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|
//! provides `AsyncJob` trait and `AsyncSingleJob` struct
#![deny(clippy::expect_used)]
use crate::error::Result;
use crossbeam_channel::Sender;
use std::sync::{Arc, Mutex};
/// trait that defines an async task we can run on a threadpool
pub trait AsyncJob: Send + Sync + Clone {
/// can run a synchronous time intensive task
fn run(&mut self);
}
/// Abstraction for a FIFO task queue that will only queue up **one** `next` job.
/// It keeps overwriting the next job until it is actually taken to be processed
#[derive(Debug, Clone)]
pub struct AsyncSingleJob<J: AsyncJob, T: Copy + Send + 'static> {
next: Arc<Mutex<Option<J>>>,
last: Arc<Mutex<Option<J>>>,
sender: Sender<T>,
pending: Arc<Mutex<()>>,
notification: T,
}
impl<J: 'static + AsyncJob, T: Copy + Send + 'static>
AsyncSingleJob<J, T>
{
///
pub fn new(sender: Sender<T>, value: T) -> Self {
Self {
next: Arc::new(Mutex::new(None)),
last: Arc::new(Mutex::new(None)),
pending: Arc::new(Mutex::new(())),
notification: value,
sender,
}
}
///
pub fn is_pending(&self) -> bool {
self.pending.try_lock().is_err()
}
/// makes sure `next` is cleared and returns `true` if it actually canceled something
pub fn cancel(&mut self) -> bool {
if let Ok(mut next) = self.next.lock() {
if next.is_some() {
*next = None;
return true;
}
}
false
}
/// take out last finished job
pub fn take_last(&self) -> Option<J> {
if let Ok(mut last) = self.last.lock() {
last.take()
} else {
None
}
}
/// spawns `task` if nothing is running currently, otherwise schedules as `next` overwriting if `next` was set before
pub fn spawn(&mut self, task: J) -> bool {
self.schedule_next(task);
self.check_for_job()
}
fn check_for_job(&self) -> bool {
if self.is_pending() {
return false;
}
if let Some(task) = self.take_next() {
let self_arc = self.clone();
rayon_core::spawn(move || {
if let Err(e) = self_arc.run_job(task) {
log::error!("async job error: {}", e);
}
});
return true;
}
false
}
fn run_job(&self, mut task: J) -> Result<()> {
//limit the pending scope
{
let _pending = self.pending.lock()?;
task.run();
if let Ok(mut last) = self.last.lock() {
*last = Some(task);
}
self.sender.send(self.notification)?;
}
self.check_for_job();
Ok(())
}
fn schedule_next(&mut self, task: J) {
if let Ok(mut next) = self.next.lock() {
*next = Some(task);
}
}
fn take_next(&self) -> Option<J> {
if let Ok(mut next) = self.next.lock() {
next.take()
} else {
None
}
}
}
#[cfg(test)]
mod test {
use super::*;
use crossbeam_channel::unbounded;
use pretty_assertions::assert_eq;
use std::{
sync::atomic::AtomicU32, thread::sleep, time::Duration,
};
#[derive(Clone)]
struct TestJob {
v: Arc<AtomicU32>,
value_to_add: u32,
}
impl AsyncJob for TestJob {
fn run(&mut self) {
sleep(Duration::from_millis(100));
self.v.fetch_add(
self.value_to_add,
std::sync::atomic::Ordering::Relaxed,
);
}
}
type Notificaton = ();
#[test]
fn test_overwrite() {
let (sender, receiver) = unbounded();
let mut job: AsyncSingleJob<TestJob, Notificaton> =
AsyncSingleJob::new(sender, ());
let task = TestJob {
v: Arc::new(AtomicU32::new(1)),
value_to_add: 1,
};
assert!(job.spawn(task.clone()));
sleep(Duration::from_millis(1));
for _ in 0..5 {
assert!(!job.spawn(task.clone()));
}
let _foo = receiver.recv().unwrap();
let _foo = receiver.recv().unwrap();
assert!(receiver.is_empty());
assert_eq!(
task.v.load(std::sync::atomic::Ordering::Relaxed),
3
);
}
#[test]
fn test_cancel() {
let (sender, receiver) = unbounded();
let mut job: AsyncSingleJob<TestJob, Notificaton> =
AsyncSingleJob::new(sender, ());
let task = TestJob {
v: Arc::new(AtomicU32::new(1)),
value_to_add: 1,
};
assert!(job.spawn(task.clone()));
sleep(Duration::from_millis(1));
for _ in 0..5 {
assert!(!job.spawn(task.clone()));
}
assert!(job.cancel());
let _foo = receiver.recv().unwrap();
assert_eq!(
task.v.load(std::sync::atomic::Ordering::Relaxed),
2
);
}
}
|
