84 lines
2.2 KiB
Rust
84 lines
2.2 KiB
Rust
use futures_core::ready;
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use pin_project::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::{Context, Poll},
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};
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use tower_service::Service;
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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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#[pin_project]
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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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#[pin_project(project = StateProj)]
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enum State<S: Service<Req>, Req> {
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NotReady(S, Option<Req>),
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Called(#[pin] S::Future),
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Done,
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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(s, Some(req)) => f
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.debug_tuple("State::NotReady")
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.field(s)
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.field(req)
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.finish(),
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State::NotReady(_, 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 fn new(svc: S, req: Req) -> Self {
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Oneshot {
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state: State::NotReady(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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let _ = 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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