code: func EncodeBytesDesc(b []byte, data []byte) []byte {
  	n := len(b)
  	b = EncodeBytes(b, data)
  	reverseBytes(b[n:])
  	return b
  }
docs: // EncodeBytesDesc first encodes bytes using EncodeBytes, then bitwise reverses
  // encoded value to guarantee the encoded value is in descending order for comparison.