GST_PAD_IS_LINKED (eventpad)) {
      if (GST_PAD_DIRECTION (eventpad) == GST_PAD_SRC) {
	/* increase the refcount */
        gst_event_ref (event);
        gst_pad_push (eventpad, GST_BUFFER (event));
      }
      else {
	GstPad *peerpad = GST_PAD_CAST (GST_RPAD_PEER (eventpad));

	/* we only send the event on one pad, multi-sinkpad elements 
	 * should implement a handler */
        return gst_pad_send_event (peerpad, event);
      }
    }
  }
  gst_event_unref (event);
  return TRUE;
}

/**
 * gst_pad_event_default:
 * @pad: a #GstPad to call the default event handler on.
 * @event: the #GstEvent to handle.
 *
 * Invokes the default event handler for the given pad.
 *
 * Returns: TRUE if the event was sent succesfully.
 */
gboolean 
gst_pad_event_default (GstPad *pad, GstEvent *event)
{
  GstElement *element;
  
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (event, FALSE);
  
  element = GST_PAD_PARENT (pad);

  switch (GST_EVENT_TYPE (event)) {
    case GST_EVENT_EOS:
      gst_pad_event_default_dispatch (pad, element, event);
      gst_element_set_eos (element);
      break;
    case GST_EVENT_DISCONTINUOUS:
    {
      guint64 time;
	      
      if (gst_event_discont_get_value (event, GST_FORMAT_TIME, &time)) {
      	if (gst_element_requires_clock (element) && element->clock) {
	  gst_clock_handle_discont (element->clock, time); 
  	}
      }
    }
    case GST_EVENT_FLUSH:
    default:
      return gst_pad_event_default_dispatch (pad, element, event);
  }
  return TRUE;
}

/**
 * gst_pad_dispatcher:
 * @pad: a #GstPad to dispatch.
 * @dispatch: the #GstDispatcherFunction to call.
 * @data: gpointer user data passed to the dispatcher function.
 *
 * Invokes the given dispatcher function on all pads that are 
 * internally linked to the given pad. 
 * The GstPadDispatcherFunction should return TRUE when no further pads 
 * need to be processed.
 *
 * Returns: TRUE if one of the dispatcher functions returned TRUE.
 */
gboolean
gst_pad_dispatcher (GstPad *pad, GstPadDispatcherFunction dispatch, 
                    gpointer data)
{
  gboolean res = FALSE;
  GList *int_pads, *orig;
  
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (data, FALSE);

  orig = int_pads = gst_pad_get_internal_links (pad);

  while (int_pads) {
    GstRealPad *int_rpad = GST_PAD_REALIZE (int_pads->data);
    GstRealPad *int_peer = GST_RPAD_PEER (int_rpad);

    if (int_peer) {
      res = dispatch (GST_PAD_CAST (int_peer), data);
      if (res)
        break;
    }
    int_pads = g_list_next (int_pads);
  }

  g_list_free (orig);
  
  return res;
}

/**
 * gst_pad_send_event:
 * @pad: a #GstPad to send the event to.
 * @event: the #GstEvent to send to the pad.
 *
 * Sends the event to the pad.
 *
 * Returns: TRUE if the event was handled.
 */
gboolean
gst_pad_send_event (GstPad *pad, GstEvent *event)
{
  gboolean success = FALSE;
  GstRealPad *rpad;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (event, FALSE);

  rpad = GST_PAD_REALIZE (pad);

  if (GST_EVENT_SRC (event) == NULL)
    GST_EVENT_SRC (event) = gst_object_ref (GST_OBJECT (rpad));

  GST_DEBUG (GST_CAT_EVENT, "have event %d on pad %s:%s",
		  GST_EVENT_TYPE (event), GST_DEBUG_PAD_NAME (rpad));

  if (GST_RPAD_EVENTHANDLER (rpad))
    success = GST_RPAD_EVENTHANDLER (rpad) (GST_PAD_CAST (rpad), event);
  else {
    GST_DEBUG (GST_CAT_EVENT, "there's no event function for pad %s:%s", 
	       GST_DEBUG_PAD_NAME (rpad));
    gst_event_unref (event);
  }

  return success;
}

typedef struct 
{
  GstFormat	 src_format;
  gint64	 src_value;
  GstFormat	 *dest_format;
  gint64	 *dest_value;
} GstPadConvertData;

static gboolean
gst_pad_convert_dispatcher (GstPad *pad, GstPadConvertData *data)
{
  return gst_pad_convert (pad, data->src_format, data->src_value, 
		  	       data->dest_format, data->dest_value);
}

/**
 * gst_pad_convert_default:
 * @pad: a #GstPad to invoke the default converter on.
 * @src_format: the source #GstFormat.
 * @src_value: the source value.
 * @dest_format: a pointer to the destination #GstFormat.
 * @dest_value: a pointer to the destination value.
 *
 * Invokes the default converter on a pad. 
 * This will forward the call to the pad obtained 
 * using the internal link of
 * the element.
 *
 * Returns: TRUE if the conversion could be performed.
 */
gboolean
gst_pad_convert_default (GstPad *pad, 
	        	 GstFormat src_format,  gint64  src_value,
	        	 GstFormat *dest_format, gint64 *dest_value)
{
  GstPadConvertData data;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (dest_format, FALSE);
  g_return_val_if_fail (dest_value, FALSE);

  data.src_format = src_format;
  data.src_value = src_value;
  data.dest_format = dest_format;
  data.dest_value = dest_value;

  return gst_pad_dispatcher (pad, (GstPadDispatcherFunction) 
                                    gst_pad_convert_dispatcher, &data);
}

/**
 * gst_pad_convert:
 * @pad: a #GstPad to invoke the default converter on.
 * @src_format: the source #GstFormat.
 * @src_value: the source value.
 * @dest_format: a pointer to the destination #GstFormat.
 * @dest_value: a pointer to the destination value.
 *
 * Invokes a conversion on the pad.
 *
 * Returns: TRUE if the conversion could be performed.
 */
gboolean
gst_pad_convert (GstPad *pad, 
	         GstFormat src_format,  gint64  src_value,
	         GstFormat *dest_format, gint64 *dest_value)
{
  GstRealPad *rpad;
  
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (dest_format, FALSE);
  g_return_val_if_fail (dest_value, FALSE);

  if (src_format == *dest_format) {
    *dest_value = src_value; 
    return TRUE;
  }     

  rpad = GST_PAD_REALIZE (pad);

  if (GST_RPAD_CONVERTFUNC (rpad)) {
    return GST_RPAD_CONVERTFUNC (rpad) (GST_PAD_CAST (rpad), src_format, 
	                                src_value, dest_format, dest_value);
  }

  return FALSE;
}

typedef struct 
{
  GstQueryType 	  type;
  GstFormat	 *format;
  gint64	 *value;
} GstPadQueryData;

static gboolean
gst_pad_query_dispatcher (GstPad *pad, GstPadQueryData *data)
{
  return gst_pad_query (pad, data->type, data->format, data->value);
}

/**
 * gst_pad_query_default:
 * @pad: a #GstPad to invoke the default query on.
 * @type: the #GstQueryType of the query to perform.
 * @format: a pointer to the #GstFormat of the result.
 * @value: a pointer to the result.
 *
 * Invokes the default query function on a pad. 
 *
 * Returns: TRUE if the query could be performed.
 */
gboolean
gst_pad_query_default (GstPad *pad, GstQueryType type,
	               GstFormat *format,  gint64 *value)
{
  GstPadQueryData data;

  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (format, FALSE);
  g_return_val_if_fail (value, FALSE);

  data.type = type;
  data.format = format;
  data.value = value;

  return gst_pad_dispatcher (pad, (GstPadDispatcherFunction) 
                                   gst_pad_query_dispatcher, &data);
}

/**
 * gst_pad_query:
 * @pad: a #GstPad to invoke the default query on.
 * @type: the #GstQueryType of the query to perform.
 * @format: a pointer to the #GstFormat of the result.
 * @value: a pointer to the result.
 *
 * Queries a pad for one of the available properties.
 *
 * Returns: TRUE if the query could be performed.
 */
gboolean
gst_pad_query (GstPad *pad, GstQueryType type,
	       GstFormat *format, gint64 *value) 
{
  GstRealPad *rpad;
  
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);
  g_return_val_if_fail (format, FALSE);
  g_return_val_if_fail (value, FALSE);

  rpad = GST_PAD_REALIZE (pad);

  g_return_val_if_fail (rpad, FALSE);

  if (GST_RPAD_QUERYFUNC (rpad))
    return GST_RPAD_QUERYFUNC (rpad) (GST_PAD_CAST (pad), type, format, value);

  return FALSE;
}

static gboolean
gst_pad_get_formats_dispatcher (GstPad *pad, const GstFormat **data)
{
  *data = gst_pad_get_formats (pad);

  return TRUE;
}

/**
 * gst_pad_get_formats_default:
 * @pad: a #GstPad to query
 *
 * Invoke the default format dispatcher for the pad.
 *
 * Returns: An array of GstFormats ended with a 0 value.
 */
const GstFormat*
gst_pad_get_formats_default (GstPad *pad)
{
  GstFormat *result = NULL;

  gst_pad_dispatcher (pad, (GstPadDispatcherFunction) 
                      gst_pad_get_formats_dispatcher, &result);

  return result;
}

/**
 * gst_pad_get_formats:
 * @pad: a #GstPad to query
 *
 * Gets the list of supported formats from the pad.
 *
 * Returns: An array of GstFormats ended with a 0 value.
 */
const GstFormat*
gst_pad_get_formats (GstPad *pad)
{
  GstRealPad *rpad;
  
  g_return_val_if_fail (GST_IS_PAD (pad), FALSE);

  rpad = GST_PAD_REALIZE (pad);

  if (GST_RPAD_FORMATSFUNC (rpad))
    return GST_RPAD_FORMATSFUNC (rpad) (GST_PAD_CAST (pad));

  return NULL;
}