93 lines
2.7 KiB
C++
93 lines
2.7 KiB
C++
/****************************************************************************
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**
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** Copyright (C) 2016 The Qt Company Ltd.
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** Contact: https://www.qt.io/licensing/
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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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** $QT_BEGIN_LICENSE:GPL-EXCEPT$
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** Commercial License Usage
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** Licensees holding valid commercial Qt licenses may use this file in
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** accordance with the commercial license agreement provided with the
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** Software or, alternatively, in accordance with the terms contained in
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** a written agreement between you and The Qt Company. For licensing terms
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** and conditions see https://www.qt.io/terms-conditions. For further
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** information use the contact form at https://www.qt.io/contact-us.
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**
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** GNU General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU
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** General Public License version 3 as published by the Free Software
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** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
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** included in the packaging of this file. Please review the following
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** information to ensure the GNU General Public License requirements will
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** be met: https://www.gnu.org/licenses/gpl-3.0.html.
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**
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** $QT_END_LICENSE$
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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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#include <QtCore/qglobal.h>
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#include <QtCore/qatomic.h>
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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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bool mustRunCode();
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void done();
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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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#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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#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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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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public:
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T *_q_value;
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QBasicAtomicInt _q_guard;
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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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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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#endif
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