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//! Utilities having to do with pinning. I sure hope these are sound!
use contracts::requires;
use core::pin::Pin;
use std::ptr::NonNull;
/// Iterates over projections of elements out of a pinned slice.
pub fn pin_project_slice_mut_iter<T>(
mut slice: Pin<&mut [T]>,
) -> impl Iterator<Item = Pin<&mut T>> {
// SAFETY: We never move out of this pointer.
let base_ptr: NonNull<T> = NonNull::from(unsafe { slice.as_mut().get_unchecked_mut() }).cast();
(0..slice.len()).map(move |i| {
// SAFETY: This is in-bounds, since the original slice was valid. No other references to
// the data can exist, since we visit each index once and have an exclusive borrow on the
// slice.
let ptr = unsafe { base_ptr.add(i).as_mut() };
// SAFETY: This is not certainly sound; see https://github.com/rust-lang/rust/issues/104108
unsafe { Pin::new_unchecked(ptr) }
})
}
/// Projects a single element out of a pinned slice.
#[requires(index < slice.len())]
pub fn pin_project_slice_mut<T>(slice: Pin<&mut [T]>, index: usize) -> Pin<&mut T> {
// SAFETY: This is not certainly sound; see https://github.com/rust-lang/rust/issues/104108
unsafe { slice.map_unchecked_mut(|slice| &mut slice[index]) }
}
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