src/libstd/sys/unix/condvar.rs

   1 // Copyright 2014 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.
   4 //
   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.
  10
  11 use prelude::v1::*;
  12
  13 use cell::UnsafeCell;
  14 use libc;
  15 use ptr;
  16 use sys::mutex::{self, Mutex};
  17 use sys::time;
  18 use sys::sync as ffi;
  19 use time::Duration;
  20
  21 pub struct Condvar { inner: UnsafeCell<ffi::pthread_cond_t> }
  22
  23 unsafe impl Send for Condvar {}
  24 unsafe impl Sync for Condvar {}
  25
  26 impl Condvar {
  27     pub const fn new() -> Condvar {
  28         // Might be moved and address is changing it is better to avoid
  29         // initialization of potentially opaque OS data before it landed
  30         Condvar { inner: UnsafeCell::new(ffi::PTHREAD_COND_INITIALIZER) }
  31     }
  32
  33     #[inline]
  34     pub unsafe fn notify_one(&self) {
  35         let r = ffi::pthread_cond_signal(self.inner.get());
  36         debug_assert_eq!(r, 0);
  37     }
  38
  39     #[inline]
  40     pub unsafe fn notify_all(&self) {
  41         let r = ffi::pthread_cond_broadcast(self.inner.get());
  42         debug_assert_eq!(r, 0);
  43     }
  44
  45     #[inline]
  46     pub unsafe fn wait(&self, mutex: &Mutex) {
  47         let r = ffi::pthread_cond_wait(self.inner.get(), mutex::raw(mutex));
  48         debug_assert_eq!(r, 0);
  49     }
  50
  51     // This implementation is modeled after libcxx's condition_variable
  52     // https://github.com/llvm-mirror/libcxx/blob/release_35/src/condition_variable.cpp#L46
  53     // https://github.com/llvm-mirror/libcxx/blob/release_35/include/__mutex_base#L367
  54     pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
  55         // First, figure out what time it currently is, in both system and
  56         // stable time.  pthread_cond_timedwait uses system time, but we want to
  57         // report timeout based on stable time.
  58         let mut sys_now = libc::timeval { tv_sec: 0, tv_usec: 0 };
  59         let stable_now = time::SteadyTime::now();
  60         let r = ffi::gettimeofday(&mut sys_now, ptr::null_mut());
  61         debug_assert_eq!(r, 0);
  62
  63         let nsec = dur.subsec_nanos() as libc::c_long +
  64                    (sys_now.tv_usec * 1000) as libc::c_long;
  65         let extra = (nsec / 1_000_000_000) as libc::time_t;
  66         let nsec = nsec % 1_000_000_000;
  67         let seconds = dur.as_secs() as libc::time_t;
  68
  69         let timeout = sys_now.tv_sec.checked_add(extra).and_then(|s| {
  70             s.checked_add(seconds)
  71         }).map(|s| {
  72             libc::timespec { tv_sec: s, tv_nsec: nsec }
  73         }).unwrap_or_else(|| {
  74             libc::timespec {
  75                 tv_sec: <libc::time_t>::max_value(),
  76                 tv_nsec: 1_000_000_000 - 1,
  77             }
  78         });
  79
  80         // And wait!
  81         let r = ffi::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex),
  82                                             &timeout);
  83         debug_assert!(r == libc::ETIMEDOUT || r == 0);
  84
  85         // ETIMEDOUT is not a totally reliable method of determining timeout due
  86         // to clock shifts, so do the check ourselves
  87         &time::SteadyTime::now() - &stable_now < dur
  88     }
  89
  90     #[inline]
  91     #[cfg(not(target_os = "dragonfly"))]
  92     pub unsafe fn destroy(&self) {
  93         let r = ffi::pthread_cond_destroy(self.inner.get());
  94         debug_assert_eq!(r, 0);
  95     }
  96
  97     #[inline]
  98     #[cfg(target_os = "dragonfly")]
  99     pub unsafe fn destroy(&self) {
 100         let r = ffi::pthread_cond_destroy(self.inner.get());
 101         // On DragonFly pthread_cond_destroy() returns EINVAL if called on
 102         // a condvar that was just initialized with
 103         // ffi::PTHREAD_COND_INITIALIZER. Once it is used or
 104         // pthread_cond_init() is called, this behaviour no longer occurs.
 105         debug_assert!(r == 0 || r == libc::EINVAL);
 106     }
 107 }