code: package com.sun.xml.xsom.impl.parser.state;
  
  import org.xml.sax.Attributes;
  import org.xml.sax.SAXException;
  
  /**
   * Dispatches incoming events into sub handlers appropriately
   * so that the interleaving semantics will be correctly realized.
   * 
   * @author Kohsuke Kawaguchi (kk@kohsuke.org)
   */
  public abstract class NGCCInterleaveFilter implements NGCCEventSource, NGCCEventReceiver {
      protected NGCCInterleaveFilter( NGCCHandler parent, int cookie ) {
          this._parent = parent;
          this._cookie = cookie;
      }
      
      protected void setHandlers( NGCCEventReceiver[] receivers ) {
          this._receivers = receivers;
      }
      
      /** event receiverse. */
      protected NGCCEventReceiver[] _receivers;
      
      public int replace(NGCCEventReceiver oldHandler, NGCCEventReceiver newHandler) {
          for( int i=0; i<_receivers.length; i++ )
              if( _receivers[i]==oldHandler ) {
                  _receivers[i]=newHandler;
                  return i;
              }
          throw new InternalError(); // a bug in RelaxNGCC.
      }
  
  
      /** Parent handler. */
      private final NGCCHandler _parent;
      /** Cookie given by the parent. */
      private final int _cookie;
  
  
  
  //
  //
  // event handler
  //
  //
      /**
       * Receiver that is being locked and therefore receives all the events.
       * <pre><xmp>
       * <interleave>
       *   <element name="foo"/>
       *   <element name="bar">
       *     <element name="foo"/>
       *   </element>
       * </interlaeve>
       * </xmp></pre>
       * When processing inside the bar element, this receiver is
       * "locked" so that it can correctly receive its child foo element.
       */
      private int lockedReceiver;
      /**
       * Nest level. Lock will be release when the lockCount becomes 0.
       */
      private int lockCount=0;
      
      public void enterElement(
          String uri, String localName, String qname,Attributes atts) throws SAXException {
          
          if(isJoining)   return; // ignore any token if we are joining. See joinByXXXX.
          
          if(lockCount++==0) {
              lockedReceiver = findReceiverOfElement(uri,localName);
              if(lockedReceiver==-1) {
                  // we can't process this token. join.
                  joinByEnterElement(null,uri,localName,qname,atts);
                  return;
              }
          }
          
          _receivers[lockedReceiver].enterElement(uri,localName,qname,atts);
      }
      public void leaveElement(String uri, String localName, String qname) throws SAXException {
          if(isJoining)   return; // ignore any token if we are joining. See joinByXXXX.
  
          if( lockCount-- == 0 )
              joinByLeaveElement(null,uri,localName,qname);
          else
              _receivers[lockedReceiver].leaveElement(uri,localName,qname);
      }
      public void enterAttribute(String uri, String localName, String qname) throws SAXException {
          if(isJoining)   return; // ignore any token if we are joining. See joinByXXXX.
          
          if(lockCount++==0) {
              lockedReceiver = findReceiverOfAttribute(uri,localName);
              if(lockedReceiver==-1) {
                  // we can't process this token. join.
                  joinByEnterAttribute(null,uri,localName,qname);
                  return;
              }
          }
                  
          _receivers[lockedReceiver].enterAttribute(uri,localName,qname);
      }
      public void leaveAttribute(String uri, String localName, String qname) throws SAXException {
          if(isJoining)   return; // ignore any token if we are joining. See joinByXXXX.
          
          if( lockCount-- == 0 )
              joinByLeaveAttribute(null,uri,localName,qname);
          else
              _receivers[lockedReceiver].leaveAttribute(uri,localName,qname);
      }
      public void text(String value) throws SAXException {
          if(isJoining)   return; // ignore any token if we are joining. See joinByXXXX.
          
          if(lockCount!=0)
              _receivers[lockedReceiver].text(value);
          else {
              int receiver = findReceiverOfText();
              if(receiver!=-1)    _receivers[receiver].text(value);
              else                joinByText(null,value);
          }
      }
  
  
  
      /**
       * Implemented by the generated code to determine the handler
       * that can receive the given element.
       * 
       * @return
       *      Thread ID of the receiver that can handle this event,
       *      or -1 if none.
       */
      protected abstract int findReceiverOfElement( String uri, String local );
      
      /**
       * Returns the handler that can receive the given attribute, or null.
       */
      protected abstract int findReceiverOfAttribute( String uri, String local );
      
      /**
       * Returns the handler that can receive text events, or null.
       */
      protected abstract int findReceiverOfText();
  
  
  
  
  //
  //
  // join method
  //
  //
  
      
      /**
       * Set to true when this handler is in the process of
       * joining all branches.
       */
      private boolean isJoining = false;
  
      /**
       * Joins all the child receivers.
       * 
       * <p>
       * This method is called by a child receiver when it sees
       * something that it cannot handle, or by this object itself
       * when it sees an event that it can't process.
       * 
       * <p>
       * This method forces children to move to its final state,
       * then revert to the parent.
       * 
       * @param source
       *      If this method is called by one of the child receivers,
       *      the receiver object. If this method is called by itself,
       *      null.
       */
      public void joinByEnterElement( NGCCEventReceiver source,
          String uri, String local, String qname, Attributes atts ) throws SAXException {
          
          if(isJoining)   return; // we are already in the process of joining. ignore.
          isJoining = true;
  
          // send special token to the rest of the branches.
          // these branches don't understand this token, so they will
          // try to move to a final state and send the token back to us,
          // which this object will ignore (because isJoining==true)
          // Otherwise branches will find an error.
          for( int i=0; i<_receivers.length; i++ )
              if( _receivers[i]!=source )
                  _receivers[i].enterElement(uri,local,qname,atts);
          
          // revert to the parent
          _parent._source.replace(this,_parent);
          _parent.onChildCompleted(null,_cookie,true);
          // send this event to the parent
          _parent.enterElement(uri,local,qname,atts);
      }
      
      public void joinByLeaveElement( NGCCEventReceiver source,
          String uri, String local, String qname ) throws SAXException {
          
          if(isJoining)   return; // we are already in the process of joining. ignore.
          isJoining = true;
  
          // send special token to the rest of the branches.
          // these branches don't understand this token, so they will
          // try to move to a final state and send the token back to us,
          // which this object will ignore (because isJoining==true)
          // Otherwise branches will find an error.
          for( int i=0; i<_receivers.length; i++ )
              if( _receivers[i]!=source )
                  _receivers[i].leaveElement(uri,local,qname);
          
          // revert to the parent
          _parent._source.replace(this,_parent);
          _parent.onChildCompleted(null,_cookie,true);
          // send this event to the parent
          _parent.leaveElement(uri,local,qname);
      }
      
      public void joinByEnterAttribute( NGCCEventReceiver source,
          String uri, String local, String qname ) throws SAXException {
          
          if(isJoining)   return; // we are already in the process of joining. ignore.
          isJoining = true;
  
          // send special token to the rest of the branches.
          // these branches don't understand this token, so they will
          // try to move to a final state and send the token back to us,
          // which this object will ignore (because isJoining==true)
          // Otherwise branches will find an error.
          for( int i=0; i<_receivers.length; i++ )
              if( _receivers[i]!=source )
                  _receivers[i].enterAttribute(uri,local,qname);
          
          // revert to the parent
          _parent._source.replace(this,_parent);
          _parent.onChildCompleted(null,_cookie,true);
          // send this event to the parent
          _parent.enterAttribute(uri,local,qname);
      }
      
      public void joinByLeaveAttribute( NGCCEventReceiver source,
          String uri, String local, String qname ) throws SAXException {
          
          if(isJoining)   return; // we are already in the process of joining. ignore.
          isJoining = true;
  
          // send special token to the rest of the branches.
          // these branches don't understand this token, so they will
          // try to move to a final state and send the token back to us,
          // which this object will ignore (because isJoining==true)
          // Otherwise branches will find an error.
          for( int i=0; i<_receivers.length; i++ )
              if( _receivers[i]!=source )
                  _receivers[i].leaveAttribute(uri,local,qname);
          
          // revert to the parent
          _parent._source.replace(this,_parent);
          _parent.onChildCompleted(null,_cookie,true);
          // send this event to the parent
          _parent.leaveAttribute(uri,local,qname);
      }
      
      public void joinByText( NGCCEventReceiver source,
          String value ) throws SAXException {
  
          if(isJoining)   return; // we are already in the process of joining. ignore.
          isJoining = true;
          
          // send special token to the rest of the branches.
          // these branches don't understand this token, so they will
          // try to move to a final state and send the token back to us,
          // which this object will ignore (because isJoining==true)
          // Otherwise branches will find an error.
          for( int i=0; i<_receivers.length; i++ )
              if( _receivers[i]!=source )
                  _receivers[i].text(value);
  
          // revert to the parent
          _parent._source.replace(this,_parent);
          _parent.onChildCompleted(null,_cookie,true);
          // send this event to the parent
          _parent.text(value);
      }
  
  
  
  //
  //
  // event dispatching methods
  //
  //
      
      public void sendEnterAttribute( int threadId,
          String uri, String local, String qname) throws SAXException {
          
          _receivers[threadId].enterAttribute(uri,local,qname);
      }
  
      public void sendEnterElement( int threadId,
          String uri, String local, String qname, Attributes atts) throws SAXException {
          
          _receivers[threadId].enterElement(uri,local,qname,atts);
      }
  
      public void sendLeaveAttribute( int threadId,
          String uri, String local, String qname) throws SAXException {
          
          _receivers[threadId].leaveAttribute(uri,local,qname);
      }
  
      public void sendLeaveElement( int threadId,
          String uri, String local, String qname) throws SAXException {
          
          _receivers[threadId].leaveElement(uri,local,qname);
      }
  
      public void sendText(int threadId, String value) throws SAXException {
          _receivers[threadId].text(value);
      }
  
  }
  