code: public FP64 extend(long i) {
      extend((byte)((i >>> 52) & 0xFF));
      extend((byte)((i >>> 48) & 0xFF));
      extend((byte)((i >>> 40) & 0xFF));
      extend((byte)((i >>> 32) & 0xFF));
      extend((byte)((i >>> 24) & 0xFF));
      extend((byte)((i >>> 16) & 0xFF));
      extend((byte)((i >>> 8) & 0xFF));
      extend((byte)((i) & 0xFF));
      return this;
    }
docs: Extends this fingerprint by the integer <code>i</code>.
  
  @return
  the resulting fingerprint.