| <!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/tokio-util-0.7.8/src/either.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>either.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="../../tokio_util/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="../../tokio_util/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="doccomment">//! Module defining an Either type. |
| </span><span class="kw">use </span>std::{ |
| future::Future, |
| io::SeekFrom, |
| pin::Pin, |
| task::{Context, Poll}, |
| }; |
| <span class="kw">use </span>tokio::io::{AsyncBufRead, AsyncRead, AsyncSeek, AsyncWrite, ReadBuf, <span class="prelude-ty">Result</span>}; |
| |
| <span class="doccomment">/// Combines two different futures, streams, or sinks having the same associated types into a single type. |
| /// |
| /// This type implements common asynchronous traits such as [`Future`] and those in Tokio. |
| /// |
| /// [`Future`]: std::future::Future |
| /// |
| /// # Example |
| /// |
| /// The following code will not work: |
| /// |
| /// ```compile_fail |
| /// # fn some_condition() -> bool { true } |
| /// # async fn some_async_function() -> u32 { 10 } |
| /// # async fn other_async_function() -> u32 { 20 } |
| /// #[tokio::main] |
| /// async fn main() { |
| /// let result = if some_condition() { |
| /// some_async_function() |
| /// } else { |
| /// other_async_function() // <- Will print: "`if` and `else` have incompatible types" |
| /// }; |
| /// |
| /// println!("Result is {}", result.await); |
| /// } |
| /// ``` |
| /// |
| </span><span class="comment">// This is because although the output types for both futures is the same, the exact future |
| // types are different, but the compiler must be able to choose a single type for the |
| // `result` variable. |
| </span><span class="doccomment">/// |
| /// When the output type is the same, we can wrap each future in `Either` to avoid the |
| /// issue: |
| /// |
| /// ``` |
| /// use tokio_util::either::Either; |
| /// # fn some_condition() -> bool { true } |
| /// # async fn some_async_function() -> u32 { 10 } |
| /// # async fn other_async_function() -> u32 { 20 } |
| /// |
| /// #[tokio::main] |
| /// async fn main() { |
| /// let result = if some_condition() { |
| /// Either::Left(some_async_function()) |
| /// } else { |
| /// Either::Right(other_async_function()) |
| /// }; |
| /// |
| /// let value = result.await; |
| /// println!("Result is {}", value); |
| /// # assert_eq!(value, 10); |
| /// } |
| /// ``` |
| </span><span class="attribute">#[allow(missing_docs)] </span><span class="comment">// Doc-comments for variants in this particular case don't make much sense. |
| </span><span class="attribute">#[derive(Debug, Clone)] |
| </span><span class="kw">pub enum </span>Either<L, R> { |
| Left(L), |
| Right(R), |
| } |
| |
| <span class="doccomment">/// A small helper macro which reduces amount of boilerplate in the actual trait method implementation. |
| /// It takes an invocation of method as an argument (e.g. `self.poll(cx)`), and redirects it to either |
| /// enum variant held in `self`. |
| </span><span class="macro">macro_rules! </span>delegate_call { |
| (<span class="macro-nonterminal">$self</span>:ident.<span class="macro-nonterminal">$method</span>:ident($(<span class="macro-nonterminal">$args</span>:ident),+)) => { |
| <span class="kw">unsafe </span>{ |
| <span class="kw">match </span><span class="macro-nonterminal">$self</span>.get_unchecked_mut() { |
| <span class="self">Self</span>::Left(l) => Pin::new_unchecked(l).<span class="macro-nonterminal">$method</span>($(<span class="macro-nonterminal">$args</span>),+), |
| <span class="self">Self</span>::Right(r) => Pin::new_unchecked(r).<span class="macro-nonterminal">$method</span>($(<span class="macro-nonterminal">$args</span>),+), |
| } |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><L, R, O> Future <span class="kw">for </span>Either<L, R> |
| <span class="kw">where |
| </span>L: Future<Output = O>, |
| R: Future<Output = O>, |
| { |
| <span class="kw">type </span>Output = O; |
| |
| <span class="kw">fn </span>poll(<span class="self">self</span>: Pin<<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="self">Self</span>::Output> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll(cx)) |
| } |
| } |
| |
| <span class="kw">impl</span><L, R> AsyncRead <span class="kw">for </span>Either<L, R> |
| <span class="kw">where |
| </span>L: AsyncRead, |
| R: AsyncRead, |
| { |
| <span class="kw">fn </span>poll_read( |
| <span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, |
| cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, |
| buf: <span class="kw-2">&mut </span>ReadBuf<<span class="lifetime">'_</span>>, |
| ) -> Poll<<span class="prelude-ty">Result</span><()>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_read(cx, buf)) |
| } |
| } |
| |
| <span class="kw">impl</span><L, R> AsyncBufRead <span class="kw">for </span>Either<L, R> |
| <span class="kw">where |
| </span>L: AsyncBufRead, |
| R: AsyncBufRead, |
| { |
| <span class="kw">fn </span>poll_fill_buf(<span class="self">self</span>: Pin<<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="kw-2">&</span>[u8]>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_fill_buf(cx)) |
| } |
| |
| <span class="kw">fn </span>consume(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, amt: usize) { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.consume(amt)) |
| } |
| } |
| |
| <span class="kw">impl</span><L, R> AsyncSeek <span class="kw">for </span>Either<L, R> |
| <span class="kw">where |
| </span>L: AsyncSeek, |
| R: AsyncSeek, |
| { |
| <span class="kw">fn </span>start_seek(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, position: SeekFrom) -> <span class="prelude-ty">Result</span><()> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.start_seek(position)) |
| } |
| |
| <span class="kw">fn </span>poll_complete(<span class="self">self</span>: Pin<<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><u64>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_complete(cx)) |
| } |
| } |
| |
| <span class="kw">impl</span><L, R> AsyncWrite <span class="kw">for </span>Either<L, R> |
| <span class="kw">where |
| </span>L: AsyncWrite, |
| R: AsyncWrite, |
| { |
| <span class="kw">fn </span>poll_write(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>, buf: <span class="kw-2">&</span>[u8]) -> Poll<<span class="prelude-ty">Result</span><usize>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_write(cx, buf)) |
| } |
| |
| <span class="kw">fn </span>poll_flush(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<tokio::io::Result<()>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_flush(cx)) |
| } |
| |
| <span class="kw">fn </span>poll_shutdown(<span class="self">self</span>: Pin<<span class="kw-2">&mut </span><span class="self">Self</span>>, cx: <span class="kw-2">&mut </span>Context<<span class="lifetime">'_</span>>) -> Poll<tokio::io::Result<()>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_shutdown(cx)) |
| } |
| } |
| |
| <span class="kw">impl</span><L, R> futures_core::stream::Stream <span class="kw">for </span>Either<L, R> |
| <span class="kw">where |
| </span>L: futures_core::stream::Stream, |
| R: futures_core::stream::Stream<Item = L::Item>, |
| { |
| <span class="kw">type </span>Item = L::Item; |
| |
| <span class="kw">fn </span>poll_next(<span class="self">self</span>: Pin<<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">Option</span><<span class="self">Self</span>::Item>> { |
| <span class="macro">delegate_call!</span>(<span class="self">self</span>.poll_next(cx)) |
| } |
| } |
| |
| <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>tokio::io::{repeat, AsyncReadExt, Repeat}; |
| <span class="kw">use </span>tokio_stream::{once, Once, StreamExt}; |
| |
| <span class="attribute">#[tokio::test] |
| </span><span class="kw">async fn </span>either_is_stream() { |
| <span class="kw">let </span><span class="kw-2">mut </span>either: Either<Once<u32>, Once<u32>> = Either::Left(once(<span class="number">1</span>)); |
| |
| <span class="macro">assert_eq!</span>(<span class="prelude-val">Some</span>(<span class="number">1u32</span>), either.next().<span class="kw">await</span>); |
| } |
| |
| <span class="attribute">#[tokio::test] |
| </span><span class="kw">async fn </span>either_is_async_read() { |
| <span class="kw">let </span><span class="kw-2">mut </span>buffer = [<span class="number">0</span>; <span class="number">3</span>]; |
| <span class="kw">let </span><span class="kw-2">mut </span>either: Either<Repeat, Repeat> = Either::Right(repeat(<span class="number">0b101</span>)); |
| |
| either.read_exact(<span class="kw-2">&mut </span>buffer).<span class="kw">await</span>.unwrap(); |
| <span class="macro">assert_eq!</span>(buffer, [<span class="number">0b101</span>, <span class="number">0b101</span>, <span class="number">0b101</span>]); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="tokio_util" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
