fetchmessage.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
modification, are permitted provided that the following conditions are
met:

- Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

- Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
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
or implied including, but not limited to, representations or
warranties of non-infringement, merchantability or fitness for a
particular purpose. In no event shall RICE or contributors be liable
for any direct, indirect, incidental, special, exemplary, or
consequential damages (including, but not limited to, procurement of
substitute goods or services; loss of use, data, or profits; or
business interruption) however caused and on any theory of liability,
whether in contract, strict liability, or tort (including negligence
or otherwise) arising in any way out of the use of this software, even
if advised of the possibility of such damage.

********************************************************************************/

package rice.p2p.past.messaging;

import java.io.IOException;

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

/**
 * @(#) FetchMessage.java This class represents a message which is a fetch
 * request in past, based on a handle). response should be a PastContent
 *
 * @version $Id: FetchMessage.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 * @author Ansley Post
 * @author Peter Druschel
 */
public class FetchMessage extends ContinuationMessage {

  // the id to fetch
  private RawPastContentHandle handle;

  // whether or not this message has been cached
  private boolean cached = false;
  /**
   * DESCRIBE THE FIELD
   */
  public final static short TYPE = 3;

  /**
   * Constructor
   *
   * @param uid The unique id
   * @param handle The handle to the data to be looked up
   * @param source The source address
   * @param dest The destination address
   */
  public FetchMessage(int uid, PastContentHandle handle, NodeHandle source, Id dest) {
    this(uid, handle instanceof RawPastContentHandle ? (RawPastContentHandle) handle : new JavaSerializedPastContentHandle(handle), source, dest);
  }

  /**
   * Constructor for FetchMessage.
   *
   * @param uid DESCRIBE THE PARAMETER
   * @param handle DESCRIBE THE PARAMETER
   * @param source DESCRIBE THE PARAMETER
   * @param dest DESCRIBE THE PARAMETER
   */
  public FetchMessage(int uid, RawPastContentHandle handle, NodeHandle source, Id dest) {
    super(uid, source, dest);

    this.handle = handle;
  }

  /**
   * Constructor for FetchMessage.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @param pcd DESCRIBE THE PARAMETER
   * @param pchd DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  private FetchMessage(InputBuffer buf, Endpoint endpoint, PastContentDeserializer pcd, PastContentHandleDeserializer pchd) throws IOException {
    super(buf, endpoint);
    // if called super.serializer(x, true) these will be set
    if (serType == S_SUB) {
      short type2 = buf.readShort();
      response = pcd.deserializePastContent(buf, endpoint, type2);
    }

    cached = buf.readBoolean();

    short type = buf.readShort();
    if (type == 0) {
      handle = new JavaSerializedPastContentHandle(pchd.deserializePastContentHandle(buf, endpoint, type));
    } else {
      handle = (RawPastContentHandle) pchd.deserializePastContentHandle(buf, endpoint, type);
    }
  }

  /**
   * Method which returns the handle
   *
   * @return The contained handle
   */
  public PastContentHandle getHandle() {
//  if (content == null)
    if (handle.getType() == 0) {
      return ((JavaSerializedPastContentHandle) handle).getPCH();
    }
    return handle;
  }

  /**
   * Returns whether or not this message has been cached
   *
   * @return Whether or not this message has been cached
   */
  public boolean isCached() {
    return cached;
  }

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

  /**
   * Sets this message as having been cached.
   */
  public void setCached() {
    cached = true;
  }

  /**
   * Returns a string representation of this message
   *
   * @return A string representing this message
   */
  public String toString() {
    return "[FetchMessage for " + handle + " cached? " + cached + "]";
  }

  /**
   * 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
    if (response != null && response instanceof RawPastContent) {
      super.serialize(buf, false);
      RawPastContent rpc = (RawPastContent) response;
      buf.writeShort(rpc.getType());
      rpc.serialize(buf);
    } else {
      super.serialize(buf, true);
    }

    buf.writeBoolean(cached);

//    System.out.println("FetchMessage.serialize() handle = "+handle);
    buf.writeShort(handle.getType());
    handle.serialize(buf);
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param endpoint DESCRIBE THE PARAMETER
   * @param pcd DESCRIBE THE PARAMETER
   * @param pchd DESCRIBE THE PARAMETER
   * @return DESCRIBE THE RETURN VALUE
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public static FetchMessage build(InputBuffer buf, Endpoint endpoint, PastContentDeserializer pcd, PastContentHandleDeserializer pchd) throws IOException {
    byte version = buf.readByte();
    switch (version) {
      case 0:
        return new FetchMessage(buf, endpoint, pcd, pchd);
      default:
        throw new IOException("Unknown Version: " + version);
    }
  }
}