NOISSUE refactor window management and launch, make MultiMC a single instance application.

libraries/LocalPeer/src/LockedFile.cpp

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+/****************************************************************************
+**
+** Copyright (C) 2013 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the Qt Solutions component.
+**
+** $QT_BEGIN_LICENSE:BSD$
+** You may use this file under the terms of the BSD license as follows:
+**
+** "Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions are
+** met:
+**   * Redistributions of source code must retain the above copyright
+**     notice, this list of conditions and the following disclaimer.
+**   * Redistributions in binary form must reproduce the above copyright
+**     notice, this list of conditions and the following disclaimer in
+**     the documentation and/or other materials provided with the
+**     distribution.
+**   * Neither the name of Digia Plc and its Subsidiary(-ies) nor the names
+**     of its contributors may be used to endorse or promote products derived
+**     from this software without specific prior written permission.
+**
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "LockedFile.h"
+
+/*!
+	\class QtLockedFile
+
+	\brief The QtLockedFile class extends QFile with advisory locking
+	functions.
+
+	A file may be locked in read or write mode. Multiple instances of
+	\e QtLockedFile, created in multiple processes running on the same
+	machine, may have a file locked in read mode. Exactly one instance
+	may have it locked in write mode. A read and a write lock cannot
+	exist simultaneously on the same file.
+
+	The file locks are advisory. This means that nothing prevents
+	another process from manipulating a locked file using QFile or
+	file system functions offered by the OS. Serialization is only
+	guaranteed if all processes that access the file use
+	QLockedFile. Also, while holding a lock on a file, a process
+	must not open the same file again (through any API), or locks
+	can be unexpectedly lost.
+
+	The lock provided by an instance of \e QtLockedFile is released
+	whenever the program terminates. This is true even when the
+	program crashes and no destructors are called.
+*/
+
+/*! \enum QtLockedFile::LockMode
+
+	This enum describes the available lock modes.
+
+	\value ReadLock A read lock.
+	\value WriteLock A write lock.
+	\value NoLock Neither a read lock nor a write lock.
+*/
+
+/*!
+	Constructs an unlocked \e QtLockedFile object. This constructor
+	behaves in the same way as \e QFile::QFile().
+
+	\sa QFile::QFile()
+*/
+LockedFile::LockedFile()
+	: QFile()
+{
+#ifdef Q_OS_WIN
+	wmutex = 0;
+	rmutex = 0;
+#endif
+	m_lock_mode = NoLock;
+}
+
+/*!
+	Constructs an unlocked QtLockedFile object with file \a name. This
+	constructor behaves in the same way as \e QFile::QFile(const
+	QString&).
+
+	\sa QFile::QFile()
+*/
+LockedFile::LockedFile(const QString &name)
+	: QFile(name)
+{
+#ifdef Q_OS_WIN
+	wmutex = 0;
+	rmutex = 0;
+#endif
+	m_lock_mode = NoLock;
+}
+
+/*!
+Opens the file in OpenMode \a mode.
+
+This is identical to QFile::open(), with the one exception that the
+Truncate mode flag is disallowed. Truncation would conflict with the
+advisory file locking, since the file would be modified before the
+write lock is obtained. If truncation is required, use resize(0)
+after obtaining the write lock.
+
+Returns true if successful; otherwise false.
+
+\sa QFile::open(), QFile::resize()
+*/
+bool LockedFile::open(OpenMode mode)
+{
+	if (mode & QIODevice::Truncate) {
+		qWarning("QtLockedFile::open(): Truncate mode not allowed.");
+		return false;
+	}
+	return QFile::open(mode);
+}
+
+/*!
+	Returns \e true if this object has a in read or write lock;
+	otherwise returns \e false.
+
+	\sa lockMode()
+*/
+bool LockedFile::isLocked() const
+{
+	return m_lock_mode != NoLock;
+}
+
+/*!
+	Returns the type of lock currently held by this object, or \e
+	QtLockedFile::NoLock.
+
+	\sa isLocked()
+*/
+LockedFile::LockMode LockedFile::lockMode() const
+{
+	return m_lock_mode;
+}
+
+/*!
+	\fn bool QtLockedFile::lock(LockMode mode, bool block = true)
+
+	Obtains a lock of type \a mode. The file must be opened before it
+	can be locked.
+
+	If \a block is true, this function will block until the lock is
+	aquired. If \a block is false, this function returns \e false
+	immediately if the lock cannot be aquired.
+
+	If this object already has a lock of type \a mode, this function
+	returns \e true immediately. If this object has a lock of a
+	different type than \a mode, the lock is first released and then a
+	new lock is obtained.
+
+	This function returns \e true if, after it executes, the file is
+	locked by this object, and \e false otherwise.
+
+	\sa unlock(), isLocked(), lockMode()
+*/
+
+/*!
+	\fn bool QtLockedFile::unlock()
+
+	Releases a lock.
+
+	If the object has no lock, this function returns immediately.
+
+	This function returns \e true if, after it executes, the file is
+	not locked by this object, and \e false otherwise.
+
+	\sa lock(), isLocked(), lockMode()
+*/
+
+/*!
+	\fn QtLockedFile::~QtLockedFile()
+
+	Destroys the \e QtLockedFile object. If any locks were held, they
+	are released.
+*/