--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/ipc/sharedmemory/dialog.cpp Mon Jan 11 14:00:40 2010 +0000
@@ -0,0 +1,189 @@
+/****************************************************************************
+**
+** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the examples 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 Technology Preview License Agreement accompanying
+** this package.
+**
+** 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 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+**
+**
+**
+**
+**
+**
+**
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "dialog.h"
+#include <QFileDialog>
+#include <QBuffer>
+#include <QtCore/QDebug>
+
+/*!
+ \class Dialog
+
+ \brief This class is a simple example of how to use QSharedMemory.
+
+ It is a simple dialog that presents a few buttons. To compile the
+ example, run make in qt/examples/ipc. Then run the executable twice
+ to create two processes running the dialog. In one of the processes,
+ press the button to load an image into a shared memory segment, and
+ then select an image file to load. Once the first process has loaded
+ and displayed the image, in the second process, press the button to
+ read the same image from shared memory. The second process displays
+ the same image loaded from its new loaction in shared memory.
+*/
+
+/*!
+ The class contains a data member \l {QSharedMemory} {sharedMemory},
+ which is initialized with the key "QSharedMemoryExample" to force
+ all instances of Dialog to access the same shared memory segment.
+ The constructor also connects the clicked() signal from each of the
+ three dialog buttons to the slot function appropriate for handling
+ each button.
+*/
+//! [0]
+Dialog::Dialog(QWidget *parent)
+ : QDialog(parent), sharedMemory("QSharedMemoryExample")
+{
+ ui.setupUi(this);
+ connect(ui.loadFromFileButton, SIGNAL(clicked()), SLOT(loadFromFile()));
+ connect(ui.loadFromSharedMemoryButton,
+ SIGNAL(clicked()),
+ SLOT(loadFromMemory()));
+ setWindowTitle(tr("SharedMemory Example"));
+}
+//! [0]
+
+/*!
+ This slot function is called when the \tt {Load Image From File...}
+ button is pressed on the firs Dialog process. First, it tests
+ whether the process is already connected to a shared memory segment
+ and, if so, detaches from that segment. This ensures that we always
+ start the example from the beginning if we run it multiple times
+ with the same two Dialog processes. After detaching from an existing
+ shared memory segment, the user is prompted to select an image file.
+ The selected file is loaded into a QImage. The QImage is displayed
+ in the Dialog and streamed into a QBuffer with a QDataStream.
+
+ Next, it gets a new shared memory segment from the system big enough
+ to hold the image data in the QBuffer, and it locks the segment to
+ prevent the second Dialog process from accessing it. Then it copies
+ the image from the QBuffer into the shared memory segment. Finally,
+ it unlocks the shared memory segment so the second Dialog process
+ can access it.
+
+ After this function runs, the user is expected to press the \tt
+ {Load Image from Shared Memory} button on the second Dialog process.
+
+ \sa loadFromMemory()
+ */
+//! [1]
+void Dialog::loadFromFile()
+{
+ if (sharedMemory.isAttached())
+ detach();
+
+ ui.label->setText(tr("Select an image file"));
+ QString fileName = QFileDialog::getOpenFileName(0, QString(), QString(),
+ tr("Images (*.png *.xpm *.jpg)"));
+ QImage image;
+ if (!image.load(fileName)) {
+ ui.label->setText(tr("Selected file is not an image, please select another."));
+ return;
+ }
+ ui.label->setPixmap(QPixmap::fromImage(image));
+//! [1] //! [2]
+
+ // load into shared memory
+ QBuffer buffer;
+ buffer.open(QBuffer::ReadWrite);
+ QDataStream out(&buffer);
+ out << image;
+ int size = buffer.size();
+
+ if (!sharedMemory.create(size)) {
+ ui.label->setText(tr("Unable to create shared memory segment."));
+ return;
+ }
+ sharedMemory.lock();
+ char *to = (char*)sharedMemory.data();
+ const char *from = buffer.data().data();
+ memcpy(to, from, qMin(sharedMemory.size(), size));
+ sharedMemory.unlock();
+}
+//! [2]
+
+/*!
+ This slot function is called in the second Dialog process, when the
+ user presses the \tt {Load Image from Shared Memory} button. First,
+ it attaches the process to the shared memory segment created by the
+ first Dialog process. Then it locks the segment for exclusive
+ access, copies the image data from the segment into a QBuffer, and
+ streams the QBuffer into a QImage. Then it unlocks the shared memory
+ segment, detaches from it, and finally displays the QImage in the
+ Dialog.
+
+ \sa loadFromFile()
+ */
+//! [3]
+void Dialog::loadFromMemory()
+{
+ if (!sharedMemory.attach()) {
+ ui.label->setText(tr("Unable to attach to shared memory segment.\n" \
+ "Load an image first."));
+ return;
+ }
+
+ QBuffer buffer;
+ QDataStream in(&buffer);
+ QImage image;
+
+ sharedMemory.lock();
+ buffer.setData((char*)sharedMemory.constData(), sharedMemory.size());
+ buffer.open(QBuffer::ReadOnly);
+ in >> image;
+ sharedMemory.unlock();
+
+ sharedMemory.detach();
+ ui.label->setPixmap(QPixmap::fromImage(image));
+}
+//! [3]
+
+/*!
+ This private function is called by the destructor to detach the
+ process from its shared memory segment. When the last process
+ detaches from a shared memory segment, the system releases the
+ shared memory.
+ */
+void Dialog::detach()
+{
+ if (!sharedMemory.detach())
+ ui.label->setText(tr("Unable to detach from shared memory."));
+}
+