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 package com.sun.grizzly.filter;

 import com.sun.grizzly.Context;

 import com.sun.grizzly.Controller;

 import com.sun.grizzly.ProtocolFilter;

 import com.sun.grizzly.util.OutputWriter;

 import com.sun.grizzly.util.WorkerThread;

 import java.io.IOException;

 import java.net.SocketAddress;

 import java.nio.ByteBuffer;

 import java.nio.channels.DatagramChannel;

 import java.nio.channels.SelectionKey;

 import java.util.logging.Level;

 /**

  * Simple ProtocolFilter implementation which write the available bytes

  * and delegate the processing to the next ProtocolFilter in the ProtocolChain.

  * If no bytes are available for write, no new ProtocolHandler will be a invoked and 

  * the connection (SelectionKey) will be cancelled. 

  *

  * @author Jeanfrancois Arcand

  */

 public class UDPWriteFilter implements ProtocolFilter{    

     public final static String UDP_SOCKETADDRESS = "socketAddress";

     public UDPWriteFilter(){

     }

     /**

      * Write available bytes and delegate the processing of them to the next

      * ProtocolFilter in the ProtocolChain.

      * @return <tt>true</tt> if the next ProtocolFilter on the ProtocolChain

      *                       need to bve invoked.

      */

     public boolean execute(Context ctx) throws IOException {

         boolean result = true;

         SocketAddress socketAddress = null;

         DatagramChannel datagramChannel = null;

         Exception exception = null;

         SelectionKey key = ctx.getSelectionKey();

         key.attach(null);

         ByteBuffer byteBuffer = 

                 ((WorkerThread)Thread.currentThread()).getByteBuffer();

         try {

             socketAddress = (SocketAddress)ctx.getAttribute(UDP_SOCKETADDRESS);

             if (socketAddress == null){

                 throw new IllegalStateException("socketAddress cannot be null");

             }

             datagramChannel = (DatagramChannel)key.channel();

             OutputWriter.flushChannel(datagramChannel,socketAddress,byteBuffer);   

         } catch (IOException ex) {

             exception = ex;

             log("UDPWriteFilter.execute",ex);

         } catch (RuntimeException ex) {

             exception = ex;    

             log("UDPWriteFilter.execute",ex);

         } finally {                               

             if (exception != null){

                 ctx.setAttribute(Context.THROWABLE,exception);

                 result = false;

             } else {

                 ctx.setKeyRegistrationState(

                         Context.KeyRegistrationState.REGISTER);    

             } 

         }       

         return result;

     }

     /**

      * Re-enable the SelectionKey and make sure the ByteBuffer has been cleared.

      * @return <tt>true</tt> if the previous ProtocolFilter postExecute method

      *         needs to be invoked.

      */

     public boolean postExecute(Context ctx) throws IOException {

         ctx.setKeyRegistrationState(Context.KeyRegistrationState.REGISTER);

         ((WorkerThread)Thread.currentThread()).getByteBuffer().clear();

         return true;

     }

     /**

      * Log a message/exception.

      * @param msg <code>String</code>

      * @param t <code>Throwable</code>

      */

     protected void log(String msg,Throwable t){

         if (Controller.logger().isLoggable(Level.FINE)){

             Controller.logger().log(Level.FINE,"Write,execute()",t);

         }

     } 

 }