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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-E61A931D-6E66-5E17-AE61-ABFB74CB8EF2" xml:lang="en"><title>Life |
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13 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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14 <p>The diagram illustrates the life-cycle of an active object. </p> |
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15 <fig id="GUID-BF465AB5-B007-5F44-9AF7-DA0963AE3BDE"> |
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16 <title>Flow diagram showing the life cycle of an active object</title> |
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17 <image href="GUID-36F18DC4-7BD0-59C6-95E9-8FD945B86D7E_d0e237164_href.png" placement="inline"/> |
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18 </fig> |
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19 <p>Procedural flow follows the black arrows; control is transferred along |
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20 the blue links, as follows:</p> |
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21 <ul> |
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22 <li id="GUID-3E3558A3-8C64-515B-A024-81586B472985"><p>the main program creates |
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23 and installs an active scheduler</p> </li> |
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24 <li id="GUID-15AE6C3A-5CF7-5711-951A-6FFC8CB6ED27"><p>active objects are created; |
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25 their constructors ensure that every active object is added to the active |
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26 scheduler (which keeps a reference to the object in its queue)</p> </li> |
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27 <li id="GUID-9428DF85-02A3-56C2-A145-604A0356A166"><p>an active object is |
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28 called to issue an initial request. This sets the object's <codeph>iActive</codeph> true |
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29 (indicating a request was issued but not yet completed) and schedules the |
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30 underlying service, which sets the object's <codeph>iStatus</codeph> to <codeph>KRequestPending</codeph>. |
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31 (If this step is omitted, no service will be requested, so no handler will |
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32 be invoked and hence the active scheduler will wait forever in its loop, never |
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33 calling any object's <codeph>RunL()</codeph>)</p> </li> |
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34 <li id="GUID-48E77554-3EF4-5313-969A-12D3426DA502"><p>the active scheduler |
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35 is started. This now takes over; control is only returned to the main program |
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36 for termination when the active scheduler is stopped</p> </li> |
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37 <li id="GUID-E697E0CF-65F0-5AFD-8201-ADC6A791D98C"><p>when a requested service |
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38 completes, it's handler terminates by signaling service completion; this alters |
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39 the associated active object's <codeph>iStatus</codeph> </p> </li> |
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40 <li id="GUID-CDD9242D-9540-5DC0-A948-8914F2AEF905"><p>when any service handler |
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41 signals completion, the active scheduler tests each object in its queues for |
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42 one with <codeph>iActive</codeph> true (request not completed) and <codeph>iStatus</codeph> not |
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43 set to <codeph>KRequestPending</codeph> (i.e. the request has been handled) </p> </li> |
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44 <li id="GUID-98980800-03DA-5623-9305-94609FBE9788"><p>if the active scheduler |
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45 finds an object with the above conditions, it sets <codeph>iActive</codeph> false |
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46 and calls the object's <codeph>RunL()</codeph> </p> </li> |
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47 <li id="GUID-CFC4609C-3FED-538E-9555-1A90114876A3"><p>the <codeph>RunL()</codeph> may |
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48 reschedule the request (so that the handler is again invoked when the requested |
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49 service completes and the cycle continues.) or may stop the active scheduler, |
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50 returning control to the main program for termination.</p> </li> |
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51 </ul> |
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52 </conbody></concept> |