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*.
57 use sync::atomic::{mod, Ordering};
58 use sync::mpsc::{channel, Sender, Receiver, TryRecvError};
60 use sys::fs::FileDesc;
61 use sys_common::helper_thread::Helper;
63 helper_init! { static HELPER: Helper<Req> }
71 inner: Option<Box<Inner>>,
75 cb: Option<Box<Callback + Send>>,
83 // Add a new timer to the helper thread.
86 // Remove a timer based on its id and then send it back on the channel
88 RemoveTimer(uint, Sender<Box<Inner>>),
91 // returns the current time (in milliseconds)
94 let mut now: libc::timeval = mem::zeroed();
95 assert_eq!(c::gettimeofday(&mut now, ptr::null_mut()), 0);
96 return (now.tv_sec as u64) * 1000 + (now.tv_usec as u64) / 1000;
100 fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
101 let mut set: c::fd_set = unsafe { mem::zeroed() };
103 let mut fd = FileDesc::new(input, true);
104 let mut timeout: libc::timeval = unsafe { mem::zeroed() };
106 // active timers are those which are able to be selected upon (and it's a
107 // sorted list, and dead timers are those which have expired, but ownership
108 // hasn't yet been transferred back to the timer itself.
109 let mut active: Vec<Box<Inner>> = vec![];
110 let mut dead = vec![];
112 // inserts a timer into an array of timers (sorted by firing time)
113 fn insert(t: Box<Inner>, active: &mut Vec<Box<Inner>>) {
114 match active.iter().position(|tm| tm.target > t.target) {
115 Some(pos) => { active.insert(pos, t); }
116 None => { active.push(t); }
120 // signals the first requests in the queue, possible re-enqueueing it.
121 fn signal(active: &mut Vec<Box<Inner>>,
122 dead: &mut Vec<(uint, Box<Inner>)>) {
123 if active.is_empty() { return }
125 let mut timer = active.remove(0);
126 let mut cb = timer.cb.take().unwrap();
130 timer.target += timer.interval;
131 insert(timer, active);
133 dead.push((timer.id, timer));
138 let timeout = if active.len() == 0 {
139 // Empty array? no timeout (wait forever for the next request)
143 // If this request has already expired, then signal it and go
144 // through another iteration
145 if active[0].target <= now {
146 signal(&mut active, &mut dead);
150 // The actual timeout listed in the requests array is an
151 // absolute date, so here we translate the absolute time to a
153 let tm = active[0].target - now;
154 timeout.tv_sec = (tm / 1000) as libc::time_t;
155 timeout.tv_usec = ((tm % 1000) * 1000) as libc::suseconds_t;
156 &mut timeout as *mut libc::timeval
159 c::fd_set(&mut set, input);
161 c::select(input + 1, &mut set, ptr::null_mut(),
162 ptr::null_mut(), timeout)
165 0 => signal(&mut active, &mut dead),
167 // file descriptor write woke us up, we've got some new requests
170 match messages.try_recv() {
171 Err(TryRecvError::Disconnected) => {
172 assert!(active.len() == 0);
176 Ok(NewTimer(timer)) => insert(timer, &mut active),
178 Ok(RemoveTimer(id, ack)) => {
179 match dead.iter().position(|&(i, _)| id == i) {
181 let (_, i) = dead.remove(i);
182 ack.send(i).unwrap();
187 let i = active.iter().position(|i| i.id == id);
188 let i = i.expect("no timer found");
189 let t = active.remove(i);
190 ack.send(t).unwrap();
196 // drain the file descriptor
198 assert_eq!(fd.read(&mut buf).ok().unwrap(), 1);
201 -1 if os::errno() == libc::EINTR as uint => {}
202 n => panic!("helper thread failed in select() with error: {} ({})",
203 n, os::last_os_error())
209 pub fn new() -> IoResult<Timer> {
210 // See notes above regarding using int return value
212 HELPER.boot(|| {}, helper);
214 static ID: atomic::AtomicUint = atomic::ATOMIC_UINT_INIT;
215 let id = ID.fetch_add(1, Ordering::Relaxed);
218 inner: Some(box Inner {
228 pub fn sleep(&mut self, ms: u64) {
229 let mut inner = self.inner();
230 inner.cb = None; // cancel any previous request
231 self.inner = Some(inner);
233 let mut to_sleep = libc::timespec {
234 tv_sec: (ms / 1000) as libc::time_t,
235 tv_nsec: ((ms % 1000) * 1000000) as libc::c_long,
237 while unsafe { libc::nanosleep(&to_sleep, &mut to_sleep) } != 0 {
238 if os::errno() as int != libc::EINTR as int {
239 panic!("failed to sleep, but not because of EINTR?");
244 pub fn oneshot(&mut self, msecs: u64, cb: Box<Callback + Send>) {
246 let mut inner = self.inner();
248 inner.repeat = false;
250 inner.interval = msecs;
251 inner.target = now + msecs;
253 HELPER.send(NewTimer(inner));
256 pub fn period(&mut self, msecs: u64, cb: Box<Callback + Send>) {
258 let mut inner = self.inner();
262 inner.interval = msecs;
263 inner.target = now + msecs;
265 HELPER.send(NewTimer(inner));
268 fn inner(&mut self) -> Box<Inner> {
269 match self.inner.take() {
272 let (tx, rx) = channel();
273 HELPER.send(RemoveTimer(self.id, tx));
280 impl Drop for Timer {
282 self.inner = Some(self.inner());