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use std::fmt::{self, Display, Formatter};
mod internal;
#[derive(Debug)]
pub struct Counter {
counter: internal::Counter,
size: usize,
}
#[derive(Clone, Debug)]
pub struct WeakCounter {
counter: internal::Counter,
}
impl Counter {
pub fn new() -> Counter {
Counter::new_with_size(1)
}
pub fn new_with_size(size: usize) -> Counter {
Counter {
counter: internal::Counter::new(1),
size,
}
}
pub fn downgrade(self) -> WeakCounter {
WeakCounter {
counter: self.counter.clone(),
}
}
#[inline]
pub fn count(&self) -> usize {
self.counter.get()
}
pub async fn wait_for_empty(&self) {
self.counter.wait_for_empty().await;
}
}
impl Clone for Counter {
fn clone(&self) -> Self {
self.counter.fetch_add(self.size);
Counter {
counter: self.counter.clone(),
size: self.size,
}
}
}
impl Display for Counter {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
write!(f, "Counter(count={})", self.count())
}
}
impl Drop for Counter {
fn drop(&mut self) {
self.counter.fetch_sub(self.size);
}
}
impl WeakCounter {
pub fn new() -> WeakCounter {
WeakCounter {
counter: internal::Counter::new(0),
}
}
#[inline]
pub fn count(&self) -> usize {
self.counter.get()
}
pub fn upgrade(self) -> Counter {
self.spawn_upgrade()
}
pub fn spawn_upgrade(&self) -> Counter {
self.spawn_upgrade_with_size(1)
}
pub fn spawn_upgrade_with_size(&self, size: usize) -> Counter {
self.counter.fetch_add(size);
Counter {
counter: self.counter.clone(),
size,
}
}
pub async fn wait_for_empty(&self) {
self.counter.wait_for_empty().await;
}
}
impl Display for WeakCounter {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
write!(f, "WeakCounter(count={})", self.count())
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::time::{Duration, Instant};
use tokio::time::delay_for;
#[test]
fn it_works() {
let counter = Counter::new();
assert_eq!(counter.count(), 1);
let weak = counter.downgrade();
assert_eq!(weak.count(), 0);
{
let _counter1 = weak.spawn_upgrade();
assert_eq!(weak.count(), 1);
let _counter2 = weak.spawn_upgrade();
assert_eq!(weak.count(), 2);
}
assert_eq!(weak.count(), 0);
}
#[test]
fn different_sizes_work() {
let weak = WeakCounter::new();
assert_eq!(weak.count(), 0);
let counter = weak.spawn_upgrade_with_size(5);
assert_eq!(weak.count(), 5);
{
let _counter1 = counter.clone();
assert_eq!(weak.count(), 10);
let _counter2 = weak.spawn_upgrade();
assert_eq!(weak.count(), 11);
}
assert_eq!(weak.count(), 5);
}
#[tokio::test]
async fn test_wait_for_empty_works() {
let start = Instant::now();
let weak = WeakCounter::new();
let counter1 = weak.spawn_upgrade();
let counter2 = counter1.clone();
let counter3 = counter2.clone();
tokio::spawn(async move {
delay_for(Duration::from_millis(250)).await;
drop(counter1);
delay_for(Duration::from_millis(500)).await;
drop(counter2);
delay_for(Duration::from_millis(100)).await;
drop(counter3);
});
weak.wait_for_empty().await;
let elapsed = start.elapsed();
assert!(elapsed >= Duration::from_millis(850));
assert!(elapsed < Duration::from_millis(900));
}
}