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Document missing unsafe blocks

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This commit is contained in:
Lukas Bergdoll 2023-01-23 09:12:25 +01:00
parent f297afa0c9
commit 5eff264533
1 changed files with 12 additions and 4 deletions
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16
library/core/src/slice/sort.rs
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@ -21,6 +21,9 @@ struct InsertionHole<T> {
impl<T> Drop for InsertionHole<T> {
fn drop(&mut self) {
// SAFETY: This is a helper class. Please refer to its usage for correctness. Namely, one
// must be sure that `src` and `dst` does not overlap as required by
// `ptr::copy_nonoverlapping` and are both valid for writes.
unsafe {
ptr::copy_nonoverlapping(self.src, self.dest, 1);
}
@ -88,6 +91,7 @@ unsafe fn insert_head<T, F>(v: &mut [T], is_less: &mut F)
{
debug_assert!(v.len() >= 2);
// SAFETY: caller must ensure v is at least len 2.
unsafe {
if is_less(v.get_unchecked(1), v.get_unchecked(0)) {
let arr_ptr = v.as_mut_ptr();
@ -153,7 +157,8 @@ fn insertion_sort_shift_left<T, F>(v: &mut [T], offset: usize, is_less: &mut F)
// Shift each element of the unsorted region v[i..] as far left as is needed to make v sorted.
for i in offset..len {
// SAFETY: we tested that `offset` must be at least 1, so this loop is only entered if len
// >= 2.
// >= 2. The range is exclusive and we know `i` must be at least 1 so this slice has at
// >least len 2.
unsafe {
insert_tail(&mut v[..=i], is_less);
}
@ -176,9 +181,10 @@ fn insertion_sort_shift_right<T, F>(v: &mut [T], offset: usize, is_less: &mut F)
// Shift each element of the unsorted region v[..i] as far left as is needed to make v sorted.
for i in (0..offset).rev() {
// We ensured that the slice length is always at least 2 long.
// We know that start_found will be at least one less than end,
// and the range is exclusive. Which gives us i always <= (end - 2).
// SAFETY: we tested that `offset` must be at least 1, so this loop is only entered if len
// >= 2.We ensured that the slice length is always at least 2 long. We know that start_found
// will be at least one less than end, and the range is exclusive. Which gives us i always
// <= (end - 2).
unsafe {
insert_head(&mut v[i..len], is_less);
}
@ -1222,6 +1228,8 @@ pub fn merge_sort<T, CmpF, ElemAllocF, ElemDeallocF, RunAllocF, RunDeallocF>(
let left = runs[r];
let right = runs[r + 1];
let merge_slice = &mut v[left.start..right.start + right.len];
// SAFETY: `buf_ptr` must hold enough capacity for the shorter of the two sides, and
// neither side may be on length 0.
unsafe {
merge(merge_slice, left.len, buf_ptr, is_less);
}