func New() hash.Hash64
New creates a new hash.Hash64 that implements the 64-bit xxHash algorithm.
func Sum64(b []byte) uint64
Sum64 computes the 64-bit xxHash digest of b.
func Sum64String(s string) uint64
Sum64String computes the 64-bit xxHash digest of s. It may be faster than Sum64([]byte(s)) by avoiding a copy.
TODO(caleb): Consider removing this if an optimization is ever added to make it unnecessary: https://golang.org/issue/2205.
TODO(caleb): We still have a function call; we could instead write Go/asm copies of Sum64 for strings to squeeze out a bit more speed.