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
115 * Returns: (transfer full): the new mini-object.
118 gst_mini_object_init (GstMiniObject * mini_object, guint flags, GType type,
119 GstMiniObjectCopyFunction copy_func,
120 GstMiniObjectDisposeFunction dispose_func,
121 GstMiniObjectFreeFunction free_func)
123 mini_object->type = type;
124 mini_object->refcount = 1;
125 mini_object->lockstate =
126 (flags & GST_MINI_OBJECT_FLAG_LOCK_READONLY ? GST_LOCK_FLAG_READ : 0);
127 mini_object->flags = flags;
129 mini_object->copy = copy_func;
130 mini_object->dispose = dispose_func;
131 mini_object->free = free_func;
133 mini_object->n_qdata = 0;
134 mini_object->qdata = NULL;
136 #ifndef GST_DISABLE_TRACE
137 _gst_alloc_trace_new (_gst_mini_object_trace, mini_object);
142 * gst_mini_object_copy:
143 * @mini_object: the mini-object to copy
145 * Creates a copy of the mini-object.
149 * Returns: (transfer full): the new mini-object.
152 gst_mini_object_copy (const GstMiniObject * mini_object)
156 g_return_val_if_fail (mini_object != NULL, NULL);
158 if (mini_object->copy)
159 copy = mini_object->copy (mini_object);
167 * gst_mini_object_lock:
168 * @object: the mini-object to lock
169 * @flags: #GstLockFlags
171 * Lock the mini-object with the specified access mode in @flags.
173 * Returns: %TRUE if @object could be locked.
176 gst_mini_object_lock (GstMiniObject * object, GstLockFlags flags)
178 gint access_mode, state, newstate;
180 g_return_val_if_fail (object != NULL, FALSE);
181 g_return_val_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object), FALSE);
183 access_mode = flags & FLAG_MASK;
186 newstate = state = g_atomic_int_get (&object->lockstate);
188 GST_CAT_TRACE (GST_CAT_LOCKING, "lock %p: state %08x, access_mode %d",
189 object, state, access_mode);
191 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
193 newstate += SHARE_ONE;
194 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
198 if ((state & LOCK_FLAG_MASK) == 0) {
199 /* shared counter > 1 and write access */
200 if (state > SHARE_ONE && access_mode & GST_LOCK_FLAG_WRITE)
202 /* nothing mapped, set access_mode */
203 newstate |= access_mode;
205 /* access_mode must match */
206 if ((state & access_mode) != access_mode)
209 /* increase refcount */
210 newstate += LOCK_ONE;
212 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
219 GST_CAT_DEBUG (GST_CAT_LOCKING,
220 "lock failed %p: state %08x, access_mode %d", object, state,
227 * gst_mini_object_unlock:
228 * @object: the mini-object to unlock
229 * @flags: #GstLockFlags
231 * Unlock the mini-object with the specified access mode in @flags.
234 gst_mini_object_unlock (GstMiniObject * object, GstLockFlags flags)
236 gint access_mode, state, newstate;
238 g_return_if_fail (object != NULL);
239 g_return_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object));
241 access_mode = flags & FLAG_MASK;
244 newstate = state = g_atomic_int_get (&object->lockstate);
246 GST_CAT_TRACE (GST_CAT_LOCKING, "unlock %p: state %08x, access_mode %d",
247 object, state, access_mode);
249 if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
251 g_return_if_fail (state >= SHARE_ONE);
252 newstate -= SHARE_ONE;
253 access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
257 g_return_if_fail ((state & access_mode) == access_mode);
258 /* decrease the refcount */
259 newstate -= LOCK_ONE;
260 /* last refcount, unset access_mode */
261 if ((newstate & LOCK_FLAG_MASK) == access_mode)
262 newstate &= ~LOCK_FLAG_MASK;
264 } while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
269 * gst_mini_object_is_writable:
270 * @mini_object: the mini-object to check
272 * If @mini_object has the LOCKABLE flag set, check if the current EXCLUSIVE
273 * lock on @object is the only one, this means that changes to the object will
274 * not be visible to any other object.
276 * If the LOCKABLE flag is not set, check if the refcount of @mini_object is
277 * exactly 1, meaning that no other reference exists to the object and that the
278 * object is therefore writable.
280 * Modification of a mini-object should only be done after verifying that it
283 * Returns: TRUE if the object is writable.
286 gst_mini_object_is_writable (const GstMiniObject * mini_object)
290 g_return_val_if_fail (mini_object != NULL, FALSE);
292 if (GST_MINI_OBJECT_IS_LOCKABLE (mini_object)) {
293 result = (g_atomic_int_get (&mini_object->lockstate) & SHARE_MASK) < 2;
295 result = (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
301 * gst_mini_object_make_writable:
302 * @mini_object: (transfer full): the mini-object to make writable
304 * Checks if a mini-object is writable. If not, a writable copy is made and
305 * returned. This gives away the reference to the original mini object,
306 * and returns a reference to the new object.
310 * Returns: (transfer full): a mini-object (possibly the same pointer) that
314 gst_mini_object_make_writable (GstMiniObject * mini_object)
318 g_return_val_if_fail (mini_object != NULL, NULL);
320 if (gst_mini_object_is_writable (mini_object)) {
323 ret = gst_mini_object_copy (mini_object);
324 GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
325 g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
326 gst_mini_object_unref (mini_object);
333 * gst_mini_object_ref:
334 * @mini_object: the mini-object
336 * Increase the reference count of the mini-object.
338 * Note that the refcount affects the writeability
339 * of @mini-object, see gst_mini_object_is_writable(). It is
340 * important to note that keeping additional references to
341 * GstMiniObject instances can potentially increase the number
342 * of memcpy operations in a pipeline, especially if the miniobject
345 * Returns: (transfer full): the mini-object.
348 gst_mini_object_ref (GstMiniObject * mini_object)
350 g_return_val_if_fail (mini_object != NULL, NULL);
351 /* we can't assert that the refcount > 0 since the _free functions
352 * increments the refcount from 0 to 1 again to allow resurecting
354 g_return_val_if_fail (mini_object->refcount > 0, NULL);
357 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
358 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
359 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) + 1);
361 g_atomic_int_inc (&mini_object->refcount);
367 find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,
368 GstMiniObjectNotify notify, gpointer data)
372 for (i = 0; i < object->n_qdata; i++) {
373 if (QDATA_QUARK (object, i) == quark) {
374 /* check if we need to match the callback too */
375 if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&
376 QDATA_DATA (object, i) == data))
384 remove_notify (GstMiniObject * object, gint index)
387 if (--object->n_qdata == 0) {
388 /* we don't shrink but free when everything is gone */
389 g_free (object->qdata);
390 object->qdata = NULL;
391 } else if (index != object->n_qdata)
392 QDATA (object, index) = QDATA (object, object->n_qdata);
396 set_notify (GstMiniObject * object, gint index, GQuark quark,
397 GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)
401 index = object->n_qdata++;
403 g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);
405 QDATA_QUARK (object, index) = quark;
406 QDATA_NOTIFY (object, index) = notify;
407 QDATA_DATA (object, index) = data;
408 QDATA_DESTROY (object, index) = destroy;
412 call_finalize_notify (GstMiniObject * obj)
416 for (i = 0; i < obj->n_qdata; i++) {
417 if (QDATA_QUARK (obj, i) == weak_ref_quark)
418 QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);
419 if (QDATA_DESTROY (obj, i))
420 QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));
425 * gst_mini_object_unref:
426 * @mini_object: the mini-object
428 * Decreases the reference count of the mini-object, possibly freeing
432 gst_mini_object_unref (GstMiniObject * mini_object)
434 g_return_if_fail (mini_object != NULL);
436 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
438 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object),
439 GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) - 1);
441 g_return_if_fail (mini_object->refcount > 0);
443 if (G_UNLIKELY (g_atomic_int_dec_and_test (&mini_object->refcount))) {
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 #ifndef GST_DISABLE_TRACE
463 _gst_alloc_trace_free (_gst_mini_object_trace, mini_object);
465 if (mini_object->free)
466 mini_object->free (mini_object);
472 * gst_mini_object_replace:
473 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
475 * @newdata: pointer to new mini-object
477 * Atomically modifies a pointer to point to a new mini-object.
478 * The reference count of @olddata is decreased and the reference count of
479 * @newdata is increased.
481 * Either @newdata and the value pointed to by @olddata may be NULL.
483 * Returns: TRUE if @newdata was different from @olddata
486 gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
488 GstMiniObject *olddata_val;
490 g_return_val_if_fail (olddata != NULL, FALSE);
492 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
493 *olddata, *olddata ? (*olddata)->refcount : 0,
494 newdata, newdata ? newdata->refcount : 0);
496 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
498 if (G_UNLIKELY (olddata_val == newdata))
502 gst_mini_object_ref (newdata);
504 while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
505 olddata, olddata_val, newdata))) {
506 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
507 if (G_UNLIKELY (olddata_val == newdata))
512 gst_mini_object_unref (olddata_val);
514 return olddata_val != newdata;
518 * gst_mini_object_steal:
519 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
522 * Replace the current #GstMiniObject pointer to by @olddata with NULL and
523 * return the old value.
525 * Returns: the #GstMiniObject at @oldata
528 gst_mini_object_steal (GstMiniObject ** olddata)
530 GstMiniObject *olddata_val;
532 g_return_val_if_fail (olddata != NULL, NULL);
534 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",
535 *olddata, *olddata ? (*olddata)->refcount : 0);
538 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
539 if (olddata_val == NULL)
541 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
542 olddata, olddata_val, NULL)));
548 * gst_mini_object_take:
549 * @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
551 * @newdata: pointer to new mini-object
553 * Modifies a pointer to point to a new mini-object. The modification
554 * is done atomically. This version is similar to gst_mini_object_replace()
555 * except that it does not increase the refcount of @newdata and thus
556 * takes ownership of @newdata.
558 * Either @newdata and the value pointed to by @olddata may be NULL.
560 * Returns: TRUE if @newdata was different from @olddata
563 gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)
565 GstMiniObject *olddata_val;
567 g_return_val_if_fail (olddata != NULL, FALSE);
569 GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",
570 *olddata, *olddata ? (*olddata)->refcount : 0,
571 newdata, newdata ? newdata->refcount : 0);
574 olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
575 if (G_UNLIKELY (olddata_val == newdata))
577 } while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
578 olddata, olddata_val, newdata)));
581 gst_mini_object_unref (olddata_val);
583 return olddata_val != newdata;
587 * gst_mini_object_weak_ref: (skip)
588 * @object: #GstMiniObject to reference weakly
589 * @notify: callback to invoke before the mini object is freed
590 * @data: extra data to pass to notify
592 * Adds a weak reference callback to a mini object. Weak references are
593 * used for notification when a mini object is finalized. They are called
594 * "weak references" because they allow you to safely hold a pointer
595 * to the mini object without calling gst_mini_object_ref()
596 * (gst_mini_object_ref() adds a strong reference, that is, forces the object
602 gst_mini_object_weak_ref (GstMiniObject * object,
603 GstMiniObjectNotify notify, gpointer data)
605 g_return_if_fail (object != NULL);
606 g_return_if_fail (notify != NULL);
607 g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);
609 G_LOCK (qdata_mutex);
610 set_notify (object, -1, weak_ref_quark, notify, data, NULL);
611 G_UNLOCK (qdata_mutex);
615 * gst_mini_object_weak_unref: (skip)
616 * @object: #GstMiniObject to remove a weak reference from
617 * @notify: callback to search for
618 * @data: data to search for
620 * Removes a weak reference callback from a mini object.
625 gst_mini_object_weak_unref (GstMiniObject * object,
626 GstMiniObjectNotify notify, gpointer data)
630 g_return_if_fail (object != NULL);
631 g_return_if_fail (notify != NULL);
633 G_LOCK (qdata_mutex);
634 if ((i = find_notify (object, weak_ref_quark, TRUE, notify, data)) != -1) {
635 remove_notify (object, i);
637 g_warning ("%s: couldn't find weak ref %p(%p)", G_STRFUNC, notify, data);
639 G_UNLOCK (qdata_mutex);
643 * gst_mini_object_set_qdata:
644 * @object: a #GstMiniObject
645 * @quark: A #GQuark, naming the user data pointer
646 * @data: An opaque user data pointer
647 * @destroy: Function to invoke with @data as argument, when @data
650 * This sets an opaque, named pointer on a miniobject.
651 * The name is specified through a #GQuark (retrived e.g. via
652 * g_quark_from_static_string()), and the pointer
653 * can be gotten back from the @object with gst_mini_object_get_qdata()
654 * until the @object is disposed.
655 * Setting a previously set user data pointer, overrides (frees)
656 * the old pointer set, using #NULL as pointer essentially
657 * removes the data stored.
659 * @destroy may be specified which is called with @data as argument
660 * when the @object is disposed, or the data is being overwritten by
661 * a call to gst_mini_object_set_qdata() with the same @quark.
664 gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,
665 gpointer data, GDestroyNotify destroy)
668 gpointer old_data = NULL;
669 GDestroyNotify old_notify = NULL;
671 g_return_if_fail (object != NULL);
672 g_return_if_fail (quark > 0);
674 G_LOCK (qdata_mutex);
675 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
677 old_data = QDATA_DATA (object, i);
678 old_notify = QDATA_DESTROY (object, i);
681 remove_notify (object, i);
684 set_notify (object, i, quark, NULL, data, destroy);
685 G_UNLOCK (qdata_mutex);
688 old_notify (old_data);
692 * gst_mini_object_get_qdata:
693 * @object: The GstMiniObject to get a stored user data pointer from
694 * @quark: A #GQuark, naming the user data pointer
696 * This function gets back user data pointers stored via
697 * gst_mini_object_set_qdata().
699 * Returns: (transfer none): The user data pointer set, or %NULL
702 gst_mini_object_get_qdata (GstMiniObject * object, GQuark quark)
707 g_return_val_if_fail (object != NULL, NULL);
708 g_return_val_if_fail (quark > 0, NULL);
710 G_LOCK (qdata_mutex);
711 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1)
712 result = QDATA_DATA (object, i);
715 G_UNLOCK (qdata_mutex);
721 * gst_mini_object_steal_qdata:
722 * @object: The GstMiniObject to get a stored user data pointer from
723 * @quark: A #GQuark, naming the user data pointer
725 * This function gets back user data pointers stored via gst_mini_object_set_qdata()
726 * and removes the data from @object without invoking its destroy() function (if
729 * Returns: (transfer full): The user data pointer set, or %NULL
732 gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)
737 g_return_val_if_fail (object != NULL, NULL);
738 g_return_val_if_fail (quark > 0, NULL);
740 G_LOCK (qdata_mutex);
741 if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
742 result = QDATA_DATA (object, i);
743 remove_notify (object, i);
747 G_UNLOCK (qdata_mutex);