def METHOD_NAME(self, data):
    count = len(data)
    sect_begin = self._sect_begin(self._offset)
    offset_in_sect = self._offset_in_sect(self._offset)
    sect_size = self._sect_size(self._offset, count)
    self._buf = self._client.read(sect_begin, sect_size)
    buf = self._buf[0: offset_in_sect] + data + \
          self._buf[offset_in_sect + count:]
    self._client.METHOD_NAME(buf, sect_begin)
    self._client.flush()
    self._offset += count
    return count