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