--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/emailservices/emailframework/commonlib/inc/cemailextensionbase.h	Thu Dec 17 08:39:21 2009 +0200
@@ -0,0 +1,152 @@
+/*
+* Copyright (c) 2009 Nokia Corporation and/or its subsidiary(-ies). 
+* All rights reserved.
+* This component and the accompanying materials are made available
+* under the terms of "Eclipse Public License v1.0"
+* which accompanies this distribution, and is available
+* at the URL "http://www.eclipse.org/legal/epl-v10.html".
+*
+* Initial Contributors:
+* Nokia Corporation - initial contribution.
+*
+* Contributors:
+*
+* Description:  Meeting Request calendar info object extension
+*
+*/
+
+#ifndef CEMAILEXTENSIONBASE_H
+#define CEMAILEXTENSIONBASE_H
+
+#include <e32base.h>
+
+/**
+* Base class for extensions. Instances of subclasses are requested from
+* CExtendableEmail::ExtensionL() with specific extension UID.
+* When client has ended using an extension it must be released with
+* CExtendableEmail::ReleaseExtension().
+* @since s60 v5.0
+*/
+class CEmailExtension : public CBase
+{
+
+public: 
+    IMPORT_C ~CEmailExtension();
+protected:    
+    IMPORT_C CEmailExtension( const TUid& aUid );
+public:
+    
+    /**         
+    * returns extension uid
+    * @return   uid of the extension.
+    */
+    IMPORT_C TUid Uid() const;
+
+public: // for internal use
+                           
+    /**
+    * Decrement reference count.
+    * @return new value of ref count
+    */                           
+    TUint DecRef();
+    
+    /**
+    * Increment reference count.
+    */                           
+    void IncRef();
+        
+private:
+
+    
+    // extension interface UID defined by specific interface.
+    const TUid iUid;    
+    
+    // Reference count is needed because more than one client may request
+    // same extension (e.g. UI and protocol plugin).
+    TUint iRefCount;
+};
+
+/**
+* helper class for managing extensions. In most cases needed only
+* by CExtendableEmail when extensions are created/released. Proto
+* @since s60 v5.0
+*/
+class TEmailExtensions
+{
+public:
+
+    /**
+     * c++ constructor
+     */
+    IMPORT_C TEmailExtensions();
+    
+    /**
+     * Destructor
+     */
+    IMPORT_C ~TEmailExtensions();
+                       
+    /**
+     * Returns extension index in iExtensions
+     @ return extension index or KErrNotFound
+     */
+    IMPORT_C TInt FindExtension( const TUid& aUid ) const;
+    
+    /**
+     * Returns extension by index or panics if invalid index is given
+     * @param aIndex index in iExtensions
+     * @panic EEmailExtensionIndexOutOfRange if index is out of range
+     * @return extension
+     */
+    IMPORT_C CEmailExtension* Extension( const TInt aIndex ) const;
+    
+    /**
+     * Adds extension to iExtensions array and increments its ref count by one.
+     *
+     * @param aExtenstion   extension to add
+     * @leave KErrArgument  if aExtension is NULL
+     */
+    IMPORT_C void AddL( CEmailExtension* aExtension );
+
+    /**
+     * Removes extension from iExtensions
+     * @param aExtenstion extension to remove
+     */
+    IMPORT_C void Remove( const CEmailExtension* aExtension );
+    
+private:    
+    // array of extensions
+    RPointerArray<CEmailExtension> iExtensions;
+};
+
+/**                 
+* Classes that support email extension mechanism by returning extensions by
+* uid should have this as base class.
+*
+* @since s60 v5.0
+*/                 
+class CExtendableEmail : public CBase
+{
+public:
+    /**
+    * Decrements extension reference count and deletes if count reaches 0.
+    * Derived class must call this if it overrides this method.
+    * @param aExtension extension to release
+    */
+    IMPORT_C virtual void ReleaseExtension( CEmailExtension* aExtension );
+
+    /**
+    * Requests extension. Default implementation performs lookup only and
+    * derived class should implement actual instantiation because it knows
+    * extensions it supports. Derived class must always call this to ensure
+    * that extension is not created twice.
+    *
+    * @param aExtension extension to release
+    */
+    IMPORT_C virtual CEmailExtension* ExtensionL( const TUid& aInterfaceUid );
+
+protected:    
+    // extension containment
+    TEmailExtensions iExtensions;
+};
+
+#endif // CEMAILEXTENSIONBASE_H