libreoffice/forms/source/xforms/computedexpression.hxx

/*************************************************************************
 *
 *  $RCSfile: computedexpression.hxx,v $
 *
 *  $Revision: 1.3 $
 *
 *  last change: $Author: vg $ $Date: 2005-03-23 11:35:16 $
 *
 *  The Contents of this file are made available subject to the terms of
 *  either of the following licenses
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 *         - GNU Lesser General Public License Version 2.1
 *         - Sun Industry Standards Source License Version 1.1
 *
 *  Sun Microsystems Inc., October, 2000
 *
 *  GNU Lesser General Public License Version 2.1
 *  =============================================
 *  Copyright 2000 by Sun Microsystems, Inc.
 *  901 San Antonio Road, Palo Alto, CA 94303, USA
 *
 *  This library is free software; you can redistribute it and/or
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 *  Lesser General Public License for more details.
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 *  MA  02111-1307  USA
 *
 *
 *  Sun Industry Standards Source License Version 1.1
 *  =================================================
 *  The contents of this file are subject to the Sun Industry Standards
 *  Source License Version 1.1 (the "License"); You may not use this file
 *  except in compliance with the License. You may obtain a copy of the
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 ************************************************************************/

#ifndef _COMPUTEDEXPRESSION_HXX
#define _COMPUTEDEXPRESSION_HXX


// includes for member variables
#include <rtl/ustring.hxx>
#include <com/sun/star/uno/Reference.hxx>

// forward declaractions
namespace com { namespace sun { namespace star
{
    namespace xml
    {
        namespace dom { class XNode; }
        namespace dom { class XNodeset; }
        namespace xpath { class XXPathAPI; }
        namespace xpath { class XXPathObject; }
    }
    namespace container { class XNameContainer; }
} } }
namespace xforms { class EvaluationContext; }



namespace xforms
{

/** ComputedExpression represents an XPath Expression and caches results.
 *
 * As this class has no virtual methods, it should never be used
 * polymorphically. */
class ComputedExpression
{
    /// the expression string
    rtl::OUString msExpression;

    /// is msExpression empty?
    bool mbIsEmpty;

protected:
    /// is msExpression a simple expression?
    bool mbIsSimple;

    /// the result from the last bind
    com::sun::star::uno::Reference<com::sun::star::xml::xpath::XXPathObject> mxResult;


    /// implementation of isSimpleExpression
    bool _checkExpression( const sal_Char* pExpression ) const;

    /// allow manipulation of the expression before it is evaluated
    const rtl::OUString _getExpressionForEvaluation() const;

    /// obtain a (suitable) XPathAPI implementation
    com::sun::star::uno::Reference<com::sun::star::xml::xpath::XXPathAPI> _getXPathAPI(const xforms::EvaluationContext& aContext);

    /// evaluate the expression relative to the content node.
    bool _evaluate( const xforms::EvaluationContext& rContext,
                    const rtl::OUString& sExpression );


public:
    ComputedExpression();
    ~ComputedExpression();


    /// get the expression string
    rtl::OUString getExpression() const;

    /// set a new expression string
    void setExpression( const rtl::OUString& rExpression );

    /// get the namespaces that are used to interpret the expression string
    com::sun::star::uno::Reference<com::sun::star::container::XNameContainer> getNamespaces() const;

    /// set the namespaces that are used to interpret the expression string
    void setNamespaces( const com::sun::star::uno::Reference<com::sun::star::container::XNameContainer>& );

    /// do we have an actual expression?
    bool isEmptyExpression() const;

    /// heuristically determine whether this expression is 'simple',
    /// i.e. whether its value will change depending on the values
    /// of other nodes
    bool isSimpleExpression() const;


    /// evaluate the expression relative to the content node.
    bool evaluate( const xforms::EvaluationContext& rContext );


    /// does this expression have a value?
    bool hasValue() const;


    /// remove value/evaluate results
    void clear();


    // get the result of this expression as string/bool/...
    // (Results will be based on the last call of evaluate(..). The caller
    // must call evaluate to ensure current results.)
    com::sun::star::uno::Reference<com::sun::star::xml::xpath::XXPathObject> getXPath();
    bool getBool( bool bDefault = false ) const;
    rtl::OUString getString( const rtl::OUString& rDefault = rtl::OUString() ) const;

};

} // namespace xforms

#endif