multiringnodehandle.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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This software is provided by RICE and the contributors on an "as is"
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********************************************************************************/

package rice.p2p.multiring;

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

import java.io.*;
import java.util.*;

/**
 * @(#) MultiringNodeHandle.java
 *
 * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
 * @author Alan Mislove
 */
public class MultiringNodeHandle extends NodeHandle implements Observer {

  /**
   * The internal handle
   */
  protected NodeHandle handle;

  /**
   * The handle's ringId
   */
  protected Id ringId;

  // serailver
  final static long serialVersionUID = -2972303779251779984L;

  /**
   * Constructor
   *
   * @param handle The handle to wrap
   * @param ringId The handle's ringId
   */
  public MultiringNodeHandle(Id ringId, NodeHandle handle) {
    this.handle = handle;
    this.ringId = ringId;

    handle.addObserver(this);
  }

  /**
   * Constructor for MultiringNodeHandle.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public MultiringNodeHandle(InputBuffer buf, Endpoint endpoint) throws IOException {
    ringId = endpoint.readId(buf, buf.readShort());
    handle = endpoint.readNodeHandle(buf);
    handle.addObserver(this);
  }

  /**
   * Returns the internal handle
   *
   * @return The internal handle
   */
  protected NodeHandle getHandle() {
    return handle;
  }

  /**
   * Returns the ringId of this node handle
   *
   * @return This node's ringId
   */
  public Id getRingId() {
    return ringId;
  }

  /**
   * Returns this node's id.
   *
   * @return The corresponding node's id.
   */
  public Id getId() {
    return RingId.build(ringId, handle.getId());
  }

  /**
   * Returns whether or not this node is currently alive
   *
   * @return Whether or not this node is currently alive
   */
  public boolean isAlive() {
    return handle.isAlive();
  }

  /**
   * Returns the current proximity value of this node
   *
   * @return The current proximity value of this node
   */
  public int proximity() {
    return handle.proximity();
  }

  /**
   * Observable callback. Simply rebroadcasts
   *
   * @param o the updated object
   * @param obj The paramter
   */
  public void update(Observable o, Object obj) {
    setChanged();
    notifyObservers(obj);
  }

  /**
   * Prints out the string
   *
   * @return A string
   */
  public String toString() {
    return "{MNH " + handle.toString() + "@" + ringId + "}";
  }

  /**
   * Returns whether or not this object is equal to the provided one
   *
   * @param o The object to compare to
   * @return Whether or not this is object is equal
   */
  public boolean equals(Object o) {
    if (!(o instanceof MultiringNodeHandle)) {
      return false;
    }

    return (((MultiringNodeHandle) o).handle.equals(handle) && ((MultiringNodeHandle) o).ringId.equals(ringId));
  }

  /**
   * Returns the hashCode
   *
   * @return hashCode
   */
  public int hashCode() {
    return (handle.hashCode() + ringId.hashCode());
  }

  /**
   * ReadObject overridden in order to maintain observer.
   *
   * @param ois The InputStream
   * @exception IOException DESCRIBE THE EXCEPTION
   * @exception ClassNotFoundException DESCRIBE THE EXCEPTION
   */
  private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
    ois.defaultReadObject();

    handle.addObserver(this);
  }

  /**
   * Requests that the underlying transport layer check to ensure that the
   * remote node is live. If the node is found to be live, nothing happens, but
   * if the node does not respond, the transport layer make take steps to
   * verfify that the node is dead. Such steps could include finding an
   * alteranate route to the node.
   *
   * @return Whether or not the node is currently alive
   */
  public boolean checkLiveness() {
    return handle.checkLiveness();
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    buf.writeShort(ringId.getType());
    ringId.serialize(buf);
    handle.serialize(buf);
  }
}