/* GStreamer
* Copyright (C) 2005 David Schleef <ds@schleef.org>
*
* gstminiobject.h: Header for GstMiniObject
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstminiobject
* @title: GstMiniObject
* @short_description: Lightweight base class for the GStreamer object hierarchy
*
* #GstMiniObject is a simple structure that can be used to implement refcounted
* types.
*
* Subclasses will include #GstMiniObject as the first member in their structure
* and then call gst_mini_object_init() to initialize the #GstMiniObject fields.
*
* gst_mini_object_ref() and gst_mini_object_unref() increment and decrement the
* refcount respectively. When the refcount of a mini-object reaches 0, the
* dispose function is called first and when this returns %TRUE, the free
* function of the miniobject is called.
*
* A copy can be made with gst_mini_object_copy().
*
* gst_mini_object_is_writable() will return %TRUE when the refcount of the
* object is exactly 1, meaning the current caller has the only reference to the
* object. gst_mini_object_make_writable() will return a writable version of the
* object, which might be a new copy when the refcount was not 1.
*
* Opaque data can be associated with a #GstMiniObject with
* gst_mini_object_set_qdata() and gst_mini_object_get_qdata(). The data is
* meant to be specific to the particular object and is not automatically copied
* with gst_mini_object_copy() or similar methods.
*
* A weak reference can be added and remove with gst_mini_object_weak_ref()
* and gst_mini_object_weak_unref() respectively.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gst/gst_private.h"
#include "gst/gstminiobject.h"
#include "gst/gstinfo.h"
#include <gobject/gvaluecollector.h>
/* Mutex used for weak referencing */
G_LOCK_DEFINE_STATIC (qdata_mutex);
static GQuark weak_ref_quark;
#define SHARE_ONE (1 << 16)
#define SHARE_TWO (2 << 16)
#define SHARE_MASK (~(SHARE_ONE - 1))
#define IS_SHARED(state) (state >= SHARE_TWO)
#define LOCK_ONE (GST_LOCK_FLAG_LAST)
#define FLAG_MASK (GST_LOCK_FLAG_LAST - 1)
#define LOCK_MASK ((SHARE_ONE - 1) - FLAG_MASK)
#define LOCK_FLAG_MASK (SHARE_ONE - 1)
typedef struct
{
GQuark quark;
GstMiniObjectNotify notify;
gpointer data;
GDestroyNotify destroy;
} GstQData;
#define QDATA(o,i) ((GstQData *)(o)->qdata)[(i)]
#define QDATA_QUARK(o,i) (QDATA(o,i).quark)
#define QDATA_NOTIFY(o,i) (QDATA(o,i).notify)
#define QDATA_DATA(o,i) (QDATA(o,i).data)
#define QDATA_DESTROY(o,i) (QDATA(o,i).destroy)
void
_priv_gst_mini_object_initialize (void)
{
weak_ref_quark = g_quark_from_static_string ("GstMiniObjectWeakRefQuark");
}
/**
* gst_mini_object_init: (skip)
* @mini_object: a #GstMiniObject
* @flags: initial #GstMiniObjectFlags
* @type: the #GType of the mini-object to create
* @copy_func: (allow-none): the copy function, or %NULL
* @dispose_func: (allow-none): the dispose function, or %NULL
* @free_func: (allow-none): the free function or %NULL
*
* Initializes a mini-object with the desired type and copy/dispose/free
* functions.
*/
void
gst_mini_object_init (GstMiniObject * mini_object, guint flags, GType type,
GstMiniObjectCopyFunction copy_func,
GstMiniObjectDisposeFunction dispose_func,
GstMiniObjectFreeFunction free_func)
{
mini_object->type = type;
mini_object->refcount = 1;
mini_object->lockstate = 0;
mini_object->flags = flags;
mini_object->copy = copy_func;
mini_object->dispose = dispose_func;
mini_object->free = free_func;
mini_object->n_qdata = 0;
mini_object->qdata = NULL;
GST_TRACER_MINI_OBJECT_CREATED (mini_object);
}
/**
* gst_mini_object_copy: (skip)
* @mini_object: the mini-object to copy
*
* Creates a copy of the mini-object.
*
* MT safe
*
* Returns: (transfer full) (nullable): the new mini-object if copying is
* possible, %NULL otherwise.
*/
GstMiniObject *
gst_mini_object_copy (const GstMiniObject * mini_object)
{
GstMiniObject *copy;
g_return_val_if_fail (mini_object != NULL, NULL);
if (mini_object->copy)
copy = mini_object->copy (mini_object);
else
copy = NULL;
return copy;
}
/**
* gst_mini_object_lock:
* @object: the mini-object to lock
* @flags: #GstLockFlags
*
* Lock the mini-object with the specified access mode in @flags.
*
* Returns: %TRUE if @object could be locked.
*/
gboolean
gst_mini_object_lock (GstMiniObject * object, GstLockFlags flags)
{
gint access_mode, state, newstate;
g_return_val_if_fail (object != NULL, FALSE);
g_return_val_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object), FALSE);
if (G_UNLIKELY (object->flags & GST_MINI_OBJECT_FLAG_LOCK_READONLY &&
flags & GST_LOCK_FLAG_WRITE))
return FALSE;
do {
access_mode = flags & FLAG_MASK;
newstate = state = g_atomic_int_get (&object->lockstate);
GST_CAT_TRACE (GST_CAT_LOCKING, "lock %p: state %08x, access_mode %d",
object, state, access_mode);
if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
/* shared ref */
newstate += SHARE_ONE;
access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
}
/* shared counter > 1 and write access is not allowed */
if (((state & GST_LOCK_FLAG_WRITE) != 0
|| (access_mode & GST_LOCK_FLAG_WRITE) != 0)
&& IS_SHARED (newstate))
goto lock_failed;
if (access_mode) {
if ((state & LOCK_FLAG_MASK) == 0) {
/* nothing mapped, set access_mode */
newstate |= access_mode;
} else {
/* access_mode must match */
if ((state & access_mode) != access_mode)
goto lock_failed;
}
/* increase refcount */
newstate += LOCK_ONE;
}
} while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
newstate));
return TRUE;
lock_failed:
{
GST_CAT_DEBUG (GST_CAT_LOCKING,
"lock failed %p: state %08x, access_mode %d", object, state,
access_mode);
return FALSE;
}
}
/**
* gst_mini_object_unlock:
* @object: the mini-object to unlock
* @flags: #GstLockFlags
*
* Unlock the mini-object with the specified access mode in @flags.
*/
void
gst_mini_object_unlock (GstMiniObject * object, GstLockFlags flags)
{
gint access_mode, state, newstate;
g_return_if_fail (object != NULL);
g_return_if_fail (GST_MINI_OBJECT_IS_LOCKABLE (object));
do {
access_mode = flags & FLAG_MASK;
newstate = state = g_atomic_int_get (&object->lockstate);
GST_CAT_TRACE (GST_CAT_LOCKING, "unlock %p: state %08x, access_mode %d",
object, state, access_mode);
if (access_mode & GST_LOCK_FLAG_EXCLUSIVE) {
/* shared counter */
g_return_if_fail (state >= SHARE_ONE);
newstate -= SHARE_ONE;
access_mode &= ~GST_LOCK_FLAG_EXCLUSIVE;
}
if (access_mode) {
g_return_if_fail ((state & access_mode) == access_mode);
/* decrease the refcount */
newstate -= LOCK_ONE;
/* last refcount, unset access_mode */
if ((newstate & LOCK_FLAG_MASK) == access_mode)
newstate &= ~LOCK_FLAG_MASK;
}
} while (!g_atomic_int_compare_and_exchange (&object->lockstate, state,
newstate));
}
/**
* gst_mini_object_is_writable:
* @mini_object: the mini-object to check
*
* If @mini_object has the LOCKABLE flag set, check if the current EXCLUSIVE
* lock on @object is the only one, this means that changes to the object will
* not be visible to any other object.
*
* If the LOCKABLE flag is not set, check if the refcount of @mini_object is
* exactly 1, meaning that no other reference exists to the object and that the
* object is therefore writable.
*
* Modification of a mini-object should only be done after verifying that it
* is writable.
*
* Returns: %TRUE if the object is writable.
*/
gboolean
gst_mini_object_is_writable (const GstMiniObject * mini_object)
{
gboolean result;
g_return_val_if_fail (mini_object != NULL, FALSE);
if (GST_MINI_OBJECT_IS_LOCKABLE (mini_object)) {
result = !IS_SHARED (g_atomic_int_get (&mini_object->lockstate));
} else {
result = (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) == 1);
}
return result;
}
/**
* gst_mini_object_make_writable: (skip)
* @mini_object: (transfer full): the mini-object to make writable
*
* Checks if a mini-object is writable. If not, a writable copy is made and
* returned. This gives away the reference to the original mini object,
* and returns a reference to the new object.
*
* MT safe
*
* Returns: (transfer full): a mini-object (possibly the same pointer) that
* is writable.
*/
GstMiniObject *
gst_mini_object_make_writable (GstMiniObject * mini_object)
{
GstMiniObject *ret;
g_return_val_if_fail (mini_object != NULL, NULL);
if (gst_mini_object_is_writable (mini_object)) {
ret = mini_object;
} else {
ret = gst_mini_object_copy (mini_object);
GST_CAT_DEBUG (GST_CAT_PERFORMANCE, "copy %s miniobject %p -> %p",
g_type_name (GST_MINI_OBJECT_TYPE (mini_object)), mini_object, ret);
gst_mini_object_unref (mini_object);
}
return ret;
}
/**
* gst_mini_object_ref: (skip)
* @mini_object: the mini-object
*
* Increase the reference count of the mini-object.
*
* Note that the refcount affects the writability
* of @mini-object, see gst_mini_object_is_writable(). It is
* important to note that keeping additional references to
* GstMiniObject instances can potentially increase the number
* of memcpy operations in a pipeline, especially if the miniobject
* is a #GstBuffer.
*
* Returns: (transfer full): the mini-object.
*/
GstMiniObject *
gst_mini_object_ref (GstMiniObject * mini_object)
{
gint old_refcount, new_refcount;
g_return_val_if_fail (mini_object != NULL, NULL);
/* we can't assert that the refcount > 0 since the _free functions
* increments the refcount from 0 to 1 again to allow resurecting
* the object
g_return_val_if_fail (mini_object->refcount > 0, NULL);
*/
old_refcount = g_atomic_int_add (&mini_object->refcount, 1);
new_refcount = old_refcount + 1;
GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p ref %d->%d", mini_object,
old_refcount, new_refcount);
GST_TRACER_MINI_OBJECT_REFFED (mini_object, new_refcount);
return mini_object;
}
static gint
find_notify (GstMiniObject * object, GQuark quark, gboolean match_notify,
GstMiniObjectNotify notify, gpointer data)
{
guint i;
for (i = 0; i < object->n_qdata; i++) {
if (QDATA_QUARK (object, i) == quark) {
/* check if we need to match the callback too */
if (!match_notify || (QDATA_NOTIFY (object, i) == notify &&
QDATA_DATA (object, i) == data))
return i;
}
}
return -1;
}
static void
remove_notify (GstMiniObject * object, gint index)
{
/* remove item */
if (--object->n_qdata == 0) {
/* we don't shrink but free when everything is gone */
g_free (object->qdata);
object->qdata = NULL;
} else if (index != object->n_qdata)
QDATA (object, index) = QDATA (object, object->n_qdata);
}
static void
set_notify (GstMiniObject * object, gint index, GQuark quark,
GstMiniObjectNotify notify, gpointer data, GDestroyNotify destroy)
{
if (index == -1) {
/* add item */
index = object->n_qdata++;
object->qdata =
g_realloc (object->qdata, sizeof (GstQData) * object->n_qdata);
}
QDATA_QUARK (object, index) = quark;
QDATA_NOTIFY (object, index) = notify;
QDATA_DATA (object, index) = data;
QDATA_DESTROY (object, index) = destroy;
}
static void
call_finalize_notify (GstMiniObject * obj)
{
guint i;
for (i = 0; i < obj->n_qdata; i++) {
if (QDATA_QUARK (obj, i) == weak_ref_quark)
QDATA_NOTIFY (obj, i) (QDATA_DATA (obj, i), obj);
if (QDATA_DESTROY (obj, i))
QDATA_DESTROY (obj, i) (QDATA_DATA (obj, i));
}
}
/**
* gst_mini_object_unref: (skip)
* @mini_object: the mini-object
*
* Decreases the reference count of the mini-object, possibly freeing
* the mini-object.
*/
void
gst_mini_object_unref (GstMiniObject * mini_object)
{
gint old_refcount, new_refcount;
g_return_if_fail (mini_object != NULL);
g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (mini_object) > 0);
old_refcount = g_atomic_int_add (&mini_object->refcount, -1);
new_refcount = old_refcount - 1;
g_return_if_fail (old_refcount > 0);
GST_CAT_TRACE (GST_CAT_REFCOUNTING, "%p unref %d->%d",
mini_object, old_refcount, new_refcount);
GST_TRACER_MINI_OBJECT_UNREFFED (mini_object, new_refcount);
if (new_refcount == 0) {
gboolean do_free;
if (mini_object->dispose)
do_free = mini_object->dispose (mini_object);
else
do_free = TRUE;
/* if the subclass recycled the object (and returned FALSE) we don't
* want to free the instance anymore */
if (G_LIKELY (do_free)) {
/* there should be no outstanding locks */
g_return_if_fail ((g_atomic_int_get (&mini_object->lockstate) & LOCK_MASK)
< 4);
if (mini_object->n_qdata) {
call_finalize_notify (mini_object);
g_free (mini_object->qdata);
}
GST_TRACER_MINI_OBJECT_DESTROYED (mini_object);
if (mini_object->free)
mini_object->free (mini_object);
}
}
}
/**
* gst_mini_object_replace:
* @olddata: (inout) (transfer full) (nullable): pointer to a pointer to a
* mini-object to be replaced
* @newdata: (allow-none): pointer to new mini-object
*
* Atomically modifies a pointer to point to a new mini-object.
* The reference count of @olddata is decreased and the reference count of
* @newdata is increased.
*
* Either @newdata and the value pointed to by @olddata may be %NULL.
*
* Returns: %TRUE if @newdata was different from @olddata
*/
gboolean
gst_mini_object_replace (GstMiniObject ** olddata, GstMiniObject * newdata)
{
GstMiniObject *olddata_val;
g_return_val_if_fail (olddata != NULL, FALSE);
GST_CAT_TRACE (GST_CAT_REFCOUNTING, "replace %p (%d) with %p (%d)",
*olddata, *olddata ? (*olddata)->refcount : 0,
newdata, newdata ? newdata->refcount : 0);
olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
if (G_UNLIKELY (olddata_val == newdata))
return FALSE;
if (newdata)
gst_mini_object_ref (newdata);
while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
olddata, olddata_val, newdata))) {
olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
if (G_UNLIKELY (olddata_val == newdata))
break;
}
if (olddata_val)
gst_mini_object_unref (olddata_val);
return olddata_val != newdata;
}
/**
* gst_mini_object_steal: (skip)
* @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
* be stolen
*
* Replace the current #GstMiniObject pointer to by @olddata with %NULL and
* return the old value.
*
* Returns: (nullable): the #GstMiniObject at @oldata
*/
GstMiniObject *
gst_mini_object_steal (GstMiniObject ** olddata)
{
GstMiniObject *olddata_val;
g_return_val_if_fail (olddata != NULL, NULL);
GST_CAT_TRACE (GST_CAT_REFCOUNTING, "steal %p (%d)",
*olddata, *olddata ? (*olddata)->refcount : 0);
do {
olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
if (olddata_val == NULL)
break;
} while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
olddata, olddata_val, NULL)));
return olddata_val;
}
/**
* gst_mini_object_take:
* @olddata: (inout) (transfer full): pointer to a pointer to a mini-object to
* be replaced
* @newdata: pointer to new mini-object
*
* Modifies a pointer to point to a new mini-object. The modification
* is done atomically. This version is similar to gst_mini_object_replace()
* except that it does not increase the refcount of @newdata and thus
* takes ownership of @newdata.
*
* Either @newdata and the value pointed to by @olddata may be %NULL.
*
* Returns: %TRUE if @newdata was different from @olddata
*/
gboolean
gst_mini_object_take (GstMiniObject ** olddata, GstMiniObject * newdata)
{
GstMiniObject *olddata_val;
g_return_val_if_fail (olddata != NULL, FALSE);
GST_CAT_TRACE (GST_CAT_REFCOUNTING, "take %p (%d) with %p (%d)",
*olddata, *olddata ? (*olddata)->refcount : 0,
newdata, newdata ? newdata->refcount : 0);
do {
olddata_val = g_atomic_pointer_get ((gpointer *) olddata);
if (G_UNLIKELY (olddata_val == newdata))
break;
} while (G_UNLIKELY (!g_atomic_pointer_compare_and_exchange ((gpointer *)
olddata, olddata_val, newdata)));
if (olddata_val)
gst_mini_object_unref (olddata_val);
return olddata_val != newdata;
}
/**
* gst_mini_object_weak_ref: (skip)
* @object: #GstMiniObject to reference weakly
* @notify: callback to invoke before the mini object is freed
* @data: extra data to pass to notify
*
* Adds a weak reference callback to a mini object. Weak references are
* used for notification when a mini object is finalized. They are called
* "weak references" because they allow you to safely hold a pointer
* to the mini object without calling gst_mini_object_ref()
* (gst_mini_object_ref() adds a strong reference, that is, forces the object
* to stay alive).
*/
void
gst_mini_object_weak_ref (GstMiniObject * object,
GstMiniObjectNotify notify, gpointer data)
{
g_return_if_fail (object != NULL);
g_return_if_fail (notify != NULL);
g_return_if_fail (GST_MINI_OBJECT_REFCOUNT_VALUE (object) >= 1);
G_LOCK (qdata_mutex);
set_notify (object, -1, weak_ref_quark, notify, data, NULL);
G_UNLOCK (qdata_mutex);
}
/**
* gst_mini_object_weak_unref: (skip)
* @object: #GstMiniObject to remove a weak reference from
* @notify: callback to search for
* @data: data to search for
*
* Removes a weak reference callback from a mini object.
*/
void
gst_mini_object_weak_unref (GstMiniObject * object,
GstMiniObjectNotify notify, gpointer data)
{
gint i;
g_return_if_fail (object != NULL);
g_return_if_fail (notify != NULL);
G_LOCK (qdata_mutex);
if ((i = find_notify (object, weak_ref_quark, TRUE, notify, data)) != -1) {
remove_notify (object, i);
} else {
g_warning ("%s: couldn't find weak ref %p (object:%p data:%p)", G_STRFUNC,
notify, object, data);
}
G_UNLOCK (qdata_mutex);
}
/**
* gst_mini_object_set_qdata:
* @object: a #GstMiniObject
* @quark: A #GQuark, naming the user data pointer
* @data: An opaque user data pointer
* @destroy: Function to invoke with @data as argument, when @data
* needs to be freed
*
* This sets an opaque, named pointer on a miniobject.
* The name is specified through a #GQuark (retrieved e.g. via
* g_quark_from_static_string()), and the pointer
* can be gotten back from the @object with gst_mini_object_get_qdata()
* until the @object is disposed.
* Setting a previously set user data pointer, overrides (frees)
* the old pointer set, using %NULL as pointer essentially
* removes the data stored.
*
* @destroy may be specified which is called with @data as argument
* when the @object is disposed, or the data is being overwritten by
* a call to gst_mini_object_set_qdata() with the same @quark.
*/
void
gst_mini_object_set_qdata (GstMiniObject * object, GQuark quark,
gpointer data, GDestroyNotify destroy)
{
gint i;
gpointer old_data = NULL;
GDestroyNotify old_notify = NULL;
g_return_if_fail (object != NULL);
g_return_if_fail (quark > 0);
G_LOCK (qdata_mutex);
if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
old_data = QDATA_DATA (object, i);
old_notify = QDATA_DESTROY (object, i);
if (data == NULL)
remove_notify (object, i);
}
if (data != NULL)
set_notify (object, i, quark, NULL, data, destroy);
G_UNLOCK (qdata_mutex);
if (old_notify)
old_notify (old_data);
}
/**
* gst_mini_object_get_qdata:
* @object: The GstMiniObject to get a stored user data pointer from
* @quark: A #GQuark, naming the user data pointer
*
* This function gets back user data pointers stored via
* gst_mini_object_set_qdata().
*
* Returns: (transfer none) (nullable): The user data pointer set, or
* %NULL
*/
gpointer
gst_mini_object_get_qdata (GstMiniObject * object, GQuark quark)
{
guint i;
gpointer result;
g_return_val_if_fail (object != NULL, NULL);
g_return_val_if_fail (quark > 0, NULL);
G_LOCK (qdata_mutex);
if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1)
result = QDATA_DATA (object, i);
else
result = NULL;
G_UNLOCK (qdata_mutex);
return result;
}
/**
* gst_mini_object_steal_qdata:
* @object: The GstMiniObject to get a stored user data pointer from
* @quark: A #GQuark, naming the user data pointer
*
* This function gets back user data pointers stored via gst_mini_object_set_qdata()
* and removes the data from @object without invoking its destroy() function (if
* any was set).
*
* Returns: (transfer full) (nullable): The user data pointer set, or
* %NULL
*/
gpointer
gst_mini_object_steal_qdata (GstMiniObject * object, GQuark quark)
{
guint i;
gpointer result;
g_return_val_if_fail (object != NULL, NULL);
g_return_val_if_fail (quark > 0, NULL);
G_LOCK (qdata_mutex);
if ((i = find_notify (object, quark, FALSE, NULL, NULL)) != -1) {
result = QDATA_DATA (object, i);
remove_notify (object, i);
} else {
result = NULL;
}
G_UNLOCK (qdata_mutex);
return result;
}