1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Timers for non-Linux/non-Windows OSes
13 //! This module implements timers with a worker thread, select(), and a lot of
14 //! witchcraft that turns out to be horribly inaccurate timers. The unfortunate
15 //! part is that I'm at a loss of what else to do one these OSes. This is also
16 //! why Linux has a specialized timerfd implementation and windows has its own
17 //! implementation (they're more accurate than this one).
19 //! The basic idea is that there is a worker thread that's communicated to via a
20 //! channel and a pipe, the pipe is used by the worker thread in a select()
21 //! syscall with a timeout. The timeout is the "next timer timeout" while the
22 //! channel is used to send data over to the worker thread.
24 //! Whenever the call to select() times out, then a channel receives a message.
25 //! Whenever the call returns that the file descriptor has information, then the
26 //! channel from timers is drained, enqueuing all incoming requests.
28 //! The actual implementation of the helper thread is a sorted array of
29 //! timers in terms of target firing date. The target is the absolute time at
30 //! which the timer should fire. Timers are then re-enqueued after a firing if
31 //! the repeat boolean is set.
33 //! Naturally, all this logic of adding times and keeping track of
34 //! relative/absolute time is a little lossy and not quite exact. I've done the
35 //! best I could to reduce the amount of calls to 'now()', but there's likely
36 //! still inaccuracies trickling in here and there.
38 //! One of the tricky parts of this implementation is that whenever a timer is
39 //! acted upon, it must cancel whatever the previous action was (if one is
40 //! active) in order to act like the other implementations of this timer. In
41 //! order to do this, the timer's inner pointer is transferred to the worker
42 //! thread. Whenever the timer is modified, it first takes ownership back from
43 //! the worker thread in order to modify the same data structure. This has the
44 //! side effect of "cancelling" the previous requests while allowing a
45 //! re-enqueuing later on.
47 //! Note that all time units in this file are in *milliseconds*.
59 use sync::atomic::{self, Ordering};
60 use sync::mpsc::{channel, Sender, Receiver, TryRecvError};
62 use sys::fs::FileDesc;
63 use sys_common::helper_thread::Helper;
65 helper_init! { static HELPER: Helper<Req> }
73 inner: Option<Box<Inner>>,
77 cb: Option<Box<Callback + Send>>,
85 // Add a new timer to the helper thread.
88 // Remove a timer based on its id and then send it back on the channel
90 RemoveTimer(uint, Sender<Box<Inner>>),
93 // returns the current time (in milliseconds)
96 let mut now: libc::timeval = mem::zeroed();
97 assert_eq!(c::gettimeofday(&mut now, ptr::null_mut()), 0);
98 return (now.tv_sec as u64) * 1000 + (now.tv_usec as u64) / 1000;
102 fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
103 let mut set: c::fd_set = unsafe { mem::zeroed() };
105 let fd = FileDesc::new(input, true);
106 let mut timeout: libc::timeval = unsafe { mem::zeroed() };
108 // active timers are those which are able to be selected upon (and it's a
109 // sorted list, and dead timers are those which have expired, but ownership
110 // hasn't yet been transferred back to the timer itself.
111 let mut active: Vec<Box<Inner>> = vec![];
112 let mut dead = vec![];
114 // inserts a timer into an array of timers (sorted by firing time)
115 fn insert(t: Box<Inner>, active: &mut Vec<Box<Inner>>) {
116 match active.iter().position(|tm| tm.target > t.target) {
117 Some(pos) => { active.insert(pos, t); }
118 None => { active.push(t); }
122 // signals the first requests in the queue, possible re-enqueueing it.
123 fn signal(active: &mut Vec<Box<Inner>>,
124 dead: &mut Vec<(uint, Box<Inner>)>) {
125 if active.is_empty() { return }
127 let mut timer = active.remove(0);
128 let mut cb = timer.cb.take().unwrap();
132 timer.target += timer.interval;
133 insert(timer, active);
135 dead.push((timer.id, timer));
140 let timeout = if active.len() == 0 {
141 // Empty array? no timeout (wait forever for the next request)
145 // If this request has already expired, then signal it and go
146 // through another iteration
147 if active[0].target <= now {
148 signal(&mut active, &mut dead);
152 // The actual timeout listed in the requests array is an
153 // absolute date, so here we translate the absolute time to a
155 let tm = active[0].target - now;
156 timeout.tv_sec = (tm / 1000) as libc::time_t;
157 timeout.tv_usec = ((tm % 1000) * 1000) as libc::suseconds_t;
158 &mut timeout as *mut libc::timeval
161 c::fd_set(&mut set, input);
163 c::select(input + 1, &mut set, ptr::null_mut(),
164 ptr::null_mut(), timeout)
167 0 => signal(&mut active, &mut dead),
169 // file descriptor write woke us up, we've got some new requests
172 match messages.try_recv() {
173 // Once we've been disconnected it means the main thread
174 // is exiting (at_exit has run). We could still have
175 // active timers for other threads, so we're just going
176 // to drop them all on the floor. This is all we can
177 // really do, however, to prevent resource leakage. The
178 // remaining timers will likely start panicking quickly
179 // as they attempt to re-use this thread but are
180 // disallowed to do so.
181 Err(TryRecvError::Disconnected) => {
185 Ok(NewTimer(timer)) => insert(timer, &mut active),
187 Ok(RemoveTimer(id, ack)) => {
188 match dead.iter().position(|&(i, _)| id == i) {
190 let (_, i) = dead.remove(i);
191 ack.send(i).unwrap();
196 let i = active.iter().position(|i| i.id == id);
197 let i = i.expect("no timer found");
198 let t = active.remove(i);
199 ack.send(t).unwrap();
205 // drain the file descriptor
207 assert_eq!(fd.read(&mut buf).unwrap(), 1);
210 -1 if os::errno() == libc::EINTR as i32 => {}
211 n => panic!("helper thread failed in select() with error: {} ({})",
212 n, os::last_os_error())
218 pub fn new() -> IoResult<Timer> {
219 // See notes above regarding using int return value
221 HELPER.boot(|| {}, helper);
223 static ID: atomic::AtomicUsize = atomic::ATOMIC_USIZE_INIT;
224 let id = ID.fetch_add(1, Ordering::Relaxed);
227 inner: Some(box Inner {
237 pub fn sleep(&mut self, ms: u64) {
238 let mut inner = self.inner();
239 inner.cb = None; // cancel any previous request
240 self.inner = Some(inner);
242 let mut to_sleep = libc::timespec {
243 tv_sec: (ms / 1000) as libc::time_t,
244 tv_nsec: ((ms % 1000) * 1000000) as libc::c_long,
246 while unsafe { libc::nanosleep(&to_sleep, &mut to_sleep) } != 0 {
247 if os::errno() as int != libc::EINTR as int {
248 panic!("failed to sleep, but not because of EINTR?");
253 pub fn oneshot(&mut self, msecs: u64, cb: Box<Callback + Send>) {
255 let mut inner = self.inner();
257 inner.repeat = false;
259 inner.interval = msecs;
260 inner.target = now + msecs;
262 HELPER.send(NewTimer(inner));
265 pub fn period(&mut self, msecs: u64, cb: Box<Callback + Send>) {
267 let mut inner = self.inner();
271 inner.interval = msecs;
272 inner.target = now + msecs;
274 HELPER.send(NewTimer(inner));
277 fn inner(&mut self) -> Box<Inner> {
278 match self.inner.take() {
281 let (tx, rx) = channel();
282 HELPER.send(RemoveTimer(self.id, tx));
289 impl Drop for Timer {
291 self.inner = Some(self.inner());