path: root/src/corelib/thread/qreadwritelock.h

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** 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, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, 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.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

#ifndef QREADWRITELOCK_H
#define QREADWRITELOCK_H

#include <QtCore/qglobal.h>
#include <limits.h> // ### Qt 5: remove

QT_BEGIN_HEADER

QT_BEGIN_NAMESPACE

QT_MODULE(Core)

#ifndef QT_NO_THREAD

struct QReadWriteLockPrivate;

class Q_CORE_EXPORT QReadWriteLock
{
public:
    enum RecursionMode { NonRecursive, Recursive };

    QReadWriteLock(); // ### Qt 5: merge with below
    QReadWriteLock(RecursionMode recursionMode);
    ~QReadWriteLock();

    void lockForRead();
    bool tryLockForRead();
    bool tryLockForRead(int timeout);

    void lockForWrite();
    bool tryLockForWrite();
    bool tryLockForWrite(int timeout);

    void unlock();

private:
    Q_DISABLE_COPY(QReadWriteLock)
    QReadWriteLockPrivate *d;

    friend class QWaitCondition;
};

#if defined(Q_CC_MSVC)
#pragma warning( push )
#pragma warning( disable : 4312 ) // ignoring the warning from /Wp64
#endif

class Q_CORE_EXPORT QReadLocker
{
public:
    inline QReadLocker(QReadWriteLock *readWriteLock);

    inline ~QReadLocker()
    { unlock(); }

    inline void unlock()
    {
        if (q_lock) {
            if ((q_val & quintptr(1u)) == quintptr(1u)) {
                q_val &= ~quintptr(1u);
                q_lock->unlock();
            }
        }
    }

    inline void relock()
    {
        if (q_lock) {
            if ((q_val & quintptr(1u)) == quintptr(0u)) {
                q_lock->lockForRead();
                q_val |= quintptr(1u);
            }
        }
    }

    inline QReadWriteLock *readWriteLock() const
    { return reinterpret_cast<QReadWriteLock *>(q_val & ~quintptr(1u)); }

private:
    Q_DISABLE_COPY(QReadLocker)
    union {
        QReadWriteLock *q_lock;
        quintptr q_val;
    };
};

inline QReadLocker::QReadLocker(QReadWriteLock *areadWriteLock)
    : q_lock(areadWriteLock)
{
    Q_ASSERT_X((q_val & quintptr(1u)) == quintptr(0),
               "QReadLocker", "QReadWriteLock pointer is misaligned");
    relock();
}

class Q_CORE_EXPORT QWriteLocker
{
public:
    inline QWriteLocker(QReadWriteLock *readWriteLock);

    inline ~QWriteLocker()
    { unlock(); }

    inline void unlock()
    {
        if (q_lock) {
            if ((q_val & quintptr(1u)) == quintptr(1u)) {
                q_val &= ~quintptr(1u);
                q_lock->unlock();
            }
        }
    }

    inline void relock()
    {
        if (q_lock) {
            if ((q_val & quintptr(1u)) == quintptr(0u)) {
                q_lock->lockForWrite();
                q_val |= quintptr(1u);
            }
        }
    }

    inline QReadWriteLock *readWriteLock() const
    { return reinterpret_cast<QReadWriteLock *>(q_val & ~quintptr(1u)); }


private:
    Q_DISABLE_COPY(QWriteLocker)
    union{
        QReadWriteLock *q_lock;
        quintptr q_val;
    };
};

inline QWriteLocker::QWriteLocker(QReadWriteLock *areadWriteLock)
    : q_lock(areadWriteLock)
{
    Q_ASSERT_X((q_val & quintptr(1u)) == quintptr(0),
               "QWriteLocker", "QReadWriteLock pointer is misaligned");
    relock();
}

#if defined(Q_CC_MSVC)
#pragma warning( pop )
#endif

#else // QT_NO_THREAD

class Q_CORE_EXPORT QReadWriteLock
{
public:
    inline explicit QReadWriteLock() { }
    inline ~QReadWriteLock() { }

    static inline void lockForRead() { }
    static inline bool tryLockForRead() { return true; }
    static inline bool tryLockForRead(int timeout) { Q_UNUSED(timeout); return true; }

    static inline void lockForWrite() { }
    static inline bool tryLockForWrite() { return true; }
    static inline bool tryLockForWrite(int timeout) { Q_UNUSED(timeout); return true; }

    static inline void unlock() { }

private:
    Q_DISABLE_COPY(QReadWriteLock)
};

class Q_CORE_EXPORT QReadLocker
{
public:
    inline QReadLocker(QReadWriteLock *) { }
    inline ~QReadLocker() { }

    static inline void unlock() { }
    static inline void relock() { }
    static inline QReadWriteLock *readWriteLock() { return 0; }

private:
    Q_DISABLE_COPY(QReadLocker)
};

class Q_CORE_EXPORT QWriteLocker
{
public:
    inline explicit QWriteLocker(QReadWriteLock *) { }
    inline ~QWriteLocker() { }

    static inline void unlock() { }
    static inline void relock() { }
    static inline QReadWriteLock *readWriteLock() { return 0; }

private:
    Q_DISABLE_COPY(QWriteLocker)
};

#endif // QT_NO_THREAD

QT_END_NAMESPACE

QT_END_HEADER

#endif // QREADWRITELOCK_H