Tokio 0.3 Upgrade (#2319)

Co-authored-by: Urhengulas <johann.hemmann@code.berlin>
Co-authored-by: Eliza Weisman <eliza@buoyant.io>

src/common/io/rewind.rs

@@ -2,7 +2,7 @@ use std::marker::Unpin;
 use std::{cmp, io};
 
 use bytes::{Buf, Bytes};
-use tokio::io::{AsyncRead, AsyncWrite};
+use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 
 use crate::common::{task, Pin, Poll};
 
@@ -37,36 +37,33 @@ impl<T> Rewind<T> {
         (self.inner, self.pre.unwrap_or_else(Bytes::new))
     }
 
-    pub(crate) fn get_mut(&mut self) -> &mut T {
-        &mut self.inner
-    }
+    // pub(crate) fn get_mut(&mut self) -> &mut T {
+    //     &mut self.inner
+    // }
 }
 
 impl<T> AsyncRead for Rewind<T>
 where
     T: AsyncRead + Unpin,
 {
-    #[inline]
-    unsafe fn prepare_uninitialized_buffer(&self, buf: &mut [std::mem::MaybeUninit<u8>]) -> bool {
-        self.inner.prepare_uninitialized_buffer(buf)
-    }
-
     fn poll_read(
         mut self: Pin<&mut Self>,
         cx: &mut task::Context<'_>,
-        buf: &mut [u8],
-    ) -> Poll<io::Result<usize>> {
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<io::Result<()>> {
         if let Some(mut prefix) = self.pre.take() {
             // If there are no remaining bytes, let the bytes get dropped.
             if !prefix.is_empty() {
-                let copy_len = cmp::min(prefix.len(), buf.len());
-                prefix.copy_to_slice(&mut buf[..copy_len]);
+                let copy_len = cmp::min(prefix.len(), buf.remaining());
+                // TODO: There should be a way to do following two lines cleaner...
+                buf.put_slice(&prefix[..copy_len]);
+                prefix.advance(copy_len);
                 // Put back whats left
                 if !prefix.is_empty() {
                     self.pre = Some(prefix);
                 }
 
-                return Poll::Ready(Ok(copy_len));
+                return Poll::Ready(Ok(()));
             }
         }
         Pin::new(&mut self.inner).poll_read(cx, buf)
@@ -92,15 +89,6 @@ where
     fn poll_shutdown(mut self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<io::Result<()>> {
         Pin::new(&mut self.inner).poll_shutdown(cx)
     }
-
-    #[inline]
-    fn poll_write_buf<B: Buf>(
-        mut self: Pin<&mut Self>,
-        cx: &mut task::Context<'_>,
-        buf: &mut B,
-    ) -> Poll<io::Result<usize>> {
-        Pin::new(&mut self.inner).poll_write_buf(cx, buf)
-    }
 }
 
 #[cfg(test)]