You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: xxhash_unsafe.go
    path of file: ./repos/faasd/vendor/github.com/cespare/xxhash/v2
    
    the code of the file until where you have to start completion: //go:build !appengine
// +build !appengine

// This file encapsulates usage of unsafe.
// xxhash_safe.go contains the safe
    
func (d *Digest) WriteString(s string) (n int, err error) {
	d.Write(*(*[]byte)(unsafe.Pointer(&sliceHeader{s, len(s)})))
	// d.Write always returns len(s), nil.
	// Ignoring the return output and returning these fixed values buys a
	// savings of 6 in the inliner's cost model.
	return len(s), nil
}