use crossbeam_channel::{bounded, Receiver, Sender};
use std::ops::{Deref, DerefMut};
pub struct OwnedPool<T> {
free: Vec<T>,
num_borrowed: usize,
receiver: Receiver<T>,
sender: Sender<T>,
reset_fn: fn(&mut T),
init_fn: fn() -> T,
}
impl<T> OwnedPool<T> {
pub fn with_capacity(
pool_size: usize,
init_fn: fn() -> T,
reset_fn: fn(&mut T),
) -> Self {
let (sender, receiver) = bounded(pool_size);
Self {
free: Vec::with_capacity(pool_size),
num_borrowed: 0,
init_fn,
reset_fn,
sender,
receiver,
}
}
pub fn borrow(&mut self) -> Pooled<T> {
if let Some(mut pooled_val) = self.free.pop() {
self.num_borrowed += 1;
(self.reset_fn)(&mut pooled_val);
Pooled {
inner: Some(pooled_val),
sender: self.sender.clone(),
}
} else if self.num_borrowed < self.free.capacity() {
self.num_borrowed += 1;
Pooled {
inner: Some((self.init_fn)()),
sender: self.sender.clone(),
}
} else {
panic!("Cannot borrow more than `pool_size` entries.");
}
}
pub fn try_recv(&mut self) {
for pooled_val in self.receiver.try_iter() {
self.free.push(pooled_val);
self.num_borrowed -= 1;
}
}
}
pub struct Pooled<T> {
inner: Option<T>,
sender: Sender<T>,
}
impl<T> Pooled<T> {
pub fn as_ref(&self) -> &T {
self.inner.as_ref().unwrap()
}
pub fn as_mut(&mut self) -> &mut T {
self.inner.as_mut().unwrap()
}
}
impl<T> Deref for Pooled<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
self.inner.as_ref().unwrap()
}
}
impl<T> DerefMut for Pooled<T> {
fn deref_mut(&mut self) -> &mut Self::Target {
self.inner.as_mut().unwrap()
}
}
impl<T> Drop for Pooled<T> {
fn drop(&mut self) {
let inner = std::mem::take(&mut self.inner);
let _ = self.sender.send(inner.unwrap());
}
}