1 files changed, 50 insertions, 17 deletions

diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 604b795cd..7d70a0bac 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -317,6 +317,7 @@ pub use self::stdio::set_output_capture;
 #[stable(feature = "is_terminal", since = "1.70.0")]
 pub use self::stdio::IsTerminal;
 #[unstable(feature = "print_internals", issue = "none")]
+#[doc(hidden)]
 pub use self::stdio::{_eprint, _print};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::{
@@ -329,7 +330,7 @@ pub use self::{
 };
 
 #[unstable(feature = "read_buf", issue = "78485")]
-pub use self::readbuf::{BorrowedBuf, BorrowedCursor};
+pub use core::io::{BorrowedBuf, BorrowedCursor};
 pub(crate) use error::const_io_error;
 
 mod buffered;
@@ -338,7 +339,6 @@ mod cursor;
 mod error;
 mod impls;
 pub mod prelude;
-mod readbuf;
 mod stdio;
 mod util;
 
@@ -513,8 +513,7 @@ pub(crate) fn default_read_exact<R: Read + ?Sized>(this: &mut R, mut buf: &mut [
         match this.read(buf) {
             Ok(0) => break,
             Ok(n) => {
-                let tmp = buf;
-                buf = &mut tmp[n..];
+                buf = &mut buf[n..];
             }
             Err(ref e) if e.is_interrupted() => {}
             Err(e) => return Err(e),
@@ -1141,10 +1140,10 @@ pub fn read_to_string<R: Read>(mut reader: R) -> Result<String> {
 #[repr(transparent)]
 pub struct IoSliceMut<'a>(sys::io::IoSliceMut<'a>);
 
-#[stable(feature = "iovec-send-sync", since = "1.44.0")]
+#[stable(feature = "iovec_send_sync", since = "1.44.0")]
 unsafe impl<'a> Send for IoSliceMut<'a> {}
 
-#[stable(feature = "iovec-send-sync", since = "1.44.0")]
+#[stable(feature = "iovec_send_sync", since = "1.44.0")]
 unsafe impl<'a> Sync for IoSliceMut<'a> {}
 
 #[stable(feature = "iovec", since = "1.36.0")]
@@ -1284,10 +1283,10 @@ impl<'a> DerefMut for IoSliceMut<'a> {
 #[repr(transparent)]
 pub struct IoSlice<'a>(sys::io::IoSlice<'a>);
 
-#[stable(feature = "iovec-send-sync", since = "1.44.0")]
+#[stable(feature = "iovec_send_sync", since = "1.44.0")]
 unsafe impl<'a> Send for IoSlice<'a> {}
 
-#[stable(feature = "iovec-send-sync", since = "1.44.0")]
+#[stable(feature = "iovec_send_sync", since = "1.44.0")]
 unsafe impl<'a> Sync for IoSlice<'a> {}
 
 #[stable(feature = "iovec", since = "1.36.0")]
@@ -1830,6 +1829,7 @@ pub trait Write {
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "IoSeek")]
 pub trait Seek {
     /// Seek to an offset, in bytes, in a stream.
     ///
@@ -2777,23 +2777,55 @@ pub struct Bytes<R> {
 impl<R: Read> Iterator for Bytes<R> {
     type Item = Result<u8>;
 
+    // Not `#[inline]`. This function gets inlined even without it, but having
+    // the inline annotation can result in worse code generation. See #116785.
     fn next(&mut self) -> Option<Result<u8>> {
-        let mut byte = 0;
-        loop {
-            return match self.inner.read(slice::from_mut(&mut byte)) {
-                Ok(0) => None,
-                Ok(..) => Some(Ok(byte)),
-                Err(ref e) if e.is_interrupted() => continue,
-                Err(e) => Some(Err(e)),
-            };
-        }
+        SpecReadByte::spec_read_byte(&mut self.inner)
     }
 
+    #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
         SizeHint::size_hint(&self.inner)
     }
 }
 
+/// For the specialization of `Bytes::next`.
+trait SpecReadByte {
+    fn spec_read_byte(&mut self) -> Option<Result<u8>>;
+}
+
+impl<R> SpecReadByte for R
+where
+    Self: Read,
+{
+    #[inline]
+    default fn spec_read_byte(&mut self) -> Option<Result<u8>> {
+        inlined_slow_read_byte(self)
+    }
+}
+
+/// Read a single byte in a slow, generic way. This is used by the default
+/// `spec_read_byte`.
+#[inline]
+fn inlined_slow_read_byte<R: Read>(reader: &mut R) -> Option<Result<u8>> {
+    let mut byte = 0;
+    loop {
+        return match reader.read(slice::from_mut(&mut byte)) {
+            Ok(0) => None,
+            Ok(..) => Some(Ok(byte)),
+            Err(ref e) if e.is_interrupted() => continue,
+            Err(e) => Some(Err(e)),
+        };
+    }
+}
+
+// Used by `BufReader::spec_read_byte`, for which the `inline(ever)` is
+// important.
+#[inline(never)]
+fn uninlined_slow_read_byte<R: Read>(reader: &mut R) -> Option<Result<u8>> {
+    inlined_slow_read_byte(reader)
+}
+
 trait SizeHint {
     fn lower_bound(&self) -> usize;
 
@@ -2893,6 +2925,7 @@ impl<B: BufRead> Iterator for Split<B> {
 /// [`lines`]: BufRead::lines
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
+#[cfg_attr(not(test), rustc_diagnostic_item = "IoLines")]
 pub struct Lines<B> {
     buf: B,
 }