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Implement generic interface stuff, with per-instance support checking instead of per-class checking
Original commit message from CVS: Implement generic interface stuff, with per-instance support checking instead of per-class checking
This commit is contained in:
Ronald S. Bultje
parent
5a26d2f709
commit
5d76a2e9b3
5 changed files with 316 additions and 6 deletions
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@ -144,13 +144,76 @@ gst_element_implements_interface (GstElement *element,
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return FALSE;
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}
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We could use this in the GST_IS_... () macros. For example, the
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macro GST_IS_MIXER () would then look like this:
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Let's now add some functions so we can abuse this in case/check
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functions.
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GstInterface *
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gst_interface_cast (gpointer from,
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GType type)
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{
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GstInterface *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 (G_OBJECT (element),
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type, GstInterface))) {
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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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gboolean interface_is_implemented =
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gst_element_implements_interface (GST_ELEMENT (from),
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type);
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g_return_val_if_fail (interface_is_implemented == TRUE, NULL);
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}
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return iface;
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}
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gboolean
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gst_interface_check (gpointer from,
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GType type)
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{
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GstInterface *iface;
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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_CAST (from, type,
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GstInterface)) {
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return FALSE;
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}
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iface = G_TYPE_CHECK_INSTANCE_CAST (G_OBJECT (element),
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type, GstInterface);
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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),
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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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#define GST_INTERFACE_CHECK_INSTANCE_CAST(obj, type, cast_t) \
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((cast_t *) gst_interface_cast ((obj), (type))
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#define GST_INTERFACE_CHECK_INSTANCE_TYPE(obj, type) \
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(gst_interface_check ((obj), (type))
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We could use this in the GST_IS_... () macros. For example, the
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macros GST_IS_MIXER () and GST_MIXER () would then look like this:
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/* Note that this is a non-standard macro, and with a reason! */
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#define GST_MIXER(obj) \
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(GST_INTERFACE_CHECK_INSTANCE_CAST ((obj), \
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GST_TYPE_MIXER,
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GstMixer))
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#define GST_IS_MIXER(obj) \
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(G_TYPE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_MIXER) && \
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gst_element_implements_interface (GST_ELEMENT (obj), \
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GST_TYPE_MIXER))
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(GST_INTERFACE_CHECK_INSTANCE_TYPE ((obj), \
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GST_TYPE_MIXER))
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So the application would just tread it with the known macro, and
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everything would look extremely simple to the end user.
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@ -184,7 +247,8 @@ And alsa* would surely implement the same interface.
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/* This is confusing naming... (i.e. FIXME)
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* A channel is referred to both as the number of simultaneous
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* sounds the input can handle as well as the in-/output itself
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* sound streams the input can handle as well as the in-/output
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* itself
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*/
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#define GST_MIXER_CHANNEL_INPUT (1<<0)
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@ -107,6 +107,7 @@ libgstreamer_@GST_MAJORMINOR@_la_SOURCES = \
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gstformat.c \
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$(GST_INDEX_SRC) \
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gstinfo.c \
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gstinterface.c \
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gstmemchunk.c \
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gstpad.c \
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gstpipeline.c \
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@ -167,6 +168,7 @@ gst_headers = \
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gstformat.h \
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gstindex.h \
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gstinfo.h \
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gstinterface.h \
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gstlog.h \
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gstmacros.h \
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gstmemchunk.h \
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@ -55,6 +55,7 @@
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#include <gst/gstevent.h>
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#include <gst/gstclock.h>
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#include <gst/gstsystemclock.h>
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#include <gst/gstinterface.h>
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#include <gst/gstparse.h>
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#include <gst/gstregistry.h>
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170
gst/gstinterface.c
Normal file
170
gst/gstinterface.c
Normal file
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@ -0,0 +1,170 @@
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/* 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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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "gstinterface.h"
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#include "gstlog.h"
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static void gst_interface_class_init (GstInterfaceClass *ifklass);
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static gboolean gst_interface_supported_default (GstInterface *iface);
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GType
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gst_interface_get_type (void)
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{
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static GType gst_interface_type = 0;
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if (!gst_interface_type) {
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static const GTypeInfo gst_interface_info = {
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sizeof (GstInterfaceClass),
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(GBaseInitFunc) gst_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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gst_interface_type = g_type_register_static (G_TYPE_INTERFACE,
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"GstInterface",
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&gst_interface_info, 0);
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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_interface_class_init (GstInterfaceClass *klass)
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{
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klass->supported = gst_interface_supported_default;
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}
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static gboolean
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gst_interface_supported_default (GstInterface *interface)
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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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gboolean
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gst_element_implements_interface (GstElement *element,
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GType iface_type)
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{
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if (G_TYPE_CHECK_INSTANCE_TYPE (G_OBJECT (element),
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iface_type)) {
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GstInterface *iface;
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GstInterfaceClass *ifclass;
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iface = G_TYPE_CHECK_INSTANCE_CAST (G_OBJECT (element),
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iface_type, GstInterface);
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ifclass = GST_INTERFACE_GET_CLASS (iface);
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if (ifclass->supported != NULL &&
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ifclass->supported (iface) == 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_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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GstInterface *
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gst_interface_cast (gpointer from,
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GType iface_type)
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{
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GstInterface *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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GstInterface))) {
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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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gboolean interface_is_implemented =
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gst_element_implements_interface (GST_ELEMENT (from), iface_type);
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g_return_val_if_fail (interface_is_implemented == TRUE, NULL);
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}
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return iface;
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}
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/**
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* gst_interface_cast:
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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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gboolean
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gst_interface_check (gpointer from,
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GType type)
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{
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GstInterface *iface;
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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_CAST (from, type, GstInterface)) {
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return FALSE;
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}
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iface = G_TYPE_CHECK_INSTANCE_CAST (from, type, GstInterface);
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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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73
gst/gstinterface.h
Normal file
73
gst/gstinterface.h
Normal file
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@ -0,0 +1,73 @@
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/* GStreamer
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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.h: Declarations of interface stuff
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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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#ifndef __GST_INTERFACE_H__
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#define __GST_INTERFACE_H__
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#include <gst/gstelement.h>
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G_BEGIN_DECLS
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#define GST_TYPE_INTERFACE \
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(gst_interface_get_type ())
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#define GST_INTERFACE(obj) \
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(GST_INTERFACE_CHECK_INSTANCE_CAST ((obj), GST_TYPE_INTERFACE, GstInterface))
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#define GST_INTERFACE_CLASS(klass) \
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(G_TYPE_CHECK_CLASS_CAST ((klass), GST_TYPE_INTERFACE, GstInterfaceClass))
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#define GST_IS_INTERFACE(obj) \
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(GST_INTERFACE_CHECK_INSTANCE_TYPE ((obj), GST_TYPE_INTERFACE))
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#define GST_IS_INTERFACE_CLASS(klass) \
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(G_TYPE_CHECK_CLASS_TYPE ((klass), GST_TYPE_INTERFACE))
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#define GST_INTERFACE_GET_CLASS(inst) \
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(G_TYPE_INSTANCE_GET_INTERFACE ((inst), GST_TYPE_INTERFACE, GstInterfaceClass))
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typedef struct _GstInterface GstInterface;
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/* This small extra virtual function is here to provide an
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* interface functionality on a per-instance basis rather
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* than a per-class basis, which is the case for glib.
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*/
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typedef struct _GstInterfaceClass {
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GTypeInterface parent;
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/* virtual functions */
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gboolean (* supported) (GstInterface *iface);
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} GstInterfaceClass;
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#define GST_INTERFACE_CHECK_INSTANCE_CAST(obj, type, cast_t) \
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((cast_t *) gst_interface_cast ((obj), (type)))
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#define GST_INTERFACE_CHECK_INSTANCE_TYPE(obj, type) \
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(gst_interface_check ((obj), (type)))
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GType gst_interface_get_type (void);
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/* wrapper functions to check for functionality implementation */
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gboolean gst_element_implements_interface(GstElement *element,
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GType iface_type);
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GstInterface * gst_interface_cast (gpointer from,
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GType type);
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gboolean gst_interface_check (gpointer from,
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GType type);
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G_END_DECLS
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#endif /* __GST_INTERFACE_H__ */
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