@Override
  public void writeByte(byte b) throws TException {
    writeRawBytes(nonNullByte, 0, 1);
    // Make sure negative numbers comes before positive numbers
    bout[0] = (byte) (b ^ 0x80);
    writeRawBytes(bout, 0, 1);
  }
Whether the current field is sorted ascendingly. Always equals to
sortOrder.charAt(topLevelStructFieldID) != '-'
serde/src/java/org/apache/hadoop/hive/serde2/thrift/TBinarySortableProtocol.java