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     7     Nokia Corporation - initial contribution.

     8 Contributors: 

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    10 <!DOCTYPE concept

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

    12 <concept id="GUID-0E93319A-439E-49D8-BF38-C809FEE4BB74" xml:lang="en"><title>User-side

    13 Creation</title><shortdesc>This document describes user-side creation of asynchronous requests.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>Asynchronous requests are commonly initiated by a call to <xref href="GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066.dita#GUID-6FBFA078-8253-3E24-B1F8-5F75E86C3066/GUID-FCC4A3A9-69F5-3947-8D0F-2AD12086F1E2"><apiname>RBusLogicalChannel::DoRequest()</apiname></xref>.

    15 The user making an asynchronous request creates a <xref href="GUID-E0B34F3E-D4C4-3232-B8B1-7DB35B454646.dita"><apiname>TRequestStatus</apiname></xref> object

    16 and passes it along with the request type to the <xref href="GUID-9D910016-5611-30DD-A139-EE46705A4912.dita"><apiname>DoRequest()</apiname></xref> call.

    17 The request status is changed to <xref href="GUID-B0778F54-C5DD-3307-A1E2-0DD339C4E4E7.dita"><apiname>KRequestPending</apiname></xref> by the

    18 Kernel before sending the message to the driver. The user may then either

    19 wait on the request using <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita#GUID-C197C9A7-EA05-3F24-9854-542E984C612D/GUID-50223158-D05D-33FE-A3DD-FFA9E2F464FF"><apiname>User::WaitForRequest()</apiname></xref>, or it

    20 may queue one or more requests and then wait. It may have an active object

    21 handler to receive the request complete notifications. </p>

    22 <codeblock id="GUID-39AC44C2-1FDF-5A6C-81F0-0BA9BB23DF91" xml:space="preserve">// Request status object for transmit. This object will be used to 

    23 // read the status of asynchronous requests after the notification of 

    24 // request completion

    25 //

    26  TRequestStatus txStatus;

    27      

    28 // Call the LDD interface TransmitData() API with test data descriptor 

    29 // and TRequestStatus object as parameters. Here TransmitData() is a

    30 // wrapper over a DoRequest() call.

    31 //

    32 r = ldd.TransmitData(txStatus, KTestSendData);

    33 test(r==KErrNone);

    34             

    35 // Wait till the request is complete on txStatus. The user thread is 

    36 // blocked with this call, till it is notified about the request 

    37 // completion.

    38 //

    39 User::WaitForRequest(txStatus);

    40      

    41 // txStatus holds the request completion. TRequestStatus::Int() 

    42 // returns the completion code. It will be KErrNone in case of 

    43 // successful completion.

    44 //

    45 r = txStatus.Int();

    46 test(r==KErrNone);</codeblock>

    47 </conbody></concept>