crc64/crc64.go
func (d *digest) Sum(in []byte) []byte {
	s := d.Sum64()
	in = append(in, byte(s))
	in = append(in, byte(s>>8))
	in = append(in, byte(s>>16))
	in = append(in, byte(s>>24))
	in = append(in, byte(s>>32))
	in = append(in, byte(s>>40))
	in = append(in, byte(s>>48))
	in = append(in, byte(s>>56))
	return in
}
func (d *digest) Sum(in []byte) []byte {
	s := d.Sum64()
	in = append(in, byte(s))
	in = append(in, byte(s>>8))
	in = append(in, byte(s>>16))
	in = append(in, byte(s>>24))
	in = append(in, byte(s>>32))
	in = append(in, byte(s>>40))
	in = append(in, byte(s>>48))
	in = append(in, byte(s>>56))
	return in
}
// Encode in little endian