diff options
Diffstat (limited to 'vendor/futures-util/src/future/try_join_all.rs')
| -rw-r--r-- | vendor/futures-util/src/future/try_join_all.rs | 137 |
1 files changed, 100 insertions, 37 deletions
diff --git a/vendor/futures-util/src/future/try_join_all.rs b/vendor/futures-util/src/future/try_join_all.rs index 29244af83..506f45065 100644 --- a/vendor/futures-util/src/future/try_join_all.rs +++ b/vendor/futures-util/src/future/try_join_all.rs @@ -10,14 +10,11 @@ use core::mem; use core::pin::Pin; use core::task::{Context, Poll}; -use super::{assert_future, TryFuture, TryMaybeDone}; +use super::{assert_future, join_all, IntoFuture, TryFuture, TryMaybeDone}; -fn iter_pin_mut<T>(slice: Pin<&mut [T]>) -> impl Iterator<Item = Pin<&mut T>> { - // Safety: `std` _could_ make this unsound if it were to decide Pin's - // invariants aren't required to transmit through slices. Otherwise this has - // the same safety as a normal field pin projection. - unsafe { slice.get_unchecked_mut() }.iter_mut().map(|t| unsafe { Pin::new_unchecked(t) }) -} +#[cfg(not(futures_no_atomic_cas))] +use crate::stream::{FuturesOrdered, TryCollect, TryStreamExt}; +use crate::TryFutureExt; enum FinalState<E = ()> { Pending, @@ -31,7 +28,20 @@ pub struct TryJoinAll<F> where F: TryFuture, { - elems: Pin<Box<[TryMaybeDone<F>]>>, + kind: TryJoinAllKind<F>, +} + +enum TryJoinAllKind<F> +where + F: TryFuture, +{ + Small { + elems: Pin<Box<[TryMaybeDone<IntoFuture<F>>]>>, + }, + #[cfg(not(futures_no_atomic_cas))] + Big { + fut: TryCollect<FuturesOrdered<IntoFuture<F>>, Vec<F::Ok>>, + }, } impl<F> fmt::Debug for TryJoinAll<F> @@ -39,9 +49,16 @@ where F: TryFuture + fmt::Debug, F::Ok: fmt::Debug, F::Error: fmt::Debug, + F::Output: fmt::Debug, { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("TryJoinAll").field("elems", &self.elems).finish() + match self.kind { + TryJoinAllKind::Small { ref elems } => { + f.debug_struct("TryJoinAll").field("elems", elems).finish() + } + #[cfg(not(futures_no_atomic_cas))] + TryJoinAllKind::Big { ref fut, .. } => fmt::Debug::fmt(fut, f), + } } } @@ -60,6 +77,20 @@ where /// This function is only available when the `std` or `alloc` feature of this /// library is activated, and it is activated by default. /// +/// # See Also +/// +/// `try_join_all` will switch to the more powerful [`FuturesOrdered`] for performance +/// reasons if the number of futures is large. You may want to look into using it or +/// it's counterpart [`FuturesUnordered`][crate::stream::FuturesUnordered] directly. +/// +/// Some examples for additional functionality provided by these are: +/// +/// * Adding new futures to the set even after it has been started. +/// +/// * Only polling the specific futures that have been woken. In cases where +/// you have a lot of futures this will result in much more efficient polling. +/// +/// /// # Examples /// /// ``` @@ -83,15 +114,37 @@ where /// assert_eq!(try_join_all(futures).await, Err(2)); /// # }); /// ``` -pub fn try_join_all<I>(i: I) -> TryJoinAll<I::Item> +pub fn try_join_all<I>(iter: I) -> TryJoinAll<I::Item> where I: IntoIterator, I::Item: TryFuture, { - let elems: Box<[_]> = i.into_iter().map(TryMaybeDone::Future).collect(); - assert_future::<Result<Vec<<I::Item as TryFuture>::Ok>, <I::Item as TryFuture>::Error>, _>( - TryJoinAll { elems: elems.into() }, - ) + let iter = iter.into_iter().map(TryFutureExt::into_future); + + #[cfg(futures_no_atomic_cas)] + { + let kind = TryJoinAllKind::Small { + elems: iter.map(TryMaybeDone::Future).collect::<Box<[_]>>().into(), + }; + + assert_future::<Result<Vec<<I::Item as TryFuture>::Ok>, <I::Item as TryFuture>::Error>, _>( + TryJoinAll { kind }, + ) + } + + #[cfg(not(futures_no_atomic_cas))] + { + let kind = match iter.size_hint().1 { + Some(max) if max <= join_all::SMALL => TryJoinAllKind::Small { + elems: iter.map(TryMaybeDone::Future).collect::<Box<[_]>>().into(), + }, + _ => TryJoinAllKind::Big { fut: iter.collect::<FuturesOrdered<_>>().try_collect() }, + }; + + assert_future::<Result<Vec<<I::Item as TryFuture>::Ok>, <I::Item as TryFuture>::Error>, _>( + TryJoinAll { kind }, + ) + } } impl<F> Future for TryJoinAll<F> @@ -101,36 +154,46 @@ where type Output = Result<Vec<F::Ok>, F::Error>; fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { - let mut state = FinalState::AllDone; - - for elem in iter_pin_mut(self.elems.as_mut()) { - match elem.try_poll(cx) { - Poll::Pending => state = FinalState::Pending, - Poll::Ready(Ok(())) => {} - Poll::Ready(Err(e)) => { - state = FinalState::Error(e); - break; + match &mut self.kind { + TryJoinAllKind::Small { elems } => { + let mut state = FinalState::AllDone; + + for elem in join_all::iter_pin_mut(elems.as_mut()) { + match elem.try_poll(cx) { + Poll::Pending => state = FinalState::Pending, + Poll::Ready(Ok(())) => {} + Poll::Ready(Err(e)) => { + state = FinalState::Error(e); + break; + } + } } - } - } - match state { - FinalState::Pending => Poll::Pending, - FinalState::AllDone => { - let mut elems = mem::replace(&mut self.elems, Box::pin([])); - let results = - iter_pin_mut(elems.as_mut()).map(|e| e.take_output().unwrap()).collect(); - Poll::Ready(Ok(results)) - } - FinalState::Error(e) => { - let _ = mem::replace(&mut self.elems, Box::pin([])); - Poll::Ready(Err(e)) + match state { + FinalState::Pending => Poll::Pending, + FinalState::AllDone => { + let mut elems = mem::replace(elems, Box::pin([])); + let results = join_all::iter_pin_mut(elems.as_mut()) + .map(|e| e.take_output().unwrap()) + .collect(); + Poll::Ready(Ok(results)) + } + FinalState::Error(e) => { + let _ = mem::replace(elems, Box::pin([])); + Poll::Ready(Err(e)) + } + } } + #[cfg(not(futures_no_atomic_cas))] + TryJoinAllKind::Big { fut } => Pin::new(fut).poll(cx), } } } -impl<F: TryFuture> FromIterator<F> for TryJoinAll<F> { +impl<F> FromIterator<F> for TryJoinAll<F> +where + F: TryFuture, +{ fn from_iter<T: IntoIterator<Item = F>>(iter: T) -> Self { try_join_all(iter) } |