private byte[] readWordOrNil(int sizeHint) throws IOException {
    byte[] ret = readWord(sizeHint);

    if (ret.length == 1 && ret[0] == '-') {
      return null;
    }

    return ret;
  }
Read a word (until next space or EOF) as a byte array.
If the complete word is "-", return null.

@param sizeHint an guess on how large string will be, in bytes.
ql/src/java/org/apache/hadoop/hive/ql/log/syslog/SyslogParser.java