/****************************************************************************

**

** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).

** All rights reserved.

** Contact: Nokia Corporation (qt-info@nokia.com)

**

** This file is part of the QtCore module of the Qt Toolkit.

**

** $QT_BEGIN_LICENSE:LGPL$

** GNU Lesser General Public License Usage

** This file may be used under the terms of the GNU Lesser General Public

** License version 2.1 as published by the Free Software Foundation and

** appearing in the file LICENSE.LGPL included in the packaging of this

** file. Please review the following information to ensure the GNU Lesser

** General Public License version 2.1 requirements will be met:

** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.

**

** In addition, as a special exception, Nokia gives you certain additional

** rights. These rights are described in the Nokia Qt LGPL Exception

** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.

**

** GNU General Public License Usage

** Alternatively, this file may be used under the terms of the GNU General

** Public License version 3.0 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 the GNU General

** Public License version 3.0 requirements will be met:

** http://www.gnu.org/copyleft/gpl.html.

**

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** conditions contained in a signed written agreement between you and Nokia.

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** $QT_END_LICENSE$

**

****************************************************************************/

#include "qcore_unix_p.h"

#include "qelapsedtimer.h"

#ifdef Q_OS_NACL

#elif !defined (Q_OS_VXWORKS)

# if !defined(Q_OS_HPUX) || defined(__ia64)

#  include <sys/select.h>

# endif

#  include <sys/time.h>

#else

#  include <selectLib.h>

#endif

#include <stdlib.h>

#ifdef Q_OS_MAC

#include <mach/mach_time.h>

#endif

QT_BEGIN_NAMESPACE

static inline bool time_update(struct timeval *tv, const struct timeval &start,

                               const struct timeval &timeout)

{

    if (!QElapsedTimer::isMonotonic()) {

        // we cannot recalculate the timeout without a monotonic clock as the time may have changed

        return false;

    }

    // clock source is monotonic, so we can recalculate how much timeout is left

    struct timeval now = qt_gettime();

    *tv = timeout + start - now;

    return tv->tv_sec >= 0;

}

int qt_safe_select(int nfds, fd_set *fdread, fd_set *fdwrite, fd_set *fdexcept,

                   const struct timeval *orig_timeout)

{

    if (!orig_timeout) {

        // no timeout -> block forever

        register int ret;

        EINTR_LOOP(ret, select(nfds, fdread, fdwrite, fdexcept, 0));

        return ret;

    }

    timeval start = qt_gettime();

    timeval timeout = *orig_timeout;

    // loop and recalculate the timeout as needed

    int ret;

    forever {

        ret = ::select(nfds, fdread, fdwrite, fdexcept, &timeout);

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

            return ret;

        // recalculate the timeout

        if (!time_update(&timeout, start, *orig_timeout)) {

            // timeout during update

            // or clock reset, fake timeout error

            return 0;

        }

    }

}

QT_END_NAMESPACE