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/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL21$
** 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 The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/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 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** As a special exception, The Qt Company gives you certain additional
** rights. These rights are described in The Qt Company LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qatomic.h"
#include "qmutexpool_p.h"
#ifndef QT_NO_THREAD
QT_BEGIN_NAMESPACE
Q_GLOBAL_STATIC_WITH_ARGS(QMutexPool, globalMutexPool, (QMutex::Recursive))
/*!
\class QMutexPool
\inmodule QtCore
\brief The QMutexPool class provides a pool of QMutex objects.
\internal
\ingroup thread
QMutexPool is a convenience class that provides access to a fixed
number of QMutex objects.
Typical use of a QMutexPool is in situations where it is not
possible or feasible to use one QMutex for every protected object.
The mutex pool will return a mutex based on the address of the
object that needs protection.
For example, consider this simple class:
\snippet code/src_corelib_thread_qmutexpool.cpp 0
Adding a QMutex member to the Number class does not make sense,
because it is so small. However, in order to ensure that access to
each Number is protected, you need to use a mutex. In this case, a
QMutexPool would be ideal.
Code to calculate the square of a number would then look something
like this:
\snippet code/src_corelib_thread_qmutexpool.cpp 1
This function will safely calculate the square of a number, since
it uses a mutex from a QMutexPool. The mutex is locked and
unlocked automatically by the QMutexLocker class. See the
QMutexLocker documentation for more details.
*/
/*!
Constructs a QMutexPool, reserving space for \a size QMutexes. All
mutexes in the pool are created with \a recursionMode. By default,
all mutexes are non-recursive.
The QMutexes are created when needed, and deleted when the
QMutexPool is destructed.
*/
QMutexPool::QMutexPool(QMutex::RecursionMode recursionMode, int size)
: mutexes(size), recursionMode(recursionMode)
{
for (int index = 0; index < mutexes.count(); ++index) {
mutexes[index].store(0);
}
}
/*!
Destructs a QMutexPool. All QMutexes that were created by the pool
are deleted.
*/
QMutexPool::~QMutexPool()
{
for (int index = 0; index < mutexes.count(); ++index)
delete mutexes[index].load();
}
/*!
Returns the global QMutexPool instance.
*/
QMutexPool *QMutexPool::instance()
{
return globalMutexPool();
}
/*!
\fn QMutexPool::get(const void *address)
Returns a QMutex from the pool. QMutexPool uses the value \a address
to determine which mutex is returned from the pool.
*/
/*!
\internal
create the mutex for the given index
*/
QMutex *QMutexPool::createMutex(int index)
{
// mutex not created, create one
QMutex *newMutex = new QMutex(recursionMode);
if (!mutexes[index].testAndSetRelease(0, newMutex))
delete newMutex;
return mutexes[index].load();
}
/*!
Returns a QMutex from the global mutex pool.
*/
QMutex *QMutexPool::globalInstanceGet(const void *address)
{
QMutexPool * const globalInstance = globalMutexPool();
if (globalInstance == 0)
return 0;
return globalInstance->get(address);
}
QT_END_NAMESPACE
#endif // QT_NO_THREAD
|
