anchor.diff:      {ok, CpySize} =
           file:copy(filename:join([Dir, encode(FromBucket), encode(FromPath)]),
                     filename:join([Dir, encode(ToBucket), encode(ToPath)])),
  -    {State, {ok, CpySize - ?BKSF_HEADER_SIZE}}.
  +    {State, {ok, CpySize - ?CURRENT_HEADER_SIZE}}.
   
   -spec obj_send(fs_data(), bkss_store:bucket_name(),
                  bkss_store:path(), Trans::bkss_transport:trans()) ->
  
positive.code: %% magic number that indicates a bookshelf file.
  -define(BKSF_IND, 16#0DDBA11).
  
  %% The total header size
  -define(BKSF_HEADER_SIZE, (4 + 14 + 32)).
  
  %% This FILE_PAD is appended to the front of files.
  -define(FILE_PAD, <<?BKSF_IND:32,
                      0,0,0,0,0,0,0,0,0,0,
                      0,0,0,0,0,0,0,0,0,0,
                      0,0,0,0,0,0,0,0,0,0,
  
negative.code: -spec file_md5(file:io_device()) -> {ok, MD5::binary()}.
  file_md5(File) ->
      case file:read(File, ?BKSF_HEADER_SIZE) of
          {ok, <<?BKSF_IND:32/integer, Version:16/integer>>} ->
              parse_header(File, Version);
          _ ->
              {error, invalid_file}
      end.
  
  parse_header(File, 1) ->
      case file:read(File, ?BKSF_HEADER_DETAIL_SIZE_1) of
          {ok, <<_DateStamp:14/binary, MD5:32/binary>>} ->
              {ok, MD5};
          _ ->
              {error, invalid_file}
  