1 | /****************************************************************************
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2 | **
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3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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4 | ** All rights reserved.
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5 | ** Contact: Nokia Corporation ([email protected])
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6 | **
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7 | ** This file is part of the examples of the Qt Toolkit.
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8 | **
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9 | ** $QT_BEGIN_LICENSE:BSD$
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10 | ** You may use this file under the terms of the BSD license as follows:
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11 | **
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12 | ** "Redistribution and use in source and binary forms, with or without
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13 | ** modification, are permitted provided that the following conditions are
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14 | ** met:
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15 | ** * Redistributions of source code must retain the above copyright
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16 | ** notice, this list of conditions and the following disclaimer.
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17 | ** * Redistributions in binary form must reproduce the above copyright
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18 | ** notice, this list of conditions and the following disclaimer in
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19 | ** the documentation and/or other materials provided with the
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20 | ** distribution.
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21 | ** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
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22 | ** the names of its contributors may be used to endorse or promote
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23 | ** products derived from this software without specific prior written
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24 | ** permission.
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25 | **
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26 | ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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36 | ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
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37 | ** $QT_END_LICENSE$
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38 | **
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39 | ****************************************************************************/
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40 |
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41 | #include "dialog.h"
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42 | #include <QFileDialog>
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43 | #include <QBuffer>
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44 | #include <QtCore/QDebug>
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45 |
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46 | /*!
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47 | \class Dialog
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48 |
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49 | \brief This class is a simple example of how to use QSharedMemory.
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50 |
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51 | It is a simple dialog that presents a few buttons. To compile the
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52 | example, run make in qt/examples/ipc. Then run the executable twice
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53 | to create two processes running the dialog. In one of the processes,
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54 | press the button to load an image into a shared memory segment, and
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55 | then select an image file to load. Once the first process has loaded
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56 | and displayed the image, in the second process, press the button to
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57 | read the same image from shared memory. The second process displays
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58 | the same image loaded from its new loaction in shared memory.
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59 | */
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60 |
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61 | /*!
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62 | The class contains a data member \l {QSharedMemory} {sharedMemory},
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63 | which is initialized with the key "QSharedMemoryExample" to force
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64 | all instances of Dialog to access the same shared memory segment.
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65 | The constructor also connects the clicked() signal from each of the
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66 | three dialog buttons to the slot function appropriate for handling
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67 | each button.
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68 | */
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69 | //! [0]
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70 | Dialog::Dialog(QWidget *parent)
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71 | : QDialog(parent), sharedMemory("QSharedMemoryExample")
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72 | {
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73 | ui.setupUi(this);
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74 | connect(ui.loadFromFileButton, SIGNAL(clicked()), SLOT(loadFromFile()));
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75 | connect(ui.loadFromSharedMemoryButton,
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76 | SIGNAL(clicked()),
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77 | SLOT(loadFromMemory()));
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78 | setWindowTitle(tr("SharedMemory Example"));
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79 | }
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80 | //! [0]
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81 |
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82 | /*!
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83 | This slot function is called when the \tt {Load Image From File...}
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84 | button is pressed on the firs Dialog process. First, it tests
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85 | whether the process is already connected to a shared memory segment
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86 | and, if so, detaches from that segment. This ensures that we always
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87 | start the example from the beginning if we run it multiple times
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88 | with the same two Dialog processes. After detaching from an existing
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89 | shared memory segment, the user is prompted to select an image file.
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90 | The selected file is loaded into a QImage. The QImage is displayed
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91 | in the Dialog and streamed into a QBuffer with a QDataStream.
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92 |
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93 | Next, it gets a new shared memory segment from the system big enough
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94 | to hold the image data in the QBuffer, and it locks the segment to
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95 | prevent the second Dialog process from accessing it. Then it copies
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96 | the image from the QBuffer into the shared memory segment. Finally,
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