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Build the slice directly in array_chunks_mut

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Review discussion found that the concern about aliasing was overblown,
so we can simplify this to cast from one slice to another directly.
This commit is contained in:
Josh Stone 2020-08-02 10:35:57 -07:00
parent 864a28e01d
commit 21903532ee
1 changed files with 3 additions and 6 deletions
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9
library/core/src/slice/mod.rs
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@ -1067,14 +1067,11 @@ impl<T> [T] {
pub fn array_chunks_mut<const N: usize>(&mut self) -> ArrayChunksMut<'_, T, N> {
assert_ne!(N, 0);
let len = self.len() / N;
let (fst_ptr, snd) = {
// Scope the first slice into a pointer to avoid aliasing the new slice below.
let (fst, snd) = self.split_at_mut(len * N);
(fst.as_mut_ptr(), snd)
};
let (fst, snd) = self.split_at_mut(len * N);
// SAFETY: We cast a slice of `len * N` elements into
// a slice of `len` many `N` elements chunks.
let array_slice: &mut [[T; N]] = unsafe { from_raw_parts_mut(fst_ptr.cast(), len) };
let array_slice: &mut [[T; N]] =
unsafe { from_raw_parts_mut(fst.as_mut_ptr().cast(), len) };
ArrayChunksMut { iter: array_slice.iter_mut(), rem: snd }
}