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 open(string(), proplists:proplist()) ->
                    {ok, table()} | {error, file:posix()}.
  open(CSumFilename, _Opts) ->
      T = ets:new(?MODULE, [private, ordered_set]),
      CSum = machi_util:make_tagged_csum(none),
      %% Dummy entry for headers
      true = ets:insert_new(T, {0, ?MINIMUM_OFFSET, CSum}),
      C0 = #machi_csum_table{
             file=CSumFilename,
             table=T},
      case file:read_file(CSumFilename) of
          %% , [read, raw, binary]) of
          {ok, Bin} ->
              List = case split_checksum_list_blob_decode(Bin) of
                         {List0, <<>>} ->
  
negative.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()|trimmed}).
  find(#machi_csum_table{table=T}, Offset, Size) ->
      ets:select(T, [{{'$1', '$2', '$3'},
                      [inclusion_match_spec(Offset, Size)],
  