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}
107