saveHeader(curi, latestFetch, A_ETAG_HEADER);
saveHeader(curi, latestFetch, A_LAST_MODIFIED_HEADER);
// save reference length (real or virtual)
long referenceLength;
if (curi.containsDataKey(A_REFERENCE_LENGTH)) {
// reuse previous length if available (see FetchHTTP#setSizes).
referenceLength = (Long) curi.getData().get(A_REFERENCE_LENGTH);
} else {
// normally, use content-length
referenceLength = curi.getContentLength();