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use std::thread; use std::sync::mpsc; use std::sync::Arc; use std::sync::Mutex; enum Message { NewJob(Job), Terminate, } pub struct ThreadPool { workers: Vec<Worker>, sender: mpsc::Sender<Message>, } trait FnBox { fn call_box(self: Box<Self>); } impl<F: FnOnce()> FnBox for F { fn call_box(self: Box<F>) { (*self)() } } type Job = Box<dyn FnBox + Send + 'static>; 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 execute<F>(&self, f: F) where F: FnOnce() + Send + 'static { let job = Box::new(f); self.sender.send(Message::NewJob(job)).unwrap(); } } impl Drop for ThreadPool { fn drop(&mut self) { for _ in &mut self.workers { self.sender.send(Message::Terminate).unwrap(); } for worker in &mut self.workers { if let Some(thread) = worker.thread.take() { thread.join().unwrap(); } } } } 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::NewJob(job) => { job.call_box(); }, Message::Terminate => { break; }, } } }); Worker { id, thread: Some(thread), } } }