nodeset.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
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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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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
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if advised of the possibility of such damage.

********************************************************************************/
package rice.pastry;

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

import rice.environment.random.RandomSource;
import rice.p2p.commonapi.rawserialization.*;

/**
 * Represents an ordered set of NodeHandles. *
 *
 * @version $Id: NodeSet.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Peter Druschel
 */

public class NodeSet implements NodeSetI, Serializable {

  private Vector set;

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

  final static long serialVersionUID = 4410658508346287677L;

  /**
   * Constructor.
   */
  public NodeSet() {
    set = new Vector();
  }

  /**
   * Constructor.
   *
   * @param s DESCRIBE THE PARAMETER
   */
  public NodeSet(Vector s) {
    set = s;
  }

  /**
   * Copy constructor.
   *
   * @param o DESCRIBE THE PARAMETER
   */
  public NodeSet(NodeSet o) {
    set = new Vector(o.set);
  }

  /**
   * Constructor for NodeSet.
   *
   * @param buf DESCRIBE THE PARAMETER
   * @param nhf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public NodeSet(InputBuffer buf, NodeHandleFactory nhf) throws IOException {
    short numNodes = buf.readShort();
    set = new Vector(numNodes);
    for (int i = 0; i < numNodes; i++) {
      set.add(nhf.readNodeHandle(buf));
    }
  }

  /**
   * Finds the NodeHandle associated with a NodeId.
   *
   * @param nid a node id.
   * @return the handle associated with that id or null if no such handle is
   *      found.
   */

  public NodeHandle get(Id nid) {
    NodeHandle h;

    try {
      return (NodeHandle) set.elementAt(getIndex(nid));
    } catch (Exception e) {
      return null;
    }

  }

  /**
   * Gets the ith element in the set.
   *
   * @param i an index.
   * @return the handle, or null if the position is out of bounds
   */

  public NodeHandle get(int i) {
    NodeHandle h;

    try {
      h = (NodeHandle) set.elementAt(i);
    } catch (Exception e) {
      return null;
    }

    return h;
  }

  /**
   * Gets the index of the element with the given node id.
   *
   * @param nid the node id.
   * @return the index or -1 if no such element
   */

  public int getIndex(Id nid) {
    return getIndexId(nid);
  }

  /**
   * Gets the Index attribute of the NodeSet object
   *
   * @param nh DESCRIBE THE PARAMETER
   * @return The Index value
   */
  public int getIndex(NodeHandle nh) {
    NodeHandle h;

    for (int i = 0; i < set.size(); i++) {
      try {
        h = (NodeHandle) set.elementAt(i);
        if (h.equals(nh)) {
          return i;
        }
      } catch (Exception e) {
      }
    }

    return -1;
  }

  /**
   * Gets the IndexId attribute of the NodeSet object
   *
   * @param nid DESCRIBE THE PARAMETER
   * @return The IndexId value
   */
  private int getIndexId(rice.p2p.commonapi.Id nid) {
    NodeHandle h;

    for (int i = 0; i < set.size(); i++) {
      try {
        h = (NodeHandle) set.elementAt(i);
        if (h.getNodeId().equals(nid)) {
          return i;
        }
      } catch (Exception e) {
      }
    }

    return -1;
  }

  /**
   * return an iterator that iterates over the elements of this set
   *
   * @return the interator
   */
  public Iterator getIterator() {
    return set.iterator();
  }

  /**
   * Finds the NodeHandle associated with the NodeId.
   *
   * @param id a node id.
   * @return the handle associated with that id or null if no such handle is
   *      found.
   */
  public rice.p2p.commonapi.NodeHandle getHandle(rice.p2p.commonapi.Id id) {
    return getHandle(id);
  }

  /**
   * Gets the ith element in the set.
   *
   * @param i an index.
   * @return the handle associated with that id or null if no such handle is
   *      found.
   */
  public rice.p2p.commonapi.NodeHandle getHandle(int i) {
    return get(i);
  }

  /**
   * Gets the index of the element with the given node id.
   *
   * @param id the id.
   * @return the index or throws a NoSuchElementException.
   * @exception NoSuchElementException DESCRIBE THE EXCEPTION
   */
  public int getIndexHandle(rice.p2p.commonapi.Id id)
     throws NoSuchElementException {
    return getIndex((Id) id);
  }

  /**
   * Gets the Type attribute of the NodeSet object
   *
   * @return The Type value
   */
  public short getType() {
    return TYPE;
  }

  /*
   *  NodeSet methods
   */
  /**
   * Appends a member to the ordered set.
   *
   * @param handle the handle to put.
   * @return false if handle was already a member, true otherwise
   */

  public boolean put(NodeHandle handle) {
    if (set.contains(handle)) {
      return false;
    }

    set.add(handle);
    return true;
  }

  /**
   * Method which randomizes the order of this NodeSet
   *
   * @param random DESCRIBE THE PARAMETER
   */
  public void randomize(RandomSource random) {
    for (int i = 0; i < set.size(); i++) {
      int a = random.nextInt(set.size());
      int b = random.nextInt(set.size());
      Object tmp = set.elementAt(a);
      set.setElementAt(set.elementAt(b), a);
      set.setElementAt(tmp, b);
    }
  }

  /**
   * test membership using Id
   *
   * @param id the id to test
   * @return true of NodeHandle associated with id is a member, false otherwise
   */

  //    public boolean member(NodeId nid) {
  //	return (getIndex(nid) >= 0);
  //    }
  private boolean memberId(rice.p2p.commonapi.Id id) {
    return (getIndexId(id) >= 0);
  }

  /**
   * Removes a node id and its handle from the set.
   *
   * @param nid the node to remove.
   * @return the node handle removed or null if nothing.
   */

  public NodeHandle remove(Id nid) {
    try {
      return (NodeHandle) set.remove(getIndex(nid));
    } catch (Exception e) {
      return null;
    }
  }

  /**
   * Gets the number of elements.
   *
   * @return the size.
   */

  public int size() {
    return set.size();
  }

  /*
   *  additional methods unique to NodeSet
   */
  /**
   * insert a member at the given index
   *
   * @param index the position at which to insert the element into the ordered
   *      set
   * @param handle the handle to add
   * @return false if handle was already a member, true otherwise
   */
  public boolean insert(int index, NodeHandle handle) {
    if (set.contains(handle)) {
      return false;
    }

    set.add(index, handle);
    return true;
  }

  /**
   * remove a member
   *
   * @param handle the handle to remove
   * @return DESCRIBE THE RETURN VALUE
   */
  public NodeHandle remove(NodeHandle handle) {
    if (set.remove(handle)) {
      return handle;
    }
    return null;
  }

  /**
   * remove a member at a given position
   *
   * @param index the position of the member to remove
   */
  public void remove(int index) {
    set.remove(index);
  }

  /**
   * determine rank of a member
   *
   * @param handle the handle to test
   * @return rank (index) of the handle, or -1 if handle is not a member
   */
  public int indexOf(NodeHandle handle) {
    return set.indexOf(handle);
  }

  /**
   * test membership
   *
   * @param handle the handle to test
   * @return true of handle is a member, false otherwise
   */
  public boolean member(NodeHandle handle) {
    return set.contains(handle);
  }

  /**
   * return a subset of this set, consisting of the members within a given range
   * of positions
   *
   * @param from the lower end of the range (inclusive)
   * @param to the upper end of the range (exclusive)
   * @return the subset, or null of the arguments were out of bounds
   */
  NodeSet subSet(int from, int to) {
    NodeSet res;

    try {
      res = new NodeSet(new Vector(set.subList(from, to)));
    } catch (Exception e) {
      return null;
    }

    return res;
  }

  /**
   * Returns a string representation of the NodeSet
   *
   * @return DESCRIBE THE RETURN VALUE
   */

  public String toString() {
    String s = "NodeSet: ";
    for (int i = 0; i < size(); i++) {
      s = s + get(i).getNodeId();
    }

    return s;
  }

  // Common API Support

  /**
   * Puts a NodeHandle into the set.
   *
   * @param handle the handle to put.
   * @return true if the put succeeded, false otherwise.
   */
  public boolean putHandle(rice.p2p.commonapi.NodeHandle handle) {
    return put((NodeHandle) handle);
  }

  /**
   * Verifies if the set contains this particular id.
   *
   * @param id a node id.
   * @return true if that node id is in the set, false otherwise.
   */
  public boolean memberHandle(rice.p2p.commonapi.Id id) {
    return memberId(id);
  }

  /**
   * Removes a node id and its handle from the set.
   *
   * @param id DESCRIBE THE PARAMETER
   * @return the node handle removed or null if nothing.
   */
  public rice.p2p.commonapi.NodeHandle removeHandle(rice.p2p.commonapi.Id id) {
    return remove((rice.pastry.Id) id);
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public Iterator iterator() {
    return set.iterator();
  }

  /**
   * DESCRIBE THE METHOD
   *
   * @param buf DESCRIBE THE PARAMETER
   * @exception IOException DESCRIBE THE EXCEPTION
   */
  public void serialize(OutputBuffer buf) throws IOException {
    buf.writeShort((short) set.size());
    Iterator i = set.iterator();
    while (i.hasNext()) {
      NodeHandle nh = (NodeHandle) i.next();
      nh.serialize(buf);
    }
  }
}