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#include "qsystemlock.h"

#include "qsystemlock_p.h"

#include <qdebug.h>

#include <QtCore>

QSystemLockPrivate::QSystemLockPrivate() :

        semaphore(0), semaphoreLock(0),

	lockCount(0), error(QSystemLock::NoError)

{

}

void QSystemLockPrivate::setErrorString(const QString &function)

{

    BOOL windowsError = GetLastError();

    if (windowsError == 0)

        return;

    errorString = function + QLatin1String(": ")

                    + QLatin1String("Unknown error");

    error = QSystemLock::UnknownError;

    qWarning() << errorString << "key" << key << (int)windowsError << semaphore << semaphoreLock;

}

/*!

    \internal

    Setup the semaphore

 */

HANDLE QSystemLockPrivate::handle()

{

    // don't allow making handles on empty keys

    if (key.isEmpty())

        return 0;

    // Create it if it doesn't already exists.

    if (semaphore == 0) {

        QString safeName = makeKeyFileName();

        semaphore = CreateSemaphore(0, MAX_LOCKS, MAX_LOCKS, (wchar_t*)safeName.utf16());

        if (semaphore == 0) {

            setErrorString(QLatin1String("QSystemLockPrivate::handle"));

            return 0;

        }

    }

    if (semaphoreLock == 0) {

        QString safeLockName = QSharedMemoryPrivate::makePlatformSafeKey(key + QLatin1String("lock"), QLatin1String("qipc_systemlock_"));

        semaphoreLock = CreateSemaphore(0, 1, 1, (wchar_t*)safeLockName.utf16());

        if (semaphoreLock == 0) {

            setErrorString(QLatin1String("QSystemLockPrivate::handle"));

            return 0;

        }

    }

    return semaphore;

}

/*!

    \internal

    Cleanup the semaphore

 */

void QSystemLockPrivate::cleanHandle()

{

    if (semaphore && !CloseHandle(semaphore))

        setErrorString(QLatin1String("QSystemLockPrivate::cleanHandle:"));

    if (semaphoreLock && !CloseHandle(semaphoreLock))

        setErrorString(QLatin1String("QSystemLockPrivate::cleanHandle:"));

    semaphore = 0;

    semaphoreLock = 0;

}

bool QSystemLockPrivate::lock(HANDLE handle, int count)

{

    if (count == 1) {

	WaitForSingleObject(handle, INFINITE);

	return true;

    }

    int i = count;

    while (i > 0) {

	if (WAIT_OBJECT_0 == WaitForSingleObject(handle, 0)) {

	    --i;

	} else {

	    // undo what we have done, sleep and then try again later

	    ReleaseSemaphore(handle, (count - i), 0);

	    i = count;

	    ReleaseSemaphore(semaphoreLock, 1, 0);

	    Sleep(1);

	    WaitForSingleObject(semaphoreLock, INFINITE);

	}

    }

    return true;

}

bool QSystemLockPrivate::unlock(HANDLE handle, int count)

{

    if (0 == ReleaseSemaphore(handle, count, 0)) {

        setErrorString(QLatin1String("QSystemLockPrivate::unlock"));

        return false;

    }

    return true;

}

/*!

    \internal

    modifySemaphore handles recursive behavior and modifies the semaphore.

 */

bool QSystemLockPrivate::modifySemaphore(QSystemLockPrivate::Operation op,

        QSystemLock::LockMode mode)

{

    if (0 == handle())

        return false;

    if ((lockCount == 0 && op == Lock) || (lockCount > 0 && op == Unlock)) {

        if (op == Unlock) {

            --lockCount;

            Q_ASSERT(lockCount >= 0);

            if (lockCount > 0)

                return true;

        }

        int count = (mode == QSystemLock::ReadWrite) ? MAX_LOCKS : 1;

        if (op == Lock) {

            lock(semaphoreLock, 1);

            lock(semaphore, count);

            if (count != MAX_LOCKS) unlock(semaphoreLock, 1);

	    lockedMode = mode;

        } else {

            if (count == MAX_LOCKS) unlock(semaphoreLock, 1);

	    unlock(semaphore, count);

        }

    }

    if (op == Lock)

        lockCount++;

    return true;

}