refactor: improve the code for connection recycling

This avoids unnecessarily registering with the waker when we aren't going to poll until Ready.

Thanks to Kestrer on discord.

src/h1/mod.rs

@@ -19,8 +19,6 @@ cfg_if::cfg_if! {
 
 use super::{async_trait, Error, HttpClient, Request, Response};
 
-pub(crate) mod utils;
-
 mod tcp;
 #[cfg(any(feature = "native-tls", feature = "rustls"))]
 mod tls;

src/h1/tcp.rs

@@ -8,8 +8,6 @@ use deadpool::managed::{Manager, Object, RecycleResult};
 use futures::io::{AsyncRead, AsyncWrite};
 use futures::task::{Context, Poll};
 
-use super::utils::PollRead;
-
 #[derive(Clone, Debug)]
 pub(crate) struct TcpConnection {
     addr: SocketAddr,
@@ -65,7 +63,8 @@ impl Manager<TcpStream, std::io::Error> for TcpConnection {
 
     async fn recycle(&self, conn: &mut TcpStream) -> RecycleResult<std::io::Error> {
         let mut buf = [0; 4];
-        match PollRead::new(conn, &mut buf).await {
+        let mut cx = Context::from_waker(futures::task::noop_waker_ref());
+        match Pin::new(conn).poll_read(&mut cx, &mut buf) {
             Poll::Ready(Err(error)) => Err(error),
             Poll::Ready(Ok(bytes)) if bytes == 0 => Err(std::io::Error::new(
                 std::io::ErrorKind::UnexpectedEof,

src/h1/tls.rs

@@ -8,8 +8,6 @@ use deadpool::managed::{Manager, Object, RecycleResult};
 use futures::io::{AsyncRead, AsyncWrite};
 use futures::task::{Context, Poll};
 
-use super::utils::PollRead;
-
 cfg_if::cfg_if! {
     if #[cfg(feature = "rustls")] {
         use async_tls::client::TlsStream;
@@ -78,7 +76,8 @@ impl Manager<TlsStream<TcpStream>, Error> for TlsConnection {
 
     async fn recycle(&self, conn: &mut TlsStream<TcpStream>) -> RecycleResult<Error> {
         let mut buf = [0; 4];
-        match PollRead::new(conn, &mut buf).await {
+        let mut cx = Context::from_waker(futures::task::noop_waker_ref());
+        match Pin::new(conn).poll_read(&mut cx, &mut buf) {
             Poll::Ready(Err(error)) => Err(error),
             Poll::Ready(Ok(bytes)) if bytes == 0 => Err(std::io::Error::new(
                 std::io::ErrorKind::UnexpectedEof,

src/h1/utils.rs

@@ -1,31 +0,0 @@
-use std::io;
-use std::pin::Pin;
-
-use futures::future::Future;
-use futures::io::AsyncRead;
-use futures::task::{Context, Poll};
-
-/// Like the `futures::io::Read` future, but returning the underlying `futures::task::Poll`.
-#[derive(Debug)]
-#[must_use = "futures do nothing unless you `.await` or poll them"]
-pub(crate) struct PollRead<'a, R: ?Sized> {
-    reader: &'a mut R,
-    buf: &'a mut [u8],
-}
-
-impl<R: ?Sized + Unpin> Unpin for PollRead<'_, R> {}
-
-impl<'a, R: AsyncRead + ?Sized + Unpin> PollRead<'a, R> {
-    pub(super) fn new(reader: &'a mut R, buf: &'a mut [u8]) -> Self {
-        Self { reader, buf }
-    }
-}
-
-impl<R: AsyncRead + ?Sized + Unpin> Future for PollRead<'_, R> {
-    type Output = Poll<io::Result<usize>>;
-
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
-        let this = &mut *self;
-        Poll::Ready(Pin::new(&mut this.reader).poll_read(cx, this.buf))
-    }
-}