forked from qt-creator/qt-creator
163 lines
4.7 KiB
C++
163 lines
4.7 KiB
C++
/***************************************************************************
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**
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** This file is part of Qt Creator
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**
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** Copyright (c) 2008 Nokia Corporation and/or its subsidiary(-ies).
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**
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** Contact: Qt Software Information (qt-info@nokia.com)
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**
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**
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** Non-Open Source Usage
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**
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** Licensees may use this file in accordance with the Qt Beta Version
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** License Agreement, Agreement version 2.2 provided with the Software or,
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** alternatively, in accordance with the terms contained in a written
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** agreement between you and Nokia.
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**
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** GNU General Public License Usage
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**
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** Alternatively, this file may be used under the terms of the GNU General
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** Public License versions 2.0 or 3.0 as published by the Free Software
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** Foundation and appearing in the file LICENSE.GPL included in the packaging
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** of this file. Please review the following information to ensure GNU
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** General Public Licensing requirements will be met:
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**
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** http://www.fsf.org/licensing/licenses/info/GPLv2.html and
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** http://www.gnu.org/copyleft/gpl.html.
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**
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** In addition, as a special exception, Nokia gives you certain additional
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** rights. These rights are described in the Nokia Qt GPL Exception version
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** 1.2, included in the file GPL_EXCEPTION.txt in this package.
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**
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***************************************************************************/
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#include "qtlockedfile.h"
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namespace SharedTools {
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/*!
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\class QtLockedFile
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\brief The QtLockedFile class extends QFile with advisory locking functions.
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A file may be locked in read or write mode. Multiple instances of
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\e QtLockedFile, created in multiple processes running on the same
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machine, may have a file locked in read mode. Exactly one instance
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may have it locked in write mode. A read and a write lock cannot
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exist simultaneously on the same file.
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The file locks are advisory. This means that nothing prevents
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another process from manipulating a locked file using QFile or
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file system functions offered by the OS. Serialization is only
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guaranteed if all processes that access the file use
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QtLockedFile. Also, while holding a lock on a file, a process
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must not open the same file again (through any API), or locks
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can be unexpectedly lost.
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The lock provided by an instance of \e QtLockedFile is released
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whenever the program terminates. This is true even when the
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program crashes and no destructors are called.
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*/
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/*! \enum QtLockedFile::LockMode
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This enum describes the available lock modes.
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\value ReadLock A read lock.
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\value WriteLock A write lock.
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\value NoLock Neither a read lock nor a write lock.
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*/
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/*!
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Constructs an unlocked \e QtLockedFile object. This constructor behaves in the same way
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as \e QFile::QFile().
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\sa QFile::QFile()
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*/
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QtLockedFile::QtLockedFile()
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: QFile()
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{
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#ifdef Q_OS_WIN
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m_semaphore_hnd = 0;
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m_mutex_hnd = 0;
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#endif
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m_lock_mode = NoLock;
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}
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/*!
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Constructs an unlocked QtLockedFile object with file \a name. This constructor behaves in
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the same way as \e QFile::QFile(const QString&).
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\sa QFile::QFile()
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*/
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QtLockedFile::QtLockedFile(const QString &name)
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: QFile(name)
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{
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#ifdef Q_OS_WIN
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m_semaphore_hnd = 0;
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m_mutex_hnd = 0;
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#endif
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m_lock_mode = NoLock;
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}
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/*!
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Returns \e true if this object has a in read or write lock;
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otherwise returns \e false.
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\sa lockMode()
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*/
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bool QtLockedFile::isLocked() const
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{
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return m_lock_mode != NoLock;
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}
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/*!
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Returns the type of lock currently held by this object, or \e QtLockedFile::NoLock.
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\sa isLocked()
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*/
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QtLockedFile::LockMode QtLockedFile::lockMode() const
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{
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return m_lock_mode;
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}
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/*!
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\fn bool QtLockedFile::lock(LockMode mode, bool block = true)
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Obtains a lock of type \a mode.
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If \a block is true, this
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function will block until the lock is aquired. If \a block is
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false, this function returns \e false immediately if the lock cannot
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be aquired.
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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
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is first released and then a new lock is obtained.
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This function returns \e true if, after it executes, the file is locked by this object,
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and \e false otherwise.
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\sa unlock(), isLocked(), lockMode()
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*/
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/*!
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\fn bool QtLockedFile::unlock()
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Releases a lock.
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If the object has no lock, this function returns immediately.
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This function returns \e true if, after it executes, the file is not locked by
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this object, and \e false otherwise.
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\sa lock(), isLocked(), lockMode()
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*/
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/*!
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\fn QtLockedFile::~QtLockedFile()
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Destroys the \e QtLockedFile object. If any locks were held, they are released.
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*/
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} // namespace SharedTools
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