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.utils.PrefixResolver;
  import org.apache.xpath.Expression;
  import org.apache.xpath.ExpressionOwner;
  import org.apache.xpath.VariableStack;
  import org.apache.xpath.XPathContext;
  import org.apache.xpath.XPathVisitor;
  import org.apache.xpath.objects.XNodeSet;
  
  /**
   * Class to use for one-step iteration that doesn't have a predicate, and 
   * doesn't need to set the context.
   */
  public class FilterExprIteratorSimple extends LocPathIterator
  {
      static final long serialVersionUID = -6978977187025375579L;
    /** The contained expression. Should be non-null.
     *  @serial   */
    private Expression m_expr;
  
    /** The result of executing m_expr.  Needs to be deep cloned on clone op.  */
    transient private XNodeSet m_exprObj;
  
    private boolean m_mustHardReset = false;
    private boolean m_canDetachNodeset = true;
  
    /**
     * Create a FilterExprIteratorSimple object.
     *
     */
    public FilterExprIteratorSimple()
    {
      super(null);
    }
    
    /**
     * Create a FilterExprIteratorSimple object.
     *
     */
    public FilterExprIteratorSimple(Expression expr)
    {
      super(null);
      m_expr = expr;
    }
    
    /**
     * 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_exprObj = executeFilterExpr(context, m_execContext, getPrefixResolver(), 
    	                  getIsTopLevel(), m_stackFrame, m_expr);
    }
  
    /**
     * Execute the expression.  Meant for reuse by other FilterExpr iterators 
     * that are not derived from this object.
     */
    public static XNodeSet executeFilterExpr(int context, XPathContext xctxt, 
    												PrefixResolver prefixResolver,
    												boolean isTopLevel,
    												int stackFrame,
    												Expression expr )
      throws org.apache.xml.utils.WrappedRuntimeException
    {
      PrefixResolver savedResolver = xctxt.getNamespaceContext();
      XNodeSet result = null;
  
      try
      {
        xctxt.pushCurrentNode(context);
        xctxt.setNamespaceContext(prefixResolver);
  
        // The setRoot operation can take place with a reset operation, 
        // and so we may not be in the context of LocPathIterator#nextNode, 
        // so we have to set up the variable context, execute the expression, 
        // and then restore the variable context.
  
        if (isTopLevel)
        {
          // System.out.println("calling m_expr.execute(getXPathContext())");
          VariableStack vars = xctxt.getVarStack();
  
          // These three statements need to be combined into one operation.
          int savedStart = vars.getStackFrame();
          vars.setStackFrame(stackFrame);
  
          result = (org.apache.xpath.objects.XNodeSet) expr.execute(xctxt);
          result.setShouldCacheNodes(true);
  
          // These two statements need to be combined into one operation.
          vars.setStackFrame(savedStart);
        }
        else
            result = (org.apache.xpath.objects.XNodeSet) expr.execute(xctxt);
  
      }
      catch (javax.xml.transform.TransformerException se)
      {
  
        // TODO: Fix...
        throw new org.apache.xml.utils.WrappedRuntimeException(se);
      }
      finally
      {
        xctxt.popCurrentNode();
        xctxt.setNamespaceContext(savedResolver);
      }
      return result;
    }
    
    /**
     *  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)
    		return DTM.NULL;
  
      int next;
  
      if (null != m_exprObj)
      {
        m_lastFetched = next = m_exprObj.nextNode();
      }
      else
        m_lastFetched = next = DTM.NULL;
  
      // m_lastFetched = next;
      if (DTM.NULL != next)
      {
        m_pos++;
        return next;
      }
      else
      {
        m_foundLast = true;
  
        return DTM.NULL;
      }
    }
    
    /**
     * 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()
    {  
      if(m_allowDetach)
      {
    		super.detach();
    		m_exprObj.detach();
    		m_exprObj = null;
      }
    }
  
    /**
     * This function is used to fixup variables from QNames to stack frame 
     * indexes at stylesheet build time.
     * @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);
      m_expr.fixupVariables(vars, globalsSize);
    }
  
    /**
     * Get the inner contained expression of this filter.
     */
    public Expression getInnerExpression()
    {
      return m_expr;
    }
  
    /**
     * Set the inner contained expression of this filter.
     */
    public void setInnerExpression(Expression expr)
    {
      expr.exprSetParent(this);
      m_expr = expr;
    }
  
    /** 
     * Get the analysis bits for this walker, as defined in the WalkerFactory.
     * @return One of WalkerFactory#BIT_DESCENDANT, etc.
     */
    public int getAnalysisBits()
    {
      if (null != m_expr && m_expr instanceof PathComponent)
      {
        return ((PathComponent) m_expr).getAnalysisBits();
      }
      return WalkerFactory.BIT_FILTER;
    }
  
    /**
     * 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 true as a default.
     */
    public boolean isDocOrdered()
    {
      return m_exprObj.isDocOrdered();
    }
  
    class filterExprOwner implements ExpressionOwner
    {
      /**
      * @see ExpressionOwner#getExpression()
      */
      public Expression getExpression()
      {
        return m_expr;
      }
  
      /**
       * @see ExpressionOwner#setExpression(Expression)
       */
      public void setExpression(Expression exp)
      {
        exp.exprSetParent(FilterExprIteratorSimple.this);
        m_expr = exp;
      }
  
    }
  
    /**
     * This will traverse the heararchy, calling the visitor for 
     * each member.  If the called visitor method returns 
     * false, the subtree should not be called.
     * 
     * @param visitor The visitor whose appropriate method will be called.
     */
    public void callPredicateVisitors(XPathVisitor visitor)
    {
      m_expr.callVisitors(new filterExprOwner(), visitor);
  
      super.callPredicateVisitors(visitor);
    }
  
    /**
     * @see Expression#deepEquals(Expression)
     */
    public boolean deepEquals(Expression expr)
    {
      if (!super.deepEquals(expr))
        return false;
  
      FilterExprIteratorSimple fet = (FilterExprIteratorSimple) expr;
      if (!m_expr.deepEquals(fet.m_expr))
        return false;
  
      return true;
    }
    
    /**
     * 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()
    {
    	if(null != m_exprObj)
      	return m_exprObj.getAxis();
      else
      	return Axis.FILTEREDLIST;
    }
  
  
  }
  
  