tokio 0.2.4

use crate::sync::semaphore::*;

use futures::future::poll_fn;
use loom::future::block_on;
use loom::thread;
use std::future::Future;
use std::pin::Pin;
use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering::SeqCst;
use std::sync::Arc;
use std::task::Poll::Ready;
use std::task::{Context, Poll};

#[test]
fn basic_usage() {
    const NUM: usize = 2;

    struct Actor {
        waiter: Permit,
        shared: Arc<Shared>,
    }

    struct Shared {
        semaphore: Semaphore,
        active: AtomicUsize,
    }

    impl Future for Actor {
        type Output = ();

        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
            let me = &mut *self;

            ready!(me.waiter.poll_acquire(cx, &me.shared.semaphore)).unwrap();

            let actual = me.shared.active.fetch_add(1, SeqCst);
            assert!(actual <= NUM - 1);

            let actual = me.shared.active.fetch_sub(1, SeqCst);
            assert!(actual <= NUM);

            me.waiter.release(&me.shared.semaphore);

            Ready(())
        }
    }

    loom::model(|| {
        let shared = Arc::new(Shared {
            semaphore: Semaphore::new(NUM),
            active: AtomicUsize::new(0),
        });

        for _ in 0..NUM {
            let shared = shared.clone();

            thread::spawn(move || {
                block_on(Actor {
                    waiter: Permit::new(),
                    shared,
                });
            });
        }

        block_on(Actor {
            waiter: Permit::new(),
            shared,
        });
    });
}

#[test]
fn release() {
    loom::model(|| {
        let semaphore = Arc::new(Semaphore::new(1));

        {
            let semaphore = semaphore.clone();
            thread::spawn(move || {
                let mut permit = Permit::new();

                block_on(poll_fn(|cx| permit.poll_acquire(cx, &semaphore))).unwrap();

                permit.release(&semaphore);
            });
        }

        let mut permit = Permit::new();

        block_on(poll_fn(|cx| permit.poll_acquire(cx, &semaphore))).unwrap();

        permit.release(&semaphore);
    });
}

#[test]
fn basic_closing() {
    const NUM: usize = 2;

    loom::model(|| {
        let semaphore = Arc::new(Semaphore::new(1));

        for _ in 0..NUM {
            let semaphore = semaphore.clone();

            thread::spawn(move || {
                let mut permit = Permit::new();

                for _ in 0..2 {
                    block_on(poll_fn(|cx| {
                        permit.poll_acquire(cx, &semaphore).map_err(|_| ())
                    }))?;

                    permit.release(&semaphore);
                }

                Ok::<(), ()>(())
            });
        }

        semaphore.close();
    });
}

#[test]
fn concurrent_close() {
    const NUM: usize = 3;

    loom::model(|| {
        let semaphore = Arc::new(Semaphore::new(1));

        for _ in 0..NUM {
            let semaphore = semaphore.clone();

            thread::spawn(move || {
                let mut permit = Permit::new();

                block_on(poll_fn(|cx| {
                    permit.poll_acquire(cx, &semaphore).map_err(|_| ())
                }))?;

                permit.release(&semaphore);

                semaphore.close();

                Ok::<(), ()>(())
            });
        }
    });
}