if c == nil || !c.Valid() {
		return nil
	}
	return map[string]string{c.Type.String(): c.Encoded}
}

// TransferChecksumHeader will transfer any checksum value that has been checked.
// If checksum was trailing, they must have been added to r.Trailer.
func TransferChecksumHeader(w http.ResponseWriter, r *http.Request) {
	c, err := GetContentChecksum(r.Header)
	if err != nil || c == nil {
		return
	}

	// clients expect the ETag header key to be literally "ETag" - not "Etag" (case-sensitive).
	// Therefore, we have to set the ETag directly as map entry.
	w.Header()[xhttp.ETag] = []string{"\"" + etag + "\""}
	hash.TransferChecksumHeader(w, r)

	writeSuccessResponseHeadersOnly(w)
}

// CompleteMultipartUploadHandler - Complete multipart upload.