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     2 **

     3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).

     4 ** All rights reserved.

     5 ** Contact: Nokia Corporation (qt-info@nokia.com)

     6 **

     7 ** This file is part of the test suite of the Qt Toolkit.

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    13 ** contained in the Technology Preview License Agreement accompanying

    14 ** this package.

    15 **

    16 ** GNU Lesser General Public License Usage

    17 ** Alternatively, this file may be used under the terms of the GNU Lesser

    18 ** General Public License version 2.1 as published by the Free Software

    19 ** Foundation and appearing in the file LICENSE.LGPL included in the

    20 ** packaging of this file.  Please review the following information to

    21 ** ensure the GNU Lesser General Public License version 2.1 requirements

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    38 ** $QT_END_LICENSE$

    39 **

    40 ****************************************************************************/

    41 

    42 

    43 #ifndef QTHREADONCE_H

    44 #define QTHREADONCE_H

    45 

    46 #include <QtCore/qglobal.h>

    47 #include <QtCore/qatomic.h>

    48 

    49 QT_BEGIN_HEADER

    50 

    51 QT_MODULE(Core)

    52 

    53 #ifndef QT_NO_THREAD

    54 

    55 class QOnceControl

    56 {

    57 public:

    58     QOnceControl(QBasicAtomicInt *);

    59     ~QOnceControl();

    60 

    61     bool mustRunCode();

    62     void done();

    63 

    64 private:

    65     QBasicAtomicInt *gv;

    66     union {

    67         qint32 extra;

    68         void *d;

    69     };

    70 };

    71 

    72 #define Q_ONCE_GV_NAME2(prefix, line)   prefix ## line

    73 #define Q_ONCE_GV_NAME(prefix, line)    Q_ONCE_GV_NAME2(prefix, line)

    74 #define Q_ONCE_GV                       Q_ONCE_GV_NAME(_q_once_, __LINE__)

    75 

    76 #define Q_ONCE \

    77     static QBasicAtomicInt Q_ONCE_GV = Q_BASIC_ATOMIC_INITIALIZER(0);   \

    78     if (0){} else                                                       \

    79         for (QOnceControl _control_(&Q_ONCE_GV); _control_.mustRunCode(); _control_.done())

    80 

    81 template<typename T>

    82 class QSingleton

    83 {

    84     // this is a POD-like class

    85     struct Destructor

    86     {

    87         T *&pointer;

    88         Destructor(T *&ptr) : pointer(ptr) {}

    89         ~Destructor() { delete pointer; }

    90     };

    91 

    92 public:

    93     T *_q_value;

    94     QBasicAtomicInt _q_guard;

    95 

    96     inline T *value()

    97     {

    98         for (QOnceControl control(&_q_guard); control.mustRunCode(); control.done()) {

    99             _q_value = new T();

   100             static Destructor cleanup(_q_value);

   101         }

   102         return _q_value;

   103     }

   104 

   105     inline T& operator*() { return *value(); }

   106     inline T* operator->() { return value(); }

   107     inline operator T*() { return value(); }

   108 };

   109 

   110 #endif // QT_NO_THREAD

   111 

   112 QT_END_HEADER

   113 

   114 #endif