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

**

** 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.

**

** Other Usage

** Alternatively, this file may be used in accordance with the terms and

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

**

**

**

**

**

** $QT_END_LICENSE$

**

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

#include "qsystemsemaphore.h"

#include "qsystemsemaphore_p.h"

#include <qcoreapplication.h>

#include <qdebug.h>

#include <qfile.h>

#ifndef QT_NO_SYSTEMSEMAPHORE

#include <sys/types.h>

#include <sys/ipc.h>

#ifndef QT_POSIX_IPC

#include <sys/sem.h>

#endif

#include <fcntl.h>

#include <errno.h>

#include "private/qcore_unix_p.h"

// OpenBSD 4.2 doesn't define EIDRM, see BUGS section:

// http://www.openbsd.org/cgi-bin/man.cgi?query=semop&manpath=OpenBSD+4.2

#if defined(Q_OS_OPENBSD) && !defined(EIDRM)

#define EIDRM EINVAL

#endif

//#define QSYSTEMSEMAPHORE_DEBUG

QT_BEGIN_NAMESPACE

QSystemSemaphorePrivate::QSystemSemaphorePrivate() :

#ifndef QT_POSIX_IPC

    unix_key(-1), semaphore(-1), createdFile(false),

#else

    semaphore(SEM_FAILED),

#endif

    createdSemaphore(false), error(QSystemSemaphore::NoError)

{

}

void QSystemSemaphorePrivate::setErrorString(const QString &function)

{

    // EINVAL is handled in functions so they can give better error strings

    switch (errno) {

    case EPERM:

    case EACCES:

        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: permission denied").arg(function);

        error = QSystemSemaphore::PermissionDenied;

        break;

    case EEXIST:

        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: already exists").arg(function);

        error = QSystemSemaphore::AlreadyExists;

        break;

    case ENOENT:

        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: does not exist").arg(function);

        error = QSystemSemaphore::NotFound;

        break;

    case ERANGE:

    case ENOMEM:

    case ENOSPC:

    case EMFILE:

    case ENFILE:

    case EOVERFLOW:

        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: out of resources").arg(function);

        error = QSystemSemaphore::OutOfResources;

        break;

    case ENAMETOOLONG:

        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: name error").arg(function);

        error = QSystemSemaphore::KeyError;

        break;

    default:

        errorString = QCoreApplication::translate("QSystemSemaphore", "%1: unknown error %2").arg(function).arg(errno);

        error = QSystemSemaphore::UnknownError;

#ifdef QSYSTEMSEMAPHORE_DEBUG

        qDebug() << errorString << "key" << key << "errno" << errno << EINVAL;

#endif

        break;

    }

}

/*!

    \internal

    Initialise the semaphore

*/

#ifndef QT_POSIX_IPC

key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)

{

    if (-1 != unix_key)

        return unix_key;

    if (key.isEmpty()) {

        errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));

        error = QSystemSemaphore::KeyError;

        return -1;

    }

    // ftok requires that an actual file exists somewhere

    int built = QSharedMemoryPrivate::createUnixKeyFile(fileName);

    if (-1 == built) {

        errorString = QCoreApplication::tr("%1: unable to make key", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));

        error = QSystemSemaphore::KeyError;

        return -1;

    }

    createdFile = (1 == built);

    // Get the unix key for the created file

    unix_key = ftok(QFile::encodeName(fileName).constData(), 'Q');

    if (-1 == unix_key) {

        errorString = QCoreApplication::tr("%1: ftok failed", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));

        error = QSystemSemaphore::KeyError;

        return -1;

    }

    // Get semaphore

    semaphore = semget(unix_key, 1, 0666 | IPC_CREAT | IPC_EXCL);

    if (-1 == semaphore) {

        if (errno == EEXIST)

            semaphore = semget(unix_key, 1, 0666 | IPC_CREAT);

        if (-1 == semaphore) {

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

            cleanHandle();

            return -1;

        }

        if (mode == QSystemSemaphore::Create) {

            createdSemaphore = true;

            createdFile = true;

        }

    } else {

        createdSemaphore = true;

        // Force cleanup of file, it is possible that it can be left over from a crash

        createdFile = true;

    }

    // Created semaphore so initialize its value.

    if (createdSemaphore && initialValue >= 0) {

        qt_semun init_op;

        init_op.val = initialValue;

        if (-1 == semctl(semaphore, 0, SETVAL, init_op)) {

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

            cleanHandle();

            return -1;

        }

    }

    return unix_key;

}

#else

bool QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)

{

    if (semaphore != SEM_FAILED)

        return true;  // we already have a semaphore

    if (fileName.isEmpty()) {

        errorString = QCoreApplication::tr("%1: key is empty", "QSystemSemaphore").arg(QLatin1String("QSystemSemaphore::handle"));

        error = QSystemSemaphore::KeyError;

        return false;

    }

    QByteArray semName = QFile::encodeName(fileName);

    // Always try with O_EXCL so we know whether we created the semaphore.

    int oflag = O_CREAT | O_EXCL;

    for (int tryNum = 0, maxTries = 1; tryNum < maxTries; ++tryNum) {

        do {

            semaphore = sem_open(semName.constData(), oflag, 0666, initialValue);

        } while (semaphore == SEM_FAILED && errno == EINTR);

        if (semaphore == SEM_FAILED && errno == EEXIST) {

            if (mode == QSystemSemaphore::Create) {

                if (sem_unlink(semName.constData()) == -1 && errno != ENOENT) {

                    setErrorString(QLatin1String("QSystemSemaphore::handle (sem_unlink)"));

                    return false;

                }

                // Race condition: the semaphore might be recreated before

                // we call sem_open again, so we'll retry several times.

                maxTries = 3;

            } else {

                // Race condition: if it no longer exists at the next sem_open

                // call, we won't realize we created it, so we'll leak it later.

                oflag &= ~O_EXCL;

                maxTries = 2;

            }

        } else {

            break;

        }

    }

    if (semaphore == SEM_FAILED) {

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

        return false;

    }

    createdSemaphore = (oflag & O_EXCL) != 0;

    return true;

}

#endif // QT_POSIX_IPC

/*!

    \internal

    Clean up the semaphore

*/

void QSystemSemaphorePrivate::cleanHandle()

{

#ifndef QT_POSIX_IPC

    unix_key = -1;

    // remove the file if we made it

    if (createdFile) {

        QFile::remove(fileName);

        createdFile = false;

    }

    if (createdSemaphore) {

        if (-1 != semaphore) {

            if (-1 == semctl(semaphore, 0, IPC_RMID, 0)) {

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

#ifdef QSYSTEMSEMAPHORE_DEBUG

                qDebug("QSystemSemaphore::cleanHandle semctl failed.");

#endif

            }

            semaphore = -1;

        }

        createdSemaphore = false;

    }

#else

    if (semaphore != SEM_FAILED) {

        if (sem_close(semaphore) == -1) {

            setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_close)"));

#ifdef QSYSTEMSEMAPHORE_DEBUG

            qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_close failed.");

#endif

        }

        semaphore = SEM_FAILED;

    }

    if (createdSemaphore) {

        if (sem_unlink(QFile::encodeName(fileName).constData()) == -1 && errno != ENOENT) {

            setErrorString(QLatin1String("QSystemSemaphore::cleanHandle (sem_unlink)"));

#ifdef QSYSTEMSEMAPHORE_DEBUG

            qDebug() << QLatin1String("QSystemSemaphore::cleanHandle sem_unlink failed.");

#endif

        }

        createdSemaphore = false;

    }

#endif // QT_POSIX_IPC

}

/*!

    \internal

*/

bool QSystemSemaphorePrivate::modifySemaphore(int count)

{

#ifndef QT_POSIX_IPC

    if (-1 == handle())

        return false;

    struct sembuf operation;

    operation.sem_num = 0;

    operation.sem_op = count;

    operation.sem_flg = SEM_UNDO;

    register int res;

    EINTR_LOOP(res, semop(semaphore, &operation, 1));

    if (-1 == res) {

        // If the semaphore was removed be nice and create it and then modifySemaphore again

        if (errno == EINVAL || errno == EIDRM) {

            semaphore = -1;

            cleanHandle();

            handle();

            return modifySemaphore(count);

        }

        setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore"));

#ifdef QSYSTEMSEMAPHORE_DEBUG

        qDebug() << QLatin1String("QSystemSemaphore::modify failed") << count << semctl(semaphore, 0, GETVAL) << errno << EIDRM << EINVAL;

#endif

        return false;

    }

#else

    if (!handle())

        return false;

    if (count > 0) {

        int cnt = count;

        do {

            if (sem_post(semaphore) == -1) {

                setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_post)"));

#ifdef QSYSTEMSEMAPHORE_DEBUG

                qDebug() << QLatin1String("QSystemSemaphore::modify sem_post failed") << count << errno;

#endif

                // rollback changes to preserve the SysV semaphore behavior

                for ( ; cnt < count; ++cnt) {

                    register int res;

                    EINTR_LOOP(res, sem_wait(semaphore));

                }

                return false;

            }

            --cnt;

        } while (cnt > 0);

    } else {

        register int res;

        EINTR_LOOP(res, sem_wait(semaphore));

        if (res == -1) {

            // If the semaphore was removed be nice and create it and then modifySemaphore again

            if (errno == EINVAL || errno == EIDRM) {

                semaphore = SEM_FAILED;

                return modifySemaphore(count);

            }

            setErrorString(QLatin1String("QSystemSemaphore::modifySemaphore (sem_wait)"));

#ifdef QSYSTEMSEMAPHORE_DEBUG

            qDebug() << QLatin1String("QSystemSemaphore::modify sem_wait failed") << count << errno;

#endif

            return false;

        }

    }

#endif // QT_POSIX_IPC

    return true;

}

QT_END_NAMESPACE

#endif // QT_NO_SYSTEMSEMAPHORE