locpathiterator.java

java1.6众多例子参考

  		return m_length;
  	
    // I'm a bit worried about this one, since it doesn't have the 
    // checks found above.  I suspect it's fine.  -sb
    if (m_foundLast)
  		return m_pos;
  		
    // Create a clone, and count from the current position to the end 
    // of the list, not taking into account the current predicate and 
    // predicates after the current one.
    int pos = (m_predicateIndex >= 0) ? getProximityPosition() : m_pos;
              
    LocPathIterator clone;

    try
    {
      clone = (LocPathIterator) clone();        
    }
    catch (CloneNotSupportedException cnse)
    {
      return -1;
    }

    // We want to clip off the last predicate, but only if we are a sub 
    // context node list, NOT if we are a context list.  See pos68 test, 
    // also test against bug4638.
    if (predCount > 0 && isPredicateTest)
    {
      // Don't call setPredicateCount, because it clones and is slower.
      clone.m_predCount = m_predicateIndex;
      // The line above used to be:
      // clone.m_predCount = predCount - 1;
      // ...which looks like a dumb bug to me. -sb
    }

    int next;

    while (DTM.NULL != (next = clone.nextNode()))
    {
      pos++;
    }
    
    if (isPredicateTest && m_predicateIndex < 1)
      m_length = pos;
    
    return pos;
  }

  /**
   * Tells if this NodeSetDTM is "fresh", in other words, if
   * the first nextNode() that is called will return the
   * first node in the set.
   *
   * @return true of nextNode has not been called.
   */
  public boolean isFresh()
  {
    return (m_pos == 0);
  }

  /**
   *  Returns the previous node in the set and moves the position of the
   * iterator backwards in the set.
   * @return  The previous <code>Node</code> in the set being iterated over,
   *   or<code>null</code> if there are no more members in that set.
   */
  public int previousNode()
  {
    throw new RuntimeException(
      XSLMessages.createXPATHMessage(XPATHErrorResources.ER_NODESETDTM_CANNOT_ITERATE, null)); //"This NodeSetDTM can not iterate to a previous node!");
  }

  /**
   * This attribute determines which node types are presented via the
   * iterator. The available set of constants is defined in the
   * <code>NodeFilter</code> interface.
   *
   * <p>This is somewhat useless at this time, since it doesn't
   * really return information that tells what this iterator will
   * show.  It is here only to fullfill the DOM NodeIterator
   * interface.</p>
   *
   * @return For now, always NodeFilter.SHOW_ALL & ~NodeFilter.SHOW_ENTITY_REFERENCE.
   * @see org.w3c.dom.traversal.NodeIterator
   */
  public int getWhatToShow()
  {

    // TODO: ??
    return DTMFilter.SHOW_ALL & ~DTMFilter.SHOW_ENTITY_REFERENCE;
  }

  /**
   *  The filter used to screen nodes.  Not used at this time,
   * this is here only to fullfill the DOM NodeIterator
   * interface.
   *
   * @return Always null.
   * @see org.w3c.dom.traversal.NodeIterator
   */
  public DTMFilter getFilter()
  {
    return null;
  }

  /**
   * The root node of the Iterator, as specified when it was created.
   *
   * @return The "root" of this iterator, which, in XPath terms,
   * is the node context for this iterator.
   */
  public int getRoot()
  {
    return m_context;
  }

  /**
   *  The value of this flag determines whether the children of entity
   * reference nodes are visible to the iterator. If false, they will be
   * skipped over.
   * <br> To produce a view of the document that has entity references
   * expanded and does not expose the entity reference node itself, use the
   * whatToShow flags to hide the entity reference node and set
   * expandEntityReferences to true when creating the iterator. To produce
   * a view of the document that has entity reference nodes but no entity
   * expansion, use the whatToShow flags to show the entity reference node
   * and set expandEntityReferences to false.
   *
   * @return Always true, since entity reference nodes are not
   * visible in the XPath model.
   */
  public boolean getExpandEntityReferences()
  {
    return true;
  }
  
  /** Control over whether it is OK for detach to reset the iterator. */
  protected boolean m_allowDetach = true;
  
  /**
   * Specify if it's OK for detach to release the iterator for reuse.
   * 
   * @param allowRelease true if it is OK for detach to release this iterator 
   * for pooling.
   */
  public void allowDetachToRelease(boolean allowRelease)
  {
    m_allowDetach = allowRelease;
  }

  /**
   *  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)
    {
      // sb: allow reusing of cached nodes when possible?
      // m_cachedNodes = null;
      m_execContext = null;
      // m_prefixResolver = null;  sb: Why would this ever want to be null?
      m_cdtm = null;
      m_length = -1;
      m_pos = 0;
      m_lastFetched = DTM.NULL;
      m_context = DTM.NULL;
      m_currentContextNode = DTM.NULL;
      
      m_clones.freeInstance(this);
    }
  }
  
  /**
   * Reset the iterator.
   */
  public void reset()
  {
  	assertion(false, "This iterator can not reset!");
  }

  /**
   * 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
  {
    LocPathIterator clone;
//    clone = (LocPathIterator) clone();
    clone = (LocPathIterator)m_clones.getInstanceOrThrow();
    clone.m_execContext = m_execContext;
    clone.m_cdtm = m_cdtm;
    
    clone.m_context = m_context;
    clone.m_currentContextNode = m_currentContextNode;
    clone.m_stackFrame = m_stackFrame;

    // clone.reset();

    return clone;
  }

//  /**
//   * 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
//  {
//
//    LocPathIterator clone = (LocPathIterator) super.clone();
//
//    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.
   */
  public abstract int nextNode();

  /**
   * Bottleneck the return of a next node, to make returns
   * easier from nextNode().
   *
   * @param nextNode The next node found, may be null.
   *
   * @return The same node that was passed as an argument.
   */
  protected int returnNextNode(int nextNode)
  {

    if (DTM.NULL != nextNode)
    {
      m_pos++;
    }

    m_lastFetched = nextNode;

    if (DTM.NULL == nextNode)
      m_foundLast = true;

    return nextNode;
  }

  /**
   * Return the last fetched node.  Needed to support the UnionPathIterator.
   *
   * @return The last fetched node, or null if the last fetch was null.
   */
  public int getCurrentNode()
  {
    return m_lastFetched;
  }

  /**
   * If an index is requested, NodeSetDTM will call this method
   * to run the iterator to the index.  By default this sets
   * m_next to the index.  If the index argument is -1, this
   * signals that the iterator should be run to the end.
   *
   * @param index The index to run to, or -1 if the iterator
   * should run to the end.
   */
  public void runTo(int index)
  {

    if (m_foundLast || ((index >= 0) && (index <= getCurrentPos())))
      return;

    int n;

    if (-1 == index)
    {
      while (DTM.NULL != (n = nextNode()));
    }
    else
    {
      while (DTM.NULL != (n = nextNode()))
      {
        if (getCurrentPos() >= index)
          break;
      }
    }
  }

  /**
   * Tells if we've found the last node yet.
   *
   * @return true if the last nextNode returned null.
   */
  public final boolean getFoundLast()
  {
    return m_foundLast;
  }

  /**
   * The XPath execution context we are operating on.
   *
   * @return XPath execution context this iterator is operating on,
   * or null if setRoot has not been called.
   */
  public final XPathContext getXPathContext()
  {
    return m_execContext;
  }

  /**
   * The node context for the iterator.
   *
   * @return The node context, same as getRoot().
   */
  public final int getContext()
  {
    return m_context;
  }

  /**
   * The node context from where the expression is being
   * executed from (i.e. for current() support).
   *
   * @return The top-level node context of the entire expression.
   */
  public final int getCurrentContextNode()
  {
    return m_currentContextNode;
  }

  /**
   * Set the current context node for this iterator.
   *
   * @param n Must be a non-null reference to the node context.
   */
  public final void setCurrentContextNode(int n)
  {
    m_currentContextNode = n;
  }
  
//  /**
//   * Set the current context node for this iterator.
//   *
//   * @param n Must be a non-null reference to the node context.
//   */
//  public void setRoot(int n)
//  {
//    m_context = n;
//    m_cdtm = m_execContext.getDTM(n);
//  }

  /**
   * Return the saved reference to the prefix resolver that
   * was in effect when this iterator was created.
   *
   * @return The prefix resolver or this iterator, which may be null.
   */
  public final PrefixResolver getPrefixResolver()
  {
  	if(null == m_prefixResolver)
  	{
    	m_prefixResolver = (PrefixResolver)getExpressionOwner();
  	}

    return m_prefixResolver;
  }
        
//  /**
//   * Get the analysis pattern built by the WalkerFactory.
//   *
//   * @return The analysis pattern built by the WalkerFactory.
//   */
//  int getAnalysis()
//  {
//    return m_analysis;
//  }

//  /**
//   * Set the analysis pattern built by the WalkerFactory.
//   *
//   * @param a The analysis pattern built by the WalkerFactory.
//   */
//  void setAnalysis(int a)
//  {
//    m_analysis = a;
//  }

  /**
   * @see com.sun.org.apache.xpath.internal.XPathVisitable#callVisitors(ExpressionOwner, XPathVisitor)
   */
  public void callVisitors(ExpressionOwner owner, XPathVisitor visitor)
  {
  	 	if(visitor.visitLocationPath(owner, this))
  	 	{
  	 		visitor.visitStep(owner, this);
  	 		callPredicateVisitors(visitor);
  	 	}
  }  

  
  //============= State Data =============
  
  /** 
   * The pool for cloned iterators.  Iterators need to be cloned
   * because the hold running state, and thus the original iterator
   * expression from the stylesheet pool can not be used.          
   */
  transient protected IteratorPool m_clones = new IteratorPool(this);
  
  /** 
   * The dtm of the context node.  Careful about using this... it may not 
   * be the dtm of the current node.
   */
  transient protected DTM m_cdtm;
  
  /**
   * The stack frame index for this iterator.
   */
  transient int m_stackFrame = -1;

  /**
   * Value determined at compile time, indicates that this is an
   * iterator at the top level of the expression, rather than inside
   * a predicate.
   * @serial
   */
  private boolean m_isTopLevel = false;

  /** The last node that was fetched, usually by nextNode. */
  transient public int m_lastFetched = DTM.NULL;

  /**
   * The context node for this iterator, which doesn't change through
   * the course of the iteration.
   */
  transient protected int m_context = DTM.NULL;

  /**
   * The node context from where the expression is being
   * executed from (i.e. for current() support).  Different
   * from m_context in that this is the context for the entire
   * expression, rather than the context for the subexpression.
   */
  transient protected int m_currentContextNode = DTM.NULL;
  
  /**
   * The current position of the context node.
   */
  transient protected int m_pos = 0;
  
  transient protected int m_length = -1;

  /**
   * Fast access to the current prefix resolver.  It isn't really
   * clear that this is needed.
   * @serial
   */
  private PrefixResolver m_prefixResolver;

  /**
   * The XPathContext reference, needed for execution of many
   * operations.
   */
  transient protected XPathContext m_execContext;
  
  /**
   * Returns true if all the nodes in the iteration well be returned in document 
   * order.
   * 
   * @return true as a default.
   */
  public boolean isDocOrdered()
  {
    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()
  {
    return -1;
  }


//  /**
//   * The analysis pattern built by the WalkerFactory.
//   * TODO: Move to LocPathIterator.
//   * @see com.sun.org.apache.xpath.internal.axes.WalkerFactory
//   * @serial
//   */
//  protected int m_analysis = 0x00000000;
  /**
   * @see PredicatedNodeTest#getLastPos(XPathContext)
   */
  public int getLastPos(XPathContext xctxt)
  {
    return getLength();
  }

}