replicationpolicy.java

pastry的java实现的2.0b版

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"FreePastry" Peer-to-Peer Application Development Substrate 

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package rice.p2p.replication;

import java.util.*;

import rice.*;
import rice.p2p.commonapi.*;
import rice.p2p.replication.messaging.*;

/**
 * @(#) ReplicationPolicy.java This interface represents a policy for
 * Replication, which is asked whenever the replication manager need to make an
 * application-specific decision.
 *
 * @version $Id: ReplicationPolicy.java 2302 2005-03-11 00:58:26Z jeffh $
 * @author Alan Mislove
 */
public interface ReplicationPolicy {

  /**
   * This method is given a list of local ids and a list of remote ids, and
   * should return the list of remote ids which need to be fetched. Thus, this
   * method should return the set B-A, where the result is a subset of B.
   *
   * @param local The set of local ids
   * @param remote The set of remote ids
   * @param factory The factory to use to create IdSets
   * @return A subset of the remote ids which need to be fetched
   */
  public IdSet difference(IdSet local, IdSet remote, IdFactory factory);

  /**
   * The default policy for Replication, which simply does a direct diff between
   * the sets
   *
   * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
   * @author Alan Mislove
   */
  public static class DefaultReplicationPolicy implements ReplicationPolicy {

    /**
     * This method simply returns remote-local.
     *
     * @param local The set of local ids
     * @param remote The set of remote ids
     * @param factory The factory to use to create IdSets
     * @return A subset of the remote ids which need to be fetched
     */
    public IdSet difference(IdSet local, IdSet remote, IdFactory factory) {
      IdSet result = factory.buildIdSet();
      Iterator i = remote.getIterator();

      while (i.hasNext()) {
        Id id = (Id) i.next();

        if (!local.isMemberId(id)) {
          result.addId(id);
        }
      }

      return result;
    }
  }
}