func splitPreMasterSecret(secret []byte) (s1, s2 []byte) {
	s1 = secret[0 : (len(secret)+1)/2]
	s2 = secret[len(secret)/2:]
	return
}

// pHash implements the P_hash function, as defined in RFC 4346, Section 5.
func pHash(result, secret, seed []byte, hash func() hash.Hash) {
	h := hmac.New(hash, secret)
	h.Write(seed)
	a := h.Sum(nil)

	j := 0
	for j < len(result) {
		h.Reset()
		h.Write(a)

	hash := hashPath(path)
	if d.Cache == nil {
		d.Cache = make(map[string]dataUsageEntry, 100)
	}
	d.Cache[hash.Key()] = e
	if parent != "" {
		phash := hashPath(parent)
		p := d.Cache[phash.Key()]
		p.addChild(hash)
		d.Cache[phash.Key()] = p
	}
}

// replaceHashed add or replaces an entry to the cache based on its hash.
// If a parent is specified it will be added to that if not already there.