// All the complexity is about doing performant constant-time math on numbers
// larger than any available numeric type.

func sumGeneric(out *[TagSize]byte, msg []byte, key *[32]byte) {
	h := newMACGeneric(key)
	h.Write(msg)
	h.Sum(out)
}

func newMACGeneric(key *[32]byte) macGeneric {
	m := macGeneric{}
	initialize(key, &m.macState)
	return m
}

// macState holds numbers in saturated 64-bit little-endian limbs. That is,