*
* 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.
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstmeta
+ * @title: GstMeta
* @short_description: Buffer metadata
*
- * Last reviewed on December 17th, 2009 (0.10.26)
+ * The #GstMeta structure should be included as the first member of a #GstBuffer
+ * metadata structure. The structure defines the API of the metadata and should
+ * be accessible to all elements using the metadata.
+ *
+ * A metadata API is registered with gst_meta_api_type_register() which takes a
+ * name for the metadata API and some tags associated with the metadata.
+ * With gst_meta_api_type_has_tag() one can check if a certain metadata API
+ * contains a given tag.
+ *
+ * Multiple implementations of a metadata API can be registered.
+ * To implement a metadata API, gst_meta_register() should be used. This
+ * function takes all parameters needed to create, free and transform metadata
+ * along with the size of the metadata. The function returns a #GstMetaInfo
+ * structure that contains the information for the implementation of the API.
+ *
+ * A specific implementation can be retrieved by name with gst_meta_get_info().
+ *
+ * See #GstBuffer for how the metadata can be added, retrieved and removed from
+ * buffers.
*/
#include "gst_private.h"
g_rw_lock_init (&lock);
metainfo = g_hash_table_new (g_str_hash, g_str_equal);
- _gst_meta_transform_copy = g_quark_from_static_string ("copy");
+ _gst_meta_transform_copy = g_quark_from_static_string ("gst-copy");
_gst_meta_tag_memory = g_quark_from_static_string ("memory");
}
/**
* gst_meta_api_type_register:
* @api: an API to register
- * @tags: tags for @api
+ * @tags: (array zero-terminated=1): tags for @api
*
* Register and return a GType for the @api and associate it with
* @tags.
g_return_val_if_fail (api != NULL, 0);
g_return_val_if_fail (tags != NULL, 0);
+ GST_CAT_DEBUG (GST_CAT_META, "register API \"%s\"", api);
type = g_pointer_type_register_static (api);
if (type != 0) {
gint i;
- for (i = 0; tags[i]; i++)
+ for (i = 0; tags[i]; i++) {
+ GST_CAT_DEBUG (GST_CAT_META, " adding tag \"%s\"", tags[i]);
g_type_set_qdata (type, g_quark_from_string (tags[i]),
GINT_TO_POINTER (TRUE));
+ }
}
+
+ g_type_set_qdata (type, g_quark_from_string ("tags"),
+ g_strdupv ((gchar **) tags));
+
return type;
}
}
/**
+ * gst_meta_api_type_get_tags:
+ * @api: an API
+ *
+ * Returns: (transfer none) (array zero-terminated=1) (element-type utf8): an array of tags as strings.
+ *
+ * Since: 1.2
+ */
+const gchar *const *
+gst_meta_api_type_get_tags (GType api)
+{
+ const gchar **tags;
+ g_return_val_if_fail (api != 0, FALSE);
+
+ tags = g_type_get_qdata (api, g_quark_from_string ("tags"));
+
+ if (!tags[0])
+ return NULL;
+
+ return (const gchar * const *) tags;
+}
+
+/**
* gst_meta_register:
* @api: the type of the #GstMeta API
* @impl: the name of the #GstMeta implementation
* @size: the size of the #GstMeta structure
- * @init_func: a #GstMetaInitFunction
- * @free_func: a #GstMetaFreeFunction
- * @transform_func: a #GstMetaTransformFunction
- * @tags: a NULL terminated array of strings describing what the metadata
- * contains info about.
+ * @init_func: (scope async): a #GstMetaInitFunction
+ * @free_func: (scope async): a #GstMetaFreeFunction
+ * @transform_func: (scope async): a #GstMetaTransformFunction
*
* Register a new #GstMeta implementation.
*
* The same @info can be retrieved later with gst_meta_get_info() by using
* @impl as the key.
*
- * Returns: (transfer none): a #GstMetaInfo that can be used to access metadata.
+ * Returns: (transfer none) (nullable): a #GstMetaInfo that can be used to
+ * access metadata.
*/
const GstMetaInfo *
GstMetaTransformFunction transform_func)
{
GstMetaInfo *info;
+ GType type;
g_return_val_if_fail (api != 0, NULL);
g_return_val_if_fail (impl != NULL, NULL);
g_return_val_if_fail (size != 0, NULL);
+ if (init_func == NULL)
+ g_critical ("Registering meta implementation '%s' without init function",
+ impl);
+
+ /* first try to register the implementation name. It's possible
+ * that this fails because it was already registered. Don't warn,
+ * glib did this for us already. */
+ type = g_pointer_type_register_static (impl);
+ if (type == 0)
+ return NULL;
+
info = g_slice_new (GstMetaInfo);
info->api = api;
- info->type = g_pointer_type_register_static (impl);
+ info->type = type;
info->size = size;
info->init_func = init_func;
info->free_func = free_func;
info->transform_func = transform_func;
- GST_DEBUG ("register \"%s\" implementing \"%s\" of size %" G_GSIZE_FORMAT,
- api, impl, size);
+ GST_CAT_DEBUG (GST_CAT_META,
+ "register \"%s\" implementing \"%s\" of size %" G_GSIZE_FORMAT, impl,
+ g_type_name (api), size);
g_rw_lock_writer_lock (&lock);
g_hash_table_insert (metainfo, (gpointer) impl, (gpointer) info);
* Lookup a previously registered meta info structure by its implementation name
* @impl.
*
- * Returns: (transfer none): a #GstMetaInfo with @impl, or #NULL when no such
- * metainfo exists.
+ * Returns: (transfer none) (nullable): a #GstMetaInfo with @impl, or
+ * %NULL when no such metainfo exists.
*/
const GstMetaInfo *
gst_meta_get_info (const gchar * impl)