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<!DOCTYPE task

  PUBLIC "-//OASIS//DTD DITA Task//EN" "task.dtd">

<task id="GUID-50E6EEB5-45D2-5B95-BDEA-5615F586DA9C" xml:lang="en"><title>Using

Extended Interfaces</title><shortdesc>Framework developers define and publish extension interfaces to

the existing interfaces used in the framework. Once an interface extension

is published by the framework developer, plug-in developers implement the

extension if required. </shortdesc><prolog><metadata><keywords/></metadata></prolog><taskbody>

<steps id="GUID-D3DD03B6-79C0-5C7A-B263-A4AC2E50266E">

<step id="GUID-BA6F73F2-BA5C-5A2B-A405-D2FD99C06954"><cmd/>

<info>Identify the published instantiation and extended interface UIDs and

header files of the framework. </info>

</step>

<step id="GUID-27966E9C-33EF-5BC3-9E5E-FA3C68A60AFD"><cmd/>

<info>Create a <xref href="GUID-641A276D-F618-50CE-BA5A-658DCC26BAB5.dita">new

project file</xref> (<filepath>.mmp</filepath>) with <codeph>targettype</codeph> variable

set as PLUGIN3. Allocate UIDs for the the plug-in implementations and plug-in

DLL (UID3) as shown in the code snippet below. </info>

<stepxmp><codeblock id="GUID-080E8FC5-5114-5CBE-BF83-C7E4164CC0CC" xml:space="preserve">TARGET         cimplementationclass.dll

TARGETTYPE     PLUGIN3

CAPABILITY    All -TCB

// PLUGIN3 recognition UID followed by the UID for this dll

UID 0x10009D93 0x10009E37

VENDORID 0x70000001

SOURCEPATH    ../src

SOURCE        cimplementationclass.cpp 

USERINCLUDE    ../src

SYSTEMINCLUDE     /epoc32/include

START RESOURCE    cimplementationclass.rss

TARGET cimplementationclass.rsc

END

LIBRARY     euser.lib

LIBRARY     ecom.lib

</codeblock> </stepxmp>

</step>

<step id="GUID-E9B72208-C9EB-50C3-A5FE-849D34371314"><cmd/>

<info>Create a new resource file (<filepath>.rss</filepath>) of <xref href="GUID-9A9103E4-27B0-5CF3-855A-DCD44795A5C0.dita">format

version 3</xref>. </info>

<stepxmp><codeblock id="GUID-33EB82EB-1CD7-5213-9B74-3F760290795E" xml:space="preserve">CImplementationClass.rss

#include <ecom/registryinfov3.rh>

RESOURCE REGISTRY_INFO theInfo

    {

    resource_format_version = RESOURCE_FORMAT_VERSION_3;

    dll_uid = 0x10009E37;

    interfaces = 

    {

    INTERFACE_INFO

        {

        instantiation_interface_uid = 0x10009DBB;

        implementations = 

        {

        IMPLEMENTATION_INFO

            {

            info_format = IMPLEMENTATION_INFO_RECORD_TYPE1; 

            implementation_uid = 0x10009E38;

            version_no = 1;

            display_name = "Extended Interface Example";

            default_data = {"Extended Interface Example||up to 255 chars", "Max. two strings allowed"};

            opaque_data = {"up to 255 chars", “max. 2 strings allowed”};

            extended_interfaces = {0x10009E44, 0x10009E45};

            flags = FLAG_ROM_ONLY;                    

            }    

        };

        }

    };

    }

</codeblock> </stepxmp>

</step>

<step id="GUID-5D92F8AC-6440-5426-A79A-8D5CBE6D2E60"><cmd/>

<info>Implement the interfaces in the plug-in implementation source files. </info>

<info>Implementing an interface extension in a plug-in implementation can

be done in either of the two ways: </info>

<substeps id="GUID-3FCA938B-5515-5707-B583-08A398B138C3">

<substep id="GUID-34A3E29D-0195-5B41-AAA9-F8A9EDF6BCA0"><cmd/>

<info> Inheritance: The instantiation interface object is also of the type

of the extended interface object. When a user wants to instantiate the extended

interface object, the implementation simply returns a re-cast of the instantiation

interface object. </info>

<info>The example below shows implementing an interface extension using inheritance. </info>

<stepxmp><codeblock id="GUID-CE4895D9-14DB-55A5-8D61-36C4613DF453" xml:space="preserve">//Implementing an interface extension using multiple inheritance

class CImplementationClass : public CExampleInterface, public MExampleInterfaceExtended

{

public:

    static CImplementationClass* NewL();

    static TAny* GetExtendedInterfaceL(TAny* aInstantiationInterface,const TUid& aExtendedInterfaceUid,TUint32& aBitFlags,TAny*& aReleaseObject);

    static void ReleaseExtendedInterface(TAny* aExtendedInterface, const TUid& aExtendedInterfaceUid);

    ~ CImplementationClass() {}

    virtual void DoMethodL(); // from original interface

    virtual void DoMethodExtended();  //from MExampleInterfaceExtended

private:

    CImplementationClass() {}

};

</codeblock> </stepxmp>

</substep>

<substep id="GUID-C9A0347A-1EC9-5D30-A6DF-57E0C121387E"><cmd/>

<info>  Realizing the extended interface as separate class and objects. When

users fetch the extended interface object, the implementation allocates a

new object. </info>

<info>The example below shows implementing an interface extension using realisation. </info>

<stepxmp><codeblock id="GUID-99C45102-442C-56F5-8054-3C88C64FE1DE" xml:space="preserve">// Implementing an interface extension using realization

class CImplementationClassExtended : public CBase, public MExampleInterfaceExtended2

{

public:

    static CImplementationClassExtended* NewL();

    ~ CImplementationClassExtended() {}

    virtual void DoMethodExtended2();  //from MExampleInterfaceExtended2

private:

    CImplementationClassExtended() {}

};

</codeblock> </stepxmp>

</substep>

</substeps>

</step>

<step id="GUID-2E92FD5E-03E0-5587-B6D1-0CA7EEDBFA44"><cmd/>

<info>Implement <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-C7F147AC-6D77-3169-AAB4-B27262B4333B"><apiname>REComSession::CreateImplementationL()</apiname></xref>,<xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-760E4CCE-8E33-3B72-B143-380503F6ACC5"><apiname>REComSession::GetExtendedInterfaceL()</apiname></xref>,<xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-8F83D14E-F340-32B4-969C-5DC9E6EA1DB0"><apiname>REComSession::ManuallyReleaseExtendedInterfaceL()</apiname></xref> functions of the instantiation interface. </info>

<stepxmp><codeblock id="GUID-FC783C9A-1990-5DDB-9266-6469B9558EE0" xml:space="preserve">TAny* CImplementationClass::GetExtendedInterfaceL(TAny* aInstantiationInterface,

const TUid& aExtendedInterfaceUid,

TUint32& aBitFlags,

TAny*& aReleaseObject)

    {

    TAny* ret = NULL;

    aBitFlags &= ~KReleaseRequiredMask; // clear release flag

    switch (aExtendedInterfaceUid.iUid)

    {

    case 0x10009E44: 

        {

            // release not required, so do not modify aBitFlags.

         // re-cast Instantiation object as Extended Interface object

        ret = static_cast<MExampleInterfaceExtended *> (static_cast<CImplementationClass *>(aObject));

        break;

        }    

    case 0x10009E45: 

        {

          CImplementationClassExtended *classExt = CImplementationClassExtended::NewL();

        aReleaseObject = classExt;

        aBitFlags |= KReleaseRequiredMask; // Indicate release is required

        // Multiple inheritance involved – Cbase and the M class. Must use

            // either dynamic_cast or static_cast to add offset to the base pointer       

        ret = static_cast<MExampleInterfaceExtended2*>(classExt);

        break;

           }                

    }

    return ret;

    }

</codeblock> </stepxmp>

<info>The plug-in framework releases the extended interface object when the

user destroys the instantiation interface object. Alternatively, if the framework

wants to release the extended interface earlier, they can call the <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-8F83D14E-F340-32B4-969C-5DC9E6EA1DB0"><apiname>REComSession::ManuallyReleaseExtendedInterfaceL()</apiname></xref>  </info>

<stepxmp><codeblock id="GUID-A058A010-9875-52F6-ABF2-8B329F50B750" xml:space="preserve">void CImplementationClass::ReleaseExtendedInterface(TAny* aExtendedInterface, const TUid&amp; aExtendedInterfaceUid)

    {

    switch (aExtendedInterfaceUid.iUid)

    {

    case 0x10009E45:

        {

            // this Extended Interface object require release.

        CImplementationClassExtended* classExt = static_cast<CImplementationClassExtended*>(aReleaseObject);

        delete classExt;

        break;

        }                

    }

    }    

</codeblock> </stepxmp>

<info>The aInstanceKey parameter is returned by <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-C7F147AC-6D77-3169-AAB4-B27262B4333B"><apiname>REComSession::CreateImplementationL()</apiname></xref>.

It identifies the instantiation interface object instance. The aExtendedInterfaceUid

parameter identifies the extended interface required. </info>

</step>

<step id="GUID-6E73075E-E907-5984-9571-D7A77FC2D05A"><cmd/>

<info>Export the instantiation functions into a TImplementationProxy3 table. </info>

<stepxmp><codeblock id="GUID-7CFF8E49-3B6F-5DAB-883F-1347B907F77E" xml:space="preserve">const TImplementationProxy3 KImplementationTable[] =

    {

    IMPLEMENTATION_PROXY_ENTRY3(0x10009E38, CImplementationClass::NewL, CImplementationClass::GetExtendedInterfaceL,CImplementationClass::ReleaseExtenedInterface)

    };

EXPORT_C const TImplementationProxy3* ImplementationGroupProxy(TInt& aTableCount)

    {

    aTableCount = sizeof(KImplementationTable) / sizeof(TImplementationProxy3);

    return KImplementationTable;

    }

</codeblock> </stepxmp>

</step>

<step id="GUID-5790D794-A201-5E9F-AE2E-DC698878CCF5"><cmd/>

<info>Export the release functions into a TImplementationProxy3 table. </info>

<stepxmp><codeblock id="GUID-22DB44AF-EDE6-52C0-ADBE-216F95E3FB5C" xml:space="preserve">void CImplementationClass::ReleaseExtendedInterface(TAny* aExtendedInterface, const TUid&amp; aExtendedInterfaceUid)

    {

    switch (aExtendedInterfaceUid.iUid)

    {

    case 0x10009E45:

        {

            // this Extended Interface object require release.

        CImplementationClassExtended* classExt = static_cast<CImplementationClassExtended*>(aReleaseObject);

        delete classExt;

        break;

        }                

    }

    }    

</codeblock> </stepxmp>

</step>

</steps>

<postreq><p>To instantiate and use an extended interface, the plug-in user

must: </p> <ul>

<li id="GUID-A8A28B3D-D94E-5AC9-8C3F-275A4C8F89DE"><p>Identify plug-ins that

support the desired interface extensions using <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-AE9D4F24-8554-3151-AAF3-D63F400821C4"><apiname>REComSession::ListImplementationsL()</apiname></xref>. </p> <codeblock id="GUID-987C54C2-F1AF-57C6-95DA-37F1572AD1B4" xml:space="preserve">IMPORT_C static void ListImplementationsL(TUid aInterfaceUid, 

RExtendedInterfacesArray& aExtendedInterfaces,

    const TEComResolverParams& aResolutionParameters,

    RImplInfoPtrArray& aImplInfoArray);

</codeblock> <p>The “aInterfaceUid” parameter specifies the instantiation

interface. All of the implementations returned in “aImplInfoArray” support

all the extensions listed in the “aExtendedInterfaces” parameter. </p> </li>

<li id="GUID-ED513B5A-9F51-5B5C-AB58-E961CAFEFD92"><p>Select one from the

array and create an instantiation interface object. </p> </li>

<li id="GUID-C4A2263B-08D1-5D44-99B2-840EE4849B35"><p>Call <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-760E4CCE-8E33-3B72-B143-380503F6ACC5"><apiname>REComSession::GetExtendedInterfaceL()</apiname></xref> API

to get an extended interface object. </p> <codeblock id="GUID-B9EE4751-EA4B-5BB6-A6DA-3083FE0CCE36" xml:space="preserve">IMPORT_C static TAny* GetExtenedInterfaceL(const TUid&amp; aInstanceKey, 

const TUid& aExtendedInterfaceUid);

</codeblock> <p>The aInstanceKey parameter identifies the instantiation interface

object returned by <xref href="GUID-1344F049-81C4-3D17-AF46-8B5584680ADB.dita#GUID-1344F049-81C4-3D17-AF46-8B5584680ADB/GUID-C7F147AC-6D77-3169-AAB4-B27262B4333B"><apiname>REComSession::CreateImplementationL()</apiname></xref>. </p> </li>

</ul> <p>The example code depicts the above steps: </p> <codeblock id="GUID-5D0D622D-3CA6-5CDB-B035-F68A580949AA" xml:space="preserve">

const TUid KExampleInterfaceUid = {0x10009DBB}; // the Instantiation Interface

const TUid KExtendedInterfaceUid1 = {0x10009E44};

const TUid KExtendedInterfaceUid2 = {0x10009E45};

// Set up extended interfaces UID list which form part of the resolution criteria.

RArray<TUid> extendedInterfaces;

CleanupClosePushL(extendedInterfaces);

extendedInterfaces.AppendL(KExtendedInterfaceUid1);

extendedInterfaces.AppendL(KExtendedInterfaceUid2);

// set up resolve parameter

_LIT8(KExampleImplementationData,"Extended Interface Example");

TEComResolverParams ResolverParams;

ResolverParams.SetDataType(KExampleImplementationData());

ResolverParams.SetGenericMatch(ETrue);

TUid instanceKey;

CExampleInterface* instantiateIf = static_cast<CExampleInterface*>(

    REComSession::CreateImplementationL(KExampleInterfaceUid,

                                       extendedInterfaces,

                                       instanceKey,

                                       ResolverParams) );

CleanupStack::PopAndDestroy(&extendedInterfaces);

CleanupStack::PushL(instantiateIf);

// May want to TRAP here if KErrNotSupported is handled, i.e. extension optional

MExampleInterfaceExtended2* ext2 = static_cast<MExampleInterfaceExtended2*>(

  REComSession::GetExtendedInterfaceL(instanceKey, KExtendedInterfaceUid2));

instantiateIf->DoMethodL();  // access old interface function

ext2->DoMethodExtended2();   // access extension function

// Calling ManuallyReleaseExtendedInterface is optional. Do this

// if want to release extended object early.

REComSession::ManuallyReleaseExtendedInterface(instanceKey,KExtendedInterfaceUid2);

REComSession::DestroyedImplementation(instanceKey);

CleanupStack::PopAndDestroy(instantiateIf);

</codeblock> </postreq>