AckDatagram.java :  » JMS » UberMQ » com » ubermq » jms » common » datagram » impl » Java Open Source

package com.ubermq.jms.common.datagram.impl;


import com.ubermq.jms.common.datagram.*;
import com.ubermq.kernel.*;
import java.nio.*;

/**
 * An implementation of an ACK (acknowledgement) datagram.
 */
public class AckDatagram
    extends AbstractDatagram
    implements IAckDatagram
{
    private MessageId msgId;
    private boolean nack;
    
  /**
   * Constructs a general purpose ACK datagram that does not refer to
   * a message, that is either a success or failure ACK.
   * @param nack true if NACK, false otherwise.
   */
    AckDatagram(boolean nack)
  {
    super(DatagramFactory.DGRAM_ACK, 0);
    this.msgId = null;
    this.nack = nack;
  }
  
  /**
   * Constructs an ACK for a specific message.
   * @param msgId the message ID of the message that the datagram isreferring to.
   * @param nack true if NACK, false otherwise.
   */
    AckDatagram(MessageId msgId, boolean nack)
    {
    super(DatagramFactory.DGRAM_ACK, 0);
    this.msgId = msgId;
    this.nack = nack;
    }
  
  /**
   * No-arg constructor for reading datagrams from byte buffers.
   */
    public AckDatagram()
    {
    super(DatagramFactory.DGRAM_ACK, 0);
    }
    
    // ack-specific
    public MessageId getAckMessageId() {return msgId;}
    public boolean isNegativeAck() {return nack;}
    
    
    /**
   * the ACK datagram format is:
   *
   * <pre>
   * -------
   *  nack?       1    non-zero for true
   * -------
   *  msgId       12   optional, sender ID followed by sequence
   * -------
   * </pre>
   */
    public void incoming(java.nio.ByteBuffer bb)
    throws java.io.IOException
    {
    super.incoming(bb);
    setDatagramProps(DatagramFactory.DGRAM_ACK, 0);
    
    nack = (bb.get() != 0);
    if (bb.remaining() > 0) {
      msgId = new MessageId(bb.getLong(), bb.getInt());
    } else {
      msgId = null;
    }
    }
    
    /**
   * allows the datagram to be output to a channel.
   */
    public void outgoing(java.nio.ByteBuffer bb)
    {
    super.outgoing(bb);
    
    bb.put(nack ? (byte)0x1 : (byte)0x0);
    if (msgId != null) {
      bb.putLong(msgId.getSenderId());
      bb.putInt(msgId.getSequence());
    }
    }
    
    public String toString()
  {
    return super.toString() +
      "\nMsgID:\t\t" + msgId +
      "\nnack:\t\t" + nack;
    }
  
  public boolean equals(Object o)
  {
    if (o instanceof IAckDatagram) {
      IAckDatagram ad = (IAckDatagram)o;
      
      return ( ((ad.getAckMessageId() == null && getAckMessageId() == null) ||
              ad.getAckMessageId().equals(getAckMessageId())) &&
            ad.isNegativeAck() == isNegativeAck());
    } else {
      return false;
    }
  }
  
  public int hashCode() {
    int result = 17;
    result = 37*result + getAckMessageId().hashCode();
    result = 37*result + (isNegativeAck() ? 0 : 1);
    return result;
  }
}