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 * reserved comment block
 * DO NOT REMOVE OR ALTER!
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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
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 * distributed under the License is distributed on an "AS IS" BASIS,
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package com.sun.org.apache.xpath.internal.operations;

import com.sun.org.apache.xml.internal.dtm.DTMManager;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.XPathContext;
import com.sun.org.apache.xpath.internal.objects.XNodeSet;
import com.sun.org.apache.xpath.internal.objects.XObject;


This is a "smart" variable reference that is used in situations where
an absolute path is optimized into a variable reference, but may
be used in some situations where the document context may have changed.
For instance, in select="document(doc/@href)//name[//salary > 7250]", the
root in the predicate will be different for each node in the set.  While
this is easy to detect statically in this case, in other cases static
detection would be very hard or impossible.  So, this class does a dynamic check
to make sure the document context of the referenced variable is the same as
the current document context, and, if it is not, execute the referenced variable's
expression with the current context instead.
/**
 * This is a "smart" variable reference that is used in situations where
 * an absolute path is optimized into a variable reference, but may
 * be used in some situations where the document context may have changed.
 * For instance, in select="document(doc/@href)//name[//salary > 7250]", the
 * root in the predicate will be different for each node in the set.  While
 * this is easy to detect statically in this case, in other cases static
 * detection would be very hard or impossible.  So, this class does a dynamic check
 * to make sure the document context of the referenced variable is the same as
 * the current document context, and, if it is not, execute the referenced variable's
 * expression with the current context instead.
 */
public class VariableSafeAbsRef extends Variable
{
    static final long serialVersionUID = -9174661990819967452L;

  
Dereference the variable, and return the reference value.  Note that lazy
evaluation will occur.  If a variable within scope is not found, a warning
will be sent to the error listener, and an empty nodeset will be returned.
Params:
xctxt – The runtime execution context.
Throws:
TransformerException – 
Returns:
The evaluated variable, or an empty nodeset if not found./**
   * Dereference the variable, and return the reference value.  Note that lazy
   * evaluation will occur.  If a variable within scope is not found, a warning
   * will be sent to the error listener, and an empty nodeset will be returned.
   *
   *
   * @param xctxt The runtime execution context.
   *
   * @return The evaluated variable, or an empty nodeset if not found.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt, boolean destructiveOK)
        throws javax.xml.transform.TransformerException
  {
        XNodeSet xns = (XNodeSet)super.execute(xctxt, destructiveOK);
        DTMManager dtmMgr = xctxt.getDTMManager();
        int context = xctxt.getContextNode();
        if(dtmMgr.getDTM(xns.getRoot()).getDocument() !=
           dtmMgr.getDTM(context).getDocument())
        {
                Expression expr = (Expression)xns.getContainedIter();
                xns = (XNodeSet)expr.asIterator(xctxt, context);
        }
        return xns;
  }

}