Specialize many implementations of `Read::read_buf_exact`

1 files changed, 24 insertions, 0 deletions

diff --git a/library/std/src/io/impls.rs b/library/std/src/io/impls.rs
index cb972abd2b8..ee7ed4bcc9a 100644
--- a/library/std/src/io/impls.rs
+++ b/library/std/src/io/impls.rs
@@ -50,6 +50,10 @@ impl<R: Read + ?Sized> Read for &mut R {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         (**self).read_exact(buf)
     }
+    #[inline]
+    fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
+        (**self).read_buf_exact(cursor)
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write + ?Sized> Write for &mut W {
@@ -154,6 +158,10 @@ impl<R: Read + ?Sized> Read for Box<R> {
     fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<()> {
         (**self).read_exact(buf)
     }
+    #[inline]
+    fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> io::Result<()> {
+        (**self).read_buf_exact(cursor)
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<W: Write + ?Sized> Write for Box<W> {
@@ -302,6 +310,22 @@ impl Read for &[u8] {
     }
 
     #[inline]
+    fn read_buf_exact(&mut self, mut cursor: BorrowedCursor<'_>) -> io::Result<()> {
+        if cursor.capacity() > self.len() {
+            return Err(io::const_io_error!(
+                ErrorKind::UnexpectedEof,
+                "failed to fill whole buffer"
+            ));
+        }
+        let (a, b) = self.split_at(cursor.capacity());
+
+        cursor.append(a);
+
+        *self = b;
+        Ok(())
+    }
+
+    #[inline]
     fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
         let len = self.len();
         buf.try_reserve(len)?;