How to add handling of new events to the JavisTrace class
  Christian Nentwich (c.nentwich@cs.ucl.ac.uk)
  01/03/1999

  This file describes how handle additional events that occur in the
  simulator and write them into a trace-file, i.e. how to add output
  formatting support for previously unsupported events that occur in a
  network so 'Javis' can handle them (if it can).
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  Table of Contents


  1. Description of Procedures

  2. How to hook in your own handlers



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  1.  Description of Procedures

  The elements in the simulator, for instance a Node, Packet or whatever
  else, generate events whenever something significant occurs. These
  events are sent to whatever subclass of Trace has been registered with
  those objects.


  This document describes how to extend the JavisTrace class to deal
  with new types of events that might have been added into the simulator
  (or are missing from the current implementation of JavisTrace) and get
  the into the output trace file.


  JavisTrace stores a Hashtable object internally that translates the
  name of an event, e.g. "NodeEvent" into an object to process this
  event. Those objects are subclasses of "JavisHandler". A subclass of
  JavisHandler must define handleEvent (and anything else it wants to).



  2.  How to hook in your own handlers

  If you have read the previous section, this should be fairly obvious.
  You created your own subclass of "JavisHandler". When you're finished
  doing that, you can register this class with the JavisTrace class. You
  have to do this after creation of a JavisTrace object, but before any
  output has taken place.


  You can achieve this by calling JavisTrace.registerHandler, pass as
  arguments the name of the event your class handles and an instance of
  the class.


  If you don't have a clue how to write the actual handler class, the
  best thing to do is to look at one of the hard-coded ones, e.g.
  NodeHandler. Make sure you do not look at the one with the longest and
  most complicated bit of code first (e.g. PacketHandler). If you do
  have a clue, you're done, enjoy it.