anchor.diff:  ext(?INCREMENTQ, Entry) -> ext_arith(Entry);
   ext(?DECREMENT,  Entry) -> ext_arith(Entry);
   ext(?DECREMENTQ, Entry) -> ext_arith(Entry);
  -ext(_, _) -> undefined.
  -
  -ext_flag_expire(#mc_entry{flag = Flag, expire = Expire}) ->
  -    <<Flag:32, Expire:32>>.
  -
  -ext_arith(#mc_entry{ext = Ext, data = Data, expire = Expire}) ->
  +ext(_, Entry) -> Entry.
  +
  +ext_flag_expire(#mc_entry{ext = Ext, flag = Flag, expire = Expire} = Entry) ->
  +    case Ext of
  +        undefined -> Entry#mc_entry{ext = <<Flag:32, Expire:32>>};
  +        _         -> Entry
  +    end.
  +
  +ext_arith(#mc_entry{ext = Ext, data = Data, expire = Expire} = Entry) ->
       case Ext of
           undefined ->
  -            case Data of
  -                <<>>      -> <<0:64, 0:64, Expire:32>>;
  -                undefined -> <<0:64, 0:64, Expire:32>>;
  -                _         -> <<Data:64, 0:64, Expire:32>>
  -            end;
  -        _ -> Ext
  +            Ext2 = case Data of
  +                       <<>>      -> <<1:64, 0:64, Expire:32>>;
  +                       undefined -> <<1:64, 0:64, Expire:32>>;
  +                       _         -> <<Data:64, 0:64, Expire:32>>
  +                   end,
  +            Entry#mc_entry{ext = Ext2, data = undefined};
  +        _ -> Entry
       end.
   
   % -------------------------------------------------
  
positive.code:     ?assert(H#mc_header.status =/= ?SUCCESS),
      ok = gen_tcp:close(Sock).
  
  stats_test() ->
      {ok, Sock} = gen_tcp:connect("localhost", 11211,
                                   [binary, {packet, 0}, {active, false}]),
  
negative.code: 
  cmd_binary_quiet(Opcode, Sock, _RecvCallback, {Header, Entry}) ->
      ok = send(Sock, req,
                Header#mc_header{opcode = Opcode}, ext(Opcode, Entry)),
      {ok, quiet}.
  
  cmd_binary_vocal(?STAT = Opcode, Sock, RecvCallback, {Header, Entry}) ->
  