/****************************************************************************+
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**+
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** Copyright (C) 2010 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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+
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+
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#ifndef QTHREADONCE_H+
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#define QTHREADONCE_H+
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+
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#include <QtCore/qglobal.h>+
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#include <QtCore/qatomic.h>+
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+
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QT_BEGIN_HEADER+
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+
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QT_MODULE(Core)+
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+
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#ifndef QT_NO_THREAD+
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+
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class QOnceControl+
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{+
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public:+
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    QOnceControl(QBasicAtomicInt *);+
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    ~QOnceControl();+
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+
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    bool mustRunCode();+
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    void done();+
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+
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private:+
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    QBasicAtomicInt *gv;+
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    union {+
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        qint32 extra;+
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        void *d;+
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    };+
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};+
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+
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#define Q_ONCE_GV_NAME2(prefix, line)   prefix ## line+
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#define Q_ONCE_GV_NAME(prefix, line)    Q_ONCE_GV_NAME2(prefix, line)+
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#define Q_ONCE_GV                       Q_ONCE_GV_NAME(_q_once_, __LINE__)+
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+
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#define Q_ONCE \+
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    static QBasicAtomicInt Q_ONCE_GV = Q_BASIC_ATOMIC_INITIALIZER(0);   \+
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    if (0){} else                                                       \+
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        for (QOnceControl _control_(&Q_ONCE_GV); _control_.mustRunCode(); _control_.done())+
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+
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template<typename T>+
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class QSingleton+
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{+
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    // this is a POD-like class+
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    struct Destructor+
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    {+
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        T *&pointer;+
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        Destructor(T *&ptr) : pointer(ptr) {}+
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        ~Destructor() { delete pointer; }+
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    };+
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+
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public:+
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    T *_q_value;+
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    QBasicAtomicInt _q_guard;+
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+
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    inline T *value()+
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    {+
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        for (QOnceControl control(&_q_guard); control.mustRunCode(); control.done()) {+
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            _q_value = new T();+
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            static Destructor cleanup(_q_value);+
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        }+
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        return _q_value;+
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    }+
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+
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    inline T& operator*() { return *value(); }+
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    inline T* operator->() { return value(); }+
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    inline operator T*() { return value(); }+
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};+
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+
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#endif // QT_NO_THREAD+
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+
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QT_END_HEADER+
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+
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#endif+
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