anchor.diff:  lvl_open(Dir,Tab) ->
     File = filename:join(Dir,Tab),
     case eleveldb:open(File,[{create_if_missing,true}]) of
  -    {ok,Handle} -> #lvl{table = Tab,handle = Handle,file = File};
  +    {ok,Handle} -> #lvl{name = Tab,handle = Handle,file = File};
       {error,Err} -> throw({500,{open_error,Err}})
     end.
   
  
positive.code:   %%   using it for a lookup in Tab1
    %% - Once the next Key1 is found, it needs to be converted to
    %%   external format before saving in Tab2
    case lvl_get(S,tk(Tab2,Key2)) of
      not_found -> via(S,Tab1,[],Tab2,Key2,false);
      Key1      -> via(S,Tab1,mk_ekey(Key1),Tab2,Key2,true)
    end.
  
  via(S,Tab1,Key1,Tab2,Key2,Retry) ->
    case nextprev(S,next,tk(Tab1,Key1)) of
      end_of_table when Retry ->
        via(S,Tab1,[],Tab2,Key2,false);
      end_of_table ->
        throw({409,end_of_table});
      {TK,V} ->
        NextKey = tk_key(TK),
        NextVal = unpack_val(V),
        ins_overwrite(S,Tab2,Key2,NextKey),
        {[{NextKey,NextVal}]}
    end.
  
  
negative.code:   ets:insert(S#state.tabs,Lvl).
  
  get_lvl(S,Tab) ->
    case ets:lookup(S#state.tabs,Tab) of
      [Lvl=#lvl{}]  -> Lvl;
      undefined     -> throw({404,no_such_table})
    end.
  
  fold_lvl(S,Fun) ->
    ets:foldl(Fun,[],S#state.tabs).
  