private void unread(int c) {
    assert c != -1 : "Trying to push back EOF";
    assert pushBack == -1 : "Trying to push back two bytes";
    pushBack = c;
  }
Push back a character.
Only a single character can be pushed back simultaneously.
ql/src/java/org/apache/hadoop/hive/ql/log/syslog/SyslogParser.java