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use super::batch_semaphore as ll;
use crate::coop::CoopFutureExt;
#[derive(Debug)]
pub struct Semaphore {
ll_sem: ll::Semaphore,
}
#[must_use]
#[derive(Debug)]
pub struct SemaphorePermit<'a> {
sem: &'a Semaphore,
permits: u16,
}
#[derive(Debug)]
pub struct TryAcquireError(());
#[test]
#[cfg(not(loom))]
fn bounds() {
fn check_unpin<T: Unpin>() {}
check_unpin::<Semaphore>();
check_unpin::<SemaphorePermit<'_>>();
}
impl Semaphore {
pub fn new(permits: usize) -> Self {
Self {
ll_sem: ll::Semaphore::new(permits),
}
}
pub fn available_permits(&self) -> usize {
self.ll_sem.available_permits()
}
pub fn add_permits(&self, n: usize) {
self.ll_sem.release(n);
}
pub async fn acquire(&self) -> SemaphorePermit<'_> {
self.ll_sem.acquire(1).cooperate().await.unwrap();
SemaphorePermit {
sem: &self,
permits: 1,
}
}
pub fn try_acquire(&self) -> Result<SemaphorePermit<'_>, TryAcquireError> {
match self.ll_sem.try_acquire(1) {
Ok(_) => Ok(SemaphorePermit {
sem: self,
permits: 1,
}),
Err(_) => Err(TryAcquireError(())),
}
}
}
impl<'a> SemaphorePermit<'a> {
pub fn forget(mut self) {
self.permits = 0;
}
}
impl<'a> Drop for SemaphorePermit<'_> {
fn drop(&mut self) {
self.sem.add_permits(self.permits as usize);
}
}