| 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256 |
- <!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="API documentation for the Rust `futures` crate."><meta name="keywords" content="rust, rustlang, rust-lang, futures"><title>futures - Rust</title><link rel="stylesheet" type="text/css" href="../normalize.css"><link rel="stylesheet" type="text/css" href="../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../dark.css"><link rel="stylesheet" type="text/css" href="../light.css" id="themeStyle"><script src="../storage.js"></script></head><body class="rustdoc mod"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><p class='location'>Crate futures</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#reexports">Re-exports</a></li><li><a href="#modules">Modules</a></li><li><a href="#macros">Macros</a></li><li><a href="#enums">Enums</a></li><li><a href="#types">Type Definitions</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'futures', ty: 'mod', relpath: '../'};</script></div></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><input class="search-input" name="search" autocomplete="off" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><a id="settings-menu" href="../settings.html"><img src="../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>futures</a></span><span class='out-of-band'><span id='render-detail'><a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[<span class='inner'>−</span>]</a></span><a class='srclink' href='../src/futures/lib.rs.html#1-265' title='goto source code'>[src]</a></span></h1><div class='docblock'><p>Zero-cost Futures in Rust</p>
- <p>This library is an implementation of futures in Rust which aims to provide
- a robust implementation of handling asynchronous computations, ergonomic
- composition and usage, and zero-cost abstractions over what would otherwise
- be written by hand.</p>
- <p>Futures are a concept for an object which is a proxy for another value that
- may not be ready yet. For example issuing an HTTP request may return a
- future for the HTTP response, as it probably hasn't arrived yet. With an
- object representing a value that will eventually be available, futures allow
- for powerful composition of tasks through basic combinators that can perform
- operations like chaining computations, changing the types of futures, or
- waiting for two futures to complete at the same time.</p>
- <p>You can find extensive tutorials and documentations at <a href="https://tokio.rs">https://tokio.rs</a>
- for both this crate (asynchronous programming in general) as well as the
- Tokio stack to perform async I/O with.</p>
- <h2 id="installation" class="section-header"><a href="#installation">Installation</a></h2>
- <p>Add this to your <code>Cargo.toml</code>:</p>
- <pre><code class="language-toml">[dependencies]
- futures = "0.1"
- </code></pre>
- <h2 id="examples" class="section-header"><a href="#examples">Examples</a></h2>
- <p>Let's take a look at a few examples of how futures might be used:</p>
- <pre class="rust rust-example-rendered">
- <span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">futures</span>;
- <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>;
- <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">time</span>::<span class="ident">Duration</span>;
- <span class="kw">use</span> <span class="ident">futures</span>::<span class="ident">prelude</span>::<span class="kw-2">*</span>;
- <span class="kw">use</span> <span class="ident">futures</span>::<span class="ident">future</span>::<span class="ident">Map</span>;
- <span class="comment">// A future is actually a trait implementation, so we can generically take a</span>
- <span class="comment">// future of any integer and return back a future that will resolve to that</span>
- <span class="comment">// value plus 10 more.</span>
- <span class="comment">//</span>
- <span class="comment">// Note here that like iterators, we're returning the `Map` combinator in</span>
- <span class="comment">// the futures crate, not a boxed abstraction. This is a zero-cost</span>
- <span class="comment">// construction of a future.</span>
- <span class="kw">fn</span> <span class="ident">add_ten</span><span class="op"><</span><span class="ident">F</span><span class="op">></span>(<span class="ident">future</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">Map</span><span class="op"><</span><span class="ident">F</span>, <span class="kw">fn</span>(<span class="ident">i32</span>) <span class="op">-></span> <span class="ident">i32</span><span class="op">></span>
- <span class="kw">where</span> <span class="ident">F</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">i32</span><span class="op">></span>,
- {
- <span class="kw">fn</span> <span class="ident">add</span>(<span class="ident">a</span>: <span class="ident">i32</span>) <span class="op">-></span> <span class="ident">i32</span> { <span class="ident">a</span> <span class="op">+</span> <span class="number">10</span> }
- <span class="ident">future</span>.<span class="ident">map</span>(<span class="ident">add</span>)
- }
- <span class="comment">// Not only can we modify one future, but we can even compose them together!</span>
- <span class="comment">// Here we have a function which takes two futures as input, and returns a</span>
- <span class="comment">// future that will calculate the sum of their two values.</span>
- <span class="comment">//</span>
- <span class="comment">// Above we saw a direct return value of the `Map` combinator, but</span>
- <span class="comment">// performance isn't always critical and sometimes it's more ergonomic to</span>
- <span class="comment">// return a trait object like we do here. Note though that there's only one</span>
- <span class="comment">// allocation here, not any for the intermediate futures.</span>
- <span class="kw">fn</span> <span class="ident">add</span><span class="op"><</span><span class="lifetime">'a</span>, <span class="ident">A</span>, <span class="ident">B</span><span class="op">></span>(<span class="ident">a</span>: <span class="ident">A</span>, <span class="ident">b</span>: <span class="ident">B</span>) <span class="op">-></span> <span class="ident">Box</span><span class="op"><</span><span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">i32</span>, <span class="ident">Error</span><span class="op">=</span><span class="ident">A</span>::<span class="ident">Error</span><span class="op">></span> <span class="op">+</span> <span class="lifetime">'a</span><span class="op">></span>
- <span class="kw">where</span> <span class="ident">A</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">i32</span><span class="op">></span> <span class="op">+</span> <span class="lifetime">'a</span>,
- <span class="ident">B</span>: <span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">i32</span>, <span class="ident">Error</span><span class="op">=</span><span class="ident">A</span>::<span class="ident">Error</span><span class="op">></span> <span class="op">+</span> <span class="lifetime">'a</span>,
- {
- <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">a</span>.<span class="ident">join</span>(<span class="ident">b</span>).<span class="ident">map</span>(<span class="op">|</span>(<span class="ident">a</span>, <span class="ident">b</span>)<span class="op">|</span> <span class="ident">a</span> <span class="op">+</span> <span class="ident">b</span>))
- }
- <span class="comment">// Futures also allow chaining computations together, starting another after</span>
- <span class="comment">// the previous finishes. Here we wait for the first computation to finish,</span>
- <span class="comment">// and then decide what to do depending on the result.</span>
- <span class="kw">fn</span> <span class="ident">download_timeout</span>(<span class="ident">url</span>: <span class="kw-2">&</span><span class="ident">str</span>,
- <span class="ident">timeout_dur</span>: <span class="ident">Duration</span>)
- <span class="op">-></span> <span class="ident">Box</span><span class="op"><</span><span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span>, <span class="ident">Error</span><span class="op">=</span><span class="ident">io</span>::<span class="ident">Error</span><span class="op">>></span> {
- <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>;
- <span class="kw">use</span> <span class="ident">std</span>::<span class="ident">net</span>::{<span class="ident">SocketAddr</span>, <span class="ident">TcpStream</span>};
- <span class="kw">type</span> <span class="ident">IoFuture</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="op">=</span> <span class="ident">Box</span><span class="op"><</span><span class="ident">Future</span><span class="op"><</span><span class="ident">Item</span><span class="op">=</span><span class="ident">T</span>, <span class="ident">Error</span><span class="op">=</span><span class="ident">io</span>::<span class="ident">Error</span><span class="op">>></span>;
- <span class="comment">// First thing to do is we need to resolve our URL to an address. This</span>
- <span class="comment">// will likely perform a DNS lookup which may take some time.</span>
- <span class="kw">let</span> <span class="ident">addr</span> <span class="op">=</span> <span class="ident">resolve</span>(<span class="ident">url</span>);
- <span class="comment">// After we acquire the address, we next want to open up a TCP</span>
- <span class="comment">// connection.</span>
- <span class="kw">let</span> <span class="ident">tcp</span> <span class="op">=</span> <span class="ident">addr</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">addr</span><span class="op">|</span> <span class="ident">connect</span>(<span class="kw-2">&</span><span class="ident">addr</span>));
- <span class="comment">// After the TCP connection is established and ready to go, we're off to</span>
- <span class="comment">// the races!</span>
- <span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">tcp</span>.<span class="ident">and_then</span>(<span class="op">|</span><span class="ident">conn</span><span class="op">|</span> <span class="ident">download</span>(<span class="ident">conn</span>));
- <span class="comment">// That all might take awhile, though, so let's not wait too long for it</span>
- <span class="comment">// to all come back. The `select` combinator here returns a future which</span>
- <span class="comment">// resolves to the first value that's ready plus the next future.</span>
- <span class="comment">//</span>
- <span class="comment">// Note we can also use the `then` combinator which is similar to</span>
- <span class="comment">// `and_then` above except that it receives the result of the</span>
- <span class="comment">// computation, not just the successful value.</span>
- <span class="comment">//</span>
- <span class="comment">// Again note that all the above calls to `and_then` and the below calls</span>
- <span class="comment">// to `map` and such require no allocations. We only ever allocate once</span>
- <span class="comment">// we hit the `Box::new()` call at the end here, which means we've built</span>
- <span class="comment">// up a relatively involved computation with only one box, and even that</span>
- <span class="comment">// was optional!</span>
- <span class="kw">let</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">data</span>.<span class="ident">map</span>(<span class="prelude-val">Ok</span>);
- <span class="kw">let</span> <span class="ident">timeout</span> <span class="op">=</span> <span class="ident">timeout</span>(<span class="ident">timeout_dur</span>).<span class="ident">map</span>(<span class="prelude-val">Err</span>);
- <span class="kw">let</span> <span class="ident">ret</span> <span class="op">=</span> <span class="ident">data</span>.<span class="ident">select</span>(<span class="ident">timeout</span>).<span class="ident">then</span>(<span class="op">|</span><span class="ident">result</span><span class="op">|</span> {
- <span class="kw">match</span> <span class="ident">result</span> {
- <span class="comment">// One future succeeded, and it was the one which was</span>
- <span class="comment">// downloading data from the connection.</span>
- <span class="prelude-val">Ok</span>((<span class="prelude-val">Ok</span>(<span class="ident">data</span>), <span class="ident">_other_future</span>)) <span class="op">=></span> <span class="prelude-val">Ok</span>(<span class="ident">data</span>),
- <span class="comment">// The timeout fired, and otherwise no error was found, so</span>
- <span class="comment">// we translate this to an error.</span>
- <span class="prelude-val">Ok</span>((<span class="prelude-val">Err</span>(<span class="ident">_timeout</span>), <span class="ident">_other_future</span>)) <span class="op">=></span> {
- <span class="prelude-val">Err</span>(<span class="ident">io</span>::<span class="ident">Error</span>::<span class="ident">new</span>(<span class="ident">io</span>::<span class="ident">ErrorKind</span>::<span class="ident">Other</span>, <span class="string">"timeout"</span>))
- }
- <span class="comment">// A normal I/O error happened, so we pass that on through.</span>
- <span class="prelude-val">Err</span>((<span class="ident">e</span>, <span class="ident">_other_future</span>)) <span class="op">=></span> <span class="prelude-val">Err</span>(<span class="ident">e</span>),
- }
- });
- <span class="kw">return</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">ret</span>);
- <span class="kw">fn</span> <span class="ident">resolve</span>(<span class="ident">url</span>: <span class="kw-2">&</span><span class="ident">str</span>) <span class="op">-></span> <span class="ident">IoFuture</span><span class="op"><</span><span class="ident">SocketAddr</span><span class="op">></span> {
- <span class="comment">// ...</span>
- }
- <span class="kw">fn</span> <span class="ident">connect</span>(<span class="ident">hostname</span>: <span class="kw-2">&</span><span class="ident">SocketAddr</span>) <span class="op">-></span> <span class="ident">IoFuture</span><span class="op"><</span><span class="ident">TcpStream</span><span class="op">></span> {
- <span class="comment">// ...</span>
- }
- <span class="kw">fn</span> <span class="ident">download</span>(<span class="ident">stream</span>: <span class="ident">TcpStream</span>) <span class="op">-></span> <span class="ident">IoFuture</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">>></span> {
- <span class="comment">// ...</span>
- }
- <span class="kw">fn</span> <span class="ident">timeout</span>(<span class="ident">stream</span>: <span class="ident">Duration</span>) <span class="op">-></span> <span class="ident">IoFuture</span><span class="op"><</span>()<span class="op">></span> {
- <span class="comment">// ...</span>
- }
- }</pre>
- <p>Some more information can also be found in the <a href="https://github.com/rust-lang-nursery/futures-rs#futures-rs">README</a> for now, but
- otherwise feel free to jump in to the docs below!</p>
- </div><h2 id='reexports' class='section-header'><a href="#reexports">Re-exports</a></h2>
- <table><tr><td><code>pub use future::<a class="trait" href="../futures/future/trait.Future.html" title="trait futures::future::Future">Future</a>;</code></td></tr><tr><td><code>pub use future::<a class="trait" href="../futures/future/trait.IntoFuture.html" title="trait futures::future::IntoFuture">IntoFuture</a>;</code></td></tr><tr><td><code>pub use stream::<a class="trait" href="../futures/stream/trait.Stream.html" title="trait futures::stream::Stream">Stream</a>;</code></td></tr><tr><td><code>pub use sink::<a class="trait" href="../futures/sink/trait.Sink.html" title="trait futures::sink::Sink">Sink</a>;</code></td></tr></table><h2 id='modules' class='section-header'><a href="#modules">Modules</a></h2>
- <table>
- <tr class=' module-item'>
- <td><a class="mod" href="executor/index.html"
- title='mod futures::executor'>executor</a></td>
- <td class='docblock-short'>
- <p>Executors</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="future/index.html"
- title='mod futures::future'>future</a></td>
- <td class='docblock-short'>
- <p>Futures</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="prelude/index.html"
- title='mod futures::prelude'>prelude</a></td>
- <td class='docblock-short'>
- <p>A "prelude" for crates using the <code>futures</code> crate.</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="sink/index.html"
- title='mod futures::sink'>sink</a></td>
- <td class='docblock-short'>
- <p>Asynchronous sinks</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="stream/index.html"
- title='mod futures::stream'>stream</a></td>
- <td class='docblock-short'>
- <p>Asynchronous streams</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="sync/index.html"
- title='mod futures::sync'>sync</a></td>
- <td class='docblock-short'>
- <p>Future-aware synchronization</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="task/index.html"
- title='mod futures::task'>task</a></td>
- <td class='docblock-short'>
- <p>Tasks used to drive a future computation</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="mod" href="unsync/index.html"
- title='mod futures::unsync'>unsync</a></td>
- <td class='docblock-short'>
- <p>Future-aware single-threaded synchronization</p>
- </td>
- </tr></table><h2 id='macros' class='section-header'><a href="#macros">Macros</a></h2>
- <table>
- <tr class=' module-item'>
- <td><a class="macro" href="macro.task_local.html"
- title='macro futures::task_local'>task_local</a></td>
- <td class='docblock-short'>
- <p>A macro to create a <code>static</code> of type <code>LocalKey</code></p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="macro" href="macro.try_ready.html"
- title='macro futures::try_ready'>try_ready</a></td>
- <td class='docblock-short'>
- <p>A macro for extracting the successful type of a <code>Poll<T, E></code>.</p>
- </td>
- </tr></table><h2 id='enums' class='section-header'><a href="#enums">Enums</a></h2>
- <table>
- <tr class=' module-item'>
- <td><a class="enum" href="enum.Async.html"
- title='enum futures::Async'>Async</a></td>
- <td class='docblock-short'>
- <p>Return type of future, indicating whether a value is ready or not.</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="enum" href="enum.AsyncSink.html"
- title='enum futures::AsyncSink'>AsyncSink</a></td>
- <td class='docblock-short'>
- <p>The result of an asynchronous attempt to send a value to a sink.</p>
- </td>
- </tr></table><h2 id='types' class='section-header'><a href="#types">Type Definitions</a></h2>
- <table>
- <tr class=' module-item'>
- <td><a class="type" href="type.Poll.html"
- title='type futures::Poll'>Poll</a></td>
- <td class='docblock-short'>
- <p>Return type of the <code>Future::poll</code> method, indicates whether a future's value
- is ready or not.</p>
- </td>
- </tr>
- <tr class=' module-item'>
- <td><a class="type" href="type.StartSend.html"
- title='type futures::StartSend'>StartSend</a></td>
- <td class='docblock-short'>
- <p>Return type of the <code>Sink::start_send</code> method, indicating the outcome of a
- send attempt. See <code>AsyncSink</code> for more details.</p>
- </td>
- </tr></table></section><section id="search" class="content hidden"></section><section class="footer"></section><aside id="help" class="hidden"><div><h1 class="hidden">Help</h1><div class="shortcuts"><h2>Keyboard Shortcuts</h2><dl><dt><kbd>?</kbd></dt><dd>Show this help dialog</dd><dt><kbd>S</kbd></dt><dd>Focus the search field</dd><dt><kbd>↑</kbd></dt><dd>Move up in search results</dd><dt><kbd>↓</kbd></dt><dd>Move down in search results</dd><dt><kbd>↹</kbd></dt><dd>Switch tab</dd><dt><kbd>⏎</kbd></dt><dd>Go to active search result</dd><dt><kbd>+</kbd></dt><dd>Expand all sections</dd><dt><kbd>-</kbd></dt><dd>Collapse all sections</dd></dl></div><div class="infos"><h2>Search Tricks</h2><p>Prefix searches with a type followed by a colon (e.g. <code>fn:</code>) to restrict the search to a given type.</p><p>Accepted types are: <code>fn</code>, <code>mod</code>, <code>struct</code>, <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, and <code>const</code>.</p><p>Search functions by type signature (e.g. <code>vec -> usize</code> or <code>* -> vec</code>)</p><p>Search multiple things at once by splitting your query with comma (e.g. <code>str,u8</code> or <code>String,struct:Vec,test</code>)</p></div></div></aside><script>window.rootPath = "../";window.currentCrate = "futures";</script><script src="../aliases.js"></script><script src="../main.js"></script><script defer src="../search-index.js"></script></body></html>
|
