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 /* Mutex used for weak referencing */
49 G_LOCK_DEFINE_STATIC (weak_refs_mutex);
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->flags = 0;
111 mini_object->size = size;
112 mini_object->n_weak_refs = 0;
113 mini_object->weak_refs = NULL;
117 * gst_mini_object_copy:
118 * @mini_object: the mini-object to copy
120 * Creates a copy of the mini-object.
124 * Returns: (transfer full): the new mini-object.
127 gst_mini_object_copy (const GstMiniObject * mini_object)
131 g_return_val_if_fail (mini_object != NULL, NULL);
133 if (mini_object->copy)
134 copy = mini_object->copy (mini_object);
142 * gst_mini_object_is_writable:
143 * @mini_object: the mini-object to check
145 * Checks if a mini-object is writable. A mini-object is writable
146 * if the reference count is one and the #GST_MINI_OBJECT_FLAG_READONLY
147 * flag is not set. Modification of a mini-object should only be
148 * done after verifying that it is writable.
152 * Returns: TRUE if the object is writable.
155 gst_mini_object_is_writable (const GstMiniObject * mini_object)
157 g_return_val_if_fail (mini_object != NULL, FALSE);
159 return (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
163 * gst_mini_object_make_writable:
164 * @mini_object: (transfer full): the mini-object to make writable
166 * Checks if a mini-object is writable. If not, a writable copy is made and
167 * returned. This gives away the reference to the original mini object,
168 * and returns a reference to the new object.
172 * Returns: (transfer full): a mini-object (possibly the same pointer) that
176 gst_mini_object_make_writable (GstMiniObject * mini_object)
180 g_return_val_if_fail (mini_object != NULL, NULL);
182 if (gst_mini_object_is_writable (mini_object)) {
185 ret = gst_mini_object_copy (mini_object);
186 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
187 g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
188 gst_mini_object_unref (mini_object);
195 * gst_mini_object_ref:
196 * @mini_object: the mini-object
198 * Increase the reference count of the mini-object.
200 * Note that the refcount affects the writeability
201 * of @mini-object, see gst_mini_object_is_writable(). It is
202 * important to note that keeping additional references to
203 * GstMiniObject instances can potentially increase the number
204 * of memcpy operations in a pipeline, especially if the miniobject
207 * Returns: (transfer full): the mini-object.
210 gst_mini_object_ref (GstMiniObject * mini_object)
212 g_return_val_if_fail (mini_object != NULL, NULL);
213 /* we can't assert that the refcount > 0 since the _free functions
214 * increments the refcount from 0 to 1 again to allow resurecting
216 g_return_val_if_fail (mini_object->refcount > 0, NULL);
219 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
220 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
221 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
223 g_atomic_int_inc (&mini_object->refcount);
229 weak_refs_notify (GstMiniObject * obj)
233 for (i = 0; i < obj->n_weak_refs; i++)
234 obj->weak_refs[i].notify (obj->weak_refs[i].data, obj);
235 g_free (obj->weak_refs);
239 * gst_mini_object_unref:
240 * @mini_object: the mini-object
242 * Decreases the reference count of the mini-object, possibly freeing
246 gst_mini_object_unref (GstMiniObject * mini_object)
248 g_return_if_fail (mini_object != NULL);
249 g_return_if_fail (mini_object->refcount > 0);
251 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
253 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
254 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
256 if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
257 /* At this point, the refcount of the object is 0. We increase the refcount
258 * here because if a subclass recycles the object and gives out a new
259 * reference we don't want to free the instance anymore. */
260 gst_mini_object_ref (mini_object);
262 if (mini_object->dispose)
263 mini_object->dispose (mini_object);
265 /* decrement the refcount again, if the subclass recycled the object we don't
266 * want to free the instance anymore */
267 if (G_LIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
268 /* The weak reference stack is freed in the notification function */
269 if (mini_object->n_weak_refs)
270 weak_refs_notify (mini_object);
272 #ifndef GST_DISABLE_TRACE
273 gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
275 if (mini_object->free)
276 mini_object->free (mini_object);
282 * gst_mini_object_replace:
283 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
285 * @newdata: pointer to new mini-object
287 * Modifies a pointer to point to a new mini-object. The modification
288 * is done atomically, and the reference counts are updated correctly.
289 * Either @newdata and the value pointed to by @olddata may be NULL.
292 gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
294 GstMiniObject *olddata_val;
296 g_return_if_fail (olddata != NULL);
298 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
299 *olddata, *olddata ? (*olddata)->refcount : 0,
300 newdata, newdata ? newdata->refcount : 0);
302 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
304 if (olddata_val == newdata)
308 gst_mini_object_ref (newdata);
310 while (!g_atomic_pointer_compare_and_exchange ((gpointer *) olddata,
311 olddata_val, newdata)) {
312 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
316 gst_mini_object_unref (olddata_val);
320 * gst_mini_object_weak_ref: (skip)
321 * @object: #GstMiniObject to reference weakly
322 * @notify: callback to invoke before the mini object is freed
323 * @data: extra data to pass to notify
325 * Adds a weak reference callback to a mini object. Weak references are
326 * used for notification when a mini object is finalized. They are called
327 * "weak references" because they allow you to safely hold a pointer
328 * to the mini object without calling gst_mini_object_ref()
329 * (gst_mini_object_ref() adds a strong reference, that is, forces the object
335 gst_mini_object_weak_ref (GstMiniObject * object,
336 GstMiniObjectWeakNotify notify, gpointer data)
340 g_return_if_fail (object != NULL);
341 g_return_if_fail (notify != NULL);
342 g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);
344 G_LOCK (weak_refs_mutex);
346 if (object->n_weak_refs) {
347 /* Don't add the weak reference if it already exists. */
348 for (i = 0; i < object->n_weak_refs; i++) {
349 if (object->weak_refs[i].notify == notify &&
350 object->weak_refs[i].data == data) {
351 g_warning ("%s: Attempt to re-add existing weak ref %p(%p) failed.",
352 G_STRFUNC, notify, data);
357 i = object->n_weak_refs++;
359 g_realloc (object->weak_refs, sizeof (object->weak_refs[0]) * i);
361 object->weak_refs = g_malloc0 (sizeof (object->weak_refs[0]));
362 object->n_weak_refs = 1;
365 object->weak_refs[i].notify = notify;
366 object->weak_refs[i].data = data;
368 G_UNLOCK (weak_refs_mutex);
372 * gst_mini_object_weak_unref: (skip)
373 * @object: #GstMiniObject to remove a weak reference from
374 * @notify: callback to search for
375 * @data: data to search for
377 * Removes a weak reference callback to a mini object.
382 gst_mini_object_weak_unref (GstMiniObject * object,
383 GstMiniObjectWeakNotify notify, gpointer data)
385 gboolean found_one = FALSE;
387 g_return_if_fail (object != NULL);
388 g_return_if_fail (notify != NULL);
390 G_LOCK (weak_refs_mutex);
392 if (object->n_weak_refs) {
395 for (i = 0; i < object->n_weak_refs; i++)
396 if (object->weak_refs[i].notify == notify &&
397 object->weak_refs[i].data == data) {
399 object->n_weak_refs -= 1;
400 if (i != object->n_weak_refs)
401 object->weak_refs[i] = object->weak_refs[object->n_weak_refs];
406 G_UNLOCK (weak_refs_mutex);
408 g_warning ("%s: couldn't find weak ref %p(%p)", G_STRFUNC, notify, data);