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;
71 #define SHARE_ONE (1 << 16)
72 #define SHARE_TWO (2 << 16)
73 #define SHARE_MASK (~(SHARE_ONE - 1))
74 #define IS_SHARED(state) (state >= SHARE_TWO)
75 #define LOCK_ONE (GST_LOCK_FLAG_LAST)
76 #define FLAG_MASK (GST_LOCK_FLAG_LAST - 1)
77 #define LOCK_MASK ((SHARE_ONE - 1) - FLAG_MASK)
78 #define LOCK_FLAG_MASK (SHARE_ONE - 1)
83 GstMiniObjectNotify notify;
85 GDestroyNotify destroy;
88 #define QDATA(o,i) ((GstQData *)(o)->qdata)[(i)]
89 #define QDATA_QUARK(o,i) (QDATA(o,i).quark)
90 #define QDATA_NOTIFY(o,i) (QDATA(o,i).notify)
91 #define QDATA_DATA(o,i) (QDATA(o,i).data)
92 #define QDATA_DESTROY(o,i) (QDATA(o,i).destroy)
95 _priv_gst_mini_object_initialize (void)
97 weak_ref_quark = g_quark_from_static_string ("GstMiniObjectWeakRefQuark");
99 #ifndef GST_DISABLE_TRACE
100 _gst_mini_object_trace = _gst_alloc_trace_register ("GstMiniObject", 0);
105 * gst_mini_object_init: (skip)
106 * @mini_object: a #GstMiniObject
107 * @flags: initial #GstMiniObjectFlags
108 * @type: the #GType of the mini-object to create
109 * @copy_func: the copy function, or NULL
110 * @dispose_func: the dispose function, or NULL
111 * @free_func: the free function or NULL
113 * Initializes a mini-object with the desired type and copy/dispose/free
117 gst_mini_object_init (GstMiniObject * mini_object, guint flags, GType type,
118 GstMiniObjectCopyFunction copy_func,
119 GstMiniObjectDisposeFunction dispose_func,
120 GstMiniObjectFreeFunction free_func)
122 mini_object->type = type;
123 mini_object->refcount = 1;
124 mini_object->lockstate =
125 (flags & GST_MINI_OBJECT_FLAG_LOCK_READONLY ? GST_LOCK_FLAG_READ : 0);
126 mini_object->flags = flags;
128 mini_object->copy = copy_func;
129 mini_object->dispose = dispose_func;
130 mini_object->free = free_func;
132 mini_object->n_qdata = 0;
133 mini_object->qdata = NULL;
135 #ifndef GST_DISABLE_TRACE
136 _gst_alloc_trace_new (_gst_mini_object_trace, mini_object);
141 * gst_mini_object_copy:
142 * @mini_object: the mini-object to copy
144 * Creates a copy of the mini-object.
148 * Returns: (transfer full): the new mini-object.
151 gst_mini_object_copy (const GstMiniObject * mini_object)
155 g_return_val_if_fail (mini_object != NULL, NULL);
157 if (mini_object->copy)
158 copy = mini_object->copy (mini_object);
166 * gst_mini_object_lock:
167 * @object: the mini-object to lock
168 * @flags: #GstLockFlags
170 * Lock the mini-object with the specified access mode in @flags.
172 * Returns: %TRUE if @object could be locked.
175 gst_mini_object_lock (GstMiniObject * object, GstLockFlags flags)
177 gint access_mode, state, newstate;
179 g_return_val_if_fail (object != NULL, FALSE);
180 g_return_val_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object), FALSE);
183 access_mode = flags & FLAG_MASK;
184 newstate = state = g_atomic_int_get (&object->lockstate);
186 GST_CAT_TRACE (GST_CAT_LOCKING, "lock %p: state %08x, access_mode %d",
187 object, state, access_mode);
189 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
191 newstate += SHARE_ONE;
192 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
196 /* shared counter > 1 and write access is not allowed */
197 if (access_mode & GST_LOCK_FLAG_WRITE && IS_SHARED (state))
200 if ((state & LOCK_FLAG_MASK) == 0) {
201 /* nothing mapped, set access_mode */
202 newstate |= access_mode;
204 /* access_mode must match */
205 if ((state & access_mode) != access_mode)
208 /* increase refcount */
209 newstate += LOCK_ONE;
211 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
218 GST_CAT_DEBUG (GST_CAT_LOCKING,
219 "lock failed %p: state %08x, access_mode %d", object, state,
226 * gst_mini_object_unlock:
227 * @object: the mini-object to unlock
228 * @flags: #GstLockFlags
230 * Unlock the mini-object with the specified access mode in @flags.
233 gst_mini_object_unlock (GstMiniObject * object, GstLockFlags flags)
235 gint access_mode, state, newstate;
237 g_return_if_fail (object != NULL);
238 g_return_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object));
241 access_mode = flags & FLAG_MASK;
242 newstate = state = g_atomic_int_get (&object->lockstate);
244 GST_CAT_TRACE (GST_CAT_LOCKING, "unlock %p: state %08x, access_mode %d",
245 object, state, access_mode);
247 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
249 g_return_if_fail (state >= SHARE_ONE);
250 newstate -= SHARE_ONE;
251 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
255 g_return_if_fail ((state & access_mode) == access_mode);
256 /* decrease the refcount */
257 newstate -= LOCK_ONE;
258 /* last refcount, unset access_mode */
259 if ((newstate & LOCK_FLAG_MASK) == access_mode)
260 newstate &= ~LOCK_FLAG_MASK;
262 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
267 * gst_mini_object_is_writable:
268 * @mini_object: the mini-object to check
270 * If @mini_object has the LOCKABLE flag set, check if the current EXCLUSIVE
271 * lock on @object is the only one, this means that changes to the object will
272 * not be visible to any other object.
274 * If the LOCKABLE flag is not set, check if the refcount of @mini_object is
275 * exactly 1, meaning that no other reference exists to the object and that the
276 * object is therefore writable.
278 * Modification of a mini-object should only be done after verifying that it
281 * Returns: TRUE if the object is writable.
284 gst_mini_object_is_writable (const GstMiniObject * mini_object)
288 g_return_val_if_fail (mini_object != NULL, FALSE);
290 if (GST_MINI_OBJECT_IS_LOCKABLE (mini_object)) {
291 result = !IS_SHARED (g_atomic_int_get (&mini_object->lockstate));
293 result = (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
299 * gst_mini_object_make_writable:
300 * @mini_object: (transfer full): the mini-object to make writable
302 * Checks if a mini-object is writable. If not, a writable copy is made and
303 * returned. This gives away the reference to the original mini object,
304 * and returns a reference to the new object.
308 * Returns: (transfer full): a mini-object (possibly the same pointer) that
312 gst_mini_object_make_writable (GstMiniObject * mini_object)
316 g_return_val_if_fail (mini_object != NULL, NULL);
318 if (gst_mini_object_is_writable (mini_object)) {
321 ret = gst_mini_object_copy (mini_object);
322 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
323 g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
324 gst_mini_object_unref (mini_object);
331 * gst_mini_object_ref:
332 * @mini_object: the mini-object
334 * Increase the reference count of the mini-object.
336 * Note that the refcount affects the writeability
337 * of @mini-object, see gst_mini_object_is_writable(). It is
338 * important to note that keeping additional references to
339 * GstMiniObject instances can potentially increase the number
340 * of memcpy operations in a pipeline, especially if the miniobject
343 * Returns: (transfer full): the mini-object.
346 gst_mini_object_ref (GstMiniObject * mini_object)
348 g_return_val_if_fail (mini_object != NULL, NULL);
349 /* we can't assert that the refcount > 0 since the _free functions
350 * increments the refcount from 0 to 1 again to allow resurecting
352 g_return_val_if_fail (mini_object->refcount > 0, NULL);
355 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
356 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
357 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
359 g_atomic_int_inc (&mini_object->refcount);
365 find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,
366 GstMiniObjectNotify notify, gpointer data)
370 for (i = 0; i < object->n_qdata; i++) {
371 if (QDATA_QUARK (object, i) == quark) {
372 /* check if we need to match the callback too */
373 if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&
374 QDATA_DATA (object, i) == data))
382 remove_notify (GstMiniObject * object, gint index)
385 if (--object->n_qdata == 0) {
386 /* we don't shrink but free when everything is gone */
387 g_free (object->qdata);
388 object->qdata = NULL;
389 } else if (index != object->n_qdata)
390 QDATA (object, index) = QDATA (object, object->n_qdata);
394 set_notify (GstMiniObject * object, gint index, GQuark quark,
395 GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)
399 index = object->n_qdata++;
401 g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);
403 QDATA_QUARK (object, index) = quark;
404 QDATA_NOTIFY (object, index) = notify;
405 QDATA_DATA (object, index) = data;
406 QDATA_DESTROY (object, index) = destroy;
410 call_finalize_notify (GstMiniObject * obj)
414 for (i = 0; i < obj->n_qdata; i++) {
415 if (QDATA_QUARK (obj, i) == weak_ref_quark)
416 QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);
417 if (QDATA_DESTROY (obj, i))
418 QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));
423 * gst_mini_object_unref:
424 * @mini_object: the mini-object
426 * Decreases the reference count of the mini-object, possibly freeing
430 gst_mini_object_unref (GstMiniObject * mini_object)
432 g_return_if_fail (mini_object != NULL);
434 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
436 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
437 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
439 g_return_if_fail (mini_object->refcount > 0);
441 if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
444 if (mini_object->dispose)
445 do_free = mini_object->dispose (mini_object);
449 /* if the subclass recycled the object (and returned FALSE) we don't
450 * want to free the instance anymore */
451 if (G_LIKELY (do_free)) {
452 /* there should be no outstanding locks */
453 g_return_if_fail ((g_atomic_int_get (&mini_object->lockstate) & LOCK_MASK)
456 if (mini_object->n_qdata) {
457 call_finalize_notify (mini_object);
458 g_free (mini_object->qdata);
460 #ifndef GST_DISABLE_TRACE
461 _gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
463 if (mini_object->free)
464 mini_object->free (mini_object);
470 * gst_mini_object_replace:
471 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
473 * @newdata: pointer to new mini-object
475 * Atomically modifies a pointer to point to a new mini-object.
476 * The reference count of @olddata is decreased and the reference count of
477 * @newdata is increased.
479 * Either @newdata and the value pointed to by @olddata may be NULL.
481 * Returns: TRUE if @newdata was different from @olddata
484 gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
486 GstMiniObject *olddata_val;
488 g_return_val_if_fail (olddata != NULL, FALSE);
490 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
491 *olddata, *olddata ? (*olddata)->refcount : 0,
492 newdata, newdata ? newdata->refcount : 0);
494 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
496 if (G_UNLIKELY (olddata_val == newdata))
500 gst_mini_object_ref (newdata);
502 while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
503 olddata, olddata_val, newdata))) {
504 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
505 if (G_UNLIKELY (olddata_val == newdata))
510 gst_mini_object_unref (olddata_val);
512 return olddata_val != newdata;
516 * gst_mini_object_steal:
517 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
520 * Replace the current #GstMiniObject pointer to by @olddata with NULL and
521 * return the old value.
523 * Returns: the #GstMiniObject at @oldata
526 gst_mini_object_steal (GstMiniObject ** olddata)
528 GstMiniObject *olddata_val;
530 g_return_val_if_fail (olddata != NULL, NULL);
532 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",
533 *olddata, *olddata ? (*olddata)->refcount : 0);
536 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
537 if (olddata_val == NULL)
539 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
540 olddata, olddata_val, NULL)));
546 * gst_mini_object_take:
547 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
549 * @newdata: pointer to new mini-object
551 * Modifies a pointer to point to a new mini-object. The modification
552 * is done atomically. This version is similar to gst_mini_object_replace()
553 * except that it does not increase the refcount of @newdata and thus
554 * takes ownership of @newdata.
556 * Either @newdata and the value pointed to by @olddata may be NULL.
558 * Returns: TRUE if @newdata was different from @olddata
561 gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)
563 GstMiniObject *olddata_val;
565 g_return_val_if_fail (olddata != NULL, FALSE);
567 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",
568 *olddata, *olddata ? (*olddata)->refcount : 0,
569 newdata, newdata ? newdata->refcount : 0);
572 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
573 if (G_UNLIKELY (olddata_val == newdata))
575 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
576 olddata, olddata_val, newdata)));
579 gst_mini_object_unref (olddata_val);
581 return olddata_val != newdata;
585 * gst_mini_object_weak_ref: (skip)
586 * @object: #GstMiniObject to reference weakly
587 * @notify: callback to invoke before the mini object is freed
588 * @data: extra data to pass to notify
590 * Adds a weak reference callback to a mini object. Weak references are
591 * used for notification when a mini object is finalized. They are called
592 * "weak references" because they allow you to safely hold a pointer
593 * to the mini object without calling gst_mini_object_ref()
594 * (gst_mini_object_ref() adds a strong reference, that is, forces the object
598 gst_mini_object_weak_ref (GstMiniObject * object,
599 GstMiniObjectNotify notify, gpointer data)
601 g_return_if_fail (object != NULL);
602 g_return_if_fail (notify != NULL);
603 g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);
605 G_LOCK (qdata_mutex);
606 set_notify (object, -1, weak_ref_quark, notify, data, NULL);
607 G_UNLOCK (qdata_mutex);
611 * gst_mini_object_weak_unref: (skip)
612 * @object: #GstMiniObject to remove a weak reference from
613 * @notify: callback to search for
614 * @data: data to search for
616 * Removes a weak reference callback from a mini object.
619 gst_mini_object_weak_unref (GstMiniObject * object,
620 GstMiniObjectNotify notify, gpointer data)
624 g_return_if_fail (object != NULL);
625 g_return_if_fail (notify != NULL);
627 G_LOCK (qdata_mutex);
628 if ((i = find_notify (object, weak_ref_quark, TRUE, notify, data)) != -1) {
629 remove_notify (object, i);
631 g_warning ("%s: couldn't find weak ref %p(%p)", G_STRFUNC, notify, data);
633 G_UNLOCK (qdata_mutex);
637 * gst_mini_object_set_qdata:
638 * @object: a #GstMiniObject
639 * @quark: A #GQuark, naming the user data pointer
640 * @data: An opaque user data pointer
641 * @destroy: Function to invoke with @data as argument, when @data
644 * This sets an opaque, named pointer on a miniobject.
645 * The name is specified through a #GQuark (retrived e.g. via
646 * g_quark_from_static_string()), and the pointer
647 * can be gotten back from the @object with gst_mini_object_get_qdata()
648 * until the @object is disposed.
649 * Setting a previously set user data pointer, overrides (frees)
650 * the old pointer set, using #NULL as pointer essentially
651 * removes the data stored.
653 * @destroy may be specified which is called with @data as argument
654 * when the @object is disposed, or the data is being overwritten by
655 * a call to gst_mini_object_set_qdata() with the same @quark.
658 gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,
659 gpointer data, GDestroyNotify destroy)
662 gpointer old_data = NULL;
663 GDestroyNotify old_notify = NULL;
665 g_return_if_fail (object != NULL);
666 g_return_if_fail (quark > 0);
668 G_LOCK (qdata_mutex);
669 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
671 old_data = QDATA_DATA (object, i);
672 old_notify = QDATA_DESTROY (object, i);
675 remove_notify (object, i);
678 set_notify (object, i, quark, NULL, data, destroy);
679 G_UNLOCK (qdata_mutex);
682 old_notify (old_data);
686 * gst_mini_object_get_qdata:
687 * @object: The GstMiniObject to get a stored user data pointer from
688 * @quark: A #GQuark, naming the user data pointer
690 * This function gets back user data pointers stored via
691 * gst_mini_object_set_qdata().
693 * Returns: (transfer none): The user data pointer set, or %NULL
696 gst_mini_object_get_qdata (GstMiniObject * object, GQuark quark)
701 g_return_val_if_fail (object != NULL, NULL);
702 g_return_val_if_fail (quark > 0, NULL);
704 G_LOCK (qdata_mutex);
705 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1)
706 result = QDATA_DATA (object, i);
709 G_UNLOCK (qdata_mutex);
715 * gst_mini_object_steal_qdata:
716 * @object: The GstMiniObject to get a stored user data pointer from
717 * @quark: A #GQuark, naming the user data pointer
719 * This function gets back user data pointers stored via gst_mini_object_set_qdata()
720 * and removes the data from @object without invoking its destroy() function (if
723 * Returns: (transfer full): The user data pointer set, or %NULL
726 gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)
731 g_return_val_if_fail (object != NULL, NULL);
732 g_return_val_if_fail (quark > 0, NULL);
734 G_LOCK (qdata_mutex);
735 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
736 result = QDATA_DATA (object, i);
737 remove_notify (object, i);
741 G_UNLOCK (qdata_mutex);