def __write_record(self, record_type, data):
    length = len(data)

    crc = crc32c.crc_update(crc32c.CRC_INIT, [record_type])
    crc = crc32c.crc_update(crc, data)
    crc = crc32c.crc_finalize(crc)

    self.__writer.write(
        struct.pack(HEADER_FORMAT, _mask_crc(crc), length, record_type))
    self.__writer.write(data)
    self.__position += HEADER_LENGTH + length
Write single physical record.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/api/files/records.py/RecordsWriter.__write_record