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use crate::cell::UnsafeCell;
use crate::intrinsics::{atomic_cxchg, atomic_load, atomic_xadd, atomic_xchg};
use crate::ptr;
use crate::time::Duration;
use crate::sys::mutex::{mutex_unlock, Mutex};
use crate::sys::syscall::{futex, TimeSpec, FUTEX_WAIT, FUTEX_WAKE, FUTEX_REQUEUE};
pub struct Condvar {
lock: UnsafeCell<*mut i32>,
seq: UnsafeCell<i32>
}
impl Condvar {
pub const fn new() -> Condvar {
Condvar {
lock: UnsafeCell::new(ptr::null_mut()),
seq: UnsafeCell::new(0)
}
}
#[inline]
pub unsafe fn init(&self) {
*self.lock.get() = ptr::null_mut();
*self.seq.get() = 0;
}
#[inline]
pub fn notify_one(&self) {
unsafe {
let seq = self.seq.get();
atomic_xadd(seq, 1);
let _ = futex(seq, FUTEX_WAKE, 1, 0, ptr::null_mut());
}
}
#[inline]
pub fn notify_all(&self) {
unsafe {
let lock = self.lock.get();
let seq = self.seq.get();
if *lock == ptr::null_mut() {
return;
}
atomic_xadd(seq, 1);
let _ = futex(seq, FUTEX_REQUEUE, 1, crate::usize::MAX, *lock);
}
}
#[inline]
unsafe fn wait_inner(&self, mutex: &Mutex, timeout_ptr: *const TimeSpec) -> bool {
let lock = self.lock.get();
let seq = self.seq.get();
if *lock != mutex.lock.get() {
if *lock != ptr::null_mut() {
panic!("Condvar used with more than one Mutex");
}
atomic_cxchg(lock as *mut usize, 0, mutex.lock.get() as usize);
}
mutex_unlock(*lock);
let seq_before = atomic_load(seq);
let _ = futex(seq, FUTEX_WAIT, seq_before, timeout_ptr as usize, ptr::null_mut());
let seq_after = atomic_load(seq);
while atomic_xchg(*lock, 2) != 0 {
let _ = futex(*lock, FUTEX_WAIT, 2, 0, ptr::null_mut());
}
seq_before != seq_after
}
#[inline]
pub fn wait(&self, mutex: &Mutex) {
unsafe {
assert!(self.wait_inner(mutex, ptr::null()));
}
}
#[inline]
pub fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
unsafe {
let timeout = TimeSpec {
tv_sec: dur.as_secs() as i64,
tv_nsec: dur.subsec_nanos() as i32
};
self.wait_inner(mutex, &timeout as *const TimeSpec)
}
}
#[inline]
pub unsafe fn destroy(&self) {
*self.lock.get() = ptr::null_mut();
*self.seq.get() = 0;
}
}
unsafe impl Send for Condvar {}
unsafe impl Sync for Condvar {}
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