scribemessage.java

pastry的java实现的2.0b版

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

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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package rice.p2p.scribe.messaging;

import java.io.IOException;

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

/**
 * @(#) ScribeMessage.java This class the abstraction of a message used
 * internally by Scribe.
 *
 * @version $Id: ScribeMessage.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public abstract class ScribeMessage implements RawMessage {

  // the source of this message
  /**
   * DESCRIBE THE FIELD
   */
  protected NodeHandle source;

  // the topic of this message
  /**
   * DESCRIBE THE FIELD
   */
  protected Topic topic;

  // serialver for backward compatibility
  private final static long serialVersionUID = 4593674882226544604L;

  /**
   * Constructor which takes a unique integer Id
   *
   * @param source The source address
   * @param topic The topic
   */
  protected ScribeMessage(NodeHandle source, Topic topic) {
    this.source = source;
    this.topic = topic;
  }

  /**
   * Protected because it should only be called from an extending class, to get
   * version numbers correct.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  protected ScribeMessage(InputBuffer buf, Endpoint endpoint) throws IOException {
    source = endpoint.readNodeHandle(buf);
    topic = new Topic(buf, endpoint);
  }

  /**
   * Method which should return the priority level of this message. The messages
   * can range in priority from 0 (highest priority) to Integer.MAX_VALUE
   * (lowest) - when sending messages across the wire, the queue is sorted by
   * message priority. If the queue reaches its limit, the lowest priority
   * messages are discarded. Thus, applications which are very verbose should
   * have LOW_PRIORITY or lower, and applications which are somewhat quiet are
   * allowed to have MEDIUM_PRIORITY or possibly even HIGH_PRIORITY.
   *
   * @return This message's priority
   */
  public byte getPriority() {
    return MEDIUM_HIGH_PRIORITY;
  }

  /**
   * Method which returns this messages' source address
   *
   * @return The source of this message
   */
  public NodeHandle getSource() {
    return source;
  }

  /**
   * Method which returns this messages' topic
   *
   * @return The topic of this message
   */
  public Topic getTopic() {
    return topic;
  }

  /**
   * Method which set this messages' source address
   *
   * @param source The source of this message
   */
  public void setSource(NodeHandle source) {
    this.source = source;
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    source.serialize(buf);
    topic.serialize(buf);
  }

}