How to adduse non Sync resource?

[rancid swallow]

Hiya! I have this interface to my audio engine which is Send but not Sync and it mustn't be cloned or created more than once. How can I add it to Bevy and use it from a system? As a resource/ResMut doesn't work and init_non_send_resourcedidn't work either.

[crude rivet]

You may be looking for insert_non_send_resource https://docs.rs/bevy/latest/bevy/ecs/world/struct.World.html#method.insert_non_send_resource

init_non_send_resource is for types that impl Default

[rancid swallow]

Thanks, that is what I should have used, but implementing Default was fine! Same error though. Inserting the resource works, but using it as a ResMut in a system doesn't

[spiral knoll]

what exactly does this interface do? is this going to be an audio library for bevy?

[spiral knoll]

you should use NonSend or NonSendMut instead of Res or ResMut

[crude rivet]

Yep! https://bevy-cheatbook.github.io/programming/non-send.html

[rancid swallow]

Aha!!

That works, thank you very much!

[rancid swallow]

It holds a handle to a JACK client and to the audio graph that is quite unsafe, but pretty fast. Maybe eventually I'll implement a Bevy plugin interface for it, but it's early days 🙂

[spiral knoll]

you probably should not do non send resources

that should be in its own thread, but systems using non send resource will be on the main thread

you will probably get underruns or your sound will probably lag (depends on what your code is)

[crude rivet]

Non-send resources are fine if you aren't concerned about the reduced parallelism, or if there's no other alternative

[rancid swallow]

The audio stuff is indeed on it's own thread, but the interface for communicating with the audio thread is not Sync

[crude rivet]

Yeah so that should be just fine

[rancid swallow]

I think so too. Maybe another layer of indirection will be worth it for parallelism at some point, but I'll cross that bridge when I get there

[spiral knoll]

yeah that would be fine i think, but i personally would just use a ring buffer to communicate with the audio thread

plus points for making it sync

[rancid swallow]

Is a ringbuffer Sync though? I'm using rtrb for some stuff which is SPSC, don't think it can be shared.

[spiral knoll]

also shameless self promotion i have two bevy plugins: bevy_fundsp for making dsp graphs and bevy_oddio for a bevy_audio or bevy_kira_audio alternative

[spiral knoll]

i use the ringbuf crate and it is Sync

also i am waiting for https://github.com/rust-lang/rust/issues/98407 to land, so probably you could wrap rtrb types in Exclusive to make it sync