code: /*
   * 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
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /*
   * $Id$
   */
  package org.apache.xpath.axes;
  
  import org.apache.xml.dtm.DTM;
  import org.apache.xml.dtm.DTMAxisIterator;
  import org.apache.xml.dtm.DTMFilter;
  import org.apache.xml.dtm.DTMIterator;
  import org.apache.xpath.Expression;
  import org.apache.xpath.XPathContext;
  import org.apache.xpath.compiler.Compiler;
  import org.apache.xpath.compiler.OpMap;
  
  /**
   * This class implements a general iterator for
   * those LocationSteps with only one step, and perhaps a predicate.
   * @see org.apache.xpath.axes#LocPathIterator
   * @xsl.usage advanced
   */
  public class OneStepIterator extends ChildTestIterator
  {
      static final long serialVersionUID = 4623710779664998283L;
    /** The traversal axis from where the nodes will be filtered. */
    protected int m_axis = -1;
  
    /** The DTM inner traversal class, that corresponds to the super axis. */
    protected DTMAxisIterator m_iterator;
  
    /**
     * Create a OneStepIterator object.
     *
     * @param compiler A reference to the Compiler that contains the op map.
     * @param opPos The position within the op map, which contains the
     * location path expression for this itterator.
     *
     * @throws javax.xml.transform.TransformerException
     */
    OneStepIterator(Compiler compiler, int opPos, int analysis)
            throws javax.xml.transform.TransformerException
    {
      super(compiler, opPos, analysis);
      int firstStepPos = OpMap.getFirstChildPos(opPos);
      
      m_axis = WalkerFactory.getAxisFromStep(compiler, firstStepPos);
      
    }
    
    
    /**
     * Create a OneStepIterator object.
     *
     * @param iterator The DTM iterator which this iterator will use.
     * @param axis One of Axis.Child, etc., or -1 if the axis is unknown.
     *
     * @throws javax.xml.transform.TransformerException
     */
    public OneStepIterator(DTMAxisIterator iterator, int axis)
            throws javax.xml.transform.TransformerException
    {
      super(null);
      
      m_iterator = iterator;
      m_axis = axis;
      int whatToShow = DTMFilter.SHOW_ALL;
      initNodeTest(whatToShow);
    }
    
    /**
     * Initialize the context values for this expression
     * after it is cloned.
     *
     * @param context The XPath runtime context for this
     * transformation.
     */
    public void setRoot(int context, Object environment)
    {
      super.setRoot(context, environment);
      if(m_axis > -1)
        m_iterator = m_cdtm.getAxisIterator(m_axis);
      m_iterator.setStartNode(m_context);
    }
  
    /**
     *  Detaches the iterator from the set which it iterated over, releasing
     * any computational resources and placing the iterator in the INVALID
     * state. After<code>detach</code> has been invoked, calls to
     * <code>nextNode</code> or<code>previousNode</code> will raise the
     * exception INVALID_STATE_ERR.
     */
    public void detach()
    {    
      if(m_allowDetach)
      {
        if(m_axis > -1)
          m_iterator = null;
        
        // Always call the superclass detach last!
        super.detach();
      }
    }
    
    /**
     * Get the next node via getFirstAttribute && getNextAttribute.
     */
    protected int getNextNode()
    {
      return m_lastFetched = m_iterator.next();
    }
    
    /**
     * Get a cloned iterator.
     *
     * @return A new iterator that can be used without mutating this one.
     *
     * @throws CloneNotSupportedException
     */
    public Object clone() throws CloneNotSupportedException
    {
      // Do not access the location path itterator during this operation!
      
      OneStepIterator clone = (OneStepIterator) super.clone();
  
      if(m_iterator != null)
      {
        clone.m_iterator = m_iterator.cloneIterator();
      }
      return clone;
    }
    
    /**
     *  Get a cloned Iterator that is reset to the beginning
     *  of the query.
     * 
     *  @return A cloned NodeIterator set of the start of the query.
     * 
     *  @throws CloneNotSupportedException
     */
    public DTMIterator cloneWithReset() throws CloneNotSupportedException
    {
  
      OneStepIterator clone = (OneStepIterator) super.cloneWithReset();
      clone.m_iterator = m_iterator;
  
      return clone;
    }
  
  
  
    /**
     * Tells if this is a reverse axes.  Overrides AxesWalker#isReverseAxes.
     *
     * @return true for this class.
     */
    public boolean isReverseAxes()
    {
      return m_iterator.isReverse();
    }
  
    /**
     * 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)
    {
      if(!isReverseAxes())
        return super.getProximityPosition(predicateIndex);
        
      // A negative predicate index seems to occur with
      // (preceding-sibling::*|following-sibling::*)/ancestor::*[position()]/*[position()]
      // -sb
      if(predicateIndex < 0)
        return -1;
        
      if (m_proximityPositions[predicateIndex] <= 0)
      {
        XPathContext xctxt = getXPathContext();
        try
        {
          OneStepIterator clone = (OneStepIterator) this.clone();
          
          int root = getRoot();
          xctxt.pushCurrentNode(root);
          clone.setRoot(root, xctxt);
  
          // clone.setPredicateCount(predicateIndex);
          clone.m_predCount = predicateIndex;
  
          // Count 'em all
          int count = 1;
          int next;
  
          while (DTM.NULL != (next = clone.nextNode()))
          {
            count++;
          }
  
          m_proximityPositions[predicateIndex] += count;
        }
        catch (CloneNotSupportedException cnse)
        {
  
          // can't happen
        }
        finally
        {
          xctxt.popCurrentNode();
        }
      }
  
      return m_proximityPositions[predicateIndex];
    }
  
    /**
     *  The number of nodes in the list. The range of valid child node indices
     * is 0 to <code>length-1</code> inclusive.
     *
     * @return The number of nodes in the list, always greater or equal to zero.
     */
    public int getLength()
    {
      if(!isReverseAxes())
        return super.getLength();
        
      // Tell if this is being called from within a predicate.
      boolean isPredicateTest = (this == m_execContext.getSubContextList());
  
      // And get how many total predicates are part of this step.
      int predCount = getPredicateCount();
     
      // If we have already calculated the length, and the current predicate 
      // is the first predicate, then return the length.  We don't cache 
      // the anything but the length of the list to the first predicate.
      if (-1 != m_length && isPredicateTest && m_predicateIndex < 1)
         return m_length;      
  
      int count = 0;
      
      XPathContext xctxt = getXPathContext();
      try
      {
        OneStepIterator clone = (OneStepIterator) this.cloneWithReset();
        
        int root = getRoot();
        xctxt.pushCurrentNode(root);
        clone.setRoot(root, xctxt);
   
        clone.m_predCount = m_predicateIndex;
  
        int next;
  
        while (DTM.NULL != (next = clone.nextNode()))
        {
          count++;
        }
      }
      catch (CloneNotSupportedException cnse)
      {
         // can't happen
      }
      finally
      {
        xctxt.popCurrentNode();
      }
      if (isPredicateTest && m_predicateIndex < 1)
        m_length = count;    
        
      return count;
    }
  
    /**
     * Count backwards one proximity position.
     *
     * @param i The predicate index.
     */
    protected void countProximityPosition(int i)
    {
      if(!isReverseAxes())
        super.countProximityPosition(i);
      else if (i < m_proximityPositions.length)
        m_proximityPositions[i]--;
    }
    
    /**
     * Reset the iterator.
     */
    public void reset()
    {
  
      super.reset();
      if(null != m_iterator)
        m_iterator.reset();
    }
    
    /**
     * Returns the axis being iterated, if it is known.
     * 
     * @return Axis.CHILD, etc., or -1 if the axis is not known or is of multiple 
     * types.
     */
    public int getAxis()
    {
      return m_axis;
    }
    
    /**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr)
    {
    	if(!super.deepEquals(expr))
    		return false;
    		
    	if(m_axis != ((OneStepIterator)expr).m_axis)
    		return false;
    		
    	return true;
    }
  
    
  }
  