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diff --git a/qmake/tools/qsemaphore_unix.cpp b/qmake/tools/qsemaphore_unix.cpp new file mode 100644 index 0000000..fcf28da --- a/dev/null +++ b/qmake/tools/qsemaphore_unix.cpp @@ -0,0 +1,292 @@ +/**************************************************************************** +** $Id$ +** +** QSemaphore class for Unix +** +** Created : 20010725 +** +** Copyright (C) 1992-2002 Trolltech AS. All rights reserved. +** +** This file is part of the tools module of the Qt GUI Toolkit. +** +** This file may be distributed under the terms of the Q Public License +** as defined by Trolltech AS of Norway and appearing in the file +** LICENSE.QPL included in the packaging of this file. +** +** This file may be distributed and/or modified under the terms of the +** GNU General Public License version 2 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. +** +** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition +** licenses may use this file in accordance with the Qt Commercial License +** Agreement provided with the Software. +** +** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE +** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. +** +** See http://www.trolltech.com/pricing.html or email sales@trolltech.com for +** information about Qt Commercial License Agreements. +** See http://www.trolltech.com/qpl/ for QPL licensing information. +** See http://www.trolltech.com/gpl/ for GPL licensing information. +** +** Contact info@trolltech.com if any conditions of this licensing are +** not clear to you. +** +**********************************************************************/ + +#if defined(QT_THREAD_SUPPORT) + +#include "qsemaphore.h" +#include "qmutex.h" +#include "qwaitcondition.h" + + +/*! + \class QSemaphore qsemaphore.h + \threadsafe + \brief The QSemaphore class provides a robust integer semaphore. + + \ingroup thread + \ingroup environment + + A QSemaphore can be used to serialize thread execution, in a + similar way to a QMutex. A semaphore differs from a mutex, in + that a semaphore can be accessed by more than one thread at a + time. + + For example, suppose we have an application that stores data in a + large tree structure. The application creates 10 threads + (commonly called a thread pool) to perform searches on the tree. + When the application searches the tree for some piece of data, it + uses one thread per base node to do the searching. A semaphore + could be used to make sure that two threads don't try to search + the same branch of the tree at the same time. + + A non-computing example of a semaphore would be dining at a + restuarant. A semaphore is initialized to have a maximum count + equal to the number of chairs in the restuarant. As people + arrive, they want a seat. As seats are filled, the semaphore is + accessed, once per person. As people leave, the access is + released, allowing more people to enter. If a party of 10 people + want to be seated, but there are only 9 seats, those 10 people + will wait, but a party of 4 people would be seated (taking the + available seats to 5, making the party of 10 people wait longer). + + When a semaphore is created it is given a number which is the + maximum number of concurrent accesses it will permit. This amount + may be changed using operator++(), operator--(), operator+=() and + operator-=(). The number of accesses allowed is retrieved with + available(), and the total number with total(). Note that the + incrementing functions will block if there aren't enough available + accesses. Use tryAccess() if you want to acquire accesses without + blocking. +*/ + + +class QSemaphorePrivate { +public: + QSemaphorePrivate(int); + + QMutex mutex; + QWaitCondition cond; + + int value, max; +}; + + +QSemaphorePrivate::QSemaphorePrivate(int m) + : mutex(FALSE), value(0), max(m) +{ +} + + +/*! + Creates a new semaphore. The semaphore can be concurrently + accessed at most \a maxcount times. +*/ +QSemaphore::QSemaphore(int maxcount) +{ + d = new QSemaphorePrivate(maxcount); +} + + +/*! + Destroys the semaphore. + + \warning If you destroy a semaphore that has accesses in use the + resultant behavior is undefined. +*/ +QSemaphore::~QSemaphore() +{ + delete d; +} + + +/*! + Postfix ++ operator. + + Try to get access to the semaphore. If \l available() == 0, this + call will block until it can get access, i.e. until available() \> + 0. +*/ +int QSemaphore::operator++(int) +{ + int ret; + + d->mutex.lock(); + + while (d->value >= d->max) + d->cond.wait(&(d->mutex)); + + ++(d->value); + if (d->value > d->max) d->value = d->max; + ret = d->value; + + d->mutex.unlock(); + + return ret; +} + + +/*! + Postfix -- operator. + + Release access of the semaphore. This wakes all threads waiting + for access to the semaphore. +*/ +int QSemaphore::operator--(int) +{ + int ret; + + d->mutex.lock(); + + --(d->value); + if (d->value < 0) d->value = 0; + ret = d->value; + + d->cond.wakeAll(); + d->mutex.unlock(); + + return ret; +} + + +/*! + Try to get access to the semaphore. If \l available() \< \a n, this + call will block until it can get all the accesses it wants, i.e. + until available() \>= \a n. +*/ +int QSemaphore::operator+=(int n) +{ + int ret; + + d->mutex.lock(); + + while (d->value + n > d->max) + d->cond.wait(&(d->mutex)); + + d->value += n; + +#ifdef QT_CHECK_RANGE + if (d->value > d->max) { + qWarning("QSemaphore::operator+=: attempt to allocate more resources than available"); + d->value = d->max; + } +#endif + + ret = d->value; + + d->mutex.unlock(); + + return ret; +} + + +/*! + Release \a n accesses to the semaphore. +*/ +int QSemaphore::operator-=(int n) +{ + int ret; + + d->mutex.lock(); + + d->value -= n; + +#ifdef QT_CHECK_RANGE + if (d->value < 0) { + qWarning("QSemaphore::operator-=: attempt to deallocate more resources than taken"); + d->value = 0; + } +#endif + + ret = d->value; + + d->cond.wakeOne(); + d->mutex.unlock(); + + return ret; +} + + +/*! + Returns the number of accesses currently available to the + semaphore. +*/ +int QSemaphore::available() const { + int ret; + + d->mutex.lock(); + ret = d->max - d->value; + d->mutex.unlock(); + + return ret; +} + + +/*! + Returns the total number of accesses to the semaphore. +*/ +int QSemaphore::total() const { + int ret; + + d->mutex.lock(); + ret = d->max; + d->mutex.unlock(); + + return ret; +} + + +/*! + Try to get access to the semaphore. If \l available() \< \a n, this + function will return FALSE immediately. If \l available() \>= \a n, + this function will take \a n accesses and return TRUE. This + function does \e not block. +*/ +bool QSemaphore::tryAccess(int n) +{ + if (! d->mutex.tryLock()) + return FALSE; + + if (d->value + n > d->max) { + d->mutex.unlock(); + return FALSE; + } + + d->value += n; + +#ifdef QT_CHECK_RANGE + if (d->value > d->max) { + qWarning("QSemaphore::operator+=: attempt to allocate more resources than available"); + d->value = d->max; + } +#endif + + d->mutex.unlock(); + + return TRUE; +} + +#endif // QT_THREAD_SUPPORT |