/****************************************************************************+
−
**+
−
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).+
−
** All rights reserved.+
−
** Contact: Nokia Corporation (qt-info@nokia.com)+
−
**+
−
** This file is part of the test suite of the Qt Toolkit.+
−
**+
−
** $QT_BEGIN_LICENSE:LGPL$+
−
** No Commercial Usage+
−
** This file contains pre-release code and may not be distributed.+
−
** You may use this file in accordance with the terms and conditions+
−
** contained in the Technology Preview License Agreement accompanying+
−
** this package.+
−
**+
−
** GNU Lesser General Public License Usage+
−
** Alternatively, this file may be used under the terms of the GNU Lesser+
−
** General Public License version 2.1 as published by the Free Software+
−
** Foundation and appearing in the file LICENSE.LGPL included in the+
−
** packaging of this file.  Please review the following information to+
−
** ensure the GNU Lesser General Public License version 2.1 requirements+
−
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.+
−
**+
−
** In addition, as a special exception, Nokia gives you certain additional+
−
** rights.  These rights are described in the Nokia Qt LGPL Exception+
−
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.+
−
**+
−
** If you have questions regarding the use of this file, please contact+
−
** Nokia at qt-info@nokia.com.+
−
**+
−
**+
−
**+
−
**+
−
**+
−
**+
−
**+
−
**+
−
** $QT_END_LICENSE$+
−
**+
−
****************************************************************************/+
−
+
−
+
−
#include "qplatformdefs.h"+
−
#include "qthreadonce.h"+
−
+
−
#ifndef QT_NO_THREAD+
−
#include "qmutex.h"+
−
+
−
Q_GLOBAL_STATIC_WITH_ARGS(QMutex, onceInitializationMutex, (QMutex::Recursive))+
−
+
−
enum QOnceExtra {+
−
    MustRunCode = 0x01,+
−
    MustUnlockMutex = 0x02+
−
};+
−
+
−
/*!+
−
    \internal+
−
    Initialize the Q_ONCE structure.+
−
+
−
    Q_ONCE consists of two variables:+
−
     - a static POD QOnceControl::ControlVariable (it's a QBasicAtomicInt)+
−
     - an automatic QOnceControl that controls the former+
−
+
−
    The POD is initialized to 0.+
−
+
−
    When QOnceControl's constructor starts, it'll lock the global+
−
    initialization mutex. It'll then check if it's the first to up+
−
    the control variable and will take note.+
−
+
−
    The QOnceControl's destructor will unlock the global+
−
    initialization mutex.+
−
*/+
−
QOnceControl::QOnceControl(QBasicAtomicInt *control)+
−
{+
−
    d = 0;+
−
    gv = control;+
−
    // check if code has already run once+
−
    if (*gv == 2) {+
−
        // uncontended case: it has already initialized+
−
        // no waiting+
−
        return;+
−
    }+
−
+
−
    // acquire the path+
−
    onceInitializationMutex()->lock();+
−
    extra = MustUnlockMutex;+
−
+
−
    if (gv->testAndSetAcquire(0, 1)) {+
−
        // path acquired, we're the first+
−
        extra |= MustRunCode;+
−
    }+
−
}+
−
+
−
QOnceControl::~QOnceControl()+
−
{+
−
    if (mustRunCode())+
−
        // code wasn't run!+
−
        gv->testAndSetRelease(1, 0);+
−
    else+
−
        gv->testAndSetRelease(1, 2);+
−
    if (extra & MustUnlockMutex)+
−
        onceInitializationMutex()->unlock();+
−
}+
−
+
−
/*!+
−
    \internal+
−
    Returns true if the initialization code must be run.+
−
+
−
    Obviously, the initialization code must be run only once...+
−
*/+
−
bool QOnceControl::mustRunCode()+
−
{+
−
    return extra & MustRunCode;+
−
}+
−
+
−
void QOnceControl::done()+
−
{+
−
    extra &= ~MustRunCode;+
−
}+
−
+
−
#endif // QT_NO_THREAD+
−