stream: add Stream wrappers in tokio-stream (#3343)

tokio-stream/src/wrappers/split.rs

@@ -0,0 +1,59 @@
+use crate::Stream;
+use pin_project_lite::pin_project;
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+use tokio::io::{AsyncBufRead, Split};
+
+pin_project! {
+    /// A wrapper around [`tokio::io::Split`] that implements [`Stream`].
+    ///
+    /// [`tokio::io::Split`]: struct@tokio::io::Split
+    /// [`Stream`]: trait@crate::Stream
+    #[derive(Debug)]
+    #[cfg_attr(docsrs, doc(cfg(feature = "io-util")))]
+    pub struct SplitStream<R> {
+        #[pin]
+        inner: Split<R>,
+    }
+}
+
+impl<R> SplitStream<R> {
+    /// Create a new `SplitStream`.
+    pub fn new(split: Split<R>) -> Self {
+        Self { inner: split }
+    }
+
+    /// Get back the inner `Split`.
+    pub fn into_inner(self) -> Split<R> {
+        self.inner
+    }
+
+    /// Obtain a pinned reference to the inner `Split<R>`.
+    pub fn as_pin_mut(self: Pin<&mut Self>) -> Pin<&mut Split<R>> {
+        self.project().inner
+    }
+}
+
+impl<R: AsyncBufRead> Stream for SplitStream<R> {
+    type Item = io::Result<Vec<u8>>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        self.project()
+            .inner
+            .poll_next_segment(cx)
+            .map(Result::transpose)
+    }
+}
+
+impl<R> AsRef<Split<R>> for SplitStream<R> {
+    fn as_ref(&self) -> &Split<R> {
+        &self.inner
+    }
+}
+
+impl<R> AsMut<Split<R>> for SplitStream<R> {
+    fn as_mut(&mut self) -> &mut Split<R> {
+        &mut self.inner
+    }
+}