routeset.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"
basis, without any representations or warranties of any kind, express
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********************************************************************************/
package rice.pastry.routing;

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

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

/**
 * A set of nodes typically stored in the routing table. The set contains a
 * bounded number of the closest node handles. Since proximity value can change
 * unpredictably, we don't keep the set in sorted order.
 *
 * @version $Id: RouteSet.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Andrew Ladd
 * @author Peter Druschel
 */

public class RouteSet implements NodeSetI, Serializable,
  Observer {

  private NodeHandle[] nodes;

  private int theSize;

  private int closest;

  transient RoutingTable observer;
  /**
   * DESCRIBE THE FIELD
   */
  public final static short TYPE = 2;

  private final static long serialVersionUID = 8156336294555109590L;

  /**
   * Constructor.
   *
   * @param maxSize the maximum number of nodes that fit in this set.
   */

  public RouteSet(int maxSize) {
    nodes = new NodeHandle[maxSize];
    theSize = 0;
    closest = -1;
  }

  /**
   * Constructor for RouteSet.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param nhf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public RouteSet(InputBuffer buf, NodeHandleFactory nhf) throws IOException {
    byte maxSize = buf.readByte();
    theSize = buf.readByte();
    closest = buf.readByte();
    nodes = new NodeHandle[maxSize];
    for (int i = 0; i < theSize; i++) {
      nodes[i] = nhf.readNodeHandle(buf);
    }
  }

  /**
   * Returns the node in the ith position in the set.
   *
   * @param i DESCRIBE THE PARAMETER
   * @return the ith node.
   */
  public NodeHandle get(int i) {
    if (i < 0 || i >= theSize) {
      throw new NoSuchElementException();
    }

    return nodes[i];
  }

  /**
   * Returns the node handle with the matching node id or null if none exists.
   *
   * @param nid the node id.
   * @return the node handle.
   */
  public NodeHandle get(Id nid) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].getNodeId().equals(nid)) {
        return nodes[i];
      }
    }

    return null;
  }

  /**
   * Get the index of the node id.
   *
   * @param nid DESCRIBE THE PARAMETER
   * @return the node.
   */
  public int getIndex(Id nid) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].getNodeId().equals(nid)) {
        return i;
      }
    }

    return -1;
  }

  /**
   * Get the index of the node id.
   *
   * @param nh DESCRIBE THE PARAMETER
   * @return the node.
   */
  public int getIndex(NodeHandle nh) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].equals(nh)) {
        return i;
      }
    }

    return -1;
  }

  /**
   * Finds the NodeHandle associated with the Id.
   *
   * @param id a node id.
   * @return the handle associated with that id or null if no such handle is
   *      found.
   */
  public rice.p2p.commonapi.NodeHandle getHandle(rice.p2p.commonapi.Id id) {
    return getHandle((Id) id);
  }

  /**
   * Gets the ith element in the set.
   *
   * @param i an index.
   * @return the handle associated with that id or null if no such handle is
   *      found.
   */
  public rice.p2p.commonapi.NodeHandle getHandle(int i) {
    return get(i);
  }

  /**
   * Gets the index of the element with the given node id.
   *
   * @param id the id.
   * @return the index or throws a NoSuchElementException.
   * @exception NoSuchElementException DESCRIBE THE EXCEPTION
   */
  public int getIndexHandle(rice.p2p.commonapi.Id id)
     throws NoSuchElementException {
    return getIndex((Id) id);
  }

  /**
   * Gets the Type attribute of the RouteSet object
   *
   * @return The Type value
   */
  public short getType() {
    return TYPE;
  }

  /**
   * Sets the RoutingTable attribute of the RouteSet object
   *
   * @param rt The new RoutingTable value
   */
  public void setRoutingTable(RoutingTable rt) {
    observer = rt;
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public String toString() {
    String s = "RS: ";
    for (int i = 0; i < nodes.length; i++) {
      s += nodes[i] + ",";
    }
    return s;
  }

  /**
   * Puts a node into the set. The insertion succeeds either if the set is below
   * is maximal size or if the handle is closer than the most distant member in
   * the set.
   *
   * @param handle the handle to put.
   * @return true if the put succeeded, false otherwise.
   */
  public boolean put(NodeHandle handle) {
    int worstIndex = -1;
    int worstProximity = Integer.MIN_VALUE;

    // scan entries
    for (int i = 0; i < theSize; i++) {

      // if handle is already in the set, abort
      if (nodes[i].equals(handle)) {
        return false;
      }

      // find entry with worst proximity
      int p = nodes[i].proximity();
      if (p >= worstProximity) {
        worstProximity = p;
        worstIndex = i;
      }
    }

    if (theSize < nodes.length) {
      nodes[theSize++] = handle;

//      setChanged();
      notifyTable(handle, true);

      // ping handles while the set is not full
      handle.ping();
      handle.addObserver(this);

      return true;
    } else {
      if (handle.proximity() == Integer.MAX_VALUE) {
        // wait until the proximity value is available

        handle.ping();
        // XXX - eventually, should only ping handles pinged from
        // the deserializer
        handle.addObserver(this);

        return false;
      } else if (handle.proximity() < worstProximity) {
        // remove handle with worst proximity
//        setChanged();
        notifyTable(nodes[worstIndex], false);

        // in case we observe this handle, stop doing so
        nodes[worstIndex].deleteObserver(this);

        // insert new handle
        nodes[worstIndex] = handle;

//        setChanged();
        notifyTable(handle, true);
        handle.addObserver(this);

        return true;
      } else {
        return false;
      }
    }
  }

  /**
   * Is called by the Observer pattern whenever the liveness or proximity of a
   * registered node handle is changed.
   *
   * @param o The node handle
   * @param arg the event type (PROXIMITY_CHANGE, DECLARED_LIVE, DECLARED_DEAD)
   */
  public void update(Observable o, Object arg) {
    // if the proximity is initialized for the time, insert the handle
    if (((Integer) arg) == NodeHandle.PROXIMITY_CHANGED) {
      put((NodeHandle) o);
    } else if (((Integer) arg) == NodeHandle.DECLARED_DEAD) {
      // changed to remove dead handles - AM
      remove((NodeHandle) o);
    }
  }

  /**
   * Removes a node from a set.
   *
   * @param nid the node id to remove.
   * @return the removed handle or null.
   */
  public NodeHandle remove(Id nid) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].getNodeId().equals(nid)) {
        NodeHandle handle = nodes[i];

        nodes[i] = nodes[--theSize];

        notifyTable(handle, false);

        // in case we observe this handle, stop doing so
        handle.deleteObserver(this);

        return handle;
      }
    }

    return null;
  }

  /**
   * Removes a node from a set.
   *
   * @param nh DESCRIBE THE PARAMETER
   * @return the removed handle or null.
   */
  public NodeHandle remove(NodeHandle nh) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].equals(nh)) {
        NodeHandle handle = nodes[i];

        nodes[i] = nodes[--theSize];

        notifyTable(handle, false);

        // in case we observe this handle, stop doing so
        handle.deleteObserver(this);

        return handle;
      }
    }

    return null;
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param handle DESCRIBE THE PARAMETER
   * @param added DESCRIBE THE PARAMETER
   */
  private void notifyTable(NodeHandle handle, boolean added) {
    if (observer != null) {
      observer.nodeSetUpdate(null, handle, added);
    }
  }

  /**
   * Membership test.
   *
   * @param nh DESCRIBE THE PARAMETER
   * @return true if it is a member, false otherwise.
   */
  public boolean member(NodeHandle nh) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].equals(nh)) {
        return true;
      }
    }

    return false;
  }

  /**
   * Membership test.
   *
   * @param nid the node id to membership of.
   * @return true if it is a member, false otherwise.
   */
  public boolean member(Id nid) {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].getNodeId().equals(nid)) {
        return true;
      }
    }

    return false;
  }

  /**
   * Return the current size of the set.
   *
   * @return the size.
   */
  public int size() {
    return theSize;
  }

  /**
   * Pings all new nodes in the RouteSet. No longer- Called from
   * RouteMaintenance.
   */
  public void pingAllNew() {
    for (int i = 0; i < theSize; i++) {
      if (nodes[i].proximity() == Integer.MAX_VALUE) {
        nodes[i].ping();
      }
    }
  }

  /**
   * Return the closest live node in the set.
   *
   * @return the closest node, or null if no live node exists in the set.
   */
  public NodeHandle closestNode() {
    return closestNode(NodeHandle.LIVENESS_SUSPECTED);
  }

  /**
   * Return the closest live node in the set.
   *
   * @param minLiveness DESCRIBE THE PARAMETER
   * @return the closest node, or null if no live node exists in the set.
   */
  public NodeHandle closestNode(int minLiveness) {
    int bestProximity = Integer.MAX_VALUE;
    NodeHandle bestNode = null;

    for (int i = 0; i < theSize; i++) {
      if (nodes[i].getLiveness() > minLiveness) {
        continue;
      }

      int p = nodes[i].proximity();
      if (p <= bestProximity) {
        bestProximity = p;
        bestNode = nodes[i];
        closest = i;
      }
    }

    // If a backup node handle bubbles up to the top, ping it.
    if (bestNode != null && bestProximity == Integer.MAX_VALUE) {
      bestNode.ping();
    }

    return bestNode;
  }

  /**
   * deserialize the routeSet pings the handle the was the closests on the
   * sending node
   *
   * @param in DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   * @exception ClassNotFoundException DESCRIBE THE EXCEPTION
   */
  private void readObject(ObjectInputStream in) throws IOException,
    ClassNotFoundException {
    nodes = (NodeHandle[]) in.readObject();
    theSize = in.readInt();
    closest = in.readInt();
    if (closest != -1) {
      nodes[closest].ping();
    }
    closest = -1;
  }

  /**
   * serialize the RouteSet records the closest node
   *
   * @param out DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   * @exception ClassNotFoundException DESCRIBE THE EXCEPTION
   */
  private void writeObject(ObjectOutputStream out) throws IOException,
    ClassNotFoundException {
    if (closest == -1) {
      closestNode();
    }

    // here, we don't want to advetise nodes which are dead, so we filter
    // our list based on only live nodes
    NodeHandle[] tmp = new NodeHandle[nodes.length];

    int j = 0;
    for (int i = 0; i < tmp.length; i++) {
      if ((nodes[i] != null) && (nodes[i].isAlive())) {
        tmp[j] = nodes[i];
        j++;
      }
    }

    out.writeObject(tmp);
    out.writeInt(j);

    int closest = -1;
    for (int i = 0; i < j; i++) {
      if ((closest == -1) || (tmp[i].proximity() < tmp[closest].proximity())) {
        closest = i;
      }
    }

    out.writeInt(closest);
  }

  // Common API Support

  /**
   * Puts a NodeHandle into the set.
   *
   * @param handle the handle to put.
   * @return true if the put succeeded, false otherwise.
   */
  public boolean putHandle(rice.p2p.commonapi.NodeHandle handle) {
    return put((NodeHandle) handle);
  }

  /**
   * Verifies if the set contains this particular id.
   *
   * @param id a node id.
   * @return true if that node id is in the set, false otherwise.
   */
  public boolean memberHandle(rice.p2p.commonapi.Id id) {
    return member((Id) id);
  }

  /**
   * Removes a node id and its handle from the set.
   *
   * @param id DESCRIBE THE PARAMETER
   * @return the node handle removed or null if nothing.
   */
  public rice.p2p.commonapi.NodeHandle removeHandle(rice.p2p.commonapi.Id id) {
    return remove((Id) id);
  }

  /**
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + maxSize + theSize +
   * closest + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * + NodeHandle 1st + ... + + + + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   * ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
   * NodeHandle theSize-th + ... + + + +
   * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    buf.writeByte((byte) nodes.length);
    buf.writeByte((byte) theSize);
    buf.writeByte((byte) closest);
    for (int i = 0; i < theSize; i++) {
      nodes[i].serialize(buf);
    }
  }

}