codec: Remove Unpin requirement from Framed[Read,Write,] (#1758)

cc #1252

tokio-util/Cargo.toml

@@ -26,6 +26,7 @@ bytes = "0.4.7"
 futures-core = "0.3.0"
 futures-sink = "0.3.0"
 log = "0.4"
+pin-project = "0.4"
 
 [dev-dependencies]
 tokio = { version = "=0.2.0-alpha.6", path = "../tokio" }

tokio-util/src/codec/framed.rs

@@ -8,6 +8,7 @@ use tokio::io::{AsyncBufRead, AsyncRead, AsyncWrite};
 use bytes::BytesMut;
 use futures_core::Stream;
 use futures_sink::Sink;
+use pin_project::pin_project;
 use std::fmt;
 use std::io::{self, BufRead, Read, Write};
 use std::pin::Pin;
@@ -17,11 +18,40 @@ use std::task::{Context, Poll};
 /// the `Encoder` and `Decoder` traits to encode and decode frames.
 ///
 /// You can create a `Framed` instance by using the `AsyncRead::framed` adapter.
+#[pin_project]
 pub struct Framed<T, U> {
+    #[pin]
     inner: FramedRead2<FramedWrite2<Fuse<T, U>>>,
 }
 
-pub(crate) struct Fuse<T, U>(pub(crate) T, pub(crate) U);
+#[pin_project]
+pub(crate) struct Fuse<T, U> {
+    #[pin]
+    pub(crate) io: T,
+    pub(crate) codec: U,
+}
+
+/// Abstracts over `FramedRead2` being either `FramedRead2<FramedWrite2<Fuse<T, U>>>` or
+/// `FramedRead2<Fuse<T, U>>` and lets the io and codec parts be extracted in either case.
+pub(crate) trait ProjectFuse {
+    type Io;
+    type Codec;
+
+    fn project(self: Pin<&mut Self>) -> Fuse<Pin<&mut Self::Io>, &mut Self::Codec>;
+}
+
+impl<T, U> ProjectFuse for Fuse<T, U> {
+    type Io = T;
+    type Codec = U;
+
+    fn project(self: Pin<&mut Self>) -> Fuse<Pin<&mut Self::Io>, &mut Self::Codec> {
+        let self_ = self.project();
+        Fuse {
+            io: self_.io,
+            codec: self_.codec,
+        }
+    }
+}
 
 impl<T, U> Framed<T, U>
 where
@@ -47,7 +77,7 @@ where
     /// break them into separate objects, allowing them to interact more easily.
     pub fn new(inner: T, codec: U) -> Framed<T, U> {
         Framed {
-            inner: framed_read2(framed_write2(Fuse(inner, codec))),
+            inner: framed_read2(framed_write2(Fuse { io: inner, codec })),
         }
     }
 }
@@ -76,7 +106,13 @@ impl<T, U> Framed<T, U> {
     pub fn from_parts(parts: FramedParts<T, U>) -> Framed<T, U> {
         Framed {
             inner: framed_read2_with_buffer(
-                framed_write2_with_buffer(Fuse(parts.io, parts.codec), parts.write_buf),
+                framed_write2_with_buffer(
+                    Fuse {
+                        io: parts.io,
+                        codec: parts.codec,
+                    },
+                    parts.write_buf,
+                ),
                 parts.read_buf,
             ),
         }
@@ -89,7 +125,7 @@ impl<T, U> Framed<T, U> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn get_ref(&self) -> &T {
-        &self.inner.get_ref().get_ref().0
+        &self.inner.get_ref().get_ref().io
     }
 
     /// Returns a mutable reference to the underlying I/O stream wrapped by
@@ -99,7 +135,7 @@ impl<T, U> Framed<T, U> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn get_mut(&mut self) -> &mut T {
-        &mut self.inner.get_mut().get_mut().0
+        &mut self.inner.get_mut().get_mut().io
     }
 
     /// Returns a reference to the underlying codec wrapped by
@@ -108,7 +144,7 @@ impl<T, U> Framed<T, U> {
     /// Note that care should be taken to not tamper with the underlying codec
     /// as it may corrupt the stream of frames otherwise being worked with.
     pub fn codec(&self) -> &U {
-        &self.inner.get_ref().get_ref().1
+        &self.inner.get_ref().get_ref().codec
     }
 
     /// Returns a mutable reference to the underlying codec wrapped by
@@ -117,7 +153,7 @@ impl<T, U> Framed<T, U> {
     /// Note that care should be taken to not tamper with the underlying codec
     /// as it may corrupt the stream of frames otherwise being worked with.
     pub fn codec_mut(&mut self) -> &mut U {
-        &mut self.inner.get_mut().get_mut().1
+        &mut self.inner.get_mut().get_mut().codec
     }
 
     /// Returns a reference to the read buffer.
@@ -131,7 +167,7 @@ impl<T, U> Framed<T, U> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn into_inner(self) -> T {
-        self.inner.into_inner().into_inner().0
+        self.inner.into_inner().into_inner().io
     }
 
     /// Consumes the `Frame`, returning its underlying I/O stream, the buffer
@@ -145,8 +181,8 @@ impl<T, U> Framed<T, U> {
         let (inner, write_buf) = inner.into_parts();
 
         FramedParts {
-            io: inner.0,
+            io: inner.io,
-            codec: inner.1,
+            codec: inner.codec,
             read_buf,
             write_buf,
             _priv: (),
@@ -156,38 +192,38 @@ impl<T, U> Framed<T, U> {
 
 impl<T, U> Stream for Framed<T, U>
 where
-    T: AsyncRead + Unpin,
+    T: AsyncRead,
-    U: Decoder + Unpin,
+    U: Decoder,
 {
     type Item = Result<U::Item, U::Error>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        pin!(self.get_mut().inner).poll_next(cx)
+        self.project().inner.poll_next(cx)
     }
 }
 
 impl<T, I, U> Sink<I> for Framed<T, U>
 where
-    T: AsyncWrite + Unpin,
+    T: AsyncWrite,
-    U: Encoder<Item = I> + Unpin,
+    U: Encoder<Item = I>,
     U::Error: From<io::Error>,
 {
     type Error = U::Error;
 
     fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        Pin::new(Pin::get_mut(self).inner.get_mut()).poll_ready(cx)
+        self.project().inner.get_pin_mut().poll_ready(cx)
     }
 
     fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
-        Pin::new(Pin::get_mut(self).inner.get_mut()).start_send(item)
+        self.project().inner.get_pin_mut().start_send(item)
     }
 
     fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        Pin::new(Pin::get_mut(self).inner.get_mut()).poll_flush(cx)
+        self.project().inner.get_pin_mut().poll_flush(cx)
     }
 
     fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        Pin::new(Pin::get_mut(self).inner.get_mut()).poll_close(cx)
+        self.project().inner.get_pin_mut().poll_close(cx)
     }
 }
 
@@ -198,8 +234,8 @@ where
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("Framed")
-            .field("io", &self.inner.get_ref().get_ref().0)
+            .field("io", &self.inner.get_ref().get_ref().io)
-            .field("codec", &self.inner.get_ref().get_ref().1)
+            .field("codec", &self.inner.get_ref().get_ref().codec)
             .finish()
     }
 }
@@ -208,23 +244,23 @@ where
 
 impl<T: Read, U> Read for Fuse<T, U> {
     fn read(&mut self, dst: &mut [u8]) -> io::Result<usize> {
-        self.0.read(dst)
+        self.io.read(dst)
     }
 }
 
 impl<T: BufRead, U> BufRead for Fuse<T, U> {
     fn fill_buf(&mut self) -> io::Result<&[u8]> {
-        self.0.fill_buf()
+        self.io.fill_buf()
     }
 
     fn consume(&mut self, amt: usize) {
-        self.0.consume(amt)
+        self.io.consume(amt)
     }
 }
 
-impl<T: AsyncRead + Unpin, U: Unpin> AsyncRead for Fuse<T, U> {
+impl<T: AsyncRead, U> AsyncRead for Fuse<T, U> {
     unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
-        self.0.prepare_uninitialized_buffer(buf)
+        self.io.prepare_uninitialized_buffer(buf)
     }
 
     fn poll_read(
@@ -232,45 +268,45 @@ impl<T: AsyncRead + Unpin, U: Unpin> AsyncRead for Fuse<T, U> {
         cx: &mut Context<'_>,
         buf: &mut [u8],
     ) -> Poll<Result<usize, io::Error>> {
-        pin!(self.get_mut().0).poll_read(cx, buf)
+        self.project().io.poll_read(cx, buf)
     }
 }
 
-impl<T: AsyncBufRead + Unpin, U: Unpin> AsyncBufRead for Fuse<T, U> {
+impl<T: AsyncBufRead, U> AsyncBufRead for Fuse<T, U> {
     fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
-        pin!(self.get_mut().0).poll_fill_buf(cx)
+        self.project().io.poll_fill_buf(cx)
     }
 
     fn consume(self: Pin<&mut Self>, amt: usize) {
-        pin!(self.get_mut().0).consume(amt)
+        self.project().io.consume(amt)
     }
 }
 
 impl<T: Write, U> Write for Fuse<T, U> {
     fn write(&mut self, src: &[u8]) -> io::Result<usize> {
-        self.0.write(src)
+        self.io.write(src)
     }
 
     fn flush(&mut self) -> io::Result<()> {
-        self.0.flush()
+        self.io.flush()
     }
 }
 
-impl<T: AsyncWrite + Unpin, U: Unpin> AsyncWrite for Fuse<T, U> {
+impl<T: AsyncWrite, U> AsyncWrite for Fuse<T, U> {
     fn poll_write(
         self: Pin<&mut Self>,
         cx: &mut Context<'_>,
         buf: &[u8],
     ) -> Poll<Result<usize, io::Error>> {
-        pin!(self.get_mut().0).poll_write(cx, buf)
+        self.project().io.poll_write(cx, buf)
     }
 
     fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
-        pin!(self.get_mut().0).poll_flush(cx)
+        self.project().io.poll_flush(cx)
     }
 
     fn poll_shutdown(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), io::Error>> {
-        pin!(self.get_mut().0).poll_shutdown(cx)
+        self.project().io.poll_shutdown(cx)
     }
 }
 
@@ -279,11 +315,11 @@ impl<T, U: Decoder> Decoder for Fuse<T, U> {
     type Error = U::Error;
 
     fn decode(&mut self, buffer: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> {
-        self.1.decode(buffer)
+        self.codec.decode(buffer)
     }
 
     fn decode_eof(&mut self, buffer: &mut BytesMut) -> Result<Option<Self::Item>, Self::Error> {
-        self.1.decode_eof(buffer)
+        self.codec.decode_eof(buffer)
     }
 }
 
@@ -292,7 +328,7 @@ impl<T, U: Encoder> Encoder for Fuse<T, U> {
     type Error = U::Error;
 
     fn encode(&mut self, item: Self::Item, dst: &mut BytesMut) -> Result<(), Self::Error> {
-        self.1.encode(item, dst)
+        self.codec.encode(item, dst)
     }
 }
 

tokio-util/src/codec/framed_read.rs

@@ -1,4 +1,4 @@
-use crate::codec::framed::Fuse;
+use crate::codec::framed::{Fuse, ProjectFuse};
 use crate::codec::Decoder;
 
 use tokio::io::AsyncRead;
@@ -7,16 +7,21 @@ use bytes::BytesMut;
 use futures_core::Stream;
 use futures_sink::Sink;
 use log::trace;
+use pin_project::pin_project;
 use std::fmt;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
 /// A `Stream` of messages decoded from an `AsyncRead`.
+#[pin_project]
 pub struct FramedRead<T, D> {
+    #[pin]
     inner: FramedRead2<Fuse<T, D>>,
 }
 
+#[pin_project]
 pub(crate) struct FramedRead2<T> {
+    #[pin]
     inner: T,
     eof: bool,
     is_readable: bool,
@@ -35,7 +40,10 @@ where
     /// Creates a new `FramedRead` with the given `decoder`.
     pub fn new(inner: T, decoder: D) -> FramedRead<T, D> {
         FramedRead {
-            inner: framed_read2(Fuse(inner, decoder)),
+            inner: framed_read2(Fuse {
+                io: inner,
+                codec: decoder,
+            }),
         }
     }
 }
@@ -48,7 +56,7 @@ impl<T, D> FramedRead<T, D> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn get_ref(&self) -> &T {
-        &self.inner.inner.0
+        &self.inner.inner.io
     }
 
     /// Returns a mutable reference to the underlying I/O stream wrapped by
@@ -58,7 +66,7 @@ impl<T, D> FramedRead<T, D> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn get_mut(&mut self) -> &mut T {
-        &mut self.inner.inner.0
+        &mut self.inner.inner.io
     }
 
     /// Consumes the `FramedRead`, returning its underlying I/O stream.
@@ -67,17 +75,17 @@ impl<T, D> FramedRead<T, D> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn into_inner(self) -> T {
-        self.inner.inner.0
+        self.inner.inner.io
     }
 
     /// Returns a reference to the underlying decoder.
     pub fn decoder(&self) -> &D {
-        &self.inner.inner.1
+        &self.inner.inner.codec
     }
 
     /// Returns a mutable reference to the underlying decoder.
     pub fn decoder_mut(&mut self) -> &mut D {
-        &mut self.inner.inner.1
+        &mut self.inner.inner.codec
     }
 
     /// Returns a reference to the read buffer.
@@ -88,38 +96,61 @@ impl<T, D> FramedRead<T, D> {
 
 impl<T, D> Stream for FramedRead<T, D>
 where
-    T: AsyncRead + Unpin,
+    T: AsyncRead,
-    D: Decoder + Unpin,
+    D: Decoder,
 {
     type Item = Result<D::Item, D::Error>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        pin!(self.get_mut().inner).poll_next(cx)
+        self.project().inner.poll_next(cx)
     }
 }
 
 // This impl just defers to the underlying T: Sink
 impl<T, I, D> Sink<I> for FramedRead<T, D>
 where
-    T: Sink<I> + Unpin,
+    T: Sink<I>,
-    D: Unpin,
 {
     type Error = T::Error;
 
     fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        pin!(Pin::get_mut(self).inner.inner.0).poll_ready(cx)
+        self.project()
+            .inner
+            .project()
+            .inner
+            .project()
+            .io
+            .poll_ready(cx)
     }
 
     fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
-        pin!(Pin::get_mut(self).inner.inner.0).start_send(item)
+        self.project()
+            .inner
+            .project()
+            .inner
+            .project()
+            .io
+            .start_send(item)
     }
 
     fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        pin!(Pin::get_mut(self).inner.inner.0).poll_flush(cx)
+        self.project()
+            .inner
+            .project()
+            .inner
+            .project()
+            .io
+            .poll_flush(cx)
     }
 
     fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        pin!(Pin::get_mut(self).inner.inner.0).poll_close(cx)
+        self.project()
+            .inner
+            .project()
+            .inner
+            .project()
+            .io
+            .poll_close(cx)
     }
 }
 
@@ -130,8 +161,8 @@ where
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("FramedRead")
-            .field("inner", &self.inner.inner.0)
+            .field("inner", &self.inner.inner.io)
-            .field("decoder", &self.inner.inner.1)
+            .field("decoder", &self.inner.inner.codec)
             .field("eof", &self.inner.eof)
             .field("is_readable", &self.inner.is_readable)
             .field("buffer", &self.inner.buffer)
@@ -180,6 +211,10 @@ impl<T> FramedRead2<T> {
         &mut self.inner
     }
 
+    pub(crate) fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut T> {
+        self.project().inner
+    }
+
     pub(crate) fn buffer(&self) -> &BytesMut {
         &self.buffer
     }
@@ -187,49 +222,65 @@ impl<T> FramedRead2<T> {
 
 impl<T> Stream for FramedRead2<T>
 where
-    T: AsyncRead + Decoder + Unpin,
+    T: ProjectFuse + AsyncRead,
+    T::Codec: Decoder,
 {
-    type Item = Result<T::Item, T::Error>;
+    type Item = Result<<T::Codec as Decoder>::Item, <T::Codec as Decoder>::Error>;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        let pinned = Pin::get_mut(self);
+        let mut pinned = self.project();
         loop {
             // Repeatedly call `decode` or `decode_eof` as long as it is
             // "readable". Readable is defined as not having returned `None`. If
             // the upstream has returned EOF, and the decoder is no longer
             // readable, it can be assumed that the decoder will never become
             // readable again, at which point the stream is terminated.
-            if pinned.is_readable {
+            if *pinned.is_readable {
-                if pinned.eof {
+                if *pinned.eof {
-                    let frame = pinned.inner.decode_eof(&mut pinned.buffer)?;
+                    let frame = pinned
+                        .inner
+                        .as_mut()
+                        .project()
+                        .codec
+                        .decode_eof(&mut pinned.buffer)?;
                     return Poll::Ready(frame.map(Ok));
                 }
 
                 trace!("attempting to decode a frame");
 
-                if let Some(frame) = pinned.inner.decode(&mut pinned.buffer)? {
+                if let Some(frame) = pinned
+                    .inner
+                    .as_mut()
+                    .project()
+                    .codec
+                    .decode(&mut pinned.buffer)?
+                {
                     trace!("frame decoded from buffer");
                     return Poll::Ready(Some(Ok(frame)));
                 }
 
-                pinned.is_readable = false;
+                *pinned.is_readable = false;
             }
 
-            assert!(!pinned.eof);
+            assert!(!*pinned.eof);
 
             // Otherwise, try to read more data and try again. Make sure we've
             // got room for at least one byte to read to ensure that we don't
             // get a spurious 0 that looks like EOF
             pinned.buffer.reserve(1);
-            let bytect = match pin!(pinned.inner).poll_read_buf(cx, &mut pinned.buffer)? {
+            let bytect = match pinned
+                .inner
+                .as_mut()
+                .poll_read_buf(cx, &mut pinned.buffer)?
+            {
                 Poll::Ready(ct) => ct,
                 Poll::Pending => return Poll::Pending,
             };
             if bytect == 0 {
-                pinned.eof = true;
+                *pinned.eof = true;
             }
 
-            pinned.is_readable = true;
+            *pinned.is_readable = true;
         }
     }
 }

tokio-util/src/codec/framed_write.rs

@@ -1,6 +1,6 @@
 use crate::codec::decoder::Decoder;
 use crate::codec::encoder::Encoder;
-use crate::codec::framed::Fuse;
+use crate::codec::framed::{Fuse, ProjectFuse};
 
 use tokio::io::{AsyncBufRead, AsyncRead, AsyncWrite};
 
@@ -8,17 +8,22 @@ use bytes::BytesMut;
 use futures_core::{ready, Stream};
 use futures_sink::Sink;
 use log::trace;
+use pin_project::pin_project;
 use std::fmt;
 use std::io::{self, BufRead, Read};
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
 /// A `Sink` of frames encoded to an `AsyncWrite`.
+#[pin_project]
 pub struct FramedWrite<T, E> {
+    #[pin]
     inner: FramedWrite2<Fuse<T, E>>,
 }
 
+#[pin_project]
 pub(crate) struct FramedWrite2<T> {
+    #[pin]
     inner: T,
     buffer: BytesMut,
 }
@@ -34,7 +39,10 @@ where
     /// Creates a new `FramedWrite` with the given `encoder`.
     pub fn new(inner: T, encoder: E) -> FramedWrite<T, E> {
         FramedWrite {
-            inner: framed_write2(Fuse(inner, encoder)),
+            inner: framed_write2(Fuse {
+                io: inner,
+                codec: encoder,
+            }),
         }
     }
 }
@@ -47,7 +55,7 @@ impl<T, E> FramedWrite<T, E> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn get_ref(&self) -> &T {
-        &self.inner.inner.0
+        &self.inner.inner.io
     }
 
     /// Returns a mutable reference to the underlying I/O stream wrapped by
@@ -57,7 +65,7 @@ impl<T, E> FramedWrite<T, E> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn get_mut(&mut self) -> &mut T {
-        &mut self.inner.inner.0
+        &mut self.inner.inner.io
     }
 
     /// Consumes the `FramedWrite`, returning its underlying I/O stream.
@@ -66,55 +74,60 @@ impl<T, E> FramedWrite<T, E> {
     /// of data coming in as it may corrupt the stream of frames otherwise
     /// being worked with.
     pub fn into_inner(self) -> T {
-        self.inner.inner.0
+        self.inner.inner.io
     }
 
     /// Returns a reference to the underlying decoder.
     pub fn encoder(&self) -> &E {
-        &self.inner.inner.1
+        &self.inner.inner.codec
     }
 
     /// Returns a mutable reference to the underlying decoder.
     pub fn encoder_mut(&mut self) -> &mut E {
-        &mut self.inner.inner.1
+        &mut self.inner.inner.codec
     }
 }
 
 // This impl just defers to the underlying FramedWrite2
 impl<T, I, E> Sink<I> for FramedWrite<T, E>
 where
-    T: AsyncWrite + Unpin,
+    T: AsyncWrite,
-    E: Encoder<Item = I> + Unpin,
+    E: Encoder<Item = I>,
     E::Error: From<io::Error>,
 {
     type Error = E::Error;
 
     fn poll_ready(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        pin!(Pin::get_mut(self).inner).poll_ready(cx)
+        self.project().inner.poll_ready(cx)
     }
 
     fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
-        pin!(Pin::get_mut(self).inner).start_send(item)
+        self.project().inner.start_send(item)
     }
 
     fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        pin!(Pin::get_mut(self).inner).poll_flush(cx)
+        self.project().inner.poll_flush(cx)
     }
 
     fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        pin!(Pin::get_mut(self).inner).poll_close(cx)
+        self.project().inner.poll_close(cx)
     }
 }
 
 impl<T, D> Stream for FramedWrite<T, D>
 where
-    T: Stream + Unpin,
+    T: Stream,
-    D: Unpin,
 {
     type Item = T::Item;
 
     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        Pin::new(Pin::get_mut(self).get_mut()).poll_next(cx)
+        self.project()
+            .inner
+            .project()
+            .inner
+            .project()
+            .io
+            .poll_next(cx)
     }
 }
 
@@ -125,8 +138,8 @@ where
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("FramedWrite")
-            .field("inner", &self.inner.get_ref().0)
+            .field("inner", &self.inner.get_ref().io)
-            .field("encoder", &self.inner.get_ref().1)
+            .field("encoder", &self.inner.get_ref().codec)
             .field("buffer", &self.inner.buffer)
             .finish()
     }
@@ -169,9 +182,10 @@ impl<T> FramedWrite2<T> {
 
 impl<I, T> Sink<I> for FramedWrite2<T>
 where
-    T: AsyncWrite + Encoder<Item = I> + Unpin,
+    T: ProjectFuse + AsyncWrite,
+    T::Codec: Encoder<Item = I>,
 {
-    type Error = T::Error;
+    type Error = <T::Codec as Encoder>::Error;
 
     fn poll_ready(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         // If the buffer is already over 8KiB, then attempt to flush it. If after flushing it's
@@ -191,20 +205,24 @@ where
     }
 
     fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
-        let pinned = Pin::get_mut(self);
+        let mut pinned = self.project();
-        pinned.inner.encode(item, &mut pinned.buffer)?;
+        pinned
+            .inner
+            .project()
+            .codec
+            .encode(item, &mut pinned.buffer)?;
         Ok(())
     }
 
     fn poll_flush(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
         trace!("flushing framed transport");
-        let pinned = Pin::get_mut(self);
+        let mut pinned = self.project();
 
         while !pinned.buffer.is_empty() {
             trace!("writing; remaining={}", pinned.buffer.len());
 
             let buf = &pinned.buffer;
-            let n = ready!(pin!(pinned.inner).poll_write(cx, &buf))?;
+            let n = ready!(pinned.inner.as_mut().poll_write(cx, &buf))?;
 
             if n == 0 {
                 return Poll::Ready(Err(io::Error::new(
@@ -220,15 +238,15 @@ where
         }
 
         // Try flushing the underlying IO
-        ready!(pin!(pinned.inner).poll_flush(cx))?;
+        ready!(pinned.inner.poll_flush(cx))?;
 
         trace!("framed transport flushed");
         Poll::Ready(Ok(()))
     }
 
     fn poll_close(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
-        ready!(pin!(self).poll_flush(cx))?;
+        ready!(self.as_mut().poll_flush(cx))?;
-        ready!(pin!(self.inner).poll_shutdown(cx))?;
+        ready!(self.project().inner.poll_shutdown(cx))?;
 
         Poll::Ready(Ok(()))
     }
@@ -263,7 +281,7 @@ impl<T: BufRead> BufRead for FramedWrite2<T> {
     }
 }
 
-impl<T: AsyncRead + Unpin> AsyncRead for FramedWrite2<T> {
+impl<T: AsyncRead> AsyncRead for FramedWrite2<T> {
     unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
         self.inner.prepare_uninitialized_buffer(buf)
     }
@@ -273,16 +291,28 @@ impl<T: AsyncRead + Unpin> AsyncRead for FramedWrite2<T> {
         cx: &mut Context<'_>,
         buf: &mut [u8],
     ) -> Poll<Result<usize, io::Error>> {
-        pin!(self.get_mut().inner).poll_read(cx, buf)
+        self.project().inner.poll_read(cx, buf)
     }
 }
 
-impl<T: AsyncBufRead + Unpin> AsyncBufRead for FramedWrite2<T> {
+impl<T: AsyncBufRead> AsyncBufRead for FramedWrite2<T> {
     fn poll_fill_buf(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<&[u8]>> {
-        pin!(self.get_mut().inner).poll_fill_buf(cx)
+        self.project().inner.poll_fill_buf(cx)
     }
 
     fn consume(self: Pin<&mut Self>, amt: usize) {
-        pin!(self.get_mut().inner).consume(amt)
+        self.project().inner.consume(amt)
+    }
+}
+
+impl<T> ProjectFuse for FramedWrite2<T>
+where
+    T: ProjectFuse,
+{
+    type Io = T::Io;
+    type Codec = T::Codec;
+
+    fn project(self: Pin<&mut Self>) -> Fuse<Pin<&mut Self::Io>, &mut Self::Codec> {
+        self.project().inner.project()
     }
 }

tokio-util/src/codec/macros.rs

@@ -1,7 +0,0 @@
-/// A macro to reduce some of the boilerplate for projecting from
-/// `Pin<&mut T>` to `Pin<&mut T.field>`
-macro_rules! pin {
-    ($e:expr) => {
-        std::pin::Pin::new(&mut $e)
-    };
-}

tokio-util/src/codec/mod.rs

@@ -9,9 +9,6 @@
 //! [`Sink`]: https://docs.rs/futures-sink/*/futures_sink/trait.Sink.html
 //! [`Stream`]: https://docs.rs/futures-core/*/futures_core/stream/trait.Stream.html
 
-#[macro_use]
-mod macros;
-
 mod bytes_codec;
 pub use self::bytes_codec::BytesCodec;