code: public static void updateState(String filename, String firstLine, long offset) {
  
      ParseState ps = getState(filename);
  
      if (firstLine != null)
        ps.firstLine = firstLine;
  
      ps.offset = offset;
  
      setState(ps);
    }
docs: Upadate the state of parsing for a particular log file.
  
  @param filename the log file for which to update the state
  @param firstLine the first line of the log file currently
  @param offset the byte offset of the last character parsed