anchor.diff:                     mem_levels=MemLevels,
                      %% dirty_segments=gb_sets:new(),
                      dirty_segments=bitarray_new(NumSegments),
  +                   write_buffer=[],
  +                   write_buffer_count=0,
                      tree=dict:new()},
       State2 = share_segment_store(State, LinkedStore),
       State2.
  
positive.code:     HKey = encode(State#state.id, Segment, Key),
      case should_insert(HKey, Opts, State) of
          true ->
              ok = eleveldb:put(State#state.ref, HKey, ObjHash, []),
              %% Dirty = gb_sets:add_element(Segment, State#state.dirty_segments),
              Dirty = bitarray_set(Segment, State#state.dirty_segments),
              State#state{dirty_segments=Dirty};
          false ->
              State
      end.
  
  -spec delete(binary(), hashtree()) -> hashtree().
  delete(Key, State) ->
  
negative.code: 
  -spec update_snapshot(hashtree()) -> {hashtree(), hashtree()}.
  update_snapshot(State=#state{segments=NumSegments}) ->
      State2 = flush_buffer(State),
      SnapState = snapshot(State2),
      State3 = SnapState#state{dirty_segments=bitarray_new(NumSegments)},
      {SnapState, State3}.
  
  -spec update_tree(hashtree()) -> hashtree().
  update_tree(State) ->
      State2 = flush_buffer(State),
      State3 = snapshot(State2),
      update_perform(State3).
  
  -spec update_perform(hashtree()) -> hashtree().
  update_perform(State2=#state{dirty_segments=Dirty, segments=NumSegments}) ->
  