105 lines
2.7 KiB
Rust
105 lines
2.7 KiB
Rust
use pin_project_lite::pin_project;
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use std::{
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fmt,
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future::Future,
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pin::Pin,
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task::{ready, Context, Poll},
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};
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use tower_service::Service;
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pin_project! {
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/// A [`Future`] consuming a [`Service`] and request, waiting until the [`Service`]
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/// is ready, and then calling [`Service::call`] with the request, and
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/// waiting for that [`Future`].
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#[derive(Debug)]
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pub struct Oneshot<S: Service<Req>, Req> {
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#[pin]
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state: State<S, Req>,
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}
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}
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pin_project! {
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#[project = StateProj]
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enum State<S: Service<Req>, Req> {
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NotReady {
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svc: S,
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req: Option<Req>,
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},
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Called {
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#[pin]
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fut: S::Future,
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},
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Done,
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}
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}
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impl<S: Service<Req>, Req> State<S, Req> {
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const fn not_ready(svc: S, req: Option<Req>) -> Self {
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Self::NotReady { svc, req }
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}
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const fn called(fut: S::Future) -> Self {
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Self::Called { fut }
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}
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}
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impl<S, Req> fmt::Debug for State<S, Req>
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where
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S: Service<Req> + fmt::Debug,
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Req: fmt::Debug,
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{
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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State::NotReady {
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svc,
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req: Some(req),
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} => f
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.debug_tuple("State::NotReady")
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.field(svc)
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.field(req)
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.finish(),
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State::NotReady { req: None, .. } => unreachable!(),
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State::Called { .. } => f.debug_tuple("State::Called").field(&"S::Future").finish(),
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State::Done => f.debug_tuple("State::Done").finish(),
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}
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}
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}
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impl<S, Req> Oneshot<S, Req>
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where
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S: Service<Req>,
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{
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#[allow(missing_docs)]
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pub const fn new(svc: S, req: Req) -> Self {
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Oneshot {
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state: State::not_ready(svc, Some(req)),
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}
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}
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}
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impl<S, Req> Future for Oneshot<S, Req>
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where
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S: Service<Req>,
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{
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type Output = Result<S::Response, S::Error>;
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fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
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let mut this = self.project();
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loop {
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match this.state.as_mut().project() {
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StateProj::NotReady { svc, req } => {
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ready!(svc.poll_ready(cx))?;
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let f = svc.call(req.take().expect("already called"));
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this.state.set(State::called(f));
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}
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StateProj::Called { fut } => {
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let res = ready!(fut.poll(cx))?;
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this.state.set(State::Done);
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return Poll::Ready(Ok(res));
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}
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StateProj::Done => panic!("polled after complete"),
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}
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}
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}
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}
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