public static boolean checkOnOff(MappedByteBuffer mapBuf,
                                     int offset)
    {
        for (int i = 0; i < VespaLevelControllerRepo.numLevels; i++) {
            int off = offset + 4 * i;
            int val = mapBuf.getInt(off);
            if (val != ONVAL && val != OFFVAL) {
                System.err.println("bad on/off value: "+val);
                return false;
            }
        }
        return true;
    }
check that each controlled level is either ON or OFF.
vespalog/src/main/java/com/yahoo/log/MappedLevelController.java