| /**************************************************************************** |
| ** |
| ** Copyright (C) 2016 The Qt Company Ltd. |
| ** Contact: https://www.qt.io/licensing/ |
| ** |
| ** This file is part of the test suite of the Qt Toolkit. |
| ** |
| ** $QT_BEGIN_LICENSE:GPL-EXCEPT$ |
| ** Commercial License Usage |
| ** Licensees holding valid commercial Qt licenses may use this file in |
| ** accordance with the commercial license agreement provided with the |
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| ** |
| ** GNU General Public License Usage |
| ** Alternatively, this file may be used under the terms of the GNU |
| ** General Public License version 3 as published by the Free Software |
| ** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT |
| ** included in the packaging of this file. Please review the following |
| ** information to ensure the GNU General Public License requirements will |
| ** be met: https://www.gnu.org/licenses/gpl-3.0.html. |
| ** |
| ** $QT_END_LICENSE$ |
| ** |
| ****************************************************************************/ |
| |
| |
| #ifndef QTHREADONCE_H |
| #define QTHREADONCE_H |
| |
| #include <QtCore/qglobal.h> |
| #include <QtCore/qatomic.h> |
| |
| |
| class QOnceControl |
| { |
| public: |
| QOnceControl(QBasicAtomicInt *); |
| ~QOnceControl(); |
| |
| bool mustRunCode(); |
| void done(); |
| |
| private: |
| QBasicAtomicInt *gv; |
| union { |
| qint32 extra; |
| void *d; |
| }; |
| }; |
| |
| #define Q_ONCE_GV_NAME2(prefix, line) prefix ## line |
| #define Q_ONCE_GV_NAME(prefix, line) Q_ONCE_GV_NAME2(prefix, line) |
| #define Q_ONCE_GV Q_ONCE_GV_NAME(_q_once_, __LINE__) |
| |
| #define Q_ONCE \ |
| static QBasicAtomicInt Q_ONCE_GV = Q_BASIC_ATOMIC_INITIALIZER(0); \ |
| if (0){} else \ |
| for (QOnceControl _control_(&Q_ONCE_GV); _control_.mustRunCode(); _control_.done()) |
| |
| template<typename T> |
| class QSingleton |
| { |
| // this is a POD-like class |
| struct Destructor |
| { |
| T *&pointer; |
| Destructor(T *&ptr) : pointer(ptr) {} |
| ~Destructor() { delete pointer; } |
| }; |
| |
| public: |
| T *_q_value; |
| QBasicAtomicInt _q_guard; |
| |
| inline T *value() |
| { |
| for (QOnceControl control(&_q_guard); control.mustRunCode(); control.done()) { |
| _q_value = new T(); |
| static Destructor cleanup(_q_value); |
| } |
| return _q_value; |
| } |
| |
| inline T& operator*() { return *value(); } |
| inline T* operator->() { return value(); } |
| inline operator T*() { return value(); } |
| }; |
| |
| #endif |