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/* GStreamer
* Copyright (C) 2011 Wim Taymans <wim.taymans@gmail.com>
*
* gstmeta.c: metadata operations
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* 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., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstmeta
* @title: GstMeta
* @short_description: Buffer metadata
*
* 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"
#include "gstbuffer.h"
#include "gstmeta.h"
#include "gstinfo.h"
#include "gstutils.h"
static GHashTable *metainfo = NULL;
static GRWLock lock;
GQuark _gst_meta_transform_copy;
GQuark _gst_meta_tag_memory;
void
_priv_gst_meta_initialize (void)
{
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 ("gst-copy");
_gst_meta_tag_memory = g_quark_from_static_string ("memory");
}
/**
* gst_meta_api_type_register:
* @api: an API to register
* @tags: (array zero-terminated=1): tags for @api
*
* Register and return a GType for the @api and associate it with
* @tags.
*
* Returns: a unique GType for @api.
*/
GType
gst_meta_api_type_register (const gchar * api, const gchar ** tags)
{
GType type;
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++) {
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_has_tag:
* @api: an API
* @tag: the tag to check
*
* Check if @api was registered with @tag.
*
* Returns: %TRUE if @api was registered with @tag.
*/
gboolean
gst_meta_api_type_has_tag (GType api, GQuark tag)
{
g_return_val_if_fail (api != 0, FALSE);
g_return_val_if_fail (tag != 0, FALSE);
return g_type_get_qdata (api, tag) != NULL;
}
/**
* 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: (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) (nullable): a #GstMetaInfo that can be used to
* access metadata.
*/
const GstMetaInfo *
gst_meta_register (GType api, const gchar * impl, gsize size,
GstMetaInitFunction init_func, GstMetaFreeFunction free_func,
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 = type;
info->size = size;
info->init_func = init_func;
info->free_func = free_func;
info->transform_func = transform_func;
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);
g_rw_lock_writer_unlock (&lock);
return info;
}
/**
* gst_meta_get_info:
* @impl: the name
*
* Lookup a previously registered meta info structure by its implementation name
* @impl.
*
* Returns: (transfer none) (nullable): a #GstMetaInfo with @impl, or
* %NULL when no such metainfo exists.
*/
const GstMetaInfo *
gst_meta_get_info (const gchar * impl)
{
GstMetaInfo *info;
g_return_val_if_fail (impl != NULL, NULL);
g_rw_lock_reader_lock (&lock);
info = g_hash_table_lookup (metainfo, impl);
g_rw_lock_reader_unlock (&lock);
return info;
}
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