src/doc/book/listings/ch20-web-server/no-listing-07-define-message-enum/src/lib.rs

   1 use std::sync::mpsc;
   2 use std::sync::Arc;
   3 use std::sync::Mutex;
   4 use std::thread;
   5
   6 pub struct ThreadPool {
   7     workers: Vec<Worker>,
   8     sender: mpsc::Sender<Job>,
   9 }
  10
  11 type Job = Box<dyn FnOnce() + Send + 'static>;
  12
  13 // ANCHOR: here
  14 enum Message {
  15     NewJob(Job),
  16     Terminate,
  17 }
  18 // ANCHOR_END: here
  19
  20 impl ThreadPool {
  21     /// Create a new ThreadPool.
  22     ///
  23     /// The size is the number of threads in the pool.
  24     ///
  25     /// # Panics
  26     ///
  27     /// The `new` function will panic if the size is zero.
  28     pub fn new(size: usize) -> ThreadPool {
  29         assert!(size > 0);
  30
  31         let (sender, receiver) = mpsc::channel();
  32
  33         let receiver = Arc::new(Mutex::new(receiver));
  34
  35         let mut workers = Vec::with_capacity(size);
  36
  37         for id in 0..size {
  38             workers.push(Worker::new(id, Arc::clone(&receiver)));
  39         }
  40
  41         ThreadPool { workers, sender }
  42     }
  43
  44     pub fn execute<F>(&self, f: F)
  45     where
  46         F: FnOnce() + Send + 'static,
  47     {
  48         let job = Box::new(f);
  49
  50         self.sender.send(job).unwrap();
  51     }
  52 }
  53
  54 impl Drop for ThreadPool {
  55     fn drop(&mut self) {
  56         for worker in &mut self.workers {
  57             println!("Shutting down worker {}", worker.id);
  58
  59             if let Some(thread) = worker.thread.take() {
  60                 thread.join().unwrap();
  61             }
  62         }
  63     }
  64 }
  65
  66 struct Worker {
  67     id: usize,
  68     thread: Option<thread::JoinHandle<()>>,
  69 }
  70
  71 impl Worker {
  72     fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
  73         let thread = thread::spawn(move || loop {
  74             let job = receiver.lock().unwrap().recv().unwrap();
  75
  76             println!("Worker {} got a job; executing.", id);
  77
  78             job();
  79         });
  80
  81         Worker {
  82             id,
  83             thread: Some(thread),
  84         }
  85     }
  86 }