gd_framenum_subset64(3) on Linux
The text a23cdc93ddcb, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster) shipped it. The page shows this text now.
perform a reverse look-up on a monotonic Dirfile field, with largefile support.