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    10 <!DOCTYPE concept

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

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

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

    15 for persistent storage. </p>

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

    17 Symbian OS components have state and settings information that need to be

    18 persistent. There is also a global state that needs to persist, for example,

    19 default filenames, locale settings, user preferences. </p> <p>The CentRep

    20 example application first registers a group of settings with the central repository

    21 server. It uses <filepath>E80000AD.txt</filepath>, a UTF-16 format text file

    22 to initialise the repository. This text file contains access control structure

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

    24 initialisation text file into a binary file using the central repository converter

    25 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

    26 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

    27 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

    28 with the contents in the initialisation file. </p> <p>Each setting stored

    29 in the repository will have a unique key to identify the setting. This unique

    30 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

    31 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

    32 and deletes them from their original location. </p> <p>The application also

    33 creates another <codeph>CRepository</codeph> object to demonstrate that, at

    34 any given point a repository cannot be opened with <i>READ/WRITE</i> access

    35 by more than one client. In such situations, it is recommended to start a

    36 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.

    37 A transaction guarantees the consistency and persistence of all values read

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

    39 the central repository server to notify any changes to the original settings. </p><p><b>Related

    40 APIs</b></p><ul>

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

    42 <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>

    43 <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>

    44 <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>

    45 <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>

    46 <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>

    47 <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>

    48 </ul> </section>

    49 <section><title>Download</title> <p>Click on the following link to download

    50 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>

    51 <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

    52 how to build an application. </p> <p>The <codeph>CentRepExample</codeph> builds

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

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

    55 After launching the executable, depending on the emulator you are using, you

    56 may need to task away from the app launcher/shell screen to view the console. </p> </section>

    57 </conbody></concept>