code: func AddString64(h uint64, s string) uint64 {
  	/*
  		This is an unrolled version of this algorithm:
  
  		for _, c := range s {
  			h = (h ^ uint64(c)) * prime64
  		}
  
  		It seems to be ~1.5x faster than the simple loop in BenchmarkHash64:
  
  		- BenchmarkHash64/hash_function-4   30000000   56.1 ns/op   642.15 MB/s   0 B/op   0 allocs/op
  		- BenchmarkHash64/hash_function-4   50000000   38.6 ns/op   932.35 MB/s   0 B/op   0 allocs/op
  
  	*/
  
  	i := 0
  	n := (len(s) / 8) * 8
  
  	for i != n {
  		h = (h ^ uint64(s[i])) * prime64
  		h = (h ^ uint64(s[i+1])) * prime64
  		h = (h ^ uint64(s[i+2])) * prime64
  		h = (h ^ uint64(s[i+3])) * prime64
  		h = (h ^ uint64(s[i+4])) * prime64
  		h = (h ^ uint64(s[i+5])) * prime64
  		h = (h ^ uint64(s[i+6])) * prime64
  		h = (h ^ uint64(s[i+7])) * prime64
  		i += 8
  	}
  
  	for _, c := range s[i:] {
  		h = (h ^ uint64(c)) * prime64
  	}
  
  	return h
  }
docs: // AddString64 adds the hash of s to the precomputed hash value h.