1use futures_util::ready;
2use pin_project_lite::pin_project;
3use std::future::Future;
4use std::pin::Pin;
5use std::task::{Context, Poll};
6use tower_service::Service;
7
8// Vendored from tower::util to reduce dependencies, the code is small enough.
9
10// Not really pub, but used in a trait for bounds
11pin_project! {
12 #[project = OneshotProj]
13 #[derive(Debug)]
14 pub enum Oneshot<S: Service<Req>, Req> {
15 NotReady {
16 svc: S,
17 req: Option<Req>,
18 },
19 Called {
20 #[pin]
21 fut: S::Future,
22 },
23 Done,
24 }
25}
26
27impl<S, Req> Oneshot<S, Req>
28where
29 S: Service<Req>,
30{
31 pub(crate) const fn new(svc: S, req: Req) -> Self {
32 Oneshot::NotReady {
33 svc,
34 req: Some(req),
35 }
36 }
37}
38
39impl<S, Req> Future for Oneshot<S, Req>
40where
41 S: Service<Req>,
42{
43 type Output = Result<S::Response, S::Error>;
44
45 fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
46 loop {
47 let this: OneshotProj<'_, S, Req> = self.as_mut().project();
48 match this {
49 OneshotProj::NotReady { svc: &mut S, req: &mut Option } => {
50 let _ = ready!(svc.poll_ready(cx))?;
51 let fut: >::Future = svc.call(req.take().expect(msg:"already called"));
52 self.set(Oneshot::Called { fut });
53 }
54 OneshotProj::Called { fut: Pin<&mut >::Future> } => {
55 let res: >::Response = ready!(fut.poll(cx))?;
56 self.set(Oneshot::Done);
57 return Poll::Ready(Ok(res));
58 }
59 OneshotProj::Done => panic!("polled after complete"),
60 }
61 }
62 }
63}
64