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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 &lt;ecom/registryinfov3.rh&gt;

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&amp; aExtendedInterfaceUid,TUint32&amp; aBitFlags,TAny*&amp; aReleaseObject);
    static void ReleaseExtendedInterface(TAny* aExtendedInterface, const TUid&amp; 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&amp; aExtendedInterfaceUid,
TUint32&amp; aBitFlags,
TAny*&amp; aReleaseObject)
    {
    TAny* ret = NULL;
    aBitFlags &amp;= ~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&lt;MExampleInterfaceExtended *&gt; (static_cast&lt;CImplementationClass *&gt;(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&lt;MExampleInterfaceExtended2*&gt;(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&lt;CImplementationClassExtended*&gt;(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&amp; 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&lt;CImplementationClassExtended*&gt;(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&amp; aExtendedInterfaces,
    const TEComResolverParams&amp; aResolutionParameters,
    RImplInfoPtrArray&amp; 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&amp; 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&lt;TUid&gt; 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&lt;CExampleInterface*&gt;(
    REComSession::CreateImplementationL(KExampleInterfaceUid,
                                       extendedInterfaces,
                                       instanceKey,
                                       ResolverParams) );
CleanupStack::PopAndDestroy(&amp;extendedInterfaces);

CleanupStack::PushL(instantiateIf);
// May want to TRAP here if KErrNotSupported is handled, i.e. extension optional
MExampleInterfaceExtended2* ext2 = static_cast&lt;MExampleInterfaceExtended2*&gt;(
  REComSession::GetExtendedInterfaceL(instanceKey, KExtendedInterfaceUid2));

instantiateIf-&gt;DoMethodL();  // access old interface function
ext2-&gt;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>
</taskbody></task>