The canlock-hp package contains standalone header parsers that can be used to
implement RFC 8315 Netnews Cancel-Locks on the receiving (server) side.
They are intended as preprocessors for canlock, the command line frontend of
libcanlock, but are independent programs.

canlock-mhp (Message Header Parser) is intended to process RFC 5536 Netnews
articles and can be used to extract and unfold a single header field.

canlock-hfp (Header Field Parser) is intended to process RFC 8315 header fields
("Cancel-Lock" and "Cancel-Key").

There is also libcanlock-hp, a library to access the header parsers.