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/**************************************************************************
**
** This file is part of Qt Creator
**
** Copyright (c) 2011 Nokia Corporation and/or its subsidiary(-ies).
**
** Contact: Nokia Corporation (info@qt.nokia.com)
**
**
** 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.
**
** 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.
**
** If you have questions regarding the use of this file, please contact
** Nokia at info@qt.nokia.com.
**
**************************************************************************/
#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 acquired. If \a block is
false, this function returns \e false immediately if the lock cannot
be acquired.
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
|
