Rust library doesn't know about platform-specific thread handling

[redaranj]

• The C2PA-iOS library wraps the prebuilt C library version of c2pa-rs
• The Rust code spawns threads, in particular for file hashing
• Those threads are always at the default priority level and don't respect the iOS thread priority levels
• This can cause, at very least, warnings in Xcode when a higher-priority thread waits on a lower-priority one
• It's fairly common to set a high priority for a user initiated action so this warning will show up regularly
• It's not likely to cause any kind of deadlock, but it does somewhat undermine the developer's chosen priority

I don't know that having the Rust library be aware of the threading details of the different platforms is ideal. But would it be possible to add a setting to disallow threads? It looks like there are already some places in the code where it will avoid spawning threads if it's WASM.

Issue initially reported here: https://github.com/contentauth/c2pa-ios/issues/30

[github-jira-sync-bot]

:white_check_mark: Jira issue https://jira.corp.adobe.com/browse/CAI-10441 is successfully created for this GitHub issue.