valentina/src/libs/vmisc/vlockguard.h

/************************************************************************
 **
 **  @file   VLockGuard.h
 **  @author Alex Zaharov <alexzkhr@gmail.com>
 **  @author Roman Telezhynskyi <dismine(at)gmail.com>
 **  @date   14 9, 2015
 **
 **  @brief
 **  @copyright
 **  This source code is part of the Valentina project, a pattern making
 **  program, whose allow create and modeling patterns of clothing.
 **  Copyright (C) 2015 Valentina project
 **  <https://gitlab.com/smart-pattern/valentina> All Rights Reserved.
 **
 **  Valentina is free software: you can redistribute it and/or modify
 **  it under the terms of the GNU General Public License as published by
 **  the Free Software Foundation, either version 3 of the License, or
 **  (at your option) any later version.
 **
 **  Valentina is distributed in the hope that it will be useful,
 **  but WITHOUT ANY WARRANTY; without even the implied warranty of
 **  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 **  GNU General Public License for more details.
 **
 **  You should have received a copy of the GNU General Public License
 **  along with Valentina.  If not, see <http://www.gnu.org/licenses/>.
 **
 *************************************************************************/

#ifndef VLOCKGUARD_H
#define VLOCKGUARD_H

#include <QtGlobal>
#ifdef Q_OS_WIN
#include <qt_windows.h>
#endif /*Q_OS_WIN*/

#include <QFileInfo>
#include <QLockFile>
#include <QSharedPointer>
#include <QString>
#include <cstdint>

/*@brief
 * This class creates Guarded object if and only if lock file taken. It keeps shared_ptr to object and lock-file.
 * Can use optional object allocator and deleter.
 *
 * On older Qt lock assumed always taken and compile-time warning is shown.
 *
 */
template <typename Guarded> class VLockGuard
{
public:
    explicit VLockGuard(const QString &lockName, int stale = 0, int timeout = 0);
    ~VLockGuard() = default;

    template <typename Alloc> VLockGuard(const QString &lockName, Alloc a, int stale = 0, int timeout = 0);

    template <typename Alloc, typename Delete>
    VLockGuard(const QString &lockName, Alloc a, Delete d, int stale = 0, int timeout = 0);

    auto GetProtected() const -> const QSharedPointer<Guarded> &;
    auto GetLockError() const -> int;
    auto IsLocked() const -> bool;
    void Unlock();
    auto GetLockFile() const -> QString;

private:
    // cppcheck-suppress unknownMacro
    Q_DISABLE_COPY_MOVE(VLockGuard) // NOLINT

    QSharedPointer<Guarded> holder{};
    int lockError{0};
    QString lockFile{};
    QSharedPointer<QLockFile> lock{};

    auto TryLock(const QString &lockName, int stale, int timeout) -> bool;
};

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> VLockGuard<Guarded>::VLockGuard(const QString &lockName, int stale, int timeout)
{
    if (TryLock(lockName, stale, timeout))
    {
        holder.reset(new Guarded());
    }
}

//---------------------------------------------------------------------------------------------------------------------
// using allocator lambdas seems logically better than supplying pointer, because we will take ownership of allocated
// object
template <typename Guarded>
template <typename Alloc>
VLockGuard<Guarded>::VLockGuard(const QString &lockName, Alloc a, int stale, int timeout)
{
    if (TryLock(lockName, stale, timeout))
    {
        holder.reset(a());
    }
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded>
template <typename Alloc, typename Delete>
VLockGuard<Guarded>::VLockGuard(const QString &lockName, Alloc a, Delete d, int stale, int timeout)
{
    if (TryLock(lockName, stale, timeout))
    {
        holder.reset(a(), d);
    }
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> inline auto VLockGuard<Guarded>::GetProtected() const -> const QSharedPointer<Guarded> &
{
    return holder;
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> inline auto VLockGuard<Guarded>::GetLockError() const -> int
{
    return lockError;
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> inline auto VLockGuard<Guarded>::IsLocked() const -> bool
{
    return !holder.isNull();
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> inline void VLockGuard<Guarded>::Unlock()
{
    if (IsLocked())
    {
        lock->unlock();
    }
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> auto VLockGuard<Guarded>::GetLockFile() const -> QString
{
    return lockFile;
}

//---------------------------------------------------------------------------------------------------------------------
template <typename Guarded> auto VLockGuard<Guarded>::TryLock(const QString &lockName, int stale, int timeout) -> bool
{
    bool res = true;

    lockFile = lockName + QLatin1String(".lock");
#if defined(Q_OS_UNIX) || defined(Q_OS_MACOS)
    {
        QFileInfo info(lockFile);
        lockFile = info.absolutePath() + QLatin1String("/.") + info.fileName();
    }
#endif
    lock.reset(new QLockFile(lockFile));

    lock->setStaleLockTime(stale);
    lock->tryLock(timeout);

    if (QLockFile::LockFailedError == lock->error())
    {
        // This happens if a stale lock file exists and another process uses that PID.
        // Try removing the stale file, which will fail if a real process is holding a
        // file-level lock. A false error is more problematic than not locking properly
        // on corner-case systems.
        lock->removeStaleLockFile();
        lock->tryLock(timeout);
    }
    res = QLockFile::NoError == (lockError = lock->error());
    if (!res)
    {
        lock.reset();
    }
#if defined(Q_OS_WIN)
    else
    {
        SetFileAttributesW(lockFile.toStdWString().c_str(), FILE_ATTRIBUTE_HIDDEN);
    }
#endif
    return res;
}

// use pointer and function below to persistent things like class-member, because lock is taken by constructor
// helper functions allow to write shorter creating and setting new lock-pointer

QT_WARNING_PUSH
QT_WARNING_DISABLE_INTEL(1418)

template <typename Guarded>
void VlpCreateLock(QSharedPointer<VLockGuard<Guarded>> &r, const QString &lockName, int stale = 0, int timeout = 0)
{
    r.reset(new VLockGuard<Guarded>(lockName, stale, timeout));
}

template <typename Guarded, typename Alloc>
void VlpCreateLock(QSharedPointer<VLockGuard<Guarded>> &r, const QString &lockName, Alloc a, int stale = 0,
                   int timeout = 0)
{
    r.reset(new VLockGuard<Guarded>(lockName, a, stale, timeout));
}

template <typename Guarded, typename Alloc, typename Del>
void VlpCreateLock(QSharedPointer<VLockGuard<Guarded>> &r, const QString &lockName, Alloc a, Del d, int stale = 0,
                   int timeout = 0)
{
    r.reset(new VLockGuard<Guarded>(lockName, a, d, stale, timeout));
}

QT_WARNING_POP

#endif // VLOCKGUARD_H