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Diffstat (limited to 'gst/gstcontext.c')
| -rw-r--r-- | gst/gstcontext.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/gst/gstcontext.c b/gst/gstcontext.c new file mode 100644 index 0000000000..6c6c38e4d7 --- /dev/null +++ b/gst/gstcontext.c @@ -0,0 +1,180 @@ +/* GStreamer + * Copyright (C) 2013 Collabora Ltd. + * Author: Sebastian Dröge <sebastian.droege@collabora.co.uk> + * + * gstcontext.h: Header for GstContext subsystem + * + * 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:gstcontext + * @short_description: Lightweight objects to represent element contexts + * @see_also: #GstMiniObject, #GstElement + * + * #GstContext is a container object used to store contexts like a device + * context, a display server connection and similar concepts that should + * be shared between multiple elements. + * + * Applications can set a context on a complete pipeline by using + * gst_element_set_context(), which will then be propagated to all + * child elements. Elements can handle these in GstElement::set_context() + * and merge them with the context information they already have. + * + * When an element needs a context it will do the following actions in this + * order until one step succeeds: + * 1) Check if the element already has a context + * 2) Query downstream with GST_QUERY_CONTEXT for the context + * 3) Post a GST_MESSAGE_NEED_CONTEXT message on the bus with the required + * context types and afterwards check if a usable context was set now + * 4) Create a context by itself and post a GST_MESSAGE_HAVE_CONTEXT message + * and send a GST_EVENT_CONTEXT event downstream, containing the complete + * context information at this time. + * + * Applications should catch the GST_MESSAGE_HAVE_CONTEXT messages and remember + * any content from it unless it has a custom version of a specific context. If + * later an element is posting a GST_MESSAGE_NEED_CONTEXT message for a specific + * context that was created by an element before the application should pass it + * to the complete pipeline. + */ + +#include "gst_private.h" +#include <string.h> +#include "gstcontext.h" +#include "gstquark.h" + +struct _GstContext +{ + GstMiniObject mini_object; + + GstStructure *structure; +}; + +#define GST_CONTEXT_STRUCTURE(c) (((GstContext *)(c))->structure) + +static GType _gst_context_type = 0; +GST_DEFINE_MINI_OBJECT_TYPE (GstContext, gst_context); + +void +_priv_gst_context_initialize (void) +{ + GST_CAT_INFO (GST_CAT_GST_INIT, "init contexts"); + + /* the GstMiniObject types need to be class_ref'd once before it can be + * done from multiple threads; + * see http://bugzilla.gnome.org/show_bug.cgi?id=304551 */ + gst_context_get_type (); + + _gst_context_type = gst_context_get_type (); +} + +static void +_gst_context_free (GstContext * context) +{ + GstStructure *structure; + + g_return_if_fail (context != NULL); + + GST_CAT_LOG (GST_CAT_CONTEXT, "finalize context %p: %" GST_PTR_FORMAT, + context, GST_CONTEXT_STRUCTURE (context)); + + structure = GST_CONTEXT_STRUCTURE (context); + if (structure) { + gst_structure_set_parent_refcount (structure, NULL); + gst_structure_free (structure); + } + + g_slice_free1 (sizeof (GstContext), context); +} + +static void gst_context_init (GstContext * context); + +static GstContext * +_gst_context_copy (GstContext * context) +{ + GstContext *copy; + GstStructure *structure; + + GST_CAT_LOG (GST_CAT_CONTEXT, "copy context %p: %" GST_PTR_FORMAT, context, + GST_CONTEXT_STRUCTURE (context)); + + copy = g_slice_new0 (GstContext); + + gst_context_init (copy); + + structure = GST_CONTEXT_STRUCTURE (context); + GST_CONTEXT_STRUCTURE (copy) = gst_structure_copy (structure); + gst_structure_set_parent_refcount (GST_CONTEXT_STRUCTURE (copy), + ©->mini_object.refcount); + + return GST_CONTEXT_CAST (copy); +} + +static void +gst_context_init (GstContext * context) +{ + gst_mini_object_init (GST_MINI_OBJECT_CAST (context), 0, _gst_context_type, + (GstMiniObjectCopyFunction) _gst_context_copy, NULL, + (GstMiniObjectFreeFunction) _gst_context_free); +} + +/** + * gst_context_new: + * + * Create a new context. + * + * Returns: (transfer full): The new context. + * + * MT safe. + */ +GstContext * +gst_context_new (void) +{ + GstContext *context; + GstStructure *structure; + + context = g_slice_new0 (GstContext); + + GST_CAT_LOG (GST_CAT_CONTEXT, "creating new context %p", context); + + structure = gst_structure_new_id_empty (GST_QUARK (CONTEXT)); + gst_structure_set_parent_refcount (structure, &context->mini_object.refcount); + gst_context_init (context); + + GST_CONTEXT_STRUCTURE (context) = structure; + + return context; +} + +/** + * gst_context_get_structure: + * @context: The #GstContext. + * + * Access the structure of the context. + * + * Returns: (transfer none): The structure of the context. The structure is + * still owned by the context, which means that you should not modify it, + * free it and that the pointer becomes invalid when you free the context. + * + * MT safe. + */ +const GstStructure * +gst_context_get_structure (GstContext * context) +{ + g_return_val_if_fail (GST_IS_CONTEXT (context), NULL); + + return GST_CONTEXT_STRUCTURE (context); +} |