1 <?xml version="1.0" encoding="utf-8"?>

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     7     Nokia Corporation - initial contribution.

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    10 <!DOCTYPE concept

    11   PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">

    12 <concept id="GUID-E61A931D-6E66-5E17-AE61-ABFB74CB8EF2" xml:lang="en"><title>Life

    13 cycle of active objects</title><shortdesc>This document describes the life cycle of an active objet.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>The diagram illustrates the life-cycle of an active object. </p>

    15 <fig id="GUID-BF465AB5-B007-5F44-9AF7-DA0963AE3BDE">

    16 <title>Flow diagram showing the life cycle of an active object</title>

    17 <image href="GUID-36F18DC4-7BD0-59C6-95E9-8FD945B86D7E_d0e208547_href.png" placement="inline"/>

    18 </fig>

    19 <p>Procedural flow follows the black arrows; control is transferred along

    20 the blue links, as follows:</p>

    21 <ul>

    22 <li id="GUID-3E3558A3-8C64-515B-A024-81586B472985"><p>the main program creates

    23 and installs an active scheduler</p> </li>

    24 <li id="GUID-15AE6C3A-5CF7-5711-951A-6FFC8CB6ED27"><p>active objects are created;

    25 their constructors ensure that every active object is added to the active

    26 scheduler (which keeps a reference to the object in its queue)</p> </li>

    27 <li id="GUID-9428DF85-02A3-56C2-A145-604A0356A166"><p>an active object is

    28 called to issue an initial request. This sets the object's <codeph>iActive</codeph> true

    29 (indicating a request was issued but not yet completed) and schedules the

    30 underlying service, which sets the object's <codeph>iStatus</codeph> to <codeph>KRequestPending</codeph>.

    31 (If this step is omitted, no service will be requested, so no handler will

    32 be invoked and hence the active scheduler will wait forever in its loop, never

    33 calling any object's <codeph>RunL()</codeph>)</p> </li>

    34 <li id="GUID-48E77554-3EF4-5313-969A-12D3426DA502"><p>the active scheduler

    35 is started. This now takes over; control is only returned to the main program

    36 for termination when the active scheduler is stopped</p> </li>

    37 <li id="GUID-E697E0CF-65F0-5AFD-8201-ADC6A791D98C"><p>when a requested service

    38 completes, it's handler terminates by signaling service completion; this alters

    39 the associated active object's <codeph>iStatus</codeph> </p> </li>

    40 <li id="GUID-CDD9242D-9540-5DC0-A948-8914F2AEF905"><p>when any service handler

    41 signals completion, the active scheduler tests each object in its queues for

    42 one with <codeph>iActive</codeph> true (request not completed) and <codeph>iStatus</codeph> not

    43 set to <codeph>KRequestPending</codeph> (i.e. the request has been handled) </p> </li>

    44 <li id="GUID-98980800-03DA-5623-9305-94609FBE9788"><p>if the active scheduler

    45 finds an object with the above conditions, it sets <codeph>iActive</codeph> false

    46 and calls the object's <codeph>RunL()</codeph> </p> </li>

    47 <li id="GUID-CFC4609C-3FED-538E-9555-1A90114876A3"><p>the <codeph>RunL()</codeph> may

    48 reschedule the request (so that the handler is again invoked when the requested

    49 service completes and the cycle continues.) or may stop the active scheduler,

    50 returning control to the main program for termination.</p> </li>

    51 </ul>

    52 </conbody></concept>