additional futures extension utils

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/utils/future/ext_ext.rs

@@ -0,0 +1,34 @@
+//! Extended external extensions to futures::FutureExt
+
+use std::marker::Unpin;
+
+use futures::{future, future::Select, Future};
+
+/// This interface is not necessarily complete; feel free to add as-needed.
+pub trait ExtExt<T>
+where
+	Self: Future<Output = T> + Send,
+{
+	fn until<A, B, F>(self, f: F) -> Select<A, B>
+	where
+		Self: Sized,
+		F: FnOnce() -> B,
+		A: Future<Output = T> + From<Self> + Send + Unpin,
+		B: Future<Output = ()> + Send + Unpin;
+}
+
+impl<T, Fut> ExtExt<T> for Fut
+where
+	Fut: Future<Output = T> + Send,
+{
+	#[inline]
+	fn until<A, B, F>(self, f: F) -> Select<A, B>
+	where
+		Self: Sized,
+		F: FnOnce() -> B,
+		A: Future<Output = T> + From<Self> + Send + Unpin,
+		B: Future<Output = ()> + Send + Unpin,
+	{
+		future::select(self.into(), f())
+	}
+}

src/core/utils/future/mod.rs

@@ -1,5 +1,7 @@
+mod ext_ext;
 mod option_ext;
 mod try_ext_ext;
 
+pub use ext_ext::ExtExt;
 pub use option_ext::OptionExt;
 pub use try_ext_ext::TryExtExt;

src/core/utils/future/try_ext_ext.rs

@@ -4,8 +4,11 @@
 // caller only ever caring about result status while discarding all contents.
 #![allow(clippy::wrong_self_convention)]
 
+use std::marker::Unpin;
+
 use futures::{
-	future::{MapOkOrElse, UnwrapOrElse},
+	future,
+	future::{MapOkOrElse, TrySelect, UnwrapOrElse},
 	TryFuture, TryFutureExt,
 };
 
@@ -46,6 +49,13 @@ where
 	where
 		Self: Sized;
 
+	fn try_until<A, B, F>(self, f: F) -> TrySelect<A, B>
+	where
+		Self: Sized,
+		F: FnOnce() -> B,
+		A: TryFuture<Ok = Self::Ok> + From<Self> + Send + Unpin,
+		B: TryFuture<Ok = (), Error = Self::Error> + Send + Unpin;
+
 	fn unwrap_or(
 		self,
 		default: Self::Ok,
@@ -110,6 +120,17 @@ where
 		self.map_ok_or(None, Some)
 	}
 
+	#[inline]
+	fn try_until<A, B, F>(self, f: F) -> TrySelect<A, B>
+	where
+		Self: Sized,
+		F: FnOnce() -> B,
+		A: TryFuture<Ok = Self::Ok> + From<Self> + Send + Unpin,
+		B: TryFuture<Ok = (), Error = Self::Error> + Send + Unpin,
+	{
+		future::try_select(self.into(), f())
+	}
+
 	#[inline]
 	fn unwrap_or(
 		self,