public static UnsignedBytes ofLength(final int len) {
        if (len < 0) {
            throw new IllegalArgumentException("Negative length not allowed");
        }
        if (len > 8) {
            throw new IllegalArgumentException("Lengths > 8 not allowed");
        }
        return INSTANCES[len];
    }
Each instance provides methods for working with unsigned longs that are written
to len bytes. The maximum numeric value of the unsigned value will be governed
by len, e.g for len == 1, the range of values are 0-255.
stroom-lmdb/src/main/java/stroom/lmdb/serde/UnsignedBytesInstances.java