/
poll.rs
245 lines (218 loc) · 7.3 KB
/
poll.rs
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#![stable(feature = "futures_api", since = "1.36.0")]
use crate::convert;
use crate::ops::{self, ControlFlow};
use crate::result::Result;
/// Indicates whether a value is available or if the current task has been
/// scheduled to receive a wakeup instead.
#[must_use = "this `Poll` may be a `Pending` variant, which should be handled"]
#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
#[stable(feature = "futures_api", since = "1.36.0")]
pub enum Poll<T> {
/// Represents that a value is immediately ready.
#[lang = "Ready"]
#[stable(feature = "futures_api", since = "1.36.0")]
Ready(#[stable(feature = "futures_api", since = "1.36.0")] T),
/// Represents that a value is not ready yet.
///
/// When a function returns `Pending`, the function *must* also
/// ensure that the current task is scheduled to be awoken when
/// progress can be made.
#[lang = "Pending"]
#[stable(feature = "futures_api", since = "1.36.0")]
Pending,
}
impl<T> Poll<T> {
/// Changes the ready value of this `Poll` with the closure provided.
#[stable(feature = "futures_api", since = "1.36.0")]
pub fn map<U, F>(self, f: F) -> Poll<U>
where
F: FnOnce(T) -> U,
{
match self {
Poll::Ready(t) => Poll::Ready(f(t)),
Poll::Pending => Poll::Pending,
}
}
/// Returns `true` if this is `Poll::Ready`
#[inline]
#[rustc_const_stable(feature = "const_poll", since = "1.49.0")]
#[stable(feature = "futures_api", since = "1.36.0")]
pub const fn is_ready(&self) -> bool {
matches!(*self, Poll::Ready(_))
}
/// Returns `true` if this is `Poll::Pending`
#[inline]
#[rustc_const_stable(feature = "const_poll", since = "1.49.0")]
#[stable(feature = "futures_api", since = "1.36.0")]
pub const fn is_pending(&self) -> bool {
!self.is_ready()
}
}
impl<T, E> Poll<Result<T, E>> {
/// Changes the success value of this `Poll` with the closure provided.
#[stable(feature = "futures_api", since = "1.36.0")]
pub fn map_ok<U, F>(self, f: F) -> Poll<Result<U, E>>
where
F: FnOnce(T) -> U,
{
match self {
Poll::Ready(Ok(t)) => Poll::Ready(Ok(f(t))),
Poll::Ready(Err(e)) => Poll::Ready(Err(e)),
Poll::Pending => Poll::Pending,
}
}
/// Changes the error value of this `Poll` with the closure provided.
#[stable(feature = "futures_api", since = "1.36.0")]
pub fn map_err<U, F>(self, f: F) -> Poll<Result<T, U>>
where
F: FnOnce(E) -> U,
{
match self {
Poll::Ready(Ok(t)) => Poll::Ready(Ok(t)),
Poll::Ready(Err(e)) => Poll::Ready(Err(f(e))),
Poll::Pending => Poll::Pending,
}
}
}
impl<T, E> Poll<Option<Result<T, E>>> {
/// Changes the success value of this `Poll` with the closure provided.
#[stable(feature = "poll_map", since = "1.51.0")]
pub fn map_ok<U, F>(self, f: F) -> Poll<Option<Result<U, E>>>
where
F: FnOnce(T) -> U,
{
match self {
Poll::Ready(Some(Ok(t))) => Poll::Ready(Some(Ok(f(t)))),
Poll::Ready(Some(Err(e))) => Poll::Ready(Some(Err(e))),
Poll::Ready(None) => Poll::Ready(None),
Poll::Pending => Poll::Pending,
}
}
/// Changes the error value of this `Poll` with the closure provided.
#[stable(feature = "poll_map", since = "1.51.0")]
pub fn map_err<U, F>(self, f: F) -> Poll<Option<Result<T, U>>>
where
F: FnOnce(E) -> U,
{
match self {
Poll::Ready(Some(Ok(t))) => Poll::Ready(Some(Ok(t))),
Poll::Ready(Some(Err(e))) => Poll::Ready(Some(Err(f(e)))),
Poll::Ready(None) => Poll::Ready(None),
Poll::Pending => Poll::Pending,
}
}
}
#[stable(feature = "futures_api", since = "1.36.0")]
impl<T> From<T> for Poll<T> {
/// Convert to a `Ready` variant.
///
/// # Example
///
/// ```
/// # use core::task::Poll;
/// assert_eq!(Poll::from(true), Poll::Ready(true));
/// ```
fn from(t: T) -> Poll<T> {
Poll::Ready(t)
}
}
#[stable(feature = "futures_api", since = "1.36.0")]
#[cfg(bootstrap)]
impl<T, E> ops::TryV1 for Poll<Result<T, E>> {
type Output = Poll<T>;
type Error = E;
#[inline]
fn into_result(self) -> Result<Self::Output, Self::Error> {
match self {
Poll::Ready(Ok(x)) => Ok(Poll::Ready(x)),
Poll::Ready(Err(e)) => Err(e),
Poll::Pending => Ok(Poll::Pending),
}
}
#[inline]
fn from_error(e: Self::Error) -> Self {
Poll::Ready(Err(e))
}
#[inline]
fn from_ok(x: Self::Output) -> Self {
x.map(Ok)
}
}
#[unstable(feature = "try_trait_v2", issue = "84277")]
impl<T, E> ops::TryV2 for Poll<Result<T, E>> {
type Output = Poll<T>;
type Residual = Result<convert::Infallible, E>;
#[inline]
fn from_output(c: Self::Output) -> Self {
c.map(Ok)
}
#[inline]
fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
match self {
Poll::Ready(Ok(x)) => ControlFlow::Continue(Poll::Ready(x)),
Poll::Ready(Err(e)) => ControlFlow::Break(Err(e)),
Poll::Pending => ControlFlow::Continue(Poll::Pending),
}
}
}
#[unstable(feature = "try_trait_v2", issue = "84277")]
impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>> for Poll<Result<T, F>> {
#[inline]
fn from_residual(x: Result<convert::Infallible, E>) -> Self {
match x {
Err(e) => Poll::Ready(Err(From::from(e))),
}
}
}
#[stable(feature = "futures_api", since = "1.36.0")]
#[cfg(bootstrap)]
impl<T, E> ops::TryV1 for Poll<Option<Result<T, E>>> {
type Output = Poll<Option<T>>;
type Error = E;
#[inline]
fn into_result(self) -> Result<Self::Output, Self::Error> {
match self {
Poll::Ready(Some(Ok(x))) => Ok(Poll::Ready(Some(x))),
Poll::Ready(Some(Err(e))) => Err(e),
Poll::Ready(None) => Ok(Poll::Ready(None)),
Poll::Pending => Ok(Poll::Pending),
}
}
#[inline]
fn from_error(e: Self::Error) -> Self {
Poll::Ready(Some(Err(e)))
}
#[inline]
fn from_ok(x: Self::Output) -> Self {
x.map(|x| x.map(Ok))
}
}
#[unstable(feature = "try_trait_v2", issue = "84277")]
impl<T, E> ops::TryV2 for Poll<Option<Result<T, E>>> {
type Output = Poll<Option<T>>;
type Residual = Result<convert::Infallible, E>;
#[inline]
fn from_output(c: Self::Output) -> Self {
c.map(|x| x.map(Ok))
}
#[inline]
fn branch(self) -> ControlFlow<Self::Residual, Self::Output> {
match self {
Poll::Ready(Some(Ok(x))) => ControlFlow::Continue(Poll::Ready(Some(x))),
Poll::Ready(Some(Err(e))) => ControlFlow::Break(Err(e)),
Poll::Ready(None) => ControlFlow::Continue(Poll::Ready(None)),
Poll::Pending => ControlFlow::Continue(Poll::Pending),
}
}
}
#[unstable(feature = "try_trait_v2", issue = "84277")]
impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>>
for Poll<Option<Result<T, F>>>
{
#[inline]
fn from_residual(x: Result<convert::Infallible, E>) -> Self {
match x {
Err(e) => Poll::Ready(Some(Err(From::from(e)))),
}
}
}