return
		}
		// Close the stream.
		// If more than compMinIndexSize was written, generate index.
		if cn > compMinIndexSize {
			idx, err := comp.CloseIndex()
			idx = s2.RemoveIndexHeaders(idx)
			indexCh <- idx
			pw.CloseWithError(err)
			return
		}
		pw.CloseWithError(comp.Close())
	}()
	var gotIdx []byte
	return pr, func() []byte {
		if gotIdx != nil {