w.mu.Lock()
	defer w.mu.Unlock()
	var err error
	if w.fw != nil {
		err = w.fw.Close()
		flateWriterPool.Put(w.fw)
		w.fw = nil
	}
	return err
}

var flateReaderPool sync.Pool

func newFlateReader(r io.Reader) io.ReadCloser {
	fr, ok := flateReaderPool.Get().(io.ReadCloser)
	if ok {
		fr.(flate.Resetter).Reset(r, nil)
	} else {
		fr = flate.NewReader(r)
	}
	return &pooledFlateReader{fr: fr}
}