cache cache
	group singleflight.Group

	// hashPool is a per authenticator pool of hash.Hash (to avoid allocations from building the Hash)
	// HMAC with SHA-256 and a random key is used to prevent precomputation and length extension attacks
	// It also mitigates hash map DOS attacks via collisions (the inputs are supplied by untrusted users)
	hashPool *sync.Pool
}

type cache interface {

	var symname string
	if len(s) > 100 {
		// Huge strings are hashed to avoid long names in object files.
		// Indulge in some paranoia by writing the length of s, too,
		// as protection against length extension attacks.
		// Same pattern is known to fileStringSym below.
		h := notsha256.New()
		io.WriteString(h, s)
		symname = fmt.Sprintf(stringSymPattern, len(s), shortHashString(h.Sum(nil)))
	} else {