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443 lines
12 KiB
C
443 lines
12 KiB
C
/* GStreamer
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* Copyright (C) 2005 David Schleef <ds@schleef.org>
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*
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* gstminiobject.h: Header for GstMiniObject
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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., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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/**
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* SECTION:gstminiobject
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* @short_description: Lightweight base class for the GStreamer object hierarchy
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*
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* #GstMiniObject is a baseclass like #GObject, but has been stripped down of
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* features to be fast and small.
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* It offers sub-classing and ref-counting in the same way as #GObject does.
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* It has no properties and no signal-support though.
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*
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* Last reviewed on 2005-11-23 (0.9.5)
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "gst/gst_private.h"
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#include "gst/gstminiobject.h"
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#include "gst/gstinfo.h"
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#include <gobject/gvaluecollector.h>
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#define GST_DISABLE_TRACE
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#ifndef GST_DISABLE_TRACE
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#include "gsttrace.h"
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static GstAllocTrace *_gst_mini_object_trace;
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#endif
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/* Mutex used for weak referencing */
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G_LOCK_DEFINE_STATIC (weak_refs_mutex);
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/**
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* gst_mini_object_init:
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* @mini_object: a #GstMiniObject
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* @type: the #GType of the mini-object to create
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* @size: the size of the data
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*
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* Initializes a mini-object with the desired type and size.
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*
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* MT safe
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*
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* Returns: (transfer full): the new mini-object.
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*/
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void
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gst_mini_object_init (GstMiniObject * mini_object, GType type, gsize size)
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{
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mini_object->type = type;
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mini_object->refcount = 1;
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mini_object->flags = 0;
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mini_object->size = size;
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mini_object->n_weak_refs = 0;
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mini_object->weak_refs = NULL;
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}
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/**
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* gst_mini_object_copy:
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* @mini_object: the mini-object to copy
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*
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* Creates a copy of the mini-object.
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*
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* MT safe
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*
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* Returns: (transfer full): the new mini-object.
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*/
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GstMiniObject *
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gst_mini_object_copy (const GstMiniObject * mini_object)
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{
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GstMiniObject *copy;
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g_return_val_if_fail (mini_object != NULL, NULL);
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if (mini_object->copy)
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copy = mini_object->copy (mini_object);
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else
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copy = NULL;
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return copy;
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}
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/**
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* gst_mini_object_is_writable:
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* @mini_object: the mini-object to check
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*
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* Checks if a mini-object is writable. A mini-object is writable
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* if the reference count is one and the #GST_MINI_OBJECT_FLAG_READONLY
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* flag is not set. Modification of a mini-object should only be
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* done after verifying that it is writable.
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*
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* MT safe
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*
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* Returns: TRUE if the object is writable.
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*/
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gboolean
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gst_mini_object_is_writable (const GstMiniObject * mini_object)
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{
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g_return_val_if_fail (mini_object != NULL, FALSE);
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return (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
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}
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/**
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* gst_mini_object_make_writable:
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* @mini_object: (transfer full): the mini-object to make writable
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*
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* Checks if a mini-object is writable. If not, a writable copy is made and
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* returned. This gives away the reference to the original mini object,
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* and returns a reference to the new object.
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*
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* MT safe
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*
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* Returns: (transfer full): a mini-object (possibly the same pointer) that
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* is writable.
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*/
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GstMiniObject *
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gst_mini_object_make_writable (GstMiniObject * mini_object)
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{
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GstMiniObject *ret;
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g_return_val_if_fail (mini_object != NULL, NULL);
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if (gst_mini_object_is_writable (mini_object)) {
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ret = mini_object;
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} else {
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ret = gst_mini_object_copy (mini_object);
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GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
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g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
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gst_mini_object_unref (mini_object);
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}
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return ret;
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}
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/**
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* gst_mini_object_ref:
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* @mini_object: the mini-object
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*
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* Increase the reference count of the mini-object.
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*
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* Note that the refcount affects the writeability
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* of @mini-object, see gst_mini_object_is_writable(). It is
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* important to note that keeping additional references to
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* GstMiniObject instances can potentially increase the number
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* of memcpy operations in a pipeline, especially if the miniobject
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* is a #GstBuffer.
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*
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* Returns: (transfer full): the mini-object.
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*/
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GstMiniObject *
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gst_mini_object_ref (GstMiniObject * mini_object)
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{
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g_return_val_if_fail (mini_object != NULL, NULL);
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/* we can't assert that the refcount > 0 since the _free functions
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* increments the refcount from 0 to 1 again to allow resurecting
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* the object
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g_return_val_if_fail (mini_object->refcount > 0, NULL);
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*/
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GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
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GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
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GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
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g_atomic_int_inc (&mini_object->refcount);
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return mini_object;
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}
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static void
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weak_refs_notify (GstMiniObject * obj)
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{
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guint i;
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for (i = 0; i < obj->n_weak_refs; i++)
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obj->weak_refs[i].notify (obj->weak_refs[i].data, obj);
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g_free (obj->weak_refs);
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}
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/**
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* gst_mini_object_unref:
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* @mini_object: the mini-object
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*
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* Decreases the reference count of the mini-object, possibly freeing
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* the mini-object.
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*/
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void
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gst_mini_object_unref (GstMiniObject * mini_object)
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{
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g_return_if_fail (mini_object != NULL);
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g_return_if_fail (mini_object->refcount > 0);
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GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
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mini_object,
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GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
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GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
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if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
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gboolean do_free;
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if (mini_object->dispose)
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do_free = mini_object->dispose (mini_object);
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else
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do_free = TRUE;
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/* if the subclass recycled the object (and returned FALSE) we don't
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* want to free the instance anymore */
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if (G_LIKELY (do_free)) {
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/* The weak reference stack is freed in the notification function */
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if (mini_object->n_weak_refs)
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weak_refs_notify (mini_object);
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#ifndef GST_DISABLE_TRACE
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gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
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#endif
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if (mini_object->free)
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mini_object->free (mini_object);
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}
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}
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}
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/**
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* gst_mini_object_replace:
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* @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
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* be replaced
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* @newdata: pointer to new mini-object
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*
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* Atomically modifies a pointer to point to a new mini-object.
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* The reference count of @olddata is decreased and the reference count of
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* @newdata is increased.
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*
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* Either @newdata and the value pointed to by @olddata may be NULL.
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*
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* Returns: TRUE if @newdata was different from @olddata
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*/
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gboolean
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gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
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{
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GstMiniObject *olddata_val;
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g_return_val_if_fail (olddata != NULL, FALSE);
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GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
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*olddata, *olddata ? (*olddata)->refcount : 0,
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newdata, newdata ? newdata->refcount : 0);
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olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
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if (G_UNLIKELY (olddata_val == newdata))
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return FALSE;
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if (newdata)
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gst_mini_object_ref (newdata);
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while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
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olddata, olddata_val, newdata))) {
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olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
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if (G_UNLIKELY (olddata_val == newdata))
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break;
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}
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if (olddata_val)
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gst_mini_object_unref (olddata_val);
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return olddata_val != newdata;
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}
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/**
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* gst_mini_object_steal:
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* @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
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* be stolen
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*
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* Replace the current #GstMiniObject pointer to by @olddata with NULL and
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* return the old value.
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*
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* Returns: the #GstMiniObject at @oldata
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*/
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GstMiniObject *
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gst_mini_object_steal (GstMiniObject ** olddata)
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{
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GstMiniObject *olddata_val;
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g_return_val_if_fail (olddata != NULL, NULL);
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GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",
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*olddata, *olddata ? (*olddata)->refcount : 0);
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do {
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olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
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if (olddata_val == NULL)
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break;
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} while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
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olddata, olddata_val, NULL)));
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return olddata_val;
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}
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/**
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* gst_mini_object_take:
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* @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
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* be replaced
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* @newdata: pointer to new mini-object
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*
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* Modifies a pointer to point to a new mini-object. The modification
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* is done atomically. This version is similar to gst_mini_object_replace()
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* except that it does not increase the refcount of @newdata and thus
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* takes ownership of @newdata.
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*
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* Either @newdata and the value pointed to by @olddata may be NULL.
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*
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* Returns: TRUE if @newdata was different from @olddata
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*/
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gboolean
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gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)
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{
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GstMiniObject *olddata_val;
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g_return_val_if_fail (olddata != NULL, FALSE);
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GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",
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*olddata, *olddata ? (*olddata)->refcount : 0,
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newdata, newdata ? newdata->refcount : 0);
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do {
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olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
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if (G_UNLIKELY (olddata_val == newdata))
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break;
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} while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
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olddata, olddata_val, newdata)));
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if (olddata_val)
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gst_mini_object_unref (olddata_val);
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return olddata_val != newdata;
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}
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/**
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* gst_mini_object_weak_ref: (skip)
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* @object: #GstMiniObject to reference weakly
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* @notify: callback to invoke before the mini object is freed
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* @data: extra data to pass to notify
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*
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* Adds a weak reference callback to a mini object. Weak references are
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* used for notification when a mini object is finalized. They are called
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* "weak references" because they allow you to safely hold a pointer
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* to the mini object without calling gst_mini_object_ref()
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* (gst_mini_object_ref() adds a strong reference, that is, forces the object
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* to stay alive).
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*
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* Since: 0.10.35
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*/
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void
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gst_mini_object_weak_ref (GstMiniObject * object,
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GstMiniObjectWeakNotify notify, gpointer data)
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{
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guint i;
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g_return_if_fail (object != NULL);
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g_return_if_fail (notify != NULL);
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g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);
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G_LOCK (weak_refs_mutex);
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if (object->n_weak_refs) {
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/* Don't add the weak reference if it already exists. */
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for (i = 0; i < object->n_weak_refs; i++) {
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if (object->weak_refs[i].notify == notify &&
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object->weak_refs[i].data == data) {
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g_warning ("%s: Attempt to re-add existing weak ref %p(%p) failed.",
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G_STRFUNC, notify, data);
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goto found;
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}
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}
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i = object->n_weak_refs++;
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object->weak_refs =
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g_realloc (object->weak_refs, sizeof (object->weak_refs[0]) * i);
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} else {
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object->weak_refs = g_malloc0 (sizeof (object->weak_refs[0]));
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object->n_weak_refs = 1;
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i = 0;
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}
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object->weak_refs[i].notify = notify;
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object->weak_refs[i].data = data;
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found:
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G_UNLOCK (weak_refs_mutex);
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}
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/**
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* gst_mini_object_weak_unref: (skip)
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* @object: #GstMiniObject to remove a weak reference from
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* @notify: callback to search for
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* @data: data to search for
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*
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* Removes a weak reference callback to a mini object.
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*
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* Since: 0.10.35
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*/
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void
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gst_mini_object_weak_unref (GstMiniObject * object,
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GstMiniObjectWeakNotify notify, gpointer data)
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{
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gboolean found_one = FALSE;
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g_return_if_fail (object != NULL);
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g_return_if_fail (notify != NULL);
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G_LOCK (weak_refs_mutex);
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if (object->n_weak_refs) {
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guint i;
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for (i = 0; i < object->n_weak_refs; i++)
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if (object->weak_refs[i].notify == notify &&
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object->weak_refs[i].data == data) {
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found_one = TRUE;
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object->n_weak_refs -= 1;
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if (i != object->n_weak_refs)
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object->weak_refs[i] = object->weak_refs[object->n_weak_refs];
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break;
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}
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}
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G_UNLOCK (weak_refs_mutex);
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if (!found_one)
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g_warning ("%s: couldn't find weak ref %p(%p)", G_STRFUNC, notify, data);
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}
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