| <!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/git/checkouts/tokio-377c595163f99a10/dfe252d/tokio/src/sync/rwlock/owned_read_guard.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>owned_read_guard.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/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/index.html"><img class="rust-logo" src="../../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">crate</span>::sync::rwlock::RwLock; |
| <span class="kw">use </span>std::fmt; |
| <span class="kw">use </span>std::marker::PhantomData; |
| <span class="kw">use </span>std::mem; |
| <span class="kw">use </span>std::mem::ManuallyDrop; |
| <span class="kw">use </span>std::ops; |
| <span class="kw">use </span>std::sync::Arc; |
| |
| <span class="doccomment">/// Owned RAII structure used to release the shared read access of a lock when |
| /// dropped. |
| /// |
| /// This structure is created by the [`read_owned`] method on |
| /// [`RwLock`]. |
| /// |
| /// [`read_owned`]: method@crate::sync::RwLock::read_owned |
| /// [`RwLock`]: struct@crate::sync::RwLock |
| </span><span class="kw">pub struct </span>OwnedRwLockReadGuard<T: <span class="question-mark">?</span>Sized, U: <span class="question-mark">?</span>Sized = T> { |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) resource_span: tracing::Span, |
| <span class="comment">// ManuallyDrop allows us to destructure into this field without running the destructor. |
| </span><span class="kw">pub</span>(<span class="kw">super</span>) lock: ManuallyDrop<Arc<RwLock<T>>>, |
| <span class="kw">pub</span>(<span class="kw">super</span>) data: <span class="kw-2">*const </span>U, |
| <span class="kw">pub</span>(<span class="kw">super</span>) _p: PhantomData<T>, |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized, U: <span class="question-mark">?</span>Sized> OwnedRwLockReadGuard<T, U> { |
| <span class="doccomment">/// Makes a new `OwnedRwLockReadGuard` for a component of the locked data. |
| /// This operation cannot fail as the `OwnedRwLockReadGuard` passed in |
| /// already locked the data. |
| /// |
| /// This is an associated function that needs to be |
| /// used as `OwnedRwLockReadGuard::map(...)`. A method would interfere with |
| /// methods of the same name on the contents of the locked data. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::sync::Arc; |
| /// use tokio::sync::{RwLock, OwnedRwLockReadGuard}; |
| /// |
| /// #[derive(Debug, Clone, Copy, PartialEq, Eq)] |
| /// struct Foo(u32); |
| /// |
| /// # #[tokio::main] |
| /// # async fn main() { |
| /// let lock = Arc::new(RwLock::new(Foo(1))); |
| /// |
| /// let guard = lock.read_owned().await; |
| /// let guard = OwnedRwLockReadGuard::map(guard, |f| &f.0); |
| /// |
| /// assert_eq!(1, *guard); |
| /// # } |
| /// ``` |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>map<F, V: <span class="question-mark">?</span>Sized>(<span class="kw-2">mut </span>this: <span class="self">Self</span>, f: F) -> OwnedRwLockReadGuard<T, V> |
| <span class="kw">where |
| </span>F: FnOnce(<span class="kw-2">&</span>U) -> <span class="kw-2">&</span>V, |
| { |
| <span class="kw">let </span>data = f(<span class="kw-2">&*</span>this) <span class="kw">as </span><span class="kw-2">*const </span>V; |
| <span class="kw">let </span>lock = <span class="kw">unsafe </span>{ ManuallyDrop::take(<span class="kw-2">&mut </span>this.lock) }; |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="kw">let </span>resource_span = this.resource_span.clone(); |
| <span class="comment">// NB: Forget to avoid drop impl from being called. |
| </span>mem::forget(this); |
| |
| OwnedRwLockReadGuard { |
| lock: ManuallyDrop::new(lock), |
| data, |
| _p: PhantomData, |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span>resource_span, |
| } |
| } |
| |
| <span class="doccomment">/// Attempts to make a new [`OwnedRwLockReadGuard`] for a component of the |
| /// locked data. The original guard is returned if the closure returns |
| /// `None`. |
| /// |
| /// This operation cannot fail as the `OwnedRwLockReadGuard` passed in |
| /// already locked the data. |
| /// |
| /// This is an associated function that needs to be used as |
| /// `OwnedRwLockReadGuard::try_map(..)`. A method would interfere with |
| /// methods of the same name on the contents of the locked data. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::sync::Arc; |
| /// use tokio::sync::{RwLock, OwnedRwLockReadGuard}; |
| /// |
| /// #[derive(Debug, Clone, Copy, PartialEq, Eq)] |
| /// struct Foo(u32); |
| /// |
| /// # #[tokio::main] |
| /// # async fn main() { |
| /// let lock = Arc::new(RwLock::new(Foo(1))); |
| /// |
| /// let guard = lock.read_owned().await; |
| /// let guard = OwnedRwLockReadGuard::try_map(guard, |f| Some(&f.0)).expect("should not fail"); |
| /// |
| /// assert_eq!(1, *guard); |
| /// # } |
| /// ``` |
| </span><span class="attribute">#[inline] |
| </span><span class="kw">pub fn </span>try_map<F, V: <span class="question-mark">?</span>Sized>(<span class="kw-2">mut </span>this: <span class="self">Self</span>, f: F) -> <span class="prelude-ty">Result</span><OwnedRwLockReadGuard<T, V>, <span class="self">Self</span>> |
| <span class="kw">where |
| </span>F: FnOnce(<span class="kw-2">&</span>U) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span>V>, |
| { |
| <span class="kw">let </span>data = <span class="kw">match </span>f(<span class="kw-2">&*</span>this) { |
| <span class="prelude-val">Some</span>(data) => data <span class="kw">as </span><span class="kw-2">*const </span>V, |
| <span class="prelude-val">None </span>=> <span class="kw">return </span><span class="prelude-val">Err</span>(this), |
| }; |
| <span class="kw">let </span>lock = <span class="kw">unsafe </span>{ ManuallyDrop::take(<span class="kw-2">&mut </span>this.lock) }; |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="kw">let </span>resource_span = this.resource_span.clone(); |
| <span class="comment">// NB: Forget to avoid drop impl from being called. |
| </span>mem::forget(this); |
| |
| <span class="prelude-val">Ok</span>(OwnedRwLockReadGuard { |
| lock: ManuallyDrop::new(lock), |
| data, |
| _p: PhantomData, |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span>resource_span, |
| }) |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized, U: <span class="question-mark">?</span>Sized> ops::Deref <span class="kw">for </span>OwnedRwLockReadGuard<T, U> { |
| <span class="kw">type </span>Target = U; |
| |
| <span class="kw">fn </span>deref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>U { |
| <span class="kw">unsafe </span>{ <span class="kw-2">&*</span><span class="self">self</span>.data } |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized, U: <span class="question-mark">?</span>Sized> fmt::Debug <span class="kw">for </span>OwnedRwLockReadGuard<T, U> |
| <span class="kw">where |
| </span>U: fmt::Debug, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| fmt::Debug::fmt(<span class="kw-2">&**</span><span class="self">self</span>, f) |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized, U: <span class="question-mark">?</span>Sized> fmt::Display <span class="kw">for </span>OwnedRwLockReadGuard<T, U> |
| <span class="kw">where |
| </span>U: fmt::Display, |
| { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result { |
| fmt::Display::fmt(<span class="kw-2">&**</span><span class="self">self</span>, f) |
| } |
| } |
| |
| <span class="kw">impl</span><T: <span class="question-mark">?</span>Sized, U: <span class="question-mark">?</span>Sized> Drop <span class="kw">for </span>OwnedRwLockReadGuard<T, U> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.lock.s.release(<span class="number">1</span>); |
| <span class="kw">unsafe </span>{ ManuallyDrop::drop(<span class="kw-2">&mut </span><span class="self">self</span>.lock) }; |
| |
| <span class="attribute">#[cfg(all(tokio_unstable, feature = <span class="string">"tracing"</span>))] |
| </span><span class="self">self</span>.resource_span.in_scope(|| { |
| <span class="macro">tracing::trace!</span>( |
| target: <span class="string">"runtime::resource::state_update"</span>, |
| current_readers = <span class="number">1</span>, |
| current_readers.op = <span class="string">"sub"</span>, |
| ) |
| }); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../../" data-current-crate="tokio" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |