/****************************************************************************+
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**+
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** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).+
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** All rights reserved.+
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** Contact: Nokia Corporation (qt-info@nokia.com)+
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**+
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** This file is part of the QtGui module of the Qt Toolkit.+
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**+
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** $QT_BEGIN_LICENSE:LGPL$+
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** No Commercial Usage+
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** This file contains pre-release code and may not be distributed.+
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** You may use this file in accordance with the terms and conditions+
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** contained in the Technology Preview License Agreement accompanying+
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** this package.+
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**+
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** GNU Lesser General Public License Usage+
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** Alternatively, this file may be used under the terms of the GNU Lesser+
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** General Public License version 2.1 as published by the Free Software+
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** Foundation and appearing in the file LICENSE.LGPL included in the+
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** packaging of this file.  Please review the following information to+
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** ensure the GNU Lesser General Public License version 2.1 requirements+
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.+
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**+
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** In addition, as a special exception, Nokia gives you certain additional+
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** rights.  These rights are described in the Nokia Qt LGPL Exception+
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.+
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**+
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** If you have questions regarding the use of this file, please contact+
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** Nokia at qt-info@nokia.com.+
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**+
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**+
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**+
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**+
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**+
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**+
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**+
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**+
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** $QT_END_LICENSE$+
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**+
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****************************************************************************/+
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+
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#include "qwslock_p.h"+
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+
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#ifndef QT_NO_QWS_MULTIPROCESS+
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+
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#include "qwssignalhandler_p.h"+
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+
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#include <qglobal.h>+
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#include <qdebug.h>+
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#include <stdio.h>+
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#include <errno.h>+
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#include <string.h>+
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#include <sys/types.h>+
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#include <sys/ipc.h>+
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#include <sys/sem.h>+
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#include <sys/time.h>+
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#include <time.h>+
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#ifdef Q_OS_LINUX+
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#include <linux/version.h>+
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#endif+
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#include <unistd.h>+
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+
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QT_BEGIN_NAMESPACE+
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+
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#ifdef QT_NO_SEMAPHORE+
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#error QWSLock currently requires semaphores+
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#endif+
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+
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#ifndef Q_OS_BSD4+
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union semun {+
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    int val;+
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    struct semid_ds *buf;+
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    unsigned short *array;+
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    struct seminfo  *__buf;+
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};+
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#endif+
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+
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QWSLock::QWSLock()+
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{+
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    semId = semget(IPC_PRIVATE, 3, IPC_CREAT | 0666);+
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+
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    if (semId == -1) {+
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        perror("QWSLock::QWSLock");+
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        qFatal("Unable to create semaphore");+
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    }+
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    QWSSignalHandler::instance()->addSemaphore(semId);+
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+
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    semun semval;+
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    semval.val = 1;+
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+
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    if (semctl(semId, BackingStore, SETVAL, semval) == -1) {+
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        perror("QWSLock::QWSLock");+
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        qFatal("Unable to initialize backingstore semaphore");+
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    }+
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    lockCount[BackingStore] = 0;+
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+
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    if (semctl(semId, Communication, SETVAL, semval) == -1) {+
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        perror("QWSLock::QWSLock");+
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        qFatal("Unable to initialize communication semaphore");+
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    }+
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    lockCount[Communication] = 0;+
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+
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    semval.val = 0;+
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    if (semctl(semId, RegionEvent, SETVAL, semval) == -1) {+
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        perror("QWSLock::QWSLock");+
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        qFatal("Unable to initialize region event semaphore");+
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    }+
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}+
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+
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QWSLock::QWSLock(int id)+
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{+
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    semId = id;+
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    QWSSignalHandler::instance()->addSemaphore(semId);+
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    lockCount[0] = lockCount[1] = 0;+
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}+
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+
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QWSLock::~QWSLock()+
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{+
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    if (semId == -1)+
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        return;+
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    QWSSignalHandler::instance()->removeSemaphore(semId);+
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}+
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+
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static bool forceLock(int semId, int semNum, int)+
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{+
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    int ret;+
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    do {+
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        sembuf sops = { semNum, -1, 0 };+
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+
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        // As the BackingStore lock is a mutex, and only one process may own+
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        // the lock, it's safe to use SEM_UNDO. On the other hand, the+
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        // Communication lock is locked by the client but unlocked by the+
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        // server and therefore can't use SEM_UNDO.+
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        if (semNum == QWSLock::BackingStore)+
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            sops.sem_flg |= SEM_UNDO;+
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+
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        ret = semop(semId, &sops, 1);+
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        if (ret == -1 && errno != EINTR)+
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            qDebug("QWSLock::lock: %s", strerror(errno));+
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    } while (ret == -1 && errno == EINTR);+
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+
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    return (ret != -1);+
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}+
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+
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static bool up(int semId, int semNum)+
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{+
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    int ret;+
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    do {+
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        sembuf sops = { semNum, 1, 0 };+
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        ret = semop(semId, &sops, 1);+
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        if (ret == -1 && errno != EINTR)+
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            qDebug("QWSLock::up: %s", strerror(errno));+
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    } while (ret == -1 && errno == EINTR);+
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+
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    return (ret != -1);+
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}+
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+
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static bool down(int semId, int semNum)+
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{+
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    int ret;+
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    do {+
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        sembuf sops = { semNum, -1, 0 };+
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        ret = semop(semId, &sops, 1);+
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        if (ret == -1 && errno != EINTR)+
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            qDebug("QWSLock::down: %s", strerror(errno));+
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    } while (ret == -1 && errno == EINTR);+
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+
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    return (ret != -1);+
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}+
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+
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static int getValue(int semId, int semNum)+
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{+
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    int ret;+
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    do {+
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        ret = semctl(semId, semNum, GETVAL, 0);+
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        if (ret == -1 && errno != EINTR)+
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            qDebug("QWSLock::getValue: %s", strerror(errno));+
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    } while (ret == -1 && errno == EINTR);+
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+
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    return ret;+
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}+
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+
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bool QWSLock::lock(LockType type, int timeout)+
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{+
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    if (type == RegionEvent)+
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        return up(semId, RegionEvent);+
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+
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    if (hasLock(type)) {+
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        ++lockCount[type];+
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        return true;+
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    }+
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+
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    if (!forceLock(semId, type, timeout))+
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        return false;+
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    ++lockCount[type];+
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    return true;+
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}+
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+
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bool QWSLock::hasLock(LockType type)+
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{+
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    if (type == RegionEvent)+
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        return (getValue(semId, RegionEvent) == 0);+
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+
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    return (lockCount[type] > 0);+
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}+
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+
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void QWSLock::unlock(LockType type)+
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{+
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    if (type == RegionEvent) {+
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        down(semId, RegionEvent);+
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        return;+
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    }+
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+
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    if (hasLock(type)) {+
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        --lockCount[type];+
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        if (hasLock(type))+
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            return;+
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    }+
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+
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    const int semNum = type;+
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    int ret;+
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    do {+
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        sembuf sops = {semNum, 1, 0};+
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        if (semNum == QWSLock::BackingStore)+
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            sops.sem_flg |= SEM_UNDO;+
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+
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        ret = semop(semId, &sops, 1);+
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        if (ret == -1 && errno != EINTR)+
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            qDebug("QWSLock::unlock: %s", strerror(errno));+
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    } while (ret == -1 && errno == EINTR);+
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}+
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+
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bool QWSLock::wait(LockType type, int timeout)+
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{+
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    bool ok = forceLock(semId, type, timeout);+
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    if (ok)+
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        unlock(type);+
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    return ok;+
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}+
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+
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QT_END_NAMESPACE+
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+
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#endif // QT_NO_QWS_MULTIPROCESS+
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