2 * Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
4 * gsttypefindfactory.c: typefinding subsystem
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
22 * SECTION:gsttypefindfactory
23 * @short_description: Information about registered typefind functions
25 * These functions allow querying informations about registered typefind
26 * functions. How to create and register these functions is described in
27 * the section <link linkend="gstreamer-Writing-typefind-functions">
28 * "Writing typefind functions"</link>.
31 * <title>how to write a simple typefinder</title>
40 * my_peek (gpointer data, gint64 offset, guint size)
42 * MyTypeFind *find = (MyTypeFind *) data;
43 * if (offset >= 0 && offset + size <= find->size) {
44 * return find->data + offset;
49 * my_suggest (gpointer data, guint probability, GstCaps *caps)
51 * MyTypeFind *find = (MyTypeFind *) data;
52 * if (probability > find->probability) {
53 * find->probability = probability;
54 * gst_caps_replace (&find->caps, caps);
58 * find_type (guint8 *data, guint size)
60 * GList *walk, *type_list;
61 * MyTypeFind find = {data, size, 0, NULL};
62 * GstTypeFind gst_find = {my_peek, my_suggest, &find, };
64 * walk = type_list = gst_type_find_factory_get_list ();
66 * GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (walk->data);
67 * walk = g_list_next (walk)
68 * gst_type_find_factory_call_function (factory, &gst_find);
70 * g_list_free (type_list);
76 * The above example shows how to write a very simple typefinder that identifies
77 * the given data. You can get quite a bit more complicated than that though.
80 #include "gst_private.h"
82 #include "gsttypefind.h"
83 #include "gsttypefindfactory.h"
84 #include "gstregistry.h"
86 GST_DEBUG_CATEGORY (gst_type_find_debug);
87 #define GST_CAT_DEFAULT gst_type_find_debug
89 static void gst_type_find_factory_class_init (gpointer g_class,
91 static void gst_type_find_factory_init (GTypeInstance * instance,
93 static void gst_type_find_factory_dispose (GObject * object);
95 static void gst_type_find_load_plugin (GstTypeFind * find, gpointer data);
97 static GstPluginFeatureClass *parent_class = NULL;
100 gst_type_find_factory_get_type (void)
102 static GType typefind_type = 0;
104 if (!typefind_type) {
105 static const GTypeInfo typefind_info = {
106 sizeof (GstTypeFindFactoryClass),
109 gst_type_find_factory_class_init,
112 sizeof (GstTypeFindFactory),
114 gst_type_find_factory_init,
118 typefind_type = g_type_register_static (GST_TYPE_PLUGIN_FEATURE,
119 "GstTypeFindFactory", &typefind_info, 0);
120 GST_DEBUG_CATEGORY_INIT (gst_type_find_debug, "GST_TYPEFIND",
121 GST_DEBUG_FG_GREEN, "typefinding subsystem");
124 return typefind_type;
127 gst_type_find_factory_class_init (gpointer g_class, gpointer class_data)
129 GObjectClass *object_class = G_OBJECT_CLASS (g_class);
131 parent_class = g_type_class_peek_parent (g_class);
133 object_class->dispose = gst_type_find_factory_dispose;
136 gst_type_find_factory_init (GTypeInstance * instance, gpointer g_class)
138 GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (instance);
140 factory->user_data = factory;
141 factory->function = gst_type_find_load_plugin;
144 gst_type_find_factory_dispose (GObject * object)
146 GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (object);
149 gst_caps_unref (factory->caps);
150 factory->caps = NULL;
152 if (factory->extensions) {
153 g_strfreev (factory->extensions);
154 factory->extensions = NULL;
158 gst_type_find_load_plugin (GstTypeFind * find, gpointer data)
160 GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (data);
162 GST_DEBUG_OBJECT (factory, "need to load typefind function %s",
163 GST_PLUGIN_FEATURE_NAME (factory));
166 GST_TYPE_FIND_FACTORY (gst_plugin_feature_load (GST_PLUGIN_FEATURE
169 if (factory->function == gst_type_find_load_plugin) {
170 /* looks like we didn't get a real typefind function */
171 g_warning ("could not load valid typefind function for feature '%s'\n",
172 GST_PLUGIN_FEATURE_NAME (factory));
174 g_assert (factory->function);
175 gst_type_find_factory_call_function (factory, find);
181 * gst_type_find_factory_get_list:
183 * Gets the list of all registered typefind factories. You must free the
184 * list using g_list_free.
186 * Returns: the list of all registered typefind factories
189 gst_type_find_factory_get_list (void)
191 return gst_registry_get_feature_list (gst_registry_get_default (),
192 GST_TYPE_TYPE_FIND_FACTORY);
196 * gst_type_find_factory_get_caps:
197 * @factory: a factory
199 * Gets the caps associated with a typefind factory.
201 * Returns: the #GstCaps associated with this factory
204 gst_type_find_factory_get_caps (const GstTypeFindFactory * factory)
206 g_return_val_if_fail (GST_IS_TYPE_FIND_FACTORY (factory), NULL);
208 return factory->caps;
212 * gst_type_find_factory_get_extensions:
213 * @factory: a factory
215 * Gets the extensions associated with a typefind factory. The returned
216 * array should not be changed. If you need to change stuff in it, you should
217 * copy it using g_stdupv(). This function may return NULL to indicate
220 * Returns: a NULL-terminated array of extensions associated with this factory
223 gst_type_find_factory_get_extensions (const GstTypeFindFactory * factory)
225 g_return_val_if_fail (GST_IS_TYPE_FIND_FACTORY (factory), NULL);
227 return factory->extensions;
231 * gst_type_find_factory_call_function:
232 * @factory: a factory
233 * @find: a properly setup #GstTypeFind entry. The get_data and suggest_type
234 * members must be set.
236 * Calls the typefinding function associated with this factory.
239 gst_type_find_factory_call_function (const GstTypeFindFactory * factory,
242 g_return_if_fail (GST_IS_TYPE_FIND_FACTORY (factory));
243 g_return_if_fail (find != NULL);
244 g_return_if_fail (find->peek != NULL);
245 g_return_if_fail (find->suggest != NULL);
247 /* should never happen */
248 g_assert (factory->function != NULL);
250 factory->function (find, factory->user_data);