1 /* GStreamer

     2  *

     3  * Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>

     4  *                    2000 Wim Taymans <wtay@chello.be>

     5  *

     6  * gstinterface.c: Interface functions

     7  *

     8  * This library is free software; you can redistribute it and/or

     9  * modify it under the terms of the GNU Library General Public

    10  * License as published by the Free Software Foundation; either

    11  * version 2 of the License, or (at your option) any later version.

    12  *

    13  * This library is distributed in the hope that it will be useful,

    14  * but WITHOUT ANY WARRANTY; without even the implied warranty of

    15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    16  * Library General Public License for more details.

    17  *

    18  * You should have received a copy of the GNU Library General Public

    19  * License along with this library; if not, write to the

    20  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,

    21  * Boston, MA 02111-1307, USA.

    22  */

    23 

    24 /**

    25  * SECTION:gstimplementsinterface

    26  * @short_description: Core interface implemented by #GstElement instances that

    27  * allows runtime querying of interface availabillity

    28  * @see_also: #GstElement

    29  *

    30  * Provides interface functionality on per instance basis and not per class

    31  * basis, which is the case for gobject.

    32  */

    33 

    34 #ifdef HAVE_CONFIG_H

    35 #include "config.h"

    36 #endif

    37 

    38 #include "gst_private.h"

    39 #include "gstinterface.h"

    40 

    41 static void

    42 gst_implements_interface_class_init (GstImplementsInterfaceClass * ifklass);

    43 static gboolean

    44 gst_implements_interface_supported_default (GstImplementsInterface * iface,

    45     GType iface_type);

    46 #ifdef __SYMBIAN32__

    47 EXPORT_C

    48 #endif

    49 

    50 

    51 GType

    52 gst_implements_interface_get_type (void)

    53 {

    54   static GType gst_interface_type = 0;

    55 

    56   if (!gst_interface_type) {

    57     static const GTypeInfo gst_interface_info = {

    58       sizeof (GstImplementsInterfaceClass),

    59       (GBaseInitFunc) gst_implements_interface_class_init,

    60       NULL,

    61       NULL,

    62       NULL,

    63       NULL,

    64       0,

    65       0,

    66       NULL,

    67       NULL

    68     };

    69 

    70     gst_interface_type = g_type_register_static (G_TYPE_INTERFACE,

    71         "GstImplementsInterface", &gst_interface_info, 0);

    72 

    73     g_type_interface_add_prerequisite (gst_interface_type, GST_TYPE_ELEMENT);

    74   }

    75 

    76   return gst_interface_type;

    77 }

    78 

    79 static void

    80 gst_implements_interface_class_init (GstImplementsInterfaceClass * klass)

    81 {

    82   klass->supported = gst_implements_interface_supported_default;

    83 }

    84 

    85 static gboolean

    86 gst_implements_interface_supported_default (GstImplementsInterface * interface,

    87     GType iface_type)

    88 {

    89   /* Well, if someone didn't set the virtual function,

    90    * then something is clearly wrong. So big no-no here */

    91 

    92   return FALSE;

    93 }

    94 

    95 /**

    96  * gst_element_implements_interface:

    97  * @element: #GstElement to check for the implementation of the interface

    98  * @iface_type: (final) type of the interface which we want to be implemented

    99  *

   100  * Test whether the given element implements a certain interface of type

   101  * iface_type, and test whether it is supported for this specific instance.

   102  *

   103  * Returns: whether or not the element implements the interface.

   104  */

   105 #ifdef __SYMBIAN32__

   106 EXPORT_C

   107 #endif

   108 

   109 

   110 gboolean

   111 gst_element_implements_interface (GstElement * element, GType iface_type)

   112 {

   113   g_return_val_if_fail (GST_IS_ELEMENT (element), FALSE);

   114 

   115   if (G_TYPE_CHECK_INSTANCE_TYPE (G_OBJECT (element), iface_type)) {

   116     GstImplementsInterface *iface;

   117     GstImplementsInterfaceClass *ifclass;

   118 

   119     iface = G_TYPE_CHECK_INSTANCE_CAST (G_OBJECT (element),

   120         iface_type, GstImplementsInterface);

   121     ifclass = GST_IMPLEMENTS_INTERFACE_GET_CLASS (iface);

   122 

   123     /* element implements iface_type but not GstImplementsInterface, so

   124      * just assume the other interface is implemented unconditionally */

   125     if (ifclass == NULL)

   126       return TRUE;

   127 

   128     if (ifclass->supported != NULL &&

   129         ifclass->supported (iface, iface_type) == TRUE) {

   130       return TRUE;

   131     }

   132   }

   133 

   134   return FALSE;

   135 }

   136 

   137 /**

   138  * gst_implements_interface_cast:

   139  * @from: the object (any sort) from which to cast to the interface

   140  * @type: the interface type to cast to

   141  *

   142  * cast a given object to an interface type, and check whether this

   143  * interface is supported for this specific instance.

   144  *

   145  * Returns: a gpointer to the interface type

   146  */

   147 #ifdef __SYMBIAN32__

   148 EXPORT_C

   149 #endif

   150 

   151 

   152 gpointer

   153 gst_implements_interface_cast (gpointer from, GType iface_type)

   154 {

   155   GstImplementsInterface *iface;

   156 

   157   /* check cast, give warning+fail if it's invalid */

   158   if (!(iface = G_TYPE_CHECK_INSTANCE_CAST (from, iface_type,

   159               GstImplementsInterface))) {

   160     return NULL;

   161   }

   162 

   163   /* if we're an element, take care that this interface

   164    * is actually implemented */

   165   if (GST_IS_ELEMENT (from)) {

   166     g_return_val_if_fail (gst_element_implements_interface (GST_ELEMENT (from),

   167             iface_type), NULL);

   168   }

   169 

   170   return iface;

   171 }

   172 

   173 /**

   174  * gst_implements_interface_check:

   175  * @from: the object (any sort) from which to check from for the interface

   176  * @type: the interface type to check for

   177  *

   178  * check a given object for an interface implementation, and check

   179  * whether this interface is supported for this specific instance.

   180  *

   181  * Returns: whether or not the object implements the given interface

   182  */

   183 #ifdef __SYMBIAN32__

   184 EXPORT_C

   185 #endif

   186 

   187 

   188 gboolean

   189 gst_implements_interface_check (gpointer from, GType type)

   190 {

   191   GstImplementsInterface *iface;

   192 

   193   /* check cast, return FALSE if it fails, don't give a warning... */

   194   if (!G_TYPE_CHECK_INSTANCE_TYPE (from, type)) {

   195     return FALSE;

   196   }

   197 

   198   iface = G_TYPE_CHECK_INSTANCE_CAST (from, type, GstImplementsInterface);

   199 

   200   /* now, if we're an element (or derivative), is this thing

   201    * actually implemented for real? */

   202   if (GST_IS_ELEMENT (from)) {

   203     if (!gst_element_implements_interface (GST_ELEMENT (from), type)) {

   204       return FALSE;

   205     }

   206   }

   207 

   208   return TRUE;

   209 }