forked from mirror/async-std
Reduce dependency on futures crate (#140)
* Add future::poll_fn * Replace all uses of poll_fn with the new one * Remove some uses of futures * Simplify ReadDir and DirEntry * Remove some use of futures from File * Use futures subcrates * Fix imports in docs * Remove futures-util dependency * Remove futures-executor-preview * Refactor * Require more features in the futures-preview cratestaging
Stjepan Glavina
5 years ago
committed by
GitHub
parent
75a4ba80cc
commit
bac74c2d7f
@ -0,0 +1,49 @@
|
|||||||
|
use std::pin::Pin;
|
||||||
|
|
||||||
|
use crate::future::Future;
|
||||||
|
use crate::task::{Context, Poll};
|
||||||
|
|
||||||
|
/// Creates a new future wrapping around a function returning [`Poll`].
|
||||||
|
///
|
||||||
|
/// Polling the returned future delegates to the wrapped function.
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```
|
||||||
|
/// # fn main() { async_std::task::block_on(async {
|
||||||
|
/// #
|
||||||
|
/// use async_std::future;
|
||||||
|
/// use async_std::task::{Context, Poll};
|
||||||
|
///
|
||||||
|
/// fn poll_greeting(_: &mut Context<'_>) -> Poll<String> {
|
||||||
|
/// Poll::Ready("hello world".to_string())
|
||||||
|
/// }
|
||||||
|
///
|
||||||
|
/// assert_eq!(future::poll_fn(poll_greeting).await, "hello world");
|
||||||
|
/// #
|
||||||
|
/// # }) }
|
||||||
|
/// ```
|
||||||
|
pub async fn poll_fn<F, T>(f: F) -> T
|
||||||
|
where
|
||||||
|
F: FnMut(&mut Context<'_>) -> Poll<T>,
|
||||||
|
{
|
||||||
|
let fut = PollFn { f };
|
||||||
|
fut.await
|
||||||
|
}
|
||||||
|
|
||||||
|
struct PollFn<F> {
|
||||||
|
f: F,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl<F> Unpin for PollFn<F> {}
|
||||||
|
|
||||||
|
impl<T, F> Future for PollFn<F>
|
||||||
|
where
|
||||||
|
F: FnMut(&mut Context<'_>) -> Poll<T>,
|
||||||
|
{
|
||||||
|
type Output = T;
|
||||||
|
|
||||||
|
fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
|
||||||
|
(&mut self.f)(cx)
|
||||||
|
}
|
||||||
|
}
|
||||||
@ -0,0 +1,135 @@
|
|||||||
|
use std::cell::UnsafeCell;
|
||||||
|
use std::mem::{self, ManuallyDrop};
|
||||||
|
use std::panic::{self, AssertUnwindSafe, UnwindSafe};
|
||||||
|
use std::pin::Pin;
|
||||||
|
use std::sync::Arc;
|
||||||
|
use std::task::{RawWaker, RawWakerVTable};
|
||||||
|
use std::thread::{self, Thread};
|
||||||
|
|
||||||
|
use super::pool;
|
||||||
|
use super::Builder;
|
||||||
|
use crate::future::Future;
|
||||||
|
use crate::task::{Context, Poll, Waker};
|
||||||
|
|
||||||
|
/// Spawns a task and blocks the current thread on its result.
|
||||||
|
///
|
||||||
|
/// Calling this function is similar to [spawning] a thread and immediately [joining] it, except an
|
||||||
|
/// asynchronous task will be spawned.
|
||||||
|
///
|
||||||
|
/// [spawning]: https://doc.rust-lang.org/std/thread/fn.spawn.html
|
||||||
|
/// [joining]: https://doc.rust-lang.org/std/thread/struct.JoinHandle.html#method.join
|
||||||
|
///
|
||||||
|
/// # Examples
|
||||||
|
///
|
||||||
|
/// ```no_run
|
||||||
|
/// use async_std::task;
|
||||||
|
///
|
||||||
|
/// fn main() {
|
||||||
|
/// task::block_on(async {
|
||||||
|
/// println!("Hello, world!");
|
||||||
|
/// })
|
||||||
|
/// }
|
||||||
|
/// ```
|
||||||
|
pub fn block_on<F, T>(future: F) -> T
|
||||||
|
where
|
||||||
|
F: Future<Output = T> + Send,
|
||||||
|
T: Send,
|
||||||
|
{
|
||||||
|
unsafe {
|
||||||
|
// A place on the stack where the result will be stored.
|
||||||
|
let out = &mut UnsafeCell::new(None);
|
||||||
|
|
||||||
|
// Wrap the future into one that stores the result into `out`.
|
||||||
|
let future = {
|
||||||
|
let out = out.get();
|
||||||
|
|
||||||
|
async move {
|
||||||
|
let future = CatchUnwindFuture {
|
||||||
|
future: AssertUnwindSafe(future),
|
||||||
|
};
|
||||||
|
*out = Some(future.await);
|
||||||
|
}
|
||||||
|
};
|
||||||
|
|
||||||
|
// Pin the future onto the stack.
|
||||||
|
pin_utils::pin_mut!(future);
|
||||||
|
|
||||||
|
// Transmute the future into one that is static and sendable.
|
||||||
|
let future = mem::transmute::<
|
||||||
|
Pin<&mut dyn Future<Output = ()>>,
|
||||||
|
Pin<&'static mut (dyn Future<Output = ()> + Send)>,
|
||||||
|
>(future);
|
||||||
|
|
||||||
|
// Spawn the future and wait for it to complete.
|
||||||
|
block(pool::spawn_with_builder(Builder::new(), future, "block_on"));
|
||||||
|
|
||||||
|
// Take out the result.
|
||||||
|
match (*out.get()).take().unwrap() {
|
||||||
|
Ok(v) => v,
|
||||||
|
Err(err) => panic::resume_unwind(err),
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
struct CatchUnwindFuture<F> {
|
||||||
|
future: F,
|
||||||
|
}
|
||||||
|
|
||||||
|
impl<F> CatchUnwindFuture<F> {
|
||||||
|
pin_utils::unsafe_pinned!(future: F);
|
||||||
|
}
|
||||||
|
|
||||||
|
impl<F: Future + UnwindSafe> Future for CatchUnwindFuture<F> {
|
||||||
|
type Output = thread::Result<F::Output>;
|
||||||
|
|
||||||
|
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
|
||||||
|
panic::catch_unwind(AssertUnwindSafe(|| self.future().poll(cx)))?.map(Ok)
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
fn block<F: Future>(f: F) -> F::Output {
|
||||||
|
thread_local! {
|
||||||
|
static ARC_THREAD: Arc<Thread> = Arc::new(thread::current());
|
||||||
|
}
|
||||||
|
|
||||||
|
pin_utils::pin_mut!(f);
|
||||||
|
|
||||||
|
ARC_THREAD.with(|arc_thread: &Arc<Thread>| {
|
||||||
|
let ptr = (&**arc_thread as *const Thread) as *const ();
|
||||||
|
let vt = vtable();
|
||||||
|
|
||||||
|
let waker = unsafe { ManuallyDrop::new(Waker::from_raw(RawWaker::new(ptr, vt))) };
|
||||||
|
let cx = &mut Context::from_waker(&waker);
|
||||||
|
|
||||||
|
loop {
|
||||||
|
if let Poll::Ready(t) = f.as_mut().poll(cx) {
|
||||||
|
return t;
|
||||||
|
}
|
||||||
|
thread::park();
|
||||||
|
}
|
||||||
|
})
|
||||||
|
}
|
||||||
|
|
||||||
|
fn vtable() -> &'static RawWakerVTable {
|
||||||
|
unsafe fn clone_raw(ptr: *const ()) -> RawWaker {
|
||||||
|
let arc = ManuallyDrop::new(Arc::from_raw(ptr as *const Thread));
|
||||||
|
mem::forget(arc.clone());
|
||||||
|
RawWaker::new(ptr, vtable())
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe fn wake_raw(ptr: *const ()) {
|
||||||
|
let arc = Arc::from_raw(ptr as *const Thread);
|
||||||
|
arc.unpark();
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe fn wake_by_ref_raw(ptr: *const ()) {
|
||||||
|
let arc = ManuallyDrop::new(Arc::from_raw(ptr as *const Thread));
|
||||||
|
arc.unpark();
|
||||||
|
}
|
||||||
|
|
||||||
|
unsafe fn drop_raw(ptr: *const ()) {
|
||||||
|
drop(Arc::from_raw(ptr as *const Thread))
|
||||||
|
}
|
||||||
|
|
||||||
|
&RawWakerVTable::new(clone_raw, wake_raw, wake_by_ref_raw, drop_raw)
|
||||||
|
}
|
||||||
Loading…
Reference in New Issue