codec: update to use std-future (#1214)

Strategy was to

- copy the old codec code that was temporarily being stashed in `tokio-io`
- modify all the type signatures to use Pin, as literal a translation as possible
- fix up the tests likewise

This is intended just to get things compiling and passing tests. Beyond that there is surely
lots of refactoring that can be done to make things more idiomatic. The docs are unchanged.

Closes #1189

tokio-codec/src/framed_write.rs

@@ -0,0 +1,271 @@
+#![allow(deprecated)]
+
+use log::trace;
+use std::fmt;
+use std::io::{self, Read};
+
+use super::framed::Fuse;
+use crate::decoder::Decoder;
+use crate::encoder::Encoder;
+use tokio_futures::{Sink, Stream};
+use tokio_io::{AsyncRead, AsyncWrite};
+
+use bytes::BytesMut;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+/// A `Sink` of frames encoded to an `AsyncWrite`.
+pub struct FramedWrite<T, E> {
+    inner: FramedWrite2<Fuse<T, E>>,
+}
+
+pub struct FramedWrite2<T> {
+    inner: T,
+    buffer: BytesMut,
+}
+
+const INITIAL_CAPACITY: usize = 8 * 1024;
+const BACKPRESSURE_BOUNDARY: usize = INITIAL_CAPACITY;
+
+impl<T, E> FramedWrite<T, E>
+where
+    T: AsyncWrite,
+    E: Encoder,
+{
+    /// 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)),
+        }
+    }
+}
+
+impl<T, E> FramedWrite<T, E> {
+    /// Returns a reference to the underlying I/O stream wrapped by
+    /// `FramedWrite`.
+    ///
+    /// Note that care should be taken to not tamper with the underlying stream
+    /// 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
+    }
+
+    /// Returns a mutable reference to the underlying I/O stream wrapped by
+    /// `FramedWrite`.
+    ///
+    /// Note that care should be taken to not tamper with the underlying stream
+    /// 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
+    }
+
+    /// Consumes the `FramedWrite`, returning its underlying I/O stream.
+    ///
+    /// Note that care should be taken to not tamper with the underlying stream
+    /// 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
+    }
+
+    /// Returns a reference to the underlying decoder.
+    pub fn encoder(&self) -> &E {
+        &self.inner.inner.1
+    }
+
+    /// Returns a mutable reference to the underlying decoder.
+    pub fn encoder_mut(&mut self) -> &mut E {
+        &mut self.inner.inner.1
+    }
+}
+
+// This impl just defers to the underlying FramedWrite2
+impl<T, I, E> Sink<I> for FramedWrite<T, E>
+where
+    T: AsyncWrite + Unpin,
+    E: Encoder<Item = I> + Unpin,
+    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)
+    }
+
+    fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
+        pin!(Pin::get_mut(self).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)
+    }
+
+    fn poll_close(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        pin!(Pin::get_mut(self).inner).poll_close(cx)
+    }
+}
+
+impl<T, D> Stream for FramedWrite<T, D>
+where
+    T: Stream + Unpin,
+    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)
+    }
+}
+
+impl<T, U> fmt::Debug for FramedWrite<T, U>
+where
+    T: fmt::Debug,
+    U: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("FramedWrite")
+            .field("inner", &self.inner.get_ref().0)
+            .field("encoder", &self.inner.get_ref().1)
+            .field("buffer", &self.inner.buffer)
+            .finish()
+    }
+}
+
+// ===== impl FramedWrite2 =====
+
+pub fn framed_write2<T>(inner: T) -> FramedWrite2<T> {
+    FramedWrite2 {
+        inner: inner,
+        buffer: BytesMut::with_capacity(INITIAL_CAPACITY),
+    }
+}
+
+pub fn framed_write2_with_buffer<T>(inner: T, mut buf: BytesMut) -> FramedWrite2<T> {
+    if buf.capacity() < INITIAL_CAPACITY {
+        let bytes_to_reserve = INITIAL_CAPACITY - buf.capacity();
+        buf.reserve(bytes_to_reserve);
+    }
+    FramedWrite2 {
+        inner: inner,
+        buffer: buf,
+    }
+}
+
+impl<T> FramedWrite2<T> {
+    pub fn get_ref(&self) -> &T {
+        &self.inner
+    }
+
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    pub fn into_parts(self) -> (T, BytesMut) {
+        (self.inner, self.buffer)
+    }
+
+    pub fn get_mut(&mut self) -> &mut T {
+        &mut self.inner
+    }
+}
+
+impl<I, T> Sink<I> for FramedWrite2<T>
+where
+    T: AsyncWrite + Encoder<Item = I> + Unpin,
+{
+    type Error = T::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
+        // *still* over 8KiB, then apply backpressure (reject the send).
+        if self.buffer.len() >= BACKPRESSURE_BOUNDARY {
+            match self.as_mut().poll_flush(cx) {
+                Poll::Pending => return Poll::Pending,
+                Poll::Ready(Err(e)) => return Poll::Ready(Err(e)),
+                Poll::Ready(Ok(())) => (),
+            };
+
+            if self.buffer.len() >= BACKPRESSURE_BOUNDARY {
+                return Poll::Pending;
+            }
+        }
+        Poll::Ready(Ok(()))
+    }
+
+    fn start_send(self: Pin<&mut Self>, item: I) -> Result<(), Self::Error> {
+        let pinned = Pin::get_mut(self);
+        pinned.inner.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);
+
+        while !pinned.buffer.is_empty() {
+            trace!("writing; remaining={}", pinned.buffer.len());
+
+            let buf = &pinned.buffer;
+            let n = try_ready!(pin!(pinned.inner).poll_write(cx, &buf));
+
+            if n == 0 {
+                return Poll::Ready(Err(io::Error::new(
+                    io::ErrorKind::WriteZero,
+                    "failed to \
+                     write frame to transport",
+                )
+                .into()));
+            }
+
+            // TODO: Add a way to `bytes` to do this w/o returning the drained data.
+            let _ = pinned.buffer.split_to(n);
+        }
+
+        // Try flushing the underlying IO
+        try_ready!(pin!(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>> {
+        let () = try_ready!(pin!(self).poll_flush(cx));
+        let () = try_ready!(pin!(self.inner).poll_shutdown(cx));
+        Poll::Ready(Ok(()))
+    }
+}
+
+impl<T: Decoder> Decoder for FramedWrite2<T> {
+    type Item = T::Item;
+    type Error = T::Error;
+
+    fn decode(&mut self, src: &mut BytesMut) -> Result<Option<T::Item>, T::Error> {
+        self.inner.decode(src)
+    }
+
+    fn decode_eof(&mut self, src: &mut BytesMut) -> Result<Option<T::Item>, T::Error> {
+        self.inner.decode_eof(src)
+    }
+}
+
+impl<T: Read> Read for FramedWrite2<T> {
+    fn read(&mut self, dst: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(dst)
+    }
+}
+
+impl<T: AsyncRead + Unpin> AsyncRead for FramedWrite2<T> {
+    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [u8]) -> bool {
+        self.inner.prepare_uninitialized_buffer(buf)
+    }
+
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut [u8],
+    ) -> Poll<Result<usize, io::Error>> {
+        pin!(Pin::get_mut(self).inner).poll_read(cx, buf)
+    }
+}