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<concept id="GUID-F0BDE1EC-5042-5328-9290-22BB2189F6B4" xml:lang="en"><title>How

to Implement a LBS Set Clock Plug-in DLL</title><shortdesc>This topic describes how to implement a LBS set clock plug-in class. </shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section><title>Required background</title> <p><xref href="GUID-A5510456-A5EB-59EC-B146-74D58A118875.dita">LBS

system clock adjustment overview</xref> describes the set clock plug-in interface. </p> </section>

<section><title>Introduction </title> <p>LBS contains a default implementation

of a set clock module that sets the system clock time by calling <xref href="GUID-C197C9A7-EA05-3F24-9854-542E984C612D.dita#GUID-C197C9A7-EA05-3F24-9854-542E984C612D/GUID-145F52E6-2A29-3FF1-8AD1-7009BE0074D7"><apiname>User::SetUTCTime()</apiname></xref>. </p> <p>To

set the system clock by some other method, a licensee must create a set clock

plug-in DLL and configure LBS to use it. </p> </section>

<section><title>Implementing the plug-in class</title> <p>Licensee set clock

plug-in classes must derive from the abstract base class <codeph>CGPSSetClockBase</codeph> shown

in figure 1. </p> <p> <codeph>CGPSSetClockBase</codeph> is packaged in <filepath>GPSSetClock.dll</filepath>.

An implementation includes <filepath>GPSSetClockBase.h</filepath> and links

with <filepath>GPSSetClock.lib</filepath>. </p> <fig id="GUID-CAE2F49D-6B7A-5F6F-A0BD-25A8475CDE32">

<title>              Figure 1. CGPSSetClockBase is the base class for LBS

set clock              plug-in classes.            </title>

<image href="GUID-9BA295BC-627C-5B82-B669-F4F7B55E3F82_d0e437287_href.png" placement="inline"/>

</fig> <p>To implement a set clock plug-in a developer must follow the steps

in the next section. </p> </section>

<section><title>Procedure</title> <ol id="GUID-657B1DA8-2A2B-583B-AADD-3E94AEE04751">

<li id="GUID-D2515C64-C814-53BB-B161-DB571F4FE42B"><p>Create a class derived

from <codeph>CGPSSetClockBase</codeph>: </p> <codeblock id="GUID-E4FE605C-689D-5A68-9FA4-E394DB366C5B" xml:space="preserve">#include &lt;GPSSetClockBase.h&gt;

class CGPSSetClockImpl : public CGPSSetClockBase

{

    public:

  static CGPSSetClockImpl* NewL();

  virtual TInt SetUTCTime(const TTime& aTime);

  virtual ~CGPSSetClockImpl();

 private:

  CGPSSetClockImpl();

  void ConstructL();

};

</codeblock> <p> <i>Note that the implementation class must only allocate

memory on construction</i>, not when <xref href="GUID-E5ED4ACA-5EC4-3AE2-862A-AC204DCA83B5.dita#GUID-E5ED4ACA-5EC4-3AE2-862A-AC204DCA83B5/GUID-F6922F15-F4D3-31D9-86AD-B2809AA111A1"><apiname>CGPSSetClockBase::SetUTCTime()</apiname></xref> is

called. This is because LBS must always be able to respond to emergency services

location requests and so must never run out of memory at runtime. Memory for

the set clock plug-in DLL must therefore be allocated on startup of the LBS

subsystem when the ECom framework loads the plug-in DLL and calls the <codeph>NewL()</codeph> function

on the implementation class. </p> <codeblock id="GUID-4A865931-1C48-5396-BD5B-BF590CE031E9" xml:space="preserve">CGPSSetClockImpl* CGPSSetClockImpl::NewL()

{

    // Allocate all required memory here or in ConstructL()

 ...

}

</codeblock> </li>

<li id="GUID-AF16291B-786D-5E90-917C-ABE8F38D664D"><p>Implement the virtual

method <xref href="GUID-E5ED4ACA-5EC4-3AE2-862A-AC204DCA83B5.dita#GUID-E5ED4ACA-5EC4-3AE2-862A-AC204DCA83B5/GUID-F6922F15-F4D3-31D9-86AD-B2809AA111A1"><apiname>CGPSSetClockBase::SetUTCTime()</apiname></xref>. The implementation

of this method is licensee specific and depends on the method that the licensee

uses to set the system clock. </p> <codeblock id="GUID-F5B3CC27-D8C1-5302-8AFE-CF92A2FEFD82" xml:space="preserve">

TInt CGPSSetClockImpl::SetUTCTime(const TTime& aTime)

{

    // Licensee method of setting the system clock

 // Do not allocate any additional memory!

    ...

}

</codeblock> </li>

<li id="GUID-25E5345F-9B40-55B2-9FE4-4EBF5549DB59"><p>Package the class as

an ECom plug-in DLL. </p> <p>See <xref href="GUID-7B304B12-D597-550C-9EAA-AB8B2A6A8531.dita">How

to create implementation collections</xref> for information on how to package

an implementation class as an ECom plug-in DLL. </p> <p> <b>Note:</b> LBS

must be configured to use the licensee set clock plug-in DLL to set the system

clock. <xref href="GUID-23BBC1D8-B3A0-5148-A4F1-22ECF3043E4E.dita">LBS administration</xref> describes

how to configure LBS system clock synchronisation settings using either the

LBS Administration API or a repository initialisation file. </p> </li>

</ol> </section>

</conbody><related-links>

<link href="GUID-A5510456-A5EB-59EC-B146-74D58A118875.dita"><linktext>LBS System

Clock Synchronisation Overview</linktext></link>

</related-links></concept>