anchor.diff:          [{Key, {_Value, false, 0, _Version}}] ->
               ?ETS:delete(DB, Key),
               {DB, ok};
  -        [{Key, _Value}] ->
  -            {DB, locks_set};
  -        [] ->
  -            {DB, undef}
  +        [{Key, _Value}] -> {DB, locks_set};
  +        [] -> {DB, undef}
       end.
   
   %% @doc reads the version of a key
  
positive.code:             {DB, ok};
          [{Key, {_Value, false, _ReadLock, _Version}}] ->
              {DB, failed};
          [] ->
              {DB, failed}
      end.
  
  %% @doc sets a read lock on a key
  
negative.code: -spec(get_range/3 :: (db(), key(), key()) -> [{key(), value()}]).
  get_range(DB, From, To) ->
      F = fun ({Key, {Value, _, _, _}}, Data) ->
                  case Value =/= empty_val
                      andalso util:is_between(From, Key, To) of
                      true -> [{Key, Value} | Data];
                      false -> Data
                  end
          end,
      ?ETS:foldl(F, [], DB).
  