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extern crate num_cpus; use std::sync::{Arc, Mutex, Condvar}; use std::sync::atomic::{AtomicUsize, Ordering}; use std::collections::VecDeque; use std::thread; use std::time::Duration; trait FnBox { fn call_box(self: Box<Self>); } impl<F: FnOnce()> FnBox for F { fn call_box(self: Box<F>) { (*self)() } } type Truck<'a> = Box<FnBox + Send + 'a>; pub struct Pool { inner: Arc<Inner>, } struct Inner { queue: Mutex<VecDeque<Truck<'static>>>, condvar: Condvar, active: AtomicUsize, waiting: AtomicUsize, min_num: usize, max_num: usize, } struct Count<'a> { num: &'a AtomicUsize, } impl<'a> Count<'a> { fn add(num: &'a AtomicUsize) -> Count<'a> { num.fetch_add(1, Ordering::Release); Count { num: num, } } } impl<'a> Drop for Count<'a> { fn drop(&mut self) { self.num.fetch_sub(1, Ordering::Release); } } impl Pool { pub fn new() -> Pool { let min_num = num_cpus::get(); let max_num = min_num * 16; let pool = Pool { inner: Arc::new(Inner { queue: Mutex::new(VecDeque::with_capacity(max_num * 16)), condvar: Condvar::new(), active: AtomicUsize::new(0), waiting: AtomicUsize::new(0), min_num: min_num, max_num: max_num, }), }; for _ in 0..min_num { pool.thread(); } pool } pub fn with_capacity(min: usize, max: usize) -> Pool { let pool = Pool { inner: Arc::new(Inner { queue: Mutex::new(VecDeque::with_capacity(max)), condvar: Condvar::new(), active: AtomicUsize::new(0), waiting: AtomicUsize::new(0), min_num: min, max_num: max, }) }; for _ in 0..min { pool.thread(); } pool } pub fn spawn<F>(&self, handle: F) where F: FnOnce() + Send + 'static { if self.inner.waiting.load(Ordering::Acquire) == 0 && self.inner.active.load(Ordering::Acquire) < self.inner.max_num + 1 { self.thread(); } let mut queue = self.inner.queue.lock().unwrap(); queue.push_back(Box::new(handle)); self.inner.condvar.notify_one(); } fn thread(&self) { let inner = self.inner.clone(); thread::spawn(move || { let _active = Count::add(&inner.active); loop { let handle = { let mut queue = inner.queue.lock().unwrap(); let handle; loop { if let Some(front) = queue.pop_front() { handle = front; break; } let _waiting = Count::add(&inner.waiting); if inner.active.load(Ordering::Acquire) <= inner.min_num { queue = inner.condvar.wait(queue).unwrap(); } else { let (q, wait) = inner.condvar.wait_timeout(queue, Duration::from_secs(60)).unwrap(); queue = q; if wait.timed_out() && queue.is_empty() && inner.active.load(Ordering::Acquire) > inner.min_num { return; } } } handle }; handle.call_box(); } }); } } impl Drop for Pool { fn drop(&mut self) { self.inner.active.store(usize::max_value(), Ordering::Release); self.inner.condvar.notify_all(); } } #[test] fn test() { let thread_pool = Pool::with_capacity(2, 8); for i in 0..100 { thread_pool.spawn(move || { i * i; }); } thread::sleep(Duration::from_secs(2)); }