<!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 to the Rust file `/home/mrh/.cargo/registry/src/github.com-1ecc6299db9ec823/crossbeam-utils-0.6.5/src/thread.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>thread.rs.html -- source</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><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="shortcut icon" href="../../favicon.ico"><style type="text/css">#crate-search{background-image:url("../../down-arrow.svg");}</style></head><body class="rustdoc source"><!--[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><a href='../../crossbeam_utils/index.html'><div class='logo-container'><img src='../../rust-logo.png' alt='logo'></div></a></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"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><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"><pre class="line-numbers"><span id="1"> 1</span>
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</pre><div class="example-wrap"><pre class="rust ">
<span class="doccomment">//! Threads that can borrow variables from the stack.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Create a scope when spawned threads need to access variables on the stack:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use crossbeam_utils::thread;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let people = vec![</span>
<span class="doccomment">//! "Alice".to_string(),</span>
<span class="doccomment">//! "Bob".to_string(),</span>
<span class="doccomment">//! "Carol".to_string(),</span>
<span class="doccomment">//! ];</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! thread::scope(|s| {</span>
<span class="doccomment">//! for person in &people {</span>
<span class="doccomment">//! s.spawn(move |_| {</span>
<span class="doccomment">//! println!("Hello, {}!", person);</span>
<span class="doccomment">//! });</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! }).unwrap();</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Why scoped threads?</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Suppose we wanted to re-write the previous example using plain threads:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```ignore</span>
<span class="doccomment">//! use std::thread;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let people = vec![</span>
<span class="doccomment">//! "Alice".to_string(),</span>
<span class="doccomment">//! "Bob".to_string(),</span>
<span class="doccomment">//! "Carol".to_string(),</span>
<span class="doccomment">//! ];</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! let mut threads = Vec::new();</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! for person in &people {</span>
<span class="doccomment">//! threads.push(thread::spawn(move |_| {</span>
<span class="doccomment">//! println!("Hello, {}!", person);</span>
<span class="doccomment">//! }));</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! for thread in threads {</span>
<span class="doccomment">//! thread.join().unwrap();</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This doesn't work because the borrow checker complains about `people` not living long enough:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```text</span>
<span class="doccomment">//! error[E0597]: `people` does not live long enough</span>
<span class="doccomment">//! --> src/main.rs:12:20</span>
<span class="doccomment">//! |</span>
<span class="doccomment">//! 12 | for person in &people {</span>
<span class="doccomment">//! | ^^^^^^ borrowed value does not live long enough</span>
<span class="doccomment">//! ...</span>
<span class="doccomment">//! 21 | }</span>
<span class="doccomment">//! | - borrowed value only lives until here</span>
<span class="doccomment">//! |</span>
<span class="doccomment">//! = note: borrowed value must be valid for the static lifetime...</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! The problem here is that spawned threads are not allowed to borrow variables on stack because</span>
<span class="doccomment">//! the compiler cannot prove they will be joined before `people` is destroyed.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Scoped threads are a mechanism to guarantee to the compiler that spawned threads will be joined</span>
<span class="doccomment">//! before the scope ends.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # How scoped threads work</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! If a variable is borrowed by a thread, the thread must complete before the variable is</span>
<span class="doccomment">//! destroyed. Threads spawned using [`std::thread::spawn`] can only borrow variables with the</span>
<span class="doccomment">//! `'static` lifetime because the borrow checker cannot be sure when the thread will complete.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! A scope creates a clear boundary between variables outside the scope and threads inside the</span>
<span class="doccomment">//! scope. Whenever a s.spawns a thread, it promises to join the thread before the scope ends.</span>
<span class="doccomment">//! This way we guarantee to the borrow checker that scoped threads only live within the scope and</span>
<span class="doccomment">//! can safely access variables outside it.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Nesting scoped threads</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Sometimes scoped threads need to spawn more threads within the same scope. This is a little</span>
<span class="doccomment">//! tricky because argument `s` lives *inside* the invocation of `thread::scope()` and as such</span>
<span class="doccomment">//! cannot be borrowed by scoped threads:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```ignore</span>
<span class="doccomment">//! use crossbeam_utils::thread;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! thread::scope(|s| {</span>
<span class="doccomment">//! s.spawn(|_| {</span>
<span class="doccomment">//! // Not going to compile because we're trying to borrow `s`,</span>
<span class="doccomment">//! // which lives *inside* the scope! :(</span>
<span class="doccomment">//! s.spawn(|_| println!("nested thread"));</span>
<span class="doccomment">//! }});</span>
<span class="doccomment">//! });</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Fortunately, there is a solution. Every scoped thread is passed a reference to its scope as an</span>
<span class="doccomment">//! argument, which can be used for spawning nested threads:</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```ignore</span>
<span class="doccomment">//! use crossbeam_utils::thread;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! thread::scope(|s| {</span>
<span class="doccomment">//! // Note the `|s|` here.</span>
<span class="doccomment">//! s.spawn(|s| {</span>
<span class="doccomment">//! // Yay, this works because we're using a fresh argument `s`! :)</span>
<span class="doccomment">//! s.spawn(|_| println!("nested thread"));</span>
<span class="doccomment">//! }});</span>
<span class="doccomment">//! });</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! [`std::thread::spawn`]: https://doc.rust-lang.org/std/thread/fn.spawn.html</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">fmt</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">marker</span>::<span class="ident">PhantomData</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">mem</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">panic</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">sync</span>::{<span class="ident">Arc</span>, <span class="ident">Mutex</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
<span class="kw">use</span> <span class="ident">sync</span>::<span class="ident">WaitGroup</span>;
<span class="kw">type</span> <span class="ident">SharedVec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">Mutex</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span><span class="op">></span>;
<span class="kw">type</span> <span class="ident">SharedOption</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="op">=</span> <span class="ident">Arc</span><span class="op"><</span><span class="ident">Mutex</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">T</span><span class="op">></span><span class="op">></span><span class="op">></span>;
<span class="doccomment">/// Creates a new scope for spawning threads.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// All child threads that haven't been manually joined will be automatically joined just before</span>
<span class="doccomment">/// this function invocation ends. If all joined threads have successfully completed, `Ok` is</span>
<span class="doccomment">/// returned with the return value of `f`. If any of the joined threads has panicked, an `Err` is</span>
<span class="doccomment">/// returned containing errors from panicked threads.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let var = vec![1, 2, 3];</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// s.spawn(|_| {</span>
<span class="doccomment">/// println!("A child thread borrowing `var`: {:?}", var);</span>
<span class="doccomment">/// });</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">scope</span><span class="op"><</span><span class="lifetime">'env</span>, <span class="ident">F</span>, <span class="ident">R</span><span class="op">></span>(<span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-</span><span class="op">></span> <span class="ident">thread</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">R</span><span class="op">></span>
<span class="kw">where</span>
<span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">R</span>,
{
<span class="kw">let</span> <span class="ident">wg</span> <span class="op">=</span> <span class="ident">WaitGroup</span>::<span class="ident">new</span>();
<span class="kw">let</span> <span class="ident">scope</span> <span class="op">=</span> <span class="ident">Scope</span>::<span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> {
<span class="ident">handles</span>: <span class="ident">SharedVec</span>::<span class="ident">default</span>(),
<span class="ident">wait_group</span>: <span class="ident">wg</span>.<span class="ident">clone</span>(),
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
};
<span class="comment">// Execute the scoped function, but catch any panics.</span>
<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">panic</span>::<span class="ident">catch_unwind</span>(<span class="ident">panic</span>::<span class="ident">AssertUnwindSafe</span>(<span class="op">|</span><span class="op">|</span> <span class="ident">f</span>(<span class="kw-2">&</span><span class="ident">scope</span>)));
<span class="comment">// Wait until all nested scopes are dropped.</span>
<span class="ident">drop</span>(<span class="ident">scope</span>.<span class="ident">wait_group</span>);
<span class="ident">wg</span>.<span class="ident">wait</span>();
<span class="comment">// Join all remaining spawned threads.</span>
<span class="kw">let</span> <span class="ident">panics</span>: <span class="ident">Vec</span><span class="op"><</span><span class="kw">_</span><span class="op">></span> <span class="op">=</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">handles</span> <span class="op">=</span> <span class="ident">scope</span>.<span class="ident">handles</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>();
<span class="comment">// Filter handles that haven't been joined, join them, and collect errors.</span>
<span class="kw">let</span> <span class="ident">panics</span> <span class="op">=</span> <span class="ident">handles</span>
.<span class="ident">drain</span>(..)
.<span class="ident">filter_map</span>(<span class="op">|</span><span class="ident">handle</span><span class="op">|</span> <span class="ident">handle</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>().<span class="ident">take</span>())
.<span class="ident">filter_map</span>(<span class="op">|</span><span class="ident">handle</span><span class="op">|</span> <span class="ident">handle</span>.<span class="ident">join</span>().<span class="ident">err</span>())
.<span class="ident">collect</span>();
<span class="ident">panics</span>
};
<span class="comment">// If `f` has panicked, resume unwinding.</span>
<span class="comment">// If any of the child threads have panicked, return the panic errors.</span>
<span class="comment">// Otherwise, everything is OK and return the result of `f`.</span>
<span class="kw">match</span> <span class="ident">result</span> {
<span class="prelude-val">Err</span>(<span class="ident">err</span>) <span class="op">=</span><span class="op">></span> <span class="ident">panic</span>::<span class="ident">resume_unwind</span>(<span class="ident">err</span>),
<span class="prelude-val">Ok</span>(<span class="ident">res</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">if</span> <span class="ident">panics</span>.<span class="ident">is_empty</span>() {
<span class="prelude-val">Ok</span>(<span class="ident">res</span>)
} <span class="kw">else</span> {
<span class="prelude-val">Err</span>(<span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">panics</span>))
}
}
}
}
<span class="doccomment">/// A scope for spawning threads.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> {
<span class="doccomment">/// The list of the thread join handles.</span>
<span class="ident">handles</span>: <span class="ident">SharedVec</span><span class="op"><</span><span class="ident">SharedOption</span><span class="op"><</span><span class="ident">thread</span>::<span class="ident">JoinHandle</span><span class="op"><</span>()<span class="op">></span><span class="op">></span><span class="op">></span>,
<span class="doccomment">/// Used to wait until all subscopes all dropped.</span>
<span class="ident">wait_group</span>: <span class="ident">WaitGroup</span>,
<span class="doccomment">/// Borrows data with invariant lifetime `'env`.</span>
<span class="ident">_marker</span>: <span class="ident">PhantomData</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'env</span> <span class="kw-2">mut</span> <span class="kw-2">&</span><span class="lifetime">'env</span> ()<span class="op">></span>,
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> {}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> <span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> {
<span class="doccomment">/// Spawns a scoped thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This method is similar to the [`spawn`] function in Rust's standard library. The difference</span>
<span class="doccomment">/// is that this thread is scoped, meaning it's guaranteed to terminate before the scope exits,</span>
<span class="doccomment">/// allowing it to reference variables outside the scope.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The scoped thread is passed a reference to this scope as an argument, which can be used for</span>
<span class="doccomment">/// spawning nested threads.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The returned handle can be used to manually join the thread before the scope exits.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`spawn`]: https://doc.rust-lang.org/std/thread/fn.spawn.html</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// let handle = s.spawn(|_| {</span>
<span class="doccomment">/// println!("A child thread is running");</span>
<span class="doccomment">/// 42</span>
<span class="doccomment">/// });</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Join the thread and retrieve its result.</span>
<span class="doccomment">/// let res = handle.join().unwrap();</span>
<span class="doccomment">/// assert_eq!(res, 42);</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">spawn</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">F</span>, <span class="ident">T</span><span class="op">></span>(<span class="kw-2">&</span><span class="lifetime">'scope</span> <span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span>
<span class="kw">where</span>
<span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">T</span>,
<span class="ident">F</span>: <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'env</span>,
<span class="ident">T</span>: <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'env</span>,
{
<span class="self">self</span>.<span class="ident">builder</span>().<span class="ident">spawn</span>(<span class="ident">f</span>).<span class="ident">unwrap</span>()
}
<span class="doccomment">/// Creates a builder that can configure a thread before spawning.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">/// use std::thread::current;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// s.builder()</span>
<span class="doccomment">/// .spawn(|_| println!("A child thread is running"))</span>
<span class="doccomment">/// .unwrap();</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">builder</span><span class="op"><</span><span class="lifetime">'scope</span><span class="op">></span>(<span class="kw-2">&</span><span class="lifetime">'scope</span> <span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ScopedThreadBuilder</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="lifetime">'env</span><span class="op">></span> {
<span class="ident">ScopedThreadBuilder</span> {
<span class="ident">scope</span>: <span class="self">self</span>,
<span class="ident">builder</span>: <span class="ident">thread</span>::<span class="ident">Builder</span>::<span class="ident">new</span>(),
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-</span><span class="op">></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">f</span>.<span class="ident">pad</span>(<span class="string">"Scope { .. }"</span>)
}
}
<span class="doccomment">/// Configures the properties of a new thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The two configurable properties are:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - [`name`]: Specifies an [associated name for the thread][naming-threads].</span>
<span class="doccomment">/// - [`stack_size`]: Specifies the [desired stack size for the thread][stack-size].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The [`spawn`] method will take ownership of the builder and return an [`io::Result`] of the</span>
<span class="doccomment">/// thread handle with the given configuration.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The [`Scope::spawn`] method uses a builder with default configuration and unwraps its return</span>
<span class="doccomment">/// value. You may want to use this builder when you want to recover from a failure to launch a</span>
<span class="doccomment">/// thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// s.builder()</span>
<span class="doccomment">/// .spawn(|_| println!("Running a child thread"))</span>
<span class="doccomment">/// .unwrap();</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [`name`]: struct.ScopedThreadBuilder.html#method.name</span>
<span class="doccomment">/// [`stack_size`]: struct.ScopedThreadBuilder.html#method.stack_size</span>
<span class="doccomment">/// [`spawn`]: struct.ScopedThreadBuilder.html#method.spawn</span>
<span class="doccomment">/// [`Scope::spawn`]: struct.Scope.html#method.spawn</span>
<span class="doccomment">/// [`io::Result`]: https://doc.rust-lang.org/std/io/type.Result.html</span>
<span class="doccomment">/// [naming-threads]: https://doc.rust-lang.org/std/thread/index.html#naming-threads</span>
<span class="doccomment">/// [stack-size]: https://doc.rust-lang.org/std/thread/index.html#stack-size</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ScopedThreadBuilder</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="lifetime">'env</span>: <span class="lifetime">'scope</span><span class="op">></span> {
<span class="ident">scope</span>: <span class="kw-2">&</span><span class="lifetime">'scope</span> <span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span>,
<span class="ident">builder</span>: <span class="ident">thread</span>::<span class="ident">Builder</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="lifetime">'env</span><span class="op">></span> <span class="ident">ScopedThreadBuilder</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="lifetime">'env</span><span class="op">></span> {
<span class="doccomment">/// Sets the name for the new thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The name must not contain null bytes. For more information about named threads, see</span>
<span class="doccomment">/// [here][naming-threads].</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">/// use std::thread::current;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// s.builder()</span>
<span class="doccomment">/// .name("my thread".to_string())</span>
<span class="doccomment">/// .spawn(|_| assert_eq!(current().name(), Some("my thread")))</span>
<span class="doccomment">/// .unwrap();</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">///</span>
<span class="doccomment">/// [naming-threads]: https://doc.rust-lang.org/std/thread/index.html#naming-threads</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">name</span>(<span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">name</span>: <span class="ident">String</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ScopedThreadBuilder</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="lifetime">'env</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">builder</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">builder</span>.<span class="ident">name</span>(<span class="ident">name</span>);
<span class="self">self</span>
}
<span class="doccomment">/// Sets the size of the stack for the new thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The stack size is measured in bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// s.builder()</span>
<span class="doccomment">/// .stack_size(32 * 1024)</span>
<span class="doccomment">/// .spawn(|_| println!("Running a child thread"))</span>
<span class="doccomment">/// .unwrap();</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">stack_size</span>(<span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">size</span>: <span class="ident">usize</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ScopedThreadBuilder</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="lifetime">'env</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">builder</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">builder</span>.<span class="ident">stack_size</span>(<span class="ident">size</span>);
<span class="self">self</span>
}
<span class="doccomment">/// Spawns a scoped thread with this configuration.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The scoped thread is passed a reference to this scope as an argument, which can be used for</span>
<span class="doccomment">/// spawning nested threads.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The returned handle can be used to manually join the thread before the scope exits.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// let handle = s.builder()</span>
<span class="doccomment">/// .spawn(|_| {</span>
<span class="doccomment">/// println!("A child thread is running");</span>
<span class="doccomment">/// 42</span>
<span class="doccomment">/// })</span>
<span class="doccomment">/// .unwrap();</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Join the thread and retrieve its result.</span>
<span class="doccomment">/// let res = handle.join().unwrap();</span>
<span class="doccomment">/// assert_eq!(res, 42);</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">spawn</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">T</span><span class="op">></span>(<span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-</span><span class="op">></span> <span class="ident">io</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span><span class="op">></span>
<span class="kw">where</span>
<span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">T</span>,
<span class="ident">F</span>: <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'env</span>,
<span class="ident">T</span>: <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'env</span>,
{
<span class="comment">// The result of `f` will be stored here.</span>
<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">SharedOption</span>::<span class="ident">default</span>();
<span class="comment">// Spawn the thread and grab its join handle and thread handle.</span>
<span class="kw">let</span> (<span class="ident">handle</span>, <span class="ident">thread</span>) <span class="op">=</span> {
<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">clone</span>(<span class="kw-2">&</span><span class="ident">result</span>);
<span class="comment">// A clone of the scope that will be moved into the new thread.</span>
<span class="kw">let</span> <span class="ident">scope</span> <span class="op">=</span> <span class="ident">Scope</span>::<span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> {
<span class="ident">handles</span>: <span class="ident">Arc</span>::<span class="ident">clone</span>(<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">scope</span>.<span class="ident">handles</span>),
<span class="ident">wait_group</span>: <span class="self">self</span>.<span class="ident">scope</span>.<span class="ident">wait_group</span>.<span class="ident">clone</span>(),
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
};
<span class="comment">// Spawn the thread.</span>
<span class="kw">let</span> <span class="ident">handle</span> <span class="op">=</span> {
<span class="kw">let</span> <span class="ident">closure</span> <span class="op">=</span> <span class="kw">move</span> <span class="op">|</span><span class="op">|</span> {
<span class="comment">// Make sure the scope is inside the closure with the proper `'env` lifetime.</span>
<span class="kw">let</span> <span class="ident">scope</span>: <span class="ident">Scope</span><span class="op"><</span><span class="lifetime">'env</span><span class="op">></span> <span class="op">=</span> <span class="ident">scope</span>;
<span class="comment">// Run the closure.</span>
<span class="kw">let</span> <span class="ident">res</span> <span class="op">=</span> <span class="ident">f</span>(<span class="kw-2">&</span><span class="ident">scope</span>);
<span class="comment">// Store the result if the closure didn't panic.</span>
<span class="kw-2">*</span><span class="ident">result</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>() <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">res</span>);
};
<span class="comment">// Change the type of `closure` from `FnOnce() -> T` to `FnMut() -> T`.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">closure</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">closure</span>);
<span class="kw">let</span> <span class="ident">closure</span> <span class="op">=</span> <span class="kw">move</span> <span class="op">|</span><span class="op">|</span> <span class="ident">closure</span>.<span class="ident">take</span>().<span class="ident">unwrap</span>()();
<span class="comment">// Allocate `clsoure` on the heap and erase the `'env` bound.</span>
<span class="kw">let</span> <span class="ident">closure</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">FnMut</span>() <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'env</span><span class="op">></span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">new</span>(<span class="ident">closure</span>);
<span class="kw">let</span> <span class="ident">closure</span>: <span class="ident">Box</span><span class="op"><</span><span class="ident">FnMut</span>() <span class="op">+</span> <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'static</span><span class="op">></span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">mem</span>::<span class="ident">transmute</span>(<span class="ident">closure</span>) };
<span class="comment">// Finally, spawn the closure.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">closure</span> <span class="op">=</span> <span class="ident">closure</span>;
<span class="self">self</span>.<span class="ident">builder</span>.<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">|</span><span class="op">|</span> <span class="ident">closure</span>())<span class="question-mark">?</span>
};
<span class="kw">let</span> <span class="ident">thread</span> <span class="op">=</span> <span class="ident">handle</span>.<span class="ident">thread</span>().<span class="ident">clone</span>();
<span class="kw">let</span> <span class="ident">handle</span> <span class="op">=</span> <span class="ident">Arc</span>::<span class="ident">new</span>(<span class="ident">Mutex</span>::<span class="ident">new</span>(<span class="prelude-val">Some</span>(<span class="ident">handle</span>)));
(<span class="ident">handle</span>, <span class="ident">thread</span>)
};
<span class="comment">// Add the handle to the shared list of join handles.</span>
<span class="self">self</span>.<span class="ident">scope</span>.<span class="ident">handles</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>().<span class="ident">push</span>(<span class="ident">Arc</span>::<span class="ident">clone</span>(<span class="kw-2">&</span><span class="ident">handle</span>));
<span class="prelude-val">Ok</span>(<span class="ident">ScopedJoinHandle</span> {
<span class="ident">handle</span>,
<span class="ident">result</span>,
<span class="ident">thread</span>,
<span class="ident">_marker</span>: <span class="ident">PhantomData</span>,
})
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">Send</span> <span class="kw">for</span> <span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">Sync</span> <span class="kw">for</span> <span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> {}
<span class="doccomment">/// A handle that can be used to join its scoped thread.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// A join handle to the spawned thread.</span>
<span class="ident">handle</span>: <span class="ident">SharedOption</span><span class="op"><</span><span class="ident">thread</span>::<span class="ident">JoinHandle</span><span class="op"><</span>()<span class="op">></span><span class="op">></span>,
<span class="doccomment">/// Holds the result of the inner closure.</span>
<span class="ident">result</span>: <span class="ident">SharedOption</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
<span class="doccomment">/// A handle to the the spawned thread.</span>
<span class="ident">thread</span>: <span class="ident">thread</span>::<span class="ident">Thread</span>,
<span class="doccomment">/// Borrows the parent scope with lifetime `'scope`.</span>
<span class="ident">_marker</span>: <span class="ident">PhantomData</span><span class="op"><</span><span class="kw-2">&</span><span class="lifetime">'scope</span> ()<span class="op">></span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Waits for the thread to finish and returns its result.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If the child thread panics, an error is returned.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function may panic on some platforms if a thread attempts to join itself or otherwise</span>
<span class="doccomment">/// may create a deadlock with joining threads.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// let handle1 = s.spawn(|_| println!("I'm a happy thread :)"));</span>
<span class="doccomment">/// let handle2 = s.spawn(|_| panic!("I'm a sad thread :("));</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Join the first thread and verify that it succeeded.</span>
<span class="doccomment">/// let res = handle1.join();</span>
<span class="doccomment">/// assert!(res.is_ok());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Join the second thread and verify that it panicked.</span>
<span class="doccomment">/// let res = handle2.join();</span>
<span class="doccomment">/// assert!(res.is_err());</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">join</span>(<span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">thread</span>::<span class="prelude-ty">Result</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// Take out the handle. The handle will surely be available because the root scope waits</span>
<span class="comment">// for nested scopes before joining remaining threads.</span>
<span class="kw">let</span> <span class="ident">handle</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">handle</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>().<span class="ident">take</span>().<span class="ident">unwrap</span>();
<span class="comment">// Join the thread and then take the result out of its inner closure.</span>
<span class="ident">handle</span>
.<span class="ident">join</span>()
.<span class="ident">map</span>(<span class="op">|</span>()<span class="op">|</span> <span class="self">self</span>.<span class="ident">result</span>.<span class="ident">lock</span>().<span class="ident">unwrap</span>().<span class="ident">take</span>().<span class="ident">unwrap</span>())
}
<span class="doccomment">/// Returns a handle to the underlying thread.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use crossbeam_utils::thread;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// thread::scope(|s| {</span>
<span class="doccomment">/// let handle = s.spawn(|_| println!("A child thread is running"));</span>
<span class="doccomment">/// println!("The child thread ID: {:?}", handle.thread().id());</span>
<span class="doccomment">/// }).unwrap();</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">thread</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="kw-2">&</span><span class="ident">thread</span>::<span class="ident">Thread</span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">thread</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> <span class="ident">fmt</span>::<span class="ident">Debug</span> <span class="kw">for</span> <span class="ident">ScopedJoinHandle</span><span class="op"><</span><span class="lifetime">'scope</span>, <span class="ident">T</span><span class="op">></span> {
<span class="kw">fn</span> <span class="ident">fmt</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">f</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">fmt</span>::<span class="ident">Formatter</span>) <span class="op">-</span><span class="op">></span> <span class="ident">fmt</span>::<span class="prelude-ty">Result</span> {
<span class="ident">f</span>.<span class="ident">pad</span>(<span class="string">"ScopedJoinHandle { .. }"</span>)
}
}
</pre></div>
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