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Adaptation/GUID-0A6C8DB8-ED41-4243-BA96-CA691CF9CD19.dita
author Graeme Price <GRAEME.PRICE@NOKIA.COM>
Fri, 15 Oct 2010 14:32:18 +0100
changeset 15 307f4279f433
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<?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-0A6C8DB8-ED41-4243-BA96-CA691CF9CD19" xml:lang="en"><title>Data
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Buffers</title><shortdesc>This document describes how device drivers allocate and access
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memory buffers.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
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<section id="GUID-21C5B685-F546-45B5-A829-00B2DBCBF8E4">
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      <p>Most device drivers need to use memory buffers for I/O operations.
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Drivers typically own memory buffers, allocate them, and access them through
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pointers. The thread should be in a critical section when it allocates or
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de-allocates memory. </p> <codeblock id="GUID-B222000C-8344-5239-9546-4E831A3C0A6E" xml:space="preserve">// Tx and Rx Buffers
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TUInt8* iTxBuffer;
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TUInt8* iRxBuffer;</codeblock> <codeblock id="GUID-A921D206-7243-5F0A-ADA3-0330D93A137F" xml:space="preserve">// Logical Channel second stage constructor
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TInt DExDriverLogicalChannel::DoCreate(TInt /*aUnit*/, const TDesC8*
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/*anInfo*/, const TVersion&amp; aVer)
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    {
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    ...
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    // Initialize the Tx Buffer
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    iTxBuffer = (TUInt8*) Kern::Alloc(KTxBufferSize);
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    if (!iTxBuffer)
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        return KErrNoMemory;
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    ...
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    }</codeblock> <p>Memory buffers must be freed when they are not required.
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If this is not done, a memory leak occurs. </p> <codeblock id="GUID-688A360C-1B7A-5F3A-BB83-98EB8A4658F3" xml:space="preserve">// Free Tx Buffer
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Kern::Free(iTxBuffer)</codeblock>     </section>
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</conbody></concept>
FCL/sftools/depl/docscontent