use crate::slot_guard::SlotGuard;
use std::collections::VecDeque;
use std::sync::Mutex;
use tokio::sync::Semaphore;
pub struct SlotPool {
semaphore: Semaphore,
free_slots: Mutex<VecDeque<usize>>,
}
impl SlotPool {
pub fn new(max_parallel: usize) -> Self {
Self {
semaphore: Semaphore::new(max_parallel),
free_slots: Mutex::new((0..max_parallel).collect()),
}
}
pub async fn acquire(&self) -> SlotGuard<'_> {
let permit = self
.semaphore
.acquire()
.await
.expect("slot pool semaphore should never be closed");
let slot_index = self
.free_slots
.lock()
.expect("free_slots lock poisoned")
.pop_front()
.expect("a semaphore permit implies a free slot is available");
SlotGuard::new(self, slot_index, permit)
}
pub(crate) fn release(&self, slot_index: usize) {
self.free_slots
.lock()
.expect("free_slots lock poisoned")
.push_back(slot_index);
}
}