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<concept id="GUID-AA5DEEB2-0B13-5FA8-8494-EC2F5C654FEF" xml:lang="en"><title>CentRepExample: Using Central Repository for Persistent Storage</title><shortdesc>This example application demonstrates the usage of Central

Repository API for persistent storage.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-E2129D18-6FBB-55B9-8D79-420EB2CF2401"><title>Description</title> <p>Several Symbian platform components have state and settings information

that need to be persistent. There is also a global state that needs

to persist, for example, default filenames, locale settings, user

preferences. </p> <p>The CentRep example application first registers

a group of settings with the central repository server. It uses <filepath>E80000AD.txt</filepath>, a UTF-16 format text file to initialise

the repository. This text file contains access control structure and

the initial content of the repository. It is recommended to convert

the initialisation text file into a binary file using the central

repository converter tool to speed up the execution. </p> <p>The application

creates a <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita"><apiname>CRepository</apiname></xref> object using the <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-B8DD1F6F-5A03-30C7-A5B5-51053D9FBDD3"><apiname>CRepository::NewLC()</apiname></xref> method to access a repository using

its UID. It resets the whole repository using <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-BA806B9D-C347-3722-886E-1290A4A0618A"><apiname>CRepository::Reset()</apiname></xref> method with the contents in the initialisation file. </p> <p>Each

setting stored in the repository will have a unique key to identify

the setting. This unique key is used to read and change the setting

by calling the <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-AB3918A5-BA69-3EE8-89B4-51DD8A899AF5"><apiname>CRepository::Get()</apiname></xref> and <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-114079A1-A8CA-3FE7-8FAD-F5E61453FF6B"><apiname>CRepository::Set()</apiname></xref> methods respectively. The application

moves these keys to a different location using <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-4F005B5F-2664-3F7C-848D-B6F93462F2F4"><apiname>CRepository::Move()</apiname></xref> method and deletes them from their original location. </p> <p>The

application also creates another <codeph>CRepository</codeph> object

to demonstrate that, at any given point a repository cannot be opened

with <i>READ/WRITE</i> access by more than one client. In such situations,

it is recommended to start a transaction before a write operation

using <xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-1F14EB0C-89CF-3A76-A678-5F6F86F50B32"><apiname>CRepository::StartTransaction()</apiname></xref> method. A

transaction guarantees the consistency and persistence of all values

read and written during the transaction. </p> <p>Finally, the application

requests the central repository server to notify any changes to the

original settings. </p><p><b>Related APIs</b></p><ul>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita"><apiname>CRepository</apiname></xref> - Provides access to a repository.</p></li>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-AB3918A5-BA69-3EE8-89B4-51DD8A899AF5"><apiname>CRepository::Get()</apiname></xref></p></li>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-4F005B5F-2664-3F7C-848D-B6F93462F2F4"><apiname>CRepository::Move()</apiname></xref></p></li>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-B8DD1F6F-5A03-30C7-A5B5-51053D9FBDD3"><apiname>CRepository::NewLC()</apiname></xref></p></li>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-BA806B9D-C347-3722-886E-1290A4A0618A"><apiname>CRepository::Reset()</apiname></xref></p></li>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-114079A1-A8CA-3FE7-8FAD-F5E61453FF6B"><apiname>CRepository::Set()</apiname></xref></p></li>

<li><p><xref href="GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78.dita#GUID-DEA618DF-D462-3B3E-A1E1-F21295AAFE78/GUID-1F14EB0C-89CF-3A76-A678-5F6F86F50B32"><apiname>CRepository::StartTransaction()</apiname></xref></p></li>

</ul> </section>

<section id="GUID-3B353EAA-5FE4-426B-A0A5-6800CE0BC9E3"><title>Download</title> <p>Click on the following link to download the example: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/zips/guid-e78b3d2c-7205-45ca-abe0-163e33a0fcc3.zip" scope="external">CentRepExample.zip</xref></p><p>Click: <xref href="guid-6013a680-57f9-415b-8851-c4fa63356636/guid-e78b3d2c-7205-45ca-abe0-163e33a0fcc3.html" scope="peer">browse</xref> to view the example code.</p> </section>

<section id="GUID-DCCBE8DE-0BBD-5528-A460-E1645116DD4F"><title>Build</title> <p>The Symbian build process describes how to build an application. </p> <p>The <codeph>CentRepExample</codeph> builds an

executable called <filepath>CentRepExample.exe</filepath> in the standard

location (\epoc32\release\winscw\&lt;<i>build_variant</i> &gt; for CodeWarrior).

After launching the executable, depending on the emulator you are

using, you may need to task away from the app launcher/shell screen

to view the console. </p> </section>