anchor.diff:          [{LOffset, _, CsumOrTrimmed}] -> {LOffset, Offset - LOffset, CsumOrTrimmed}
       end.
   
  +-spec find_rightneighbor(table(), non_neg_integer()) ->
  +                                undefined |
  +                                {non_neg_integer(), machi_dt:chunk_size(), trimmed|machi_dt:chunk_csum()}.
   find_rightneighbor(CsumT, Offset) ->
       case find(CsumT, Offset, 1) of
           [] -> undefined;
  
positive.code: -spec find(table(), machi_dt:file_offset(), machi_dt:file_size()) ->
                    list({machi_dt:file_offset(),
                          machi_dt:file_size(),
                          machi_dt:chunk_csum()}).
  find(#machi_csum_table{table=T}, Offset, Size) ->
      ets:select(T, [{{'$1', '$2', '$3'},
                      [inclusion_match_spec(Offset, Size)],
  
negative.code:                                end, Chunks),
                   true = ets:insert(T, {Offset, Size, CsumOrTrimmed})
               end
               || {Offset, Size, CsumOrTrimmed} <- List],
              ok;
          {error, enoent} ->
              ok;
          Error ->
  