mtbl_varint(3) on Linux
The text 5eb521ce7bf6, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 9 (Stretch), Debian 8 (Jessie) shipped it. The page shows this text now.
Variable-width encoding and decoding of 32 and 64 bit integers