How to use the pyulog.core.ULog._MessageData function in pyulog

def _read_file_data(self, message_name_filter_list, read_until=None):
        """
        read the file data section
        :param read_until: an optional file offset: if set, parse only up to
                           this offset (smaller than)
        """

        if read_until is None:
            read_until = 1 << 50 # make it larger than any possible log file

        try:
            # pre-init reusable objects
            header = self._MessageHeader()
            msg_data = self._MessageData()

            curr_file_pos = self._file_handle.tell()

            while True:
                data = self._file_handle.read(3)
                curr_file_pos += len(data)
                header.initialize(data)
                data = self._file_handle.read(header.msg_size)
                curr_file_pos += len(data)
                if len(data) < header.msg_size:
                    break # less data than expected. File is most likely cut

                if curr_file_pos > read_until:
                    if self._debug:
                        print('read until offset=%i done, current pos=%i' %
                              (read_until, curr_file_pos))