/******************************************************************************** Copyright (C) 1992-2006 Trolltech ASA. All rights reserved.**** This file is part of the QtCore module of the Qt Toolkit.**** This file may be used under the terms of the GNU General Public** License version 2.0 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 GNU** General Public Licensing requirements will be met:** http://www.trolltech.com/products/qt/opensource.html**** If you are unsure which license is appropriate for your use, please** review the following information:** http://www.trolltech.com/products/qt/licensing.html or contact the** sales department at sales@trolltech.com.**** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.******************************************************************************/#include "qmutexpool_p.h"#ifndef QT_NO_THREADQ_CORE_EXPORT QMutexPool *qt_global_mutexpool = 0;/*!    \class QMutexPool qmutexpool_p.h    \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:    \code    class Number {    public:        Number(double n) : num (n) { }        void setNumber(double n) { num = n; }        double number() const { return num; }    private:        double num;    };    \endcode    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:    \code    void calcSquare(Number *num)    {        QMutexLocker locker(mutexpool.get(num));        num.setNumber(num.number() * num.number());    }    \endcode    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. If    \a recursive is true, all QMutexes in the pool will be recursive    mutexes; otherwise they will all be non-recursive (the default).    The QMutexes are created when needed, and deleted when the    QMutexPool is destructed.*/QMutexPool::QMutexPool(bool recursive, int size)    : count(size), recurs(recursive){    mutexes = new QMutex*[count];    for (int index = 0; index < count; ++index) {        mutexes[index] = 0;    }}/*!    Destructs a QMutexPool. All QMutexes that were created by the pool    are deleted.*/QMutexPool::~QMutexPool(){    QMutexLocker locker(&mutex);    for (int index = 0; index < count; ++index) {        delete mutexes[index];        mutexes[index] = 0;    }    delete [] mutexes;    mutexes = 0;}/*!    Returns a QMutex from the pool. QMutexPool uses the value \a address    to determine which mutex is returned from the pool.*/QMutex *QMutexPool::get(const void *address){    Q_ASSERT_X(address != 0, "QMutexPool::get()", "'address' argument cannot be zero");    int index = int((ulong(address) >> (sizeof(address) >> 1)) % count);    if (!mutexes[index]) {        // mutex not created, create one        QMutexLocker locker(&mutex);        // we need to check once again that the mutex hasn't been created, since        // 2 threads could be trying to create a mutex at the same index...        if (!mutexes[index])            mutexes[index] = new QMutex(recurs ? QMutex::Recursive : QMutex::NonRecursive);    }    return mutexes[index];}#endif // QT_NO_THREAD