add AsyncFd::async_io_mut

tokio/src/io/async_fd.rs

@@ -559,7 +559,7 @@ impl<T: AsRawFd> AsyncFd<T> {
     ///     let async_fd = AsyncFd::new(socket)?;
     ///
     ///     let written = async_fd
-    ///         .async_io(Interest::WRITABLE, || async_fd.get_ref().send(&[1, 2]))
+    ///         .async_io(Interest::WRITABLE, |inner| inner.send(&[1, 2]))
     ///         .await?;
     ///
     ///     println!("wrote {written} bytes");
@@ -596,9 +596,27 @@ impl<T: AsRawFd> AsyncFd<T> {
     pub async fn async_io<R>(
         &self,
         interest: Interest,
-        f: impl FnMut() -> io::Result<R>,
+        mut f: impl FnMut(&T) -> io::Result<R>,
     ) -> io::Result<R> {
-        self.registration.async_io(interest, f).await
+        self.registration
+            .async_io(interest, || f(self.get_ref()))
+            .await
+    }
+
+    /// Reads or writes from the file descriptor using a user-provided IO operation.
+    ///
+    /// The behavior is the same as [`async_io`], except that the closure can mutate the inner
+    /// value of the [`AsyncFd`].
+    ///
+    /// [`async_io`]: AsyncFd::async_io
+    pub async fn async_io_mut<R>(
+        &mut self,
+        interest: Interest,
+        mut f: impl FnMut(&mut T) -> io::Result<R>,
+    ) -> io::Result<R> {
+        self.registration
+            .async_io(interest, || f(self.inner.as_mut().unwrap()))
+            .await
     }
 }