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use std::thread;
use crossbeam_channel::{bounded, unbounded, Sender, Receiver};
use drop_bomb::DropBomb;
use Result;
pub struct Worker<I, O> {
pub inp: Sender<I>,
pub out: Receiver<O>,
}
impl<I, O> Worker<I, O> {
pub fn spawn<F>(name: &'static str, buf: usize, f: F) -> (Self, ThreadWatcher)
where
F: FnOnce(Receiver<I>, Sender<O>) + Send + 'static,
I: Send + 'static,
O: Send + 'static,
{
let ((inp, out), inp_r, out_s) = worker_chan(buf);
let worker = Worker { inp, out };
let watcher = ThreadWatcher::spawn(name, move || f(inp_r, out_s));
(worker, watcher)
}
pub fn stop(self) -> Receiver<O> {
self.out
}
pub fn send(&self, item: I) {
self.inp.send(item)
}
}
pub struct ThreadWatcher {
name: &'static str,
thread: thread::JoinHandle<()>,
bomb: DropBomb,
}
impl ThreadWatcher {
fn spawn(name: &'static str, f: impl FnOnce() + Send + 'static) -> ThreadWatcher {
let thread = thread::spawn(f);
ThreadWatcher {
name,
thread,
bomb: DropBomb::new(format!("ThreadWatcher {} was not stopped", name)),
}
}
pub fn stop(mut self) -> Result<()> {
info!("waiting for {} to finish ...", self.name);
let name = self.name;
self.bomb.defuse();
let res = self.thread.join()
.map_err(|_| format_err!("ThreadWatcher {} died", name));
match &res {
Ok(()) => info!("... {} terminated with ok", name),
Err(_) => error!("... {} terminated with err", name)
}
res
}
}
/// Sets up worker channels in a deadlock-avoind way.
/// If one sets both input and output buffers to a fixed size,
/// a worker might get stuck.
fn worker_chan<I, O>(buf: usize) -> ((Sender<I>, Receiver<O>), Receiver<I>, Sender<O>) {
let (input_sender, input_receiver) = bounded::<I>(buf);
let (output_sender, output_receiver) = unbounded::<O>();
((input_sender, output_receiver), input_receiver, output_sender)
}
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