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use std::thread;
use std::sync::{mpsc, Arc, Mutex};
trait FnBox {
fn call_box(self: Box<Self>);
}
impl<F: FnOnce()> FnBox for F {
fn call_box(self: Box<Self>) {
(*self)();
}
}
type Job = Box<FnBox + Send + 'static>;
enum Message {
Job(Job),
Halt
}
struct Worker {
id: usize,
thread: Option<thread::JoinHandle<()>>
}
impl Worker {
fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Message>>>) -> Worker {
let thread = thread::spawn(move || {
loop {
let message = receiver.lock().unwrap().recv().unwrap();
match message {
Message::Job(job) => {
debug!("Worker {} picked up a job, executing...", id);
job.call_box();
debug!("Worker {} finished job.", id);
},
Message::Halt => {
debug!("Worker {} terminating.", id);
break;
}
}
}
});
Worker {
id,
thread: Some(thread)
}
}
}
pub struct ThreadPool {
workers: Vec<Worker>,
sender: mpsc::Sender<Message>
}
impl ThreadPool {
pub fn new(size: usize) -> ThreadPool {
assert!(size > 0);
let (sender, receiver) = mpsc::channel();
let receiver = Arc::new(Mutex::new(receiver));
let mut workers = Vec::with_capacity(size);
for id in 0..size {
workers.push(Worker::new(id, Arc::clone(&receiver)));
}
ThreadPool {
workers,
sender
}
}
pub fn assign<F>(&self, f: F)
where
F: FnOnce() + Send + 'static
{
let message = Message::Job(Box::new(f));
self.sender.send(message).unwrap();
}
}
impl Drop for ThreadPool {
fn drop(&mut self) {
for _ in &self.workers {
self.sender.send(Message::Halt).unwrap();
}
for worker in &mut self.workers {
if let Some(thread) = worker.thread.take() {
thread.join().unwrap();
}
}
}
}