io: clean up buffer casts (#7142)

tokio-util/Cargo.toml

@@ -35,7 +35,7 @@ __docs_rs = ["futures-util"]
 
 [dependencies]
 tokio = { version = "1.28.0", path = "../tokio", features = ["sync"] }
-bytes = "1.0.0"
+bytes = "1.2.1"
 futures-core = "0.3.0"
 futures-sink = "0.3.0"
 futures-io = { version = "0.3.0", optional = true }

tokio-util/src/udp/frame.rs

@@ -5,13 +5,13 @@ use tokio::{io::ReadBuf, net::UdpSocket};
 
 use bytes::{BufMut, BytesMut};
 use futures_sink::Sink;
+use std::io;
 use std::pin::Pin;
 use std::task::{ready, Context, Poll};
 use std::{
     borrow::Borrow,
     net::{Ipv4Addr, SocketAddr, SocketAddrV4},
 };
-use std::{io, mem::MaybeUninit};
 
 /// A unified [`Stream`] and [`Sink`] interface to an underlying `UdpSocket`, using
 /// the `Encoder` and `Decoder` traits to encode and decode frames.
@@ -83,7 +83,7 @@ where
             let addr = {
                 // Safety: `chunk_mut()` returns a `&mut UninitSlice`, and `UninitSlice` is a
                 // transparent wrapper around `[MaybeUninit<u8>]`.
-                let buf = unsafe { &mut *(pin.rd.chunk_mut() as *mut _ as *mut [MaybeUninit<u8>]) };
+                let buf = unsafe { pin.rd.chunk_mut().as_uninit_slice_mut() };
                 let mut read = ReadBuf::uninit(buf);
                 let ptr = read.filled().as_ptr();
                 let res = ready!(pin.socket.borrow().poll_recv_from(cx, &mut read));
@@ -91,9 +91,10 @@ where
                 assert_eq!(ptr, read.filled().as_ptr());
                 let addr = res?;
 
+                let filled = read.filled().len();
                 // Safety: This is guaranteed to be the number of initialized (and read) bytes due
                 // to the invariants provided by `ReadBuf::filled`.
-                unsafe { pin.rd.advance_mut(read.filled().len()) };
+                unsafe { pin.rd.advance_mut(filled) };
 
                 addr
             };

tokio-util/src/util/poll_buf.rs

@@ -2,7 +2,6 @@ use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
 
 use bytes::{Buf, BufMut};
 use std::io::{self, IoSlice};
-use std::mem::MaybeUninit;
 use std::pin::Pin;
 use std::task::{ready, Context, Poll};
 
@@ -59,7 +58,7 @@ pub fn poll_read_buf<T: AsyncRead + ?Sized, B: BufMut>(
 
         // Safety: `chunk_mut()` returns a `&mut UninitSlice`, and `UninitSlice` is a
         // transparent wrapper around `[MaybeUninit<u8>]`.
-        let dst = unsafe { &mut *(dst as *mut _ as *mut [MaybeUninit<u8>]) };
+        let dst = unsafe { dst.as_uninit_slice_mut() };
         let mut buf = ReadBuf::uninit(dst);
         let ptr = buf.filled().as_ptr();
         ready!(io.poll_read(cx, &mut buf)?);

tokio/Cargo.toml

@@ -91,7 +91,7 @@ tokio-macros = { version = "~2.5.0", path = "../tokio-macros", optional = true }
 pin-project-lite = "0.2.11"
 
 # Everything else is optional...
-bytes = { version = "1.1.0", optional = true }
+bytes = { version = "1.2.1", optional = true }
 mio = { version = "1.0.1", optional = true, default-features = false }
 parking_lot = { version = "0.12.0", optional = true }
 

tokio/src/io/util/read_buf.rs

@@ -41,7 +41,6 @@ where
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
         use crate::io::ReadBuf;
-        use std::mem::MaybeUninit;
 
         let me = self.project();
 
@@ -51,7 +50,7 @@ where
 
         let n = {
             let dst = me.buf.chunk_mut();
-            let dst = unsafe { &mut *(dst as *mut _ as *mut [MaybeUninit<u8>]) };
+            let dst = unsafe { dst.as_uninit_slice_mut() };
             let mut buf = ReadBuf::uninit(dst);
             let ptr = buf.filled().as_ptr();
             ready!(Pin::new(me.reader).poll_read(cx, &mut buf)?);