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 simple structure that can be used to implement refcounted
28 * Subclasses will include #GstMiniObject as the first member in their structure
29 * and then call gst_mini_object_init() to initialize the #GstMiniObject fields.
31 * gst_mini_object_ref() and gst_mini_object_unref() increment and decrement the
32 * refcount respectively. When the refcount of a mini-object reaches 0, the
33 * dispose function is called first and when this returns %TRUE, the free
34 * function of the miniobject is called.
36 * A copy can be made with gst_mini_object_copy().
38 * gst_mini_object_is_writable() will return %TRUE when the refcount of the
39 * object is exactly 1, meaning the current caller has the only reference to the
40 * object. gst_mini_object_make_writable() will return a writable version of the
41 * object, which might be a new copy when the refcount was not 1.
43 * Opaque data can be associated with a #GstMiniObject with
44 * gst_mini_object_set_qdata() and gst_mini_object_get_qdata(). The data is
45 * meant to be specific to the particular object and is not automatically copied
46 * with gst_mini_object_copy() or similar methods.
48 * A weak reference can be added and remove with gst_mini_object_weak_ref()
49 * and gst_mini_object_weak_unref() respectively.
51 * Last reviewed on 2012-06-15 (0.11.93)
57 #include "gst/gst_private.h"
58 #include "gst/gstminiobject.h"
59 #include "gst/gstinfo.h"
60 #include <gobject/gvaluecollector.h>
62 #ifndef GST_DISABLE_TRACE
64 static GstAllocTrace *_gst_mini_object_trace;
67 /* Mutex used for weak referencing */
68 G_LOCK_DEFINE_STATIC (qdata_mutex);
69 static GQuark weak_ref_quark;
74 GstMiniObjectNotify notify;
76 GDestroyNotify destroy;
79 #define QDATA(o,i) ((GstQData *)(o)->qdata)[(i)]
80 #define QDATA_QUARK(o,i) (QDATA(o,i).quark)
81 #define QDATA_NOTIFY(o,i) (QDATA(o,i).notify)
82 #define QDATA_DATA(o,i) (QDATA(o,i).data)
83 #define QDATA_DESTROY(o,i) (QDATA(o,i).destroy)
86 _priv_gst_mini_object_initialize (void)
88 weak_ref_quark = g_quark_from_static_string ("GstMiniObjectWeakRefQuark");
90 #ifndef GST_DISABLE_TRACE
91 _gst_mini_object_trace = _gst_alloc_trace_register ("GstMiniObject", 0);
96 * gst_mini_object_init: (skip)
97 * @mini_object: a #GstMiniObject
98 * @type: the #GType of the mini-object to create
99 * @copy_func: the copy function, or NULL
100 * @dispose_func: the dispose function, or NULL
101 * @free_func: the free function or NULL
103 * Initializes a mini-object with the desired type and copy/dispose/free
108 * Returns: (transfer full): the new mini-object.
111 gst_mini_object_init (GstMiniObject * mini_object, GType type,
112 GstMiniObjectCopyFunction copy_func,
113 GstMiniObjectDisposeFunction dispose_func,
114 GstMiniObjectFreeFunction free_func)
116 mini_object->type = type;
117 mini_object->refcount = 1;
118 mini_object->flags = 0;
120 mini_object->copy = copy_func;
121 mini_object->dispose = dispose_func;
122 mini_object->free = free_func;
124 mini_object->n_qdata = 0;
125 mini_object->qdata = NULL;
127 #ifndef GST_DISABLE_TRACE
128 _gst_alloc_trace_new (_gst_mini_object_trace, mini_object);
133 * gst_mini_object_copy:
134 * @mini_object: the mini-object to copy
136 * Creates a copy of the mini-object.
140 * Returns: (transfer full): the new mini-object.
143 gst_mini_object_copy (const GstMiniObject * mini_object)
147 g_return_val_if_fail (mini_object != NULL, NULL);
149 if (mini_object->copy)
150 copy = mini_object->copy (mini_object);
158 * gst_mini_object_is_writable:
159 * @mini_object: the mini-object to check
161 * Checks if a mini-object is writable. A mini-object is writable
162 * if the reference count is one. Modification of a mini-object should
163 * only be done after verifying that it is writable.
167 * Returns: TRUE if the object is writable.
170 gst_mini_object_is_writable (const GstMiniObject * mini_object)
172 g_return_val_if_fail (mini_object != NULL, FALSE);
174 return (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
178 * gst_mini_object_make_writable:
179 * @mini_object: (transfer full): the mini-object to make writable
181 * Checks if a mini-object is writable. If not, a writable copy is made and
182 * returned. This gives away the reference to the original mini object,
183 * and returns a reference to the new object.
187 * Returns: (transfer full): a mini-object (possibly the same pointer) that
191 gst_mini_object_make_writable (GstMiniObject * mini_object)
195 g_return_val_if_fail (mini_object != NULL, NULL);
197 if (gst_mini_object_is_writable (mini_object)) {
200 ret = gst_mini_object_copy (mini_object);
201 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
202 g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
203 gst_mini_object_unref (mini_object);
210 * gst_mini_object_ref:
211 * @mini_object: the mini-object
213 * Increase the reference count of the mini-object.
215 * Note that the refcount affects the writeability
216 * of @mini-object, see gst_mini_object_is_writable(). It is
217 * important to note that keeping additional references to
218 * GstMiniObject instances can potentially increase the number
219 * of memcpy operations in a pipeline, especially if the miniobject
222 * Returns: (transfer full): the mini-object.
225 gst_mini_object_ref (GstMiniObject * mini_object)
227 g_return_val_if_fail (mini_object != NULL, NULL);
228 /* we can't assert that the refcount > 0 since the _free functions
229 * increments the refcount from 0 to 1 again to allow resurecting
231 g_return_val_if_fail (mini_object->refcount > 0, NULL);
234 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
235 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
236 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
238 g_atomic_int_inc (&mini_object->refcount);
244 find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,
245 GstMiniObjectNotify notify, gpointer data)
249 for (i = 0; i < object->n_qdata; i++) {
250 if (QDATA_QUARK (object, i) == quark) {
251 /* check if we need to match the callback too */
252 if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&
253 QDATA_DATA (object, i) == data))
261 remove_notify (GstMiniObject * object, gint index)
264 if (--object->n_qdata == 0) {
265 /* we don't shrink but free when everything is gone */
266 g_free (object->qdata);
267 object->qdata = NULL;
268 } else if (index != object->n_qdata)
269 QDATA (object, index) = QDATA (object, object->n_qdata);
273 set_notify (GstMiniObject * object, gint index, GQuark quark,
274 GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)
278 index = object->n_qdata++;
280 g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);
282 QDATA_QUARK (object, index) = quark;
283 QDATA_NOTIFY (object, index) = notify;
284 QDATA_DATA (object, index) = data;
285 QDATA_DESTROY (object, index) = destroy;
289 call_finalize_notify (GstMiniObject * obj)
293 for (i = 0; i < obj->n_qdata; i++) {
294 if (QDATA_QUARK (obj, i) == weak_ref_quark)
295 QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);
296 if (QDATA_DESTROY (obj, i))
297 QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));
302 * gst_mini_object_unref:
303 * @mini_object: the mini-object
305 * Decreases the reference count of the mini-object, possibly freeing
309 gst_mini_object_unref (GstMiniObject * mini_object)
311 g_return_if_fail (mini_object != NULL);
313 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
315 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
316 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
318 g_return_if_fail (mini_object->refcount > 0);
320 if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
323 if (mini_object->dispose)
324 do_free = mini_object->dispose (mini_object);
328 /* if the subclass recycled the object (and returned FALSE) we don't
329 * want to free the instance anymore */
330 if (G_LIKELY (do_free)) {
331 if (mini_object->n_qdata) {
332 call_finalize_notify (mini_object);
333 g_free (mini_object->qdata);
335 #ifndef GST_DISABLE_TRACE
336 _gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
338 if (mini_object->free)
339 mini_object->free (mini_object);
345 * gst_mini_object_replace:
346 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
348 * @newdata: pointer to new mini-object
350 * Atomically modifies a pointer to point to a new mini-object.
351 * The reference count of @olddata is decreased and the reference count of
352 * @newdata is increased.
354 * Either @newdata and the value pointed to by @olddata may be NULL.
356 * Returns: TRUE if @newdata was different from @olddata
359 gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
361 GstMiniObject *olddata_val;
363 g_return_val_if_fail (olddata != NULL, FALSE);
365 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
366 *olddata, *olddata ? (*olddata)->refcount : 0,
367 newdata, newdata ? newdata->refcount : 0);
369 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
371 if (G_UNLIKELY (olddata_val == newdata))
375 gst_mini_object_ref (newdata);
377 while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
378 olddata, olddata_val, newdata))) {
379 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
380 if (G_UNLIKELY (olddata_val == newdata))
385 gst_mini_object_unref (olddata_val);
387 return olddata_val != newdata;
391 * gst_mini_object_steal:
392 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
395 * Replace the current #GstMiniObject pointer to by @olddata with NULL and
396 * return the old value.
398 * Returns: the #GstMiniObject at @oldata
401 gst_mini_object_steal (GstMiniObject ** olddata)
403 GstMiniObject *olddata_val;
405 g_return_val_if_fail (olddata != NULL, NULL);
407 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",
408 *olddata, *olddata ? (*olddata)->refcount : 0);
411 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
412 if (olddata_val == NULL)
414 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
415 olddata, olddata_val, NULL)));
421 * gst_mini_object_take:
422 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
424 * @newdata: pointer to new mini-object
426 * Modifies a pointer to point to a new mini-object. The modification
427 * is done atomically. This version is similar to gst_mini_object_replace()
428 * except that it does not increase the refcount of @newdata and thus
429 * takes ownership of @newdata.
431 * Either @newdata and the value pointed to by @olddata may be NULL.
433 * Returns: TRUE if @newdata was different from @olddata
436 gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)
438 GstMiniObject *olddata_val;
440 g_return_val_if_fail (olddata != NULL, FALSE);
442 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",
443 *olddata, *olddata ? (*olddata)->refcount : 0,
444 newdata, newdata ? newdata->refcount : 0);
447 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
448 if (G_UNLIKELY (olddata_val == newdata))
450 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
451 olddata, olddata_val, newdata)));
454 gst_mini_object_unref (olddata_val);
456 return olddata_val != newdata;
460 * gst_mini_object_weak_ref: (skip)
461 * @object: #GstMiniObject to reference weakly
462 * @notify: callback to invoke before the mini object is freed
463 * @data: extra data to pass to notify
465 * Adds a weak reference callback to a mini object. Weak references are
466 * used for notification when a mini object is finalized. They are called
467 * "weak references" because they allow you to safely hold a pointer
468 * to the mini object without calling gst_mini_object_ref()
469 * (gst_mini_object_ref() adds a strong reference, that is, forces the object
475 gst_mini_object_weak_ref (GstMiniObject * object,
476 GstMiniObjectNotify notify, gpointer data)
478 g_return_if_fail (object != NULL);
479 g_return_if_fail (notify != NULL);
480 g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);
482 G_LOCK (qdata_mutex);
483 set_notify (object, -1, weak_ref_quark, notify, data, NULL);
484 G_UNLOCK (qdata_mutex);
488 * gst_mini_object_weak_unref: (skip)
489 * @object: #GstMiniObject to remove a weak reference from
490 * @notify: callback to search for
491 * @data: data to search for
493 * Removes a weak reference callback from a mini object.
498 gst_mini_object_weak_unref (GstMiniObject * object,
499 GstMiniObjectNotify notify, gpointer data)
503 g_return_if_fail (object != NULL);
504 g_return_if_fail (notify != NULL);
506 G_LOCK (qdata_mutex);
507 if ((i = find_notify (object, weak_ref_quark, TRUE, notify, data)) != -1) {
508 remove_notify (object, i);
510 g_warning ("%s: couldn't find weak ref %p(%p)", G_STRFUNC, notify, data);
512 G_UNLOCK (qdata_mutex);
516 * gst_mini_object_set_qdata:
517 * @object: a #GstMiniObject
518 * @quark: A #GQuark, naming the user data pointer
519 * @data: An opaque user data pointer
520 * @destroy: Function to invoke with @data as argument, when @data
523 * This sets an opaque, named pointer on a miniobject.
524 * The name is specified through a #GQuark (retrived e.g. via
525 * g_quark_from_static_string()), and the pointer
526 * can be gotten back from the @object with gst_mini_object_get_qdata()
527 * until the @object is disposed.
528 * Setting a previously set user data pointer, overrides (frees)
529 * the old pointer set, using #NULL as pointer essentially
530 * removes the data stored.
532 * @destroy may be specified which is called with @data as argument
533 * when the @object is disposed, or the data is being overwritten by
534 * a call to gst_mini_object_set_qdata() with the same @quark.
537 gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,
538 gpointer data, GDestroyNotify destroy)
541 gpointer old_data = NULL;
542 GDestroyNotify old_notify = NULL;
544 g_return_if_fail (object != NULL);
545 g_return_if_fail (quark > 0);
547 G_LOCK (qdata_mutex);
548 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
550 old_data = QDATA_DATA (object, i);
551 old_notify = QDATA_DESTROY (object, i);
554 remove_notify (object, i);
557 set_notify (object, i, quark, NULL, data, destroy);
558 G_UNLOCK (qdata_mutex);
561 old_notify (old_data);
565 * gst_mini_object_get_qdata:
566 * @object: The GstMiniObject to get a stored user data pointer from
567 * @quark: A #GQuark, naming the user data pointer
569 * This function gets back user data pointers stored via
570 * gst_mini_object_set_qdata().
572 * Returns: (transfer none): The user data pointer set, or %NULL
575 gst_mini_object_get_qdata (GstMiniObject * object, GQuark quark)
580 g_return_val_if_fail (object != NULL, NULL);
581 g_return_val_if_fail (quark > 0, NULL);
583 G_LOCK (qdata_mutex);
584 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1)
585 result = QDATA_DATA (object, i);
588 G_UNLOCK (qdata_mutex);
594 * gst_mini_object_steal_qdata:
595 * @object: The GstMiniObject to get a stored user data pointer from
596 * @quark: A #GQuark, naming the user data pointer
598 * This function gets back user data pointers stored via gst_mini_object_set_qdata()
599 * and removes the data from @object without invoking its destroy() function (if
602 * Returns: (transfer full): The user data pointer set, or %NULL
605 gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)
610 g_return_val_if_fail (object != NULL, NULL);
611 g_return_val_if_fail (quark > 0, NULL);
613 G_LOCK (qdata_mutex);
614 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
615 result = QDATA_DATA (object, i);
616 remove_notify (object, i);
620 G_UNLOCK (qdata_mutex);