// Sum64String computes the 64-bit xxHash digest of s with a zero seed. // It may be faster than Sum64([]byte(s)) by avoiding a copy. func Sum64String(s string) uint64 { … } // WriteString adds more data to d. It always returns len(s), nil. // It may be faster than Write([]byte(s)) by avoiding a copy. func (d *Digest) WriteString(s string) (n int, err error) { … } type sliceHeader …