| <!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/tracing-core-0.1.31/src/lazy.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>lazy.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="../../tracing_core/index.html"><div class="logo-container"> |
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| <img src="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png" 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="attribute">#[cfg(feature = <span class="string">"std"</span>)] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">use </span>once_cell::sync::Lazy; |
| |
| <span class="attribute">#[cfg(not(feature = <span class="string">"std"</span>))] |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">use </span><span class="self">self</span>::spin::Lazy; |
| |
| <span class="attribute">#[cfg(not(feature = <span class="string">"std"</span>))] |
| </span><span class="kw">mod </span>spin { |
| <span class="doccomment">//! This is the `once_cell::sync::Lazy` type, but modified to use our |
| //! `spin::Once` type rather than `OnceCell`. This is used to replace |
| //! `once_cell::sync::Lazy` on `no-std` builds. |
| </span><span class="kw">use </span><span class="kw">crate</span>::spin::Once; |
| <span class="kw">use </span>core::{cell::Cell, fmt, ops::Deref}; |
| |
| <span class="doccomment">/// Re-implementation of `once_cell::sync::Lazy` on top of `spin::Once` |
| /// rather than `OnceCell`. |
| /// |
| /// This is used when the standard library is disabled. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">struct </span>Lazy<T, F = <span class="kw">fn</span>() -> T> { |
| cell: Once<T>, |
| init: Cell<<span class="prelude-ty">Option</span><F>>, |
| } |
| |
| <span class="kw">impl</span><T: fmt::Debug, F> fmt::Debug <span class="kw">for </span>Lazy<T, F> { |
| <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 { |
| f.debug_struct(<span class="string">"Lazy"</span>) |
| .field(<span class="string">"cell"</span>, <span class="kw-2">&</span><span class="self">self</span>.cell) |
| .field(<span class="string">"init"</span>, <span class="kw-2">&</span><span class="string">".."</span>) |
| .finish() |
| } |
| } |
| |
| <span class="comment">// We never create a `&F` from a `&Lazy<T, F>` so it is fine to not impl |
| // `Sync` for `F`. We do create a `&mut Option<F>` in `force`, but this is |
| // properly synchronized, so it only happens once so it also does not |
| // contribute to this impl. |
| </span><span class="kw">unsafe impl</span><T, F: Send> Sync <span class="kw">for </span>Lazy<T, F> <span class="kw">where </span>Once<T>: Sync {} |
| <span class="comment">// auto-derived `Send` impl is OK. |
| |
| </span><span class="kw">impl</span><T, F> Lazy<T, F> { |
| <span class="doccomment">/// Creates a new lazy value with the given initializing function. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">const fn </span>new(init: F) -> Lazy<T, F> { |
| Lazy { |
| cell: Once::new(), |
| init: Cell::new(<span class="prelude-val">Some</span>(init)), |
| } |
| } |
| } |
| |
| <span class="kw">impl</span><T, F: FnOnce() -> T> Lazy<T, F> { |
| <span class="doccomment">/// Forces the evaluation of this lazy value and returns a reference to |
| /// the result. |
| /// |
| /// This is equivalent to the `Deref` impl, but is explicit. |
| </span><span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>force(this: <span class="kw-2">&</span>Lazy<T, F>) -> <span class="kw-2">&</span>T { |
| this.cell.call_once(|| <span class="kw">match </span>this.init.take() { |
| <span class="prelude-val">Some</span>(f) => f(), |
| <span class="prelude-val">None </span>=> <span class="macro">panic!</span>(<span class="string">"Lazy instance has previously been poisoned"</span>), |
| }) |
| } |
| } |
| |
| <span class="kw">impl</span><T, F: FnOnce() -> T> Deref <span class="kw">for </span>Lazy<T, F> { |
| <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 { |
| Lazy::force(<span class="self">self</span>) |
| } |
| } |
| |
| <span class="kw">impl</span><T: Default> Default <span class="kw">for </span>Lazy<T> { |
| <span class="doccomment">/// Creates a new lazy value using `Default` as the initializing function. |
| </span><span class="kw">fn </span>default() -> Lazy<T> { |
| Lazy::new(T::default) |
| } |
| } |
| } |
| </code></pre></div> |
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