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use crate::cell::Cell;
pub struct RwLock {
// This platform has no threads, so we can use a Cell here.
mode: Cell<isize>,
}
pub type MovableRwLock = RwLock;
unsafe impl Send for RwLock {}
unsafe impl Sync for RwLock {} // no threads on this platform
impl RwLock {
#[inline]
#[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
pub const fn new() -> RwLock {
RwLock { mode: Cell::new(0) }
}
#[inline]
pub unsafe fn read(&self) {
let m = self.mode.get();
if m >= 0 {
self.mode.set(m + 1);
} else {
rtabort!("rwlock locked for writing");
}
}
#[inline]
pub unsafe fn try_read(&self) -> bool {
let m = self.mode.get();
if m >= 0 {
self.mode.set(m + 1);
true
} else {
false
}
}
#[inline]
pub unsafe fn write(&self) {
if self.mode.replace(-1) != 0 {
rtabort!("rwlock locked for reading")
}
}
#[inline]
pub unsafe fn try_write(&self) -> bool {
if self.mode.get() == 0 {
self.mode.set(-1);
true
} else {
false
}
}
#[inline]
pub unsafe fn read_unlock(&self) {
self.mode.set(self.mode.get() - 1);
}
#[inline]
pub unsafe fn write_unlock(&self) {
assert_eq!(self.mode.replace(0), -1);
}
}
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