XmCvtXmStringToByteStream(3) on Linux
The text 43b385131a05, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie) shipped it.
A compound string function that converts a compound string to a Byte Stream format "XmCvtXmStringToByteStream" "compound string functions" "XmCvtXmStringToByteStream"