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Symbian3/SDK/Source/GUID-C21BB0E4-7AF7-58E5-AAD6-8CE67399460C.dita
changeset 7 51a74ef9ed63
child 8 ae94777fff8f 
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Symbian3/SDK/Source/GUID-C21BB0E4-7AF7-58E5-AAD6-8CE67399460C.dita	Wed Mar 31 11:11:55 2010 +0100
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+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-C21BB0E4-7AF7-58E5-AAD6-8CE67399460C" xml:lang="en"><title>MessageQueue
+Example</title><shortdesc>This example application shows the use of message queue in interprocess
+communication using the RMsgQueue class.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<section id="GUID-ED679CA7-FF4C-4E69-8663-5DA46A3D94F4"><title>Download</title> <p>Click
+on the following link to download the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-d72e85ad-4659-4f66-9cb3-f084e9505709.zip" scope="external">MessageQueueExample.zip</xref>.</p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-d72e85ad-4659-4f66-9cb3-f084e9505709.html" scope="peer">browse</xref> to view the example code.</p> </section>
+<section id="GUID-39D2064D-AD24-4785-956F-18A0CAD57B81"><title>Description</title> <p>The
+example describes the global message queue. The following sections provide
+more information. </p> <p><b> MessageQueueExample</b> </p> <p>The example
+comprises two processes: a Collector, which collects words from the user via
+the console, and an Inverter, which periodically reverses the order of the
+collected words. The Collector and the Inverter pass words to each other using
+two message queues: InverterInQ and InverterOutQ. The Collector is the main
+process which starts the Inverter process. The Collector process takes user
+input in form of different words and sends to the Inverter process via message
+queue. The Inverter process receives messages at a regular interval of 10
+seconds, inverts the words in the message and sends it back to the Collector. </p> <p>The
+Collector creates an active object to collect words from the user and another
+active object to receive words from the Inverter. Each active object has its
+own console for display. More information about running the example is given
+in the build section of this document. </p> <p><b>Design</b> </p> <p>The following
+block diagram describes the example in more detail. </p> <fig id="GUID-27A0C389-EDDD-5E17-82EE-2727F21803AF">
+<image href="GUID-CD7F507C-CDD5-5612-BA1B-72641D28FA4A_d0e257906_href.png" placement="inline"/>
+</fig><p><filepath>CCollector.exe</filepath> is the Collector process. The
+user starts the Collector and creates an active scheduler and two global message
+queues. It also starts the Inverter process called <filepath>Inverter.exe</filepath>.
+The Collector creates one active object to collect words from the user and
+another active object to monitor its input queue (InverterOutQ). The active
+object to collect words is an object of class CCollector and the active object
+which monitors <codeph>InverterOutQ</codeph> is an object of class <xref href="GUID-A39BC295-2845-3018-B8B8-49418277E7EB.dita"><apiname>CMsgQActive</apiname></xref>.
+The two active objects have different consoles (one for user input and one
+for displaying the output message). </p><p> The user inputs words in the console.
+The set of words goes to the <codeph>InverterInQ</codeph> when the "<codeph>Enter</codeph>"
+key is pressed. If the "<codeph>ESC</codeph>" key is pressed, the system stops
+and sends the command to the Inverter process to stop.</p><p> The Inverter
+is another process which opens the global message queues. It creates an active
+scheduler and implements a periodic timer. The timer wakes every 10 seconds
+to receive the words from the <codeph>InverterInQ</codeph>. It also checks
+for a stop command, which closes the message queue and the two process. The
+Inverter inverts the received words and sends the result to <codeph>InverterOutQ</codeph>. </p><p>In
+the Collector process, the active object that monitors the <codeph>InveterOutQ</codeph> opens
+the message queue, receives the received words and displays  them in its console.
+It uses the <xref href="GUID-6E6B3CD0-FB61-336D-9357-2FFBE3F7A57A.dita"><apiname>NotifyDataAvailable()</apiname></xref> API to monitor the queue
+for the next set of data. </p><p>The Class diagram of the example is shown
+below </p><fig id="GUID-E93EF1D6-1B9D-4C76-80B0-1FF660B5C75A">
+<image href="GUID-3560E862-CB68-584F-B9B6-FCD9F0D202DC_d0e257954_href.png" placement="inline"/>
+</fig> </section>
+<section id="GUID-86B04D06-7046-49BD-AE1A-57D5E406F864"><title>Class summary</title><ul>
+<li><p> <xref href="GUID-3CECC9FC-58C1-3117-AAF2-FDF88341F56F.dita"><apiname>CPeriodic</apiname></xref> - Periodic timer active object.</p></li>
+<li><p><xref href="GUID-5195B8D1-851E-3BEE-A72D-1841C0937300.dita"><apiname> RMsgQueue</apiname></xref> - A handle to a message queue.</p></li>
+<li><p><xref href="GUID-9DD1EA2B-DC59-315C-8E9C-CE6D9461B695.dita"><apiname> RProcess</apiname></xref>A handle to a process.</p></li>
+<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>
+</ul></section>
+<section id="GUID-F8D41313-760D-417E-834C-09D41F4EDB06"><title>Build</title> <p>The <xref href="GUID-3100800B-B2F7-50EF-BD4C-3C345ECCB2A5.dita">Symbian build
+process</xref> describes how to build this example application. </p> <p>The
+example builds an executable called <filepath>Inverter.exe</filepath> and <filepath>Collector.exe</filepath> in
+the standard locations. </p> <p>To run the example, first build <filepath>Inverter.exe</filepath> and
+start <filepath>Collector.exe</filepath> from the file system or from your
+IDE. After launching the .exes (and depending on the emulator you are using)
+you may need to navigate away from the application launcher or shell screen
+to view the console. </p> <p>A message input console is used for user input
+and an output message console is used to display inverted words. The output
+message console that is displayed at startup. The user can switch between
+two consoles by <cmdname>Ctrl+Shift+Alt+t </cmdname> combination. </p> <p>The
+input message console is used to input words. A user presses enter to send
+the words to the Inverter and presses <cmdname>ESC</cmdname> to exit the application.
+When a user presses "Enter" the words go to the <codeph>InverterInQ</codeph>.
+The Inverter opens the <codeph>InverterInQ</codeph> at periodic intervals
+of 10 secs and inverts the words which it sends to the collector via <codeph>InverterOutQ</codeph>.
+The Collector opens the <codeph>InverterOutQ</codeph> and display the words
+in the output message console. </p> </section>
+</conbody></concept>
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MCL/sftools/depl/docscontent