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_MASK (~(SHARE_ONE - 1))
73 #define LOCK_ONE (GST_LOCK_FLAG_LAST)
74 #define FLAG_MASK (GST_LOCK_FLAG_LAST - 1)
75 #define LOCK_MASK ((SHARE_ONE - 1) - FLAG_MASK)
76 #define LOCK_FLAG_MASK (SHARE_ONE - 1)
81 GstMiniObjectNotify notify;
83 GDestroyNotify destroy;
86 #define QDATA(o,i) ((GstQData *)(o)->qdata)[(i)]
87 #define QDATA_QUARK(o,i) (QDATA(o,i).quark)
88 #define QDATA_NOTIFY(o,i) (QDATA(o,i).notify)
89 #define QDATA_DATA(o,i) (QDATA(o,i).data)
90 #define QDATA_DESTROY(o,i) (QDATA(o,i).destroy)
93 _priv_gst_mini_object_initialize (void)
95 weak_ref_quark = g_quark_from_static_string ("GstMiniObjectWeakRefQuark");
97 #ifndef GST_DISABLE_TRACE
98 _gst_mini_object_trace = _gst_alloc_trace_register ("GstMiniObject", 0);
103 * gst_mini_object_init: (skip)
104 * @mini_object: a #GstMiniObject
105 * @type: the #GType of the mini-object to create
106 * @copy_func: the copy function, or NULL
107 * @dispose_func: the dispose function, or NULL
108 * @free_func: the free function or NULL
110 * Initializes a mini-object with the desired type and copy/dispose/free
114 gst_mini_object_init (GstMiniObject * mini_object, guint flags, GType type,
115 GstMiniObjectCopyFunction copy_func,
116 GstMiniObjectDisposeFunction dispose_func,
117 GstMiniObjectFreeFunction free_func)
119 mini_object->type = type;
120 mini_object->refcount = 1;
121 mini_object->lockstate =
122 (flags & GST_MINI_OBJECT_FLAG_LOCK_READONLY ? GST_LOCK_FLAG_READ : 0);
123 mini_object->flags = flags;
125 mini_object->copy = copy_func;
126 mini_object->dispose = dispose_func;
127 mini_object->free = free_func;
129 mini_object->n_qdata = 0;
130 mini_object->qdata = NULL;
132 #ifndef GST_DISABLE_TRACE
133 _gst_alloc_trace_new (_gst_mini_object_trace, mini_object);
138 * gst_mini_object_copy:
139 * @mini_object: the mini-object to copy
141 * Creates a copy of the mini-object.
145 * Returns: (transfer full): the new mini-object.
148 gst_mini_object_copy (const GstMiniObject * mini_object)
152 g_return_val_if_fail (mini_object != NULL, NULL);
154 if (mini_object->copy)
155 copy = mini_object->copy (mini_object);
163 * gst_mini_object_lock:
164 * @object: the mini-object to lock
165 * @flags: #GstLockFlags
167 * Lock the mini-object with the specified access mode in @flags.
169 * Returns: %TRUE if @object could be locked.
172 gst_mini_object_lock (GstMiniObject * object, GstLockFlags flags)
174 gint access_mode, state, newstate;
176 g_return_val_if_fail (object != NULL, FALSE);
177 g_return_val_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object), FALSE);
179 access_mode = flags & FLAG_MASK;
182 newstate = state = g_atomic_int_get (&object->lockstate);
184 GST_CAT_TRACE (GST_CAT_LOCKING, "lock %p: state %08x, access_mode %d",
185 object, state, access_mode);
187 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
189 newstate += SHARE_ONE;
190 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
194 if ((state & LOCK_FLAG_MASK) == 0) {
195 /* shared counter > 1 and write access */
196 if (state > SHARE_ONE && access_mode & GST_LOCK_FLAG_WRITE)
198 /* nothing mapped, set access_mode */
199 newstate |= access_mode;
201 /* access_mode must match */
202 if ((state & access_mode) != access_mode)
205 /* increase refcount */
206 newstate += LOCK_ONE;
208 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
215 GST_CAT_DEBUG (GST_CAT_LOCKING,
216 "lock failed %p: state %08x, access_mode %d", object, state,
223 * gst_mini_object_unlock:
224 * @object: the mini-object to unlock
225 * @flags: #GstLockFlags
227 * Unlock the mini-object with the specified access mode in @flags.
230 gst_mini_object_unlock (GstMiniObject * object, GstLockFlags flags)
232 gint access_mode, state, newstate;
234 g_return_if_fail (object != NULL);
235 g_return_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object));
237 access_mode = flags & FLAG_MASK;
240 newstate = state = g_atomic_int_get (&object->lockstate);
242 GST_CAT_TRACE (GST_CAT_LOCKING, "unlock %p: state %08x, access_mode %d",
243 object, state, access_mode);
245 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
247 g_return_if_fail (state >= SHARE_ONE);
248 newstate -= SHARE_ONE;
249 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
253 g_return_if_fail ((state & access_mode) == access_mode);
254 /* decrease the refcount */
255 newstate -= LOCK_ONE;
256 /* last refcount, unset access_mode */
257 if ((newstate & LOCK_FLAG_MASK) == access_mode)
258 newstate &= ~LOCK_FLAG_MASK;
260 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
265 * gst_mini_object_is_writable:
266 * @mini_object: the mini-object to check
268 * If @mini_object has the LOCKABLE flag set, check if the current EXCLUSIVE
269 * lock on @object is the only one, this means that changes to the object will
270 * not be visible to any other object.
272 * If the LOCKABLE flag is not set, check if the refcount of @mini_object is
273 * exactly 1, meaning that no other reference exists to the object and that the
274 * object is therefore writable.
276 * Modification of a mini-object should only be done after verifying that it
279 * Returns: TRUE if the object is writable.
282 gst_mini_object_is_writable (const GstMiniObject * mini_object)
286 g_return_val_if_fail (mini_object != NULL, FALSE);
288 if (GST_MINI_OBJECT_IS_LOCKABLE (mini_object)) {
289 result = (g_atomic_int_get (&mini_object->lockstate) & SHARE_MASK) < 2;
291 result = (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
297 * gst_mini_object_make_writable:
298 * @mini_object: (transfer full): the mini-object to make writable
300 * Checks if a mini-object is writable. If not, a writable copy is made and
301 * returned. This gives away the reference to the original mini object,
302 * and returns a reference to the new object.
306 * Returns: (transfer full): a mini-object (possibly the same pointer) that
310 gst_mini_object_make_writable (GstMiniObject * mini_object)
314 g_return_val_if_fail (mini_object != NULL, NULL);
316 if (gst_mini_object_is_writable (mini_object)) {
319 ret = gst_mini_object_copy (mini_object);
320 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
321 g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
322 gst_mini_object_unref (mini_object);
329 * gst_mini_object_ref:
330 * @mini_object: the mini-object
332 * Increase the reference count of the mini-object.
334 * Note that the refcount affects the writeability
335 * of @mini-object, see gst_mini_object_is_writable(). It is
336 * important to note that keeping additional references to
337 * GstMiniObject instances can potentially increase the number
338 * of memcpy operations in a pipeline, especially if the miniobject
341 * Returns: (transfer full): the mini-object.
344 gst_mini_object_ref (GstMiniObject * mini_object)
346 g_return_val_if_fail (mini_object != NULL, NULL);
347 /* we can't assert that the refcount > 0 since the _free functions
348 * increments the refcount from 0 to 1 again to allow resurecting
350 g_return_val_if_fail (mini_object->refcount > 0, NULL);
353 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
354 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
355 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
357 g_atomic_int_inc (&mini_object->refcount);
363 find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,
364 GstMiniObjectNotify notify, gpointer data)
368 for (i = 0; i < object->n_qdata; i++) {
369 if (QDATA_QUARK (object, i) == quark) {
370 /* check if we need to match the callback too */
371 if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&
372 QDATA_DATA (object, i) == data))
380 remove_notify (GstMiniObject * object, gint index)
383 if (--object->n_qdata == 0) {
384 /* we don't shrink but free when everything is gone */
385 g_free (object->qdata);
386 object->qdata = NULL;
387 } else if (index != object->n_qdata)
388 QDATA (object, index) = QDATA (object, object->n_qdata);
392 set_notify (GstMiniObject * object, gint index, GQuark quark,
393 GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)
397 index = object->n_qdata++;
399 g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);
401 QDATA_QUARK (object, index) = quark;
402 QDATA_NOTIFY (object, index) = notify;
403 QDATA_DATA (object, index) = data;
404 QDATA_DESTROY (object, index) = destroy;
408 call_finalize_notify (GstMiniObject * obj)
412 for (i = 0; i < obj->n_qdata; i++) {
413 if (QDATA_QUARK (obj, i) == weak_ref_quark)
414 QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);
415 if (QDATA_DESTROY (obj, i))
416 QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));
421 * gst_mini_object_unref:
422 * @mini_object: the mini-object
424 * Decreases the reference count of the mini-object, possibly freeing
428 gst_mini_object_unref (GstMiniObject * mini_object)
430 g_return_if_fail (mini_object != NULL);
432 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
434 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
435 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
437 g_return_if_fail (mini_object->refcount > 0);
439 if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
442 if (mini_object->dispose)
443 do_free = mini_object->dispose (mini_object);
447 /* if the subclass recycled the object (and returned FALSE) we don't
448 * want to free the instance anymore */
449 if (G_LIKELY (do_free)) {
450 /* there should be no outstanding locks */
451 g_return_if_fail ((g_atomic_int_get (&mini_object->lockstate) & LOCK_MASK)
454 if (mini_object->n_qdata) {
455 call_finalize_notify (mini_object);
456 g_free (mini_object->qdata);
458 #ifndef GST_DISABLE_TRACE
459 _gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
461 if (mini_object->free)
462 mini_object->free (mini_object);
468 * gst_mini_object_replace:
469 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
471 * @newdata: pointer to new mini-object
473 * Atomically modifies a pointer to point to a new mini-object.
474 * The reference count of @olddata is decreased and the reference count of
475 * @newdata is increased.
477 * Either @newdata and the value pointed to by @olddata may be NULL.
479 * Returns: TRUE if @newdata was different from @olddata
482 gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
484 GstMiniObject *olddata_val;
486 g_return_val_if_fail (olddata != NULL, FALSE);
488 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
489 *olddata, *olddata ? (*olddata)->refcount : 0,
490 newdata, newdata ? newdata->refcount : 0);
492 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
494 if (G_UNLIKELY (olddata_val == newdata))
498 gst_mini_object_ref (newdata);
500 while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
501 olddata, olddata_val, newdata))) {
502 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
503 if (G_UNLIKELY (olddata_val == newdata))
508 gst_mini_object_unref (olddata_val);
510 return olddata_val != newdata;
514 * gst_mini_object_steal:
515 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
518 * Replace the current #GstMiniObject pointer to by @olddata with NULL and
519 * return the old value.
521 * Returns: the #GstMiniObject at @oldata
524 gst_mini_object_steal (GstMiniObject ** olddata)
526 GstMiniObject *olddata_val;
528 g_return_val_if_fail (olddata != NULL, NULL);
530 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",
531 *olddata, *olddata ? (*olddata)->refcount : 0);
534 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
535 if (olddata_val == NULL)
537 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
538 olddata, olddata_val, NULL)));
544 * gst_mini_object_take:
545 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
547 * @newdata: pointer to new mini-object
549 * Modifies a pointer to point to a new mini-object. The modification
550 * is done atomically. This version is similar to gst_mini_object_replace()
551 * except that it does not increase the refcount of @newdata and thus
552 * takes ownership of @newdata.
554 * Either @newdata and the value pointed to by @olddata may be NULL.
556 * Returns: TRUE if @newdata was different from @olddata
559 gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)
561 GstMiniObject *olddata_val;
563 g_return_val_if_fail (olddata != NULL, FALSE);
565 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",
566 *olddata, *olddata ? (*olddata)->refcount : 0,
567 newdata, newdata ? newdata->refcount : 0);
570 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
571 if (G_UNLIKELY (olddata_val == newdata))
573 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
574 olddata, olddata_val, newdata)));
577 gst_mini_object_unref (olddata_val);
579 return olddata_val != newdata;
583 * gst_mini_object_weak_ref: (skip)
584 * @object: #GstMiniObject to reference weakly
585 * @notify: callback to invoke before the mini object is freed
586 * @data: extra data to pass to notify
588 * Adds a weak reference callback to a mini object. Weak references are
589 * used for notification when a mini object is finalized. They are called
590 * "weak references" because they allow you to safely hold a pointer
591 * to the mini object without calling gst_mini_object_ref()
592 * (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.
621 gst_mini_object_weak_unref (GstMiniObject * object,
622 GstMiniObjectNotify notify, gpointer data)
626 g_return_if_fail (object != NULL);
627 g_return_if_fail (notify != NULL);
629 G_LOCK (qdata_mutex);
630 if ((i = find_notify (object, weak_ref_quark, TRUE, notify, data)) != -1) {
631 remove_notify (object, i);
633 g_warning ("%s: couldn't find weak ref %p(%p)", G_STRFUNC, notify, data);
635 G_UNLOCK (qdata_mutex);
639 * gst_mini_object_set_qdata:
640 * @object: a #GstMiniObject
641 * @quark: A #GQuark, naming the user data pointer
642 * @data: An opaque user data pointer
643 * @destroy: Function to invoke with @data as argument, when @data
646 * This sets an opaque, named pointer on a miniobject.
647 * The name is specified through a #GQuark (retrived e.g. via
648 * g_quark_from_static_string()), and the pointer
649 * can be gotten back from the @object with gst_mini_object_get_qdata()
650 * until the @object is disposed.
651 * Setting a previously set user data pointer, overrides (frees)
652 * the old pointer set, using #NULL as pointer essentially
653 * removes the data stored.
655 * @destroy may be specified which is called with @data as argument
656 * when the @object is disposed, or the data is being overwritten by
657 * a call to gst_mini_object_set_qdata() with the same @quark.
660 gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,
661 gpointer data, GDestroyNotify destroy)
664 gpointer old_data = NULL;
665 GDestroyNotify old_notify = NULL;
667 g_return_if_fail (object != NULL);
668 g_return_if_fail (quark > 0);
670 G_LOCK (qdata_mutex);
671 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
673 old_data = QDATA_DATA (object, i);
674 old_notify = QDATA_DESTROY (object, i);
677 remove_notify (object, i);
680 set_notify (object, i, quark, NULL, data, destroy);
681 G_UNLOCK (qdata_mutex);
684 old_notify (old_data);
688 * gst_mini_object_get_qdata:
689 * @object: The GstMiniObject to get a stored user data pointer from
690 * @quark: A #GQuark, naming the user data pointer
692 * This function gets back user data pointers stored via
693 * gst_mini_object_set_qdata().
695 * Returns: (transfer none): The user data pointer set, or %NULL
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): The user data pointer set, or %NULL
728 gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)
733 g_return_val_if_fail (object != NULL, NULL);
734 g_return_val_if_fail (quark > 0, NULL);
736 G_LOCK (qdata_mutex);
737 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
738 result = QDATA_DATA (object, i);
739 remove_notify (object, i);
743 G_UNLOCK (qdata_mutex);