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277 lines
7.3 KiB
C
277 lines
7.3 KiB
C
/* GStreamer
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* Copyright (C) 2011 Wim Taymans <wim.taymans@gmail.com>
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*
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* gstmeta.c: metadata operations
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
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* Boston, MA 02110-1301, USA.
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*/
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/**
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* SECTION:gstmeta
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* @title: GstMeta
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* @short_description: Buffer metadata
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*
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* The #GstMeta structure should be included as the first member of a #GstBuffer
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* metadata structure. The structure defines the API of the metadata and should
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* be accessible to all elements using the metadata.
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*
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* A metadata API is registered with gst_meta_api_type_register() which takes a
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* name for the metadata API and some tags associated with the metadata.
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* With gst_meta_api_type_has_tag() one can check if a certain metadata API
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* contains a given tag.
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*
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* Multiple implementations of a metadata API can be registered.
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* To implement a metadata API, gst_meta_register() should be used. This
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* function takes all parameters needed to create, free and transform metadata
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* along with the size of the metadata. The function returns a #GstMetaInfo
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* structure that contains the information for the implementation of the API.
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*
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* A specific implementation can be retrieved by name with gst_meta_get_info().
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*
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* See #GstBuffer for how the metadata can be added, retrieved and removed from
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* buffers.
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*/
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#include "gst_private.h"
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#include "gstbuffer.h"
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#include "gstmeta.h"
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#include "gstinfo.h"
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#include "gstutils.h"
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#include "gstquark.h"
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static GHashTable *metainfo = NULL;
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static GRWLock lock;
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GQuark _gst_meta_transform_copy;
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GQuark _gst_meta_tag_memory;
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void
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_priv_gst_meta_initialize (void)
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{
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g_rw_lock_init (&lock);
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metainfo = g_hash_table_new (g_str_hash, g_str_equal);
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_gst_meta_transform_copy = g_quark_from_static_string ("gst-copy");
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_gst_meta_tag_memory = g_quark_from_static_string ("memory");
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}
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/**
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* gst_meta_api_type_register:
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* @api: an API to register
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* @tags: (array zero-terminated=1): tags for @api
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*
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* Register and return a GType for the @api and associate it with
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* @tags.
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*
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* Returns: a unique GType for @api.
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*/
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GType
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gst_meta_api_type_register (const gchar * api, const gchar ** tags)
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{
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GType type;
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g_return_val_if_fail (api != NULL, 0);
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g_return_val_if_fail (tags != NULL, 0);
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GST_CAT_DEBUG (GST_CAT_META, "register API \"%s\"", api);
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type = g_pointer_type_register_static (api);
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if (type != 0) {
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gint i;
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for (i = 0; tags[i]; i++) {
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GST_CAT_DEBUG (GST_CAT_META, " adding tag \"%s\"", tags[i]);
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g_type_set_qdata (type, g_quark_from_string (tags[i]),
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GINT_TO_POINTER (TRUE));
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}
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}
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g_type_set_qdata (type, GST_QUARK (TAGS), g_strdupv ((gchar **) tags));
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return type;
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}
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/**
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* gst_meta_api_type_has_tag:
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* @api: an API
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* @tag: the tag to check
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*
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* Check if @api was registered with @tag.
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*
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* Returns: %TRUE if @api was registered with @tag.
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*/
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gboolean
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gst_meta_api_type_has_tag (GType api, GQuark tag)
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{
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g_return_val_if_fail (api != 0, FALSE);
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g_return_val_if_fail (tag != 0, FALSE);
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return g_type_get_qdata (api, tag) != NULL;
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}
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/**
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* gst_meta_api_type_get_tags:
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* @api: an API
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*
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* Returns: (transfer none) (array zero-terminated=1) (element-type utf8): an array of tags as strings.
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*
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* Since: 1.2
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*/
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const gchar *const *
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gst_meta_api_type_get_tags (GType api)
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{
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const gchar **tags;
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g_return_val_if_fail (api != 0, FALSE);
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tags = g_type_get_qdata (api, GST_QUARK (TAGS));
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if (!tags[0])
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return NULL;
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return (const gchar * const *) tags;
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}
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/**
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* gst_meta_register:
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* @api: the type of the #GstMeta API
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* @impl: the name of the #GstMeta implementation
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* @size: the size of the #GstMeta structure
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* @init_func: (scope async): a #GstMetaInitFunction
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* @free_func: (scope async): a #GstMetaFreeFunction
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* @transform_func: (scope async): a #GstMetaTransformFunction
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*
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* Register a new #GstMeta implementation.
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*
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* The same @info can be retrieved later with gst_meta_get_info() by using
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* @impl as the key.
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*
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* Returns: (transfer none) (nullable): a #GstMetaInfo that can be used to
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* access metadata.
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*/
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const GstMetaInfo *
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gst_meta_register (GType api, const gchar * impl, gsize size,
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GstMetaInitFunction init_func, GstMetaFreeFunction free_func,
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GstMetaTransformFunction transform_func)
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{
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GstMetaInfo *info;
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GType type;
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g_return_val_if_fail (api != 0, NULL);
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g_return_val_if_fail (impl != NULL, NULL);
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g_return_val_if_fail (size != 0, NULL);
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if (init_func == NULL)
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g_critical ("Registering meta implementation '%s' without init function",
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impl);
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/* first try to register the implementation name. It's possible
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* that this fails because it was already registered. Don't warn,
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* glib did this for us already. */
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type = g_pointer_type_register_static (impl);
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if (type == 0)
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return NULL;
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info = g_slice_new (GstMetaInfo);
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info->api = api;
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info->type = type;
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info->size = size;
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info->init_func = init_func;
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info->free_func = free_func;
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info->transform_func = transform_func;
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GST_CAT_DEBUG (GST_CAT_META,
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"register \"%s\" implementing \"%s\" of size %" G_GSIZE_FORMAT, impl,
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g_type_name (api), size);
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g_rw_lock_writer_lock (&lock);
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g_hash_table_insert (metainfo, (gpointer) impl, (gpointer) info);
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g_rw_lock_writer_unlock (&lock);
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return info;
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}
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/**
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* gst_meta_get_info:
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* @impl: the name
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*
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* Lookup a previously registered meta info structure by its implementation name
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* @impl.
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*
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* Returns: (transfer none) (nullable): a #GstMetaInfo with @impl, or
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* %NULL when no such metainfo exists.
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*/
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const GstMetaInfo *
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gst_meta_get_info (const gchar * impl)
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{
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GstMetaInfo *info;
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g_return_val_if_fail (impl != NULL, NULL);
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g_rw_lock_reader_lock (&lock);
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info = g_hash_table_lookup (metainfo, impl);
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g_rw_lock_reader_unlock (&lock);
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return info;
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}
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/**
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* gst_meta_get_seqnum:
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* @meta: a #GstMeta
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*
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* Gets seqnum for this meta.
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*
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* Since: 1.16
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*/
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guint64
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gst_meta_get_seqnum (const GstMeta * meta)
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{
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GstMetaItem *meta_item;
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guint8 *p;
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g_return_val_if_fail (meta != NULL, 0);
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p = (guint8 *) meta;
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p -= G_STRUCT_OFFSET (GstMetaItem, meta);
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meta_item = (GstMetaItem *) p;
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return meta_item->seq_num;
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}
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/**
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* gst_meta_compare_seqnum:
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* @meta1: a #GstMeta
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* @meta2: a #GstMeta
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*
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* Meta sequence number compare function. Can be used as #GCompareFunc
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* or a #GCompareDataFunc.
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*
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* Returns: a negative number if @meta1 comes before @meta2, 0 if both metas
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* have an equal sequence number, or a positive integer if @meta1 comes
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* after @meta2.
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*
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* Since: 1.16
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*/
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gint
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gst_meta_compare_seqnum (const GstMeta * meta1, const GstMeta * meta2)
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{
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guint64 seqnum1 = gst_meta_get_seqnum (meta1);
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guint64 seqnum2 = gst_meta_get_seqnum (meta2);
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if (seqnum1 == seqnum2)
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return 0;
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return (seqnum1 < seqnum2) ? -1 : 1;
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}
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