anchor.diff:  %% State record.
   -record(state, {tref,
                   size_per_type=orddict:new(),
  -                clients=0,
                   lines="",
                   clock=0,
                   status=init,
  
positive.code:     Map = orddict:store(Type, Current + Size, Map0),
      {reply, ok, State#state{size_per_type=Map}};
  
  handle_call({start, Filename, Clients}, _From, #state{}=State) ->
      {ok, TRef} = start_timer(),
      _ = lager:info("Instrumentation timer enabled!"),
      {reply, ok, State#state{tref=TRef, clock=0, clients=Clients,
                              filename=Filename, status=running,
                              size_per_type=orddict:new(), lines = []}};
  
  handle_call(stop, _From, #state{lines=Lines0, clock=Clock0,
                                  clients=Clients, size_per_type=Map,
                                  filename=Filename, tref=TRef}=State) ->
      {ok, cancel} = timer:cancel(TRef),
      {ok, Clock, Lines} = record(Clock0, Map, Clients, Filename, Lines0),
      _ = lager:info("Instrumentation timer disabled!"),
      {reply, ok, State#state{tref=undefined, clock=Clock, lines=Lines}};
  
  
negative.code: 
  %% API
  -export([start_link/0,
           start/1,
           log/4,
           stop/0]).
  
  