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#include "qwslock_p.h"

#ifndef QT_NO_QWS_MULTIPROCESS

#include "qwssignalhandler_p.h"

#include <qglobal.h>

#include <qdebug.h>

#include <stdio.h>

#include <errno.h>

#include <string.h>

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/sem.h>

#include <sys/time.h>

#include <time.h>

#ifdef Q_OS_LINUX

#include <linux/version.h>

#endif

#include <unistd.h>

QT_BEGIN_NAMESPACE

#ifdef QT_NO_SEMAPHORE

#error QWSLock currently requires semaphores

#endif

#ifndef Q_OS_BSD4

union semun {

    int val;

    struct semid_ds *buf;

    unsigned short *array;

    struct seminfo  *__buf;

};

#endif

QWSLock::QWSLock()

{

    semId = semget(IPC_PRIVATE, 3, IPC_CREAT | 0666);

    if (semId == -1) {

        perror("QWSLock::QWSLock");

        qFatal("Unable to create semaphore");

    }

    QWSSignalHandler::instance()->addSemaphore(semId);

    semun semval;

    semval.val = 1;

    if (semctl(semId, BackingStore, SETVAL, semval) == -1) {

        perror("QWSLock::QWSLock");

        qFatal("Unable to initialize backingstore semaphore");

    }

    lockCount[BackingStore] = 0;

    if (semctl(semId, Communication, SETVAL, semval) == -1) {

        perror("QWSLock::QWSLock");

        qFatal("Unable to initialize communication semaphore");

    }

    lockCount[Communication] = 0;

    semval.val = 0;

    if (semctl(semId, RegionEvent, SETVAL, semval) == -1) {

        perror("QWSLock::QWSLock");

        qFatal("Unable to initialize region event semaphore");

    }

}

QWSLock::QWSLock(int id)

{

    semId = id;

    QWSSignalHandler::instance()->addSemaphore(semId);

    lockCount[0] = lockCount[1] = 0;

}

QWSLock::~QWSLock()

{

    if (semId == -1)

        return;

    QWSSignalHandler::instance()->removeSemaphore(semId);

}

static bool forceLock(int semId, int semNum, int)

{

    int ret;

    do {

        sembuf sops = { semNum, -1, 0 };

        // As the BackingStore lock is a mutex, and only one process may own

        // the lock, it's safe to use SEM_UNDO. On the other hand, the

        // Communication lock is locked by the client but unlocked by the

        // server and therefore can't use SEM_UNDO.

        if (semNum == QWSLock::BackingStore)

            sops.sem_flg |= SEM_UNDO;

        ret = semop(semId, &sops, 1);

        if (ret == -1 && errno != EINTR)

            qDebug("QWSLock::lock: %s", strerror(errno));

    } while (ret == -1 && errno == EINTR);

    return (ret != -1);

}

static bool up(int semId, int semNum)

{

    int ret;

    do {

        sembuf sops = { semNum, 1, 0 };

        ret = semop(semId, &sops, 1);

        if (ret == -1 && errno != EINTR)

            qDebug("QWSLock::up: %s", strerror(errno));

    } while (ret == -1 && errno == EINTR);

    return (ret != -1);

}

static bool down(int semId, int semNum)

{

    int ret;

    do {

        sembuf sops = { semNum, -1, 0 };

        ret = semop(semId, &sops, 1);

        if (ret == -1 && errno != EINTR)

            qDebug("QWSLock::down: %s", strerror(errno));

    } while (ret == -1 && errno == EINTR);

    return (ret != -1);

}

static int getValue(int semId, int semNum)

{

    int ret;

    do {

        ret = semctl(semId, semNum, GETVAL, 0);

        if (ret == -1 && errno != EINTR)

            qDebug("QWSLock::getValue: %s", strerror(errno));

    } while (ret == -1 && errno == EINTR);

    return ret;

}

bool QWSLock::lock(LockType type, int timeout)

{

    if (type == RegionEvent)

        return up(semId, RegionEvent);

    if (hasLock(type)) {

        ++lockCount[type];

        return true;

    }

    if (!forceLock(semId, type, timeout))

        return false;

    ++lockCount[type];

    return true;

}

bool QWSLock::hasLock(LockType type)

{

    if (type == RegionEvent)

        return (getValue(semId, RegionEvent) == 0);

    return (lockCount[type] > 0);

}

void QWSLock::unlock(LockType type)

{

    if (type == RegionEvent) {

        down(semId, RegionEvent);

        return;

    }

    if (hasLock(type)) {

        --lockCount[type];

        if (hasLock(type))

            return;

    }

    const int semNum = type;

    int ret;

    do {

        sembuf sops = {semNum, 1, 0};

        if (semNum == QWSLock::BackingStore)

            sops.sem_flg |= SEM_UNDO;

        ret = semop(semId, &sops, 1);

        if (ret == -1 && errno != EINTR)

            qDebug("QWSLock::unlock: %s", strerror(errno));

    } while (ret == -1 && errno == EINTR);

}

bool QWSLock::wait(LockType type, int timeout)

{

    bool ok = forceLock(semId, type, timeout);

    if (ok)

        unlock(type);

    return ok;

}

QT_END_NAMESPACE

#endif // QT_NO_QWS_MULTIPROCESS