// Copyright (c) 2005-2009 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:

 // Extension function interface

 //

 /**

  @file

  @publishedAll

  @released

 */

 #ifndef XMLENGXPATHFUNCTION_H

 #define XMLENGXPATHFUNCTION_H

 #include <xml/dom/xmlengxpathresult.h>

 class MXmlEngXPathEvaluationContext;

 /**

 Provides an interface for an object to participate in the evaluation of XPath

 expression via a XPath function call.

 Objects that implement the MXmlEngXPathExtensionFunction interface can be

 registered in a XmlEngXPathConfiguration object for global action (across

 all evaluations globally). 

 @see XmlEngXPathConfiguration::AddExtensionFunctionL()

 When the extension function is no longer required, it must be deregistered

 by calling XmlEngXPathConfiguration::RemoveExtensionFunction().

 */ 

 class MXmlEngXPathExtensionFunction

     {

 public:

     /** Evaluation status */

     enum TXmlEngEvaluationStatus

         {

 		/** Evaluation was accomplished successfully */

         ESucceeded,

 		/** An exceptional condition occurs */

         EError,

 		/** Type of argument does not match function specification */

         EInvalidArgumentType,

 		/** Number of arguments do not match function specification */

         EInvalidArgumentNumber

         };

 public:

     /** 

     Gets the minimum number of arguments the function can take.

     @return Minimum number of arguments

     */

     virtual TInt MinArity() {return 0;}

     /** 

     Gets the maximum number of arguments the function can take.

 	@return The maximum number of arguments or -1 if unbounded

     */

     virtual TInt MaxArity() {return MinArity();}

     /**

 	Called to evaluate the extension function.

 	This function is called only if simple arity constraints (min/max number of

 	arguments) are satisfied. The implementation of this function may need to

 	check further that the types of arguments and their positions in the

 	function call match function-specific requirements.

 	@param aEvalCtxt Evaluation context, which contains data about arguments

 	and provides a number of methods for setting the result of the extension

 	function.

     @return ESucceeded if evaluation success, otherwise one of the errors 

 	defined in TXmlEngEvaluationStatus.

     */

     virtual TXmlEngEvaluationStatus Evaluate(MXmlEngXPathEvaluationContext* aEvalCtxt) = 0; 

     };

 #endif /* XMLENGXPATHFUNCTION_H */