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., 51 Franklin St, Fifth Floor,
19 * Boston, MA 02110-1301, USA.
22 * SECTION:gstminiobject
23 * @title: GstMiniObject
24 * @short_description: Lightweight base class for the GStreamer object hierarchy
26 * #GstMiniObject is a simple structure that can be used to implement refcounted
29 * Subclasses will include #GstMiniObject as the first member in their structure
30 * and then call gst_mini_object_init() to initialize the #GstMiniObject fields.
32 * gst_mini_object_ref() and gst_mini_object_unref() increment and decrement the
33 * refcount respectively. When the refcount of a mini-object reaches 0, the
34 * dispose function is called first and when this returns %TRUE, the free
35 * function of the miniobject is called.
37 * A copy can be made with gst_mini_object_copy().
39 * gst_mini_object_is_writable() will return %TRUE when the refcount of the
40 * object is exactly 1, meaning the current caller has the only reference to the
41 * object. gst_mini_object_make_writable() will return a writable version of the
42 * object, which might be a new copy when the refcount was not 1.
44 * Opaque data can be associated with a #GstMiniObject with
45 * gst_mini_object_set_qdata() and gst_mini_object_get_qdata(). The data is
46 * meant to be specific to the particular object and is not automatically copied
47 * with gst_mini_object_copy() or similar methods.
49 * A weak reference can be added and remove with gst_mini_object_weak_ref()
50 * and gst_mini_object_weak_unref() respectively.
56 #include "gst/gst_private.h"
57 #include "gst/gstminiobject.h"
58 #include "gst/gstinfo.h"
59 #include <gobject/gvaluecollector.h>
61 /* Mutex used for weak referencing */
62 G_LOCK_DEFINE_STATIC (qdata_mutex);
63 static GQuark weak_ref_quark;
65 #define SHARE_ONE (1 << 16)
66 #define SHARE_TWO (2 << 16)
67 #define SHARE_MASK (~(SHARE_ONE - 1))
68 #define IS_SHARED(state) (state >= SHARE_TWO)
69 #define LOCK_ONE (GST_LOCK_FLAG_LAST)
70 #define FLAG_MASK (GST_LOCK_FLAG_LAST - 1)
71 #define LOCK_MASK ((SHARE_ONE - 1) - FLAG_MASK)
72 #define LOCK_FLAG_MASK (SHARE_ONE - 1)
77 GstMiniObjectNotify notify;
79 GDestroyNotify destroy;
82 #define QDATA(o,i) ((GstQData *)(o)->qdata)[(i)]
83 #define QDATA_QUARK(o,i) (QDATA(o,i).quark)
84 #define QDATA_NOTIFY(o,i) (QDATA(o,i).notify)
85 #define QDATA_DATA(o,i) (QDATA(o,i).data)
86 #define QDATA_DESTROY(o,i) (QDATA(o,i).destroy)
89 _priv_gst_mini_object_initialize (void)
91 weak_ref_quark = g_quark_from_static_string ("GstMiniObjectWeakRefQuark");
95 * gst_mini_object_init: (skip)
96 * @mini_object: a #GstMiniObject
97 * @flags: initial #GstMiniObjectFlags
98 * @type: the #GType of the mini-object to create
99 * @copy_func: (allow-none): the copy function, or %NULL
100 * @dispose_func: (allow-none): the dispose function, or %NULL
101 * @free_func: (allow-none): the free function or %NULL
103 * Initializes a mini-object with the desired type and copy/dispose/free
107 gst_mini_object_init (GstMiniObject * mini_object, guint flags, GType type,
108 GstMiniObjectCopyFunction copy_func,
109 GstMiniObjectDisposeFunction dispose_func,
110 GstMiniObjectFreeFunction free_func)
112 mini_object->type = type;
113 mini_object->refcount = 1;
114 mini_object->lockstate = 0;
115 mini_object->flags = flags;
117 mini_object->copy = copy_func;
118 mini_object->dispose = dispose_func;
119 mini_object->free = free_func;
121 mini_object->n_qdata = 0;
122 mini_object->qdata = NULL;
124 GST_TRACER_MINI_OBJECT_CREATED (mini_object);
128 * gst_mini_object_copy: (skip)
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_lock:
154 * @object: the mini-object to lock
155 * @flags: #GstLockFlags
157 * Lock the mini-object with the specified access mode in @flags.
159 * Returns: %TRUE if @object could be locked.
162 gst_mini_object_lock (GstMiniObject * object, GstLockFlags flags)
164 gint access_mode, state, newstate;
166 g_return_val_if_fail (object != NULL, FALSE);
167 g_return_val_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object), FALSE);
169 if (G_UNLIKELY (object->flags & GST_MINI_OBJECT_FLAG_LOCK_READONLY &&
170 flags & GST_LOCK_FLAG_WRITE))
174 access_mode = flags & FLAG_MASK;
175 newstate = state = g_atomic_int_get (&object->lockstate);
177 GST_CAT_TRACE (GST_CAT_LOCKING, "lock %p: state %08x, access_mode %d",
178 object, state, access_mode);
180 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
182 newstate += SHARE_ONE;
183 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
186 /* shared counter > 1 and write access is not allowed */
187 if (((state & GST_LOCK_FLAG_WRITE) != 0
188 || (access_mode & GST_LOCK_FLAG_WRITE) != 0)
189 && IS_SHARED (newstate))
193 if ((state & LOCK_FLAG_MASK) == 0) {
194 /* nothing mapped, set access_mode */
195 newstate |= access_mode;
197 /* access_mode must match */
198 if ((state & access_mode) != access_mode)
201 /* increase refcount */
202 newstate += LOCK_ONE;
204 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
211 GST_CAT_DEBUG (GST_CAT_LOCKING,
212 "lock failed %p: state %08x, access_mode %d", object, state,
219 * gst_mini_object_unlock:
220 * @object: the mini-object to unlock
221 * @flags: #GstLockFlags
223 * Unlock the mini-object with the specified access mode in @flags.
226 gst_mini_object_unlock (GstMiniObject * object, GstLockFlags flags)
228 gint access_mode, state, newstate;
230 g_return_if_fail (object != NULL);
231 g_return_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object));
234 access_mode = flags & FLAG_MASK;
235 newstate = state = g_atomic_int_get (&object->lockstate);
237 GST_CAT_TRACE (GST_CAT_LOCKING, "unlock %p: state %08x, access_mode %d",
238 object, state, access_mode);
240 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
242 g_return_if_fail (state >= SHARE_ONE);
243 newstate -= SHARE_ONE;
244 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
248 g_return_if_fail ((state & access_mode) == access_mode);
249 /* decrease the refcount */
250 newstate -= LOCK_ONE;
251 /* last refcount, unset access_mode */
252 if ((newstate & LOCK_FLAG_MASK) == access_mode)
253 newstate &= ~LOCK_FLAG_MASK;
255 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
260 * gst_mini_object_is_writable:
261 * @mini_object: the mini-object to check
263 * If @mini_object has the LOCKABLE flag set, check if the current EXCLUSIVE
264 * lock on @object is the only one, this means that changes to the object will
265 * not be visible to any other object.
267 * If the LOCKABLE flag is not set, check if the refcount of @mini_object is
268 * exactly 1, meaning that no other reference exists to the object and that the
269 * object is therefore writable.
271 * Modification of a mini-object should only be done after verifying that it
274 * Returns: %TRUE if the object is writable.
277 gst_mini_object_is_writable (const GstMiniObject * mini_object)
281 g_return_val_if_fail (mini_object != NULL, FALSE);
283 if (GST_MINI_OBJECT_IS_LOCKABLE (mini_object)) {
284 result = !IS_SHARED (g_atomic_int_get (&mini_object->lockstate));
286 result = (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
292 * gst_mini_object_make_writable: (skip)
293 * @mini_object: (transfer full): the mini-object to make writable
295 * Checks if a mini-object is writable. If not, a writable copy is made and
296 * returned. This gives away the reference to the original mini object,
297 * and returns a reference to the new object.
301 * Returns: (transfer full): a mini-object (possibly the same pointer) that
305 gst_mini_object_make_writable (GstMiniObject * mini_object)
309 g_return_val_if_fail (mini_object != NULL, NULL);
311 if (gst_mini_object_is_writable (mini_object)) {
314 ret = gst_mini_object_copy (mini_object);
315 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
316 g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
317 gst_mini_object_unref (mini_object);
324 * gst_mini_object_ref: (skip)
325 * @mini_object: the mini-object
327 * Increase the reference count of the mini-object.
329 * Note that the refcount affects the writability
330 * of @mini-object, see gst_mini_object_is_writable(). It is
331 * important to note that keeping additional references to
332 * GstMiniObject instances can potentially increase the number
333 * of memcpy operations in a pipeline, especially if the miniobject
336 * Returns: (transfer full): the mini-object.
339 gst_mini_object_ref (GstMiniObject * mini_object)
341 gint old_refcount, new_refcount;
343 g_return_val_if_fail (mini_object != NULL, NULL);
344 /* we can't assert that the refcount > 0 since the _free functions
345 * increments the refcount from 0 to 1 again to allow resurecting
347 g_return_val_if_fail (mini_object->refcount > 0, NULL);
350 old_refcount = g_atomic_int_add (&mini_object->refcount, 1);
351 new_refcount = old_refcount + 1;
353 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
354 old_refcount, new_refcount);
356 GST_TRACER_MINI_OBJECT_REFFED (mini_object, new_refcount);
362 find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,
363 GstMiniObjectNotify notify, gpointer data)
367 for (i = 0; i < object->n_qdata; i++) {
368 if (QDATA_QUARK (object, i) == quark) {
369 /* check if we need to match the callback too */
370 if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&
371 QDATA_DATA (object, i) == data))
379 remove_notify (GstMiniObject * object, gint index)
382 if (--object->n_qdata == 0) {
383 /* we don't shrink but free when everything is gone */
384 g_free (object->qdata);
385 object->qdata = NULL;
386 } else if (index != object->n_qdata)
387 QDATA (object, index) = QDATA (object, object->n_qdata);
391 set_notify (GstMiniObject * object, gint index, GQuark quark,
392 GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)
396 index = object->n_qdata++;
398 g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);
400 QDATA_QUARK (object, index) = quark;
401 QDATA_NOTIFY (object, index) = notify;
402 QDATA_DATA (object, index) = data;
403 QDATA_DESTROY (object, index) = destroy;
407 call_finalize_notify (GstMiniObject * obj)
411 for (i = 0; i < obj->n_qdata; i++) {
412 if (QDATA_QUARK (obj, i) == weak_ref_quark)
413 QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);
414 if (QDATA_DESTROY (obj, i))
415 QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));
420 * gst_mini_object_unref: (skip)
421 * @mini_object: the mini-object
423 * Decreases the reference count of the mini-object, possibly freeing
427 gst_mini_object_unref (GstMiniObject * mini_object)
429 gint old_refcount, new_refcount;
431 g_return_if_fail (mini_object != NULL);
433 old_refcount = g_atomic_int_add (&mini_object->refcount, -1);
434 new_refcount = old_refcount - 1;
436 g_return_if_fail (old_refcount > 0);
438 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
439 mini_object, old_refcount, new_refcount);
441 GST_TRACER_MINI_OBJECT_UNREFFED (mini_object, new_refcount);
443 if (new_refcount == 0) {
446 if (mini_object->dispose)
447 do_free = mini_object->dispose (mini_object);
451 /* if the subclass recycled the object (and returned FALSE) we don't
452 * want to free the instance anymore */
453 if (G_LIKELY (do_free)) {
454 /* there should be no outstanding locks */
455 g_return_if_fail ((g_atomic_int_get (&mini_object->lockstate) & LOCK_MASK)
458 if (mini_object->n_qdata) {
459 call_finalize_notify (mini_object);
460 g_free (mini_object->qdata);
462 GST_TRACER_MINI_OBJECT_DESTROYED (mini_object);
463 if (mini_object->free)
464 mini_object->free (mini_object);
470 * gst_mini_object_replace:
471 * @olddata: (inout) (transfer full) (nullable): pointer to a pointer to a
472 * mini-object to be replaced
473 * @newdata: (allow-none): 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: (skip)
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 (object:%p data:%p)", G_STRFUNC,
632 notify, object, data);
634 G_UNLOCK (qdata_mutex);
638 * gst_mini_object_set_qdata:
639 * @object: a #GstMiniObject
640 * @quark: A #GQuark, naming the user data pointer
641 * @data: An opaque user data pointer
642 * @destroy: Function to invoke with @data as argument, when @data
645 * This sets an opaque, named pointer on a miniobject.
646 * The name is specified through a #GQuark (retrieved e.g. via
647 * g_quark_from_static_string()), and the pointer
648 * can be gotten back from the @object with gst_mini_object_get_qdata()
649 * until the @object is disposed.
650 * Setting a previously set user data pointer, overrides (frees)
651 * the old pointer set, using %NULL as pointer essentially
652 * removes the data stored.
654 * @destroy may be specified which is called with @data as argument
655 * when the @object is disposed, or the data is being overwritten by
656 * a call to gst_mini_object_set_qdata() with the same @quark.
659 gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,
660 gpointer data, GDestroyNotify destroy)
663 gpointer old_data = NULL;
664 GDestroyNotify old_notify = NULL;
666 g_return_if_fail (object != NULL);
667 g_return_if_fail (quark > 0);
669 G_LOCK (qdata_mutex);
670 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
672 old_data = QDATA_DATA (object, i);
673 old_notify = QDATA_DESTROY (object, i);
676 remove_notify (object, i);
679 set_notify (object, i, quark, NULL, data, destroy);
680 G_UNLOCK (qdata_mutex);
683 old_notify (old_data);
687 * gst_mini_object_get_qdata:
688 * @object: The GstMiniObject to get a stored user data pointer from
689 * @quark: A #GQuark, naming the user data pointer
691 * This function gets back user data pointers stored via
692 * gst_mini_object_set_qdata().
694 * Returns: (transfer none) (nullable): The user data pointer set, or
698 gst_mini_object_get_qdata (GstMiniObject * object, GQuark quark)
703 g_return_val_if_fail (object != NULL, NULL);
704 g_return_val_if_fail (quark > 0, NULL);
706 G_LOCK (qdata_mutex);
707 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1)
708 result = QDATA_DATA (object, i);
711 G_UNLOCK (qdata_mutex);
717 * gst_mini_object_steal_qdata:
718 * @object: The GstMiniObject to get a stored user data pointer from
719 * @quark: A #GQuark, naming the user data pointer
721 * This function gets back user data pointers stored via gst_mini_object_set_qdata()
722 * and removes the data from @object without invoking its destroy() function (if
725 * Returns: (transfer full) (nullable): The user data pointer set, or
729 gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)
734 g_return_val_if_fail (object != NULL, NULL);
735 g_return_val_if_fail (quark > 0, NULL);
737 G_LOCK (qdata_mutex);
738 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
739 result = QDATA_DATA (object, i);
740 remove_notify (object, i);
744 G_UNLOCK (qdata_mutex);