/* 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: 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;

}