| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/tower-0.4.13/src/util/future_service.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>future_service.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../tower/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../tower/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::{ |
| future::Future, |
| pin::Pin, |
| task::{Context, Poll}, |
| }; |
| <span class="kw">use </span>tower_service::Service; |
| |
| <span class="doccomment">/// Returns a new [`FutureService`] for the given future. |
| /// |
| /// A [`FutureService`] allows you to treat a future that resolves to a service as a service. This |
| /// can be useful for services that are created asynchronously. |
| /// |
| /// # Example |
| /// ``` |
| /// use tower::{service_fn, Service, ServiceExt}; |
| /// use tower::util::future_service; |
| /// use std::convert::Infallible; |
| /// |
| /// # fn main() { |
| /// # async { |
| /// // A future which outputs a type implementing `Service`. |
| /// let future_of_a_service = async { |
| /// let svc = service_fn(|_req: ()| async { Ok::<_, Infallible>("ok") }); |
| /// Ok::<_, Infallible>(svc) |
| /// }; |
| /// |
| /// // Wrap the future with a `FutureService`, allowing it to be used |
| /// // as a service without awaiting the future's completion: |
| /// let mut svc = future_service(Box::pin(future_of_a_service)); |
| /// |
| /// // Now, when we wait for the service to become ready, it will |
| /// // drive the future to completion internally. |
| /// let svc = svc.ready().await.unwrap(); |
| /// let res = svc.call(()).await.unwrap(); |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// # Regarding the [`Unpin`] bound |
| /// |
| /// The [`Unpin`] bound on `F` is necessary because the future will be polled in |
| /// [`Service::poll_ready`] which doesn't have a pinned receiver (it takes `&mut self` and not `self: |
| /// Pin<&mut Self>`). So we cannot put the future into a `Pin` without requiring `Unpin`. |
| /// |
| /// This will most likely come up if you're calling `future_service` with an async block. In that |
| /// case you can use `Box::pin(async { ... })` as shown in the example. |
| </span><span class="kw">pub fn </span>future_service<F, S, R, E>(future: F) -> FutureService<F, S> |
| <span class="kw">where |
| </span>F: Future<Output = <span class="prelude-ty">Result</span><S, E>> + Unpin, |
| S: Service<R, Error = E>, |
| { |
| FutureService::new(future) |
| } |
| |
| <span class="doccomment">/// A type that implements [`Service`] for a [`Future`] that produces a [`Service`]. |
| /// |
| /// See [`future_service`] for more details. |
| </span><span class="attribute">#[derive(Clone)] |
| </span><span class="kw">pub struct </span>FutureService<F, S> { |
| state: State<F, S>, |
| } |
| |
| <span class="kw">impl</span><F, S> FutureService<F, S> { |
| <span class="doccomment">/// Returns a new [`FutureService`] for the given future. |
| /// |
| /// A [`FutureService`] allows you to treat a future that resolves to a service as a service. This |
| /// can be useful for services that are created asynchronously. |
| /// |
| /// # Example |
| /// ``` |
| /// use tower::{service_fn, Service, ServiceExt}; |
| /// use tower::util::FutureService; |
| /// use std::convert::Infallible; |
| /// |
| /// # fn main() { |
| /// # async { |
| /// // A future which outputs a type implementing `Service`. |
| /// let future_of_a_service = async { |
| /// let svc = service_fn(|_req: ()| async { Ok::<_, Infallible>("ok") }); |
| /// Ok::<_, Infallible>(svc) |
| /// }; |
| /// |
| /// // Wrap the future with a `FutureService`, allowing it to be used |
| /// // as a service without awaiting the future's completion: |
| /// let mut svc = FutureService::new(Box::pin(future_of_a_service)); |
| /// |
| /// // Now, when we wait for the service to become ready, it will |
| /// // drive the future to completion internally. |
| /// let svc = svc.ready().await.unwrap(); |
| /// let res = svc.call(()).await.unwrap(); |
| /// # }; |
| /// # } |
| /// ``` |
| /// |
| /// # Regarding the [`Unpin`] bound |
| /// |
| /// The [`Unpin`] bound on `F` is necessary because the future will be polled in |
| /// [`Service::poll_ready`] which doesn't have a pinned receiver (it takes `&mut self` and not `self: |
| /// Pin<&mut Self>`). So we cannot put the future into a `Pin` without requiring `Unpin`. |
| /// |
| /// This will most likely come up if you're calling `future_service` with an async block. In that |
| /// case you can use `Box::pin(async { ... })` as shown in the example. |
| </span><span class="kw">pub fn </span>new(future: F) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ |
| state: State::Future(future), |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><F, S> fmt::Debug <span class="kw">for </span>FutureService<F, S> |
| <span class="kw">where |
| </span>S: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| f.debug_struct(<span class="string">"FutureService"</span>) |
| .field(<span class="string">"state"</span>, <span class="kw-2">&</span><span class="macro">format_args!</span>(<span class="string">"{:?}"</span>, <span class="self">self</span>.state)) |
| .finish() |
| } |
| } |
| |
| <span class="attribute">#[derive(Clone)] |
| </span><span class="kw">enum </span>State<F, S> { |
| Future(F), |
| Service(S), |
| } |
| |
| <span class="kw">impl</span><F, S> fmt::Debug <span class="kw">for </span>State<F, S> |
| <span class="kw">where |
| </span>S: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| <span class="kw">match </span><span class="self">self </span>{ |
| State::Future(<span class="kw">_</span>) => f |
| .debug_tuple(<span class="string">"State::Future"</span>) |
| .field(<span class="kw-2">&</span><span class="macro">format_args!</span>(<span class="string">"<{}>"</span>, std::any::type_name::<F>())) |
| .finish(), |
| State::Service(svc) => f.debug_tuple(<span class="string">"State::Service"</span>).field(svc).finish(), |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><F, S, R, E> Service<R> <span class="kw">for </span>FutureService<F, S> |
| <span class="kw">where |
| </span>F: Future<Output = <span class="prelude-ty">Result</span><S, E>> + Unpin, |
| S: Service<R, Error = E>, |
| { |
| <span class="kw">type </span>Response = S::Response; |
| <span class="kw">type </span>Error = E; |
| <span class="kw">type </span>Future = S::Future; |
| |
| <span class="kw">fn </span>poll_ready(<span class="kw-2">&mut </span><span class="self">self</span>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error>> { |
| <span class="kw">loop </span>{ |
| <span class="self">self</span>.state = <span class="kw">match </span><span class="kw-2">&mut </span><span class="self">self</span>.state { |
| State::Future(fut) => { |
| <span class="kw">let </span>fut = Pin::new(fut); |
| <span class="kw">let </span>svc = <span class="macro">futures_core::ready!</span>(fut.poll(cx)<span class="question-mark">?</span>); |
| State::Service(svc) |
| } |
| State::Service(svc) => <span class="kw">return </span>svc.poll_ready(cx), |
| }; |
| } |
| } |
| |
| <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, req: R) -> <span class="self">Self</span>::Future { |
| <span class="kw">if let </span>State::Service(svc) = <span class="kw-2">&mut </span><span class="self">self</span>.state { |
| svc.call(req) |
| } <span class="kw">else </span>{ |
| <span class="macro">panic!</span>(<span class="string">"FutureService::call was called before FutureService::poll_ready"</span>) |
| } |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| <span class="kw">use </span><span class="kw">crate</span>::util::{future_service, ServiceExt}; |
| <span class="kw">use </span><span class="kw">crate</span>::Service; |
| <span class="kw">use </span>futures::future::{ready, Ready}; |
| <span class="kw">use </span>std::convert::Infallible; |
| |
| <span class="attribute">#[tokio::test] |
| </span><span class="kw">async fn </span>pending_service_debug_impl() { |
| <span class="kw">let </span><span class="kw-2">mut </span>pending_svc = future_service(ready(<span class="prelude-val">Ok</span>(DebugService))); |
| |
| <span class="macro">assert_eq!</span>( |
| <span class="macro">format!</span>(<span class="string">"{:?}"</span>, pending_svc), |
| <span class="string">"FutureService { state: State::Future(<futures_util::future::ready::Ready<core::result::Result<tower::util::future_service::tests::DebugService, core::convert::Infallible>>>) }" |
| </span>); |
| |
| pending_svc.ready().<span class="kw">await</span>.unwrap(); |
| |
| <span class="macro">assert_eq!</span>( |
| <span class="macro">format!</span>(<span class="string">"{:?}"</span>, pending_svc), |
| <span class="string">"FutureService { state: State::Service(DebugService) }" |
| </span>); |
| } |
| |
| <span class="attribute">#[derive(Debug)] |
| </span><span class="kw">struct </span>DebugService; |
| |
| <span class="kw">impl </span>Service<()> <span class="kw">for </span>DebugService { |
| <span class="kw">type </span>Response = (); |
| <span class="kw">type </span>Error = Infallible; |
| <span class="kw">type </span>Future = Ready<<span class="prelude-ty">Result</span><<span class="self">Self</span>::Response, <span class="self">Self</span>::Error>>; |
| |
| <span class="kw">fn </span>poll_ready(<span class="kw-2">&mut </span><span class="self">self</span>, _cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<<span class="prelude-ty">Result</span><(), <span class="self">Self</span>::Error>> { |
| <span class="prelude-val">Ok</span>(()).into() |
| } |
| |
| <span class="kw">fn </span>call(<span class="kw-2">&mut </span><span class="self">self</span>, _req: ()) -> <span class="self">Self</span>::Future { |
| ready(<span class="prelude-val">Ok</span>(())) |
| } |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="tower" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
