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.DTMFilter;
  import org.apache.xml.dtm.DTMIterator;
  import org.apache.xml.utils.PrefixResolver;
  import org.apache.xpath.compiler.Compiler;
  import org.apache.xpath.compiler.OpMap;
  
  /**
   * Base for iterators that handle predicates.  Does the basic next 
   * node logic, so all the derived iterator has to do is get the 
   * next node.
   */
  public abstract class BasicTestIterator extends LocPathIterator
  {
      static final long serialVersionUID = 3505378079378096623L;
    /**
     * Create a LocPathIterator object.
     *
     * @param nscontext The namespace context for this iterator,
     * should be OK if null.
     */
    protected BasicTestIterator()
    {
    }
  
  
    /**
     * Create a LocPathIterator object.
     *
     * @param nscontext The namespace context for this iterator,
     * should be OK if null.
     */
    protected BasicTestIterator(PrefixResolver nscontext)
    {
  
      super(nscontext);
    }
  
    /**
     * Create a LocPathIterator object, 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.
     *
     * @throws javax.xml.transform.TransformerException
     */
    protected BasicTestIterator(Compiler compiler, int opPos, int analysis)
            throws javax.xml.transform.TransformerException
    {
      super(compiler, opPos, analysis, false);
      
      int firstStepPos = OpMap.getFirstChildPos(opPos);
      int whatToShow = compiler.getWhatToShow(firstStepPos);
  
      if ((0 == (whatToShow
                 & (DTMFilter.SHOW_ATTRIBUTE 
                 | DTMFilter.SHOW_NAMESPACE 
                 | 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 LocPathIterator object, 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
     */
    protected BasicTestIterator(
            Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers)
              throws javax.xml.transform.TransformerException
    {
      super(compiler, opPos, analysis, shouldLoadWalkers);
    }
  
  	
    /**
     * Get the next node via getNextXXX.  Bottlenecked for derived class override.
     * @return The next node on the axis, or DTM.NULL.
     */
    protected abstract int getNextNode();
  
    /**
     *  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.
     */
    public int nextNode()
    {      
    	if(m_foundLast)
    	{
    		m_lastFetched = DTM.NULL;
    		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
        {
          next = getNextNode();
    
          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);
        }
      }
    }
    
    /**
     *  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
    {
  
      ChildTestIterator clone = (ChildTestIterator) super.cloneWithReset();
  
      clone.resetProximityPositions();
  
      return clone;
    }
  
  
  }
  
  