# driver.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.4.0/src/runtime/driver.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Abstracts out the entire chain of runtime sub-drivers into common types.
    use crate::park::thread::ParkThread;
    use crate::park::Park;

    use std::io;
    use std::time::Duration;

    // ===== io driver =====

    cfg_io_driver! {
        type IoDriver = crate::io::driver::Driver;
        type IoStack = crate::park::either::Either<ProcessDriver, ParkThread>;
        pub(crate) type IoHandle = Option<crate::io::driver::Handle>;

        fn create_io_stack(enabled: bool) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
            use crate::park::either::Either;

            #[cfg(loom)]
            assert!(!enabled);

            let ret = if enabled {
                let io_driver = crate::io::driver::Driver::new()?;
                let io_handle = io_driver.handle();

                let (signal_driver, signal_handle) = create_signal_driver(io_driver)?;
                let process_driver = create_process_driver(signal_driver)?;

                (Either::A(process_driver), Some(io_handle), signal_handle)
            } else {
                (Either::B(ParkThread::new()), Default::default(), Default::default())
            };

            Ok(ret)
        }
    }

    cfg_not_io_driver! {
        pub(crate) type IoHandle = ();
        type IoStack = ParkThread;

        fn create_io_stack(_enabled: bool) -> io::Result<(IoStack, IoHandle, SignalHandle)> {
            Ok((ParkThread::new(), Default::default(), Default::default()))
        }
    }

    // ===== signal driver =====

    macro_rules! cfg_signal_internal_and_unix {
        ($($item:item)*) => {
            #[cfg(unix)]
            cfg_signal_internal! { $($item)* }
        }
    }

    cfg_signal_internal_and_unix! {
        type SignalDriver = crate::signal::unix::driver::Driver;
        pub(crate) type SignalHandle = Option<crate::signal::unix::driver::Handle>;

        fn create_signal_driver(io_driver: IoDriver) -> io::Result<(SignalDriver, SignalHandle)> {
            let driver = crate::signal::unix::driver::Driver::new(io_driver)?;
            let handle = driver.handle();
            Ok((driver, Some(handle)))
        }
    }

    cfg_not_signal_internal! {
        pub(crate) type SignalHandle = ();

        cfg_io_driver! {
            type SignalDriver = IoDriver;

            fn create_signal_driver(io_driver: IoDriver) -> io::Result<(SignalDriver, SignalHandle)> {
                Ok((io_driver, ()))
            }
        }
    }

    // ===== process driver =====

    cfg_process_driver! {
        type ProcessDriver = crate::process::unix::driver::Driver;

        fn create_process_driver(signal_driver: SignalDriver) -> io::Result<ProcessDriver> {
            crate::process::unix::driver::Driver::new(signal_driver)
        }
    }

    cfg_not_process_driver! {
        cfg_io_driver! {
            type ProcessDriver = SignalDriver;

            fn create_process_driver(signal_driver: SignalDriver) -> io::Result<ProcessDriver> {
                Ok(signal_driver)
            }
        }
    }

    // ===== time driver =====

    cfg_time! {
        type TimeDriver = crate::park::either::Either<crate::time::driver::Driver<IoStack>, IoStack>;

        pub(crate) type Clock = crate::time::Clock;
        pub(crate) type TimeHandle = Option<crate::time::driver::Handle>;

        fn create_clock(enable_pausing: bool, start_paused: bool) -> Clock {
            crate::time::Clock::new(enable_pausing, start_paused)
        }

        fn create_time_driver(
            enable: bool,
            io_stack: IoStack,
            clock: Clock,
        ) -> (TimeDriver, TimeHandle) {
            use crate::park::either::Either;

            if enable {
                let driver = crate::time::driver::Driver::new(io_stack, clock);
                let handle = driver.handle();

                (Either::A(driver), Some(handle))
            } else {
                (Either::B(io_stack), None)
            }
        }
    }

    cfg_not_time! {
        type TimeDriver = IoStack;

        pub(crate) type Clock = ();
        pub(crate) type TimeHandle = ();

        fn create_clock(_enable_pausing: bool, _start_paused: bool) -> Clock {
            ()
        }

        fn create_time_driver(
            _enable: bool,
            io_stack: IoStack,
            _clock: Clock,
        ) -> (TimeDriver, TimeHandle) {
            (io_stack, ())
        }
    }

    // ===== runtime driver =====

    #[derive(Debug)]
    pub(crate) struct Driver {
        inner: TimeDriver,
    }

    pub(crate) struct Resources {
        pub(crate) io_handle: IoHandle,
        pub(crate) signal_handle: SignalHandle,
        pub(crate) time_handle: TimeHandle,
        pub(crate) clock: Clock,
    }

    pub(crate) struct Cfg {
        pub(crate) enable_io: bool,
        pub(crate) enable_time: bool,
        pub(crate) enable_pause_time: bool,
        pub(crate) start_paused: bool,
    }

    impl Driver {
        pub(crate) fn new(cfg: Cfg) -> io::Result<(Self, Resources)> {
            let (io_stack, io_handle, signal_handle) = create_io_stack(cfg.enable_io)?;

            let clock = create_clock(cfg.enable_pause_time, cfg.start_paused);

            let (time_driver, time_handle) =
                create_time_driver(cfg.enable_time, io_stack, clock.clone());

            Ok((
                Self { inner: time_driver },
                Resources {
                    io_handle,
                    signal_handle,
                    time_handle,
                    clock,
                },
            ))
        }
    }

    impl Park for Driver {
        type Unpark = <TimeDriver as Park>::Unpark;
        type Error = <TimeDriver as Park>::Error;

        fn unpark(&self) -> Self::Unpark {
            self.inner.unpark()
        }

        fn park(&mut self) -> Result<(), Self::Error> {
            self.inner.park()
        }

        fn park_timeout(&mut self, duration: Duration) -> Result<(), Self::Error> {
            self.inner.park_timeout(duration)
        }

        fn shutdown(&mut self) {
            self.inner.shutdown()
        }
    }