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    use crate::time::Duration;
    use crate::sys_common::mutex::{self, Mutex};
    use crate::sys::condvar as imp;

    /// An OS-based condition variable.
    ///
    /// This structure is the lowest layer possible on top of the OS-provided
    /// condition variables. It is consequently entirely unsafe to use. It is
    /// recommended to use the safer types at the top level of this crate instead of
    /// this type.
    pub struct Condvar(imp::Condvar);

    impl Condvar {
        /// Creates a new condition variable for use.
        ///
        /// Behavior is undefined if the condition variable is moved after it is
        /// first used with any of the functions below.
        pub const fn new() -> Condvar { Condvar(imp::Condvar::new()) }

        /// Prepares the condition variable for use.
        ///
        /// This should be called once the condition variable is at a stable memory
        /// address.
        #[inline]
        pub unsafe fn init(&mut self) { self.0.init() }

        /// Signals one waiter on this condition variable to wake up.
        #[inline]
        pub unsafe fn notify_one(&self) { self.0.notify_one() }

        /// Awakens all current waiters on this condition variable.
        #[inline]
        pub unsafe fn notify_all(&self) { self.0.notify_all() }

        /// Waits for a signal on the specified mutex.
        ///
        /// Behavior is undefined if the mutex is not locked by the current thread.
        /// Behavior is also undefined if more than one mutex is used concurrently
        /// on this condition variable.
        #[inline]
        pub unsafe fn wait(&self, mutex: &Mutex) { self.0.wait(mutex::raw(mutex)) }

        /// Waits for a signal on the specified mutex with a timeout duration
        /// specified by `dur` (a relative time into the future).
        ///
        /// Behavior is undefined if the mutex is not locked by the current thread.
        /// Behavior is also undefined if more than one mutex is used concurrently
        /// on this condition variable.
        #[inline]
        pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
            self.0.wait_timeout(mutex::raw(mutex), dur)
        }

        /// Deallocates all resources associated with this condition variable.
        ///
        /// Behavior is undefined if there are current or will be future users of
        /// this condition variable.
        #[inline]
        pub unsafe fn destroy(&self) { self.0.destroy() }
    }