| <!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/signal-hook-0.1.17/src/flag.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>flag.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="../../signal_hook/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="../../signal_hook/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">//! Module for actions setting flags. |
| //! |
| //! This contains helper functions to set flags whenever a signal happens. The flags are atomic |
| //! bools or numbers and the library manipulates them with the `SeqCst` ordering, in case someone |
| //! cares about relative order to some *other* atomic variables. If you don't care about the |
| //! relative order, you are free to use `Ordering::Relaxed` when reading and resetting the flags. |
| //! |
| //! # When to use |
| //! |
| //! The flags in this module allow for polling if a signal arrived since the previous poll. The do |
| //! not allow blocking until something arrives. |
| //! |
| //! Therefore, the natural way to use them is in applications that have some kind of iterative work |
| //! with both some upper and lower time limit on one iteration. If one iteration could block for |
| //! arbitrary time, the handling of the signal would be postponed for a long time. If the iteration |
| //! didn't block at all, the checking for the signal would turn into a busy-loop. |
| //! |
| //! If what you need is blocking until a signal comes, you might find better tools in the |
| //! [`pipe`](../pipe/) and [`iterator`](../iterator/) modules. |
| //! |
| //! # Examples |
| //! |
| //! Doing something until terminated. This also knows by which signal it was terminated. In case |
| //! multiple termination signals arrive before it is handled, it recognizes the last one. |
| //! |
| //! ```rust |
| //! extern crate signal_hook; |
| //! |
| //! use std::io::Error; |
| //! use std::sync::Arc; |
| //! use std::sync::atomic::{AtomicUsize, Ordering}; |
| //! |
| //! use signal_hook::flag as signal_flag; |
| //! |
| //! fn main() -> Result<(), Error> { |
| //! let term = Arc::new(AtomicUsize::new(0)); |
| //! const SIGTERM: usize = signal_hook::SIGTERM as usize; |
| //! const SIGINT: usize = signal_hook::SIGINT as usize; |
| //! # #[cfg(not(windows))] |
| //! const SIGQUIT: usize = signal_hook::SIGQUIT as usize; |
| //! signal_flag::register_usize(signal_hook::SIGTERM, Arc::clone(&term), SIGTERM)?; |
| //! signal_flag::register_usize(signal_hook::SIGINT, Arc::clone(&term), SIGINT)?; |
| //! # #[cfg(not(windows))] |
| //! signal_flag::register_usize(signal_hook::SIGQUIT, Arc::clone(&term), SIGQUIT)?; |
| //! |
| //! # // Hack to terminate the example when run as a doc-test. |
| //! # term.store(SIGTERM, Ordering::Relaxed); |
| //! loop { |
| //! match term.load(Ordering::Relaxed) { |
| //! 0 => { |
| //! // Do some useful stuff here |
| //! } |
| //! SIGTERM => { |
| //! eprintln!("Terminating on the TERM signal"); |
| //! break; |
| //! } |
| //! SIGINT => { |
| //! eprintln!("Terminating on the INT signal"); |
| //! break; |
| //! } |
| //! # #[cfg(not(windows))] |
| //! SIGQUIT => { |
| //! eprintln!("Terminating on the QUIT signal"); |
| //! break; |
| //! } |
| //! _ => unreachable!(), |
| //! } |
| //! } |
| //! |
| //! Ok(()) |
| //! } |
| //! ``` |
| //! |
| //! Sending a signal to self and seeing it arrived (not of a practical usage on itself): |
| //! |
| //! ```rust |
| //! extern crate libc; |
| //! extern crate signal_hook; |
| //! |
| //! use std::io::Error; |
| //! use std::sync::Arc; |
| //! use std::sync::atomic::{AtomicBool, Ordering}; |
| //! use std::thread; |
| //! use std::time::Duration; |
| //! |
| //! fn main() -> Result<(), Error> { |
| //! let got = Arc::new(AtomicBool::new(false)); |
| //! # #[cfg(not(windows))] |
| //! signal_hook::flag::register(signal_hook::SIGUSR1, Arc::clone(&got))?; |
| //! # #[cfg(windows)] |
| //! # signal_hook::flag::register(signal_hook::SIGTERM, Arc::clone(&got))?; |
| //! unsafe { |
| //! # #[cfg(not(windows))] |
| //! libc::raise(signal_hook::SIGUSR1); |
| //! # #[cfg(windows)] |
| //! # libc::raise(signal_hook::SIGTERM); |
| //! } |
| //! // A sleep here, because it could run the signal handler in another thread and we may not |
| //! // see the flag right away. This is still a hack and not guaranteed to work, it is just an |
| //! // example! |
| //! thread::sleep(Duration::from_secs(1)); |
| //! assert!(got.load(Ordering::Relaxed)); |
| //! Ok(()) |
| //! } |
| //! ``` |
| //! |
| //! Reloading a configuration on `SIGHUP` (which is a common behaviour of many UNIX daemons, |
| //! together with reopening the log file). |
| //! |
| //! ```rust |
| //! extern crate signal_hook; |
| //! |
| //! use std::io::Error; |
| //! use std::sync::Arc; |
| //! use std::sync::atomic::{AtomicBool, Ordering}; |
| //! |
| //! use signal_hook::flag as signal_flag; |
| //! |
| //! fn main() -> Result<(), Error> { |
| //! // We start with true, to load the configuration in the very first iteration too. |
| //! let reload = Arc::new(AtomicBool::new(true)); |
| //! let term = Arc::new(AtomicBool::new(false)); |
| //! # #[cfg(not(windows))] |
| //! signal_flag::register(signal_hook::SIGHUP, Arc::clone(&reload))?; |
| //! signal_flag::register(signal_hook::SIGINT, Arc::clone(&term))?; |
| //! signal_flag::register(signal_hook::SIGTERM, Arc::clone(&term))?; |
| //! # #[cfg(not(windows))] |
| //! signal_flag::register(signal_hook::SIGQUIT, Arc::clone(&term))?; |
| //! while !term.load(Ordering::Relaxed) { |
| //! // Using swap here, not load, to reset it back to false once it is reloaded. |
| //! if reload.swap(false, Ordering::Relaxed) { |
| //! // Reload the config here |
| //! # |
| //! # // Hiden hack to make the example terminate when run as doc-test. Not part of the |
| //! # // real code. |
| //! # term.store(true, Ordering::Relaxed); |
| //! } |
| //! // Serve one request |
| //! } |
| //! Ok(()) |
| //! } |
| //! ``` |
| |
| </span><span class="kw">use </span>std::io::Error; |
| <span class="kw">use </span>std::sync::atomic::{AtomicBool, AtomicUsize, Ordering}; |
| <span class="kw">use </span>std::sync::Arc; |
| |
| <span class="kw">use </span>libc::c_int; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::SigId; |
| |
| <span class="doccomment">/// Registers an action to set the flag to `true` whenever the given signal arrives. |
| </span><span class="kw">pub fn </span>register(signal: c_int, flag: Arc<AtomicBool>) -> <span class="prelude-ty">Result</span><SigId, Error> { |
| <span class="comment">// We use SeqCst for two reasons: |
| // * Signals should not come very often, so the performance does not really matter. |
| // * We promise the order of actions, but setting different atomics with Relaxed or similar |
| // would not guarantee the effective order. |
| </span><span class="kw">unsafe </span>{ <span class="kw">crate</span>::register(signal, <span class="kw">move </span>|| flag.store(<span class="bool-val">true</span>, Ordering::SeqCst)) } |
| } |
| |
| <span class="doccomment">/// Registers an action to set the flag to the given value whenever the signal arrives. |
| </span><span class="kw">pub fn </span>register_usize(signal: c_int, flag: Arc<AtomicUsize>, value: usize) -> <span class="prelude-ty">Result</span><SigId, Error> { |
| <span class="kw">unsafe </span>{ <span class="kw">crate</span>::register(signal, <span class="kw">move </span>|| flag.store(value, Ordering::SeqCst)) } |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span>std::sync::atomic; |
| <span class="kw">use </span>std::time::{Duration, Instant}; |
| |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="kw">fn </span>self_signal() { |
| <span class="kw">unsafe </span>{ |
| <span class="attribute">#[cfg(not(windows))] |
| </span>libc::raise(<span class="kw">crate</span>::SIGUSR1); |
| <span class="attribute">#[cfg(windows)] |
| </span>libc::raise(<span class="kw">crate</span>::SIGTERM); |
| } |
| } |
| |
| <span class="kw">fn </span>wait_flag(flag: <span class="kw-2">&</span>AtomicBool) -> bool { |
| <span class="kw">let </span>start = Instant::now(); |
| <span class="kw">while </span>!flag.load(Ordering::Relaxed) { |
| atomic::spin_loop_hint(); |
| <span class="kw">if </span>Instant::now() - start > Duration::from_secs(<span class="number">1</span>) { |
| <span class="comment">// We reached a timeout and nothing happened yet. |
| // In theory, using timeouts for thread-synchronization tests is wrong, but a |
| // second should be enough in practice. |
| </span><span class="kw">return </span><span class="bool-val">false</span>; |
| } |
| } |
| <span class="bool-val">true |
| </span>} |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>register_unregister() { |
| <span class="comment">// When we register the action, it is active. |
| </span><span class="kw">let </span>flag = Arc::new(AtomicBool::new(<span class="bool-val">false</span>)); |
| <span class="attribute">#[cfg(not(windows))] |
| </span><span class="kw">let </span>signal = register(<span class="kw">crate</span>::SIGUSR1, Arc::clone(<span class="kw-2">&</span>flag)).unwrap(); |
| <span class="attribute">#[cfg(windows)] |
| </span><span class="kw">let </span>signal = register(<span class="kw">crate</span>::SIGTERM, Arc::clone(<span class="kw-2">&</span>flag)).unwrap(); |
| self_signal(); |
| <span class="macro">assert!</span>(wait_flag(<span class="kw-2">&</span>flag)); |
| <span class="comment">// But stops working after it is unregistered. |
| </span><span class="macro">assert!</span>(<span class="kw">crate</span>::unregister(signal)); |
| flag.store(<span class="bool-val">false</span>, Ordering::Relaxed); |
| self_signal(); |
| <span class="macro">assert!</span>(!wait_flag(<span class="kw-2">&</span>flag)); |
| <span class="comment">// And the unregistration actually dropped its copy of the Arc |
| </span><span class="macro">assert_eq!</span>(<span class="number">1</span>, Arc::strong_count(<span class="kw-2">&</span>flag)); |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../" data-current-crate="signal_hook" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
