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

     2 <!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->

     3 <!-- This component and the accompanying materials are made available under the terms of the License 

     4 "Eclipse Public License v1.0" which accompanies this distribution, 

     5 and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->

     6 <!-- Initial Contributors:

     7     Nokia Corporation - initial contribution.

     8 Contributors: 

     9 -->

    10 <!DOCTYPE concept

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

    12 <concept id="GUID-E6D9F8CA-F293-5CE6-93C4-5FEC5EBCB2E9" xml:lang="en"><title>Asynchronous

    13 service provider's responsibilities</title><shortdesc>This document describes the functionality required from an asynchronous

    14 service provider.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    15 <p>An asynchronous service provider must interact in the following ways with

    16 its clients:</p>

    17 <ul>

    18 <li id="GUID-C140D0C8-0486-5AEF-8AFC-732B34078705"><p>prior to initiating

    19 a request, a request function must set the value of the passed <codeph>TRequestStatus</codeph> to <codeph>KRequestPending</codeph>,

    20 which indicates that a request has been issued but not completed.</p> </li>

    21 <li id="GUID-117EE3F9-A2A9-59FE-ABE2-D8CC9C5856C5"><p>requests must be completed

    22 by signalling the requesting thread’s request semaphore by calling <codeph>RThread::RequestComplete()</codeph> with

    23 the <codeph>TRequestStatus</codeph> as the first parameter and the completion

    24 code as the second parameter (which is placed in the <codeph>TRequestStatus</codeph>).</p> </li>

    25 <li id="GUID-EBD83E91-B71C-5532-8EB6-F44541D2DC53"><p>there must be a <i>cancel

    26 function</i> which can cancel an outstanding request. In some cases, calling

    27 the cancel function does not cause cancellation because the request is already

    28 complete. In all cases, the request must be complete before the cancel function

    29 returns.</p> </li>

    30 <li id="GUID-6F7F7419-9170-50C3-AF76-8F03E4FF43D3"><p>if an asynchronous request

    31 is made, it must complete precisely once, whether normally, abnormally, or

    32 through cancellation.</p> </li>

    33 <li id="GUID-DCC53064-2B63-5532-B2E7-3A48FB9CD630"><p>completion through cancellation

    34 is often indicated by a <codeph>TRequestStatus</codeph> code of <codeph>KErrCancel</codeph>.</p> </li>

    35 </ul>

    36 <section id="GUID-08111F39-8412-40CC-B21D-C97A14B43BF8"><title>See also</title> <p><xref href="GUID-E0B34F3E-D4C4-3232-B8B1-7DB35B454646.dita"><apiname>TRequestStatus</apiname></xref> </p> </section>

    37 </conbody></concept>