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/* GStreamer
*
* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
* 2000 Wim Taymans <wtay@chello.be>
*
* gstinterface.c: Interface functions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
/**
* SECTION:gstimplementsinterface
* @short_description: Core interface implemented by #GstElement instances that
* allows runtime querying of interface availabillity
* @see_also: #GstElement
*
* Provides interface functionality on per instance basis and not per class
* basis, which is the case for gobject.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gst_private.h"
#include "gstinterface.h"
static void
gst_implements_interface_class_init (GstImplementsInterfaceClass * ifklass);
static gboolean
gst_implements_interface_supported_default (GstImplementsInterface * iface,
GType iface_type);
GType
gst_implements_interface_get_type (void)
{
static volatile gsize gst_interface_type = 0;
if (g_once_init_enter (&gst_interface_type)) {
GType _type;
static const GTypeInfo gst_interface_info = {
sizeof (GstImplementsInterfaceClass),
(GBaseInitFunc) gst_implements_interface_class_init,
NULL,
NULL,
NULL,
NULL,
0,
0,
NULL,
NULL
};
_type = g_type_register_static (G_TYPE_INTERFACE,
"GstImplementsInterface", &gst_interface_info, 0);
g_type_interface_add_prerequisite (_type, GST_TYPE_ELEMENT);
g_once_init_leave (&gst_interface_type, _type);
}
return gst_interface_type;
}
static void
gst_implements_interface_class_init (GstImplementsInterfaceClass * klass)
{
klass->supported = gst_implements_interface_supported_default;
}
static gboolean
gst_implements_interface_supported_default (GstImplementsInterface * interface,
GType iface_type)
{
/* Well, if someone didn't set the virtual function,
* then something is clearly wrong. So big no-no here */
return FALSE;
}
/**
* gst_element_implements_interface:
* @element: #GstElement to check for the implementation of the interface
* @iface_type: (final) type of the interface which we want to be implemented
*
* Test whether the given element implements a certain interface of type
* iface_type, and test whether it is supported for this specific instance.
*
* Returns: whether or not the element implements the interface.
*/
gboolean
gst_element_implements_interface (GstElement * element, GType iface_type)
{
g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);
if (G_TYPE_CHECK_INSTANCE_TYPE (G_OBJECT (element), iface_type)) {
GstImplementsInterface *iface;
GstImplementsInterfaceClass *ifclass;
iface = G_TYPE_CHECK_INSTANCE_CAST (G_OBJECT (element),
iface_type, GstImplementsInterface);
ifclass = GST_IMPLEMENTS_INTERFACE_GET_CLASS (iface);
/* element implements iface_type but not GstImplementsInterface, so
* just assume the other interface is implemented unconditionally */
if (ifclass == NULL)
return TRUE;
if (ifclass->supported != NULL &&
ifclass->supported (iface, iface_type) == TRUE) {
return TRUE;
}
}
return FALSE;
}
/**
* gst_implements_interface_cast:
* @from: the object (any sort) from which to cast to the interface
* @type: the interface type to cast to
*
* cast a given object to an interface type, and check whether this
* interface is supported for this specific instance.
*
* Returns: a gpointer to the interface type
*/
gpointer
gst_implements_interface_cast (gpointer from, GType iface_type)
{
GstImplementsInterface *iface;
/* check cast, give warning+fail if it's invalid */
if (!(iface = G_TYPE_CHECK_INSTANCE_CAST (from, iface_type,
GstImplementsInterface))) {
return NULL;
}
/* if we're an element, take care that this interface
* is actually implemented */
if (GST_IS_ELEMENT (from)) {
g_return_val_if_fail (gst_element_implements_interface (GST_ELEMENT (from),
iface_type), NULL);
}
return iface;
}
/**
* gst_implements_interface_check:
* @from: the object (any sort) from which to check from for the interface
* @type: the interface type to check for
*
* check a given object for an interface implementation, and check
* whether this interface is supported for this specific instance.
*
* Returns: whether or not the object implements the given interface
*/
gboolean
gst_implements_interface_check (gpointer from, GType type)
{
/* check cast, return FALSE if it fails, don't give a warning... */
if (!G_TYPE_CHECK_INSTANCE_TYPE (from, type)) {
return FALSE;
}
/* now, if we're an element (or derivative), is this thing
* actually implemented for real? */
if (GST_IS_ELEMENT (from)) {
if (!gst_element_implements_interface (GST_ELEMENT (from), type)) {
return FALSE;
}
}
return TRUE;
}
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