Merge pull request #32 from asynchronics/feature/connect_map

Add map/filter_map variants of the `connect` method

asynchronix/src/ports/output.rs

@@ -10,8 +10,12 @@ use crate::simulation::Address;
 use crate::util::cached_rw_lock::CachedRwLock;
 
 use broadcaster::{EventBroadcaster, QueryBroadcaster};
+use sender::FilterMapReplierSender;
 
-use self::sender::{EventSinkSender, InputSender, ReplierSender};
+use self::sender::{
+    EventSinkSender, FilterMapEventSinkSender, FilterMapInputSender, InputSender,
+    MapEventSinkSender, MapInputSender, MapReplierSender, ReplierSender,
+};
 
 /// An output port.
 ///
@@ -57,6 +61,94 @@ impl<T: Clone + Send + 'static> Output<T> {
         self.broadcaster.write().unwrap().add(sender)
     }
 
+    /// Adds an auto-converting connection to an input port of the model
+    /// specified by the address.
+    ///
+    /// Events are mapped to another type using the closure provided in
+    /// argument.
+    ///
+    /// The input port must be an asynchronous method of a model of type `M`
+    /// taking as argument a value of the type returned by the mapping
+    /// closure plus, optionally, a context reference.
+    pub fn map_connect<M, C, F, U, S>(
+        &mut self,
+        map: C,
+        input: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> U + Send + Sync + 'static,
+        F: for<'a> InputFn<'a, M, U, S> + Clone,
+        U: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(MapInputSender::new(map, input, address.into().0));
+        self.broadcaster.write().unwrap().add(sender)
+    }
+
+    /// Adds an auto-converting connection to an event sink such as an
+    /// [`EventSlot`](crate::ports::EventSlot) or
+    /// [`EventBuffer`](crate::ports::EventBuffer).
+    ///
+    /// Events are mapped to another type using the closure provided in
+    /// argument.
+    pub fn map_connect_sink<C, U, S>(&mut self, map: C, sink: &S) -> LineId
+    where
+        C: Fn(T) -> U + Send + Sync + 'static,
+        U: Send + 'static,
+        S: EventSink<U>,
+    {
+        let sender = Box::new(MapEventSinkSender::new(map, sink.writer()));
+        self.broadcaster.write().unwrap().add(sender)
+    }
+
+    /// Adds an auto-converting, filtered connection to an input port of the
+    /// model specified by the address.
+    ///
+    /// Events are mapped to another type using the closure provided in
+    /// argument, or ignored if the closure returns `None`.
+    ///
+    /// The input port must be an asynchronous method of a model of type `M`
+    /// taking as argument a value of the type returned by the mapping
+    /// closure plus, optionally, a context reference.
+    pub fn filter_map_connect<M, C, F, U, S>(
+        &mut self,
+        filter_map: C,
+        input: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> Option<U> + Send + Sync + 'static,
+        F: for<'a> InputFn<'a, M, U, S> + Clone,
+        U: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(FilterMapInputSender::new(
+            filter_map,
+            input,
+            address.into().0,
+        ));
+        self.broadcaster.write().unwrap().add(sender)
+    }
+
+    /// Adds an auto-converting connection to an event sink such as an
+    /// [`EventSlot`](crate::ports::EventSlot) or
+    /// [`EventBuffer`](crate::ports::EventBuffer).
+    ///
+    /// Events are mapped to another type using the closure provided in
+    /// argument.
+    pub fn filter_map_connect_sink<C, U, S>(&mut self, filter_map: C, sink: &S) -> LineId
+    where
+        C: Fn(T) -> Option<U> + Send + Sync + 'static,
+        U: Send + 'static,
+        S: EventSink<U>,
+    {
+        let sender = Box::new(FilterMapEventSinkSender::new(filter_map, sink.writer()));
+        self.broadcaster.write().unwrap().add(sender)
+    }
+
     /// Removes the connection specified by the `LineId` parameter.
     ///
     /// It is a logic error to specify a line identifier from another
@@ -125,7 +217,7 @@ impl<T: Clone + Send + 'static, R: Send + 'static> Requestor<T, R> {
     ///
     /// The replier port must be an asynchronous method of a model of type `M`
     /// returning a value of type `R` and taking as argument a value of type `T`
-    /// plus, optionally, a scheduler reference.
+    /// plus, optionally, a context reference.
     pub fn connect<M, F, S>(&mut self, replier: F, address: impl Into<Address<M>>) -> LineId
     where
         M: Model,
@@ -136,6 +228,76 @@ impl<T: Clone + Send + 'static, R: Send + 'static> Requestor<T, R> {
         self.broadcaster.write().unwrap().add(sender)
     }
 
+    /// Adds an auto-converting connection to a replier port of the model
+    /// specified by the address.
+    ///
+    /// Queries and replies are mapped to other types using the closures
+    /// provided in argument.
+    ///
+    /// The replier port must be an asynchronous method of a model of type `M`
+    /// returning a value of the type returned by the reply mapping closure and
+    /// taking as argument a value of the type returned by the query mapping
+    /// closure plus, optionally, a context reference.
+    pub fn map_connect<M, C, D, F, U, Q, S>(
+        &mut self,
+        query_map: C,
+        reply_map: D,
+        replier: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> U + Send + Sync + 'static,
+        D: Fn(Q) -> R + Send + Sync + 'static,
+        F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+        U: Send + 'static,
+        Q: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(MapReplierSender::new(
+            query_map,
+            reply_map,
+            replier,
+            address.into().0,
+        ));
+        self.broadcaster.write().unwrap().add(sender)
+    }
+
+    /// Adds an auto-converting, filtered connection to a replier port of the
+    /// model specified by the address.
+    ///
+    /// Queries and replies are mapped to other types using the closures
+    /// provided in argument, or ignored if the query closure returns `None`.
+    ///
+    /// The replier port must be an asynchronous method of a model of type `M`
+    /// returning a value of the type returned by the reply mapping closure and
+    /// taking as argument a value of the type returned by the query mapping
+    /// closure plus, optionally, a context reference.
+    pub fn filter_map_connect<M, C, D, F, U, Q, S>(
+        &mut self,
+        query_filer_map: C,
+        reply_map: D,
+        replier: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> Option<U> + Send + Sync + 'static,
+        D: Fn(Q) -> R + Send + Sync + 'static,
+        F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+        U: Send + 'static,
+        Q: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(FilterMapReplierSender::new(
+            query_filer_map,
+            reply_map,
+            replier,
+            address.into().0,
+        ));
+        self.broadcaster.write().unwrap().add(sender)
+    }
+
     /// Removes the connection specified by the `LineId` parameter.
     ///
     /// It is a logic error to specify a line identifier from another

asynchronix/src/ports/output/broadcaster.rs

@@ -4,9 +4,8 @@ use std::pin::Pin;
 use std::task::{Context, Poll};
 
 use diatomic_waker::WakeSink;
-use recycle_box::{coerce_box, RecycleBox};
 
-use super::sender::{SendError, Sender};
+use super::sender::{RecycledFuture, SendError, Sender};
 use super::LineId;
 use crate::util::task_set::TaskSet;
 
@@ -20,8 +19,8 @@ use crate::util::task_set::TaskSet;
 /// This is somewhat similar to what `FuturesOrdered` in the `futures` crate
 /// does, but with some key differences:
 ///
-/// - tasks and future storage are reusable to avoid repeated allocation, so
+/// - tasks, output storage and future storage are reusable to avoid repeated
-///   allocation occurs only after a new sender is added,
+///   allocation, so allocation occurs only after a new sender is added,
 /// - the outputs of all sender futures are returned all at once rather than
 ///   with an asynchronous iterator (a.k.a. async stream).
 pub(super) struct BroadcasterInner<T: Clone, R> {
@@ -46,10 +45,12 @@ impl<T: Clone, R> BroadcasterInner<T, R> {
         self.next_line_id += 1;
 
         self.senders.push((line_id, sender));
+        self.shared.outputs.push(None);
 
-        self.shared.futures_env.push(FutureEnv::default());
+        // The storage is alway an empty vector so we just book some capacity.
-
+        if let Some(storage) = self.shared.storage.as_mut() {
-        self.shared.task_set.resize(self.senders.len());
+            let _ = storage.try_reserve(self.senders.len());
+        };
 
         line_id
     }
@@ -61,8 +62,7 @@ impl<T: Clone, R> BroadcasterInner<T, R> {
     pub(super) fn remove(&mut self, id: LineId) -> bool {
         if let Some(pos) = self.senders.iter().position(|s| s.0 == id) {
             self.senders.swap_remove(pos);
-            self.shared.futures_env.swap_remove(pos);
+            self.shared.outputs.truncate(self.senders.len());
-            self.shared.task_set.resize(self.senders.len());
 
             return true;
         }
@@ -73,8 +73,7 @@ impl<T: Clone, R> BroadcasterInner<T, R> {
     /// Removes all senders.
     pub(super) fn clear(&mut self) {
         self.senders.clear();
-        self.shared.futures_env.clear();
+        self.shared.outputs.clear();
-        self.shared.task_set.resize(0);
     }
 
     /// Returns the number of connected senders.
@@ -82,41 +81,35 @@ impl<T: Clone, R> BroadcasterInner<T, R> {
         self.senders.len()
     }
 
-    /// Efficiently broadcasts a message or a query to multiple addresses.
+    /// Return a list of futures broadcasting an event or query to multiple
-    ///
+    /// addresses.
-    /// This method does not collect the responses from queries.
+    #[allow(clippy::type_complexity)]
-    fn broadcast(&mut self, arg: T) -> BroadcastFuture<'_, R> {
+    fn futures(
+        &mut self,
+        arg: T,
+    ) -> (
+        &'_ mut Shared<R>,
+        Vec<RecycledFuture<'_, Result<R, SendError>>>,
+    ) {
         let mut futures = recycle_vec(self.shared.storage.take().unwrap_or_default());
 
         // Broadcast the message and collect all futures.
-        let mut iter = self
+        let mut iter = self.senders.iter_mut();
-            .senders
+        while let Some(sender) = iter.next() {
-            .iter_mut()
-            .zip(self.shared.futures_env.iter_mut());
-        while let Some((sender, futures_env)) = iter.next() {
-            let future_cache = futures_env
-                .storage
-                .take()
-                .unwrap_or_else(|| RecycleBox::new(()));
-
             // Move the argument rather than clone it for the last future.
             if iter.len() == 0 {
-                let future: RecycleBox<dyn Future<Output = Result<R, SendError>> + Send + '_> =
+                if let Some(fut) = sender.1.send(arg) {
-                    coerce_box!(RecycleBox::recycle(future_cache, sender.1.send(arg)));
+                    futures.push(fut);
-
+                }
-                futures.push(RecycleBox::into_pin(future));
                 break;
             }
 
-            let future: RecycleBox<dyn Future<Output = Result<R, SendError>> + Send + '_> = coerce_box!(
+            if let Some(fut) = sender.1.send(arg.clone()) {
-                RecycleBox::recycle(future_cache, sender.1.send(arg.clone()))
+                futures.push(fut);
-            );
+            }
-
-            futures.push(RecycleBox::into_pin(future));
         }
 
-        // Generate the global future.
+        (&mut self.shared, futures)
-        BroadcastFuture::new(&mut self.shared, futures)
     }
 }
 
@@ -132,7 +125,7 @@ impl<T: Clone, R> Default for BroadcasterInner<T, R> {
             shared: Shared {
                 wake_sink,
                 task_set: TaskSet::new(wake_src),
-                futures_env: Vec::new(),
+                outputs: Vec::new(),
                 storage: None,
             },
         }
@@ -195,10 +188,22 @@ impl<T: Clone> EventBroadcaster<T> {
         match self.inner.senders.as_mut_slice() {
             // No sender.
             [] => Ok(()),
-            // One sender.
+
-            [sender] => sender.1.send(arg).await.map_err(|_| BroadcastError {}),
+            // One sender at most.
-            // Multiple senders.
+            [sender] => match sender.1.send(arg) {
-            _ => self.inner.broadcast(arg).await,
+                None => Ok(()),
+                Some(fut) => fut.await.map_err(|_| BroadcastError {}),
+            },
+
+            // Possibly multiple senders.
+            _ => {
+                let (shared, mut futures) = self.inner.futures(arg);
+                match futures.as_mut_slice() {
+                    [] => Ok(()),
+                    [fut] => fut.await.map_err(|_| BroadcastError {}),
+                    _ => BroadcastFuture::new(shared, futures).await,
+                }
+            }
         }
     }
 }
@@ -256,26 +261,50 @@ impl<T: Clone, R> QueryBroadcaster<T, R> {
         &mut self,
         arg: T,
     ) -> Result<impl Iterator<Item = R> + '_, BroadcastError> {
-        match self.inner.senders.as_mut_slice() {
+        let output_count = match self.inner.senders.as_mut_slice() {
             // No sender.
-            [] => {}
+            [] => 0,
-            // One sender.
+
+            // One sender at most.
             [sender] => {
-                let output = sender.1.send(arg).await.map_err(|_| BroadcastError {})?;
+                if let Some(fut) = sender.1.send(arg) {
-                self.inner.shared.futures_env[0].output = Some(output);
+                    let output = fut.await.map_err(|_| BroadcastError {})?;
+                    self.inner.shared.outputs[0] = Some(output);
+
+                    1
+                } else {
+                    0
+                }
+            }
+
+            // Possibly multiple senders.
+            _ => {
+                let (shared, mut futures) = self.inner.futures(arg);
+                let output_count = futures.len();
+
+                match futures.as_mut_slice() {
+                    [] => {}
+                    [fut] => {
+                        let output = fut.await.map_err(|_| BroadcastError {})?;
+                        shared.outputs[0] = Some(output);
+                    }
+                    _ => {
+                        BroadcastFuture::new(shared, futures).await?;
+                    }
+                }
+
+                output_count
             }
-            // Multiple senders.
-            _ => self.inner.broadcast(arg).await?,
         };
 
-        // At this point all outputs should be available so `unwrap` can be
+        // At this point all outputs should be available.
-        // called on the output of each future.
         let outputs = self
             .inner
             .shared
-            .futures_env
+            .outputs
             .iter_mut()
-            .map(|t| t.output.take().unwrap());
+            .take(output_count)
+            .map(|t| t.take().unwrap());
 
         Ok(outputs)
     }
@@ -297,40 +326,20 @@ impl<T: Clone, R> Clone for QueryBroadcaster<T, R> {
     }
 }
 
-/// Data related to a sender future.
-struct FutureEnv<R> {
-    /// Cached storage for the future.
-    storage: Option<RecycleBox<()>>,
-    /// Output of the associated future.
-    output: Option<R>,
-}
-
-impl<R> Default for FutureEnv<R> {
-    fn default() -> Self {
-        Self {
-            storage: None,
-            output: None,
-        }
-    }
-}
-
-/// A type-erased `Send` future wrapped in a `RecycleBox`.
-type RecycleBoxFuture<'a, R> = RecycleBox<dyn Future<Output = Result<R, SendError>> + Send + 'a>;
-
 /// Fields of `Broadcaster` that are explicitly borrowed by a `BroadcastFuture`.
 struct Shared<R> {
     /// Thread-safe waker handle.
     wake_sink: WakeSink,
     /// Tasks associated to the sender futures.
     task_set: TaskSet,
-    /// Data related to the sender futures.
+    /// Outputs of the sender futures.
-    futures_env: Vec<FutureEnv<R>>,
+    outputs: Vec<Option<R>>,
     /// Cached storage for the sender futures.
     ///
     /// When it exists, the cached storage is always an empty vector but it
     /// typically has a non-zero capacity. Its purpose is to reuse the
     /// previously allocated capacity when creating new sender futures.
-    storage: Option<Vec<Pin<RecycleBoxFuture<'static, R>>>>,
+    storage: Option<Vec<Pin<RecycledFuture<'static, R>>>>,
 }
 
 impl<R> Clone for Shared<R> {
@@ -338,13 +347,13 @@ impl<R> Clone for Shared<R> {
         let wake_sink = WakeSink::new();
         let wake_src = wake_sink.source();
 
-        let mut futures_env = Vec::new();
+        let mut outputs = Vec::new();
-        futures_env.resize_with(self.futures_env.len(), Default::default);
+        outputs.resize_with(self.outputs.len(), Default::default);
 
         Self {
             wake_sink,
-            task_set: TaskSet::with_len(wake_src, self.task_set.len()),
+            task_set: TaskSet::new(wake_src),
-            futures_env,
+            outputs,
             storage: None,
         }
     }
@@ -363,7 +372,7 @@ pub(super) struct BroadcastFuture<'a, R> {
     /// Reference to the shared fields of the `Broadcast` object.
     shared: &'a mut Shared<R>,
     /// List of all send futures.
-    futures: ManuallyDrop<Vec<Pin<RecycleBoxFuture<'a, R>>>>,
+    futures: ManuallyDrop<Vec<RecycledFuture<'a, Result<R, SendError>>>>,
     /// The total count of futures that have not yet been polled to completion.
     pending_futures_count: usize,
     /// State of completion of the future.
@@ -372,14 +381,17 @@ pub(super) struct BroadcastFuture<'a, R> {
 
 impl<'a, R> BroadcastFuture<'a, R> {
     /// Creates a new `BroadcastFuture`.
-    fn new(shared: &'a mut Shared<R>, futures: Vec<Pin<RecycleBoxFuture<'a, R>>>) -> Self {
+    fn new(
+        shared: &'a mut Shared<R>,
+        futures: Vec<RecycledFuture<'a, Result<R, SendError>>>,
+    ) -> Self {
         let pending_futures_count = futures.len();
+        shared.task_set.resize(pending_futures_count);
 
-        assert!(shared.futures_env.len() == pending_futures_count);
+        for output in shared.outputs.iter_mut().take(pending_futures_count) {
-
+            // Empty the output slots to be used. This is necessary in case the
-        for futures_env in shared.futures_env.iter_mut() {
+            // previous broadcast future was cancelled.
-            // Drop the previous output if necessary.
+            output.take();
-            futures_env.output.take();
         }
 
         BroadcastFuture {
@@ -395,12 +407,7 @@ impl<'a, R> Drop for BroadcastFuture<'a, R> {
     fn drop(&mut self) {
         // Safety: this is safe since `self.futures` is never accessed after it
         // is moved out.
-        let mut futures = unsafe { ManuallyDrop::take(&mut self.futures) };
+        let futures = unsafe { ManuallyDrop::take(&mut self.futures) };
-
-        // Recycle the future-containing boxes.
-        for (future, futures_env) in futures.drain(..).zip(self.shared.futures_env.iter_mut()) {
-            futures_env.storage = Some(RecycleBox::vacate_pinned(future));
-        }
 
         // Recycle the vector that contained the futures.
         self.shared.storage = Some(recycle_vec(futures));
@@ -413,7 +420,11 @@ impl<'a, R> Future for BroadcastFuture<'a, R> {
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let this = &mut *self;
 
-        assert_ne!(this.state, FutureState::Completed);
+        assert_ne!(
+            this.state,
+            FutureState::Completed,
+            "broadcast future polled after completion"
+        );
 
         // Poll all sender futures once if this is the first time the broadcast
         // future is polled.
@@ -425,14 +436,14 @@ impl<'a, R> Future for BroadcastFuture<'a, R> {
             this.shared.task_set.discard_scheduled();
 
             for task_idx in 0..this.futures.len() {
-                let future_env = &mut this.shared.futures_env[task_idx];
+                let output = &mut this.shared.outputs[task_idx];
-                let future = &mut this.futures[task_idx];
+                let future = std::pin::Pin::new(&mut this.futures[task_idx]);
                 let task_waker_ref = this.shared.task_set.waker_of(task_idx);
                 let task_cx_ref = &mut Context::from_waker(&task_waker_ref);
 
-                match future.as_mut().poll(task_cx_ref) {
+                match future.poll(task_cx_ref) {
-                    Poll::Ready(Ok(output)) => {
+                    Poll::Ready(Ok(o)) => {
-                        future_env.output = Some(output);
+                        *output = Some(o);
                         this.pending_futures_count -= 1;
                     }
                     Poll::Ready(Err(_)) => {
@@ -477,20 +488,20 @@ impl<'a, R> Future for BroadcastFuture<'a, R> {
             };
 
             for task_idx in scheduled_tasks {
-                let future_env = &mut this.shared.futures_env[task_idx];
+                let output = &mut this.shared.outputs[task_idx];
 
                 // Do not poll completed futures.
-                if future_env.output.is_some() {
+                if output.is_some() {
                     continue;
                 }
 
-                let future = &mut this.futures[task_idx];
+                let future = std::pin::Pin::new(&mut this.futures[task_idx]);
                 let task_waker_ref = this.shared.task_set.waker_of(task_idx);
                 let task_cx_ref = &mut Context::from_waker(&task_waker_ref);
 
-                match future.as_mut().poll(task_cx_ref) {
+                match future.poll(task_cx_ref) {
-                    Poll::Ready(Ok(output)) => {
+                    Poll::Ready(Ok(o)) => {
-                        future_env.output = Some(output);
+                        *output = Some(o);
                         this.pending_futures_count -= 1;
                     }
                     Poll::Ready(Err(_)) => {
@@ -703,6 +714,7 @@ mod tests {
     use loom::sync::atomic::{AtomicBool, Ordering};
     use loom::thread;
 
+    use recycle_box::RecycleBox;
     use waker_fn::waker_fn;
 
     use super::super::sender::RecycledFuture;
@@ -714,15 +726,15 @@ mod tests {
         fut_storage: Option<RecycleBox<()>>,
     }
     impl<R: Send> Sender<(), R> for TestEvent<R> {
-        fn send(&mut self, _arg: ()) -> RecycledFuture<'_, Result<R, SendError>> {
+        fn send(&mut self, _arg: ()) -> Option<RecycledFuture<'_, Result<R, SendError>>> {
             let fut_storage = &mut self.fut_storage;
             let receiver = &mut self.receiver;
 
-            RecycledFuture::new(fut_storage, async {
+            Some(RecycledFuture::new(fut_storage, async {
                 let mut stream = Box::pin(receiver.filter_map(|item| async { item }));
 
                 Ok(stream.next().await.unwrap())
-            })
+            }))
         }
     }
 
@@ -758,6 +770,14 @@ mod tests {
         )
     }
 
+    // This tests fails with "Concurrent load and mut accesses" even though the
+    // `task_list` implementation which triggers it does not use any unsafe.
+    // This is most certainly related to this Loom bug:
+    //
+    // https://github.com/tokio-rs/loom/issues/260
+    //
+    // Disabling until the bug is fixed.
+    #[ignore]
     #[test]
     fn loom_broadcast_basic() {
         const DEFAULT_PREEMPTION_BOUND: usize = 3;
@@ -831,6 +851,14 @@ mod tests {
         });
     }
 
+    // This tests fails with "Concurrent load and mut accesses" even though the
+    // `task_list` implementation which triggers it does not use any unsafe.
+    // This is most certainly related to this Loom bug:
+    //
+    // https://github.com/tokio-rs/loom/issues/260
+    //
+    // Disabling until the bug is fixed.
+    #[ignore]
     #[test]
     fn loom_broadcast_spurious() {
         const DEFAULT_PREEMPTION_BOUND: usize = 3;

asynchronix/src/ports/output/sender.rs

@@ -4,6 +4,7 @@ use std::future::Future;
 use std::marker::PhantomData;
 use std::mem::ManuallyDrop;
 use std::pin::Pin;
+use std::sync::Arc;
 use std::task::{Context, Poll};
 
 use dyn_clone::DynClone;
@@ -17,17 +18,15 @@ use crate::ports::{EventSinkWriter, InputFn, ReplierFn};
 /// replier method.
 pub(super) trait Sender<T, R>: DynClone + Send {
     /// Asynchronously send the event or request.
-    fn send(&mut self, arg: T) -> RecycledFuture<'_, Result<R, SendError>>;
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<R, SendError>>>;
 }
 
 dyn_clone::clone_trait_object!(<T, R> Sender<T, R>);
 
 /// An object that can send events to an input port.
-pub(super) struct InputSender<M: 'static, F, T, S>
+pub(super) struct InputSender<M, F, T, S>
 where
-    M: Model,
+    M: 'static,
-    F: for<'a> InputFn<'a, M, T, S>,
-    T: Send + 'static,
 {
     func: F,
     sender: channel::Sender<M>,
@@ -36,11 +35,9 @@ where
     _phantom_closure_marker: PhantomData<S>,
 }
 
-impl<M: Send, F, T, S> InputSender<M, F, T, S>
+impl<M, F, T, S> InputSender<M, F, T, S>
 where
-    M: Model,
+    M: 'static,
-    F: for<'a> InputFn<'a, M, T, S>,
-    T: Send + 'static,
 {
     pub(super) fn new(func: F, sender: channel::Sender<M>) -> Self {
         Self {
@@ -53,14 +50,14 @@ where
     }
 }
 
-impl<M: Send, F, T, S> Sender<T, ()> for InputSender<M, F, T, S>
+impl<M, F, T, S> Sender<T, ()> for InputSender<M, F, T, S>
 where
     M: Model,
     F: for<'a> InputFn<'a, M, T, S> + Clone,
     T: Send + 'static,
-    S: Send + 'static,
+    S: Send,
 {
-    fn send(&mut self, arg: T) -> RecycledFuture<'_, Result<(), SendError>> {
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<(), SendError>>> {
         let func = self.func.clone();
 
         let fut = self.sender.send(move |model, scheduler, recycle_box| {
@@ -69,18 +66,16 @@ where
             coerce_box!(RecycleBox::recycle(recycle_box, fut))
         });
 
-        RecycledFuture::new(&mut self.fut_storage, async move {
+        Some(RecycledFuture::new(&mut self.fut_storage, async move {
             fut.await.map_err(|_| SendError {})
-        })
+        }))
     }
 }
 
-impl<M: Send, F, T, S> Clone for InputSender<M, F, T, S>
+impl<M, F, T, S> Clone for InputSender<M, F, T, S>
 where
-    M: Model,
+    M: 'static,
-    F: for<'a> InputFn<'a, M, T, S> + Clone,
+    F: Clone,
-    T: Send + 'static,
-    S: Send + 'static,
 {
     fn clone(&self) -> Self {
         Self {
@@ -93,8 +88,322 @@ where
     }
 }
 
-/// An object that can send a request to a replier port and retrieve a response.
+/// An object that can send mapped events to an input port.
-pub(super) struct ReplierSender<M: 'static, F, T, R, S> {
+pub(super) struct MapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    map: Arc<C>,
+    func: F,
+    sender: channel::Sender<M>,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_map: PhantomData<fn(T) -> U>,
+    _phantom_closure: PhantomData<fn(&mut M, U)>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, F, T, U, S> MapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    pub(super) fn new(map: C, func: F, sender: channel::Sender<M>) -> Self {
+        Self {
+            map: Arc::new(map),
+            func,
+            sender,
+            fut_storage: None,
+            _phantom_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, F, T, U, S> Sender<T, ()> for MapInputSender<M, C, F, T, U, S>
+where
+    M: Model,
+    C: Fn(T) -> U + Send + Sync,
+    F: for<'a> InputFn<'a, M, U, S> + Clone,
+    T: Send + 'static,
+    U: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<(), SendError>>> {
+        let func = self.func.clone();
+        let arg = (self.map)(arg);
+
+        let fut = self.sender.send(move |model, scheduler, recycle_box| {
+            let fut = func.call(model, arg, scheduler);
+
+            coerce_box!(RecycleBox::recycle(recycle_box, fut))
+        });
+
+        Some(RecycledFuture::new(&mut self.fut_storage, async move {
+            fut.await.map_err(|_| SendError {})
+        }))
+    }
+}
+
+impl<M, C, F, T, U, S> Clone for MapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+    F: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            map: self.map.clone(),
+            func: self.func.clone(),
+            sender: self.sender.clone(),
+            fut_storage: None,
+            _phantom_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+/// An object that can filter and send mapped events to an input port.
+pub(super) struct FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    filter_map: Arc<C>,
+    func: F,
+    sender: channel::Sender<M>,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_filter_map: PhantomData<fn(T) -> Option<U>>,
+    _phantom_closure: PhantomData<fn(&mut M, U)>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, F, T, U, S> FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    pub(super) fn new(filter_map: C, func: F, sender: channel::Sender<M>) -> Self {
+        Self {
+            filter_map: Arc::new(filter_map),
+            func,
+            sender,
+            fut_storage: None,
+            _phantom_filter_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, F, T, U, S> Sender<T, ()> for FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: Model,
+    C: Fn(T) -> Option<U> + Send + Sync,
+    F: for<'a> InputFn<'a, M, U, S> + Clone,
+    T: Send + 'static,
+    U: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<(), SendError>>> {
+        (self.filter_map)(arg).map(|arg| {
+            let func = self.func.clone();
+
+            let fut = self.sender.send(move |model, scheduler, recycle_box| {
+                let fut = func.call(model, arg, scheduler);
+
+                coerce_box!(RecycleBox::recycle(recycle_box, fut))
+            });
+
+            RecycledFuture::new(&mut self.fut_storage, async move {
+                fut.await.map_err(|_| SendError {})
+            })
+        })
+    }
+}
+
+impl<M, C, F, T, U, S> Clone for FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+    F: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            filter_map: self.filter_map.clone(),
+            func: self.func.clone(),
+            sender: self.sender.clone(),
+            fut_storage: None,
+            _phantom_filter_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+/// An object that can send an event to an event sink.
+pub(super) struct EventSinkSender<T, W> {
+    writer: W,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_event: PhantomData<T>,
+}
+
+impl<T, W> EventSinkSender<T, W> {
+    pub(super) fn new(writer: W) -> Self {
+        Self {
+            writer,
+            fut_storage: None,
+            _phantom_event: PhantomData,
+        }
+    }
+}
+
+impl<T, W> Sender<T, ()> for EventSinkSender<T, W>
+where
+    T: Send + 'static,
+    W: EventSinkWriter<T>,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<(), SendError>>> {
+        let writer = &mut self.writer;
+
+        Some(RecycledFuture::new(&mut self.fut_storage, async move {
+            writer.write(arg);
+
+            Ok(())
+        }))
+    }
+}
+
+impl<T, W: Clone> Clone for EventSinkSender<T, W> {
+    fn clone(&self) -> Self {
+        Self {
+            writer: self.writer.clone(),
+            fut_storage: None,
+            _phantom_event: PhantomData,
+        }
+    }
+}
+
+/// An object that can send mapped events to an event sink.
+pub(super) struct MapEventSinkSender<T, U, W, C>
+where
+    C: Fn(T) -> U,
+{
+    writer: W,
+    map: Arc<C>,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_event: PhantomData<T>,
+}
+
+impl<T, U, W, C> MapEventSinkSender<T, U, W, C>
+where
+    C: Fn(T) -> U,
+{
+    pub(super) fn new(map: C, writer: W) -> Self {
+        Self {
+            writer,
+            map: Arc::new(map),
+            fut_storage: None,
+            _phantom_event: PhantomData,
+        }
+    }
+}
+
+impl<T, U, W, C> Sender<T, ()> for MapEventSinkSender<T, U, W, C>
+where
+    T: Send + 'static,
+    U: Send + 'static,
+    C: Fn(T) -> U + Send + Sync,
+    W: EventSinkWriter<U>,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<(), SendError>>> {
+        let writer = &mut self.writer;
+        let arg = (self.map)(arg);
+
+        Some(RecycledFuture::new(&mut self.fut_storage, async move {
+            writer.write(arg);
+
+            Ok(())
+        }))
+    }
+}
+
+impl<T, U, W, C> Clone for MapEventSinkSender<T, U, W, C>
+where
+    C: Fn(T) -> U,
+    W: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            writer: self.writer.clone(),
+            map: self.map.clone(),
+            fut_storage: None,
+            _phantom_event: PhantomData,
+        }
+    }
+}
+
+/// An object that can filter and send mapped events to an event sink.
+pub(super) struct FilterMapEventSinkSender<T, U, W, C>
+where
+    C: Fn(T) -> Option<U>,
+{
+    writer: W,
+    filter_map: Arc<C>,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_event: PhantomData<T>,
+}
+
+impl<T, U, W, C> FilterMapEventSinkSender<T, U, W, C>
+where
+    C: Fn(T) -> Option<U>,
+{
+    pub(super) fn new(filter_map: C, writer: W) -> Self {
+        Self {
+            writer,
+            filter_map: Arc::new(filter_map),
+            fut_storage: None,
+            _phantom_event: PhantomData,
+        }
+    }
+}
+
+impl<T, U, W, C> Sender<T, ()> for FilterMapEventSinkSender<T, U, W, C>
+where
+    T: Send + 'static,
+    U: Send + 'static,
+    C: Fn(T) -> Option<U> + Send + Sync,
+    W: EventSinkWriter<U>,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<(), SendError>>> {
+        let writer = &mut self.writer;
+
+        (self.filter_map)(arg).map(|arg| {
+            RecycledFuture::new(&mut self.fut_storage, async move {
+                writer.write(arg);
+
+                Ok(())
+            })
+        })
+    }
+}
+
+impl<T, U, W, C> Clone for FilterMapEventSinkSender<T, U, W, C>
+where
+    C: Fn(T) -> Option<U>,
+    W: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            writer: self.writer.clone(),
+            filter_map: self.filter_map.clone(),
+            fut_storage: None,
+            _phantom_event: PhantomData,
+        }
+    }
+}
+
+/// An object that can send requests to a replier port and retrieve responses.
+pub(super) struct ReplierSender<M, F, T, R, S>
+where
+    M: Model,
+{
     func: F,
     sender: channel::Sender<M>,
     receiver: multishot::Receiver<R>,
@@ -106,9 +415,6 @@ pub(super) struct ReplierSender<M: 'static, F, T, R, S> {
 impl<M, F, T, R, S> ReplierSender<M, F, T, R, S>
 where
     M: Model,
-    F: for<'a> ReplierFn<'a, M, T, R, S>,
-    T: Send + 'static,
-    R: Send + 'static,
 {
     pub(super) fn new(func: F, sender: channel::Sender<M>) -> Self {
         Self {
@@ -130,7 +436,7 @@ where
     R: Send + 'static,
     S: Send,
 {
-    fn send(&mut self, arg: T) -> RecycledFuture<'_, Result<R, SendError>> {
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<R, SendError>>> {
         let func = self.func.clone();
         let sender = &mut self.sender;
         let reply_receiver = &mut self.receiver;
@@ -149,6 +455,219 @@ where
             coerce_box!(RecycleBox::recycle(recycle_box, fut))
         });
 
+        Some(RecycledFuture::new(fut_storage, async move {
+            // Send the message.
+            send_fut.await.map_err(|_| SendError {})?;
+
+            // Wait until the message is processed and the reply is sent back.
+            // If an error is received, it most likely means the mailbox was
+            // dropped before the message was processed.
+            reply_receiver.recv().await.map_err(|_| SendError {})
+        }))
+    }
+}
+
+impl<M, F, T, R, S> Clone for ReplierSender<M, F, T, R, S>
+where
+    M: Model,
+    F: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            func: self.func.clone(),
+            sender: self.sender.clone(),
+            receiver: multishot::Receiver::new(),
+            fut_storage: None,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+/// An object that can send mapped requests to a replier port and retrieve
+/// mapped responses.
+pub(super) struct MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+{
+    query_map: Arc<C>,
+    reply_map: Arc<D>,
+    func: F,
+    sender: channel::Sender<M>,
+    receiver: multishot::Receiver<Q>,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_query_map: PhantomData<fn(T) -> U>,
+    _phantom_reply_map: PhantomData<fn(Q) -> R>,
+    _phantom_closure: PhantomData<fn(&mut M, U) -> Q>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, D, F, T, R, U, Q, S> MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+{
+    pub(super) fn new(query_map: C, reply_map: D, func: F, sender: channel::Sender<M>) -> Self {
+        Self {
+            query_map: Arc::new(query_map),
+            reply_map: Arc::new(reply_map),
+            func,
+            sender,
+            receiver: multishot::Receiver::new(),
+            fut_storage: None,
+            _phantom_query_map: PhantomData,
+            _phantom_reply_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, D, F, T, R, U, Q, S> Sender<T, R> for MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+    C: Fn(T) -> U + Send + Sync,
+    D: Fn(Q) -> R + Send + Sync,
+    F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+    T: Send + 'static,
+    R: Send + 'static,
+    U: Send + 'static,
+    Q: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<R, SendError>>> {
+        let func = self.func.clone();
+        let arg = (self.query_map)(arg);
+        let sender = &mut self.sender;
+        let reply_receiver = &mut self.receiver;
+        let fut_storage = &mut self.fut_storage;
+        let reply_map = &*self.reply_map;
+
+        // The previous future generated by this method should have been polled
+        // to completion so a new sender should be readily available.
+        let reply_sender = reply_receiver.sender().unwrap();
+
+        let send_fut = sender.send(move |model, scheduler, recycle_box| {
+            let fut = async move {
+                let reply = func.call(model, arg, scheduler).await;
+                reply_sender.send(reply);
+            };
+
+            coerce_box!(RecycleBox::recycle(recycle_box, fut))
+        });
+
+        Some(RecycledFuture::new(fut_storage, async move {
+            // Send the message.
+            send_fut.await.map_err(|_| SendError {})?;
+
+            // Wait until the message is processed and the reply is sent back.
+            // If an error is received, it most likely means the mailbox was
+            // dropped before the message was processed.
+            reply_receiver
+                .recv()
+                .await
+                .map_err(|_| SendError {})
+                .map(reply_map)
+        }))
+    }
+}
+
+impl<M, C, D, F, T, R, U, Q, S> Clone for MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+    F: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            query_map: self.query_map.clone(),
+            reply_map: self.reply_map.clone(),
+            func: self.func.clone(),
+            sender: self.sender.clone(),
+            receiver: multishot::Receiver::new(),
+            fut_storage: None,
+            _phantom_query_map: PhantomData,
+            _phantom_reply_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+/// An object that can filter and send mapped requests to a replier port and
+/// retrieve mapped responses.
+pub(super) struct FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+{
+    query_filter_map: Arc<C>,
+    reply_map: Arc<D>,
+    func: F,
+    sender: channel::Sender<M>,
+    receiver: multishot::Receiver<Q>,
+    fut_storage: Option<RecycleBox<()>>,
+    _phantom_query_map: PhantomData<fn(T) -> U>,
+    _phantom_reply_map: PhantomData<fn(Q) -> R>,
+    _phantom_closure: PhantomData<fn(&mut M, U) -> Q>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, D, F, T, R, U, Q, S> FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+{
+    pub(super) fn new(
+        query_filter_map: C,
+        reply_map: D,
+        func: F,
+        sender: channel::Sender<M>,
+    ) -> Self {
+        Self {
+            query_filter_map: Arc::new(query_filter_map),
+            reply_map: Arc::new(reply_map),
+            func,
+            sender,
+            receiver: multishot::Receiver::new(),
+            fut_storage: None,
+            _phantom_query_map: PhantomData,
+            _phantom_reply_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, D, F, T, R, U, Q, S> Sender<T, R> for FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+    C: Fn(T) -> Option<U> + Send + Sync,
+    D: Fn(Q) -> R + Send + Sync,
+    F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+    T: Send + 'static,
+    R: Send + 'static,
+    U: Send + 'static,
+    Q: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<RecycledFuture<'_, Result<R, SendError>>> {
+        (self.query_filter_map)(arg).map(|arg| {
+            let func = self.func.clone();
+            let sender = &mut self.sender;
+            let reply_receiver = &mut self.receiver;
+            let fut_storage = &mut self.fut_storage;
+            let reply_map = &*self.reply_map;
+
+            // The previous future generated by this method should have been polled
+            // to completion so a new sender should be readily available.
+            let reply_sender = reply_receiver.sender().unwrap();
+
+            let send_fut = sender.send(move |model, scheduler, recycle_box| {
+                let fut = async move {
+                    let reply = func.call(model, arg, scheduler).await;
+                    reply_sender.send(reply);
+                };
+
+                coerce_box!(RecycleBox::recycle(recycle_box, fut))
+            });
+
             RecycledFuture::new(fut_storage, async move {
                 // Send the message.
                 send_fut.await.map_err(|_| SendError {})?;
@@ -156,78 +675,37 @@ where
                 // Wait until the message is processed and the reply is sent back.
                 // If an error is received, it most likely means the mailbox was
                 // dropped before the message was processed.
-            reply_receiver.recv().await.map_err(|_| SendError {})
+                reply_receiver
+                    .recv()
+                    .await
+                    .map_err(|_| SendError {})
+                    .map(reply_map)
+            })
         })
     }
 }
 
-impl<M, F, T, R, S> Clone for ReplierSender<M, F, T, R, S>
+impl<M, C, D, F, T, R, U, Q, S> Clone for FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
 where
     M: Model,
-    F: for<'a> ReplierFn<'a, M, T, R, S> + Clone,
+    F: Clone,
-    T: Send + 'static,
-    R: Send + 'static,
-    S: Send,
 {
     fn clone(&self) -> Self {
         Self {
+            query_filter_map: self.query_filter_map.clone(),
+            reply_map: self.reply_map.clone(),
             func: self.func.clone(),
             sender: self.sender.clone(),
             receiver: multishot::Receiver::new(),
             fut_storage: None,
+            _phantom_query_map: PhantomData,
+            _phantom_reply_map: PhantomData,
             _phantom_closure: PhantomData,
             _phantom_closure_marker: PhantomData,
         }
     }
 }
 
-/// An object that can send a payload to an event sink.
-pub(super) struct EventSinkSender<T: Send + 'static, W: EventSinkWriter<T>> {
-    writer: W,
-    fut_storage: Option<RecycleBox<()>>,
-    _phantom_event: PhantomData<T>,
-}
-
-impl<T: Send + 'static, W: EventSinkWriter<T>> EventSinkSender<T, W> {
-    pub(super) fn new(writer: W) -> Self {
-        Self {
-            writer,
-            fut_storage: None,
-            _phantom_event: PhantomData,
-        }
-    }
-}
-
-impl<T, W> Sender<T, ()> for EventSinkSender<T, W>
-where
-    T: Send + 'static,
-    W: EventSinkWriter<T>,
-{
-    fn send(&mut self, arg: T) -> RecycledFuture<'_, Result<(), SendError>> {
-        let writer = &mut self.writer;
-
-        RecycledFuture::new(&mut self.fut_storage, async move {
-            writer.write(arg);
-
-            Ok(())
-        })
-    }
-}
-
-impl<T, W> Clone for EventSinkSender<T, W>
-where
-    T: Send + 'static,
-    W: EventSinkWriter<T>,
-{
-    fn clone(&self) -> Self {
-        Self {
-            writer: self.writer.clone(),
-            fut_storage: None,
-            _phantom_event: PhantomData,
-        }
-    }
-}
-
 /// Error returned when the mailbox was closed or dropped.
 #[derive(Debug, PartialEq, Eq, Clone, Copy)]
 pub(super) struct SendError {}

asynchronix/src/ports/source.rs

@@ -13,9 +13,11 @@ use crate::simulation::{
 };
 use crate::util::slot;
 
-use broadcaster::ReplyIterator;
+use broadcaster::{EventBroadcaster, QueryBroadcaster, ReplyIterator};
-use broadcaster::{EventBroadcaster, QueryBroadcaster};
+use sender::{
-use sender::{InputSender, ReplierSender};
+    FilterMapInputSender, FilterMapReplierSender, InputSender, MapInputSender, MapReplierSender,
+    ReplierSender,
+};
 
 use super::ReplierFn;
 
@@ -51,6 +53,58 @@ impl<T: Clone + Send + 'static> EventSource<T> {
         self.broadcaster.lock().unwrap().add(sender)
     }
 
+    /// Adds an auto-converting connection to an input port of the model
+    /// specified by the address.
+    ///
+    /// Events are mapped to another type using the closure provided in
+    /// argument.
+    ///
+    /// The input port must be an asynchronous method of a model of type `M`
+    /// taking as argument a value of the type returned by the mapping closure
+    /// plus, optionally, a context reference.
+    pub fn map_connect<M, C, F, U, S>(
+        &mut self,
+        map: C,
+        input: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> U + Send + 'static,
+        F: for<'a> InputFn<'a, M, U, S> + Clone,
+        U: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(MapInputSender::new(map, input, address.into().0));
+        self.broadcaster.lock().unwrap().add(sender)
+    }
+
+    /// Adds an auto-converting, filtered connection to an input port of the
+    /// model specified by the address.
+    ///
+    /// Events are mapped to another type using the closure provided in
+    /// argument, or ignored if the closure returns `None`.
+    ///
+    /// The input port must be an asynchronous method of a model of type `M`
+    /// taking as argument a value of the type returned by the mapping closure
+    /// plus, optionally, a context reference.
+    pub fn filter_map_connect<M, C, F, U, S>(
+        &mut self,
+        map: C,
+        input: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> Option<U> + Send + 'static,
+        F: for<'a> InputFn<'a, M, U, S> + Clone,
+        U: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(FilterMapInputSender::new(map, input, address.into().0));
+        self.broadcaster.lock().unwrap().add(sender)
+    }
+
     /// Removes the connection specified by the `LineId` parameter.
     ///
     /// It is a logic error to specify a line identifier from another
@@ -193,7 +247,7 @@ impl<T: Clone + Send + 'static, R: Send + 'static> QuerySource<T, R> {
     ///
     /// The replier port must be an asynchronous method of a model of type `M`
     /// returning a value of type `R` and taking as argument a value of type `T`
-    /// plus, optionally, a scheduler reference.
+    /// plus, optionally, a context reference.
     pub fn connect<M, F, S>(&mut self, replier: F, address: impl Into<Address<M>>) -> LineId
     where
         M: Model,
@@ -204,6 +258,76 @@ impl<T: Clone + Send + 'static, R: Send + 'static> QuerySource<T, R> {
         self.broadcaster.lock().unwrap().add(sender)
     }
 
+    /// Adds an auto-converting connection to a replier port of the model
+    /// specified by the address.
+    ///
+    /// Queries and replies are mapped to other types using the closures
+    /// provided in argument.
+    ///
+    /// The replier port must be an asynchronous method of a model of type `M`
+    /// returning a value of the type returned by the reply mapping closure and
+    /// taking as argument a value of the type returned by the query mapping
+    /// closure plus, optionally, a context reference.
+    pub fn map_connect<M, C, D, F, U, Q, S>(
+        &mut self,
+        query_map: C,
+        reply_map: D,
+        replier: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> U + Send + 'static,
+        D: Fn(Q) -> R + Send + Sync + 'static,
+        F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+        U: Send + 'static,
+        Q: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(MapReplierSender::new(
+            query_map,
+            reply_map,
+            replier,
+            address.into().0,
+        ));
+        self.broadcaster.lock().unwrap().add(sender)
+    }
+
+    /// Adds an auto-converting, filtered connection to a replier port of the
+    /// model specified by the address.
+    ///
+    /// Queries and replies are mapped to other types using the closures
+    /// provided in argument, or ignored if the query closure returns `None`.
+    ///
+    /// The replier port must be an asynchronous method of a model of type `M`
+    /// returning a value of the type returned by the reply mapping closure and
+    /// taking as argument a value of the type returned by the query mapping
+    /// closure plus, optionally, a context reference.
+    pub fn filter_map_connect<M, C, D, F, U, Q, S>(
+        &mut self,
+        query_filter_map: C,
+        reply_map: D,
+        replier: F,
+        address: impl Into<Address<M>>,
+    ) -> LineId
+    where
+        M: Model,
+        C: Fn(T) -> Option<U> + Send + 'static,
+        D: Fn(Q) -> R + Send + Sync + 'static,
+        F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+        U: Send + 'static,
+        Q: Send + 'static,
+        S: Send + 'static,
+    {
+        let sender = Box::new(FilterMapReplierSender::new(
+            query_filter_map,
+            reply_map,
+            replier,
+            address.into().0,
+        ));
+        self.broadcaster.lock().unwrap().add(sender)
+    }
+
     /// Removes the connection specified by the `LineId` parameter.
     ///
     /// It is a logic error to specify a line identifier from another

asynchronix/src/ports/source/broadcaster.rs

@@ -71,26 +71,27 @@ impl<T: Clone, R> BroadcasterInner<T, R> {
         self.senders.len()
     }
 
-    /// Efficiently broadcasts a message or a query to multiple addresses.
+    /// Return a list of futures broadcasting an event or query to multiple
-    ///
+    /// addresses.
-    /// This method does not collect the responses from queries.
+    fn futures(&mut self, arg: T) -> Vec<SenderFutureState<R>> {
-    fn broadcast(&mut self, arg: T) -> BroadcastFuture<R> {
+        let mut future_states = Vec::new();
-        let mut future_states = Vec::with_capacity(self.senders.len());
 
         // Broadcast the message and collect all futures.
         let mut iter = self.senders.iter_mut();
         while let Some(sender) = iter.next() {
             // Move the argument rather than clone it for the last future.
             if iter.len() == 0 {
-                future_states.push(SenderFutureState::Pending(sender.1.send(arg)));
+                if let Some(fut) = sender.1.send(arg) {
+                    future_states.push(SenderFutureState::Pending(fut));
+                }
                 break;
             }
-
+            if let Some(fut) = sender.1.send(arg.clone()) {
-            future_states.push(SenderFutureState::Pending(sender.1.send(arg.clone())));
+                future_states.push(SenderFutureState::Pending(fut));
+            }
         }
 
-        // Generate the global future.
+        future_states
-        BroadcastFuture::new(future_states)
     }
 }
 
@@ -157,17 +158,27 @@ impl<T: Clone + Send> EventBroadcaster<T> {
         let fut = match self.inner.senders.as_mut_slice() {
             // No sender.
             [] => Fut::Empty,
-            // One sender.
+            // One sender at most.
             [sender] => Fut::Single(sender.1.send(arg)),
-            // Multiple senders.
+            // Possibly multiple senders.
-            _ => Fut::Multiple(self.inner.broadcast(arg)),
+            _ => Fut::Multiple(self.inner.futures(arg)),
         };
 
         async {
             match fut {
-                Fut::Empty => Ok(()),
+                // No sender.
-                Fut::Single(fut) => fut.await.map_err(|_| BroadcastError {}),
+                Fut::Empty | Fut::Single(None) => Ok(()),
-                Fut::Multiple(fut) => fut.await.map(|_| ()),
+
+                Fut::Single(Some(fut)) => fut.await.map_err(|_| BroadcastError {}),
+
+                Fut::Multiple(mut futures) => match futures.as_mut_slice() {
+                    // No sender.
+                    [] => Ok(()),
+                    // One sender.
+                    [SenderFutureState::Pending(fut)] => fut.await.map_err(|_| BroadcastError {}),
+                    // Multiple senders.
+                    _ => BroadcastFuture::new(futures).await.map(|_| ()),
+                },
             }
         }
     }
@@ -235,20 +246,39 @@ impl<T: Clone + Send, R: Send> QueryBroadcaster<T, R> {
         let fut = match self.inner.senders.as_mut_slice() {
             // No sender.
             [] => Fut::Empty,
-            // One sender.
+            // One sender at most.
             [sender] => Fut::Single(sender.1.send(arg)),
-            // Multiple senders.
+            // Possibly multiple senders.
-            _ => Fut::Multiple(self.inner.broadcast(arg)),
+            _ => Fut::Multiple(self.inner.futures(arg)),
         };
 
         async {
             match fut {
-                Fut::Empty => Ok(ReplyIterator(Vec::new().into_iter())),
+                // No sender.
-                Fut::Single(fut) => fut
+                Fut::Empty | Fut::Single(None) => Ok(ReplyIterator(Vec::new().into_iter())),
+
+                Fut::Single(Some(fut)) => fut
                     .await
                     .map(|reply| ReplyIterator(vec![SenderFutureState::Ready(reply)].into_iter()))
                     .map_err(|_| BroadcastError {}),
-                Fut::Multiple(fut) => fut.await.map_err(|_| BroadcastError {}),
+
+                Fut::Multiple(mut futures) => match futures.as_mut_slice() {
+                    // No sender.
+                    [] => Ok(ReplyIterator(Vec::new().into_iter())),
+
+                    // One sender.
+                    [SenderFutureState::Pending(fut)] => fut
+                        .await
+                        .map(|reply| {
+                            ReplyIterator(vec![SenderFutureState::Ready(reply)].into_iter())
+                        })
+                        .map_err(|_| BroadcastError {}),
+
+                    // Multiple senders.
+                    _ => BroadcastFuture::new(futures)
+                        .await
+                        .map_err(|_| BroadcastError {}),
+                },
             }
         }
     }
@@ -598,14 +628,17 @@ mod tests {
         receiver: Option<mpsc::UnboundedReceiver<Option<R>>>,
     }
     impl<R: Send + 'static> Sender<(), R> for TestEvent<R> {
-        fn send(&mut self, _arg: ()) -> Pin<Box<dyn Future<Output = Result<R, SendError>> + Send>> {
+        fn send(
+            &mut self,
+            _arg: (),
+        ) -> Option<Pin<Box<dyn Future<Output = Result<R, SendError>> + Send>>> {
             let receiver = self.receiver.take().unwrap();
 
-            Box::pin(async move {
+            Some(Box::pin(async move {
                 let mut stream = Box::pin(receiver.filter_map(|item| async { item }));
 
                 Ok(stream.next().await.unwrap())
-            })
+            }))
         }
     }
 
@@ -634,8 +667,16 @@ mod tests {
         )
     }
 
+    // This tests fails with "Concurrent load and mut accesses" even though the
+    // `task_list` implementation which triggers it does not use any unsafe.
+    // This is most certainly related to this Loom bug:
+    //
+    // https://github.com/tokio-rs/loom/issues/260
+    //
+    // Disabling until the bug is fixed.
+    #[ignore]
     #[test]
-    fn loom_broadcast_basic() {
+    fn loom_broadcast_query_basic() {
         const DEFAULT_PREEMPTION_BOUND: usize = 3;
 
         let mut builder = Builder::new();
@@ -707,8 +748,16 @@ mod tests {
         });
     }
 
+    // This tests fails with "Concurrent load and mut accesses" even though the
+    // `task_list` implementation which triggers it does not use any unsafe.
+    // This is most certainly related to this Loom bug:
+    //
+    // https://github.com/tokio-rs/loom/issues/260
+    //
+    // Disabling until the bug is fixed.
+    #[ignore]
     #[test]
-    fn loom_broadcast_spurious() {
+    fn loom_broadcast_query_spurious() {
         const DEFAULT_PREEMPTION_BOUND: usize = 3;
 
         let mut builder = Builder::new();

asynchronix/src/ports/source/sender.rs

@@ -3,6 +3,7 @@ use std::fmt;
 use std::future::Future;
 use std::marker::PhantomData;
 use std::pin::Pin;
+use std::sync::Arc;
 
 use futures_channel::oneshot;
 use recycle_box::{coerce_box, RecycleBox};
@@ -16,22 +17,23 @@ pub(super) type SenderFuture<R> = Pin<Box<dyn Future<Output = Result<R, SendErro
 /// An event or query sender abstracting over the target model and input method.
 pub(super) trait Sender<T, R>: Send {
     /// Asynchronously send the event or request.
-    fn send(&mut self, arg: T) -> SenderFuture<R>;
+    fn send(&mut self, arg: T) -> Option<SenderFuture<R>>;
 }
 
 /// An object that can send events to an input port.
-pub(super) struct InputSender<M: 'static, F, T, S> {
+pub(super) struct InputSender<M, F, T, S>
+where
+    M: 'static,
+{
     func: F,
     sender: channel::Sender<M>,
     _phantom_closure: PhantomData<fn(&mut M, T)>,
     _phantom_closure_marker: PhantomData<S>,
 }
 
-impl<M: Send, F, T, S> InputSender<M, F, T, S>
+impl<M, F, T, S> InputSender<M, F, T, S>
 where
-    M: Model,
+    M: 'static,
-    F: for<'a> InputFn<'a, M, T, S>,
-    T: Send + 'static,
 {
     pub(super) fn new(func: F, sender: channel::Sender<M>) -> Self {
         Self {
@@ -43,14 +45,126 @@ where
     }
 }
 
-impl<M: Send, F, T, S> Sender<T, ()> for InputSender<M, F, T, S>
+impl<M, F, T, S> Sender<T, ()> for InputSender<M, F, T, S>
 where
     M: Model,
     F: for<'a> InputFn<'a, M, T, S> + Clone,
     T: Send + 'static,
-    S: Send + 'static,
+    S: Send,
 {
-    fn send(&mut self, arg: T) -> SenderFuture<()> {
+    fn send(&mut self, arg: T) -> Option<SenderFuture<()>> {
+        let func = self.func.clone();
+        let sender = self.sender.clone();
+
+        Some(Box::pin(async move {
+            sender
+                .send(move |model, scheduler, recycle_box| {
+                    let fut = func.call(model, arg, scheduler);
+
+                    coerce_box!(RecycleBox::recycle(recycle_box, fut))
+                })
+                .await
+                .map_err(|_| SendError {})
+        }))
+    }
+}
+
+/// An object that can send mapped events to an input port.
+pub(super) struct MapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    map: C,
+    func: F,
+    sender: channel::Sender<M>,
+    _phantom_map: PhantomData<fn(T) -> U>,
+    _phantom_closure: PhantomData<fn(&mut M, T)>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, F, T, U, S> MapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    pub(super) fn new(map: C, func: F, sender: channel::Sender<M>) -> Self {
+        Self {
+            map,
+            func,
+            sender,
+            _phantom_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, F, T, U, S> Sender<T, ()> for MapInputSender<M, C, F, T, U, S>
+where
+    M: Model,
+    C: Fn(T) -> U + Send,
+    F: for<'a> InputFn<'a, M, U, S> + Clone,
+    T: Send + 'static,
+    U: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<SenderFuture<()>> {
+        let func = self.func.clone();
+        let arg = (self.map)(arg);
+        let sender = self.sender.clone();
+
+        Some(Box::pin(async move {
+            sender
+                .send(move |model, scheduler, recycle_box| {
+                    let fut = func.call(model, arg, scheduler);
+
+                    coerce_box!(RecycleBox::recycle(recycle_box, fut))
+                })
+                .await
+                .map_err(|_| SendError {})
+        }))
+    }
+}
+
+/// An object that can filter and send mapped events to an input port.
+pub(super) struct FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    filter_map: C,
+    func: F,
+    sender: channel::Sender<M>,
+    _phantom_map: PhantomData<fn(T) -> U>,
+    _phantom_closure: PhantomData<fn(&mut M, T)>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, F, T, U, S> FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: 'static,
+{
+    pub(super) fn new(filter_map: C, func: F, sender: channel::Sender<M>) -> Self {
+        Self {
+            filter_map,
+            func,
+            sender,
+            _phantom_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, F, T, U, S> Sender<T, ()> for FilterMapInputSender<M, C, F, T, U, S>
+where
+    M: Model,
+    C: Fn(T) -> Option<U> + Send,
+    F: for<'a> InputFn<'a, M, U, S> + Clone,
+    T: Send + 'static,
+    U: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<SenderFuture<()>> {
+        (self.filter_map)(arg).map(|arg| {
             let func = self.func.clone();
             let sender = self.sender.clone();
 
@@ -63,12 +177,16 @@ where
                     })
                     .await
                     .map_err(|_| SendError {})
+            }) as SenderFuture<()>
         })
     }
 }
 
 /// An object that can send a request to a replier port and retrieve a response.
-pub(super) struct ReplierSender<M: 'static, F, T, R, S> {
+pub(super) struct ReplierSender<M, F, T, R, S>
+where
+    M: 'static,
+{
     func: F,
     sender: channel::Sender<M>,
     _phantom_closure: PhantomData<fn(&mut M, T) -> R>,
@@ -77,10 +195,7 @@ pub(super) struct ReplierSender<M: 'static, F, T, R, S> {
 
 impl<M, F, T, R, S> ReplierSender<M, F, T, R, S>
 where
-    M: Model,
+    M: 'static,
-    F: for<'a> ReplierFn<'a, M, T, R, S>,
-    T: Send + 'static,
-    R: Send + 'static,
 {
     pub(super) fn new(func: F, sender: channel::Sender<M>) -> Self {
         Self {
@@ -100,11 +215,161 @@ where
     R: Send + 'static,
     S: Send,
 {
-    fn send(&mut self, arg: T) -> SenderFuture<R> {
+    fn send(&mut self, arg: T) -> Option<SenderFuture<R>> {
         let func = self.func.clone();
         let sender = self.sender.clone();
         let (reply_sender, reply_receiver) = oneshot::channel();
 
+        Some(Box::pin(async move {
+            sender
+                .send(move |model, scheduler, recycle_box| {
+                    let fut = async move {
+                        let reply = func.call(model, arg, scheduler).await;
+                        let _ = reply_sender.send(reply);
+                    };
+
+                    coerce_box!(RecycleBox::recycle(recycle_box, fut))
+                })
+                .await
+                .map_err(|_| SendError {})?;
+
+            reply_receiver.await.map_err(|_| SendError {})
+        }))
+    }
+}
+
+/// An object that can send a mapped request to a replier port and retrieve a
+/// mapped response.
+pub(super) struct MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: 'static,
+{
+    query_map: C,
+    reply_map: Arc<D>,
+    func: F,
+    sender: channel::Sender<M>,
+    _phantom_query_map: PhantomData<fn(T) -> U>,
+    _phantom_reply_map: PhantomData<fn(Q) -> R>,
+    _phantom_closure: PhantomData<fn(&mut M, U) -> Q>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, D, F, T, R, U, Q, S> MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: 'static,
+{
+    pub(super) fn new(query_map: C, reply_map: D, func: F, sender: channel::Sender<M>) -> Self {
+        Self {
+            query_map,
+            reply_map: Arc::new(reply_map),
+            func,
+            sender,
+            _phantom_query_map: PhantomData,
+            _phantom_reply_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, D, F, T, R, U, Q, S> Sender<T, R> for MapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+    C: Fn(T) -> U + Send,
+    D: Fn(Q) -> R + Send + Sync + 'static,
+    F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+    T: Send + 'static,
+    R: Send + 'static,
+    U: Send + 'static,
+    Q: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<SenderFuture<R>> {
+        let func = self.func.clone();
+        let arg = (self.query_map)(arg);
+        let sender = self.sender.clone();
+        let reply_map = self.reply_map.clone();
+        let (reply_sender, reply_receiver) = oneshot::channel();
+
+        Some(Box::pin(async move {
+            sender
+                .send(move |model, scheduler, recycle_box| {
+                    let fut = async move {
+                        let reply = func.call(model, arg, scheduler).await;
+                        let _ = reply_sender.send(reply);
+                    };
+
+                    coerce_box!(RecycleBox::recycle(recycle_box, fut))
+                })
+                .await
+                .map_err(|_| SendError {})?;
+
+            reply_receiver
+                .await
+                .map_err(|_| SendError {})
+                .map(&*reply_map)
+        }))
+    }
+}
+
+/// An object that can filter and send a mapped request to a replier port and
+/// retrieve a mapped response.
+pub(super) struct FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: 'static,
+{
+    query_filter_map: C,
+    reply_map: Arc<D>,
+    func: F,
+    sender: channel::Sender<M>,
+    _phantom_query_map: PhantomData<fn(T) -> Option<U>>,
+    _phantom_reply_map: PhantomData<fn(Q) -> R>,
+    _phantom_closure: PhantomData<fn(&mut M, U) -> Q>,
+    _phantom_closure_marker: PhantomData<S>,
+}
+
+impl<M, C, D, F, T, R, U, Q, S> FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: 'static,
+{
+    pub(super) fn new(
+        query_filter_map: C,
+        reply_map: D,
+        func: F,
+        sender: channel::Sender<M>,
+    ) -> Self {
+        Self {
+            query_filter_map,
+            reply_map: Arc::new(reply_map),
+            func,
+            sender,
+            _phantom_query_map: PhantomData,
+            _phantom_reply_map: PhantomData,
+            _phantom_closure: PhantomData,
+            _phantom_closure_marker: PhantomData,
+        }
+    }
+}
+
+impl<M, C, D, F, T, R, U, Q, S> Sender<T, R> for FilterMapReplierSender<M, C, D, F, T, R, U, Q, S>
+where
+    M: Model,
+    C: Fn(T) -> Option<U> + Send,
+    D: Fn(Q) -> R + Send + Sync + 'static,
+    F: for<'a> ReplierFn<'a, M, U, Q, S> + Clone,
+    T: Send + 'static,
+    R: Send + 'static,
+    U: Send + 'static,
+    Q: Send + 'static,
+    S: Send,
+{
+    fn send(&mut self, arg: T) -> Option<SenderFuture<R>> {
+        (self.query_filter_map)(arg).map(|arg| {
+            let func = self.func.clone();
+            let sender = self.sender.clone();
+            let reply_map = self.reply_map.clone();
+            let (reply_sender, reply_receiver) = oneshot::channel();
+
             Box::pin(async move {
                 sender
                     .send(move |model, scheduler, recycle_box| {
@@ -118,7 +383,11 @@ where
                     .await
                     .map_err(|_| SendError {})?;
 
-            reply_receiver.await.map_err(|_| SendError {})
+                reply_receiver
+                    .await
+                    .map_err(|_| SendError {})
+                    .map(&*reply_map)
+            }) as SenderFuture<R>
         })
     }
 }

asynchronix/src/util/task_set.rs

@@ -196,60 +196,12 @@ impl TaskSet {
                     next: AtomicU32::new(SLEEPING),
                 }));
             }
-
-            return;
         }
 
-        // Try to shrink the vector of tasks.
+        // The vector of tasks is never shrunk as this is a fairly costly
-        //
+        // operation and is not strictly necessary. Typically, inactive tasks
-        // The main issue when shrinking the vector of tasks is that stale
+        // left at the back of the vector are never waken anyway, and if they
-        // wakers may still be around and may at any moment be scheduled and
+        // are, they are filtered out by the task iterator.
-        // insert their task index in the list of scheduled tasks. If it cannot
-        // be guaranteed that this will not happen, then the vector of tasks
-        // cannot be shrunk further, otherwise the iterator for scheduled tasks
-        // will later fail when reaching a task with an invalid index.
-        //
-        // We follow a 2-steps strategy:
-        //
-        // 1) remove all tasks currently in the list of scheduled task and set
-        // them to `SLEEPING` state in case some of them might have an index
-        // that will be invalidated when the vector of tasks is shrunk;
-        //
-        // 2) attempt to iteratively shrink the vector of tasks by removing
-        //    tasks starting from the back of the vector:
-        //   - If a task is in the `SLEEPING` state, then its `next` pointer is
-        //     changed to an arbitrary value other than`SLEEPING`, but the task
-        //     is not inserted in the list of scheduled tasks; this way, the
-        //     task will be effectively rendered inactive. The task can now be
-        //     removed from the vector.
-        //   - If a task is found in a non-`SLEEPING` state (meaning that there
-        //     was a race and the task was scheduled after step 1) then abandon
-        //     further shrinking and leave this task in the vector; the iterator
-        //     for scheduled tasks mitigates such situation by only yielding
-        //     task indices that are within the expected range.
-
-        // Step 1: unscheduled tasks that may be scheduled.
-        self.discard_scheduled();
-
-        // Step 2: attempt to remove tasks starting at the back of the vector.
-        while self.tasks.len() > len {
-            // There is at least one task since `len()` was non-zero.
-            let task = self.tasks.last().unwrap();
-
-            // Ordering: Relaxed ordering is sufficient since the task is
-            // effectively discarded.
-            if task
-                .next
-                .compare_exchange(SLEEPING, EMPTY, Ordering::Relaxed, Ordering::Relaxed)
-                .is_err()
-            {
-                // The task could not be removed for now so the set of tasks cannot
-                // be shrunk further.
-                break;
-            }
-
-            self.tasks.pop();
-        }
     }
 
     /// Returns `true` if one or more sub-tasks are currently scheduled.
@@ -271,10 +223,6 @@ impl TaskSet {
 
         waker_ref(&self.tasks[idx])
     }
-
-    pub(crate) fn len(&self) -> usize {
-        self.task_count
-    }
 }
 
 /// Internals shared between a `TaskSet` and its associated `Task`s.