2 * Copyright (C) 2005 David Schleef <ds@schleef.org>
4 * gstminiobject.h: Header for GstMiniObject
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Library General Public
8 * License as published by the Free Software Foundation; either
9 * version 2 of the License, or (at your option) any later version.
11 * This library is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Library General Public License for more details.
16 * You should have received a copy of the GNU Library General Public
17 * License along with this library; if not, write to the
18 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
19 * Boston, MA 02111-1307, USA.
22 * SECTION:gstminiobject
23 * @short_description: Lightweight base class for the GStreamer object hierarchy
25 * #GstMiniObject is a baseclass like #GObject, but has been stripped down of
26 * features to be fast and small.
27 * It offers sub-classing and ref-counting in the same way as #GObject does.
28 * It has no properties and no signal-support though.
30 * Last reviewed on 2005-11-23 (0.9.5)
36 #include "gst/gst_private.h"
37 #include "gst/gstminiobject.h"
38 #include "gst/gstinfo.h"
39 #include <gobject/gvaluecollector.h>
41 #define GST_DISABLE_TRACE
43 #ifndef GST_DISABLE_TRACE
45 static GstAllocTrace *_gst_mini_object_trace;
48 #define GST_MINI_OBJECT_GET_CLASS_UNCHECKED(obj) \
49 ((GstMiniObjectClass *) (((GTypeInstance*)(obj))->g_class))
51 /* boxed copy and free functions. Don't real copy or free but simply
52 * change the refcount */
53 static GstMiniObject *
54 _gst_mini_object_boxed_copy (GstMiniObject * mini_object)
57 return gst_mini_object_ref (mini_object);
63 _gst_mini_object_boxed_free (GstMiniObject * mini_object)
66 gst_mini_object_unref (mini_object);
70 * gst_mini_object_register:
71 * @name: name of the new boxed type
73 * This function creates a new G_TYPE_BOXED derived type id for a new boxed type
74 * with name @name. The default miniobject refcounting copy and free function
75 * are used for the boxed type.
77 * Returns: a new G_TYPE_BOXED derived type id for @name.
80 gst_mini_object_register (const gchar * name)
84 g_return_val_if_fail (name != NULL, 0);
86 type = g_boxed_type_register_static (name,
87 (GBoxedCopyFunc) _gst_mini_object_boxed_copy,
88 (GBoxedFreeFunc) _gst_mini_object_boxed_free);
94 * gst_mini_object_init:
95 * @mini_object: a #GstMiniObject
96 * @type: the #GType of the mini-object to create
97 * @size: the size of the data
99 * Initializes a mini-object with the desired type and size.
103 * Returns: (transfer full): the new mini-object.
106 gst_mini_object_init (GstMiniObject * mini_object, GType type, gsize size)
108 mini_object->type = type;
109 mini_object->refcount = 1;
110 mini_object->size = size;
113 /* FIXME 0.11: Current way of doing the copy makes it impossible
114 * to currectly chain to the parent classes and do a copy in a
115 * subclass without knowing all internals of the parent classes.
117 * For 0.11 we should do something like the following:
118 * - The GstMiniObjectClass::copy() implementation of GstMiniObject
119 * should call g_type_create_instance() with the type of the source
121 * - All GstMiniObjectClass::copy() implementations should as first
122 * thing chain up to the parent class and then do whatever they need
123 * to do to copy their type specific data. Note that this way the
124 * instance_init() functions are called!
128 * gst_mini_object_copy:
129 * @mini_object: the mini-object to copy
131 * Creates a copy of the mini-object.
135 * Returns: (transfer full): the new mini-object.
138 gst_mini_object_copy (const GstMiniObject * mini_object)
142 g_return_val_if_fail (mini_object != NULL, NULL);
144 if (mini_object->copy)
145 copy = mini_object->copy (mini_object);
153 * gst_mini_object_is_writable:
154 * @mini_object: the mini-object to check
156 * Checks if a mini-object is writable. A mini-object is writable
157 * if the reference count is one and the #GST_MINI_OBJECT_FLAG_READONLY
158 * flag is not set. Modification of a mini-object should only be
159 * done after verifying that it is writable.
163 * Returns: TRUE if the object is writable.
166 gst_mini_object_is_writable (const GstMiniObject * mini_object)
168 g_return_val_if_fail (mini_object != NULL, FALSE);
170 return (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1) &&
171 ((mini_object->flags & GST_MINI_OBJECT_FLAG_READONLY) == 0);
175 * gst_mini_object_make_writable:
176 * @mini_object: (transfer full): the mini-object to make writable
178 * Checks if a mini-object is writable. If not, a writable copy is made and
179 * returned. This gives away the reference to the original mini object,
180 * and returns a reference to the new object.
184 * Returns: (transfer full): a mini-object (possibly the same pointer) that
188 gst_mini_object_make_writable (GstMiniObject * mini_object)
192 g_return_val_if_fail (mini_object != NULL, NULL);
194 if (gst_mini_object_is_writable (mini_object)) {
197 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject",
198 g_type_name (G_TYPE_FROM_INSTANCE (mini_object)));
199 ret = gst_mini_object_copy (mini_object);
200 gst_mini_object_unref (mini_object);
207 * gst_mini_object_ref:
208 * @mini_object: the mini-object
210 * Increase the reference count of the mini-object.
212 * Note that the refcount affects the writeability
213 * of @mini-object, see gst_mini_object_is_writable(). It is
214 * important to note that keeping additional references to
215 * GstMiniObject instances can potentially increase the number
216 * of memcpy operations in a pipeline, especially if the miniobject
219 * Returns: the mini-object.
222 gst_mini_object_ref (GstMiniObject * mini_object)
224 g_return_val_if_fail (mini_object != NULL, NULL);
225 /* we can't assert that the refcount > 0 since the _free functions
226 * increments the refcount from 0 to 1 again to allow resurecting
228 g_return_val_if_fail (mini_object->refcount > 0, NULL);
231 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
232 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
233 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
235 g_atomic_int_inc (&mini_object->refcount);
241 * gst_mini_object_unref:
242 * @mini_object: the mini-object
244 * Decreases the reference count of the mini-object, possibly freeing
248 gst_mini_object_unref (GstMiniObject * mini_object)
250 g_return_if_fail (mini_object != NULL);
251 g_return_if_fail (mini_object->refcount > 0);
253 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
255 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
256 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
258 if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
259 /* At this point, the refcount of the object is 0. We increase the refcount
260 * here because if a subclass recycles the object and gives out a new
261 * reference we don't want to free the instance anymore. */
262 gst_mini_object_ref (mini_object);
264 if (mini_object->dispose)
265 mini_object->dispose (mini_object);
267 /* decrement the refcount again, if the subclass recycled the object we don't
268 * want to free the instance anymore */
269 if (G_LIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
270 #ifndef GST_DISABLE_TRACE
271 gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
273 if (mini_object->free)
274 mini_object->free (mini_object);
280 * gst_mini_object_replace:
281 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
283 * @newdata: pointer to new mini-object
285 * Modifies a pointer to point to a new mini-object. The modification
286 * is done atomically, and the reference counts are updated correctly.
287 * Either @newdata and the value pointed to by @olddata may be NULL.
290 gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
292 GstMiniObject *olddata_val;
294 g_return_if_fail (olddata != NULL);
296 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
297 *olddata, *olddata ? (*olddata)->refcount : 0,
298 newdata, newdata ? newdata->refcount : 0);
300 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
302 if (olddata_val == newdata)
306 gst_mini_object_ref (newdata);
308 while (!g_atomic_pointer_compare_and_exchange ((gpointer *) olddata,
309 olddata_val, newdata)) {
310 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
314 gst_mini_object_unref (olddata_val);