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use futures_task::{LocalSpawn, Spawn};
#[cfg(feature = "compat")]
use crate::compat::Compat;
#[cfg(feature = "channel")]
#[cfg(feature = "std")]
use crate::future::{FutureExt, RemoteHandle};
#[cfg(feature = "alloc")]
use alloc::boxed::Box;
#[cfg(feature = "alloc")]
use futures_core::future::Future;
#[cfg(feature = "alloc")]
use futures_task::{FutureObj, LocalFutureObj, SpawnError};
impl<Sp: ?Sized> SpawnExt for Sp where Sp: Spawn {}
impl<Sp: ?Sized> LocalSpawnExt for Sp where Sp: LocalSpawn {}
/// Extension trait for `Spawn`.
pub trait SpawnExt: Spawn {
/// Spawns a task that polls the given future with output `()` to
/// completion.
///
/// This method returns a [`Result`] that contains a [`SpawnError`] if
/// spawning fails.
///
/// You can use [`spawn_with_handle`](SpawnExt::spawn_with_handle) if
/// you want to spawn a future with output other than `()` or if you want
/// to be able to await its completion.
///
/// Note this method will eventually be replaced with the upcoming
/// `Spawn::spawn` method which will take a `dyn Future` as input.
/// Technical limitations prevent `Spawn::spawn` from being implemented
/// today. Feel free to use this method in the meantime.
///
/// ```
/// # {
/// use futures::executor::ThreadPool;
/// use futures::task::SpawnExt;
///
/// let executor = ThreadPool::new().unwrap();
///
/// let future = async { /* ... */ };
/// executor.spawn(future).unwrap();
/// # }
/// # std::thread::sleep(std::time::Duration::from_millis(500)); // wait for background threads closed: https://github.com/rust-lang/miri/issues/1371
/// ```
#[cfg(feature = "alloc")]
fn spawn<Fut>(&self, future: Fut) -> Result<(), SpawnError>
where
Fut: Future<Output = ()> + Send + 'static,
{
self.spawn_obj(FutureObj::new(Box::new(future)))
}
/// Spawns a task that polls the given future to completion and returns a
/// future that resolves to the spawned future's output.
///
/// This method returns a [`Result`] that contains a [`RemoteHandle`](crate::future::RemoteHandle), or, if
/// spawning fails, a [`SpawnError`]. [`RemoteHandle`](crate::future::RemoteHandle) is a future that
/// resolves to the output of the spawned future.
///
/// ```
/// # {
/// use futures::executor::{block_on, ThreadPool};
/// use futures::future;
/// use futures::task::SpawnExt;
///
/// let executor = ThreadPool::new().unwrap();
///
/// let future = future::ready(1);
/// let join_handle_fut = executor.spawn_with_handle(future).unwrap();
/// assert_eq!(block_on(join_handle_fut), 1);
/// # }
/// # std::thread::sleep(std::time::Duration::from_millis(500)); // wait for background threads closed: https://github.com/rust-lang/miri/issues/1371
/// ```
#[cfg(feature = "channel")]
#[cfg_attr(docsrs, doc(cfg(feature = "channel")))]
#[cfg(feature = "std")]
fn spawn_with_handle<Fut>(&self, future: Fut) -> Result<RemoteHandle<Fut::Output>, SpawnError>
where
Fut: Future + Send + 'static,
Fut::Output: Send,
{
let (future, handle) = future.remote_handle();
self.spawn(future)?;
Ok(handle)
}
/// Wraps a [`Spawn`] and makes it usable as a futures 0.1 `Executor`.
/// Requires the `compat` feature to enable.
#[cfg(feature = "compat")]
#[cfg_attr(docsrs, doc(cfg(feature = "compat")))]
fn compat(self) -> Compat<Self>
where
Self: Sized,
{
Compat::new(self)
}
}
/// Extension trait for `LocalSpawn`.
pub trait LocalSpawnExt: LocalSpawn {
/// Spawns a task that polls the given future with output `()` to
/// completion.
///
/// This method returns a [`Result`] that contains a [`SpawnError`] if
/// spawning fails.
///
/// You can use [`spawn_with_handle`](SpawnExt::spawn_with_handle) if
/// you want to spawn a future with output other than `()` or if you want
/// to be able to await its completion.
///
/// Note this method will eventually be replaced with the upcoming
/// `Spawn::spawn` method which will take a `dyn Future` as input.
/// Technical limitations prevent `Spawn::spawn` from being implemented
/// today. Feel free to use this method in the meantime.
///
/// ```
/// use futures::executor::LocalPool;
/// use futures::task::LocalSpawnExt;
///
/// let executor = LocalPool::new();
/// let spawner = executor.spawner();
///
/// let future = async { /* ... */ };
/// spawner.spawn_local(future).unwrap();
/// ```
#[cfg(feature = "alloc")]
fn spawn_local<Fut>(&self, future: Fut) -> Result<(), SpawnError>
where
Fut: Future<Output = ()> + 'static,
{
self.spawn_local_obj(LocalFutureObj::new(Box::new(future)))
}
/// Spawns a task that polls the given future to completion and returns a
/// future that resolves to the spawned future's output.
///
/// This method returns a [`Result`] that contains a [`RemoteHandle`](crate::future::RemoteHandle), or, if
/// spawning fails, a [`SpawnError`]. [`RemoteHandle`](crate::future::RemoteHandle) is a future that
/// resolves to the output of the spawned future.
///
/// ```
/// use futures::executor::LocalPool;
/// use futures::task::LocalSpawnExt;
///
/// let mut executor = LocalPool::new();
/// let spawner = executor.spawner();
///
/// let future = async { 1 };
/// let join_handle_fut = spawner.spawn_local_with_handle(future).unwrap();
/// assert_eq!(executor.run_until(join_handle_fut), 1);
/// ```
#[cfg(feature = "channel")]
#[cfg_attr(docsrs, doc(cfg(feature = "channel")))]
#[cfg(feature = "std")]
fn spawn_local_with_handle<Fut>(
&self,
future: Fut,
) -> Result<RemoteHandle<Fut::Output>, SpawnError>
where
Fut: Future + 'static,
{
let (future, handle) = future.remote_handle();
self.spawn_local(future)?;
Ok(handle)
}
}