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Diffstat (limited to 'src/corelib/global/qglobalstatic.h')
| -rw-r--r-- | src/corelib/global/qglobalstatic.h | 157 |
1 files changed, 157 insertions, 0 deletions
diff --git a/src/corelib/global/qglobalstatic.h b/src/corelib/global/qglobalstatic.h new file mode 100644 index 0000000000..78a4acff12 --- /dev/null +++ b/src/corelib/global/qglobalstatic.h @@ -0,0 +1,157 @@ +/**************************************************************************** +** +** Copyright (C) 2012 Intel Corporation +** Contact: http://www.qt-project.org/legal +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and Digia. For licensing terms and +** conditions see http://qt.digia.com/licensing. For further information +** use the contact form at http://qt.digia.com/contact-us. +** +** 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, Digia gives you certain additional +** rights. These rights are described in the Digia Qt LGPL Exception +** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#include <QtCore/qglobal.h> + +#ifndef QGLOBALSTATIC_H +#define QGLOBALSTATIC_H + +#include <QtCore/qatomic.h> + +QT_BEGIN_HEADER +QT_BEGIN_NAMESPACE + +/* + * QGlobalStatic internals: + * + * The pointer is initialized to 0. + * The guard is initialized to 0. + * The guard can assume the following values: + * -2: object initialized and already destroyed + * -1: object initialized and is still valid + * 0: not initialized, the value of the pointer should be null + * +1: initializing, must wait until a state change happens + * (not used in the current implementation) + */ + +namespace QtGlobalStatic { +enum GuardValues { + Destroyed = -2, + Initialized = -1, + Uninitialized = 0, + Initializing = 1 +}; +} + +#if defined(QT_NO_THREAD) || defined(Q_CC_GNU) +// some compilers support thread-safe statics +// The IA-64 C++ ABI requires this, so we know that all GCC versions since 3.4 +// support it. C++11 also requires this behavior. +// Clang and Intel CC masquerade as GCC when compiling on Linux and Mac OS X. + +#define Q_GLOBAL_STATIC_INTERNAL(ARGS) \ + Q_DECL_HIDDEN inline Type *innerFunction() \ + { \ + struct HolderBase { \ + ~HolderBase() Q_DECL_NOTHROW \ + { guard.store(QtGlobalStatic::Destroyed); } \ + }; \ + static struct Holder : public HolderBase { \ + Type value; \ + Holder() \ + Q_DECL_NOEXCEPT_EXPR(noexcept(Type ARGS)) \ + : value ARGS \ + { guard.store(QtGlobalStatic::Initialized); } \ + } holder; \ + return &holder.value; \ + } +#else +// We don't know if this compiler supports thread-safe global statics +// so use our own locked implementation + +QT_END_NAMESPACE +#include <QtCore/qmutex.h> +QT_BEGIN_NAMESPACE + +#define Q_GLOBAL_STATIC_INTERNAL(ARGS) \ + Q_DECL_HIDDEN inline Type *innerFunction() \ + { \ + static Type *d; \ + static QBasicMutex mutex; \ + int x = guard.loadAcquire(); \ + if (Q_UNLIKELY(x >= QtGlobalStatic::Uninitialized)) { \ + QMutexLocker locker(&mutex); \ + if (guard.load() == QtGlobalStatic::Uninitialized) { \ + d = new Type ARGS; \ + static struct Cleanup { \ + ~Cleanup() { \ + delete d; \ + guard.store(QtGlobalStatic::Destroyed); \ + } \ + } cleanup; \ + guard.store(QtGlobalStatic::Initialized); \ + } \ + } \ + return d; \ + } +#endif + +// this class must be POD, unless the compiler supports thread-safe statics +template <typename T, T *(&innerFunction)(), QBasicAtomicInt &guard> +struct QGlobalStatic +{ + typedef T Type; + + bool isDestroyed() const { return guard.load() <= QtGlobalStatic::Destroyed; } + bool exists() const { return guard.load() == QtGlobalStatic::Initialized; } + operator Type *() { if (isDestroyed()) return 0; return innerFunction(); } + Type *operator()() { if (isDestroyed()) return 0; return innerFunction(); } + Type *operator->() { return innerFunction(); } + Type &operator*() { return *innerFunction(); } +}; + +#define Q_GLOBAL_STATIC_WITH_ARGS(TYPE, NAME, ARGS) \ + namespace { namespace Q_QGS_ ## NAME { \ + typedef TYPE Type; \ + QBasicAtomicInt guard = Q_BASIC_ATOMIC_INITIALIZER(QtGlobalStatic::Uninitialized); \ + Q_GLOBAL_STATIC_INTERNAL(ARGS) \ + } } \ + static QGlobalStatic<TYPE, \ + Q_QGS_ ## NAME::innerFunction, \ + Q_QGS_ ## NAME::guard> NAME; + +#define Q_GLOBAL_STATIC(TYPE, NAME) \ + Q_GLOBAL_STATIC_WITH_ARGS(TYPE, NAME, ()) + +QT_END_NAMESPACE +QT_END_HEADER + +#endif // QGLOBALSTATIC_H |