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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /vendor/futures-util/src/future/select_ok.rs | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/futures-util/src/future/select_ok.rs')
-rw-r--r-- | vendor/futures-util/src/future/select_ok.rs | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/vendor/futures-util/src/future/select_ok.rs b/vendor/futures-util/src/future/select_ok.rs new file mode 100644 index 000000000..0ad83c6db --- /dev/null +++ b/vendor/futures-util/src/future/select_ok.rs @@ -0,0 +1,85 @@ +use super::assert_future; +use crate::future::TryFutureExt; +use alloc::vec::Vec; +use core::iter::FromIterator; +use core::mem; +use core::pin::Pin; +use futures_core::future::{Future, TryFuture}; +use futures_core::task::{Context, Poll}; + +/// Future for the [`select_ok`] function. +#[derive(Debug)] +#[must_use = "futures do nothing unless you `.await` or poll them"] +pub struct SelectOk<Fut> { + inner: Vec<Fut>, +} + +impl<Fut: Unpin> Unpin for SelectOk<Fut> {} + +/// Creates a new future which will select the first successful future over a list of futures. +/// +/// The returned future will wait for any future within `iter` to be ready and Ok. Unlike +/// `select_all`, this will only return the first successful completion, or the last +/// failure. This is useful in contexts where any success is desired and failures +/// are ignored, unless all the futures fail. +/// +/// This function is only available when the `std` or `alloc` feature of this +/// library is activated, and it is activated by default. +/// +/// # Panics +/// +/// This function will panic if the iterator specified contains no items. +pub fn select_ok<I>(iter: I) -> SelectOk<I::Item> +where + I: IntoIterator, + I::Item: TryFuture + Unpin, +{ + let ret = SelectOk { inner: iter.into_iter().collect() }; + assert!(!ret.inner.is_empty(), "iterator provided to select_ok was empty"); + assert_future::< + Result<(<I::Item as TryFuture>::Ok, Vec<I::Item>), <I::Item as TryFuture>::Error>, + _, + >(ret) +} + +impl<Fut: TryFuture + Unpin> Future for SelectOk<Fut> { + type Output = Result<(Fut::Ok, Vec<Fut>), Fut::Error>; + + fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { + // loop until we've either exhausted all errors, a success was hit, or nothing is ready + loop { + let item = + self.inner.iter_mut().enumerate().find_map(|(i, f)| match f.try_poll_unpin(cx) { + Poll::Pending => None, + Poll::Ready(e) => Some((i, e)), + }); + match item { + Some((idx, res)) => { + // always remove Ok or Err, if it's not the last Err continue looping + drop(self.inner.remove(idx)); + match res { + Ok(e) => { + let rest = mem::replace(&mut self.inner, Vec::new()); + return Poll::Ready(Ok((e, rest))); + } + Err(e) => { + if self.inner.is_empty() { + return Poll::Ready(Err(e)); + } + } + } + } + None => { + // based on the filter above, nothing is ready, return + return Poll::Pending; + } + } + } + } +} + +impl<Fut: TryFuture + Unpin> FromIterator<Fut> for SelectOk<Fut> { + fn from_iter<T: IntoIterator<Item = Fut>>(iter: T) -> Self { + select_ok(iter) + } +} |