net: add generic trait to combine UnixListener and TcpListener (#4385)

tokio-util/src/lib.rs

@@ -30,6 +30,7 @@ cfg_codec! {
 
 cfg_net! {
     pub mod udp;
+    pub mod net;
 }
 
 cfg_compat! {

tokio-util/src/net/mod.rs

@@ -0,0 +1,97 @@
+//! TCP/UDP/Unix helpers for tokio.
+
+use crate::either::Either;
+use std::future::Future;
+use std::io::Result;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+#[cfg(unix)]
+pub mod unix;
+
+/// A trait for a listener: `TcpListener` and `UnixListener`.
+pub trait Listener {
+    /// The stream's type of this listener.
+    type Io: tokio::io::AsyncRead + tokio::io::AsyncWrite;
+    /// The socket address type of this listener.
+    type Addr;
+
+    /// Polls to accept a new incoming connection to this listener.
+    fn poll_accept(&mut self, cx: &mut Context<'_>) -> Poll<Result<(Self::Io, Self::Addr)>>;
+
+    /// Accepts a new incoming connection from this listener.
+    fn accept(&mut self) -> ListenerAcceptFut<'_, Self>
+    where
+        Self: Sized,
+    {
+        ListenerAcceptFut { listener: self }
+    }
+
+    /// Returns the local address that this listener is bound to.
+    fn local_addr(&self) -> Result<Self::Addr>;
+}
+
+impl Listener for tokio::net::TcpListener {
+    type Io = tokio::net::TcpStream;
+    type Addr = std::net::SocketAddr;
+
+    fn poll_accept(&mut self, cx: &mut Context<'_>) -> Poll<Result<(Self::Io, Self::Addr)>> {
+        Self::poll_accept(self, cx)
+    }
+
+    fn local_addr(&self) -> Result<Self::Addr> {
+        self.local_addr().map(Into::into)
+    }
+}
+
+/// Future for accepting a new connection from a listener.
+#[derive(Debug)]
+#[must_use = "futures do nothing unless you `.await` or poll them"]
+pub struct ListenerAcceptFut<'a, L> {
+    listener: &'a mut L,
+}
+
+impl<'a, L> Future for ListenerAcceptFut<'a, L>
+where
+    L: Listener,
+{
+    type Output = Result<(L::Io, L::Addr)>;
+
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        self.listener.poll_accept(cx)
+    }
+}
+
+impl<L, R> Either<L, R>
+where
+    L: Listener,
+    R: Listener,
+{
+    /// Accepts a new incoming connection from this listener.
+    pub async fn accept(&mut self) -> Result<Either<(L::Io, L::Addr), (R::Io, R::Addr)>> {
+        match self {
+            Either::Left(listener) => {
+                let (stream, addr) = listener.accept().await?;
+                Ok(Either::Left((stream, addr)))
+            }
+            Either::Right(listener) => {
+                let (stream, addr) = listener.accept().await?;
+                Ok(Either::Right((stream, addr)))
+            }
+        }
+    }
+
+    /// Returns the local address that this listener is bound to.
+    pub fn local_addr(&self) -> Result<Either<L::Addr, R::Addr>> {
+        match self {
+            Either::Left(listener) => {
+                let addr = listener.local_addr()?;
+                Ok(Either::Left(addr))
+            }
+            Either::Right(listener) => {
+                let addr = listener.local_addr()?;
+                Ok(Either::Right(addr))
+            }
+        }
+    }
+}

tokio-util/src/net/unix/mod.rs

@@ -0,0 +1,18 @@
+//! Unix domain socket helpers.
+
+use super::Listener;
+use std::io::Result;
+use std::task::{Context, Poll};
+
+impl Listener for tokio::net::UnixListener {
+    type Io = tokio::net::UnixStream;
+    type Addr = tokio::net::unix::SocketAddr;
+
+    fn poll_accept(&mut self, cx: &mut Context<'_>) -> Poll<Result<(Self::Io, Self::Addr)>> {
+        Self::poll_accept(self, cx)
+    }
+
+    fn local_addr(&self) -> Result<Self::Addr> {
+        self.local_addr().map(Into::into)
+    }
+}