--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/videofeeds/utils/inc/mtvobserverutils.inl	Mon Jan 18 20:21:12 2010 +0200
@@ -0,0 +1,214 @@
+/*
+* Copyright (c) 2007 Nokia Corporation and/or its subsidiary(-ies).
+* All rights reserved.
+* This component and the accompanying materials are made available
+* under the terms of the License "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:    Helper functions and macros for handling multiple observers.*
+*/
+
+
+
+
+#ifndef _MTV_OBSERVER_UTILS
+#define _MTV_OBSERVER_UTILS
+
+namespace MtvObserverUtils
+{
+    
+/**
+ *  Struct for holding a bunch of observers and a semaphore for controlling observer removal.
+ *
+ *  @since Live TV UI v1.0
+ */
+template <class ObserverType, template<class> class ContainerType = RPointerArray, class PointerType = ObserverType>
+struct RObserverData
+    {
+    // constructor for initializing the semaphore
+    RObserverData() : iSemaphore(0), iShutdown(EFalse)
+        {
+        }
+    /**
+     * Initializes the container.
+     * This function is currently just a placeholder, later
+     * it can be used to add support for CBase-derived containers,
+     * assuming that all clients call OpenL and Close when using
+     * this class.
+     */
+    void OpenL()
+        {
+        }
+    /**
+     * Closes the container.
+     */
+    void Close()
+        {
+        iContainer.Close();
+        iShutdown = ETrue;
+        }
+    // Container can be RPointerArray, RArray.. 
+    // At the moment CBase-derived containers are not supported.
+    ContainerType<ObserverType> iContainer;
+    // the semaphore is used so that when it has a value greater than zero, observers
+    // are not removed, but nulled in the container
+    TInt iSemaphore;
+    // pointer type member helps code using this object, the using code does not
+    // need to know the actual observer type
+    PointerType* iObserver;
+    // Set to ETrue when the provider of notifications is shut down.
+    TBool iShutdown;
+    };
+
+/**
+ * Removes NULL observers from a container.
+ * @param aExistsNull Tells whether there are any NULL observers.
+ * Checking this parameter inside this function makes invoking code simpler.
+ * @param aObserverData Observer data object (usually a RObserverData).
+ * This data object must contain a container of observers and a semaphore.
+ */
+template <class ObserverDataType>
+static void RemoveNullObservers(TBool aExistsNull, ObserverDataType& aObserverData)
+    {
+    // semaphore must always be decremented 
+    --aObserverData.iSemaphore;    
+    if ( !aObserverData.iSemaphore && aExistsNull )
+        {
+        for (TInt i = aObserverData.iContainer.Count() - 1; i >= 0; --i)
+            {
+            if (aObserverData.iContainer[i] == NULL)
+                {
+                aObserverData.iContainer.Remove(i);
+                }
+            }
+        }
+    }
+    
+/**
+ * Macro that invokes an observer function for all registered observers.
+ * @param aNotification Observer function to call.
+ * @param aObserverData Observer data object (usually a RObserverData).
+ * This data object must contain a container of observers and a semaphore.
+ */
+#define RUN_NOTIFY_LOOP(aNotification, aObserverData) \
+do \
+    { \
+    if ( !aObserverData.iShutdown )\
+        {\
+        ++aObserverData.iSemaphore; \
+        TBool existsNull = EFalse; \
+        const TInt count = aObserverData.iContainer.Count(); \
+        for ( TInt i = 0; i < count; ++i ) \
+            { \
+            aObserverData.iObserver = aObserverData.iContainer[ i ]; \
+            if ( aObserverData.iObserver ) \
+                { \
+                TRAP_IGNORE( aObserverData.iObserver->aNotification ); \
+                } \
+            else \
+                { \
+                existsNull = ETrue; \
+                } \
+            } \
+        RemoveNullObservers(existsNull, \
+            aObserverData); \
+        }\
+    } while (EFalse) \
+
+/**
+ * Macro that invokes an observer function for all registered observers.
+ * @param aNotification Observer function to call.
+ * @param aObserverData Observer data object (usually a RObserverData).
+ * @param aError On return, contains the possible first error code that happened.
+ * This data object must contain a container of observers and a semaphore.
+ */
+#define RUN_NOTIFY_LOOP_L(aNotification, aObserverData, aError) \
+do \
+    { \
+    aError = KErrNone; \
+    TInt ___mtvObserverUtilsNotifyLoopError = KErrNone; \
+    if ( !aObserverData.iShutdown )\
+        {\
+        ++aObserverData.iSemaphore; \
+        TBool existsNull = EFalse; \
+        const TInt count = aObserverData.iContainer.Count(); \
+        for ( TInt i = 0; i < count; ++i ) \
+            { \
+            aObserverData.iObserver = aObserverData.iContainer[ i ]; \
+            if ( aObserverData.iObserver ) \
+                { \
+                TRAP( ___mtvObserverUtilsNotifyLoopError, aObserverData.iObserver->aNotification ); \
+                if ( aError == KErrNone ) \
+                    { \
+                    aError = ___mtvObserverUtilsNotifyLoopError; \
+                    } \
+                } \
+            else \
+                { \
+                existsNull = ETrue; \
+                } \
+            } \
+        RemoveNullObservers(existsNull, \
+            aObserverData); \
+        }\
+    } while (EFalse) \
+
+/**
+ * Adds an observer to an observer data object.
+ * @param aObserverData Data object to which an observer is added.
+ * @param aObserver Observer to add.
+ * @param aError Error code to use for Leave if adding fails.
+ */
+template <class ObserverType, class ContainerType>
+static void AddObserverL(ContainerType& aObserverData, ObserverType& aObserver, TInt aError)
+    {
+    if (aObserverData.iShutdown)
+        {
+        return;
+        }
+    TInt pos = aObserverData.iContainer.Find( &aObserver );
+    if (KErrNotFound != pos)
+        {
+        return;
+        }
+    TInt error = aObserverData.iContainer.Append( &aObserver );
+    if (KErrNone != error)
+        {
+        User::Leave(aError); 
+        }
+    }
+
+/**
+ * Removes an observer from an observer data object.
+ * @param aObserverData Data object from which an observer is removed.
+ * @param aObserver Observer to remove.
+ */
+template <class ObserverType, class ContainerType>
+static void RemoveObserver( ContainerType& aObserverData, ObserverType& aObserver )
+    {
+    TInt pos = aObserverData.iContainer.Find( &aObserver );
+    if ( KErrNotFound == pos  )
+        {
+        return;
+        }
+    if ( !aObserverData.iSemaphore )
+        {
+        // NotifyEventL is not part of call stack. Just remove.
+        aObserverData.iContainer.Remove( pos );
+        }
+    else
+        {
+        // Simply set to NULL. NotifyEventL will remove observers.
+        aObserverData.iContainer[ pos ] = NULL;
+        }
+    }
+
+} // end namespace MtvObserverUtils
+
+#endif //_MTV_OBSERVER_UTILS