| <!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/pipe.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>pipe.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 with the self-pipe pattern. |
| //! |
| //! One of the common patterns around signals is to have a pipe with both ends in the same program. |
| //! Whenever there's a signal, the signal handler writes one byte of garbage data to the write end, |
| //! unless the pipe's already full. The application then can handle the read end. |
| //! |
| //! This has two advantages. First, the real signal action moves outside of the signal handler |
| //! where there are a lot less restrictions. Second, it fits nicely in all kinds of asynchronous |
| //! loops and has less chance of race conditions. |
| //! |
| //! This module offers premade functions for the write end (and doesn't insist that it must be a |
| //! pipe ‒ anything that can be written to is fine ‒ sockets too, therefore `UnixStream::pair` is a |
| //! good candidate). |
| //! |
| //! If you want to integrate with some asynchronous library, plugging streams from `mio-uds` or |
| //! `tokio-uds` libraries should work. |
| //! |
| //! If it looks too low-level for your needs, the [`iterator`](../iterator/) module contains some |
| //! higher-lever interface that also uses a self-pipe pattern under the hood. |
| //! |
| //! # Correct order of handling |
| //! |
| //! A care needs to be taken to avoid race conditions, especially when handling the same signal in |
| //! a loop. Specifically, another signal might come when the action for the previous signal is |
| //! being taken. The correct order is first to clear the content of the pipe (read some/all data |
| //! from it) and then take the action. This way a spurious wakeup can happen (the pipe could wake |
| //! up even when no signal came after the signal was taken, because ‒ it arrived between cleaning |
| //! the pipe and taking the action). Note that some OS primitives (eg. `select`) suffer from |
| //! spurious wakeups themselves (they can claim a FD is readable when it is not true) and blocking |
| //! `read` might return prematurely (with eg. `EINTR`). |
| //! |
| //! The reverse order of first taking the action and then clearing the pipe might lose signals, |
| //! which is usually worse. |
| //! |
| //! This is not a problem with blocking on reading from the pipe (because both the blocking and |
| //! cleaning is the same action), but in case of asynchronous handling it matters. |
| //! |
| //! If you want to combine setting some flags with a self-pipe pattern, the flag needs to be set |
| //! first, then the pipe written. On the read end, first the pipe needs to be cleaned, then the |
| //! flag and then the action taken. This is what the [`Signals`](../iterator/struct.Signals.html) |
| //! structure does internally. |
| //! |
| //! # Write collating |
| //! |
| //! While unlikely if handled correctly, it is possible the write end is full when a signal comes. |
| //! In such case the signal handler simply does nothing. If the write end is full, the read end is |
| //! readable and therefore will wake up. On the other hand, blocking in the signal handler would |
| //! definitely be a bad idea. |
| //! |
| //! However, this also means the number of bytes read from the end might be lower than the number |
| //! of signals that arrived. This should not generally be a problem, since the OS already collates |
| //! signals of the same kind together. |
| //! |
| //! # Examples |
| //! |
| //! This example waits for at last one `SIGUSR1` signal to come before continuing (and |
| //! terminating). It sends the signal to itself, so it correctly terminates. |
| //! |
| //! ```rust |
| //! extern crate libc; |
| //! extern crate signal_hook; |
| //! |
| //! use std::io::{Error, Read}; |
| //! use std::os::unix::net::UnixStream; |
| //! |
| //! fn main() -> Result<(), Error> { |
| //! let (mut read, write) = UnixStream::pair()?; |
| //! signal_hook::pipe::register(signal_hook::SIGUSR1, write)?; |
| //! // This will write into the pipe write end through the signal handler |
| //! unsafe { libc::raise(signal_hook::SIGUSR1) }; |
| //! let mut buff = [0]; |
| //! read.read_exact(&mut buff)?; |
| //! println!("Happily terminating"); |
| //! Ok(()) |
| //! } |
| |
| </span><span class="kw">use </span>std::io::Error; |
| <span class="kw">use </span>std::os::unix::io::{AsRawFd, RawFd}; |
| |
| <span class="kw">use </span>libc::{<span class="self">self</span>, c_int}; |
| |
| <span class="kw">use </span><span class="kw">crate</span>::SigId; |
| |
| <span class="kw">struct </span>OwnedFd(RawFd); |
| |
| <span class="kw">impl </span>OwnedFd { |
| <span class="doccomment">/// Sets close on exec and nonblock on the inner file descriptor. |
| </span><span class="kw">fn </span>set_flags(<span class="kw-2">&</span><span class="self">self</span>) -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">unsafe </span>{ |
| <span class="kw">let </span>flags = libc::fcntl(<span class="self">self</span>.as_raw_fd(), libc::F_GETFL, <span class="number">0</span>); |
| <span class="kw">if </span>flags == -<span class="number">1 </span>{ |
| <span class="kw">return </span><span class="prelude-val">Err</span>(Error::last_os_error()); |
| } |
| <span class="kw">let </span>flags = flags | libc::O_NONBLOCK | libc::O_CLOEXEC; |
| <span class="kw">if </span>libc::fcntl(<span class="self">self</span>.as_raw_fd(), libc::F_SETFL, flags) == -<span class="number">1 </span>{ |
| <span class="kw">return </span><span class="prelude-val">Err</span>(Error::last_os_error()); |
| } |
| } |
| <span class="prelude-val">Ok</span>(()) |
| } |
| } |
| |
| <span class="kw">impl </span>AsRawFd <span class="kw">for </span>OwnedFd { |
| <span class="kw">fn </span>as_raw_fd(<span class="kw-2">&</span><span class="self">self</span>) -> RawFd { |
| <span class="self">self</span>.<span class="number">0 |
| </span>} |
| } |
| |
| <span class="kw">impl </span>Drop <span class="kw">for </span>OwnedFd { |
| <span class="kw">fn </span>drop(<span class="kw-2">&mut </span><span class="self">self</span>) { |
| <span class="kw">unsafe </span>{ |
| libc::close(<span class="self">self</span>.<span class="number">0</span>); |
| } |
| } |
| } |
| |
| <span class="kw">pub</span>(<span class="kw">crate</span>) <span class="kw">fn </span>wake(pipe: RawFd) { |
| <span class="kw">unsafe </span>{ |
| <span class="comment">// This writes some data into the pipe. |
| // |
| // There are two tricks: |
| // * First, the crazy cast. The first part turns reference into pointer. The second part |
| // turns pointer to u8 into a pointer to void, which is what write requires. |
| // * Second, we ignore errors, on purpose. We don't have any means to handling them. The |
| // two conceivable errors are EBADFD, if someone passes a non-existent file descriptor or |
| // if it is closed. The second is EAGAIN, in which case the pipe is full ‒ there were |
| // many signals, but the reader didn't have time to read the data yet. It'll still get |
| // woken up, so not fitting another letter in it is fine. |
| </span>libc::write(pipe, <span class="string">b"X" </span><span class="kw">as </span><span class="kw-2">*const </span><span class="kw">_ as </span><span class="kw-2">*const </span><span class="kw">_</span>, <span class="number">1</span>); |
| } |
| } |
| |
| <span class="doccomment">/// Registers a write to a self-pipe whenever there's the signal. |
| /// |
| /// In this case, the pipe is taken as the `RawFd`. It is still the caller's responsibility to |
| /// close it. |
| /// |
| /// Note that passing the wrong file descriptor won't cause UB, but can still lead to severe bugs ‒ |
| /// like data corruptions in files. |
| </span><span class="kw">pub fn </span>register_raw(signal: c_int, pipe: RawFd) -> <span class="prelude-ty">Result</span><SigId, Error> { |
| <span class="comment">// A trick here: |
| // We want to set the FD non-blocking. But it belongs to the caller. Therefore, we make our own |
| // copy with `dup` to play on instead. |
| </span><span class="kw">let </span>duped = <span class="kw">unsafe </span>{ libc::dup(pipe) }; |
| <span class="kw">if </span>duped == -<span class="number">1 </span>{ |
| <span class="kw">return </span><span class="prelude-val">Err</span>(Error::last_os_error()); |
| } |
| <span class="kw">let </span>duped = OwnedFd(duped); |
| duped.set_flags()<span class="question-mark">?</span>; |
| <span class="kw">let </span>action = <span class="kw">move </span>|| wake(duped.as_raw_fd()); |
| <span class="kw">unsafe </span>{ <span class="kw">crate</span>::register(signal, action) } |
| } |
| |
| <span class="doccomment">/// Registers a write to a self-pipe whenever there's the signal. |
| /// |
| /// The ownership of pipe is taken and will be closed whenever the created action is unregistered. |
| /// |
| /// Note that if you want to register the same pipe for multiple signals, there's `try_clone` |
| /// method on many unix socket primitives. |
| </span><span class="kw">pub fn </span>register<P>(signal: c_int, pipe: P) -> <span class="prelude-ty">Result</span><SigId, Error> |
| <span class="kw">where |
| </span>P: AsRawFd + Send + Sync + <span class="lifetime">'static</span>, |
| { |
| <span class="kw">let </span>id = register_raw(signal, pipe.as_raw_fd())<span class="question-mark">?</span>; |
| <span class="comment">// Close the original |
| </span>drop(pipe); |
| <span class="prelude-val">Ok</span>(id) |
| } |
| |
| <span class="attribute">#[cfg(test)] |
| </span><span class="kw">mod </span>tests { |
| <span class="kw">use </span>std::io::Read; |
| <span class="kw">use </span>std::os::unix::net::{UnixDatagram, UnixStream}; |
| |
| <span class="kw">use super</span>::<span class="kw-2">*</span>; |
| |
| <span class="comment">// Note: multiple tests share the SIGUSR1 signal. This is fine, we only need to know the signal |
| // arrives. It's OK to arrive multiple times, from multiple tests. |
| </span><span class="kw">fn </span>wakeup() { |
| <span class="kw">unsafe </span>{ <span class="macro">assert_eq!</span>(<span class="number">0</span>, libc::raise(libc::SIGUSR1)) } |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>register_with_socket() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">let </span>(<span class="kw-2">mut </span>read, write) = UnixStream::pair()<span class="question-mark">?</span>; |
| register(libc::SIGUSR1, write)<span class="question-mark">?</span>; |
| read.set_nonblocking(<span class="bool-val">true</span>)<span class="question-mark">?</span>; |
| wakeup(); |
| <span class="kw">let </span><span class="kw-2">mut </span>buff = [<span class="number">0</span>; <span class="number">1</span>]; |
| read.read_exact(<span class="kw-2">&mut </span>buff)<span class="question-mark">?</span>; |
| <span class="macro">assert_eq!</span>(<span class="string">b"X"</span>, <span class="kw-2">&</span>buff); |
| <span class="prelude-val">Ok</span>(()) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>register_dgram_socket() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">let </span>(read, write) = UnixDatagram::pair()<span class="question-mark">?</span>; |
| register(libc::SIGUSR1, write)<span class="question-mark">?</span>; |
| read.set_nonblocking(<span class="bool-val">true</span>)<span class="question-mark">?</span>; |
| wakeup(); |
| <span class="kw">let </span><span class="kw-2">mut </span>buff = [<span class="number">0</span>; <span class="number">1</span>]; |
| read.recv(<span class="kw-2">&mut </span>buff)<span class="question-mark">?</span>; |
| <span class="macro">assert_eq!</span>(<span class="string">b"X"</span>, <span class="kw-2">&</span>buff); |
| <span class="prelude-val">Ok</span>(()) |
| } |
| |
| <span class="attribute">#[test] |
| </span><span class="kw">fn </span>register_with_pipe() -> <span class="prelude-ty">Result</span><(), Error> { |
| <span class="kw">let </span><span class="kw-2">mut </span>fds = [<span class="number">0</span>; <span class="number">2</span>]; |
| <span class="kw">unsafe </span>{ <span class="macro">assert_eq!</span>(<span class="number">0</span>, libc::pipe(fds.as_mut_ptr())) }; |
| <span class="kw">let </span>read = OwnedFd(fds[<span class="number">0</span>]); |
| <span class="kw">let </span>write = OwnedFd(fds[<span class="number">1</span>]); |
| register(libc::SIGUSR1, write)<span class="question-mark">?</span>; |
| read.set_flags()<span class="question-mark">?</span>; |
| wakeup(); |
| <span class="kw">let </span><span class="kw-2">mut </span>buff = [<span class="number">0</span>; <span class="number">1</span>]; |
| <span class="kw">unsafe </span>{ |
| <span class="macro">assert_eq!</span>( |
| <span class="number">1</span>, |
| libc::read(read.as_raw_fd(), buff.as_mut_ptr() <span class="kw">as </span><span class="kw-2">*mut </span><span class="kw">_</span>, <span class="number">1</span>) |
| ) |
| } |
| <span class="macro">assert_eq!</span>(<span class="string">b"X"</span>, <span class="kw-2">&</span>buff); |
| <span class="prelude-val">Ok</span>(()) |
| } |
| } |
| </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> |
