eventqueue.java

DSr project for the java applications

package dsr;


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

//this is an implementation of the Event Queue. Whenever a packet is received by
//the server it is stored in the Event Queue and then it spawns a thread to
//handle that particular packet.
public class EventQueue {

  public static List eventList;     //list of EventQueueEntry.

  //constructor
  public EventQueue() {
    eventList = Collections.synchronizedList(new LinkedList());
  }

  //print out the EventQueue
  public static void printEventQueue() {
    Iterator l = eventList.iterator();
    int i = 0;
    while (l.hasNext()) {
      i++;
      System.out.println("the element in the event queue is " +
                         ((EventQueueEntry)l.next()).toString() );
    }
    System.out.println("the event queue had "  + i + " elements ");
  }

  //This code is for inserting a packet that was received into the event queue.
  public static boolean insertEventQueueEntry(DatagramPacket packet, InetAddress srcIP, InetAddress dstIP) {
    //the srcIP is the IP address of the node from which this packet was
    //received.
    //first it checks if this packet was generated by me. if yes then i don't need
    //to handle this packet.
    if(checkIfPacketBelongsToMe(packet, srcIP, dstIP))
      return false;

    EventQueueEntry newEntry = new EventQueueEntry(packet, srcIP, dstIP);
    System.out.println("the entry is " + newEntry.toString());
   /*
    try {
    if (!eventList.isEmpty() && eventList.contains(newEntry)){
      return true;
    }
    } catch (NullPointerException e) {
      System.out.println("message is  " + e.getMessage());
    }
    */

    //since this is not a packet that was generated by me i need to handle it
    //so i add it to the event queue.
    try{
      eventList.add(newEntry);
    } catch (NullPointerException e) {
      System.out.println("message is  " + e.getMessage());
    }
    System.out.println("an element added to the eventQueue");

    /*//kickDSR();                   //start handling the packets.
    StartUp init = new StartUp();
    Thread thread = new Thread(init);
    thread.start();
    */
    //This is what handles the packet depending on the type of the packet received.
    startDSR();
    //System.out.println("Created a thread " + thread.getName() + "for starting the DSR protocol");
    return true;
  }
  /*
  public void run() {
  StartUp s = new StartUp();
  s.startDSR();
  }
  */

  //when a packet in inserted in the event queue. it calls the following function to
  //handle that particular packet.
  public static void startDSR() {
    System.out.println("ok the aodv has been started");
    System.out.println("the entries in the eventqueue are as follows:- " );
    EventQueue.printEventQueue();

    EventQueueEntry workingEvent =
        new EventQueueEntry((EventQueueEntry)EventQueue.eventList.remove(0));

    //we decode the datagram packet to get the type of the packet.
    //the type is required to find out what kind of packet it is and how it needs to be handled
    ByteArrayInputStream payload = new ByteArrayInputStream(workingEvent.packet.getData());
    DataInputStream src = new DataInputStream(payload);
    byte type = (byte)1;
    System.out.println("after printing out the event queue");

    try {
      type = src.readByte();
    } catch (IOException ie) {}

    //handling the packet on the basis of its type
    switch(type) {
      case Const.RREQ_TYPE:
        System.out.println("ok ........ inside startDSR... RREQ pacet");
        try {
          RREQ.recvRREQ(workingEvent);
          } catch (UnknownHostException e) {}
          break;
        case Const.RREP_TYPE:
          System.out.println("in side startDSR..... RREP packet");
          RREP.recvRREP(workingEvent);
          break;
        case Const.EVENT_RREP_ACK:
          //RREP_ACK.recv.RREP_ACK();
          break;
        case Const.EVENT_RERR:
          //RERR.recvRERR();
          break;
        case Const.EVENT_CLEANUP:
          //RouteTable.findInactiveRouteTableEntry();
          //floodQueue.deleteOldFloodIDQueueEntry();
          break;
        default:
          break;
    }
  }

  //the following functions checks if the packet has been generated by me. reurns true
  //if it wasgenereated by me otherwise false.
  public static boolean checkIfPacketBelongsToMe(DatagramPacket packet, InetAddress srcIP,
      InetAddress dstIP) {
    Iterator vItr = InterfaceList.interfaceList.iterator();
    InetAddress localAddress;
    while (vItr.hasNext()){
      localAddress = ((InterfaceListEntry)vItr.next()).ipAddress;
      if (localAddress.equals(srcIP)) {
        return true;    //found a matching entry. so it was generated by me
      }
    }
    return false;
  }

  //get the first entry in the event queue table
  public static EventQueueEntry getFirstEventQueueEntry() {
    return (EventQueueEntry)eventList.get(0);
  }

  //delete a particular entry in the Event queue
  public static boolean deleteEventQueueEntryByID(int ID) {
    EventQueueEntry tmp_entry = new EventQueueEntry();
    for (int i=0; i < eventList.size(); ++i) {
      tmp_entry = (EventQueueEntry)eventList.get(i);
        if(tmp_entry.ID == ID) {
          try {
            eventList.remove(i);
            return true;
          } catch (ArrayIndexOutOfBoundsException e) {
            System.out.println("ArrayIndexOutOfBoundsException = " + e.getMessage());
          }
        }
    }
    return false;
  }

  //delete the first entry in the Event Queue
  public static boolean deleteFirstEventQueueEntry() {
    try {
      eventList.remove(0);
      return true;
    } catch (ArrayIndexOutOfBoundsException e) {
      System.out.println("ArrayIndexOutOfBoundsException = " +
                         e.getMessage());
    }
    return false;
  }

  //clean up the whole of the event Queue
  public static void cleanUPEventQueue() {
    eventList.clear();
  }
}