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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, 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 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 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 the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/
#include "qsharedmemory.h"
#include "qsharedmemory_p.h"
#include "qsystemsemaphore.h"
#include <qdir.h>
#include <qcryptographichash.h>
#include <qdebug.h>
QT_BEGIN_NAMESPACE
#if !(defined(QT_NO_SHAREDMEMORY) && defined(QT_NO_SYSTEMSEMAPHORE))
/*!
\internal
Generate a string from the key which can be any unicode string into
the subset that the win/unix kernel allows.
On Unix this will be a file name
*/
QString
QSharedMemoryPrivate::makePlatformSafeKey(const QString &key,
const QString &prefix)
{
if (key.isEmpty())
return QString();
QString result = prefix;
QString part1 = key;
part1.replace(QRegExp(QLatin1String("[^A-Za-z]")), QString());
result.append(part1);
QByteArray hex = QCryptographicHash::hash(key.toUtf8(), QCryptographicHash::Sha1).toHex();
result.append(QLatin1String(hex));
#ifdef Q_OS_WIN
return result;
#else
return QDir::tempPath() + QLatin1Char('/') + result;
#endif
}
#endif // QT_NO_SHAREDMEMORY && QT_NO_SHAREDMEMORY
#ifndef QT_NO_SHAREDMEMORY
/*!
\class QSharedMemory
\ingroup ipc
\since 4.4
\brief The QSharedMemory class provides access to a shared memory segment.
QSharedMemory provides access to a shared memory segment by multiple
threads and processes. It also provides a way for a single thread or
process to lock the memory for exclusive access.
When using this class, be aware of the following platform
differences:
\list
\o Windows: QSharedMemory does not "own" the shared memory segment.
When all threads or processes that have an instance of QSharedMemory
attached to a particular shared memory segment have either destroyed
their instance of QSharedMemory or exited, the Windows kernel
releases the shared memory segment automatically.
\o Unix: QSharedMemory "owns" the shared memory segment. When the
last thread or process that has an instance of QSharedMemory
attached to a particular shared memory segment detaches from the
segment by destroying its instance of QSharedMemory, the Unix kernel
release the shared memory segment. But if that last thread or
process crashes without running the QSharedMemory destructor, the
shared memory segment survives the crash.
\o HP-UX: Only one attach to a shared memory segment is allowed per
process. This means that QSharedMemory should not be used across
multiple threads in the same process in HP-UX.
\endlist
Remember to lock the shared memory with lock() before reading from
or writing to the shared memory, and remember to release the lock
with unlock() after you are done.
Unlike QtSharedMemory, QSharedMemory automatically destroys the
shared memory segment when the last instance of QSharedMemory is
detached from the segment, and no references to the segment
remain. Do not mix using QtSharedMemory and QSharedMemory. Port
everything to QSharedMemory.
*/
/*!
\overload QSharedMemory()
Constructs a shared memory object with the given \a parent. The
shared memory object's key is not set by the constructor, so the
shared memory object does not have an underlying shared memory
segment attached. The key must be set with setKey() before create()
or attach() can be used.
\sa setKey()
*/
QSharedMemory::QSharedMemory(QObject *parent)
: QObject(*new QSharedMemoryPrivate, parent)
{
}
/*!
Constructs a shared memory object with the given \a parent and with
its key set to \a key. Because its key is set, its create() and
attach() functions can be called.
\sa setKey(), create(), attach()
*/
QSharedMemory::QSharedMemory(const QString &key, QObject *parent)
: QObject(*new QSharedMemoryPrivate, parent)
{
setKey(key);
}
/*!
The destructor clears the key, which forces the shared memory object
to \l {detach()} {detach} from its underlying shared memory
segment. If this shared memory object is the last one connected to
the shared memory segment, the detach() operation destroys the
shared memory segment.
\sa detach() isAttached()
*/
QSharedMemory::~QSharedMemory()
{
setKey(QString());
}
/*!
Sets a new \a key for this shared memory object. If \a key and the
current key are the same, the function returns without doing
anything. If the shared memory object is attached to an underlying
shared memory segment, it will \l {detach()} {detach} from it before
setting the new key. This function does not do an attach().
\sa key() isAttached()
*/
void QSharedMemory::setKey(const QString &key)
{
Q_D(QSharedMemory);
if (key == d->key)
return;
if (isAttached())
detach();
d->cleanHandle();
d->key = key;
}
bool QSharedMemoryPrivate::initKey()
{
if (!cleanHandle())
return false;
#ifndef QT_NO_SYSTEMSEMAPHORE
systemSemaphore.setKey(QString(), 1);
systemSemaphore.setKey(key, 1);
if (systemSemaphore.error() != QSystemSemaphore::NoError) {
QString function = QLatin1String("QSharedMemoryPrivate::initKey");
errorString = QSharedMemory::tr("%1: unable to set key on lock").arg(function);
switch(systemSemaphore.error()) {
case QSystemSemaphore::PermissionDenied:
error = QSharedMemory::PermissionDenied;
break;
case QSystemSemaphore::KeyError:
error = QSharedMemory::KeyError;
break;
case QSystemSemaphore::AlreadyExists:
error = QSharedMemory::AlreadyExists;
break;
case QSystemSemaphore::NotFound:
error = QSharedMemory::NotFound;
break;
case QSystemSemaphore::OutOfResources:
error = QSharedMemory::OutOfResources;
break;
case QSystemSemaphore::UnknownError:
default:
error = QSharedMemory::UnknownError;
break;
}
return false;
}
#endif
errorString = QString();
error = QSharedMemory::NoError;
return true;
}
/*!
Returns the key assigned to this shared memory. The key is the
identifier used by the operating system to identify the shared
memory segment. When QSharedMemory is used for interprocess
communication, the key is how each process attaches to the shared
memory segment through which the IPC occurs.
\sa setKey()
*/
QString QSharedMemory::key() const
{
Q_D(const QSharedMemory);
return d->key;
}
/*!
Creates a shared memory segment of \a size bytes with the key passed
to the constructor or set with setKey(), attaches to the new shared
memory segment with the given access \a mode, and returns \tt true.
If a shared memory segment identified by the key already exists, the
attach operation is not performed, and \tt false is returned. When
the return value is \tt false, call error() to determine which error
occurred.
\sa error()
*/
bool QSharedMemory::create(int size, AccessMode mode)
{
Q_D(QSharedMemory);
if (!d->initKey())
return false;
#ifndef QT_NO_SYSTEMSEMAPHORE
#ifndef Q_OS_WIN
// Take ownership and force set initialValue because the semaphore
// might have already existed from a previous crash.
d->systemSemaphore.setKey(d->key, 1, QSystemSemaphore::Create);
#endif
#endif
QString function = QLatin1String("QSharedMemory::create");
#ifndef QT_NO_SYSTEMSEMAPHORE
QSharedMemoryLocker lock(this);
if (!d->tryLocker(&lock, function))
return false;
#endif
if (size <= 0) {
d->error = QSharedMemory::InvalidSize;
d->errorString =
QSharedMemory::tr("%1: create size is less then 0").arg(function);
return false;
}
if (!d->create(size))
return false;
return d->attach(mode);
}
/*!
Returns the size of the attached shared memory segment. If no shared
memory segment is attached, 0 is returned.
\sa create() attach()
*/
int QSharedMemory::size() const
{
Q_D(const QSharedMemory);
return d->size;
}
/*!
\enum QSharedMemory::AccessMode
\value ReadOnly The shared memory segment is read-only. Writing to
the shared memory segment is not allowed. An attempt to write to a
shared memory segment created with ReadOnly causes the program to
abort.
\value ReadWrite Reading and writing the shared memory segment are
both allowed.
*/
/*!
Attempts to attach the process to the shared memory segment
identified by the key that was passed to the constructor or to a
call to setKey(). The access \a mode is \l {QSharedMemory::}
{ReadWrite} by default. It can also be \l {QSharedMemory::}
{ReadOnly}. Returns true if the attach operation is successful. If
false is returned, call error() to determine which error occurred.
After attaching the shared memory segment, a pointer to the shared
memory can be obtained by calling data().
\sa isAttached(), detach(), create()
*/
bool QSharedMemory::attach(AccessMode mode)
{
Q_D(QSharedMemory);
if (isAttached() || !d->initKey())
return false;
#ifndef QT_NO_SYSTEMSEMAPHORE
QSharedMemoryLocker lock(this);
if (!d->tryLocker(&lock, QLatin1String("QSharedMemory::attach")))
return false;
#endif
if (isAttached() || !d->handle())
return false;
return d->attach(mode);
}
/*!
Returns true if this process is attached to the shared memory
segment.
\sa attach(), detach()
*/
bool QSharedMemory::isAttached() const
{
Q_D(const QSharedMemory);
return (0 != d->memory);
}
/*!
Detaches the process from the shared memory segment. If this was the
last process attached to the shared memory segment, then the shared
memory segment is released by the system, i.e., the contents are
destroyed. The function returns true if it detaches the shared
memory segment. If it returns false, it usually means the segment
either isn't attached, or it is locked by another process.
\sa attach(), isAttached()
*/
bool QSharedMemory::detach()
{
Q_D(QSharedMemory);
if (!isAttached())
return false;
#ifndef QT_NO_SYSTEMSEMAPHORE
QSharedMemoryLocker lock(this);
if (!d->tryLocker(&lock, QLatin1String("QSharedMemory::detach")))
return false;
#endif
if (d->detach()) {
d->size = 0;
return true;
}
return false;
}
/*!
Returns a pointer to the contents of the shared memory segment, if
one is attached. Otherwise it returns null. Remember to lock the
shared memory with lock() before reading from or writing to the
shared memory, and remember to release the lock with unlock() after
you are done.
\sa attach()
*/
void *QSharedMemory::data()
{
Q_D(QSharedMemory);
return d->memory;
}
/*!
Returns a const pointer to the contents of the shared memory
segment, if one is attached. Otherwise it returns null. Remember to
lock the shared memory with lock() before reading from or writing to
the shared memory, and remember to release the lock with unlock()
after you are done.
\sa attach() create()
*/
const void* QSharedMemory::constData() const
{
Q_D(const QSharedMemory);
return d->memory;
}
/*!
\overload data()
*/
const void *QSharedMemory::data() const
{
Q_D(const QSharedMemory);
return d->memory;
}
#ifndef QT_NO_SYSTEMSEMAPHORE
/*!
This is a semaphore that locks the shared memory segment for access
by this process and returns true. If another process has locked the
segment, this function blocks until the lock is released. Then it
acquires the lock and returns true. If this function returns false,
it means either that you have ignored a false return from create()
or attach(), or that QSystemSemaphore::acquire() failed due to an
unknown system error.
\sa unlock(), data(), QSystemSemaphore::acquire()
*/
bool QSharedMemory::lock()
{
Q_D(QSharedMemory);
if (d->lockedByMe) {
qWarning("QSharedMemory::lock: already locked");
return true;
}
if (d->systemSemaphore.acquire()) {
d->lockedByMe = true;
return true;
}
QString function = QLatin1String("QSharedMemory::lock");
d->errorString = QSharedMemory::tr("%1: unable to lock").arg(function);
d->error = QSharedMemory::LockError;
return false;
}
/*!
Releases the lock on the shared memory segment and returns true, if
the lock is currently held by this process. If the segment is not
locked, or if the lock is held by another process, nothing happens
and false is returned.
\sa lock()
*/
bool QSharedMemory::unlock()
{
Q_D(QSharedMemory);
if (!d->lockedByMe)
return false;
d->lockedByMe = false;
if (d->systemSemaphore.release())
return true;
QString function = QLatin1String("QSharedMemory::unlock");
d->errorString = QSharedMemory::tr("%1: unable to unlock").arg(function);
d->error = QSharedMemory::LockError;
return false;
}
#endif // QT_NO_SYSTEMSEMAPHORE
/*!
\enum QSharedMemory::SharedMemoryError
\value NoError No error occurred.
\value PermissionDenied The operation failed because the caller
didn't have the required permissions.
\value InvalidSize A create operation failed because the requested
size was invalid.
\value KeyError The operation failed because of an invalid key.
\value AlreadyExists A create() operation failed because a shared
memory segment with the specified key already existed.
\value NotFound An attach() failed because a shared memory segment
with the specified key could not be found.
\value LockError The attempt to lock() the shared memory segment
failed because create() or attach() failed and returned false, or
because a system error occurred in QSystemSemaphore::acquire().
\value OutOfResources A create() operation failed because there was
not enough memory available to fill the request.
\value UnknownError Something else happened and it was bad.
*/
/*!
Returns a value indicating whether an error occurred, and, if so,
which error it was.
\sa errorString()
*/
QSharedMemory::SharedMemoryError QSharedMemory::error() const
{
Q_D(const QSharedMemory);
return d->error;
}
/*!
Returns a text description of the last error that occurred. If
error() returns an \l {QSharedMemory::SharedMemoryError} {error
value}, call this function to get a text string that describes the
error.
\sa error()
*/
QString QSharedMemory::errorString() const
{
Q_D(const QSharedMemory);
return d->errorString;
}
#endif // QT_NO_SHAREDMEMORY
QT_END_NAMESPACE
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