117 lines
3 KiB
Rust
117 lines
3 KiB
Rust
use core::convert;
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use core::fmt;
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use core::ops::{ControlFlow, FromResidual, Try};
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use core::task::Poll;
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/// Extracts the successful type of a [`Poll<T>`].
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///
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/// This macro bakes in propagation of [`Pending`] signals by returning early.
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///
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/// [`Poll<T>`]: crate::task::Poll
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/// [`Pending`]: crate::task::Poll::Pending
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///
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/// # Examples
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///
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/// ```
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/// #![feature(ready_macro)]
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///
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/// use std::task::{ready, Context, Poll};
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/// use std::future::{self, Future};
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/// use std::pin::Pin;
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///
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/// pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
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/// let mut fut = future::ready(42);
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/// let fut = Pin::new(&mut fut);
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///
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/// let num = ready!(fut.poll(cx));
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/// # drop(num);
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/// // ... use num
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///
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/// Poll::Ready(())
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/// }
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/// ```
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///
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/// The `ready!` call expands to:
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///
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/// ```
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/// # #![feature(ready_macro)]
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/// # use std::task::{Context, Poll};
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/// # use std::future::{self, Future};
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/// # use std::pin::Pin;
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/// #
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/// # pub fn do_poll(cx: &mut Context<'_>) -> Poll<()> {
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/// # let mut fut = future::ready(42);
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/// # let fut = Pin::new(&mut fut);
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/// #
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/// let num = match fut.poll(cx) {
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/// Poll::Ready(t) => t,
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/// Poll::Pending => return Poll::Pending,
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/// };
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/// # drop(num);
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/// # // ... use num
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/// #
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/// # Poll::Ready(())
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/// # }
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/// ```
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#[unstable(feature = "ready_macro", issue = "70922")]
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#[rustc_macro_transparency = "semitransparent"]
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pub macro ready($e:expr) {
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match $e {
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$crate::task::Poll::Ready(t) => t,
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$crate::task::Poll::Pending => {
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return $crate::task::Poll::Pending;
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}
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}
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}
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/// Extracts the successful type of a [`Poll<T>`].
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///
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/// See [`Poll::ready`] for details.
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#[unstable(feature = "poll_ready", issue = "89780")]
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pub struct Ready<T>(pub(crate) Poll<T>);
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#[unstable(feature = "poll_ready", issue = "89780")]
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impl<T> Try for Ready<T> {
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type Output = T;
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type Residual = Ready<convert::Infallible>;
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#[inline]
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fn from_output(output: Self::Output) -> Self {
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Ready(Poll::Ready(output))
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}
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#[inline]
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fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
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match self.0 {
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Poll::Ready(v) => ControlFlow::Continue(v),
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Poll::Pending => ControlFlow::Break(Ready(Poll::Pending)),
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}
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}
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}
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#[unstable(feature = "poll_ready", issue = "89780")]
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impl<T> FromResidual for Ready<T> {
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#[inline]
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fn from_residual(residual: Ready<convert::Infallible>) -> Self {
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match residual.0 {
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Poll::Pending => Ready(Poll::Pending),
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}
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}
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}
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#[unstable(feature = "poll_ready", issue = "89780")]
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impl<T> FromResidual<Ready<convert::Infallible>> for Poll<T> {
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#[inline]
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fn from_residual(residual: Ready<convert::Infallible>) -> Self {
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match residual.0 {
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Poll::Pending => Poll::Pending,
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}
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}
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}
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#[unstable(feature = "poll_ready", issue = "89780")]
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impl<T> fmt::Debug for Ready<T> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_tuple("Ready").finish()
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}
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}
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