use crate::task::JoinHandle;

cfg_rt_multi_thread! {

    /// Runs the provided blocking function on the current thread without

    /// blocking the executor.

    ///

    /// In general, issuing a blocking call or performing a lot of compute in a

    /// future without yielding is problematic, as it may prevent the executor

    /// from driving other tasks forward. Calling this function informs the

    /// executor that the currently executing task is about to block the thread,

    /// so the executor is able to hand off any other tasks it has to a new

    /// worker thread before that happens. See the [CPU-bound tasks and blocking

    /// code][blocking] section for more information.

    ///

    /// Be aware that although this function avoids starving other independently

    /// spawned tasks, any other code running concurrently in the same task will

    /// be suspended during the call to `block_in_place`. This can happen e.g.

    /// when using the [`join!`] macro. To avoid this issue, use

    /// [`spawn_blocking`] instead of `block_in_place`.

    ///

    /// Note that this function cannot be used within a [`current_thread`] runtime

    /// because in this case there are no other worker threads to hand off tasks

    /// to. On the other hand, calling the function outside a runtime is

    /// allowed. In this case, `block_in_place` just calls the provided closure

    /// normally.

    ///

    /// Code running behind `block_in_place` cannot be cancelled. When you shut

    /// down the executor, it will wait indefinitely for all blocking operations

    /// to finish. You can use [`shutdown_timeout`] to stop waiting for them

    /// after a certain timeout. Be aware that this will still not cancel the

    /// tasks — they are simply allowed to keep running after the method

    /// returns.

    ///

    /// [blocking]: ../index.html#cpu-bound-tasks-and-blocking-code

    /// [`spawn_blocking`]: fn@crate::task::spawn_blocking

    /// [`join!`]: macro@join

    /// [`thread::spawn`]: fn@std::thread::spawn

    /// [`shutdown_timeout`]: fn@crate::runtime::Runtime::shutdown_timeout

    ///

    /// # Examples

    ///

    /// ```

    /// use tokio::task;

    ///

    /// # async fn docs() {

    /// task::block_in_place(move || {

    ///     // do some compute-heavy work or call synchronous code

    /// });

    /// # }

    /// ```

    ///

    /// Code running inside `block_in_place` may use `block_on` to reenter the

    /// async context.

    ///

    /// ```

    /// use tokio::task;

    /// use tokio::runtime::Handle;

    ///

    /// # async fn docs() {

    /// task::block_in_place(move || {

    ///     Handle::current().block_on(async move {

    ///         // do something async

    ///     });

    /// });

    /// # }

    /// ```

    ///

    /// # Panics

    ///

    /// This function panics if called from a [`current_thread`] runtime.

    ///

    /// [`current_thread`]: fn@crate::runtime::Builder::new_current_thread

    #[track_caller]

    pub fn block_in_place<F, R>(f: F) -> R

    where

        F: FnOnce() -> R,

    {

        crate::runtime::scheduler::block_in_place(f)

    }

}

cfg_rt! {

    /// Runs the provided closure on a thread where blocking is acceptable.

    ///

    /// In general, issuing a blocking call or performing a lot of compute in a

    /// future without yielding is problematic, as it may prevent the executor from

    /// driving other futures forward. This function runs the provided closure on a

    /// thread dedicated to blocking operations. See the [CPU-bound tasks and

    /// blocking code][blocking] section for more information.

    ///

    /// Tokio will spawn more blocking threads when they are requested through this

    /// function until the upper limit configured on the [`Builder`] is reached.

    /// After reaching the upper limit, the tasks are put in a queue.

    /// The thread limit is very large by default, because `spawn_blocking` is often

    /// used for various kinds of IO operations that cannot be performed

    /// asynchronously.  When you run CPU-bound code using `spawn_blocking`, you

    /// should keep this large upper limit in mind. When running many CPU-bound

    /// computations, a semaphore or some other synchronization primitive should be

    /// used to limit the number of computation executed in parallel. Specialized

    /// CPU-bound executors, such as [rayon], may also be a good fit.

    ///

    /// This function is intended for non-async operations that eventually finish on

    /// their own. If you want to spawn an ordinary thread, you should use

    /// [`thread::spawn`] instead.

    ///

    /// Be aware that tasks spawned using `spawn_blocking` cannot be aborted

    /// because they are not async. If you call [`abort`] on a `spawn_blocking`

    /// task, then this *will not have any effect*, and the task will continue

    /// running normally. The exception is if the task has not started running

    /// yet; in that case, calling `abort` may prevent the task from starting.

    ///

    /// When you shut down the executor, it will wait indefinitely for all blocking operations to

    /// finish. You can use [`shutdown_timeout`] to stop waiting for them after a

    /// certain timeout. Be aware that this will still not cancel the tasks — they

    /// are simply allowed to keep running after the method returns.  It is possible

    /// for a blocking task to be cancelled if it has not yet started running, but this

    /// is not guaranteed.

    ///

    /// Note that if you are using the single threaded runtime, this function will

    /// still spawn additional threads for blocking operations. The current-thread

    /// scheduler's single thread is only used for asynchronous code.

    ///

    /// # Related APIs and patterns for bridging asynchronous and blocking code

    ///

    /// In simple cases, it is sufficient to have the closure accept input

    /// parameters at creation time and return a single value (or struct/tuple, etc.).

    ///

    /// For more complex situations in which it is desirable to stream data to or from

    /// the synchronous context, the [`mpsc channel`] has `blocking_send` and

    /// `blocking_recv` methods for use in non-async code such as the thread created

    /// by `spawn_blocking`.

    ///

    /// Another option is [`SyncIoBridge`] for cases where the synchronous context

    /// is operating on byte streams.  For example, you might use an asynchronous

    /// HTTP client such as [hyper] to fetch data, but perform complex parsing

    /// of the payload body using a library written for synchronous I/O.

    ///

    /// Finally, see also [Bridging with sync code][bridgesync] for discussions

    /// around the opposite case of using Tokio as part of a larger synchronous

    /// codebase.

    ///

    /// [`Builder`]: struct@crate::runtime::Builder

    /// [blocking]: ../index.html#cpu-bound-tasks-and-blocking-code

    /// [rayon]: https://docs.rs/rayon

    /// [`mpsc channel`]: crate::sync::mpsc

    /// [`SyncIoBridge`]: https://docs.rs/tokio-util/latest/tokio_util/io/struct.SyncIoBridge.html

    /// [hyper]: https://docs.rs/hyper

    /// [`thread::spawn`]: fn@std::thread::spawn

    /// [`shutdown_timeout`]: fn@crate::runtime::Runtime::shutdown_timeout

    /// [bridgesync]: https://tokio.rs/tokio/topics/bridging

    /// [`AtomicBool`]: struct@std::sync::atomic::AtomicBool

    /// [`abort`]: crate::task::JoinHandle::abort

    ///

    /// # Examples

    ///

    /// Pass an input value and receive result of computation:

    ///

    /// ```

    /// use tokio::task;

    ///

    /// # async fn docs() -> Result<(), Box<dyn std::error::Error>>{

    /// // Initial input

    /// let mut v = "Hello, ".to_string();

    /// let res = task::spawn_blocking(move || {

    ///     // Stand-in for compute-heavy work or using synchronous APIs

    ///     v.push_str("world");

    ///     // Pass ownership of the value back to the asynchronous context

    ///     v

    /// }).await?;

    ///

    /// // `res` is the value returned from the thread

    /// assert_eq!(res.as_str(), "Hello, world");

    /// # Ok(())

    /// # }

    /// ```

    ///

    /// Use a channel:

    ///

    /// ```

    /// use tokio::task;

    /// use tokio::sync::mpsc;

    ///

    /// # async fn docs() {

    /// let (tx, mut rx) = mpsc::channel(2);

    /// let start = 5;

    /// let worker = task::spawn_blocking(move || {

    ///     for x in 0..10 {

    ///         // Stand in for complex computation

    ///         tx.blocking_send(start + x).unwrap();

    ///     }

    /// });

    ///

    /// let mut acc = 0;

    /// while let Some(v) = rx.recv().await {

    ///     acc += v;

    /// }

    /// assert_eq!(acc, 95);

    /// worker.await.unwrap();

    /// # }

    /// ```

    #[track_caller]

    pub fn spawn_blocking<F, R>(f: F) -> JoinHandle<R>

    where

        F: FnOnce() -> R + Send + 'static,

        R: Send + 'static,

    {

        crate::runtime::spawn_blocking(f)

    }

Unexecuted instantiation: tokio::task::blocking::spawn_blocking::<<hyper_util::client::legacy::connect::dns::GaiResolver as tower_service::Service<hyper_util::client::legacy::connect::dns::Name>>::call::{closure#0}, core::result::Result<hyper_util::client::legacy::connect::dns::SocketAddrs, std::io::error::Error>>

Unexecuted instantiation: tokio::task::blocking::spawn_blocking::<_, _>

}