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#![allow(unreachable_pub)]
use crate::{
runtime::{Handle, BOX_FUTURE_THRESHOLD},
task::{JoinHandle, LocalSet},
};
use std::{future::Future, io};
/// Factory which is used to configure the properties of a new task.
///
/// **Note**: This is an [unstable API][unstable]. The public API of this type
/// may break in 1.x releases. See [the documentation on unstable
/// features][unstable] for details.
///
/// Methods can be chained in order to configure it.
///
/// Currently, there is only one configuration option:
///
/// - [`name`], which specifies an associated name for
/// the task
///
/// There are three types of task that can be spawned from a Builder:
/// - [`spawn_local`] for executing futures on the current thread
/// - [`spawn`] for executing [`Send`] futures on the runtime
/// - [`spawn_blocking`] for executing blocking code in the
/// blocking thread pool.
///
/// ## Example
///
/// ```no_run
/// use tokio::net::{TcpListener, TcpStream};
///
/// use std::io;
///
/// async fn process(socket: TcpStream) {
/// // ...
/// # drop(socket);
/// }
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let listener = TcpListener::bind("127.0.0.1:8080").await?;
///
/// loop {
/// let (socket, _) = listener.accept().await?;
///
/// tokio::task::Builder::new()
/// .name("tcp connection handler")
/// .spawn(async move {
/// // Process each socket concurrently.
/// process(socket).await
/// })?;
/// }
/// }
/// ```
/// [unstable]: crate#unstable-features
/// [`name`]: Builder::name
/// [`spawn_local`]: Builder::spawn_local
/// [`spawn`]: Builder::spawn
/// [`spawn_blocking`]: Builder::spawn_blocking
#[derive(Default, Debug)]
#[cfg_attr(docsrs, doc(cfg(all(tokio_unstable, feature = "tracing"))))]
pub struct Builder<'a> {
name: Option<&'a str>,
}
impl<'a> Builder<'a> {
/// Creates a new task builder.
pub fn new() -> Self {
Self::default()
}
/// Assigns a name to the task which will be spawned.
pub fn name(&self, name: &'a str) -> Self {
Self { name: Some(name) }
}
/// Spawns a task with this builder's settings on the current runtime.
///
/// # Panics
///
/// This method panics if called outside of a Tokio runtime.
///
/// See [`task::spawn`](crate::task::spawn()) for
/// more details.
#[track_caller]
pub fn spawn<Fut>(self, future: Fut) -> io::Result<JoinHandle<Fut::Output>>
where
Fut: Future + Send + 'static,
Fut::Output: Send + 'static,
{
Ok(
if cfg!(debug_assertions) && std::mem::size_of::<Fut>() > BOX_FUTURE_THRESHOLD {
super::spawn::spawn_inner(Box::pin(future), self.name)
} else {
super::spawn::spawn_inner(future, self.name)
},
)
}
/// Spawn a task with this builder's settings on the provided [runtime
/// handle].
///
/// See [`Handle::spawn`] for more details.
///
/// [runtime handle]: crate::runtime::Handle
/// [`Handle::spawn`]: crate::runtime::Handle::spawn
#[track_caller]
pub fn spawn_on<Fut>(self, future: Fut, handle: &Handle) -> io::Result<JoinHandle<Fut::Output>>
where
Fut: Future + Send + 'static,
Fut::Output: Send + 'static,
{
Ok(
if cfg!(debug_assertions) && std::mem::size_of::<Fut>() > BOX_FUTURE_THRESHOLD {
handle.spawn_named(Box::pin(future), self.name)
} else {
handle.spawn_named(future, self.name)
},
)
}
/// Spawns `!Send` a task on the current [`LocalSet`] with this builder's
/// settings.
///
/// The spawned future will be run on the same thread that called `spawn_local`.
/// This may only be called from the context of a [local task set][`LocalSet`].
///
/// # Panics
///
/// This function panics if called outside of a [local task set][`LocalSet`].
///
/// See [`task::spawn_local`] for more details.
///
/// [`task::spawn_local`]: crate::task::spawn_local
/// [`LocalSet`]: crate::task::LocalSet
#[track_caller]
pub fn spawn_local<Fut>(self, future: Fut) -> io::Result<JoinHandle<Fut::Output>>
where
Fut: Future + 'static,
Fut::Output: 'static,
{
Ok(
if cfg!(debug_assertions) && std::mem::size_of::<Fut>() > BOX_FUTURE_THRESHOLD {
super::local::spawn_local_inner(Box::pin(future), self.name)
} else {
super::local::spawn_local_inner(future, self.name)
},
)
}
/// Spawns `!Send` a task on the provided [`LocalSet`] with this builder's
/// settings.
///
/// See [`LocalSet::spawn_local`] for more details.
///
/// [`LocalSet::spawn_local`]: crate::task::LocalSet::spawn_local
/// [`LocalSet`]: crate::task::LocalSet
#[track_caller]
pub fn spawn_local_on<Fut>(
self,
future: Fut,
local_set: &LocalSet,
) -> io::Result<JoinHandle<Fut::Output>>
where
Fut: Future + 'static,
Fut::Output: 'static,
{
Ok(local_set.spawn_named(future, self.name))
}
/// Spawns blocking code on the blocking threadpool.
///
/// # Panics
///
/// This method panics if called outside of a Tokio runtime.
///
/// See [`task::spawn_blocking`](crate::task::spawn_blocking)
/// for more details.
#[track_caller]
pub fn spawn_blocking<Function, Output>(
self,
function: Function,
) -> io::Result<JoinHandle<Output>>
where
Function: FnOnce() -> Output + Send + 'static,
Output: Send + 'static,
{
let handle = Handle::current();
self.spawn_blocking_on(function, &handle)
}
/// Spawns blocking code on the provided [runtime handle]'s blocking threadpool.
///
/// See [`Handle::spawn_blocking`] for more details.
///
/// [runtime handle]: crate::runtime::Handle
/// [`Handle::spawn_blocking`]: crate::runtime::Handle::spawn_blocking
#[track_caller]
pub fn spawn_blocking_on<Function, Output>(
self,
function: Function,
handle: &Handle,
) -> io::Result<JoinHandle<Output>>
where
Function: FnOnce() -> Output + Send + 'static,
Output: Send + 'static,
{
use crate::runtime::Mandatory;
let (join_handle, spawn_result) =
if cfg!(debug_assertions) && std::mem::size_of::<Function>() > BOX_FUTURE_THRESHOLD {
handle.inner.blocking_spawner().spawn_blocking_inner(
Box::new(function),
Mandatory::NonMandatory,
self.name,
handle,
)
} else {
handle.inner.blocking_spawner().spawn_blocking_inner(
function,
Mandatory::NonMandatory,
self.name,
handle,
)
};
spawn_result?;
Ok(join_handle)
}
}