atomic_cell.rs

extern crate crossbeam_utils;

use std::sync::atomic::AtomicUsize;
use std::sync::atomic::Ordering::SeqCst;

use crossbeam_utils::atomic::AtomicCell;

#[test]
fn is_lock_free() {
    struct UsizeWrap(usize);
    struct U8Wrap(bool);

    assert_eq!(AtomicCell::<usize>::is_lock_free(), true);
    assert_eq!(AtomicCell::<isize>::is_lock_free(), true);
    assert_eq!(AtomicCell::<UsizeWrap>::is_lock_free(), true);

    assert_eq!(AtomicCell::<u8>::is_lock_free(), cfg!(feature = "nightly"));
    assert_eq!(
        AtomicCell::<bool>::is_lock_free(),
        cfg!(feature = "nightly")
    );
    assert_eq!(
        AtomicCell::<U8Wrap>::is_lock_free(),
        cfg!(feature = "nightly")
    );
}

#[test]
fn drops_unit() {
    static CNT: AtomicUsize = AtomicUsize::new(0);
    CNT.store(0, SeqCst);

    #[derive(Debug, PartialEq, Eq)]
    struct Foo();

    impl Foo {
        fn new() -> Foo {
            CNT.fetch_add(1, SeqCst);
            Foo()
        }
    }

    impl Drop for Foo {
        fn drop(&mut self) {
            CNT.fetch_sub(1, SeqCst);
        }
    }

    impl Default for Foo {
        fn default() -> Foo {
            Foo::new()
        }
    }

    let a = AtomicCell::new(Foo::new());

    assert_eq!(a.swap(Foo::new()), Foo::new());
    assert_eq!(CNT.load(SeqCst), 1);

    a.store(Foo::new());
    assert_eq!(CNT.load(SeqCst), 1);

    assert_eq!(a.swap(Foo::default()), Foo::new());
    assert_eq!(CNT.load(SeqCst), 1);

    drop(a);
    assert_eq!(CNT.load(SeqCst), 0);
}

#[test]
fn drops_u8() {
    static CNT: AtomicUsize = AtomicUsize::new(0);
    CNT.store(0, SeqCst);

    #[derive(Debug, PartialEq, Eq)]
    struct Foo(u8);

    impl Foo {
        fn new(val: u8) -> Foo {
            CNT.fetch_add(1, SeqCst);
            Foo(val)
        }
    }

    impl Drop for Foo {
        fn drop(&mut self) {
            CNT.fetch_sub(1, SeqCst);
        }
    }

    impl Default for Foo {
        fn default() -> Foo {
            Foo::new(0)
        }
    }

    let a = AtomicCell::new(Foo::new(5));

    assert_eq!(a.swap(Foo::new(6)), Foo::new(5));
    assert_eq!(a.swap(Foo::new(1)), Foo::new(6));
    assert_eq!(CNT.load(SeqCst), 1);

    a.store(Foo::new(2));
    assert_eq!(CNT.load(SeqCst), 1);

    assert_eq!(a.swap(Foo::default()), Foo::new(2));
    assert_eq!(CNT.load(SeqCst), 1);

    assert_eq!(a.swap(Foo::default()), Foo::new(0));
    assert_eq!(CNT.load(SeqCst), 1);

    drop(a);
    assert_eq!(CNT.load(SeqCst), 0);
}

#[test]
fn drops_usize() {
    static CNT: AtomicUsize = AtomicUsize::new(0);
    CNT.store(0, SeqCst);

    #[derive(Debug, PartialEq, Eq)]
    struct Foo(usize);

    impl Foo {
        fn new(val: usize) -> Foo {
            CNT.fetch_add(1, SeqCst);
            Foo(val)
        }
    }

    impl Drop for Foo {
        fn drop(&mut self) {
            CNT.fetch_sub(1, SeqCst);
        }
    }

    impl Default for Foo {
        fn default() -> Foo {
            Foo::new(0)
        }
    }

    let a = AtomicCell::new(Foo::new(5));

    assert_eq!(a.swap(Foo::new(6)), Foo::new(5));
    assert_eq!(a.swap(Foo::new(1)), Foo::new(6));
    assert_eq!(CNT.load(SeqCst), 1);

    a.store(Foo::new(2));
    assert_eq!(CNT.load(SeqCst), 1);

    assert_eq!(a.swap(Foo::default()), Foo::new(2));
    assert_eq!(CNT.load(SeqCst), 1);

    assert_eq!(a.swap(Foo::default()), Foo::new(0));
    assert_eq!(CNT.load(SeqCst), 1);

    drop(a);
    assert_eq!(CNT.load(SeqCst), 0);
}

#[test]
fn modular_u8() {
    #[derive(Clone, Copy, Eq, Debug, Default)]
    struct Foo(u8);

    impl PartialEq for Foo {
        fn eq(&self, other: &Foo) -> bool {
            self.0 % 5 == other.0 % 5
        }
    }

    let a = AtomicCell::new(Foo(1));

    assert_eq!(a.load(), Foo(1));
    assert_eq!(a.swap(Foo(2)), Foo(11));
    assert_eq!(a.load(), Foo(52));

    a.store(Foo(0));
    assert_eq!(a.compare_exchange(Foo(0), Foo(5)), Ok(Foo(100)));
    assert_eq!(a.load().0, 5);
    assert_eq!(a.compare_exchange(Foo(10), Foo(15)), Ok(Foo(100)));
    assert_eq!(a.load().0, 15);
}

#[test]
fn modular_usize() {
    #[derive(Clone, Copy, Eq, Debug, Default)]
    struct Foo(usize);

    impl PartialEq for Foo {
        fn eq(&self, other: &Foo) -> bool {
            self.0 % 5 == other.0 % 5
        }
    }

    let a = AtomicCell::new(Foo(1));

    assert_eq!(a.load(), Foo(1));
    assert_eq!(a.swap(Foo(2)), Foo(11));
    assert_eq!(a.load(), Foo(52));

    a.store(Foo(0));
    assert_eq!(a.compare_exchange(Foo(0), Foo(5)), Ok(Foo(100)));
    assert_eq!(a.load().0, 5);
    assert_eq!(a.compare_exchange(Foo(10), Foo(15)), Ok(Foo(100)));
    assert_eq!(a.load().0, 15);
}

#[test]
fn garbage_padding() {
    #[derive(Copy, Clone, Eq, PartialEq)]
    struct Object {
        a: i64,
        b: i32,
    }

    let cell = AtomicCell::new(Object { a: 0, b: 0 });
    let _garbage = [0xfe, 0xfe, 0xfe, 0xfe, 0xfe]; // Needed
    let next = Object { a: 0, b: 0 };

    let prev = cell.load();
    assert!(cell.compare_exchange(prev, next).is_ok());
    println!();
}

#[cfg(has_min_const_fn)]
#[test]
fn const_atomic_cell_new() {
    static CELL: AtomicCell<usize> = AtomicCell::new(0);

    CELL.store(1);
    assert_eq!(CELL.load(), 1);
}