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/****************************************************************************
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**
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** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
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** All rights reserved.
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** Contact: Nokia Corporation (qt-info@nokia.com)
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**
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** This file is part of the QtCore module of the Qt Toolkit.
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**
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** $QT_BEGIN_LICENSE:LGPL$
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** No Commercial Usage
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** This file contains pre-release code and may not be distributed.
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** You may use this file in accordance with the terms and conditions
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** contained in the Technology Preview License Agreement accompanying
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** this package.
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**
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** GNU Lesser General Public License Usage
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** Alternatively, this file may be used under the terms of the GNU Lesser
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** General Public License version 2.1 as published by the Free Software
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** Foundation and appearing in the file LICENSE.LGPL included in the
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** packaging of this file. Please review the following information to
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** ensure the GNU Lesser General Public License version 2.1 requirements
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** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.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 LGPL Exception
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** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
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**
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** If you have questions regarding the use of this file, please contact
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** Nokia at qt-info@nokia.com.
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**
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**
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**
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**
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**
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**
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**
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**
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** $QT_END_LICENSE$
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**
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****************************************************************************/
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#include "qsharedmemory.h"
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#include "qsharedmemory_p.h"
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#include "qsystemsemaphore.h"
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#include <qdir.h>
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#include <qcryptographichash.h>
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#ifdef Q_OS_SYMBIAN
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#include <e32const.h>
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#endif
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#include <qdebug.h>
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QT_BEGIN_NAMESPACE
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#if !(defined(QT_NO_SHAREDMEMORY) && defined(QT_NO_SYSTEMSEMAPHORE))
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/*!
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\internal
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Generate a string from the key which can be any unicode string into
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the subset that the win/unix kernel allows.
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On Unix this will be a file name
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On Symbian key will be truncated to 80 characters
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*/
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QString
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QSharedMemoryPrivate::makePlatformSafeKey(const QString &key,
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const QString &prefix)
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{
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if (key.isEmpty())
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return QString();
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QString result = prefix;
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QString part1 = key;
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part1.replace(QRegExp(QLatin1String("[^A-Za-z]")), QString());
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result.append(part1);
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#ifdef Q_OS_SYMBIAN
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return result.left(KMaxKernelName);
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#endif
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QByteArray hex = QCryptographicHash::hash(key.toUtf8(), QCryptographicHash::Sha1).toHex();
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result.append(QLatin1String(hex));
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#ifdef Q_OS_WIN
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return result;
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#else
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return QDir::tempPath() + QLatin1Char('/') + result;
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#endif
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}
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#endif // QT_NO_SHAREDMEMORY && QT_NO_SHAREDMEMORY
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#ifndef QT_NO_SHAREDMEMORY
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/*!
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\class QSharedMemory
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\since 4.4
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\brief The QSharedMemory class provides access to a shared memory segment.
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QSharedMemory provides access to a shared memory segment by multiple
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threads and processes. It also provides a way for a single thread or
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process to lock the memory for exclusive access.
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When using this class, be aware of the following platform
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differences:
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\list
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\o Windows: QSharedMemory does not "own" the shared memory segment.
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When all threads or processes that have an instance of QSharedMemory
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attached to a particular shared memory segment have either destroyed
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their instance of QSharedMemory or exited, the Windows kernel
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releases the shared memory segment automatically.
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\o Unix: QSharedMemory "owns" the shared memory segment. When the
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last thread or process that has an instance of QSharedMemory
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attached to a particular shared memory segment detaches from the
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segment by destroying its instance of QSharedMemory, the Unix kernel
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release the shared memory segment. But if that last thread or
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process crashes without running the QSharedMemory destructor, the
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shared memory segment survives the crash.
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\o HP-UX: Only one attach to a shared memory segment is allowed per
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process. This means that QSharedMemory should not be used across
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multiple threads in the same process in HP-UX.
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\o Symbian: QSharedMemory does not "own" the shared memory segment.
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When all threads or processes that have an instance of QSharedMemory
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attached to a particular shared memory segment have either destroyed
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their instance of QSharedMemory or exited, the Symbian kernel
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releases the shared memory segment automatically.
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Also, access to a shared memory segment cannot be limited to read-only
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in Symbian.
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\endlist
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Remember to lock the shared memory with lock() before reading from
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or writing to the shared memory, and remember to release the lock
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with unlock() after you are done.
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Unlike QtSharedMemory, QSharedMemory automatically destroys the
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shared memory segment when the last instance of QSharedMemory is
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detached from the segment, and no references to the segment
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remain. Do not mix using QtSharedMemory and QSharedMemory. Port
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everything to QSharedMemory.
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\warning QSharedMemory changes the key in a Qt-specific way.
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It is therefore currently not possible to use the shared memory of
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non-Qt applications with QSharedMemory.
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*/
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/*!
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\overload QSharedMemory()
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Constructs a shared memory object with the given \a parent. The
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shared memory object's key is not set by the constructor, so the
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shared memory object does not have an underlying shared memory
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segment attached. The key must be set with setKey() before create()
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or attach() can be used.
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\sa setKey()
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*/
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QSharedMemory::QSharedMemory(QObject *parent)
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: QObject(*new QSharedMemoryPrivate, parent)
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{
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}
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/*!
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Constructs a shared memory object with the given \a parent and with
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its key set to \a key. Because its key is set, its create() and
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attach() functions can be called.
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\sa setKey(), create(), attach()
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*/
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QSharedMemory::QSharedMemory(const QString &key, QObject *parent)
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: QObject(*new QSharedMemoryPrivate, parent)
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{
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setKey(key);
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}
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/*!
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The destructor clears the key, which forces the shared memory object
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to \l {detach()} {detach} from its underlying shared memory
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segment. If this shared memory object is the last one connected to
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the shared memory segment, the detach() operation destroys the
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shared memory segment.
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\sa detach() isAttached()
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*/
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QSharedMemory::~QSharedMemory()
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{
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setKey(QString());
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}
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/*!
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Sets a new \a key for this shared memory object. If \a key and the
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current key are the same, the function returns without doing
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anything. If the shared memory object is attached to an underlying
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shared memory segment, it will \l {detach()} {detach} from it before
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setting the new key. This function does not do an attach().
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\sa key() isAttached()
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*/
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void QSharedMemory::setKey(const QString &key)
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{
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Q_D(QSharedMemory);
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if (key == d->key)
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return;
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if (isAttached())
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detach();
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d->cleanHandle();
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d->key = key;
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}
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bool QSharedMemoryPrivate::initKey()
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{
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if (!cleanHandle())
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return false;
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#ifndef QT_NO_SYSTEMSEMAPHORE
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systemSemaphore.setKey(QString(), 1);
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systemSemaphore.setKey(key, 1);
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if (systemSemaphore.error() != QSystemSemaphore::NoError) {
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QString function = QLatin1String("QSharedMemoryPrivate::initKey");
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errorString = QSharedMemory::tr("%1: unable to set key on lock").arg(function);
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switch(systemSemaphore.error()) {
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case QSystemSemaphore::PermissionDenied:
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error = QSharedMemory::PermissionDenied;
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break;
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case QSystemSemaphore::KeyError:
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error = QSharedMemory::KeyError;
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break;
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case QSystemSemaphore::AlreadyExists:
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error = QSharedMemory::AlreadyExists;
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break;
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case QSystemSemaphore::NotFound:
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error = QSharedMemory::NotFound;
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break;
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case QSystemSemaphore::OutOfResources:
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error = QSharedMemory::OutOfResources;
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break;
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case QSystemSemaphore::UnknownError:
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default:
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error = QSharedMemory::UnknownError;
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break;
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}
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return false;
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}
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#endif
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errorString = QString();
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error = QSharedMemory::NoError;
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return true;
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}
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/*!
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Returns the key assigned to this shared memory. The key is the
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identifier used by the operating system to identify the shared
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memory segment. When QSharedMemory is used for interprocess
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communication, the key is how each process attaches to the shared
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memory segment through which the IPC occurs.
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\sa setKey()
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*/
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QString QSharedMemory::key() const
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{
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Q_D(const QSharedMemory);
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return d->key;
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}
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/*!
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Creates a shared memory segment of \a size bytes with the key passed
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to the constructor or set with setKey(), attaches to the new shared
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memory segment with the given access \a mode, and returns \tt true.
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If a shared memory segment identified by the key already exists, the
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attach operation is not performed, and \tt false is returned. When
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the return value is \tt false, call error() to determine which error
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occurred.
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\sa error()
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*/
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bool QSharedMemory::create(int size, AccessMode mode)
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{
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Q_D(QSharedMemory);
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if (!d->initKey())
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return false;
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#ifndef QT_NO_SYSTEMSEMAPHORE
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#ifndef Q_OS_WIN
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// Take ownership and force set initialValue because the semaphore
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// might have already existed from a previous crash.
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d->systemSemaphore.setKey(d->key, 1, QSystemSemaphore::Create);
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#endif
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#endif
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QString function = QLatin1String("QSharedMemory::create");
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#ifndef QT_NO_SYSTEMSEMAPHORE
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QSharedMemoryLocker lock(this);
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if (!d->tryLocker(&lock, function))
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return false;
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#endif
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if (size <= 0) {
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d->error = QSharedMemory::InvalidSize;
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d->errorString =
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QSharedMemory::tr("%1: create size is less then 0").arg(function);
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return false;
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}
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if (!d->create(size))
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return false;
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return d->attach(mode);
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}
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/*!
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Returns the size of the attached shared memory segment. If no shared
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memory segment is attached, 0 is returned.
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\sa create() attach()
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*/
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int QSharedMemory::size() const
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{
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Q_D(const QSharedMemory);
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return d->size;
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}
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/*!
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\enum QSharedMemory::AccessMode
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\value ReadOnly The shared memory segment is read-only. Writing to
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the shared memory segment is not allowed. An attempt to write to a
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shared memory segment created with ReadOnly causes the program to
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abort.
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\value ReadWrite Reading and writing the shared memory segment are
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both allowed.
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*/
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/*!
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Attempts to attach the process to the shared memory segment
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identified by the key that was passed to the constructor or to a
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call to setKey(). The access \a mode is \l {QSharedMemory::}
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{ReadWrite} by default. It can also be \l {QSharedMemory::}
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{ReadOnly}. Returns true if the attach operation is successful. If
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false is returned, call error() to determine which error occurred.
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After attaching the shared memory segment, a pointer to the shared
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memory can be obtained by calling data().
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\sa isAttached(), detach(), create()
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*/
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bool QSharedMemory::attach(AccessMode mode)
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{
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Q_D(QSharedMemory);
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if (isAttached() || !d->initKey())
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return false;
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#ifndef QT_NO_SYSTEMSEMAPHORE
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QSharedMemoryLocker lock(this);
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if (!d->tryLocker(&lock, QLatin1String("QSharedMemory::attach")))
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return false;
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#endif
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if (isAttached() || !d->handle())
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return false;
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return d->attach(mode);
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}
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/*!
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Returns true if this process is attached to the shared memory
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segment.
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\sa attach(), detach()
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*/
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bool QSharedMemory::isAttached() const
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{
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Q_D(const QSharedMemory);
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return (0 != d->memory);
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}
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/*!
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Detaches the process from the shared memory segment. If this was the
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last process attached to the shared memory segment, then the shared
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memory segment is released by the system, i.e., the contents are
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destroyed. The function returns true if it detaches the shared
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memory segment. If it returns false, it usually means the segment
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either isn't attached, or it is locked by another process.
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\sa attach(), isAttached()
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*/
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bool QSharedMemory::detach()
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{
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Q_D(QSharedMemory);
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if (!isAttached())
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return false;
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#ifndef QT_NO_SYSTEMSEMAPHORE
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QSharedMemoryLocker lock(this);
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if (!d->tryLocker(&lock, QLatin1String("QSharedMemory::detach")))
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return false;
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#endif
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if (d->detach()) {
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d->size = 0;
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return true;
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}
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return false;
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}
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|
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|
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/*!
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410 |
Returns a pointer to the contents of the shared memory segment, if
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one is attached. Otherwise it returns null. Remember to lock the
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shared memory with lock() before reading from or writing to the
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413 |
shared memory, and remember to release the lock with unlock() after
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you are done.
|
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415 |
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\sa attach()
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*/
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void *QSharedMemory::data()
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{
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Q_D(QSharedMemory);
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|
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return d->memory;
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|
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}
|
|
423 |
|
|
424 |
/*!
|
|
425 |
Returns a const pointer to the contents of the shared memory
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segment, if one is attached. Otherwise it returns null. Remember to
|
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427 |
lock the shared memory with lock() before reading from or writing to
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|
428 |
the shared memory, and remember to release the lock with unlock()
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|
429 |
after you are done.
|
|
430 |
|
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431 |
\sa attach() create()
|
|
432 |
*/
|
|
433 |
const void* QSharedMemory::constData() const
|
|
434 |
{
|
|
435 |
Q_D(const QSharedMemory);
|
|
436 |
return d->memory;
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|
437 |
}
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|
438 |
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439 |
/*!
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440 |
\overload data()
|
|
441 |
*/
|
|
442 |
const void *QSharedMemory::data() const
|
|
443 |
{
|
|
444 |
Q_D(const QSharedMemory);
|
|
445 |
return d->memory;
|
|
446 |
}
|
|
447 |
|
|
448 |
#ifndef QT_NO_SYSTEMSEMAPHORE
|
|
449 |
/*!
|
|
450 |
This is a semaphore that locks the shared memory segment for access
|
|
451 |
by this process and returns true. If another process has locked the
|
|
452 |
segment, this function blocks until the lock is released. Then it
|
|
453 |
acquires the lock and returns true. If this function returns false,
|
|
454 |
it means either that you have ignored a false return from create()
|
|
455 |
or attach(), or that QSystemSemaphore::acquire() failed due to an
|
|
456 |
unknown system error.
|
|
457 |
|
|
458 |
\sa unlock(), data(), QSystemSemaphore::acquire()
|
|
459 |
*/
|
|
460 |
bool QSharedMemory::lock()
|
|
461 |
{
|
|
462 |
Q_D(QSharedMemory);
|
|
463 |
if (d->lockedByMe) {
|
|
464 |
qWarning("QSharedMemory::lock: already locked");
|
|
465 |
return true;
|
|
466 |
}
|
|
467 |
if (d->systemSemaphore.acquire()) {
|
|
468 |
d->lockedByMe = true;
|
|
469 |
return true;
|
|
470 |
}
|
|
471 |
QString function = QLatin1String("QSharedMemory::lock");
|
|
472 |
d->errorString = QSharedMemory::tr("%1: unable to lock").arg(function);
|
|
473 |
d->error = QSharedMemory::LockError;
|
|
474 |
return false;
|
|
475 |
}
|
|
476 |
|
|
477 |
/*!
|
|
478 |
Releases the lock on the shared memory segment and returns true, if
|
|
479 |
the lock is currently held by this process. If the segment is not
|
|
480 |
locked, or if the lock is held by another process, nothing happens
|
|
481 |
and false is returned.
|
|
482 |
|
|
483 |
\sa lock()
|
|
484 |
*/
|
|
485 |
bool QSharedMemory::unlock()
|
|
486 |
{
|
|
487 |
Q_D(QSharedMemory);
|
|
488 |
if (!d->lockedByMe)
|
|
489 |
return false;
|
|
490 |
d->lockedByMe = false;
|
|
491 |
if (d->systemSemaphore.release())
|
|
492 |
return true;
|
|
493 |
QString function = QLatin1String("QSharedMemory::unlock");
|
|
494 |
d->errorString = QSharedMemory::tr("%1: unable to unlock").arg(function);
|
|
495 |
d->error = QSharedMemory::LockError;
|
|
496 |
return false;
|
|
497 |
}
|
|
498 |
#endif // QT_NO_SYSTEMSEMAPHORE
|
|
499 |
|
|
500 |
/*!
|
|
501 |
\enum QSharedMemory::SharedMemoryError
|
|
502 |
|
|
503 |
\value NoError No error occurred.
|
|
504 |
|
|
505 |
\value PermissionDenied The operation failed because the caller
|
|
506 |
didn't have the required permissions.
|
|
507 |
|
|
508 |
\value InvalidSize A create operation failed because the requested
|
|
509 |
size was invalid.
|
|
510 |
|
|
511 |
\value KeyError The operation failed because of an invalid key.
|
|
512 |
|
|
513 |
\value AlreadyExists A create() operation failed because a shared
|
|
514 |
memory segment with the specified key already existed.
|
|
515 |
|
|
516 |
\value NotFound An attach() failed because a shared memory segment
|
|
517 |
with the specified key could not be found.
|
|
518 |
|
|
519 |
\value LockError The attempt to lock() the shared memory segment
|
|
520 |
failed because create() or attach() failed and returned false, or
|
|
521 |
because a system error occurred in QSystemSemaphore::acquire().
|
|
522 |
|
|
523 |
\value OutOfResources A create() operation failed because there was
|
|
524 |
not enough memory available to fill the request.
|
|
525 |
|
|
526 |
\value UnknownError Something else happened and it was bad.
|
|
527 |
*/
|
|
528 |
|
|
529 |
/*!
|
|
530 |
Returns a value indicating whether an error occurred, and, if so,
|
|
531 |
which error it was.
|
|
532 |
|
|
533 |
\sa errorString()
|
|
534 |
*/
|
|
535 |
QSharedMemory::SharedMemoryError QSharedMemory::error() const
|
|
536 |
{
|
|
537 |
Q_D(const QSharedMemory);
|
|
538 |
return d->error;
|
|
539 |
}
|
|
540 |
|
|
541 |
/*!
|
|
542 |
Returns a text description of the last error that occurred. If
|
|
543 |
error() returns an \l {QSharedMemory::SharedMemoryError} {error
|
|
544 |
value}, call this function to get a text string that describes the
|
|
545 |
error.
|
|
546 |
|
|
547 |
\sa error()
|
|
548 |
*/
|
|
549 |
QString QSharedMemory::errorString() const
|
|
550 |
{
|
|
551 |
Q_D(const QSharedMemory);
|
|
552 |
return d->errorString;
|
|
553 |
}
|
|
554 |
|
|
555 |
#endif // QT_NO_SHAREDMEMORY
|
|
556 |
|
|
557 |
QT_END_NAMESPACE
|