src/org/apache/xpath/axes/RootWalker.java

/*
 * The Apache Software License, Version 1.1
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 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
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 * This software consists of voluntary contributions made by many
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 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
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package org.apache.xpath.axes;

import org.apache.xpath.axes.LocPathIterator;
import org.apache.xpath.XPath;
import org.apache.xpath.XPathContext;

//import org.w3c.dom.Node;
import org.apache.xml.dtm.DTM;

/**
 * Walker for the FROM_ROOT axes.
 * @see <a href="http://www.w3.org/TR/xpath#location-paths">XPath location-paths descriptions</a>
 * @see <a href="http://www.w3.org/TR/xpath#NT-AbsoluteLocationPath">XPath AbsoluteLocationPath descriptions</a>
 * @see <a href="http://www.w3.org/TR/xpath#NT-AbbreviatedAbsoluteLocationPath">XPath AbbreviatedAbsoluteLocationPath descriptions</a>
 */
public class RootWalker extends AxesWalker
{

  /**
   * Construct a RootWalker using a LocPathIterator.
   *
   * @param locPathIterator The location path iterator that 'owns' this walker.
   */
  public RootWalker(LocPathIterator locPathIterator)
  {

    super(locPathIterator);

    m_nextLevelAmount = 0;
  }

  /**
   *  Set the root node of the TreeWalker.
   *
   * @param root The context node of this step.
   */
  public void setRoot(int root)
  {      

    super.setRoot(root);
    m_processedRoot = false;
  }

  /**
   *  Moves the <code>TreeWalker</code> to the first visible child of the
   * current node, and returns the new node. If the current node has no
   * visible children, returns <code>null</code> , and retains the current
   * node.
   * @return  The new node, or <code>null</code> if the current node has no
   *   visible children in the TreeWalker's logical view.
   */
  public int firstChild()
  {

    // Follow rule about returning the first occuring in document order 
    // as the first child.  Strange but true.
    if (!m_processedRoot)
    {
      m_processedRoot = true;

      int n = getDTM(m_currentNode).getDocument();

      return setCurrentIfNotNull(n);
    }

    return DTM.NULL;
  }

  /** True if the root node has been processed.   */
  transient boolean m_processedRoot = false;

  /**
   * Tell what's the maximum level this axes can descend to.
   *
   * @return Always 1.
   */
  protected int getLevelMax()
  {
    return 1;
  }
}