splitstreamimpl.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.splitstream;

import java.io.*;
import java.util.*;

import rice.environment.Environment;
import rice.environment.params.Parameters;
import rice.p2p.commonapi.*;
import rice.p2p.commonapi.rawserialization.InputBuffer;
import rice.p2p.scribe.*;
import rice.p2p.scribe.rawserialization.ScribeContentDeserializer;

/**
 * This is the implementing class of the ISplitStream interface. It provides the
 * functionality of creating and attaching to channels. This class is
 * responsible for handling all channels that a local node is part of. @(#)
 * SplitStreamImpl.java
 *
 * @version $Id: SplitStreamImpl.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Ansley Post
 * @author Alan Mislove
 */
public class SplitStreamImpl implements SplitStream {

  /**
   * The scribe instance for this SplitStream Object
   */
  protected Scribe scribe;

  /**
   * The node that this application is running on
   */
  protected Node node;

  /**
   * Hashtable of all the channels currently created on this node implicitly or
   * explicitly.
   */
  protected Hashtable channels;

  /**
   * DESCRIBE THE FIELD
   */
  protected final int stripeBaseBitLength;
  /**
   * DESCRIBE THE FIELD
   */
  protected final int maxFailedSubscriptions;
  /**
   * DESCRIBE THE FIELD
   */
  protected final int defaultMaxChildren;

  /**
   * DESCRIBE THE FIELD
   */
  protected String instance;

  /**
   * Convienience constructor which uses the default SplitStreamScribePolicy.
   *
   * @param node
   * @param instance
   */
  public SplitStreamImpl(Node node, String instance) {
    this(node, instance,
      new SplitStreamScribePolicyFactory() {
        public ScribePolicy getSplitStreamScribePolicy(Scribe scribe,
                                                       SplitStream splitstream) {
          return new SplitStreamScribePolicy(scribe, splitstream);
        }
      });
  }

  /**
   * The constructor for building the splitStream object which internally
   * creates it's own Scribe.
   *
   * @param node the pastry node that we will use
   * @param instance The instance name for this splitstream
   * @param factory DESCRIBE THE PARAMETER
   */
  public SplitStreamImpl(Node node, String instance, SplitStreamScribePolicyFactory factory) {
    this.instance = instance;
    Environment environment = node.getEnvironment();
    Parameters p = environment.getParameters();
    defaultMaxChildren = p.getInt("p2p_splitStream_policy_default_maximum_children");
    maxFailedSubscriptions = p.getInt("p2p_splitStream_stripe_max_failed_subscription");
    stripeBaseBitLength = p.getInt("p2p_splitStream_stripeBaseBitLength");
    this.scribe = new ScribeImpl(node, instance);
    scribe.setContentDeserializer(
      new ScribeContentDeserializer() {
        public ScribeContent deserializeScribeContent(InputBuffer buf,
                                                      Endpoint endpoint, short contentType) throws IOException {
          switch (contentType) {
            case SplitStreamContent.TYPE:
              return new SplitStreamContent(buf);
            case SplitStreamSubscribeContent.TYPE:
              return new SplitStreamSubscribeContent(buf);
          }
          throw new IllegalArgumentException("Invalid type:" + contentType);
        }
      });

    this.node = node;
    this.channels = new Hashtable();
    scribe.setPolicy(factory.getSplitStreamScribePolicy(scribe, this));
  }


  /**
   * Returns all of the channels on this local splitstream
   *
   * @return All of the channels currently being received by this splitstream
   */
  public Channel[] getChannels() {
    return (Channel[]) channels.values().toArray(new Channel[0]);
  }

  /**
   * Returns the policy used to control Scribe
   *
   * @return The Scribe policy
   */
  public SplitStreamScribePolicy getPolicy() {
    return (SplitStreamScribePolicy) (scribe.getPolicy());
  }

  /**
   * Gets the StripeBaseBitLength attribute of the SplitStreamImpl object
   *
   * @return The StripeBaseBitLength value
   */
  public int getStripeBaseBitLength() {
    return stripeBaseBitLength;
  }

  /**
   * Gets the Environment attribute of the SplitStreamImpl object
   *
   * @return The Environment value
   */
  public Environment getEnvironment() {
    return scribe.getEnvironment();
  }

  /**
   * This method is used by a peer who wishes to distribute the content using
   * SplitStream. It creates a Channel Object consisting of numStripes number of
   * Stripes, one for each stripe's content. A Channel object is responsible for
   * implementing SplitStream functionality, like maintaining multiple multicast
   * trees, bandwidth management and discovering parents having spare capacity.
   * One Channel object should be created for each content distribution which
   * wishes to use SplitStream.
   *
   * @param id The id of the channel to create
   * @return an instance of a Channel class.
   */
  public Channel createChannel(ChannelId id) {
    return attachChannel(id);
  }

  /**
   * This method is used by peers who wish to listen to content distributed by
   * some other peer using SplitStream. It attaches the local node to the
   * Channel which is being used by the source peer to distribute the content.
   * Essentially, this method finds out the different parameters of Channel
   * object which is created by the source, (the peer distributing the content)
   * , and then creates a local Channel object with these parameters and returns
   * it. This is a non-blocking call so the returned Channel object may not be
   * initialized with all the parameters, so applications should wait for
   * channelIsReady() notification made by channels when they are ready.
   *
   * @param id The id of the channel to create
   * @return An instance of Channel object.
   */
  public Channel attachChannel(ChannelId id) {
    Channel channel = (Channel) channels.get(id);

    if (channel == null) {
      channel = new Channel(id, scribe, instance, node.getIdFactory(), this.node.getId(),
        stripeBaseBitLength, maxFailedSubscriptions);
      channels.put(id, channel);
    }

    ((SplitStreamScribePolicy) scribe.getPolicy()).setMaxChildren(id,
      defaultMaxChildren);
    return channel;
  }

  /**
   * DESCRIBE THE METHOD
   */
  public void destroy() {
    scribe.destroy();
  }
}