anchor.diff:  %   <ul> If the byte range is not yet written, `{error, not_written}' is
   %        returned.</ul>
   %   <ul> If the checksum given does not match what comes off the disk,
  -%        `{error, bad_csum}' is returned.</ul>
  +%        `{error, bad_checksum}' is returned.</ul>
   %   <ul> If the number of bytes that comes off the disk is not the requested length,
   %        `{error, partial_read}' is returned.</ul>
   %   <ul> If the offset is at or beyond the current file boundary, `eof' is returned.</ul>
  
positive.code:     end;
  check_or_make_tagged_csum(OtherTag, _ClientCsum, _Data) ->
      lager:warning("Unknown checksum tag ~p", [OtherTag]),
      {error, bad_csum}.
  
  encode_csum_file_entry(Offset, Size, TaggedCSum) ->
      Len = 8 + 4 + byte_size(TaggedCSum),
  
negative.code:                 {error, Bad} ->
                      lager:error("Bad checksum; got ~p, expected ~p",
                                  [Bad, Ck]),
                      {error, bad_checksum};
                  TaggedCsum ->
                      {ok, Bytes, TaggedCsum};
                  %% XXX FIXME: Should we return something other than
  