@Override
  public void writeI16(short i16) throws TException {
    i16out[0] = (byte) (0xff & ((i16 >> 8) ^ 0x80));
    i16out[1] = (byte) (0xff & (i16));
    writeRawBytes(nonNullByte, 0, 1);
    writeRawBytes(i16out, 0, 2);
  }
Whether the current field is sorted ascendingly. Always equals to
sortOrder.charAt(topLevelStructFieldID) != '-'
serde/src/java/org/apache/hadoop/hive/serde2/thrift/TBinarySortableProtocol.java