sourceroute.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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- 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.pastry.socket;

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

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

/**
 * Class which represets a source route to a remote IP address.
 *
 * @version $Id: SourceRoute.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public class SourceRoute extends PRawMessage implements Serializable {

  // the default distance, which is used before a ping
  /**
   * DESCRIBE THE FIELD
   */
  protected EpochInetSocketAddress[] path;

  // serialver, for backward compatibility
  private final static long serialVersionUID = -4402277039316685149L;

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

  /**
   * DESCRIBE THE FIELD
   */
  public final static short TYPE = 1;

  /**
   * Constructor
   *
   * @param path DESCRIBE THE PARAMETER
   */
  private SourceRoute(EpochInetSocketAddress[] path) {
    super(0);
    this.path = path;
  }

  /**
   * Method which returns the first "hop" of this source route
   *
   * @return The first hop of this source route
   */
  public EpochInetSocketAddress getFirstHop() {
    return path[0];
  }

  /**
   * Method which returns the first "hop" of this source route
   *
   * @return The first hop of this source route
   */
  public EpochInetSocketAddress getLastHop() {
    return path[path.length - 1];
  }

  /**
   * Returns the number of hops in this source route
   *
   * @return The number of hops
   */
  public int getNumHops() {
    return path.length;
  }

  /**
   * Returns the hop at the given index
   *
   * @param i The hop index
   * @return The hop
   */
  public EpochInetSocketAddress getHop(int i) {
    return path[i];
  }

  /**
   * Returns whether or not this route is direct
   *
   * @return whether or not this route is direct
   */
  public boolean isDirect() {
    return (path.length == 1);
  }

  /**
   * 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 Id coalescing.
   *
   * @return The real Id
   * @exception ObjectStreamException DESCRIBE THE EXCEPTION
   */
  private Object readResolve() throws ObjectStreamException {
    return resolve(SOURCE_ROUTE_MAP, this);
  }

  /**
   * Returns the hashCode of this source route
   *
   * @return The hashCode
   */
  public int hashCode() {
    int result = 399388937;

    for (int i = 0; i < path.length; i++) {
      result ^= path[i].hashCode();
    }

    return result;
  }

  /**
   * Checks equaltiy on source routes
   *
   * @param o The source route to compare to
   * @return The equality
   */
  public boolean equals(Object o) {
    if (o == null) {
      return false;
    }

    return Arrays.equals(path, ((SourceRoute) o).path);
  }

  /**
   * Internal method for computing the toString of an array of
   * InetSocketAddresses
   *
   * @return THe string
   */
  public String toString() {
    StringBuffer result = new StringBuffer();
    result.append("{");

    for (int i = 0; i < path.length; i++) {
      EpochInetSocketAddress thePath = path[i];
      InetSocketAddress theAddr = thePath.getAddress();
      InetAddress theAddr2 = theAddr.getAddress();
      if (theAddr2 == null) {
        result.append(theAddr.toString());
      } else {
        String ha = theAddr2.getHostAddress();
        result.append(ha + ":" + theAddr.getPort());
      }
      if (i < path.length - 1) {
        result.append(" -> ");
      }
    }

    result.append("}");

    return result.toString();
  }

  /**
   * Internal method for computing the toString of an array of
   * InetSocketAddresses
   *
   * @return THe string
   */
  public String toStringFull() {
    StringBuffer result = new StringBuffer();
    result.append("{");

    for (int i = 0; i < path.length; i++) {
      result.append(path[i].toString());
      if (i < path.length - 1) {
        result.append(" -> ");
      }
    }

    result.append("}");

    return result.toString();
  }

  /**
   * Method which revereses path and cliams the corresponding address
   *
   * @param localAddress DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   */
  public SourceRoute reverse(EpochInetSocketAddress localAddress) {
    EpochInetSocketAddress[] result = new EpochInetSocketAddress[path.length];

    for (int i = 0; i < path.length - 1; i++) {
      result[i] = path[path.length - 2 - i];
    }

    result[result.length - 1] = localAddress;

    return SourceRoute.build(result);
  }

  /**
   * Method which revereses path
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public SourceRoute reverse() {
    EpochInetSocketAddress[] result = new EpochInetSocketAddress[path.length];

    for (int i = 0; i < path.length; i++) {
      result[i] = path[path.length - 1 - i];
    }

    return SourceRoute.build(result);
  }

  /**
   * Returns whether or not this route goes through the given address
   *
   * @param address DESCRIBE THE PARAMETER
   * @return whether or not this route goes through the given address
   */
  public boolean goesThrough(EpochInetSocketAddress address) {
    for (int i = 0; i < path.length; i++) {
      if (path[i].equals(address)) {
        return true;
      }
    }

    return false;
  }

  /**
   * Internal method which returns an array representing the source route
   *
   * @return An array represetning the route
   */
  public InetSocketAddress[] toArray() {
    InetSocketAddress[] result = new InetSocketAddress[path.length];

    for (int i = 0; i < result.length; i++) {
      result[i] = path[i].getAddress();
    }

    return result;
  }

  /**
   * Method which creates a new source route by removing the last hop of this
   * one
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public SourceRoute removeLastHop() {
    EpochInetSocketAddress[] result = new EpochInetSocketAddress[path.length - 1];
    System.arraycopy(path, 0, result, 0, result.length);

    return SourceRoute.build(result);
  }

  /**
   * Method which creates a new source route by appending the given address to
   * the end of this one
   *
   * @param address The address to append
   * @return DESCRIBE THE RETURN VALUE
   */
  public SourceRoute append(EpochInetSocketAddress address) {
    EpochInetSocketAddress[] result = new EpochInetSocketAddress[path.length + 1];
    System.arraycopy(path, 0, result, 0, path.length);
    result[result.length - 1] = address;

    return SourceRoute.build(result);
  }

  /**
   * Method which creates a new source route by appending the given address to
   * the end of this one
   *
   * @param address The address to append
   * @return DESCRIBE THE RETURN VALUE
   */
  public SourceRoute prepend(EpochInetSocketAddress address) {
    EpochInetSocketAddress[] result = new EpochInetSocketAddress[path.length + 1];
    System.arraycopy(path, 0, result, 1, path.length);
    result[0] = address;

    return SourceRoute.build(result);
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    buf.writeByte((byte) 0);
    // version
    buf.writeInt(path.length);
    for (int i = 0; i < path.length; i++) {
      path[i].serialize(buf);
    }
  }

  /**
   * Method which performs the coalescing and interaction with the weak hash map
   *
   * @param map DESCRIBE THE PARAMETER
   * @param route DESCRIBE THE PARAMETER
   * @return The Id to use
   */
  protected static SourceRoute resolve(WeakHashMap map, SourceRoute route) {
    synchronized (map) {
      WeakReference ref = (WeakReference) map.get(route);
      SourceRoute result = null;

      if ((ref != null) && ((result = (SourceRoute) ref.get()) != null)) {
        return result;
      } else {
        map.put(route, new WeakReference(route));
        return route;
      }
    }
  }

  /**
   * Constructor.
   *
   * @param path The path of the route
   * @return DESCRIBE THE RETURN VALUE
   */
  public static SourceRoute build(EpochInetSocketAddress[] path) {
    return resolve(SOURCE_ROUTE_MAP, new SourceRoute(path));
  }

  /**
   * Constructor.
   *
   * @param address DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   */
  public static SourceRoute build(EpochInetSocketAddress address) {
    return resolve(SOURCE_ROUTE_MAP, new SourceRoute(new EpochInetSocketAddress[]{address}));
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public static SourceRoute build(InputBuffer buf) throws IOException {
    byte version = buf.readByte();
    switch (version) {
      case 0:
        int numInPath = buf.readInt();
        EpochInetSocketAddress[] path = new EpochInetSocketAddress[numInPath];
        for (int i = 0; i < numInPath; i++) {
          path[i] = EpochInetSocketAddress.build(buf);
        }
        return new SourceRoute(path);
      default:
        throw new IOException("Unknown Version: " + version);
    }
  }

}