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.utils.PrefixResolver;
  import org.apache.xpath.compiler.Compiler;
  
  /**
   * This class iterates over set of nodes that needs to be sorted.
   * @xsl.usage internal
   */
  public class WalkingIteratorSorted extends WalkingIterator
  {
      static final long serialVersionUID = -4512512007542368213L;
  
  //  /** True if the nodes will be found in document order */
  //  protected boolean m_inNaturalOrder = false;
    
    /** True if the nodes will be found in document order, and this can 
     * be determined statically. */
    protected boolean m_inNaturalOrderStatic = false;
  
    /**
     * Create a WalkingIteratorSorted object.
     *
     * @param nscontext The namespace context for this iterator,
     * should be OK if null.
     */
    public WalkingIteratorSorted(PrefixResolver nscontext)
    {
      super(nscontext);
    }
  
    /**
     * Create a WalkingIterator iterator, including creation
     * of step walkers from the opcode list, and call back
     * into the Compiler to create predicate expressions.
     *
     * @param compiler The Compiler which is creating
     * this expression.
     * @param opPos The position of this iterator in the
     * opcode list from the compiler.
     * @param shouldLoadWalkers True if walkers should be
     * loaded, or false if this is a derived iterator and
     * it doesn't wish to load child walkers.
     *
     * @throws javax.xml.transform.TransformerException
     */
    WalkingIteratorSorted(
            Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers)
              throws javax.xml.transform.TransformerException
    {
      super(compiler, opPos, analysis, shouldLoadWalkers);
    }
    
    /**
     * Returns true if all the nodes in the iteration well be returned in document 
     * order.
     * 
     * @return true as a default.
     */
    public boolean isDocOrdered()
    {
      return m_inNaturalOrderStatic;
    }
  
      
    /**
     * Tell if the nodeset can be walked in doc order, via static analysis. 
     *
     *
     * @return true if the nodeset can be walked in doc order, without sorting.
     */
    boolean canBeWalkedInNaturalDocOrderStatic()
    {
  
      if (null != m_firstWalker)
      {
        AxesWalker walker = m_firstWalker;
        int prevAxis = -1;
        boolean prevIsSimpleDownAxis = true;
  
        for(int i = 0; null != walker; i++)
        {
          int axis = walker.getAxis();
          
          if(walker.isDocOrdered())
          {
            boolean isSimpleDownAxis = ((axis == Axis.CHILD)
                                     || (axis == Axis.SELF)
                                     || (axis == Axis.ROOT));
            // Catching the filtered list here is only OK because
            // FilterExprWalker#isDocOrdered() did the right thing.
            if(isSimpleDownAxis || (axis == -1))
              walker = walker.getNextWalker();
            else
            {
              boolean isLastWalker = (null == walker.getNextWalker());
              if(isLastWalker)
              {
                if(walker.isDocOrdered() && (axis == Axis.DESCENDANT || 
                   axis == Axis.DESCENDANTORSELF || axis == Axis.DESCENDANTSFROMROOT
                   || axis == Axis.DESCENDANTSORSELFFROMROOT) || (axis == Axis.ATTRIBUTE))
                  return true;
              }
              return false;
            }
          }
          else
            return false;
        }
        return true;
      }
      return false;
    }
  
  
  //  /**
  //   * NEEDSDOC Method canBeWalkedInNaturalDocOrder 
  //   *
  //   *
  //   * NEEDSDOC (canBeWalkedInNaturalDocOrder) @return
  //   */
  //  boolean canBeWalkedInNaturalDocOrder()
  //  {
  //
  //    if (null != m_firstWalker)
  //    {
  //      AxesWalker walker = m_firstWalker;
  //      int prevAxis = -1;
  //      boolean prevIsSimpleDownAxis = true;
  //
  //      for(int i = 0; null != walker; i++)
  //      {
  //        int axis = walker.getAxis();
  //        
  //        if(walker.isDocOrdered())
  //        {
  //          boolean isSimpleDownAxis = ((axis == Axis.CHILD)
  //                                   || (axis == Axis.SELF)
  //                                   || (axis == Axis.ROOT));
  //          // Catching the filtered list here is only OK because
  //          // FilterExprWalker#isDocOrdered() did the right thing.
  //          if(isSimpleDownAxis || (axis == -1))
  //            walker = walker.getNextWalker();
  //          else
  //          {
  //            boolean isLastWalker = (null == walker.getNextWalker());
  //            if(isLastWalker)
  //            {
  //              if(walker.isDocOrdered() && (axis == Axis.DESCENDANT || 
  //                 axis == Axis.DESCENDANTORSELF || axis == Axis.DESCENDANTSFROMROOT
  //                 || axis == Axis.DESCENDANTSORSELFFROMROOT) || (axis == Axis.ATTRIBUTE))
  //                return true;
  //            }
  //            return false;
  //          }
  //        }
  //        else
  //          return false;
  //      }
  //      return true;
  //    }
  //    return false;
  //  }
    
    /**
     * This function is used to perform some extra analysis of the iterator.
     * 
     * @param vars List of QNames that correspond to variables.  This list 
     * should be searched backwards for the first qualified name that 
     * corresponds to the variable reference qname.  The position of the 
     * QName in the vector from the start of the vector will be its position 
     * in the stack frame (but variables above the globalsTop value will need 
     * to be offset to the current stack frame).
     */
    public void fixupVariables(java.util.Vector vars, int globalsSize)
    {
      super.fixupVariables(vars, globalsSize);
  
      int analysis = getAnalysisBits();
      if(WalkerFactory.isNaturalDocOrder(analysis))
      {
      	m_inNaturalOrderStatic = true;
      }
      else
      {
      	m_inNaturalOrderStatic = false;
      	// System.out.println("Setting natural doc order to false: "+
      	//    WalkerFactory.getAnalysisString(analysis));
      }
      
    }
  
  }
  