docs: def _readuntil(f, end=_TYPE_END):
  	"""Helper function to read bytes until a certain end byte is hit"""
  	buf = bytearray()
  	byte = f.read(1)
  	while byte != end:
  		if byte == b'':
  			raise ValueError('File ended unexpectedly. Expected end byte {}.'.format(end))
  		buf += byte
  		byte = f.read(1)
  	return buf