38be0d1383
This is the beginning of revision history for this module. If you want to look at revision history older than this, please refer to the Qt Git wiki for how to use Git history grafting. At the time of writing, this wiki is located here: http://qt.gitorious.org/qt/pages/GitIntroductionWithQt If you have already performed the grafting and you don't see any history beyond this commit, try running "git log" with the "--follow" argument. Branched from the monolithic repo, Qt master branch, at commit 896db169ea224deb96c59ce8af800d019de63f12
122 lines
3.2 KiB
C++
122 lines
3.2 KiB
C++
/****************************************************************************
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**
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** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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** All rights reserved.
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** Contact: Nokia Corporation (qt-info@nokia.com)
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**
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** This file is part of the test suite of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** No Commercial Usage
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** This file contains pre-release code and may not be distributed.
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** You may use this file in accordance with the terms and conditions
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** contained in the Technology Preview License Agreement accompanying
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** this package.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 2.1 as published by the Free Software
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** Foundation and appearing in the file LICENSE.LGPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU Lesser General Public License version 2.1 requirements
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
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**
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** In addition, as a special exception, Nokia gives you certain additional
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** rights. These rights are described in the Nokia Qt LGPL Exception
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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**
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** If you have questions regarding the use of this file, please contact
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** Nokia at qt-info@nokia.com.
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**
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**
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**
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**
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**
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**
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**
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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#include "qplatformdefs.h"
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#include "qthreadonce.h"
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#ifndef QT_NO_THREAD
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#include "qmutex.h"
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Q_GLOBAL_STATIC_WITH_ARGS(QMutex, onceInitializationMutex, (QMutex::Recursive))
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enum QOnceExtra {
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MustRunCode = 0x01,
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MustUnlockMutex = 0x02
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};
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/*!
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\internal
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Initialize the Q_ONCE structure.
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Q_ONCE consists of two variables:
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- a static POD QOnceControl::ControlVariable (it's a QBasicAtomicInt)
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- an automatic QOnceControl that controls the former
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The POD is initialized to 0.
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When QOnceControl's constructor starts, it'll lock the global
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initialization mutex. It'll then check if it's the first to up
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the control variable and will take note.
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The QOnceControl's destructor will unlock the global
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initialization mutex.
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*/
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QOnceControl::QOnceControl(QBasicAtomicInt *control)
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{
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d = 0;
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gv = control;
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// check if code has already run once
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if (*gv == 2) {
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// uncontended case: it has already initialized
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// no waiting
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return;
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}
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// acquire the path
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onceInitializationMutex()->lock();
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extra = MustUnlockMutex;
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if (gv->testAndSetAcquire(0, 1)) {
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// path acquired, we're the first
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extra |= MustRunCode;
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}
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}
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QOnceControl::~QOnceControl()
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{
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if (mustRunCode())
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// code wasn't run!
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gv->testAndSetRelease(1, 0);
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else
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gv->testAndSetRelease(1, 2);
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if (extra & MustUnlockMutex)
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onceInitializationMutex()->unlock();
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}
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/*!
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\internal
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Returns true if the initialization code must be run.
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Obviously, the initialization code must be run only once...
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*/
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bool QOnceControl::mustRunCode()
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{
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return extra & MustRunCode;
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}
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void QOnceControl::done()
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{
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extra &= ~MustRunCode;
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}
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#endif // QT_NO_THREAD
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