diff --git a/Cargo.toml b/Cargo.toml index 9ada005..71fcac7 100644 --- a/Cargo.toml +++ b/Cargo.toml @@ -23,6 +23,7 @@ harness = false [dependencies] bitvec = { version = "1.0.1", default-features = false, features = ["alloc"] } futures-core = "0.3" +paste = "1.0.9" pin-project = "1.0.8" [dev-dependencies] diff --git a/src/future/join/tuple.rs b/src/future/join/tuple.rs index 9c91660..f18a2e3 100644 --- a/src/future/join/tuple.rs +++ b/src/future/join/tuple.rs @@ -1,28 +1,37 @@ use super::Join as JoinTrait; -use crate::utils::MaybeDone; +use crate::utils::PollState; use core::fmt::{self, Debug}; use core::future::{Future, IntoFuture}; +use core::mem::MaybeUninit; use core::pin::Pin; use core::task::{Context, Poll}; -use pin_project::pin_project; +use pin_project::{pin_project, pinned_drop}; -macro_rules! impl_merge_tuple { +use paste::paste; + +macro_rules! impl_join_tuple { ($StructName:ident $($F:ident)*) => { - /// Waits for two similarly-typed futures to complete. - /// - /// This `struct` is created by the [`join`] method on the [`Join`] trait. See - /// its documentation for more. - /// - /// [`join`]: crate::future::Join::join - /// [`Join`]: crate::future::Join - #[pin_project] - #[must_use = "futures do nothing unless you `.await` or poll them"] - #[allow(non_snake_case)] - pub struct $StructName<$($F: Future),*> { - done: bool, - $(#[pin] $F: MaybeDone<$F>,)* + paste!{ + /// Waits for two similarly-typed futures to complete. + /// + /// This `struct` is created by the [`join`] method on the [`Join`] trait. See + /// its documentation for more. + /// + /// [`join`]: crate::future::Join::join + /// [`Join`]: crate::future::Join + #[pin_project(PinnedDrop)] + #[must_use = "futures do nothing unless you `.await` or poll them"] + #[allow(non_snake_case)] + pub struct $StructName<$($F: Future),*> { + done: bool, + $( + #[pin] $F: $F, + [<$F _out>]: MaybeUninit<$F::Output>, + [<$F _state>]: PollState, + )* + } } impl<$($F),*> Debug for $StructName<$($F),*> @@ -31,9 +40,11 @@ macro_rules! impl_merge_tuple { $F::Output: Debug, )* { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_tuple("Join") - $(.field(&self.$F))* - .finish() + paste!{ + f.debug_tuple("Join") + $(.field(&self.$F).field(&self.[<$F _state >]))* + .finish() + } } } @@ -50,11 +61,24 @@ macro_rules! impl_merge_tuple { let mut this = self.project(); assert!(!*this.done, "Futures must not be polled after completing"); - $(all_done &= this.$F.as_mut().poll(cx).is_ready();)* + // Poll futures + paste! { + $( + if this.[<$F _state>].is_pending() { + if let Poll::Ready(out) = this.$F.poll(cx) { + *this.[<$F _out>] = MaybeUninit::new(out); + *this.[<$F _state>] = PollState::Done; + } + } + all_done &= this.[<$F _state>].is_done(); + )* + } if all_done { *this.done = true; - Poll::Ready(($(this.$F.take().unwrap()),*)) + paste! { + Poll::Ready(($( unsafe { this.[<$F _out>].assume_init_read() }),*)) + } } else { Poll::Pending } @@ -71,28 +95,53 @@ macro_rules! impl_merge_tuple { fn join(self) -> Self::Future { let ($($F,)*): ($($F,)*) = self; - $StructName { - done: false, - $($F: MaybeDone::new($F.into_future())),* + paste! { + $StructName { + done: false, + $( + $F: $F.into_future(), + [<$F _out>]: MaybeUninit::uninit(), + [<$F _state>]: PollState::default(), + )* + } + } + } + } + + #[pinned_drop] + impl<$($F,)*> PinnedDrop for $StructName<$($F,)*> + where $( + $F: Future, + )* { + fn drop(self: Pin<&mut Self>) { + let _this = self.project(); + + paste! { + $( + if _this.[<$F _state>].is_done() { + // SAFETY: if the future is marked as done, we can safelly drop its out + unsafe { _this.[<$F _out>].assume_init_drop() }; + } + )* } } } }; } -impl_merge_tuple! { Join0 } -impl_merge_tuple! { Join1 A } -impl_merge_tuple! { Join2 A B } -impl_merge_tuple! { Join3 A B C } -impl_merge_tuple! { Join4 A B C D } -impl_merge_tuple! { Join5 A B C D E } -impl_merge_tuple! { Join6 A B C D E F } -impl_merge_tuple! { Join7 A B C D E F G } -impl_merge_tuple! { Join8 A B C D E F G H } -impl_merge_tuple! { Join9 A B C D E F G H I } -impl_merge_tuple! { Join10 A B C D E F G H I J } -impl_merge_tuple! { Join11 A B C D E F G H I J K } -impl_merge_tuple! { Join12 A B C D E F G H I J K L } +impl_join_tuple! { Join0 } +impl_join_tuple! { Join1 A } +impl_join_tuple! { Join2 A B } +impl_join_tuple! { Join3 A B C } +impl_join_tuple! { Join4 A B C D } +impl_join_tuple! { Join5 A B C D E } +impl_join_tuple! { Join6 A B C D E F } +impl_join_tuple! { Join7 A B C D E F G } +impl_join_tuple! { Join8 A B C D E F G H } +impl_join_tuple! { Join9 A B C D E F G H I } +impl_join_tuple! { Join10 A B C D E F G H I J } +impl_join_tuple! { Join11 A B C D E F G H I J K } +impl_join_tuple! { Join12 A B C D E F G H I J K L } #[cfg(test)] mod test {