You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: decode_res4.m
    path of file: ./repos/bspm/thirdparty/spm12/external/fieldtrip/fileio/private
    
    the code of the file until where you have to start completion: function R4F = decode_res4(chunk)

% DECODE_RES4 is a helper function for real-time processing of CTF data. This
% function is used to decode the content of the optional ctf_res4 chunck.
%
% See also DECODE_FIF, DECODE_NIFTI1, SAP2MATLAB

% decode the res4 file content
if 0
  % using  READ_CTF_RES4 -- this does not produce a proper .grad structure
  % TODO: remove this code, and possibly read_ctf_res4 as well
  tmp_name = tempname;
  F = fopen(tmp_name, 'wb');
  fwrite(F, chunk, 'uint8');
  fclose(F);
  R4F = read_ctf_res4(tmp_name);
  delete(tmp_name);

    
function R4F = decode_res4(chunk)

% DECODE_RES4 is a helper function for real-time processing of CTF data. This
% function is used to decode the content of the optional ctf_res4 chunck.
%
% See also DECODE_FIF, DECODE_NIFTI1, SAP2MATLAB

% decode the res4 file content
if 0
  % using  READ_CTF_RES4 -- this does not produce a proper .grad structure
  % TODO: remove this code, and possibly read_ctf_res4 as well
  tmp_name = tempname;
  F = fopen(tmp_name, 'wb');
  fwrite(F, chunk, 'uint8');
  fclose(F);
  R4F = read_ctf_res4(tmp_name);
  delete(tmp_name);
else
  % using FT_READ_HEADER recursively, and then readCTFds in the second call
  % this will also call ctf2grad and yield correct gradiometer information
  tmp_name = tempname;
  [dirname, fname] = fileparts(tmp_name);
  res4fn = [tmp_name '.ds/' fname '.res4'];
  meg4fn = [tmp_name '.ds/' fname '.meg4'];
  dsname = [tmp_name '.ds'];
  
  mkdir(dsname);
  
  F = fopen(res4fn, 'wb');
  fwrite(F, chunk, 'uint8');
  fclose(F);
  
  F = fopen(meg4fn, 'wb');
  fwrite(F, 'MEG42CP');
  fclose(F);
  
  R4F = ft_read_header(dsname, 'coordsys', 'dewar');
  
  delete(res4fn);
  delete(meg4fn);
  rmdir(dsname);
end