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

/*
 * The Apache Software License, Version 1.1
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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 'descendant' axes.
 * @see <a href="http://www.w3.org/TR/xpath#axes">XPath axes descriptions</a>
 */
public class DescendantWalker extends AxesWalker
{

  /**
   * Construct an DescendantWalker using a LocPathIterator.
   *
   * @param locPathIterator The location path iterator that 'owns' this walker.
   */
  public DescendantWalker(LocPathIterator locPathIterator)
  {
    super(locPathIterator);
  }

  /**
   *  Set the root node of the TreeWalker.
   *
   * @param root The context node of this step.
   */
  public void setRoot(int root)
  {
    m_nextLevelAmount = getDTM(root).hasChildNodes(root) ? 1 : 0;

    super.setRoot(root);
  }

  /**
   *  Moves to and returns the closest visible ancestor node of the current
   * node. If the search for parentNode attempts to step upward from the
   * TreeWalker's root node, or if it fails to find a visible ancestor
   * node, this method retains the current position and returns null.
   * @return  The new parent node, or null if the current node has no parent
   *   in the TreeWalker's logical view.
   */
  public int parentNode()
  {

    int n;

    if (m_root == m_currentNode) // why not == ?  -sb
    {
      n = DTM.NULL;
    }
    else
    {
      int p = getDTM(m_currentNode).getParent(m_currentNode);

      n = (m_root == p) ? DTM.NULL : p;
    }

    m_nextLevelAmount = 0;

    return setCurrentIfNotNull(n);
  }

  /**
   *  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()
  {
    DTM dtm = getDTM(m_currentNode);
    int next = (dtm.getNodeType(m_currentNode) != DTM.ATTRIBUTE_NODE) ?
                dtm.getFirstChild(m_currentNode) : DTM.NULL;

    m_nextLevelAmount = (DTM.NULL == next) ? 0 : (dtm.hasChildNodes(next) ? 1 : 0);

    return setCurrentIfNotNull(next);
  }

  /**
   *  Moves the <code>TreeWalker</code> to the next sibling of the current
   * node, and returns the new node. If the current node has no visible
   * next sibling, returns <code>null</code> , and retains the current node.
   * @return  The new node, or <code>null</code> if the current node has no
   *   next sibling in the TreeWalker's logical view.
   */
  public int nextSibling()
  {
    DTM dtm = getDTM(m_root);
    int next = (m_root == m_currentNode)
                ? DTM.NULL : dtm.getNextSibling(m_currentNode);

    m_nextLevelAmount = (DTM.NULL == next) ? 0 : (dtm.hasChildNodes(next) ? 1 : 0);

    return setCurrentIfNotNull(next);
  }

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