code: private String encode() {
          byte[] pack = new byte[4 + m_bits.length];
  
          pack[0] = (byte) ((FP_SIZE & 0xffffffff) >> 24);
          pack[1] = (byte) ((FP_SIZE & 0x00ffffff) >> 16);
          pack[2] = (byte) ((FP_SIZE & 0x0000ffff) >> 8);
          pack[3] = (byte) (FP_SIZE & 0x000000ff);
          for (int i = 0; i < m_bits.length; ++i) {
              pack[i + 4] = m_bits[i];
          }
          return base64Encode(pack);
      }
docs: the first four bytes contains the length of the fingerprint