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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>
</conbody></concept>