pub(crate) mod futures {
    pub(crate) use crate::task::AtomicWaker;
}

pub(crate) mod sync {
    pub(crate) use std::sync::atomic;
    pub(crate) use std::sync::Arc;

    use std::cell::UnsafeCell;

    pub(crate) struct CausalCell<T>(UnsafeCell<T>);

    impl<T> CausalCell<T> {
        pub(crate) fn new(data: T) -> CausalCell<T> {
            CausalCell(UnsafeCell::new(data))
        }

        pub(crate) fn with<F, R>(&self, f: F) -> R
        where
            F: FnOnce(*const T) -> R,
        {
            f(self.0.get())
        }

        pub(crate) fn with_mut<F, R>(&self, f: F) -> R
        where
            F: FnOnce(*mut T) -> R,
        {
            f(self.0.get())
        }
    }
}

pub(crate) fn yield_now() {
    ::std::sync::atomic::spin_loop_hint();
}