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.Axis;
  import org.apache.xml.dtm.DTM;
  import org.apache.xml.dtm.DTMAxisTraverser;
  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.OpCodes;
  import org.apache.xpath.compiler.OpMap;
  import org.apache.xpath.patterns.NodeTest;
  
  /**
   * This class implements an optimized iterator for
   * descendant, descendant-or-self, or "//foo" patterns.
   * @see org.apache.xpath.axes.LocPathIterator
   * @xsl.usage advanced
   */
  public class DescendantIterator extends LocPathIterator
  {
      static final long serialVersionUID = -1190338607743976938L;
    /**
     * Create a DescendantIterator 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
     */
    DescendantIterator(Compiler compiler, int opPos, int analysis)
            throws javax.xml.transform.TransformerException
    {
  
      super(compiler, opPos, analysis, false);
  
      int firstStepPos = OpMap.getFirstChildPos(opPos);
      int stepType = compiler.getOp(firstStepPos);
  
      boolean orSelf = (OpCodes.FROM_DESCENDANTS_OR_SELF == stepType);
      boolean fromRoot = false;
      if (OpCodes.FROM_SELF == stepType)
      {
        orSelf = true;
        // firstStepPos += 8;
      }
      else if(OpCodes.FROM_ROOT == stepType)
      {
        fromRoot = true;
        // Ugly code... will go away when AST work is done.
        int nextStepPos = compiler.getNextStepPos(firstStepPos);
        if(compiler.getOp(nextStepPos) == OpCodes.FROM_DESCENDANTS_OR_SELF)
          orSelf = true;
        // firstStepPos += 8;
      }
      
      // Find the position of the last step.
      int nextStepPos = firstStepPos;
      while(true)
      {
        nextStepPos = compiler.getNextStepPos(nextStepPos);
        if(nextStepPos > 0)
        {
          int stepOp = compiler.getOp(nextStepPos);
          if(OpCodes.ENDOP != stepOp)
            firstStepPos = nextStepPos;
          else
            break;
        }
        else
          break;
        
      }
      
      // Fix for http://nagoya.apache.org/bugzilla/show_bug.cgi?id=1336
      if((analysis & WalkerFactory.BIT_CHILD) != 0)
        orSelf = false;
        
      if(fromRoot)
      {
        if(orSelf)
          m_axis = Axis.DESCENDANTSORSELFFROMROOT;
        else
          m_axis = Axis.DESCENDANTSFROMROOT;
      }
      else if(orSelf)
        m_axis = Axis.DESCENDANTORSELF;
      else
        m_axis = Axis.DESCENDANT;
  
      int whatToShow = compiler.getWhatToShow(firstStepPos);
  
      if ((0 == (whatToShow
                 & (DTMFilter.SHOW_ATTRIBUTE | DTMFilter.SHOW_ELEMENT
                    | DTMFilter.SHOW_PROCESSING_INSTRUCTION))) || 
                     (whatToShow == DTMFilter.SHOW_ALL))
        initNodeTest(whatToShow);
      else
      {
        initNodeTest(whatToShow, compiler.getStepNS(firstStepPos),
                                compiler.getStepLocalName(firstStepPos));
      }
      initPredicateInfo(compiler, firstStepPos);
    }
    
    /**
     * Create a DescendantIterator object.
     *
     */
    public DescendantIterator()
    {
      super(null);
      m_axis = Axis.DESCENDANTSORSELFFROMROOT;
      int whatToShow = DTMFilter.SHOW_ALL;
      initNodeTest(whatToShow);
    }
  
    
    /**
     *  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
    {
  
      DescendantIterator clone = (DescendantIterator) super.cloneWithReset();
      clone.m_traverser = m_traverser;
  
      clone.resetProximityPositions();
  
      return clone;
    }
  
    /**
     *  Returns the next node in the set and advances the position of the
     * iterator in the set. After a NodeIterator is created, the first call
     * to nextNode() returns the first node in the set.
     *
     * @return  The next <code>Node</code> in the set being iterated over, or
     *   <code>null</code> if there are no more members in that set.
     *
     * @throws DOMException
     *    INVALID_STATE_ERR: Raised if this method is called after the
     *   <code>detach</code> method was invoked.
     */
    public int nextNode()
    {
     	if(m_foundLast)
    		return DTM.NULL;
  
      if(DTM.NULL == m_lastFetched)
      {
        resetProximityPositions();
      }
  
      int next;
      
      org.apache.xpath.VariableStack vars;
      int savedStart;
      if (-1 != m_stackFrame)
      {
        vars = m_execContext.getVarStack();
  
        // These three statements need to be combined into one operation.
        savedStart = vars.getStackFrame();
  
        vars.setStackFrame(m_stackFrame);
      }
      else
      {
        // Yuck.  Just to shut up the compiler!
        vars = null;
        savedStart = 0;
      }
      
      try
      {
        do
        {
          if(0 == m_extendedTypeID)
          {
            next = m_lastFetched = (DTM.NULL == m_lastFetched)
                         ? m_traverser.first(m_context)
                         : m_traverser.next(m_context, m_lastFetched);
          }
          else
          {
            next = m_lastFetched = (DTM.NULL == m_lastFetched)
                         ? m_traverser.first(m_context, m_extendedTypeID)
                         : m_traverser.next(m_context, m_lastFetched, 
                                            m_extendedTypeID);
          }
    
          if (DTM.NULL != next)
          {
            if(DTMIterator.FILTER_ACCEPT == acceptNode(next))
              break;
            else
              continue;
          }
          else
            break;
        }
        while (next != DTM.NULL);
    
        if (DTM.NULL != next)
        {
        	m_pos++;
          return next;
        }
        else
        {
          m_foundLast = true;
    
          return DTM.NULL;
        }
      }
      finally
      {
        if (-1 != m_stackFrame)
        {
          // These two statements need to be combined into one operation.
          vars.setStackFrame(savedStart);
        }
      }
    }
    
    /**
     * 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);
      m_traverser = m_cdtm.getAxisTraverser(m_axis);
      
      String localName = getLocalName();
      String namespace = getNamespace();
      int what = m_whatToShow;
      // System.out.println("what: ");
      // NodeTest.debugWhatToShow(what);
      if(DTMFilter.SHOW_ALL == what
         || NodeTest.WILD.equals(localName)
         || NodeTest.WILD.equals(namespace))
      {
        m_extendedTypeID = 0;
      }
      else
      {
        int type = getNodeTypeTest(what);
        m_extendedTypeID = m_cdtm.getExpandedTypeID(namespace, localName, type);
      }
      
    }
    
    /**
     * Return the first node out of the nodeset, if this expression is 
     * a nodeset expression.  This is the default implementation for 
     * nodesets.
     * <p>WARNING: Do not mutate this class from this function!</p>
     * @param xctxt The XPath runtime context.
     * @return the first node out of the nodeset, or DTM.NULL.
     */
    public int asNode(XPathContext xctxt)
      throws javax.xml.transform.TransformerException
    {
      if(getPredicateCount() > 0)
        return super.asNode(xctxt);
  
      int current = xctxt.getCurrentNode();
      
      DTM dtm = xctxt.getDTM(current);
      DTMAxisTraverser traverser = dtm.getAxisTraverser(m_axis);
      
      String localName = getLocalName();
      String namespace = getNamespace();
      int what = m_whatToShow;
      
      // System.out.print(" (DescendantIterator) ");
      
      // System.out.println("what: ");
      // NodeTest.debugWhatToShow(what);
      if(DTMFilter.SHOW_ALL == what
         || localName == NodeTest.WILD
         || namespace == NodeTest.WILD)
      {
        return traverser.first(current);
      }
      else
      {
        int type = getNodeTypeTest(what);
        int extendedType = dtm.getExpandedTypeID(namespace, localName, type);
        return traverser.first(current, extendedType);
      }
    }
    
    /**
     *  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) {
        m_traverser = null;    
        m_extendedTypeID = 0;
  
        // Always call the superclass detach last!
        super.detach();
      }
    }
    
    /**
     * 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;
    }
    
    
    /** The traverser to use to navigate over the descendants. */
    transient protected DTMAxisTraverser m_traverser;
    
    /** The axis that we are traversing. */
    protected int m_axis;
    
    /** The extended type ID, not set until setRoot. */
    protected int m_extendedTypeID;
    
    /**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr)
    {
    	if(!super.deepEquals(expr))
    		return false;
    		
    	if(m_axis != ((DescendantIterator)expr).m_axis)
    		return false;
    		
    	return true;
    }
  
    
  }
  