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    //! Thread local runtime context
    use crate::runtime::Handle;

    use std::cell::RefCell;

    thread_local! {
        static CONTEXT: RefCell<Option<Handle>> = RefCell::new(None)
    }

    pub(crate) fn current() -> Option<Handle> {
        CONTEXT.with(|ctx| ctx.borrow().clone())
    }

    cfg_io_driver! {
        pub(crate) fn io_handle() -> crate::runtime::driver::IoHandle {
            CONTEXT.with(|ctx| match *ctx.borrow() {
                Some(ref ctx) => ctx.io_handle.clone(),
                None => Default::default(),
            })
        }
    }

    cfg_signal_internal! {
        #[cfg(unix)]
        pub(crate) fn signal_handle() -> crate::runtime::driver::SignalHandle {
            CONTEXT.with(|ctx| match *ctx.borrow() {
                Some(ref ctx) => ctx.signal_handle.clone(),
                None => Default::default(),
            })
        }
    }

    cfg_time! {
        pub(crate) fn time_handle() -> crate::runtime::driver::TimeHandle {
            CONTEXT.with(|ctx| match *ctx.borrow() {
                Some(ref ctx) => ctx.time_handle.clone(),
                None => Default::default(),
            })
        }

        cfg_test_util! {
            pub(crate) fn clock() -> Option<crate::runtime::driver::Clock> {
                CONTEXT.with(|ctx| match *ctx.borrow() {
                    Some(ref ctx) => Some(ctx.clock.clone()),
                    None => None,
                })
            }
        }
    }

    cfg_rt! {
        pub(crate) fn spawn_handle() -> Option<crate::runtime::Spawner> {
            CONTEXT.with(|ctx| match *ctx.borrow() {
                Some(ref ctx) => Some(ctx.spawner.clone()),
                None => None,
            })
        }
    }

    /// Set this [`Handle`] as the current active [`Handle`].
    ///
    /// [`Handle`]: Handle
    pub(crate) fn enter(new: Handle) -> EnterGuard {
        CONTEXT.with(|ctx| {
            let old = ctx.borrow_mut().replace(new);
            EnterGuard(old)
        })
    }

    #[derive(Debug)]
    pub(crate) struct EnterGuard(Option<Handle>);

    impl Drop for EnterGuard {
        fn drop(&mut self) {
            CONTEXT.with(|ctx| {
                *ctx.borrow_mut() = self.0.take();
            });
        }
    }