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// Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
use std::i64;
use std::time::Duration;
use std::ptr::null;
use std::os::unix::io::{AsRawFd, RawFd};
use std::os::unix::net::{UnixDatagram, UnixStream};
use libc::{c_int, c_long, timespec, time_t, nfds_t, sigset_t, pollfd, syscall, SYS_ppoll, POLLIN};
use {Result, errno_result};
// The libc wrapper suppresses the kernel's changes to timeout, so we use the syscall directly.
unsafe fn ppoll(fds: *mut pollfd,
nfds: nfds_t,
timeout: *mut timespec,
sigmask: *const sigset_t,
sigsetsize: usize)
-> c_int {
syscall(SYS_ppoll, fds, nfds, timeout, sigmask, sigsetsize) as c_int
}
/// Trait for file descriptors that can be polled for input.
///
/// This is marked unsafe because the implementation must promise that the returned RawFd is valid
/// for polling purposes and that the lifetime of the returned fd is at least that of the trait
/// object.
pub unsafe trait Pollable {
/// Gets the file descriptor that can be polled for input.
fn pollable_fd(&self) -> RawFd;
}
unsafe impl Pollable for UnixStream {
fn pollable_fd(&self) -> RawFd {
self.as_raw_fd()
}
}
unsafe impl Pollable for UnixDatagram {
fn pollable_fd(&self) -> RawFd {
self.as_raw_fd()
}
}
/// Used to poll multiple `Pollable` objects at once.
///
/// # Example
///
/// ```
/// # use sys_util::{Result, EventFd, Poller, Pollable};
/// # fn test() -> Result<()> {
/// let evt1 = EventFd::new()?;
/// let evt2 = EventFd::new()?;
/// evt2.write(1)?;
///
/// let pollables: Vec<(u32, &Pollable)> = vec![(1, &evt1), (2, &evt2)];
///
/// let mut poller = Poller::new(2);
/// assert_eq!(poller.poll(&pollables[..]), Ok([2].as_ref()));
/// # Ok(())
/// # }
/// ```
pub struct Poller {
pollfds: Vec<pollfd>,
tokens: Vec<u32>,
}
impl Poller {
/// Constructs a new poller object with the given `capacity` of Pollable objects pre-allocated.
pub fn new(capacity: usize) -> Poller {
Poller {
pollfds: Vec::with_capacity(capacity),
tokens: Vec::with_capacity(capacity),
}
}
/// Waits for any of the given slice of `token`-`Pollable` tuples to be readable without
/// blocking and returns the `token` of each that is readable.
///
/// This is guaranteed to not allocate if `pollables.len()` is less than the `capacity` given in
/// `Poller::new`.
pub fn poll(&mut self, pollables: &[(u32, &Pollable)]) -> Result<&[u32]> {
self.poll_timeout(pollables, &mut Duration::new(i64::MAX as u64, 0))
}
/// Waits for up to the given timeout for any of the given slice of `token`-`Pollable` tuples to
/// be readable without blocking and returns the `token` of each that is readable.
///
/// If a timeout duration is given, the duration will be modified to the unused portion of the
/// timeout, even if an error is returned.
///
/// This is guaranteed to not allocate if `pollables.len()` is less than the `capacity` given in
/// `Poller::new`.
pub fn poll_timeout(&mut self,
pollables: &[(u32, &Pollable)],
timeout: &mut Duration)
-> Result<&[u32]> {
self.pollfds.clear();
for pollable in pollables.iter() {
self.pollfds
.push(pollfd {
fd: pollable.1.pollable_fd(),
events: POLLIN,
revents: 0,
});
}
let mut timeout_spec = timespec {
tv_sec: timeout.as_secs() as time_t,
tv_nsec: timeout.subsec_nanos() as c_long,
};
// Safe because poll is given the correct length of properly initialized pollfds, and we
// check the return result.
let ret = unsafe {
handle_eintr_errno!(ppoll(self.pollfds.as_mut_ptr(),
self.pollfds.len() as nfds_t,
&mut timeout_spec,
null(),
0))
};
*timeout = Duration::new(timeout_spec.tv_sec as u64, timeout_spec.tv_nsec as u32);
if ret < 0 {
return errno_result();
}
self.tokens.clear();
for (pollfd, pollable) in self.pollfds.iter().zip(pollables.iter()) {
if (pollfd.revents & POLLIN) != 0 {
self.tokens.push(pollable.0);
}
}
Ok(&self.tokens)
}
}
#[cfg(test)]
mod tests {
use super::*;
use EventFd;
#[test]
fn poller() {
let evt1 = EventFd::new().unwrap();
let evt2 = EventFd::new().unwrap();
evt2.write(1).unwrap();
let pollables: Vec<(u32, &Pollable)> = vec![(1, &evt1), (2, &evt2)];
let mut poller = Poller::new(2);
assert_eq!(poller.poll(&pollables[..]), Ok([2].as_ref()));
}
#[test]
fn poller_multi() {
let evt1 = EventFd::new().unwrap();
let evt2 = EventFd::new().unwrap();
evt1.write(1).unwrap();
evt2.write(1).unwrap();
let pollables: Vec<(u32, &Pollable)> = vec![(1, &evt1), (2, &evt2)];
let mut poller = Poller::new(2);
assert_eq!(poller.poll(&pollables[..]), Ok([1, 2].as_ref()));
}
#[test]
fn timeout() {
let evt1 = EventFd::new().unwrap();
let initial_dur = Duration::from_millis(10);
let mut timeout_dur = initial_dur;
let mut poller = Poller::new(0);
assert_eq!(poller.poll_timeout(&[(1, &evt1)], &mut timeout_dur),
Ok([].as_ref()));
assert_eq!(timeout_dur, Duration::from_secs(0));
evt1.write(1).unwrap();
timeout_dur = initial_dur;
assert_eq!(poller.poll_timeout(&[(1, &evt1)], &mut timeout_dur),
Ok([1].as_ref()));
assert!(timeout_dur < initial_dur);
}
}
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