examples/java/kademlia/RoutingTable.java

   1 /* Copyright (c) 2012. The SimGrid Team.
   2  * All rights reserved.                                                     */
   3
   4 /* This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the license (GNU LGPL) which comes with this package. */
   6 package kademlia;
   7 import java.util.Collections;
   8 import java.util.Vector;
   9
  10 import org.simgrid.msg.Msg;
  11 /**
  12  * @brief Contains the various data of a routing table.
  13  */
  14 public class RoutingTable {
  15         /**
  16          * Bucket list
  17          */
  18         private Vector<Bucket> buckets;
  19         /**
  20          * Id of the routing table owner
  21          */
  22         private int id;
  23         /**
  24          * Constructor
  25          */
  26         public RoutingTable(int id) {
  27                 this.id = id;
  28                 buckets = new Vector<Bucket>();
  29                 for (int i = 0; i < Common.IDENTIFIER_SIZE + 1; i++) {
  30                         buckets.add(new Bucket(i));
  31                 }
  32         }
  33         /**
  34          * Returns an identifier which is in a specific bucket of a routing table
  35          * @brief id id of the routing table owner
  36          * @brief prefix id of the bucket where we want that identifier to be
  37          */
  38         public int getIdInPrefix(int id, int prefix) {
  39                 if (prefix == 0) {
  40                         return 0;
  41                 }
  42                 int identifier = 1;
  43                 identifier = identifier << (prefix - 1);
  44                 identifier = identifier ^ id;
  45                 return identifier;
  46         }
  47         /**
  48          * Returns the corresponding node prefix for a given id
  49          */
  50         public int getNodePrefix(int id) {
  51                 for (int j = 0; j < 32; j++) {
  52                         if ((id >> (32 - 1 - j) & 0x1) != 0) {
  53                                 return 32 - j;
  54                         }
  55                 }
  56                 return 0;
  57         }
  58         /**
  59           * Fins the corresponding bucket in a routing table for a given identifier
  60           */
  61         public Bucket findBucket(int id) {
  62                 int xorNumber = id ^ this.id;
  63 //              Msg.info("Number:" + xorNumber.toString(16));
  64                 int prefix = this.getNodePrefix(xorNumber);
  65
  66                 return buckets.get(prefix);
  67         }
  68         /**
  69          * Updates the routing table with a new value.
  70          */
  71         public void update(int id) {
  72
  73                 Bucket bucket = this.findBucket(id);
  74                 if (bucket.contains(id)) {
  75                         Msg.debug("Updating " + Integer.toString(id) + " in my routing table");
  76                         //If the element is already in the bucket, we update it.
  77                         bucket.pushToFront(id);
  78                 }
  79                 else {
  80                         Msg.debug("Adding " + id + " to my routing table");
  81                         bucket.add(id);
  82                         if (bucket.size() > Common.BUCKET_SIZE)  {
  83                                 //TODO: Ping the least seen guy and remove him if he is offline.
  84                         }
  85                 }
  86         }
  87         /**
  88          * Returns the closest notes we know to a given id
  89          */
  90         public Answer findClosest(int destinationId) {
  91                 Answer answer = new Answer(destinationId);
  92
  93
  94                 Bucket bucket = this.findBucket(destinationId);
  95                 bucket.addToAnswer(answer,destinationId);
  96
  97                 for (int i = 1; answer.size() < Common.BUCKET_SIZE &&
  98                 ((bucket.getId() - i) >= 0 ||
  99                 (bucket.getId() + i) <= Common.IDENTIFIER_SIZE); i++) {
 100                         //Check the previous buckets
 101                         if (bucket.getId() - i >= 0) {
 102                                 Bucket bucketP = this.buckets.get(bucket.getId() - i);
 103                                 bucketP.addToAnswer(answer,destinationId);
 104                         }
 105                         //Check the next buckets
 106                         if (bucket.getId() + i <= Common.IDENTIFIER_SIZE) {
 107                                 Bucket bucketN = this.buckets.get(bucket.getId() + i);
 108                                 bucketN.addToAnswer(answer, destinationId);
 109                         }
 110                 }
 111                 //We sort the list
 112                 Collections.sort(answer.getNodes());
 113                 //We trim the list
 114                 while (answer.size() > Common.BUCKET_SIZE) {
 115                         answer.remove(answer.size() - 1); //TODO: Not the best thing.
 116                 }
 117
 118                 return answer;
 119         }
 120
 121         @Override
 122         public String toString() {
 123                 String string = "RoutingTable [ id=" + id + " " ;
 124                 for (int i = 0; i < buckets.size(); i++) {
 125                         if (buckets.get(i).size() > 0) {
 126                                 string += buckets.get(i) + " ";
 127                         }
 128                 }
 129                 return string;
 130         }
 131
 132 }