def unpack_header(data)
      struct_header_len = MAGIC_STRING.size
      magic_message = data[0, struct_header_len]
      len, type = data[struct_header_len..-1].unpack("LL")
      [magic_message, len, type]
    end
def unpack_header(data)
      struct_header_len = MAGIC_STRING.size
      magic_message = data[0, struct_header_len]
      len, type = data[struct_header_len..-1].unpack("LL")
      [magic_message, len, type]
    end
Unpacks the header.
 A typical header looks like:
 @example
   <magic_string><message length><message type>

 @param [String] data: data to be unpacked.