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package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;
import com.sun.org.apache.xpath.internal.XPathContext;


Walker for a reverse axes.

See Also:
/**
 * Walker for a reverse axes.
 * @see <a href="http://www.w3.org/TR/xpath#predicates">XPath 2.4 Predicates</a>
 */
public class ReverseAxesWalker extends AxesWalker
{
    static final long serialVersionUID = 2847007647832768941L;

  
Construct an AxesWalker using a LocPathIterator.

Params:
  • locPathIterator – The location path iterator that 'owns' this walker.
/**
   * Construct an AxesWalker using a LocPathIterator.
   *
   * @param locPathIterator The location path iterator that 'owns' this walker.
   */
  ReverseAxesWalker(LocPathIterator locPathIterator, int axis)
  {
    super(locPathIterator, axis);
  }

  
Set the root node of the TreeWalker.
(Not part of the DOM2 TreeWalker interface).

Params:
  • root – The context node of this step.
/**
   * Set the root node of the TreeWalker.
   * (Not part of the DOM2 TreeWalker interface).
   *
   * @param root The context node of this step.
   */
  public void setRoot(int root)
  {
    super.setRoot(root);
    m_iterator = getDTM(root).getAxisIterator(m_axis);
    m_iterator.setStartNode(root);
  }

  
Detaches the walker from the set which it iterated over, releasing
any computational resources and placing the iterator in the INVALID
state.

/**
   * Detaches the walker from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state.
   */
  public void detach()
  {
    m_iterator = null;
    super.detach();
  }

  
Get the next node in document order on the axes.

Returns:the next node in document order on the axes, or null.
/**
   * Get the next node in document order on the axes.
   *
   * @return the next node in document order on the axes, or null.
   */
  protected int getNextNode()
  {
    if (m_foundLast)
      return DTM.NULL;

    int next = m_iterator.next();

    if (m_isFresh)
      m_isFresh = false;

    if (DTM.NULL == next)
      this.m_foundLast = true;

    return next;
  }


  
Tells if this is a reverse axes.  Overrides AxesWalker#isReverseAxes.

Returns:true for this class.
/**
   * Tells if this is a reverse axes.  Overrides AxesWalker#isReverseAxes.
   *
   * @return true for this class.
   */
  public boolean isReverseAxes()
  {
    return true;
  }

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

  
Get the current sub-context position.  In order to do the
reverse axes count, for the moment this re-searches the axes
up to the predicate.  An optimization on this is to cache
the nodes searched, but, for the moment, this case is probably
rare enough that the added complexity isn't worth it.

Params:
  • predicateIndex – The predicate index of the proximity position.
Returns:The pridicate index, or -1.
/**
   * Get the current sub-context position.  In order to do the
   * reverse axes count, for the moment this re-searches the axes
   * up to the predicate.  An optimization on this is to cache
   * the nodes searched, but, for the moment, this case is probably
   * rare enough that the added complexity isn't worth it.
   *
   * @param predicateIndex The predicate index of the proximity position.
   *
   * @return The pridicate index, or -1.
   */
  protected int getProximityPosition(int predicateIndex)
  {
    // A negative predicate index seems to occur with
    // (preceding-sibling::*|following-sibling::*)/ancestor::*[position()]/*[position()]
    // -sb
    if(predicateIndex < 0)
      return -1;

    int count = m_proximityPositions[predicateIndex];

    if (count <= 0)
    {
      AxesWalker savedWalker = wi().getLastUsedWalker();

      try
      {
        ReverseAxesWalker clone = (ReverseAxesWalker) this.clone();

        clone.setRoot(this.getRoot());

        clone.setPredicateCount(predicateIndex);

        clone.setPrevWalker(null);
        clone.setNextWalker(null);
        wi().setLastUsedWalker(clone);

        // Count 'em all
        count++;
        int next;

        while (DTM.NULL != (next = clone.nextNode()))
        {
          count++;
        }

        m_proximityPositions[predicateIndex] = count;
      }
      catch (CloneNotSupportedException cnse)
      {

        // can't happen
      }
      finally
      {
        wi().setLastUsedWalker(savedWalker);
      }
    }

    return count;
  }

  
Count backwards one proximity position.

Params:
  • i – The predicate index.
/**
   * Count backwards one proximity position.
   *
   * @param i The predicate index.
   */
  protected void countProximityPosition(int i)
  {
    if (i < m_proximityPositions.length)
      m_proximityPositions[i]--;
  }

  
Get the number of nodes in this node list.  The function is probably ill
named?

Params:
  • xctxt – The XPath runtime context.
Returns:the number of nodes in this node list.
/**
   * Get the number of nodes in this node list.  The function is probably ill
   * named?
   *
   *
   * @param xctxt The XPath runtime context.
   *
   * @return the number of nodes in this node list.
   */
  public int getLastPos(XPathContext xctxt)
  {

    int count = 0;
    AxesWalker savedWalker = wi().getLastUsedWalker();

    try
    {
      ReverseAxesWalker clone = (ReverseAxesWalker) this.clone();

      clone.setRoot(this.getRoot());

      clone.setPredicateCount(this.getPredicateCount() - 1);

      clone.setPrevWalker(null);
      clone.setNextWalker(null);
      wi().setLastUsedWalker(clone);

      // Count 'em all
      // count = 1;
      int next;

      while (DTM.NULL != (next = clone.nextNode()))
      {
        count++;
      }
    }
    catch (CloneNotSupportedException cnse)
    {

      // can't happen
    }
    finally
    {
      wi().setLastUsedWalker(savedWalker);
    }

    return count;
  }

  
Returns true if all the nodes in the iteration well be returned in document
order.
Warning: This can only be called after setRoot has been called!

Returns:false.
/**
   * Returns true if all the nodes in the iteration well be returned in document
   * order.
   * Warning: This can only be called after setRoot has been called!
   *
   * @return false.
   */
  public boolean isDocOrdered()
  {
    return false;  // I think.
  }

  
The DTM inner traversal class, that corresponds to the super axis. 
/** The DTM inner traversal class, that corresponds to the super axis. */
  protected DTMAxisIterator m_iterator;
}