lookupmessage.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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- Redistributions of source code must retain the above copyright
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- Redistributions in binary form must reproduce the above copyright
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- Neither  the name  of Rice  University (RICE) nor  the names  of its
contributors may be  used to endorse or promote  products derived from
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This software is provided by RICE and the contributors on an "as is"
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********************************************************************************/

package rice.p2p.past.messaging;

import java.io.IOException;

import rice.*;
import rice.p2p.commonapi.*;
import rice.p2p.commonapi.rawserialization.*;
import rice.p2p.past.*;
import rice.p2p.past.gc.GCId;
import rice.p2p.past.rawserialization.*;

/**
 * @(#) LookupMessage.java This class is the representation of a lookup request
 * (by Id) in Past. response should be PastContent
 *
 * @version $Id: LookupMessage.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 * @author Ansley Post
 * @author Peter Druschel
 */
public class LookupMessage extends ContinuationMessage {

  // the id to fetch
  private Id id;

  // whether or not this message has been cached
  private boolean cached = false;

  // the list of nodes where this message has been
  private NodeHandle handle;
  /**
   * DESCRIBE THE FIELD
   */
  public final static short TYPE = 6;

  /**
   * Constructor
   *
   * @param uid The unique id
   * @param id The location to be stored
   * @param source The source address
   * @param dest The destination address
   */
  public LookupMessage(int uid, Id id, NodeHandle source, Id dest) {
    super(uid, source, dest);

    this.id = id;
  }

  /**
   * Constructor for LookupMessage.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @param pcd DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  private LookupMessage(InputBuffer buf, Endpoint endpoint, PastContentDeserializer pcd) throws IOException {
    super(buf, endpoint);
    if (serType == S_SUB) {
      short contentType = buf.readShort();
      response = pcd.deserializePastContent(buf, endpoint, contentType);
    }
    if (buf.readBoolean()) {
      handle = endpoint.readNodeHandle(buf);
    }
    try {
      id = endpoint.readId(buf, buf.readShort());
    } catch (IllegalArgumentException iae) {
      System.out.println(iae + " " + this + " serType:" + serType + " UID:" + getUID() + " d:" + dest + " s:" + source);
      throw iae;
    }
    cached = buf.readBoolean();
  }

  /**
   * Method which returns the id
   *
   * @return The contained id
   */
  public Id getId() {
    return id;
  }

  /**
   * Returns whether or not this message has been cached
   *
   * @return Whether or not this message has been cached
   */
  public boolean isCached() {
    return cached;
  }

  /**
   * Method which returns the previous hop (where the message was just at)
   *
   * @return The previous hop
   */
  public NodeHandle getPreviousNodeHandle() {
    return handle;
  }

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

  /**
   * Sets this message as having been cached.
   */
  public void setCached() {
    cached = true;
  }

  /**
   * Method which is designed to be overridden by subclasses if they need to
   * keep track of where they've been.
   *
   * @param handle The current local handle
   */
  public void addHop(NodeHandle handle) {
    this.handle = handle;
  }

  /**
   * Returns a string representation of this message
   *
   * @return A string representing this message
   */
  public String toString() {
    return "[LookupMessage for " + id + " data " + response + "]";
  }

  /**
   * 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
    if (response != null && response instanceof RawPastContent) {
      super.serialize(buf, false);
      RawPastContent rpc = (RawPastContent) response;
      buf.writeShort(rpc.getType());
      rpc.serialize(buf);
    } else {
      super.serialize(buf, true);
    }

    buf.writeBoolean(handle != null);
    if (handle != null) {
      handle.serialize(buf);
    }

    buf.writeShort(id.getType());
    id.serialize(buf);
    buf.writeBoolean(cached);
  }

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