Use MaybeFuture

iroh/src/magicsock/relay_actor.rs

@@ -13,8 +13,6 @@ use std::{
 use anyhow::Context;
 use backoff::backoff::Backoff;
 use bytes::{Bytes, BytesMut};
-use futures_lite::future;
-use futures_util::future::Either;
 use iroh_metrics::{inc, inc_by};
 use iroh_relay::{self as relay, client::ClientError, ReceivedMessage, RelayUrl, MAX_PACKET_SIZE};
 use tokio::{
@@ -28,6 +26,7 @@ use tracing::{debug, error, info, info_span, trace, warn, Instrument};
 use crate::{
     key::{NodeId, PUBLIC_KEY_LENGTH},
     magicsock::{MagicSock, Metrics as MagicsockMetrics, RelayContents, RelayDatagramsQueue},
+    util::MaybeFuture,
 };
 
 /// How long a non-home relay connection needs to be idle (last written to) before we close it.
@@ -113,11 +112,10 @@ impl ConnectedRelayActor {
         let relay_client = self.relay_client.clone();
         relay_client.connect().await.context("initial connection")?;
 
-        // When this future is Either::Right this is a future which is currently sending
+        // When this future has an inner, it is a future which is currently sending
         // something to the relay server.  Nothing else can be sent to the relay server at
-        // the same time.  If this future is Either::Left nothing is being sent to the
-        // relay server.
-        let mut relay_send_fut = Either::Left(future::pending());
+        // the same time.
+        let mut relay_send_fut = MaybeFuture::none();
 
         loop {
             // If a read error occurred on the connection it might have been lost.  But we
@@ -137,13 +135,15 @@ impl ConnectedRelayActor {
                         break;
                     }
                 }
-                // Only poll relay_send_fut if it is sending to the future.
-                _ = &mut relay_send_fut, if matches!(relay_send_fut, Either::Right(_)) => {
-                    relay_send_fut = Either::Left(future::pending());
+                // Only poll relay_send_fut if it is sending to the relay.
+                _ = &mut relay_send_fut, if relay_send_fut.is_some() => {
+                    relay_send_fut = MaybeFuture::none();
                 }
                 // Only poll for new datagrams if relay_send_fut is not busy.
-                Some(msg) = self.relay_datagrams_send.recv(), if matches!(relay_send_fut, Either::Left(_)) => {
-                    relay_send_fut = Either::Right(Box::pin(relay_client.send(msg.0, msg.1)));
+                Some(msg) = self.relay_datagrams_send.recv(), if relay_send_fut.is_none() => {
+                    relay_send_fut = MaybeFuture::with_future(
+                        Box::pin(relay_client.send(msg.0, msg.1))
+                    );
                     self.last_write = Instant::now();
 
                 }

iroh/src/util.rs

@@ -6,17 +6,44 @@ use std::{
     task::{Context, Poll},
 };
 
-/// Resolves to pending if the inner is `None`.
+/// A future which may not be present.
+///
+/// This is a single type which may optionally contain a future.  If there is no inner
+/// future polling will always return [`Poll::Pending`].
+///
+/// The [`Default`] impl will create a [`MaybeFuture`] without an inner.
 #[derive(Debug)]
 pub(crate) struct MaybeFuture<T> {
     /// Future to be polled.
     pub inner: Option<T>,
 }
 
+impl<T> MaybeFuture<T> {
+    /// Creates a [`MaybeFuture`] without an inner future.
+    pub(crate) fn none() -> Self {
+        Self { inner: None }
+    }
+
+    /// Creates a [`MaybeFuture`] with an inner future.
+    pub(crate) fn with_future(fut: T) -> Self {
+        Self { inner: Some(fut) }
+    }
+
+    /// Returns `true` if the inner is empty.
+    pub(crate) fn is_none(&self) -> bool {
+        self.inner.is_none()
+    }
+
+    /// Returns `true` if the inner contains a future.
+    pub(crate) fn is_some(&self) -> bool {
+        self.inner.is_some()
+    }
+}
+
 // NOTE: explicit implementation to bypass derive unnecessary bounds
 impl<T> Default for MaybeFuture<T> {
     fn default() -> Self {
-        MaybeFuture { inner: None }
+        Self::none()
     }
 }