nad: support for encoding/decoding stuffit (sit) archives

[rdmark]

StuffIt was the de-facto standard archiving and compression format for Macs throughout the 90s, adding support for it alongside MacBinary and BinHex would make for a near-complete Classic Mac file suite

there is a Rust implementation with a permissive license that we can learn from https://github.com/benletchford/stuffit-rs

[NJRoadfan]

See also: https://github.com/thecloudexpanse/sit

[rdmark]

indeed, I am aware of thecloudexpanse's project

from what I understand the code was rescued from a 90s Usenet archive and doesn't come with a permissive license, so it cannot be used verbatim in a GPL context

[rdmark]

have a working prototype locally with a C shim for the Rust library, however a resilient solution would require the upstream project to provide a stable C ABI, I think

filed benletchford/stuffit-rs#3 to gauge their appetite