ringid.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
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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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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
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********************************************************************************/

package rice.p2p.multiring;

import java.lang.ref.*;
import java.io.*;
import java.util.*;

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

/**
 * @(#) RingId.java This class represents an Id with a specific ring attached.
 *
 * @version $Id: RingId.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public class RingId implements Id {

  /**
   * The id which this ringId represents
   */
  protected Id id;

  /**
   * The ringId which this ringId represents
   */
  protected Id ringId;
  /**
   * DESCRIBE THE FIELD
   */
  public static short TYPE = 2;

  /**
   * Serialver for backward compatibility
   */
  private final static long serialVersionUID = -4390496639871320200L;

  /**
   * Support for coalesced Ids - ensures only one copy of each Id is in memory
   */
  private static WeakHashMap RINGID_MAP = new WeakHashMap();

  /**
   * Constructor
   *
   * @param ringId DESCRIBE THE PARAMETER
   * @param id DESCRIBE THE PARAMETER
   */
  private RingId(Id ringId, Id id) {
    this.id = id;
    this.ringId = ringId;

    if ((id == null) || (ringId == null)) {
      throw new IllegalArgumentException("RingId created with args " + ringId + " " + id);
    }
    if (id instanceof RingId) {
      throw new IllegalArgumentException("RingId created with id as a RingId!" + ringId + " " + id);
    }
    if (ringId instanceof RingId) {
      throw new IllegalArgumentException("RingId created with ringId as a RingId!" + ringId + " " + id);
    }
  }

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

  /**
   * Returns this ringid's id
   *
   * @return The id of this ringid
   */
  public Id getId() {
    return id;
  }

  /**
   * Returns this ringid's ring id
   *
   * @return The ring id of this ringid
   */
  public Id getRingId() {
    return ringId;
  }

  /**
   * Checks if this Id is between two given ids ccw (inclusive) and cw
   * (exclusive) on the circle
   *
   * @param ccw the counterclockwise id
   * @param cw the clockwise id
   * @return true if this is between ccw (inclusive) and cw (exclusive), false
   *      otherwise
   */
  public boolean isBetween(Id ccw, Id cw) {
    if (!(ccw instanceof RingId) || (!((RingId) ccw).getRingId().equals(ringId)) ||
      !(cw instanceof RingId) || (!((RingId) cw).getRingId().equals(ringId))) {
      throw new IllegalArgumentException("Defined only for RingIds from the same ring!");
    }

    return id.isBetween(((RingId) ccw).getId(), ((RingId) cw).getId());
  }

  /**
   * Returns the length of the byte[] representing this Id
   *
   * @return The length of the byte[] representing this Id
   */
  public int getByteArrayLength() {
    return id.getByteArrayLength();
  }

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

  /**
   * Define readResolve, which will replace the deserialized object with the
   * canootical one (if one exists) to ensure RingId coalescing.
   *
   * @return The real RingId
   * @exception ObjectStreamException DESCRIBE THE EXCEPTION
   */
  private Object readResolve() throws ObjectStreamException {
    // commented out to preserve backward compatibility with serialization
    // should be able to reenable in the future
    //return resolve(this);
    return this;
  }

  /**
   * Checks to see if the Id nid is clockwise or counterclockwise from this, on
   * the ring. An Id is clockwise if it is within the half circle clockwise from
   * this on the ring. An Id is considered counter-clockwise from itself.
   *
   * @param nid The id to compare to
   * @return true if clockwise, false otherwise.
   */
  public boolean clockwise(Id nid) {
    if (!(nid instanceof RingId) || (!((RingId) nid).getRingId().equals(ringId))) {
      throw new IllegalArgumentException("Defined only for RingIds from the same ring!");
    }

    return id.clockwise(((RingId) nid).getId());
  }

  /**
   * Returns an Id corresponding to this Id plus a given distance
   *
   * @param offset the distance to add
   * @return the new Id
   */
  public Id addToId(Distance offset) {
    return build(ringId, id.addToId(offset));
  }

  /**
   * Returns the shorter numerical distance on the ring between a pair of Ids.
   *
   * @param nid the other node id.
   * @return the distance between this and nid.
   */
  public Distance distanceFromId(Id nid) {
    if (!(nid instanceof RingId) || (!((RingId) nid).getRingId().equals(ringId))) {
      throw new IllegalArgumentException("Defined only for RingIds from the same ring!");
    }

    return id.distanceFromId(((RingId) nid).getId());
  }

  /**
   * Returns the longer numerical distance on the ring between a pair of Ids.
   *
   * @param nid the other node id.
   * @return the distance between this and nid.
   */
  public Distance longDistanceFromId(Id nid) {
    if (!(nid instanceof RingId) || (!((RingId) nid).getRingId().equals(ringId))) {
      throw new IllegalArgumentException("Defined only for RingIds from the same ring!");
    }

    return id.longDistanceFromId(((RingId) nid).getId());
  }

  /**
   * Returns a (mutable) byte array representing this Id
   *
   * @return A byte[] representing this Id
   */
  public byte[] toByteArray() {
    return id.toByteArray();
  }

  /**
   * Stores the byte[] value of this Id in the provided byte array
   *
   * @param array DESCRIBE THE PARAMETER
   * @param offset DESCRIBE THE PARAMETER
   */
  public void toByteArray(byte[] array, int offset) {
    id.toByteArray(array, offset);
  }

  /**
   * 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 RingId)) {
      return false;
    }

    return (((RingId) o).id.equals(id) && ((RingId) o).ringId.equals(ringId));
  }

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

  /**
   * Returns a string representing this ring Id.
   *
   * @return A string with all of this Id
   */
  public String toString() {
    return "(" + ringId + ", " + id + ")";
  }

  /**
   * Returns a string representing the full length of this Id.
   *
   * @return A string with all of this Id
   */
  public String toStringFull() {
    return "(" + ringId.toStringFull() + ", " + id.toStringFull() + ")";
  }

  /**
   * Returns this id compared to the target
   *
   * @param o DESCRIBE THE PARAMETER
   * @return The comparison
   */
  public int compareTo(Object o) {
    return id.compareTo(((RingId) o).id);
  }

  /**
   * 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);
    buf.writeShort(id.getType());
    id.serialize(buf);
  }

  /**
   * Constructor.
   *
   * @param ringId DESCRIBE THE PARAMETER
   * @param id DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   */
  public static RingId build(Id ringId, Id id) {
    return resolve(new RingId(ringId, id));
  }

  /**
   * Method which resolves the given id to the canonical one
   *
   * @param id The id to resolver
   * @return The canonicaial one
   */
  private static RingId resolve(RingId id) {
    synchronized (RINGID_MAP) {
      WeakReference ref = (WeakReference) RINGID_MAP.get(id);
      RingId result = null;

      if ((ref != null) && ((result = (RingId) ref.get()) != null)) {
        return result;
      } else {
        RINGID_MAP.put(id, new WeakReference(id));
        return id;
      }
    }
  }

  /**
   * Method which splits apart a ringid string and returns the RingID
   *
   * @param s The ring to parse
   * @return The result
   */
  public static RingId build(String s) {
    String[] sArray = s.split("\\(|\\)| |,");
    return build(rice.pastry.Id.build(sArray[1]), rice.pastry.Id.build(sArray[3]));
  }
}