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epoll.rs
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epoll.rs
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use crate::{Interest, Token};
use libc::{EPOLLET, EPOLLIN, EPOLLOUT, EPOLLPRI, EPOLLRDHUP};
use std::os::unix::io::{AsRawFd, RawFd};
#[cfg(debug_assertions)]
use std::sync::atomic::{AtomicUsize, Ordering};
use std::time::Duration;
use std::{cmp, i32, io, ptr};
/// Unique id for use as `SelectorId`.
#[cfg(debug_assertions)]
static NEXT_ID: AtomicUsize = AtomicUsize::new(1);
#[derive(Debug)]
pub struct Selector {
#[cfg(debug_assertions)]
id: usize,
ep: RawFd,
}
impl Selector {
pub fn new() -> io::Result<Selector> {
#[cfg(not(target_os = "android"))]
let res = syscall!(epoll_create1(libc::EPOLL_CLOEXEC));
// On Android < API level 16 `epoll_create1` is not defined, so use a
// raw system call.
// According to libuv, `EPOLL_CLOEXEC` is not defined on Android API <
// 21. But `EPOLL_CLOEXEC` is an alias for `O_CLOEXEC` on that platform,
// so we use it instead.
#[cfg(target_os = "android")]
let res = syscall!(syscall(libc::SYS_epoll_create1, libc::O_CLOEXEC));
let ep = match res {
Ok(ep) => ep as RawFd,
Err(err) => {
// When `epoll_create1` is not available fall back to use
// `epoll_create` followed by `fcntl`.
if let Some(libc::ENOSYS) = err.raw_os_error() {
match syscall!(epoll_create(1024)) {
Ok(ep) => match syscall!(fcntl(ep, libc::F_SETFD, libc::FD_CLOEXEC)) {
Ok(ep) => ep as RawFd,
Err(err) => {
// `fcntl` failed, cleanup `ep`.
let _ = unsafe { libc::close(ep) };
return Err(err);
}
},
Err(err) => return Err(err),
}
} else {
return Err(err);
}
}
};
Ok(Selector {
#[cfg(debug_assertions)]
id: NEXT_ID.fetch_add(1, Ordering::Relaxed),
ep,
})
}
pub fn try_clone(&self) -> io::Result<Selector> {
syscall!(fcntl(self.ep, libc::F_DUPFD_CLOEXEC, super::LOWEST_FD)).map(|ep| Selector {
// It's the same selector, so we use the same id.
#[cfg(debug_assertions)]
id: self.id,
ep,
})
}
pub fn select(&self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> {
// A bug in kernels < 2.6.37 makes timeouts larger than LONG_MAX / CONFIG_HZ
// (approx. 30 minutes with CONFIG_HZ=1200) effectively infinite on 32 bits
// architectures. The magic number is the same constant used by libuv.
#[cfg(target_pointer_width = "32")]
const MAX_SAFE_TIMEOUT: u128 = 1789569;
#[cfg(not(target_pointer_width = "32"))]
const MAX_SAFE_TIMEOUT: u128 = libc::c_int::max_value() as u128;
let timeout = timeout
.map(|to| {
// `Duration::as_millis` truncates, so round up. This avoids
// turning sub-millisecond timeouts into a zero timeout, unless
// the caller explicitly requests that by specifying a zero
// timeout.
let to_ms = to
.checked_add(Duration::from_nanos(999_999))
.unwrap_or(to)
.as_millis();
cmp::min(MAX_SAFE_TIMEOUT, to_ms) as libc::c_int
})
.unwrap_or(-1);
events.clear();
syscall!(epoll_wait(
self.ep,
events.as_mut_ptr(),
events.capacity() as i32,
timeout,
))
.map(|n_events| {
// This is safe because `epoll_wait` ensures that `n_events` are
// assigned.
unsafe { events.set_len(n_events as usize) };
})
}
pub fn register(&self, fd: RawFd, token: Token, interests: Interest) -> io::Result<()> {
let mut event = libc::epoll_event {
events: interests_to_epoll(interests),
u64: usize::from(token) as u64,
#[cfg(target_os = "redox")]
_pad: 0,
};
syscall!(epoll_ctl(self.ep, libc::EPOLL_CTL_ADD, fd, &mut event)).map(|_| ())
}
pub fn reregister(&self, fd: RawFd, token: Token, interests: Interest) -> io::Result<()> {
let mut event = libc::epoll_event {
events: interests_to_epoll(interests),
u64: usize::from(token) as u64,
#[cfg(target_os = "redox")]
_pad: 0,
};
syscall!(epoll_ctl(self.ep, libc::EPOLL_CTL_MOD, fd, &mut event)).map(|_| ())
}
pub fn deregister(&self, fd: RawFd) -> io::Result<()> {
syscall!(epoll_ctl(self.ep, libc::EPOLL_CTL_DEL, fd, ptr::null_mut())).map(|_| ())
}
}
cfg_io_source! {
impl Selector {
#[cfg(debug_assertions)]
pub fn id(&self) -> usize {
self.id
}
}
}
impl AsRawFd for Selector {
fn as_raw_fd(&self) -> RawFd {
self.ep
}
}
impl Drop for Selector {
fn drop(&mut self) {
if let Err(err) = syscall!(close(self.ep)) {
error!("error closing epoll: {}", err);
}
}
}
fn interests_to_epoll(interests: Interest) -> u32 {
let mut kind = EPOLLET;
if interests.is_readable() {
kind = kind | EPOLLIN | EPOLLRDHUP;
}
if interests.is_writable() {
kind |= EPOLLOUT;
}
if interests.is_priority() {
kind |= EPOLLPRI;
}
kind as u32
}
pub type Event = libc::epoll_event;
pub type Events = Vec<Event>;
pub mod event {
use std::fmt;
use crate::sys::Event;
use crate::Token;
pub fn token(event: &Event) -> Token {
Token(event.u64 as usize)
}
pub fn is_readable(event: &Event) -> bool {
(event.events as libc::c_int & libc::EPOLLIN) != 0
|| (event.events as libc::c_int & libc::EPOLLPRI) != 0
}
pub fn is_writable(event: &Event) -> bool {
(event.events as libc::c_int & libc::EPOLLOUT) != 0
}
pub fn is_error(event: &Event) -> bool {
(event.events as libc::c_int & libc::EPOLLERR) != 0
}
pub fn is_read_closed(event: &Event) -> bool {
// Both halves of the socket have closed
event.events as libc::c_int & libc::EPOLLHUP != 0
// Socket has received FIN or called shutdown(SHUT_RD)
|| (event.events as libc::c_int & libc::EPOLLIN != 0
&& event.events as libc::c_int & libc::EPOLLRDHUP != 0)
}
pub fn is_write_closed(event: &Event) -> bool {
// Both halves of the socket have closed
event.events as libc::c_int & libc::EPOLLHUP != 0
// Unix pipe write end has closed
|| (event.events as libc::c_int & libc::EPOLLOUT != 0
&& event.events as libc::c_int & libc::EPOLLERR != 0)
// The other side (read end) of a Unix pipe has closed.
|| event.events as libc::c_int == libc::EPOLLERR
}
pub fn is_priority(event: &Event) -> bool {
(event.events as libc::c_int & libc::EPOLLPRI) != 0
}
pub fn is_aio(_: &Event) -> bool {
// Not supported in the kernel, only in libc.
false
}
pub fn is_lio(_: &Event) -> bool {
// Not supported.
false
}
pub fn debug_details(f: &mut fmt::Formatter<'_>, event: &Event) -> fmt::Result {
#[allow(clippy::trivially_copy_pass_by_ref)]
fn check_events(got: &u32, want: &libc::c_int) -> bool {
(*got as libc::c_int & want) != 0
}
debug_detail!(
EventsDetails(u32),
check_events,
libc::EPOLLIN,
libc::EPOLLPRI,
libc::EPOLLOUT,
libc::EPOLLRDNORM,
libc::EPOLLRDBAND,
libc::EPOLLWRNORM,
libc::EPOLLWRBAND,
libc::EPOLLMSG,
libc::EPOLLERR,
libc::EPOLLHUP,
libc::EPOLLET,
libc::EPOLLRDHUP,
libc::EPOLLONESHOT,
#[cfg(target_os = "linux")]
libc::EPOLLEXCLUSIVE,
#[cfg(any(target_os = "android", target_os = "linux"))]
libc::EPOLLWAKEUP,
libc::EPOLL_CLOEXEC,
);
// Can't reference fields in packed structures.
let e_u64 = event.u64;
f.debug_struct("epoll_event")
.field("events", &EventsDetails(event.events))
.field("u64", &e_u64)
.finish()
}
}
#[cfg(target_os = "android")]
#[test]
fn assert_close_on_exec_flag() {
// This assertion need to be true for Selector::new.
assert_eq!(libc::O_CLOEXEC, libc::EPOLL_CLOEXEC);
}