subscribemessage.java

pastry的java实现的2.0b版

/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

- Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

- Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.

- Neither  the name  of Rice  University (RICE) nor  the names  of its
contributors may be  used to endorse or promote  products derived from
this software without specific prior written permission.

This software is provided by RICE and the contributors on an "as is"
basis, without any representations or warranties of any kind, express
or implied including, but not limited to, representations or
warranties of non-infringement, merchantability or fitness for a
particular purpose. In no event shall RICE or contributors be liable
for any direct, indirect, incidental, special, exemplary, or
consequential damages (including, but not limited to, procurement of
substitute goods or services; loss of use, data, or profits; or
business interruption) however caused and on any theory of liability,
whether in contract, strict liability, or tort (including negligence
or otherwise) arising in any way out of the use of this software, even
if advised of the possibility of such damage.

********************************************************************************/

package rice.p2p.scribe.messaging;

import java.io.IOException;

import rice.*;
import rice.p2p.commonapi.*;
import rice.p2p.commonapi.rawserialization.*;
import rice.p2p.scribe.*;
import rice.p2p.scribe.rawserialization.*;

/**
 * @(#) SubscribeMessage.java The subscribe message.
 *
 * @version $Id: SubscribeMessage.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public class SubscribeMessage extends AnycastMessage {

  /**
   * The original subscriber
   */
  protected NodeHandle subscriber;

  /**
   * The previous parent
   */
  protected Id previousParent;

  /**
   * The id of this message
   */
  protected int id;
  /**
   * DESCRIBE THE FIELD
   */
  public final static short TYPE = 2;

  /**
   * Constructor which takes a unique integer Id
   *
   * @param source The source address
   * @param topic The topic
   * @param id The UID for this message
   * @param content The content
   */
  public SubscribeMessage(NodeHandle source, Topic topic, int id, RawScribeContent content) {
    this(source, topic, null, id, content);
  }

  /**
   * Constructor which takes a unique integer Id
   *
   * @param source The source address
   * @param topic The topic
   * @param id The UID for this message
   * @param content The content
   * @param previousParent The parent on this topic who died
   */
  public SubscribeMessage(NodeHandle source, Topic topic, Id previousParent, int id, RawScribeContent content) {
    super(source, topic, content);

    this.id = id;
    this.subscriber = source;
    this.previousParent = previousParent;
  }

  /**
   * Private because it should only be called from build(), if you need to
   * extend this, make sure to build a serializeHelper() like in
   * AnycastMessage/SubscribeMessage, and properly handle the version number.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @param contentDeserializer DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  private SubscribeMessage(InputBuffer buf, Endpoint endpoint, ScribeContentDeserializer contentDeserializer) throws IOException {
    super(buf, endpoint, contentDeserializer, false);
    id = buf.readInt();
    if (buf.readBoolean()) {
      previousParent = endpoint.readId(buf, buf.readShort());
    }
    subscriber = endpoint.readNodeHandle(buf);
  }

  /**
   * Returns the node who is trying to subscribe
   *
   * @return The node who is attempting to subscribe
   */
  public NodeHandle getSubscriber() {
    return subscriber;
  }

  /**
   * Returns the node who is trying to subscribe
   *
   * @return The node who is attempting to subscribe
   */
  public Id getPreviousParent() {
    return previousParent;
  }

  /**
   * Returns this subscribe lost message's id
   *
   * @return The id of this subscribe message
   */
  public int getId() {
    return id;
  }

  /**
   * Raw Serialization **************************************
   *
   * @return The Type value
   */
  public short getType() {
    return TYPE;
  }

  /**
   * Returns a String represneting this message
   *
   * @return A String of this message
   */
  public String toString() {
    return "[SubscribeMessage " + topic + " subscriber " + subscriber + " ID " + id + "]";
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    buf.writeByte((byte) 0);
    // version
    super.serializeHelper(buf);
    buf.writeInt(id);
    if (previousParent == null) {
      buf.writeBoolean(false);
    } else {
      buf.writeBoolean(true);
      buf.writeShort(previousParent.getType());
      previousParent.serialize(buf);
    }
    subscriber.serialize(buf);
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @param scd DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public static SubscribeMessage buildSM(InputBuffer buf, Endpoint endpoint, ScribeContentDeserializer scd) throws IOException {
    byte version = buf.readByte();
    switch (version) {
      case 0:
        return new SubscribeMessage(buf, endpoint, scd);
      default:
        throw new IOException("Unknown Version: " + version);
    }
  }

}