| <!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/sync/cancellation_token.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>cancellation_token.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">//! An asynchronously awaitable `CancellationToken`. |
| //! The token allows to signal a cancellation request to one or more tasks. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">mod </span>guard; |
| <span class="kw">mod </span>tree_node; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::loom::sync::Arc; |
| <span class="kw">use </span>core::future::Future; |
| <span class="kw">use </span>core::pin::Pin; |
| <span class="kw">use </span>core::task::{Context, Poll}; |
| |
| <span class="kw">use </span>guard::DropGuard; |
| <span class="kw">use </span>pin_project_lite::pin_project; |
| |
| <span class="doccomment">/// A token which can be used to signal a cancellation request to one or more |
| /// tasks. |
| /// |
| /// Tasks can call [`CancellationToken::cancelled()`] in order to |
| /// obtain a Future which will be resolved when cancellation is requested. |
| /// |
| /// Cancellation can be requested through the [`CancellationToken::cancel`] method. |
| /// |
| /// # Examples |
| /// |
| /// ```no_run |
| /// use tokio::select; |
| /// use tokio_util::sync::CancellationToken; |
| /// |
| /// #[tokio::main] |
| /// async fn main() { |
| /// let token = CancellationToken::new(); |
| /// let cloned_token = token.clone(); |
| /// |
| /// let join_handle = tokio::spawn(async move { |
| /// // Wait for either cancellation or a very long time |
| /// select! { |
| /// _ = cloned_token.cancelled() => { |
| /// // The token was cancelled |
| /// 5 |
| /// } |
| /// _ = tokio::time::sleep(std::time::Duration::from_secs(9999)) => { |
| /// 99 |
| /// } |
| /// } |
| /// }); |
| /// |
| /// tokio::spawn(async move { |
| /// tokio::time::sleep(std::time::Duration::from_millis(10)).await; |
| /// token.cancel(); |
| /// }); |
| /// |
| /// assert_eq!(5, join_handle.await.unwrap()); |
| /// } |
| /// ``` |
| </span><span class="kw">pub struct </span>CancellationToken { |
| inner: Arc<tree_node::TreeNode>, |
| } |
| |
| <span class="kw">impl </span>std::panic::UnwindSafe <span class="kw">for </span>CancellationToken {} |
| <span class="kw">impl </span>std::panic::RefUnwindSafe <span class="kw">for </span>CancellationToken {} |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// A Future that is resolved once the corresponding [`CancellationToken`] |
| /// is cancelled. |
| </span><span class="attribute">#[must_use = <span class="string">"futures do nothing unless polled"</span>] |
| </span><span class="kw">pub struct </span>WaitForCancellationFuture<<span class="lifetime">'a</span>> { |
| cancellation_token: <span class="kw-2">&</span><span class="lifetime">'a </span>CancellationToken, |
| <span class="attribute">#[pin] |
| </span>future: tokio::sync::futures::Notified<<span class="lifetime">'a</span>>, |
| } |
| } |
| |
| <span class="macro">pin_project! </span>{ |
| <span class="doccomment">/// A Future that is resolved once the corresponding [`CancellationToken`] |
| /// is cancelled. |
| /// |
| /// This is the counterpart to [`WaitForCancellationFuture`] that takes |
| /// [`CancellationToken`] by value instead of using a reference. |
| </span><span class="attribute">#[must_use = <span class="string">"futures do nothing unless polled"</span>] |
| </span><span class="kw">pub struct </span>WaitForCancellationFutureOwned { |
| <span class="comment">// Since `future` is the first field, it is dropped before the |
| // cancellation_token field. This ensures that the reference inside the |
| // `Notified` remains valid. |
| </span><span class="attribute">#[pin] |
| </span>future: tokio::sync::futures::Notified<<span class="lifetime">'static</span>>, |
| cancellation_token: CancellationToken, |
| } |
| } |
| |
| <span class="comment">// ===== impl CancellationToken ===== |
| |
| </span><span class="kw">impl </span>core::fmt::Debug <span class="kw">for </span>CancellationToken { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>core::fmt::Formatter<<span class="lifetime">'_</span>>) -> core::fmt::Result { |
| f.debug_struct(<span class="string">"CancellationToken"</span>) |
| .field(<span class="string">"is_cancelled"</span>, <span class="kw-2">&</span><span class="self">self</span>.is_cancelled()) |
| .finish() |
| } |
| } |
| |
| <span class="kw">impl </span>Clone <span class="kw">for </span>CancellationToken { |
| <span class="doccomment">/// Creates a clone of the `CancellationToken` which will get cancelled |
| /// whenever the current token gets cancelled, and vice versa. |
| </span><span class="kw">fn </span>clone(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="self">Self </span>{ |
| tree_node::increase_handle_refcount(<span class="kw-2">&</span><span class="self">self</span>.inner); |
| CancellationToken { |
| inner: <span class="self">self</span>.inner.clone(), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>CancellationToken { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| tree_node::decrease_handle_refcount(<span class="kw-2">&</span><span class="self">self</span>.inner); |
| } |
| } |
| |
| <span class="kw">impl </span>Default <span class="kw">for </span>CancellationToken { |
| <span class="kw">fn </span>default() -> CancellationToken { |
| CancellationToken::new() |
| } |
| } |
| |
| <span class="kw">impl </span>CancellationToken { |
| <span class="doccomment">/// Creates a new CancellationToken in the non-cancelled state. |
| </span><span class="kw">pub fn </span>new() -> CancellationToken { |
| CancellationToken { |
| inner: Arc::new(tree_node::TreeNode::new()), |
| } |
| } |
| |
| <span class="doccomment">/// Creates a `CancellationToken` which will get cancelled whenever the |
| /// current token gets cancelled. Unlike a cloned `CancellationToken`, |
| /// cancelling a child token does not cancel the parent token. |
| /// |
| /// If the current token is already cancelled, the child token will get |
| /// returned in cancelled state. |
| /// |
| /// # Examples |
| /// |
| /// ```no_run |
| /// use tokio::select; |
| /// use tokio_util::sync::CancellationToken; |
| /// |
| /// #[tokio::main] |
| /// async fn main() { |
| /// let token = CancellationToken::new(); |
| /// let child_token = token.child_token(); |
| /// |
| /// let join_handle = tokio::spawn(async move { |
| /// // Wait for either cancellation or a very long time |
| /// select! { |
| /// _ = child_token.cancelled() => { |
| /// // The token was cancelled |
| /// 5 |
| /// } |
| /// _ = tokio::time::sleep(std::time::Duration::from_secs(9999)) => { |
| /// 99 |
| /// } |
| /// } |
| /// }); |
| /// |
| /// tokio::spawn(async move { |
| /// tokio::time::sleep(std::time::Duration::from_millis(10)).await; |
| /// token.cancel(); |
| /// }); |
| /// |
| /// assert_eq!(5, join_handle.await.unwrap()); |
| /// } |
| /// ``` |
| </span><span class="kw">pub fn </span>child_token(<span class="kw-2">&</span><span class="self">self</span>) -> CancellationToken { |
| CancellationToken { |
| inner: tree_node::child_node(<span class="kw-2">&</span><span class="self">self</span>.inner), |
| } |
| } |
| |
| <span class="doccomment">/// Cancel the [`CancellationToken`] and all child tokens which had been |
| /// derived from it. |
| /// |
| /// This will wake up all tasks which are waiting for cancellation. |
| /// |
| /// Be aware that cancellation is not an atomic operation. It is possible |
| /// for another thread running in parallel with a call to `cancel` to first |
| /// receive `true` from `is_cancelled` on one child node, and then receive |
| /// `false` from `is_cancelled` on another child node. However, once the |
| /// call to `cancel` returns, all child nodes have been fully cancelled. |
| </span><span class="kw">pub fn </span>cancel(<span class="kw-2">&</span><span class="self">self</span>) { |
| tree_node::cancel(<span class="kw-2">&</span><span class="self">self</span>.inner); |
| } |
| |
| <span class="doccomment">/// Returns `true` if the `CancellationToken` is cancelled. |
| </span><span class="kw">pub fn </span>is_cancelled(<span class="kw-2">&</span><span class="self">self</span>) -> bool { |
| tree_node::is_cancelled(<span class="kw-2">&</span><span class="self">self</span>.inner) |
| } |
| |
| <span class="doccomment">/// Returns a `Future` that gets fulfilled when cancellation is requested. |
| /// |
| /// The future will complete immediately if the token is already cancelled |
| /// when this method is called. |
| /// |
| /// # Cancel safety |
| /// |
| /// This method is cancel safe. |
| </span><span class="kw">pub fn </span>cancelled(<span class="kw-2">&</span><span class="self">self</span>) -> WaitForCancellationFuture<<span class="lifetime">'_</span>> { |
| WaitForCancellationFuture { |
| cancellation_token: <span class="self">self</span>, |
| future: <span class="self">self</span>.inner.notified(), |
| } |
| } |
| |
| <span class="doccomment">/// Returns a `Future` that gets fulfilled when cancellation is requested. |
| /// |
| /// The future will complete immediately if the token is already cancelled |
| /// when this method is called. |
| /// |
| /// The function takes self by value and returns a future that owns the |
| /// token. |
| /// |
| /// # Cancel safety |
| /// |
| /// This method is cancel safe. |
| </span><span class="kw">pub fn </span>cancelled_owned(<span class="self">self</span>) -> WaitForCancellationFutureOwned { |
| WaitForCancellationFutureOwned::new(<span class="self">self</span>) |
| } |
| |
| <span class="doccomment">/// Creates a `DropGuard` for this token. |
| /// |
| /// Returned guard will cancel this token (and all its children) on drop |
| /// unless disarmed. |
| </span><span class="kw">pub fn </span>drop_guard(<span class="self">self</span>) -> DropGuard { |
| DropGuard { inner: <span class="prelude-val">Some</span>(<span class="self">self</span>) } |
| } |
| } |
| |
| <span class="comment">// ===== impl WaitForCancellationFuture ===== |
| |
| </span><span class="kw">impl</span><<span class="lifetime">'a</span>> core::fmt::Debug <span class="kw">for </span>WaitForCancellationFuture<<span class="lifetime">'a</span>> { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>core::fmt::Formatter<<span class="lifetime">'_</span>>) -> core::fmt::Result { |
| f.debug_struct(<span class="string">"WaitForCancellationFuture"</span>).finish() |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> Future <span class="kw">for </span>WaitForCancellationFuture<<span class="lifetime">'a</span>> { |
| <span class="kw">type </span>Output = (); |
| |
| <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="kw">let </span><span class="kw-2">mut </span>this = <span class="self">self</span>.project(); |
| <span class="kw">loop </span>{ |
| <span class="kw">if </span>this.cancellation_token.is_cancelled() { |
| <span class="kw">return </span>Poll::Ready(()); |
| } |
| |
| <span class="comment">// No wakeups can be lost here because there is always a call to |
| // `is_cancelled` between the creation of the future and the call to |
| // `poll`, and the code that sets the cancelled flag does so before |
| // waking the `Notified`. |
| </span><span class="kw">if </span>this.future.as_mut().poll(cx).is_pending() { |
| <span class="kw">return </span>Poll::Pending; |
| } |
| |
| this.future.set(this.cancellation_token.inner.notified()); |
| } |
| } |
| } |
| |
| <span class="comment">// ===== impl WaitForCancellationFutureOwned ===== |
| |
| </span><span class="kw">impl </span>core::fmt::Debug <span class="kw">for </span>WaitForCancellationFutureOwned { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>core::fmt::Formatter<<span class="lifetime">'_</span>>) -> core::fmt::Result { |
| f.debug_struct(<span class="string">"WaitForCancellationFutureOwned"</span>).finish() |
| } |
| } |
| |
| <span class="kw">impl </span>WaitForCancellationFutureOwned { |
| <span class="kw">fn </span>new(cancellation_token: CancellationToken) -> <span class="self">Self </span>{ |
| WaitForCancellationFutureOwned { |
| <span class="comment">// cancellation_token holds a heap allocation and is guaranteed to have a |
| // stable deref, thus it would be ok to move the cancellation_token while |
| // the future holds a reference to it. |
| // |
| // # Safety |
| // |
| // cancellation_token is dropped after future due to the field ordering. |
| </span>future: <span class="kw">unsafe </span>{ <span class="self">Self</span>::new_future(<span class="kw-2">&</span>cancellation_token) }, |
| cancellation_token, |
| } |
| } |
| |
| <span class="doccomment">/// # Safety |
| /// The returned future must be destroyed before the cancellation token is |
| /// destroyed. |
| </span><span class="kw">unsafe fn </span>new_future( |
| cancellation_token: <span class="kw-2">&</span>CancellationToken, |
| ) -> tokio::sync::futures::Notified<<span class="lifetime">'static</span>> { |
| <span class="kw">let </span>inner_ptr = Arc::as_ptr(<span class="kw-2">&</span>cancellation_token.inner); |
| <span class="comment">// SAFETY: The `Arc::as_ptr` method guarantees that `inner_ptr` remains |
| // valid until the strong count of the Arc drops to zero, and the caller |
| // guarantees that they will drop the future before that happens. |
| </span>(<span class="kw-2">*</span>inner_ptr).notified() |
| } |
| } |
| |
| <span class="kw">impl </span>Future <span class="kw">for </span>WaitForCancellationFutureOwned { |
| <span class="kw">type </span>Output = (); |
| |
| <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="kw">let </span><span class="kw-2">mut </span>this = <span class="self">self</span>.project(); |
| |
| <span class="kw">loop </span>{ |
| <span class="kw">if </span>this.cancellation_token.is_cancelled() { |
| <span class="kw">return </span>Poll::Ready(()); |
| } |
| |
| <span class="comment">// No wakeups can be lost here because there is always a call to |
| // `is_cancelled` between the creation of the future and the call to |
| // `poll`, and the code that sets the cancelled flag does so before |
| // waking the `Notified`. |
| </span><span class="kw">if </span>this.future.as_mut().poll(cx).is_pending() { |
| <span class="kw">return </span>Poll::Pending; |
| } |
| |
| <span class="comment">// # Safety |
| // |
| // cancellation_token is dropped after future due to the field ordering. |
| </span>this.future |
| .set(<span class="kw">unsafe </span>{ <span class="self">Self</span>::new_future(this.cancellation_token) }); |
| } |
| } |
| } |
| </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> |
