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use crate::cell::UnsafeCell;
use crate::sys::mutex::{self, Mutex};
use crate::time::Duration;
pub struct Condvar {
inner: UnsafeCell<libc::pthread_cond_t>,
}
unsafe impl Send for Condvar {}
unsafe impl Sync for Condvar {}
const TIMESPEC_MAX: libc::timespec =
libc::timespec { tv_sec: <libc::time_t>::MAX, tv_nsec: 1_000_000_000 - 1 };
fn saturating_cast_to_time_t(value: u64) -> libc::time_t {
if value > <libc::time_t>::MAX as u64 { <libc::time_t>::MAX } else { value as libc::time_t }
}
impl Condvar {
pub const fn new() -> Condvar {
// Might be moved and address is changing it is better to avoid
// initialization of potentially opaque OS data before it landed
Condvar { inner: UnsafeCell::new(libc::PTHREAD_COND_INITIALIZER) }
}
pub unsafe fn init(&mut self) {
use crate::mem::MaybeUninit;
let mut attr = MaybeUninit::<libc::pthread_condattr_t>::uninit();
let r = libc::pthread_condattr_init(attr.as_mut_ptr());
assert_eq!(r, 0);
let r = libc::pthread_condattr_setclock(attr.as_mut_ptr(), libc::CLOCK_MONOTONIC);
assert_eq!(r, 0);
let r = libc::pthread_cond_init(self.inner.get(), attr.as_ptr());
assert_eq!(r, 0);
let r = libc::pthread_condattr_destroy(attr.as_mut_ptr());
assert_eq!(r, 0);
}
#[inline]
pub unsafe fn notify_one(&self) {
let r = libc::pthread_cond_signal(self.inner.get());
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn notify_all(&self) {
let r = libc::pthread_cond_broadcast(self.inner.get());
debug_assert_eq!(r, 0);
}
#[inline]
pub unsafe fn wait(&self, mutex: &Mutex) {
let r = libc::pthread_cond_wait(self.inner.get(), mutex::raw(mutex));
debug_assert_eq!(r, 0);
}
// This implementation is used on systems that support pthread_condattr_setclock
// where we configure condition variable to use monotonic clock (instead of
// default system clock). This approach avoids all problems that result
// from changes made to the system time.
pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
use crate::mem;
let mut now: libc::timespec = mem::zeroed();
let r = libc::clock_gettime(libc::CLOCK_MONOTONIC, &mut now);
assert_eq!(r, 0);
// Nanosecond calculations can't overflow because both values are below 1e9.
let nsec = dur.subsec_nanos() + now.tv_nsec as u32;
let sec = saturating_cast_to_time_t(dur.as_secs())
.checked_add((nsec / 1_000_000_000) as libc::time_t)
.and_then(|s| s.checked_add(now.tv_sec));
let nsec = nsec % 1_000_000_000;
let timeout =
sec.map(|s| libc::timespec { tv_sec: s, tv_nsec: nsec as _ }).unwrap_or(TIMESPEC_MAX);
let r = libc::pthread_cond_timedwait(self.inner.get(), mutex::raw(mutex), &timeout);
assert!(r == libc::ETIMEDOUT || r == 0);
r == 0
}
#[inline]
pub unsafe fn destroy(&self) {
let r = libc::pthread_cond_destroy(self.inner.get());
debug_assert_eq!(r, 0);
}
}
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