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This allows the caller to take the lock on the GData first, and perform some operations. This is useful under the assumption, that the caller can find cases where calling g_datalist_id_update_atomic() is unnecessary, but where they still need to hold the lock to atomically make that decision. That can avoid performance overhead, if we can avoid calling g_datalist_id_update_atomic(). That matters for checking the toggle-notify in g_object_ref()/g_object_unref(). Note that with "already_locked", g_datalist_id_update_atomic() will still unlock the GData at the end. That is because the API of g_datalist_id_update_atomic() requires that it might re-allocate the buffer, and it can do a more efficient unlock in that case, instead of leaving it to the caller. The usage and purpose of this parameter is anyway special, so the few callers will be fine with this asymmetry. It can safe an additional atomic operation to first set the buffer and then do a separate g_datalist_unlock().
88 lines
3.6 KiB
C
88 lines
3.6 KiB
C
/* GLIB - Library of useful routines for C programming
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* gdataset-private.h: Internal macros for accessing dataset values
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* Copyright (C) 2005 Red Hat
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*
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* SPDX-License-Identifier: LGPL-2.1-or-later
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* Modified by the GLib Team and others 1997-2000. See the AUTHORS
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* file for a list of people on the GLib Team. See the ChangeLog
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* files for a list of changes. These files are distributed with
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* GLib at ftp://ftp.gtk.org/pub/gtk/.
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*/
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#ifndef __G_DATASETPRIVATE_H__
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#define __G_DATASETPRIVATE_H__
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#include <gatomic.h>
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G_BEGIN_DECLS
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/* GET_FLAGS is implemented via atomic pointer access, to allow memory
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* barriers to take effect without acquiring the global dataset mutex.
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*/
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#define G_DATALIST_GET_FLAGS(datalist) \
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((gsize) g_atomic_pointer_get (datalist) & G_DATALIST_FLAGS_MASK)
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#define _G_DATALIST_LOCK_BIT 2
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#define g_datalist_lock(datalist) \
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G_STMT_START \
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{ \
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GData **const _datalist = (datalist); \
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\
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g_pointer_bit_lock ((void **) _datalist, _G_DATALIST_LOCK_BIT); \
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} \
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G_STMT_END
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#define g_datalist_unlock(datalist) \
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G_STMT_START \
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{ \
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GData **const _datalist = (datalist); \
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\
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g_pointer_bit_unlock ((void **) _datalist, _G_DATALIST_LOCK_BIT); \
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} \
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G_STMT_END
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/*< private >
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* GDataListUpdateAtomicFunc:
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* @data: (inout) (nullable) (not optional): the existing data corresponding to
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* the "key_id" parameter of g_datalist_id_update_atomic(), and return location
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* for the new value for it
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* @destroy_notify: (inout) (nullable) (not optional): the existing destroy
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* notify function for @data, and return location for the destroy notify
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* function for the new value for it
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* @user_data: user data passed in to [func@GLib.datalist_id_update_atomic]
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*
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* Callback from [func@GLib.datalist_id_update_atomic].
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*
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* Since: 2.80
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*/
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typedef gpointer (*GDataListUpdateAtomicFunc) (gpointer *data,
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GDestroyNotify *destroy_notify,
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gpointer user_data);
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gpointer g_datalist_id_update_atomic (GData **datalist,
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GQuark key_id,
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gboolean already_locked,
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GDataListUpdateAtomicFunc callback,
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gpointer user_data);
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G_END_DECLS
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#endif /* __G_DATASETPRIVATE_H__ */
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