feat: add typed iterators for StreamMap and StreamSet

src/lib.rs

@@ -12,8 +12,10 @@ pub use futures_tuple_set::FuturesTupleSet;
 pub use stream_map::StreamMap;
 pub use stream_set::StreamSet;
 
+use std::any::Any;
 use std::fmt;
 use std::fmt::Formatter;
+use std::pin::Pin;
 use std::time::Duration;
 
 /// A future failed to complete within the given timeout.
@@ -35,7 +37,7 @@ impl fmt::Display for Timeout {
 }
 
 /// Error of a future pushing
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq)]
 pub enum PushError<T> {
     /// The length of the set is equal to the capacity
     BeyondCapacity(T),
@@ -45,4 +47,20 @@ pub enum PushError<T> {
     Replaced(T),
 }
 
+impl<T> fmt::Debug for PushError<T> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::BeyondCapacity(_) => f.debug_tuple("BeyondCapacity").finish(),
+            Self::Replaced(_) => f.debug_tuple("Replaced").finish(),
+        }
+    }
+}
+
 impl std::error::Error for Timeout {}
+
+#[doc(hidden)]
+pub trait AnyStream: futures_util::Stream + Any + Unpin + Send {}
+
+impl<T> AnyStream for T where T: futures_util::Stream + Any + Unpin + Send {}
+
+type BoxStream<T> = Pin<Box<dyn AnyStream<Item = T> + Send>>;

src/stream_map.rs

@@ -1,20 +1,21 @@
+use std::any::Any;
 use std::mem;
 use std::pin::Pin;
 use std::task::{Context, Poll, Waker};
 use std::time::Duration;
 
-use futures_util::stream::{BoxStream, SelectAll};
+use futures_util::stream::SelectAll;
 use futures_util::{stream, FutureExt, Stream, StreamExt};
 
-use crate::{Delay, PushError, Timeout};
+use crate::{AnyStream, BoxStream, Delay, PushError, Timeout};
 
 /// Represents a map of [`Stream`]s.
 ///
 /// Each stream must finish within the specified time and the map never outgrows its capacity.
 pub struct StreamMap<ID, O> {
     make_delay: Box<dyn Fn() -> Delay + Send + Sync>,
     capacity: usize,
-    inner: SelectAll<TaggedStream<ID, TimeoutStream<BoxStream<'static, O>>>>,
+    inner: SelectAll<TaggedStream<ID, TimeoutStream<BoxStream<O>>>>,
     empty_waker: Option<Waker>,
     full_waker: Option<Waker>,
 }
@@ -42,10 +43,10 @@ where
     /// Push a stream into the map.
     pub fn try_push<F>(&mut self, id: ID, stream: F) -> Result<(), PushError<BoxStream<O>>>
     where
-        F: Stream<Item = O> + Send + 'static,
+        F: AnyStream<Item = O>,
     {
         if self.inner.len() >= self.capacity {
-            return Err(PushError::BeyondCapacity(stream.boxed()));
+            return Err(PushError::BeyondCapacity(Box::pin(stream)));
         }
 
         if let Some(waker) = self.empty_waker.take() {
@@ -56,7 +57,7 @@ where
         self.inner.push(TaggedStream::new(
             id,
             TimeoutStream {
-                inner: stream.boxed(),
+                inner: Box::pin(stream),
                 timeout: (self.make_delay)(),
             },
         ));
@@ -67,10 +68,10 @@ where
         }
     }
 
-    pub fn remove(&mut self, id: ID) -> Option<BoxStream<'static, O>> {
+    pub fn remove(&mut self, id: ID) -> Option<BoxStream<O>> {
         let tagged = self.inner.iter_mut().find(|s| s.key == id)?;
 
-        let inner = mem::replace(&mut tagged.inner.inner, stream::pending().boxed());
+        let inner = mem::replace(&mut tagged.inner.inner, Box::pin(stream::pending()));
         tagged.exhausted = true; // Setting this will emit `None` on the next poll and ensure `SelectAll` cleans up the resources.
 
         Some(inner)
@@ -113,6 +114,36 @@ where
             Some((id, None)) => Poll::Ready((id, None)),
         }
     }
+
+    /// Returns an iterator over all streams whose inner type is `T`.
+    ///
+    /// If downcasting a stream to `T` fails it will be skipped in the iterator.
+    pub fn iter_typed<T>(&self) -> impl Iterator<Item = (&ID, &T)>
+    where
+        T: 'static,
+    {
+        self.inner.iter().filter_map(|a| {
+            let pin = a.inner.inner.as_ref();
+            let any = Pin::into_inner(pin) as &(dyn Any + Send);
+            let inner = any.downcast_ref::<T>()?;
+            Some((&a.key, inner))
+        })
+    }
+
+    /// Returns an iterator with mutable access over all streams whose inner type is `T`.
+    ///
+    /// If downcasting a stream to `T` fails it will be skipped in the iterator.
+    pub fn iter_mut_typed<T>(&mut self) -> impl Iterator<Item = (&mut ID, &mut T)>
+    where
+        T: 'static,
+    {
+        self.inner.iter_mut().filter_map(|a| {
+            let pin = a.inner.inner.as_mut();
+            let any = Pin::into_inner(pin) as &mut (dyn Any + Send);
+            let inner = any.downcast_mut::<T>()?;
+            Some((&mut a.key, inner))
+        })
+    }
 }
 
 struct TimeoutStream<S> {
@@ -304,6 +335,29 @@ mod tests {
         assert!(duration >= DELAY * NUM_STREAMS);
     }
 
+    #[test]
+    fn can_iter_named_streams() {
+        const N: usize = 10;
+        let mut streams = StreamMap::new(|| Delay::futures_timer(Duration::from_millis(100)), N);
+        let mut sender = Vec::with_capacity(N);
+        for i in 0..N {
+            let (tx, rx) = mpsc::channel::<()>(1);
+            streams.try_push(format!("ID{i}"), rx).unwrap();
+            sender.push(tx);
+        }
+        assert_eq!(streams.iter_typed::<mpsc::Receiver<()>>().count(), N);
+        for (i, (id, _)) in streams.iter_typed::<mpsc::Receiver<()>>().enumerate() {
+            let expect_id = format!("ID{}", N - i - 1); // Reverse order.
+            assert_eq!(id, &expect_id);
+        }
+        assert!(!sender.iter().any(|tx| tx.is_closed()));
+
+        for (_, rx) in streams.iter_mut_typed::<mpsc::Receiver<()>>() {
+            rx.close();
+        }
+        assert!(sender.iter().all(|tx| tx.is_closed()));
+    }
+
     struct Task {
         item_delay: Duration,
         num_streams: usize,

src/stream_set.rs

@@ -1,8 +1,6 @@
-use futures_util::stream::BoxStream;
-use futures_util::Stream;
 use std::task::{ready, Context, Poll};
 
-use crate::{Delay, PushError, StreamMap, Timeout};
+use crate::{AnyStream, BoxStream, Delay, PushError, StreamMap, Timeout};
 
 /// Represents a set of [Stream]s.
 ///
@@ -32,7 +30,7 @@ where
     /// In that case, the stream is not added to the set.
     pub fn try_push<F>(&mut self, stream: F) -> Result<(), BoxStream<O>>
     where
-        F: Stream<Item = O> + Send + 'static,
+        F: AnyStream<Item = O>,
     {
         self.id = self.id.wrapping_add(1);
 
@@ -60,4 +58,24 @@ where
 
         Poll::Ready(res)
     }
+
+    /// Returns an iterator over all streams whose inner type is `T`.
+    ///
+    /// If downcasting a stream to `T` fails it will be skipped in the iterator.
+    pub fn iter_typed<T>(&self) -> impl Iterator<Item = &T>
+    where
+        T: 'static,
+    {
+        self.inner.iter_typed().map(|(_, item)| item)
+    }
+
+    /// Returns an iterator with mutable access over all streams whose inner type is `T`.
+    ///
+    /// If downcasting a stream to `T` fails it will be skipped in the iterator.
+    pub fn iter_mut_typed<T>(&mut self) -> impl Iterator<Item = &mut T>
+    where
+        T: 'static,
+    {
+        self.inner.iter_mut_typed().map(|(_, item)| item)
+    }
 }