anchor.diff:      N = make_filename_mgr_name(FluName),
       gen_server:start_link({local, N}, ?MODULE, [FluName, DataDir], []).
   
  --spec find_or_make_filename_from_prefix( FluName :: atom(), Prefix :: {prefix, string()} ) ->
  +-spec find_or_make_filename_from_prefix( FluName :: atom(), 
  +                                         EpochId :: pv1_epoch_n(), 
  +                                         Prefix :: {prefix, string()} ) ->
           {file, Filename :: string()} | {error, Reason :: term() } | timeout.
   % @doc Find the latest available or make a filename from a prefix. A prefix
   % should be in the form of a tagged tuple `{prefix, P}'. Returns a tagged
   % tuple in the form of `{file, F}' or an `{error, Reason}'
  -find_or_make_filename_from_prefix(FluName, {prefix, Prefix}) when is_atom(FluName) ->
  +find_or_make_filename_from_prefix(FluName, EpochId, {prefix, Prefix}) when is_atom(FluName) ->
       N = make_filename_mgr_name(FluName),
  -    gen_server:call(N, {find_filename, Prefix}, ?TIMEOUT); 
  -find_or_make_filename_from_prefix(_FluName, Other) ->
  +    gen_server:call(N, {find_filename, EpochId, Prefix}, ?TIMEOUT); 
  +find_or_make_filename_from_prefix(_FluName, _EpochId, Other) ->
       lager:error("~p is not a valid prefix.", [Other]),
       error(badarg).
   
  
positive.code: %% gen_server API
  init([FluName, DataDir]) ->
      Tid = ets:new(make_filename_mgr_name(FluName), [named_table, {read_concurrency, true}]),
      {ok, #state{ fluname = FluName, datadir = DataDir, tid = Tid }}.
  
  handle_cast(Req, State) ->
      lager:warning("Got unknown cast ~p", [Req]),
      {noreply, State}.
  
  handle_call({find_filename, Prefix}, _From, S = #state{ datadir = DataDir, tid = Tid }) ->
      File = handle_find_file(Tid, Prefix, DataDir),
      {reply, {file, File}, S};
  handle_call({increment_sequence, Prefix}, _From, S = #state{ datadir = DataDir }) ->
      ok = machi_util:increment_max_filenum(DataDir, Prefix),
      {reply, ok, S};
  
negative.code: -export([
      child_spec/2,
      start_link/2,
      find_or_make_filename_from_prefix/3,
      increment_prefix_sequence/2,
      list_files_by_prefix/2
      ]).
  