I'd like to make a pull request for my code, but I'm not sure where it fits in.

[ErisianArchitect]

A while back, I designed and implemented a SPSC Pending primitive that allows you to send work to a worker thread and then attempt to receive a response from that thread. It's lightweight and lock-free. I thought maybe it would make a good fit to crossbeam.

I was thinking that it would fit right into crossbeam-utils, but I just wanted to ask to be certain.

[ErisianArchitect]

I suppose I should give more details.

The Pending primitive works in a similar way to an Arc, in the sense that it's reference counted. But there are only two references, the Pending type, and the Responder type. The memory for the response type is allocated with the reference count and the state, much like Arc. There's no queue, no extra heap allocation for the response type, and there are no locks.

It works using atomics to determine what state it's in. It can either be "waiting", "taken", "assigning", or in case of some corrupted state, there's also unknown, which isn't likely to be strictly necessary, so I might remove it.

You can create a Pending/Responder pair, then you send the responder to another thread or wherever you want, then you use the Pending object to try to get a response back. Once the response is received, the state transitions to "taken" so that it can't be accidentally taken twice.

It's a very simple and easy to use API, and works somewhat like a future.