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use std::sync::mpsc::{self, Receiver, RecvError, SendError, Sender};
pub struct Fulfiller<T>(pub(crate) Sender<T>);
pub struct Awaiter<T>(Receiver<T>);
pub fn promissory<T>() -> (Fulfiller<T>, Awaiter<T>)
where
T: Send,
{
let (send, recv) = mpsc::channel();
(Fulfiller(send), Awaiter(recv))
}
impl<T: Send> Awaiter<T> {
pub fn await_value(self) -> Result<T, RecvError> {
self.0.recv()
}
}
impl<T> Fulfiller<T>
where
T: Send,
{
pub fn fulfill(self, t: T) -> Result<(), SendError<T>> {
self.0.send(t)
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::thread;
#[test]
fn basic_exchange() -> Result<(), RecvError> {
let (send, recv) = promissory();
thread::spawn(move || send.fulfill(42));
let r = recv.await_value()?;
assert_eq!(42, r);
Ok(())
}
}