feat(io,net): add split

compio-io/Cargo.toml

@@ -12,6 +12,7 @@ repository = { workspace = true }
 
 [dependencies]
 compio-buf = { workspace = true, features = ["arrayvec"] }
+futures-util = { workspace = true }
 paste = { workspace = true }
 
 [dev-dependencies]

compio-io/src/lib.rs

@@ -107,11 +107,13 @@ mod buffer;
 #[cfg(feature = "compat")]
 pub mod compat;
 mod read;
+mod split;
 pub mod util;
 mod write;
 
 pub(crate) type IoResult<T> = std::io::Result<T>;
 
 pub use read::*;
+pub use split::*;
 pub use util::{copy, null, repeat};
 pub use write::*;

compio-io/src/split.rs

@@ -0,0 +1,75 @@
+use std::sync::Arc;
+
+use compio_buf::{BufResult, IoBuf, IoBufMut, IoVectoredBuf, IoVectoredBufMut};
+use futures_util::lock::Mutex;
+
+use crate::{AsyncRead, AsyncWrite, IoResult};
+
+/// Splits a single value implementing `AsyncRead + AsyncWrite` into separate
+/// [`AsyncRead`] and [`AsyncWrite`] handles.
+pub fn split<T: AsyncRead + AsyncWrite>(stream: T) -> (ReadHalf<T>, WriteHalf<T>) {
+    let stream = Arc::new(Mutex::new(stream));
+    (ReadHalf(stream.clone()), WriteHalf(stream))
+}
+
+/// The readable half of a value returned from [`split`].
+#[derive(Debug)]
+pub struct ReadHalf<T>(Arc<Mutex<T>>);
+
+impl<T: Unpin> ReadHalf<T> {
+    /// Reunites with a previously split [`WriteHalf`].
+    ///
+    /// # Panics
+    ///
+    /// If this [`ReadHalf`] and the given [`WriteHalf`] do not originate from
+    /// the same [`split`] operation this method will panic.
+    /// This can be checked ahead of time by comparing the stored pointer
+    /// of the two halves.
+    #[track_caller]
+    pub fn unsplit(self, w: WriteHalf<T>) -> T {
+        if Arc::ptr_eq(&self.0, &w.0) {
+            drop(w);
+            let inner = Arc::try_unwrap(self.0).expect("`Arc::try_unwrap` failed");
+            inner.into_inner()
+        } else {
+            #[cold]
+            fn panic_unrelated() -> ! {
+                panic!("Unrelated `WriteHalf` passed to `ReadHalf::unsplit`.")
+            }
+
+            panic_unrelated()
+        }
+    }
+}
+
+impl<T: AsyncRead> AsyncRead for ReadHalf<T> {
+    async fn read<B: IoBufMut>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.lock().await.read(buf).await
+    }
+
+    async fn read_vectored<V: IoVectoredBufMut>(&mut self, buf: V) -> BufResult<usize, V> {
+        self.0.lock().await.read_vectored(buf).await
+    }
+}
+
+/// The writable half of a value returned from [`split`].
+#[derive(Debug)]
+pub struct WriteHalf<T>(Arc<Mutex<T>>);
+
+impl<T: AsyncWrite> AsyncWrite for WriteHalf<T> {
+    async fn write<B: IoBuf>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.lock().await.write(buf).await
+    }
+
+    async fn write_vectored<B: IoVectoredBuf>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.lock().await.write_vectored(buf).await
+    }
+
+    async fn flush(&mut self) -> IoResult<()> {
+        self.0.lock().await.flush().await
+    }
+
+    async fn shutdown(&mut self) -> IoResult<()> {
+        self.0.lock().await.shutdown().await
+    }
+}

compio-io/tests/io.rs

@@ -2,7 +2,7 @@ use std::io::Cursor;
 
 use compio_buf::{arrayvec::ArrayVec, BufResult, IoBuf, IoBufMut};
 use compio_io::{
-    AsyncRead, AsyncReadAt, AsyncReadAtExt, AsyncReadExt, AsyncWrite, AsyncWriteAt,
+    split, AsyncRead, AsyncReadAt, AsyncReadAtExt, AsyncReadExt, AsyncWrite, AsyncWriteAt,
     AsyncWriteAtExt, AsyncWriteExt,
 };
 
@@ -355,3 +355,19 @@ async fn read_to_end_at() {
     assert_eq!(len, 4);
     assert_eq!(buf, [4, 5, 1, 4]);
 }
+
+#[tokio::test]
+async fn split_unsplit() {
+    let src = Cursor::new([1, 1, 4, 5, 1, 4]);
+    let (mut read, mut write) = split(src);
+
+    let (len, buf) = read.read([0, 0, 0]).await.unwrap();
+    assert_eq!(len, 3);
+    assert_eq!(buf, [1, 1, 4]);
+
+    let (len, _) = write.write([2, 2, 2]).await.unwrap();
+    assert_eq!(len, 3);
+
+    let src = read.unsplit(write);
+    assert_eq!(src.into_inner(), [1, 1, 4, 2, 2, 2]);
+}

compio-net/src/lib.rs

@@ -7,13 +7,15 @@
 
 mod resolve;
 mod socket;
+pub(crate) mod split;
 mod tcp;
 mod udp;
 mod unix;
 
 pub use resolve::ToSocketAddrsAsync;
 pub(crate) use resolve::{each_addr, first_addr_buf};
 pub(crate) use socket::*;
+pub use split::*;
 pub use tcp::*;
 pub use udp::*;
 pub use unix::*;

compio-net/src/split.rs

@@ -0,0 +1,135 @@
+use std::{error::Error, fmt, io, ops::Deref, sync::Arc};
+
+use compio_buf::{BufResult, IoBuf, IoBufMut, IoVectoredBuf, IoVectoredBufMut};
+use compio_io::{AsyncRead, AsyncWrite};
+
+pub(crate) fn split<T>(stream: &T) -> (ReadHalf<T>, WriteHalf<T>)
+where
+    for<'a> &'a T: AsyncRead + AsyncWrite,
+{
+    (ReadHalf(stream), WriteHalf(stream))
+}
+
+/// Borrowed read half.
+#[derive(Debug)]
+pub struct ReadHalf<'a, T>(&'a T);
+
+impl<T> AsyncRead for ReadHalf<'_, T>
+where
+    for<'a> &'a T: AsyncRead,
+{
+    async fn read<B: IoBufMut>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.read(buf).await
+    }
+
+    async fn read_vectored<V: IoVectoredBufMut>(&mut self, buf: V) -> BufResult<usize, V> {
+        self.0.read_vectored(buf).await
+    }
+}
+
+/// Borrowed write half.
+#[derive(Debug)]
+pub struct WriteHalf<'a, T>(&'a T);
+
+impl<T> AsyncWrite for WriteHalf<'_, T>
+where
+    for<'a> &'a T: AsyncWrite,
+{
+    async fn write<B: IoBuf>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.write(buf).await
+    }
+
+    async fn write_vectored<B: IoVectoredBuf>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.write_vectored(buf).await
+    }
+
+    async fn flush(&mut self) -> io::Result<()> {
+        self.0.flush().await
+    }
+
+    async fn shutdown(&mut self) -> io::Result<()> {
+        self.0.shutdown().await
+    }
+}
+
+pub(crate) fn into_split<T>(stream: T) -> (OwnedReadHalf<T>, OwnedWriteHalf<T>)
+where
+    for<'a> &'a T: AsyncRead + AsyncWrite,
+{
+    let stream = Arc::new(stream);
+    (OwnedReadHalf(stream.clone()), OwnedWriteHalf(stream))
+}
+
+/// Owned read half.
+#[derive(Debug)]
+pub struct OwnedReadHalf<T>(Arc<T>);
+
+impl<T: Unpin> OwnedReadHalf<T> {
+    /// Attempts to put the two halves of a `TcpStream` back together and
+    /// recover the original socket. Succeeds only if the two halves
+    /// originated from the same call to `into_split`.
+    pub fn reunite(self, w: OwnedWriteHalf<T>) -> Result<T, ReuniteError<T>> {
+        if Arc::ptr_eq(&self.0, &w.0) {
+            drop(w);
+            Ok(Arc::try_unwrap(self.0)
+                .ok()
+                .expect("`Arc::try_unwrap` failed"))
+        } else {
+            Err(ReuniteError(self, w))
+        }
+    }
+}
+
+impl<T> AsyncRead for OwnedReadHalf<T>
+where
+    for<'a> &'a T: AsyncRead,
+{
+    async fn read<B: IoBufMut>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.deref().read(buf).await
+    }
+
+    async fn read_vectored<V: IoVectoredBufMut>(&mut self, buf: V) -> BufResult<usize, V> {
+        self.0.deref().read_vectored(buf).await
+    }
+}
+
+/// Owned write half.
+#[derive(Debug)]
+pub struct OwnedWriteHalf<T>(Arc<T>);
+
+impl<T> AsyncWrite for OwnedWriteHalf<T>
+where
+    for<'a> &'a T: AsyncWrite,
+{
+    async fn write<B: IoBuf>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.deref().write(buf).await
+    }
+
+    async fn write_vectored<B: IoVectoredBuf>(&mut self, buf: B) -> BufResult<usize, B> {
+        self.0.deref().write_vectored(buf).await
+    }
+
+    async fn flush(&mut self) -> io::Result<()> {
+        self.0.deref().flush().await
+    }
+
+    async fn shutdown(&mut self) -> io::Result<()> {
+        self.0.deref().shutdown().await
+    }
+}
+
+/// Error indicating that two halves were not from the same socket, and thus
+/// could not be reunited.
+#[derive(Debug)]
+pub struct ReuniteError<T>(pub OwnedReadHalf<T>, pub OwnedWriteHalf<T>);
+
+impl<T> fmt::Display for ReuniteError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(
+            f,
+            "tried to reunite halves that are not from the same socket"
+        )
+    }
+}
+
+impl<T: fmt::Debug> Error for ReuniteError<T> {}

compio-net/src/tcp.rs

@@ -5,7 +5,7 @@ use compio_io::{AsyncRead, AsyncWrite};
 use compio_runtime::{impl_attachable, impl_try_as_raw_fd};
 use socket2::{Protocol, SockAddr, Type};
 
-use crate::{Socket, ToSocketAddrsAsync};
+use crate::{OwnedReadHalf, OwnedWriteHalf, ReadHalf, Socket, ToSocketAddrsAsync, WriteHalf};
 
 /// A TCP socket server, listening for connections.
 ///
@@ -203,6 +203,25 @@ impl TcpStream {
             .local_addr()
             .map(|addr| addr.as_socket().expect("should be SocketAddr"))
     }
+
+    /// Splits a [`TcpStream`] into a read half and a write half, which can be
+    /// used to read and write the stream concurrently.
+    ///
+    /// This method is more efficient than
+    /// [`into_split`](TcpStream::into_split), but the halves cannot
+    /// be moved into independently spawned tasks.
+    pub fn split(&self) -> (ReadHalf<Self>, WriteHalf<Self>) {
+        crate::split(self)
+    }
+
+    /// Splits a [`TcpStream`] into a read half and a write half, which can be
+    /// used to read and write the stream concurrently.
+    ///
+    /// Unlike [`split`](TcpStream::split), the owned halves can be moved to
+    /// separate tasks, however this comes at the cost of a heap allocation.
+    pub fn into_split(self) -> (OwnedReadHalf<Self>, OwnedWriteHalf<Self>) {
+        crate::into_split(self)
+    }
 }
 
 impl AsyncRead for TcpStream {

compio-net/src/unix.rs

@@ -5,7 +5,7 @@ use compio_io::{AsyncRead, AsyncWrite};
 use compio_runtime::{impl_attachable, impl_try_as_raw_fd};
 use socket2::{Domain, SockAddr, Type};
 
-use crate::Socket;
+use crate::{OwnedReadHalf, OwnedWriteHalf, ReadHalf, Socket, WriteHalf};
 
 /// A Unix socket server, listening for connections.
 ///
@@ -159,6 +159,25 @@ impl UnixStream {
     pub fn local_addr(&self) -> io::Result<SockAddr> {
         self.inner.local_addr()
     }
+
+    /// Splits a [`UnixStream`] into a read half and a write half, which can be
+    /// used to read and write the stream concurrently.
+    ///
+    /// This method is more efficient than
+    /// [`into_split`](UnixStream::into_split), but the halves cannot
+    /// be moved into independently spawned tasks.
+    pub fn split(&self) -> (ReadHalf<Self>, WriteHalf<Self>) {
+        crate::split(self)
+    }
+
+    /// Splits a [`UnixStream`] into a read half and a write half, which can be
+    /// used to read and write the stream concurrently.
+    ///
+    /// Unlike [`split`](UnixStream::split), the owned halves can be moved to
+    /// separate tasks, however this comes at the cost of a heap allocation.
+    pub fn into_split(self) -> (OwnedReadHalf<Self>, OwnedWriteHalf<Self>) {
+        crate::into_split(self)
+    }
 }
 
 impl AsyncRead for UnixStream {