// Nothing will be read from the stream yet.
func newMetacacheReader(r io.Reader) *metacacheReader {
	dec := s2DecPool.Get().(*s2.Reader)
	dec.Reset(r)
	mr := msgpNewReader(dec)
	return &metacacheReader{
		mr: mr,
		closer: func() {
			dec.Reset(nil)
			s2DecPool.Put(dec)
			readMsgpReaderPoolPut(mr)
		},
		creator: func() error {
			v, err := mr.ReadByte()
			if err != nil {