--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Symbian3/SDK/Source/GUID-49C93C36-D86B-4EEE-A8AB-4279312DF4BC.dita	Wed Mar 31 11:11:55 2010 +0100
@@ -0,0 +1,60 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright (c) 2007-2010 Nokia Corporation and/or its subsidiary(-ies) All rights reserved. -->
+<!-- This component and the accompanying materials are made available under the terms of the License 
+"Eclipse Public License v1.0" which accompanies this distribution, 
+and is available at the URL "http://www.eclipse.org/legal/epl-v10.html". -->
+<!-- Initial Contributors:
+    Nokia Corporation - initial contribution.
+Contributors: 
+-->
+<!DOCTYPE task
+  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">
+<task id="GUID-49C93C36-D86B-4EEE-A8AB-4279312DF4BC" xml:lang="en"><title>Write
+an interface implementation for a converter</title><prolog><metadata><keywords/></metadata></prolog><taskbody>
+<context>       <p>Conversion from one data type to another is performed by
+a class derived from the abstract <codeph>CConverterBase2</codeph> class.
+Conversions can be performed between files specified by filenames, or between
+objects which support the stream interfaces. For example, stream stores, memory
+streams and the clipboard.</p><p>Implement the following key <codeph>CConverterBase2</codeph> functions:</p><ul>
+<li><p><codeph>ConvertAL()</codeph>, which prepares the converter to convert
+data in a file. By default, this leaves with <codeph>KErrNotSupported</codeph>.</p></li>
+<li><p><codeph>ConvertObjectAL()</codeph>, which prepares the converter to
+convert data in a stream. By default, this leaves with <codeph>KErrNotSupported</codeph>.</p></li>
+<li><p><codeph>DoConvertL()</codeph>, which performs a step in the conversion
+and indicates whether the conversion is complete, or whether the client needs
+to call <codeph>DoConvertL()</codeph> again. By default this leaves with <codeph>KErrNotSupported</codeph>.</p></li>
+<li><p><codeph>CancelConvert()</codeph>, which can be called at any stage
+in the conversion process to cancel the conversion.</p></li>
+</ul><p><b>NOTE</b>: The approach of an initial preparatory step followed
+by a sequence of further incremental steps allows the client thread to stay
+responsive while a potentially lengthy conversion process is taking place.</p><p><codeph>CConverterBase2</codeph> also
+defines two functions which do the complete conversion in one function call: <codeph>ConvertL()</codeph> and <codeph>ConvertObjectL()</codeph>. <codeph>CConverterBase2</codeph> supplies default implementations of these functions
+which perform their tasks by calling <codeph>ConvertAL()</codeph> or <codeph>ConvertObjectAL()</codeph> once,
+and <codeph>DoConvertL()</codeph> in a loop until complete. </p><p>A converter
+must also implement:</p><ul>
+<li><p><codeph>Uid()</codeph> to return a UID that uniquely identifies the
+converter. This should be the same value as the <codeph>conv_uid</codeph> value
+defined in the converter's <codeph>CONARC_RESOURCE_FILE</codeph> resource.</p></li>
+<li><p><codeph>Capabilities()</codeph> to return a flag indicating if the
+converter can convert files, streams, or both.</p></li>
+</ul><p>The following code snippet is an example declaration of a converter
+class:</p><codeblock xml:space="preserve">class CExampleConverter : public CConverterBase2
+    {
+    public: 
+        static CConverterBase2* NewL();        CExampleConverter();
+        ~CExampleConverter();    
+        // from CConverterBase2
+        void ConvertObjectAL( RReadStream&amp; aReadStream, 
+                              RWriteStream&amp; aWriteStream, 
+                              MConverterUiObserver* aObserver = NULL );
+        TBool DoConvertL();
+        TUid Uid();
+        TInt Capabilities();
+        void CancelConvert();
+    private:
+        RReadStream* iReadStream;
+        RWriteStream* iWriteStream;
+    };
+</codeblock><p><b>Note</b>: The <codeph>MConverterUiObserver</codeph> observer
+pointer can be NULL, so check for this before calling its functions.</p></context>
+</taskbody></task>
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