unionpathiterator.java

java1.6众多例子参考

/*
 * Copyright 1999-2004 The Apache Software Foundation.
 *
 * Licensed 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: UnionPathIterator.java,v 1.2.4.1 2005/09/14 19:43:25 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xpath.internal.Expression;
import com.sun.org.apache.xpath.internal.ExpressionOwner;
import com.sun.org.apache.xpath.internal.XPathVisitor;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.compiler.OpCodes;

/**
 * This class extends NodeSetDTM, which implements DTMIterator,
 * and fetches nodes one at a time in document order based on a XPath
 * <a href="http://www.w3.org/TR/xpath#NT-UnionExpr">UnionExpr</a>.
 * As each node is iterated via nextNode(), the node is also stored
 * in the NodeVector, so that previousNode() can easily be done.
 * @xsl.usage advanced
 */
public class UnionPathIterator extends LocPathIterator
        implements Cloneable, DTMIterator, java.io.Serializable, PathComponent
{
    static final long serialVersionUID = -3910351546843826781L;

  /**
   * Constructor to create an instance which you can add location paths to.
   */
  public UnionPathIterator()
  {

    super();

    // m_mutable = false;
    // m_cacheNodes = false;
    m_iterators = null;
    m_exprs = null;
  }

  /**
   * 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);

    try
    {
      if (null != m_exprs)
      {
        int n = m_exprs.length;
        DTMIterator newIters[] = new DTMIterator[n];
  
        for (int i = 0; i < n; i++)
        {
          DTMIterator iter = m_exprs[i].asIterator(m_execContext, context);
          newIters[i] = iter;
          iter.nextNode();
        }
        m_iterators = newIters;
      }
    }
    catch(Exception e)
    {
      throw new com.sun.org.apache.xml.internal.utils.WrappedRuntimeException(e);
    }
  }
  
  /**
   * Add an iterator to the union list.
   *
   * @param expr non-null reference to a location path iterator.
   */
  public void addIterator(DTMIterator expr)
  {

    // Increase array size by only 1 at a time.  Fix this
    // if it looks to be a problem.
    if (null == m_iterators)
    {
      m_iterators = new DTMIterator[1];
      m_iterators[0] = expr;
    }
    else
    {
      DTMIterator[] exprs = m_iterators;
      int len = m_iterators.length;

      m_iterators = new DTMIterator[len + 1];

      System.arraycopy(exprs, 0, m_iterators, 0, len);

      m_iterators[len] = expr;
    }
    expr.nextNode();
    if(expr instanceof Expression)
    	((Expression)expr).exprSetParent(this);
  }
  
  /**
   *  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 && null != m_iterators){         
                  int n = m_iterators.length;
                  for(int i = 0; i < n; i++)
                  {
                          m_iterators[i].detach();
                  }
                  m_iterators = null;                                
          }
  }


  /**
   * Create a UnionPathIterator object, including creation 
   * of location path iterators 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
   */
  public UnionPathIterator(Compiler compiler, int opPos)
          throws javax.xml.transform.TransformerException
  {

    super();

    opPos = compiler.getFirstChildPos(opPos);

    loadLocationPaths(compiler, opPos, 0);
  }
  
  /**
   * This will return an iterator capable of handling the union of paths given.
   * 
   * @param compiler The Compiler which is creating 
   * this expression.
   * @param opPos The position of this iterator in the 
   * opcode list from the compiler.
   * 
   * @return Object that is derived from LocPathIterator.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public static LocPathIterator createUnionIterator(Compiler compiler, int opPos)
          throws javax.xml.transform.TransformerException
  {
  	// For the moment, I'm going to first create a full UnionPathIterator, and 
  	// then see if I can reduce it to a UnionChildIterator.  It would obviously 
  	// be more effecient to just test for the conditions for a UnionChildIterator, 
  	// and then create that directly.
  	UnionPathIterator upi = new UnionPathIterator(compiler, opPos);
  	int nPaths = upi.m_exprs.length;
  	boolean isAllChildIterators = true;
  	for(int i = 0; i < nPaths; i++)
  	{
  		LocPathIterator lpi = upi.m_exprs[i];
  		
  		if(lpi.getAxis() != Axis.CHILD)
  		{
  			isAllChildIterators = false;
  			break;
  		}
  		else
  		{
  			// check for positional predicates or position function, which won't work.
  			if(HasPositionalPredChecker.check(lpi))
  			{
  				isAllChildIterators = false;
  				break;
  			}
  		}
  	}
  	if(isAllChildIterators)
  	{
  		UnionChildIterator uci = new UnionChildIterator();
  		
	  	for(int i = 0; i < nPaths; i++)
	  	{
	  		PredicatedNodeTest lpi = upi.m_exprs[i];
	  		// I could strip the lpi down to a pure PredicatedNodeTest, but 
	  		// I don't think it's worth it.  Note that the test can be used 
	  		// as a static object... so it doesn't have to be cloned.
	  		uci.addNodeTest(lpi);
	  	}
	  	return uci;
  		
  	}
  	else
  		return upi;
  }
  
  /** 
   * Get the analysis bits for this walker, as defined in the WalkerFactory.
   * @return One of WalkerFactory#BIT_DESCENDANT, etc.
   */
  public int getAnalysisBits()
  {
    int bits = 0;
    
    if (m_exprs != null)
    {
      int n = m_exprs.length;

      for (int i = 0; i < n; i++)
      {
      	int bit = m_exprs[i].getAnalysisBits();
        bits |= bit;
      }
    }

    return bits;
  }
  
  /**
   * Read the object from a serialization stream.
   *
   * @param stream Input stream to read from
   *
   * @throws java.io.IOException
   * @throws javax.xml.transform.TransformerException
   */
  private void readObject(java.io.ObjectInputStream stream)
          throws java.io.IOException, javax.xml.transform.TransformerException
  {
    try
    {
      stream.defaultReadObject();
      m_clones =  new IteratorPool(this);
    }
    catch (ClassNotFoundException cnfe)
    {
      throw new javax.xml.transform.TransformerException(cnfe);
    }
  }

  /**
   * Get a cloned LocPathIterator that holds the same 
   * position as this iterator.
   *
   * @return A clone of this iterator that holds the same node position.
   *
   * @throws CloneNotSupportedException
   */
  public Object clone() throws CloneNotSupportedException
  {

    UnionPathIterator clone = (UnionPathIterator) super.clone();
    if (m_iterators != null)
    {
      int n = m_iterators.length;
      
      clone.m_iterators = new DTMIterator[n];

      for (int i = 0; i < n; i++)
      {
        clone.m_iterators[i] = (DTMIterator)m_iterators[i].clone();
      }
    }