async_signal/
pipe.rs

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1//! A signal notifier that uses an asynchronous pipe.
2
3use crate::Signal;
4
5use async_io::Async;
6use futures_core::ready;
7use futures_io::AsyncRead;
8
9use std::io::{self, prelude::*};
10use std::mem;
11use std::os::unix::io::{AsFd, AsRawFd, BorrowedFd, RawFd};
12use std::os::unix::net::UnixStream;
13use std::pin::Pin;
14use std::task::{Context, Poll};
15
16const BUFFER_LEN: usize = mem::size_of::<std::os::raw::c_int>();
17
18/// The notifier that uses an asynchronous pipe.
19#[derive(Debug)]
20pub(super) struct Notifier {
21    /// The read end of the signal pipe.
22    read: Async<UnixStream>,
23
24    /// The write end of the signal pipe.
25    write: UnixStream,
26}
27
28impl Notifier {
29    /// Create a new signal notifier.
30    pub(super) fn new() -> io::Result<Self> {
31        let (read, write) = UnixStream::pair()?;
32        let read = Async::new(read)?;
33        write.set_nonblocking(true)?;
34
35        Ok(Self { read, write })
36    }
37
38    /// Add a signal to the notifier.
39    ///
40    /// Returns a closure to be passed to signal-hook.
41    pub(super) fn add_signal(
42        &mut self,
43        signal: Signal,
44    ) -> io::Result<impl Fn() + Send + Sync + 'static> {
45        let number = signal.number();
46        let write = self.write.try_clone()?;
47
48        Ok(move || {
49            // SAFETY: to_ne_bytes() and write() are both signal safe.
50            let bytes = number.to_ne_bytes();
51            let _ = (&write).write(&bytes);
52        })
53    }
54
55    /// Remove a signal from the notifier.
56    pub(super) fn remove_signal(&mut self, _signal: Signal) -> io::Result<()> {
57        Ok(())
58    }
59
60    /// Get the next signal.
61    pub(super) fn poll_next(&self, cx: &mut Context<'_>) -> Poll<io::Result<Signal>> {
62        let mut buffer = [0; BUFFER_LEN];
63        let mut buffer_len = 0;
64
65        // Read into the buffer.
66        loop {
67            if buffer_len >= BUFFER_LEN {
68                break;
69            }
70
71            // Try to fill up the entire buffer.
72            let buf_range = buffer_len..BUFFER_LEN;
73            let res = ready!(Pin::new(&mut &self.read).poll_read(cx, &mut buffer[buf_range]));
74
75            match res {
76                Ok(0) => return Poll::Ready(Err(io::Error::from(io::ErrorKind::UnexpectedEof))),
77                Ok(n) => buffer_len += n,
78                Err(e) => return Poll::Ready(Err(e)),
79            }
80        }
81
82        // Convert the buffer into a signal number.
83        let number = std::os::raw::c_int::from_ne_bytes(buffer);
84
85        // Convert the signal number into a signal.
86        let signal = match Signal::from_number(number) {
87            Some(signal) => signal,
88            None => return Poll::Ready(Err(io::Error::from(io::ErrorKind::InvalidData))),
89        };
90
91        // Return the signal.
92        Poll::Ready(Ok(signal))
93    }
94}
95
96impl AsRawFd for Notifier {
97    fn as_raw_fd(&self) -> RawFd {
98        self.read.as_raw_fd()
99    }
100}
101
102impl AsFd for Notifier {
103    fn as_fd(&self) -> BorrowedFd<'_> {
104        self.read.as_fd()
105    }
106}
async_signal/pipe.rs

async_signal/
pipe.rs
