src/doc/book/listings/ch20-web-server/listing-20-25/src/lib.rs

   1 use std::{
   2     sync::{mpsc, Arc, Mutex},
   3     thread,
   4 };
   5
   6 pub struct ThreadPool {
   7     workers: Vec<Worker>,
   8     sender: Option<mpsc::Sender<Job>>,
   9 }
  10
  11 type Job = Box<dyn FnOnce() + Send + 'static>;
  12
  13 impl ThreadPool {
  14     /// Create a new ThreadPool.
  15     ///
  16     /// The size is the number of threads in the pool.
  17     ///
  18     /// # Panics
  19     ///
  20     /// The `new` function will panic if the size is zero.
  21     pub fn new(size: usize) -> ThreadPool {
  22         assert!(size > 0);
  23
  24         let (sender, receiver) = mpsc::channel();
  25
  26         let receiver = Arc::new(Mutex::new(receiver));
  27
  28         let mut workers = Vec::with_capacity(size);
  29
  30         for id in 0..size {
  31             workers.push(Worker::new(id, Arc::clone(&receiver)));
  32         }
  33
  34         ThreadPool {
  35             workers,
  36             sender: Some(sender),
  37         }
  38     }
  39
  40     pub fn execute<F>(&self, f: F)
  41     where
  42         F: FnOnce() + Send + 'static,
  43     {
  44         let job = Box::new(f);
  45
  46         self.sender.as_ref().unwrap().send(job).unwrap();
  47     }
  48 }
  49
  50 impl Drop for ThreadPool {
  51     fn drop(&mut self) {
  52         drop(self.sender.take());
  53
  54         for worker in &mut self.workers {
  55             println!("Shutting down worker {}", worker.id);
  56
  57             if let Some(thread) = worker.thread.take() {
  58                 thread.join().unwrap();
  59             }
  60         }
  61     }
  62 }
  63
  64 struct Worker {
  65     id: usize,
  66     thread: Option<thread::JoinHandle<()>>,
  67 }
  68
  69 impl Worker {
  70     fn new(id: usize, receiver: Arc<Mutex<mpsc::Receiver<Job>>>) -> Worker {
  71         let thread = thread::spawn(move || loop {
  72             let message = receiver.lock().unwrap().recv();
  73
  74             match message {
  75                 Ok(job) => {
  76                     println!("Worker {id} got a job; executing.");
  77
  78                     job();
  79                 }
  80                 Err(_) => {
  81                     println!("Worker {id} disconnected; shutting down.");
  82                     break;
  83                 }
  84             }
  85         });
  86
  87         Worker {
  88             id,
  89             thread: Some(thread),
  90         }
  91     }
  92 }