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37a66b2340
git-svn-id: svn://svn.openpilot.org/OpenPilot/trunk@281 ebee16cc-31ac-478f-84a7-5cbb03baadba
158 lines
4.6 KiB
C++
158 lines
4.6 KiB
C++
/**
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******************************************************************************
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*
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* @file qtlockedfile.cpp
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* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2010.
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* Parts by Nokia Corporation (qt-info@nokia.com) Copyright (C) 2009.
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* @brief
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* @see The GNU Public License (GPL) Version 3
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* @defgroup
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* @{
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*
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*****************************************************************************/
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/*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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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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