--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Symbian3/SDK/Source/GUID-442F2E69-87B5-54E7-B62A-70B742432372.dita	Wed Mar 31 11:11:55 2010 +0100
@@ -0,0 +1,82 @@
+<?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 concept
+  PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
+<concept id="GUID-442F2E69-87B5-54E7-B62A-70B742432372" xml:lang="en"><title>How
+to Commit and Revert </title><shortdesc>Changes to a store are not made permanent until they are committed
+and until such changes are committed, they can be rolled back (i.e. reverted)</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>
+<p>Transactions are supported by a commit and revert protocol.</p>
+<p>In the following code fragment, <codeph>store</codeph> is a pointer to
+an opened permanent file store. The function <codeph>doUpdateStoreL()</codeph> adds
+a number of streams to this store and, if successful, establishes a new commit
+point.</p>
+<p>If a failure occurs or the call to <codeph>CommitL()</codeph> fails, then <codeph>doUpdateStoreL()</codeph> leaves;
+the leave is trapped and any changes made to the store are rolled back, so
+that the store is in the same state as it was before the changes were started.
+The store, therefore, remains in a consistent state in the event of failure.</p>
+<p><codeph>CItemArray</codeph> is a class that encapsulates an array of <codeph>TItem</codeph> objects;
+the relevant part of the definition is:</p>
+<codeblock id="GUID-0B5B04A7-AB4A-55CA-BCF0-9E19623F1554" xml:space="preserve">typedef TBuf&lt;100&gt; TItem;</codeblock>
+<codeblock id="GUID-52A3FAC2-4E23-5574-A21C-DE087ADDB911" xml:space="preserve">class CItemArray : public CBase
+    {
+public:
+    ...
+    void AddItemL(const TItem&amp; anItem);
+    void StoreL() const;
+       void ExternalizeL(RWriteStream&amp; aStream) const;
+    ...
+private:
+    CStreamStore&amp; iStore;
+       ...
+    CArrayFixFlat&lt;TStreamId&gt;* iArray;
+    }</codeblock>
+<p>The example also assumes that the store is one that allows streams to be
+modified and replaced; for example, a permanent file store.</p>
+<codeblock id="GUID-21AFD117-3D52-55BE-BEB7-430CF08D0429" xml:space="preserve">...
+TRAPD(error,doUpdateStoreL(*store));
+if (error!=KErrNone)
+    {
+    store-&gt;Revert();
+    ...
+    }
+...</codeblock>
+<codeblock id="GUID-EB07D2AA-ECAA-5014-84F0-85767A60E366" xml:space="preserve">LOCAL_C void doUpdateStoreL(CPersistentStore&amp; aStore)
+    {
+    _LIT(KTxtHello,"hello");
+    _LIT(KtxtWorld," world!");
+              // get the root stream into memory
+    CItemArray* array=CItemArray::NewLC(aStore,aStore.Root());
+    
+              // Add some items
+    TItem item;
+    item = KTxtHello;
+    array-&gt;AddItemL(item);
+    item = KTxtWorld;
+    array-&gt;AddItemL(item);
+             // Re-write the root stream with new data
+    array-&gt;StoreL();
+            // commit all changes
+    aStore.CommitL();
+    ...
+    }</codeblock>
+<codeblock id="GUID-3E2184DA-7C74-58F0-925E-6AE1317732C9" xml:space="preserve">void CItemArray::AddItemL(const TItem&amp; anItem)
+    {
+    RStoreWriteStream outstream;
+    TStreamId id=outstream.CreateLC(iStore);
+    outstream&lt;&lt;anItem;
+    outstream.CommitL();
+    CleanupStack::PopAndDestroy();
+    iArray-&gt;AppendL(id);
+    }
+</codeblock>
+</conbody><related-links>
+<link href="GUID-C9D8D913-C65F-5A69-A606-30F59BFB38E2.dita"><linktext>File Stores</linktext>
+</link>
+</related-links></concept>
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