Add as_slice/into_slice for IoSlice/IoSliceMut.

library/std/src/io/mod.rs

@@ -1340,6 +1340,25 @@ impl<'a> IoSliceMut<'a> {
             bufs[0].advance(left);
         }
     }
+
+    /// Get the underlying bytes as a mutable slice with the original lifetime.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(io_slice_as_bytes)]
+    /// use std::io::IoSliceMut;
+    ///
+    /// let mut data = *b"abcdef";
+    /// let io_slice = IoSliceMut::new(&mut data);
+    /// io_slice.into_slice()[0] = b'A';
+    ///
+    /// assert_eq!(&data, b"Abcdef");
+    /// ```
+    #[unstable(feature = "io_slice_as_bytes", issue = "132818")]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        self.0.into_slice()
+    }
 }
 
 #[stable(feature = "iovec", since = "1.36.0")]
@@ -1482,6 +1501,32 @@ impl<'a> IoSlice<'a> {
             bufs[0].advance(left);
         }
     }
+
+    /// Get the underlying bytes as a slice with the original lifetime.
+    ///
+    /// This doesn't borrow from `self`, so is less restrictive than calling
+    /// `.deref()`, which does.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(io_slice_as_bytes)]
+    /// use std::io::IoSlice;
+    ///
+    /// let data = b"abcdef";
+    ///
+    /// let mut io_slice = IoSlice::new(data);
+    /// let tail = &io_slice.as_slice()[3..];
+    ///
+    /// // This works because `tail` doesn't borrow `io_slice`
+    /// io_slice = IoSlice::new(tail);
+    ///
+    /// assert_eq!(io_slice.as_slice(), b"def");
+    /// ```
+    #[unstable(feature = "io_slice_as_bytes", issue = "132818")]
+    pub const fn as_slice(self) -> &'a [u8] {
+        self.0.as_slice()
+    }
 }
 
 #[stable(feature = "iovec", since = "1.36.0")]

library/std/src/io/tests.rs

@@ -531,6 +531,20 @@ fn io_slice_advance_slices_beyond_total_length() {
     assert!(bufs.is_empty());
 }
 
+#[test]
+fn io_slice_as_slice() {
+    let buf = [1; 8];
+    let slice = IoSlice::new(&buf).as_slice();
+    assert_eq!(slice, buf);
+}
+
+#[test]
+fn io_slice_into_slice() {
+    let mut buf = [1; 8];
+    let slice = IoSliceMut::new(&mut buf).into_slice();
+    assert_eq!(slice, [1; 8]);
+}
+
 /// Creates a new writer that reads from at most `n_bufs` and reads
 /// `per_call` bytes (in total) per call to write.
 fn test_writer(n_bufs: usize, per_call: usize) -> TestWriter {

library/std/src/sys/pal/hermit/io.rs

@@ -33,7 +33,7 @@ impl<'a> IoSlice<'a> {
     }
 
     #[inline]
-    pub fn as_slice(&self) -> &[u8] {
+    pub const fn as_slice(&self) -> &'a [u8] {
         unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 }
@@ -70,6 +70,11 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 
+    #[inline]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+    }
+
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
         unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }

library/std/src/sys/pal/solid/io.rs

@@ -33,7 +33,7 @@ impl<'a> IoSlice<'a> {
     }
 
     #[inline]
-    pub fn as_slice(&self) -> &[u8] {
+    pub const fn as_slice(&self) -> &'a [u8] {
         unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 }
@@ -70,6 +70,11 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 
+    #[inline]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+    }
+
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
         unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }

library/std/src/sys/pal/unix/io.rs

@@ -33,7 +33,7 @@ impl<'a> IoSlice<'a> {
     }
 
     #[inline]
-    pub fn as_slice(&self) -> &[u8] {
+    pub const fn as_slice(&self) -> &'a [u8] {
         unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 }
@@ -70,6 +70,11 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 
+    #[inline]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+    }
+
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
         unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }

library/std/src/sys/pal/unsupported/io.rs

@@ -15,7 +15,7 @@ impl<'a> IoSlice<'a> {
     }
 
     #[inline]
-    pub fn as_slice(&self) -> &[u8] {
+    pub const fn as_slice(&self) -> &'a [u8] {
         self.0
     }
 }
@@ -40,6 +40,11 @@ impl<'a> IoSliceMut<'a> {
         self.0
     }
 
+    #[inline]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        self.0
+    }
+
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
         self.0

library/std/src/sys/pal/wasi/io.rs

@@ -30,7 +30,7 @@ impl<'a> IoSlice<'a> {
     }
 
     #[inline]
-    pub fn as_slice(&self) -> &[u8] {
+    pub const fn as_slice(&self) -> &'a [u8] {
         unsafe { slice::from_raw_parts(self.vec.buf as *const u8, self.vec.buf_len) }
     }
 }
@@ -67,6 +67,11 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts(self.vec.buf as *const u8, self.vec.buf_len) }
     }
 
+    #[inline]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.buf as *mut u8, self.vec.buf_len) }
+    }
+
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
         unsafe { slice::from_raw_parts_mut(self.vec.buf as *mut u8, self.vec.buf_len) }

library/std/src/sys/pal/windows/io.rs

@@ -36,7 +36,7 @@ impl<'a> IoSlice<'a> {
     }
 
     #[inline]
-    pub fn as_slice(&self) -> &[u8] {
+    pub const fn as_slice(&self) -> &'a [u8] {
         unsafe { slice::from_raw_parts(self.vec.buf, self.vec.len as usize) }
     }
 }
@@ -74,6 +74,11 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts(self.vec.buf, self.vec.len as usize) }
     }
 
+    #[inline]
+    pub const fn into_slice(self) -> &'a mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.vec.buf, self.vec.len as usize) }
+    }
+
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
         unsafe { slice::from_raw_parts_mut(self.vec.buf, self.vec.len as usize) }