anchor.diff:      do_fold_idx(IO, Chunk,
                   fun({entry, M}, Acc) ->
                           btrie:store(M, Acc)
  -                end, btrie:new(), R);    
  +                end, btrie:new(), R);
   maybe_read_index(IO, _Chunk, _R, false) ->
       file:close(IO),
       delayed.
  
positive.code:         mstore(),
          binary(),
          non_neg_integer()) ->
                   {'error',atom()} |
                   {ok, bitmap:bitmap()}.
  
  bitmap(#mstore{size=S, files=FS, dir=Dir},
      Metric, Time) when
        is_binary(Metric),
        is_integer(Time), Time >= 0 ->
      R = do_get_bitmap(S, FS, Dir, Metric, Time),
  
negative.code: -spec open(Dir :: string(), [open_opt()]) ->
                    {ok, mstore()} | {error, enoent | not_found | invalid_file}.
  open(Dir, Opts) ->
      FullIndexRead = proplists:get_bool(preload_index, Opts),
      case open_mfile(Dir, FullIndexRead) of
          {ok, FileSize, Metrics} ->
              MStore = apply_opts(#mstore{dir=Dir, metrics=Metrics,
                                          size = FileSize}, Opts),
              {ok, MStore#mstore{}};
          Error ->
              Error
      end.
  
  
  %%--------------------------------------------------------------------
  %% @doc
  