| <!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/futures-channel-0.3.28/src/lock.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lock.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="../../futures_channel/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="../../futures_channel/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> |
| <span id="2">2</span> |
| <span id="3">3</span> |
| <span id="4">4</span> |
| <span id="5">5</span> |
| <span id="6">6</span> |
| <span id="7">7</span> |
| <span id="8">8</span> |
| <span id="9">9</span> |
| <span id="10">10</span> |
| <span id="11">11</span> |
| <span id="12">12</span> |
| <span id="13">13</span> |
| <span id="14">14</span> |
| <span id="15">15</span> |
| <span id="16">16</span> |
| <span id="17">17</span> |
| <span id="18">18</span> |
| <span id="19">19</span> |
| <span id="20">20</span> |
| <span id="21">21</span> |
| <span id="22">22</span> |
| <span id="23">23</span> |
| <span id="24">24</span> |
| <span id="25">25</span> |
| <span id="26">26</span> |
| <span id="27">27</span> |
| <span id="28">28</span> |
| <span id="29">29</span> |
| <span id="30">30</span> |
| <span id="31">31</span> |
| <span id="32">32</span> |
| <span id="33">33</span> |
| <span id="34">34</span> |
| <span id="35">35</span> |
| <span id="36">36</span> |
| <span id="37">37</span> |
| <span id="38">38</span> |
| <span id="39">39</span> |
| <span id="40">40</span> |
| <span id="41">41</span> |
| <span id="42">42</span> |
| <span id="43">43</span> |
| <span id="44">44</span> |
| <span id="45">45</span> |
| <span id="46">46</span> |
| <span id="47">47</span> |
| <span id="48">48</span> |
| <span id="49">49</span> |
| <span id="50">50</span> |
| <span id="51">51</span> |
| <span id="52">52</span> |
| <span id="53">53</span> |
| <span id="54">54</span> |
| <span id="55">55</span> |
| <span id="56">56</span> |
| <span id="57">57</span> |
| <span id="58">58</span> |
| <span id="59">59</span> |
| <span id="60">60</span> |
| <span id="61">61</span> |
| <span id="62">62</span> |
| <span id="63">63</span> |
| <span id="64">64</span> |
| <span id="65">65</span> |
| <span id="66">66</span> |
| <span id="67">67</span> |
| <span id="68">68</span> |
| <span id="69">69</span> |
| <span id="70">70</span> |
| <span id="71">71</span> |
| <span id="72">72</span> |
| <span id="73">73</span> |
| <span id="74">74</span> |
| <span id="75">75</span> |
| <span id="76">76</span> |
| <span id="77">77</span> |
| <span id="78">78</span> |
| <span id="79">79</span> |
| <span id="80">80</span> |
| <span id="81">81</span> |
| <span id="82">82</span> |
| <span id="83">83</span> |
| <span id="84">84</span> |
| <span id="85">85</span> |
| <span id="86">86</span> |
| <span id="87">87</span> |
| <span id="88">88</span> |
| <span id="89">89</span> |
| <span id="90">90</span> |
| <span id="91">91</span> |
| <span id="92">92</span> |
| <span id="93">93</span> |
| <span id="94">94</span> |
| <span id="95">95</span> |
| <span id="96">96</span> |
| <span id="97">97</span> |
| <span id="98">98</span> |
| <span id="99">99</span> |
| <span id="100">100</span> |
| <span id="101">101</span> |
| <span id="102">102</span> |
| </pre><pre class="rust"><code><span class="doccomment">//! A "mutex" which only supports `try_lock` |
| //! |
| //! As a futures library the eventual call to an event loop should be the only |
| //! thing that ever blocks, so this is assisted with a fast user-space |
| //! implementation of a lock that can only have a `try_lock` operation. |
| |
| </span><span class="kw">use </span>core::cell::UnsafeCell; |
| <span class="kw">use </span>core::ops::{Deref, DerefMut}; |
| <span class="kw">use </span>core::sync::atomic::AtomicBool; |
| <span class="kw">use </span>core::sync::atomic::Ordering::SeqCst; |
| |
| <span class="doccomment">/// A "mutex" around a value, similar to `std::sync::Mutex<T>`. |
| /// |
| /// This lock only supports the `try_lock` operation, however, and does not |
| /// implement poisoning. |
| </span><span class="attribute">#[derive(Debug)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Lock<T> { |
| locked: AtomicBool, |
| data: UnsafeCell<T>, |
| } |
| |
| <span class="doccomment">/// Sentinel representing an acquired lock through which the data can be |
| /// accessed. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>TryLock<<span class="lifetime">'a</span>, T> { |
| __ptr: <span class="kw-2">&</span><span class="lifetime">'a </span>Lock<T>, |
| } |
| |
| <span class="comment">// The `Lock` structure is basically just a `Mutex<T>`, and these two impls are |
| // intended to mirror the standard library's corresponding impls for `Mutex<T>`. |
| // |
| // If a `T` is sendable across threads, so is the lock, and `T` must be sendable |
| // across threads to be `Sync` because it allows mutable access from multiple |
| // threads. |
| </span><span class="kw">unsafe impl</span><T: Send> Send <span class="kw">for </span>Lock<T> {} |
| <span class="kw">unsafe impl</span><T: Send> Sync <span class="kw">for </span>Lock<T> {} |
| |
| <span class="kw">impl</span><T> Lock<T> { |
| <span class="doccomment">/// Creates a new lock around the given value. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>new(t: T) -> <span class="self">Self </span>{ |
| <span class="self">Self </span>{ locked: AtomicBool::new(<span class="bool-val">false</span>), data: UnsafeCell::new(t) } |
| } |
| |
| <span class="doccomment">/// Attempts to acquire this lock, returning whether the lock was acquired or |
| /// not. |
| /// |
| /// If `Some` is returned then the data this lock protects can be accessed |
| /// through the sentinel. This sentinel allows both mutable and immutable |
| /// access. |
| /// |
| /// If `None` is returned then the lock is already locked, either elsewhere |
| /// on this thread or on another thread. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>try_lock(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Option</span><TryLock<<span class="lifetime">'_</span>, T>> { |
| <span class="kw">if </span>!<span class="self">self</span>.locked.swap(<span class="bool-val">true</span>, SeqCst) { |
| <span class="prelude-val">Some</span>(TryLock { __ptr: <span class="self">self </span>}) |
| } <span class="kw">else </span>{ |
| <span class="prelude-val">None |
| </span>} |
| } |
| } |
| |
| <span class="kw">impl</span><T> Deref <span class="kw">for </span>TryLock<<span class="lifetime">'_</span>, T> { |
| <span class="kw">type </span>Target = T; |
| <span class="kw">fn </span>deref(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="kw-2">&</span>T { |
| <span class="comment">// The existence of `TryLock` represents that we own the lock, so we |
| // can safely access the data here. |
| </span><span class="kw">unsafe </span>{ <span class="kw-2">&*</span><span class="self">self</span>.__ptr.data.get() } |
| } |
| } |
| |
| <span class="kw">impl</span><T> DerefMut <span class="kw">for </span>TryLock<<span class="lifetime">'_</span>, T> { |
| <span class="kw">fn </span>deref_mut(<span class="kw-2">&mut </span><span class="self">self</span>) -> <span class="kw-2">&mut </span>T { |
| <span class="comment">// The existence of `TryLock` represents that we own the lock, so we |
| // can safely access the data here. |
| // |
| // Additionally, we're the *only* `TryLock` in existence so mutable |
| // access should be ok. |
| </span><span class="kw">unsafe </span>{ <span class="kw-2">&mut *</span><span class="self">self</span>.__ptr.data.get() } |
| } |
| } |
| |
| <span class="kw">impl</span><T> Drop <span class="kw">for </span>TryLock<<span class="lifetime">'_</span>, T> { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="self">self</span>.__ptr.locked.store(<span class="bool-val">false</span>, SeqCst); |
| } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span><span class="kw">super</span>::Lock; |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>smoke() { |
| <span class="kw">let </span>a = Lock::new(<span class="number">1</span>); |
| <span class="kw">let </span><span class="kw-2">mut </span>a1 = a.try_lock().unwrap(); |
| <span class="macro">assert!</span>(a.try_lock().is_none()); |
| <span class="macro">assert_eq!</span>(<span class="kw-2">*</span>a1, <span class="number">1</span>); |
| <span class="kw-2">*</span>a1 = <span class="number">2</span>; |
| drop(a1); |
| <span class="macro">assert_eq!</span>(<span class="kw-2">*</span>a.try_lock().unwrap(), <span class="number">2</span>); |
| <span class="macro">assert_eq!</span>(<span class="kw-2">*</span>a.try_lock().unwrap(), <span class="number">2</span>); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="futures_channel" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
