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#![warn(missing_docs)]
use std::ops::{Deref, DerefMut};
use std::sync::atomic::{AtomicIsize, AtomicUsize, Ordering};
use std::sync::{Arc, Weak};
use async_trait::async_trait;
use tokio::sync::mpsc::{channel, Receiver, Sender};
use tokio::sync::Mutex;
#[cfg(feature = "postgres")]
pub mod postgres;
#[async_trait]
pub trait Manager<T, E> {
async fn create(&self) -> Result<T, E>;
async fn recycle(&self, obj: T) -> Result<T, E>;
}
pub struct Object<T, E> {
obj: Option<T>,
pool: Weak<PoolInner<T, E>>,
}
impl<T, E> Object<T, E> {
fn new(pool: &Pool<T, E>, obj: T) -> Object<T, E> {
Object {
obj: Some(obj),
pool: Arc::downgrade(&pool.inner),
}
}
}
impl<T, E> Drop for Object<T, E> {
fn drop(&mut self) {
if let Some(pool) = self.pool.upgrade() {
pool.return_obj(self.obj.take().unwrap());
}
}
}
impl<T, E> Deref for Object<T, E> {
type Target = T;
fn deref(&self) -> &T {
self.obj.as_ref().unwrap()
}
}
impl<T, E> DerefMut for Object<T, E> {
fn deref_mut(&mut self) -> &mut T {
self.obj.as_mut().unwrap()
}
}
#[derive(Default)]
struct PoolSize {
current: AtomicUsize,
available: AtomicIsize,
}
struct PoolInner<T, E> {
manager: Box<dyn Manager<T, E> + Sync + Send>,
max_size: usize,
obj_sender: Sender<T>,
obj_receiver: Mutex<Receiver<T>>,
size: PoolSize,
}
impl<T, E> PoolInner<T, E> {
fn return_obj(&self, obj: T) {
self.size.available.fetch_add(1, Ordering::SeqCst);
self.obj_sender
.clone()
.try_send(obj)
.map_err(|_| ())
.unwrap();
}
}
pub struct Pool<T, E> {
inner: Arc<PoolInner<T, E>>,
}
impl<T, E> Clone for Pool<T, E> {
fn clone(&self) -> Pool<T, E> {
Pool {
inner: self.inner.clone(),
}
}
}
impl<T, E> Pool<T, E> {
pub fn new(manager: impl Manager<T, E> + Send + Sync + 'static, max_size: usize) -> Pool<T, E> {
let (obj_sender, obj_receiver) = channel::<T>(max_size);
Pool {
inner: Arc::new(PoolInner {
max_size: max_size,
manager: Box::new(manager),
obj_sender: obj_sender,
obj_receiver: Mutex::new(obj_receiver),
size: PoolSize::default(),
}),
}
}
pub async fn get(&self) -> Result<Object<T, E>, E> {
let available = self.inner.size.available.fetch_sub(1, Ordering::SeqCst);
if available <= 0 && self.inner.size.current.load(Ordering::SeqCst) < self.inner.max_size {
let current = self.inner.size.current.fetch_add(1, Ordering::SeqCst);
if current < self.inner.max_size {
self.inner.size.available.fetch_add(1, Ordering::SeqCst);
let obj = self.inner.manager.create().await?;
return Ok(Object::new(&self, obj));
}
}
let obj = self.inner.obj_receiver.lock().await.recv().await.unwrap();
let obj = self.inner.manager.recycle(obj).await?;
Ok(Object::new(&self, obj))
}
}