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/***************************************************************************
**
** This file is part of Qt Creator
**
** Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).
**
** Contact: Qt Software Information (qt-info@nokia.com)
**
**
** Non-Open Source Usage
**
** Licensees may use this file in accordance with the Qt Beta Version
** License Agreement, Agreement version 2.2 provided with the Software or,
** alternatively, in accordance with the terms contained in a written
** agreement between you and Nokia.
**
** GNU General Public License Usage
**
** Alternatively, this file may be used under the terms of the GNU General
** Public License versions 2.0 or 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 GNU
** General Public Licensing requirements will be met:
**
** http://www.fsf.org/licensing/licenses/info/GPLv2.html and
** http://www.gnu.org/copyleft/gpl.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights. These rights are described in the Nokia Qt GPL Exception version
** 1.2, included in the file GPL_EXCEPTION.txt in this package.
**
***************************************************************************/
#include "qtlockedfile.h"
namespace SharedTools {
/*!
\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
QtLockedFile. 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()
*/
QtLockedFile::QtLockedFile()
: QFile()
{
#ifdef Q_OS_WIN
m_semaphore_hnd = 0;
m_mutex_hnd = 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()
*/
QtLockedFile::QtLockedFile(const QString &name)
: QFile(name)
{
#ifdef Q_OS_WIN
m_semaphore_hnd = 0;
m_mutex_hnd = 0;
#endif
m_lock_mode = NoLock;
}
/*!
Returns \e true if this object has a in read or write lock;
otherwise returns \e false.
\sa lockMode()
*/
bool QtLockedFile::isLocked() const
{
return m_lock_mode != NoLock;
}
/*!
Returns the type of lock currently held by this object, or \e QtLockedFile::NoLock.
\sa isLocked()
*/
QtLockedFile::LockMode QtLockedFile::lockMode() const
{
return m_lock_mode;
}
/*!
\fn bool QtLockedFile::lock(LockMode mode, bool block = true)
Obtains a lock of type \a mode.
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.
*/
} // namespace SharedTools
|
