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use std::sync::mpsc;
use std::sync::Arc;
use std::sync::Mutex;
use std::thread;
pub struct ThreadPool {
workers: Vec<Worker>,
sender: mpsc::Sender<Job>,
}
type Job = Box<dyn FnOnce() + Send + 'static>;
// ANCHOR: here
enum Message {
NewJob(Job),
Terminate,
}
// ANCHOR_END: here
impl ThreadPool {
/// Create a new ThreadPool.
///
/// The size is the number of threads in the pool.
///
/// # Panics
///
/// The `new` function will panic if the size is zero.
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(job).unwrap();
}
}
impl Drop for ThreadPool {
fn drop(&mut self) {
for worker in &mut self.workers {
println!("Shutting down worker {}", worker.id);
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<Job>>>) -> Worker {
let thread = thread::spawn(move || loop {
let job = receiver.lock().unwrap().recv().unwrap();
println!("Worker {} got a job; executing.", id);
job();
});
Worker {
id,
thread: Some(thread),
}
}
}