<?xml version="1.0" encoding="utf-8"?>+
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<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->+
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<!-- This component and the accompanying materials are made available under the terms of the License +
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"Eclipse Public License v1.0" which accompanies this distribution, +
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and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->+
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<!-- Initial Contributors:+
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    Nokia Corporation - initial contribution.+
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Contributors: +
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-->+
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<!DOCTYPE concept+
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  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">+
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<concept id="GUID-E61A931D-6E66-5E17-AE61-ABFB74CB8EF2" xml:lang="en"><title>Life+
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cycle of active objects</title><shortdesc>This document describes the life cycle of an active objet.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>+
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<p>The diagram illustrates the life-cycle of an active object. </p>+
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<fig id="GUID-BF465AB5-B007-5F44-9AF7-DA0963AE3BDE">+
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<title>Flow diagram showing the life cycle of an active object</title>+
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<image href="GUID-36F18DC4-7BD0-59C6-95E9-8FD945B86D7E_d0e208547_href.png" placement="inline"/>+
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</fig>+
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<p>Procedural flow follows the black arrows; control is transferred along+
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the blue links, as follows:</p>+
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<ul>+
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<li id="GUID-3E3558A3-8C64-515B-A024-81586B472985"><p>the main program creates+
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and installs an active scheduler</p> </li>+
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<li id="GUID-15AE6C3A-5CF7-5711-951A-6FFC8CB6ED27"><p>active objects are created;+
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their constructors ensure that every active object is added to the active+
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scheduler (which keeps a reference to the object in its queue)</p> </li>+
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<li id="GUID-9428DF85-02A3-56C2-A145-604A0356A166"><p>an active object is+
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called to issue an initial request. This sets the object's <codeph>iActive</codeph> true+
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(indicating a request was issued but not yet completed) and schedules the+
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underlying service, which sets the object's <codeph>iStatus</codeph> to <codeph>KRequestPending</codeph>.+
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(If this step is omitted, no service will be requested, so no handler will+
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be invoked and hence the active scheduler will wait forever in its loop, never+
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calling any object's <codeph>RunL()</codeph>)</p> </li>+
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<li id="GUID-48E77554-3EF4-5313-969A-12D3426DA502"><p>the active scheduler+
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is started. This now takes over; control is only returned to the main program+
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for termination when the active scheduler is stopped</p> </li>+
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<li id="GUID-E697E0CF-65F0-5AFD-8201-ADC6A791D98C"><p>when a requested service+
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completes, it's handler terminates by signaling service completion; this alters+
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the associated active object's <codeph>iStatus</codeph> </p> </li>+
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<li id="GUID-CDD9242D-9540-5DC0-A948-8914F2AEF905"><p>when any service handler+
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signals completion, the active scheduler tests each object in its queues for+
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one with <codeph>iActive</codeph> true (request not completed) and <codeph>iStatus</codeph> not+
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set to <codeph>KRequestPending</codeph> (i.e. the request has been handled) </p> </li>+
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<li id="GUID-98980800-03DA-5623-9305-94609FBE9788"><p>if the active scheduler+
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finds an object with the above conditions, it sets <codeph>iActive</codeph> false+
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and calls the object's <codeph>RunL()</codeph> </p> </li>+
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<li id="GUID-CFC4609C-3FED-538E-9555-1A90114876A3"><p>the <codeph>RunL()</codeph> may+
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reschedule the request (so that the handler is again invoked when the requested+
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service completes and the cycle continues.) or may stop the active scheduler,+
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returning control to the main program for termination.</p> </li>+
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</ul>+
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</conbody></concept>+
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