reader = rd
	if buf != nil {
		reader = io.TeeReader(rd, buf)
	}

	actualSize := size
	var idxCb func() []byte
	if isCompressible(r.Header, object) && size > minCompressibleSize {
		// Storing the compression metadata.
		metadata[ReservedMetadataPrefix+"compression"] = compressionAlgorithmV2
		metadata[ReservedMetadataPrefix+"actual-size"] = strconv.FormatInt(size, 10)