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<concept id="GUID-AA5DEEB2-0B13-5FA8-8494-EC2F5C654FEF" xml:lang="en"><title>CentRepExample:

Using central repository for persistent storage</title><prolog><metadata><keywords/></metadata></prolog><conbody>

<p>This example application demonstrates the usage of Central Repository API

for persistent storage. </p>

<section id="GUID-E2129D18-6FBB-55B9-8D79-420EB2CF2401"><title>Description</title> <p>Several

Symbian OS 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><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 <xref href="GUID-3100800B-B2F7-50EF-BD4C-3C345ECCB2A5.dita">Symbian OS build process</xref> 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>