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1 <?xml version="1.0" encoding="utf-8"?> |
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2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. --> |
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3 <!-- This component and the accompanying materials are made available under the terms of the License |
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4 "Eclipse Public License v1.0" which accompanies this distribution, |
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5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". --> |
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6 <!-- Initial Contributors: |
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7 Nokia Corporation - initial contribution. |
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8 Contributors: |
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9 --> |
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10 <!DOCTYPE concept |
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11 PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
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12 <concept id="GUID-3472798D-CEC5-5BA9-A3A7-D4245661DEDB" xml:lang="en"><title>pubsub: |
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13 Using the Publish and Subscribe IPC Mechanism</title><shortdesc>This example demonstrates the Publish and Subscribe IPC mechanisms |
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14 using the <apiname>RProperty</apiname> class. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody> |
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15 <section id="GUID-909438A0-5FCA-4FA3-96EF-2666A3C07227"><title>Download</title> <p>Click on the following link to download |
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16 the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-b24148a4-d20f-4af6-a0d2-d404f1a5698e.zip" scope="external">pubsub.zip</xref>.</p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-b24148a4-d20f-4af6-a0d2-d404f1a5698e.html" scope="peer">browse</xref> to view the example code.</p> </section> |
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17 <section id="GUID-20D6C064-50E0-52EE-8287-1D657C27FF75"><title>Description</title> <p>This |
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18 example demonstrates three types of usage pattern for Publish and Subscribe: </p> <ul> |
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19 <li id="GUID-12170122-3E04-5098-99C3-0C0C6B8C8914"><p>Standard State Publishing </p> <ul> |
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20 <li id="GUID-DA65B928-6F46-5238-AED8-8CE062098621"><p> <b>Publisher:</b> The |
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21 publisher defines a byte-array property and pre-allocates memory to it. It |
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22 interactively updates and re-publishes the value of the property. </p> </li> |
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23 <li id="GUID-0519A68F-E898-5FD7-95C1-A6AA79C5CAE1"><p> <b>Subscriber:</b> The |
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24 subscriber gets the value of the property defined by the publisher by subscribing |
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25 to it. It displays an error and stops running if it fails to get the value |
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26 of the property. </p> </li> |
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27 </ul> </li> |
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28 <li id="GUID-FA0336A7-3402-58BF-A987-BC3273FFB687"><p>Pure Event Distribution </p> <ul> |
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29 <li id="GUID-03D5D3D0-23F5-5E75-840E-70DC8BB74388"><p> <b>Publisher:</b> The |
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30 publisher defines an integer property and publishes a random integer value |
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31 periodically. This value has no significance to the subscriber. </p> </li> |
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32 <li id="GUID-4A3987D9-B916-584A-81C9-DC8079AA1270"><p> <b>Subscriber:</b> The |
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33 subscriber gets a notification when the publisher publishes a value. It exits |
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34 when the property is deleted by the publisher. </p> </li> |
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35 </ul> </li> |
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36 <li id="GUID-FFBD46FD-D0FB-5C9A-98D8-ABA7B8C6E398"><p>Speculative Publishing </p> <ul> |
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37 <li id="GUID-073BA0B9-1682-5642-8929-4B45738F28BD"><p> <b>Publisher:</b> The |
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38 publisher does not define the property. It ignores the <codeph>KErrNotFound</codeph> error |
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39 when it publishes the value of the property. </p> </li> |
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40 <li id="GUID-78B22435-963F-5E5E-9A2B-AC582DD520D4"><p> <b>Subscriber:</b> The |
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41 subscriber defines and subscribes to the property. It ignores the <codeph>KErrAlreadyExists</codeph> error. </p> </li> |
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42 </ul> </li> |
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43 </ul> </section> |
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44 <section id="GUID-63F559E8-36AB-41CD-9A2E-57080EA29601"><title>Class summary</title><ul> |
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45 <li><p><xref href="GUID-C4776034-D190-3FC4-AF45-C7F195093AC3.dita"><apiname>RProperty</apiname></xref> - User side interface to Publish & |
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46 Subscribe.</p></li> |
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47 <li><p><xref href="GUID-067293BF-B28C-3CEC-92F4-1351A795EA7F.dita"><apiname>CActive</apiname></xref> - The core class of the active object abstraction.</p></li> |
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48 </ul></section> |
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49 <section id="GUID-43D665F1-BB55-5D5D-808E-3CBE18D2F6DA"><title>Build</title> <p><xref href="GUID-3100800B-B2F7-50EF-BD4C-3C345ECCB2A5.dita">The Symbian OS build process</xref> describes |
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50 how to build this example. </p> <p>This example builds the following binaries |
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51 in the standard location (<filepath>\epoc32\release\winscw\<build_variant></filepath>) |
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52 for Carbide.c++: </p> <ul> |
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53 <li id="GUID-F06CD099-75C7-5070-89E9-015AAC1F0D9A"><p> <filepath>publishstd.exe</filepath>: |
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54 The publisher process for the Standard State pattern. </p> </li> |
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55 <li id="GUID-772A8A83-743C-5EE5-8D78-F1E8B60B070F"><p> <filepath>subscribestd.exe</filepath>: |
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56 The subscriber process for the Standard State pattern. </p> </li> |
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57 <li id="GUID-19AD84BC-4618-518B-8F46-3DA1B1279B20"><p> <filepath>publishpe.exe</filepath>: |
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58 The publisher process for the Pure Event Distribution pattern. </p> </li> |
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59 <li id="GUID-BDCCB376-3EE5-5F5B-A53D-43F52418E6AA"><p> <filepath>subscribepe.exe</filepath>: |
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60 The subscriber process for the Pure Event Distribution pattern. </p> </li> |
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61 <li id="GUID-9731BBF0-0C21-5739-A9C6-4894E78A6B41"><p> <filepath>publishspec.exe</filepath>: |
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62 The publisher process for the Speculative Publishing pattern. </p> </li> |
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63 <li id="GUID-0897C9AB-A30D-57A7-817C-80750877350C"><p> <filepath>subscribespec.exe</filepath>: |
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64 The subscriber process for the Speculative Publishing pattern. </p> </li> |
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65 </ul> </section> |
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66 <section id="GUID-D8D0CB53-A319-55EA-8650-6F9A74DBDD6C"><title>Running the |
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67 example</title> <p>To run the example, perform the following steps on each |
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68 usage pattern: </p> <ol id="GUID-5BFB2C37-2036-542C-9CD4-672D9D18F25C"> |
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69 <li id="GUID-80B81388-C636-50A0-BCCC-8F6F609E410E"><p>Open two eshells. </p> </li> |
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70 <li id="GUID-A1FF28F1-696E-593C-9FFA-54F5C96F32F2"><p>Run the publisher executable |
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71 file in one eshell. </p> </li> |
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72 <li id="GUID-E3227D02-EB36-518A-8A25-59335A27F062"><p>Run the subscriber executable |
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73 file in another eshell. </p> </li> |
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74 </ol> <p> <b>Note</b>: Switch between eshells by pressing <codeph>CTRL+ALT+SHIFT+T</codeph>. </p> </section> |
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75 <section id="GUID-935115E3-FF46-5EC1-8F36-A6AE35356AD4"><title>See also</title> <p>For |
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76 more information, see <xref href="GUID-A81C65CF-CF4E-571C-8080-9D387F46AAD6.dita">Publish |
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77 and Subscribe</xref> in <i>Using User Library (E32)</i>. </p> </section> |
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78 </conbody></concept> |