expression.h

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/*
 * expression.h - Copyright 2005 Frerich Raabe <raabe@kde.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
#ifndef EXPRESSION_H
#define EXPRESSION_H

#include "util.h"

#include <QHash>
#include <QList>

#include <dom/dom_string.h>
#include <xml/dom_stringimpl.h>
#include <xml/dom_nodelistimpl.h>
#include <misc/shared.h>

namespace DOM {
    class NodeImpl;
}

namespace khtml {

class XPathNSResolverImpl;
namespace XPath {

struct EvaluationContext
{
    EvaluationContext() { reset(0, 0); }

    void reset(DOM::NodeImpl* ctx, XPathNSResolverImpl* res) {
        node     = ctx;
        resolver = res;
        size     = 1;
        position = 1;
        exceptionCode = 0;
    }

    DOM::NodeImpl *node;
    unsigned long size;
    unsigned long position;
    QHash<DOM::DOMString, DOM::DOMString> variableBindings;

    // reports only first one.
    void reportException(int ec) { if (!exceptionCode) exceptionCode = ec; } 

    int exceptionCode;
    
    /* The function library is globally accessible through
     * FunctionLibrary::self()
     */
    XPathNSResolverImpl *resolver;
};

class Value
{
    public:
        enum Type {
            Nodeset, Boolean, Number, String
        };

        Value();
        explicit Value( DOM::NodeImpl *value );
        explicit Value( const DomNodeList &value );
        explicit Value( bool value );
        explicit Value( double value );
        explicit Value( const DOM::DOMString &value );

        Type type() const;
        bool isNodeset() const;
        bool isBoolean() const;
        bool isNumber() const;
        bool isString() const;

        DomNodeList &toNodeset(); // may return 0
        const DomNodeList &toNodeset() const;
        bool toBoolean() const;
        double toNumber() const;
        DOM::DOMString toString() const;

        QString dump() const;

    private:
        // Catch undesired conversions -- this manages to go to bool otherwise!
        explicit Value( const char* );
    
        Type m_type;
        DomNodeList m_nodeset;
        bool m_bool;
        double m_number;
        DOM::DOMString m_string;
};

class Expression
{
    public:
        static EvaluationContext &evaluationContext();

        Expression();
        virtual ~Expression();
        virtual Value evaluate() const;

        void addSubExpression( Expression *expr );
        void optimize();
        virtual bool isConstant() const;

        virtual QString dump() const = 0;

        static void reportInvalidExpressionErr();
        static void reportNamespaceErr();
    protected:
        unsigned int subExprCount() const;
        Expression *subExpr( unsigned int i );
        const Expression *subExpr( unsigned int i ) const;

    private:
        virtual Value doEvaluate() const = 0;

        QList<Expression *> m_subExpressions;
        Value *m_constantValue;
};

} // namespace XPath

} // namespace khtml

#endif // EXPRESSION_H

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