gcid.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.past.gc;

import java.io.IOException;

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

/**
 * @(#) GCId.java This class is the internal representation of an Id with an
 * expiration time in the GC Past system. Should not be used by applications.
 *
 * @version $Id: GCId.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public class GCId implements Id {

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

  /**
   * The ringId which this ringId represents
   */
  protected long expiration;
  /**
   * DESCRIBE THE FIELD
   */
  public final static short TYPE = 3;

  /**
   * Constructor
   *
   * @param id DESCRIBE THE PARAMETER
   * @param expiration DESCRIBE THE PARAMETER
   */
  public GCId(Id id, long expiration) {
    this.id = id;
    this.expiration = expiration;
  }

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

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

  /**
   * Returns this gcid's expiration time
   *
   * @return The expiration time of this gcid
   */
  public long getExpiration() {
    return expiration;
  }

  /**
   * 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) {
    return id.isBetween(((GCId) ccw).getId(), ((GCId) 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() + 8;
  }

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

  /**
   * 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) {
    return id.clockwise(((GCId) 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 new GCId(id.addToId(offset), expiration);
  }

  /**
   * 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) {
    return id.distanceFromId(((GCId) 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) {
    return id.longDistanceFromId(((GCId) nid).getId());
  }

  /**
   * Returns a (mutable) byte array representing this Id
   *
   * @return A byte[] representing this Id
   */
  public byte[] toByteArray() {
    byte[] result = new byte[getByteArrayLength()];

    toByteArray(result, 0);

    return result;
  }

  /**
   * 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);
    MathUtils.longToByteArray(expiration, array, offset + id.getByteArrayLength());
  }

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

    return (((GCId) o).id.equals(id) && (((GCId) o).expiration == expiration));
  }

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

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

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

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

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    // to be peeked
    buf.writeShort(getType());
    buf.writeLong(expiration);
    buf.writeShort(id.getType());
    id.serialize(buf);
  }
}