36 lines
1.4 KiB
Rust
36 lines
1.4 KiB
Rust
#![allow(dead_code)]
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use core::{mem::MaybeUninit, ptr};
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/// Polyfill for `maybe_uninit_slice` feature's
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/// `MaybeUninit::slice_assume_init_mut`. Every element of `slice` must have
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/// been initialized.
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#[inline(always)]
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pub unsafe fn slice_assume_init_mut<T>(slice: &mut [MaybeUninit<T>]) -> &mut [T] {
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// SAFETY: `MaybeUninit<T>` is guaranteed to be layout-compatible with `T`.
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&mut *(slice as *mut [MaybeUninit<T>] as *mut [T])
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}
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#[inline]
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pub fn uninit_slice_fill_zero(slice: &mut [MaybeUninit<u8>]) -> &mut [u8] {
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unsafe { ptr::write_bytes(slice.as_mut_ptr(), 0, slice.len()) };
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unsafe { slice_assume_init_mut(slice) }
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}
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#[inline(always)]
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pub fn slice_as_uninit<T>(slice: &[T]) -> &[MaybeUninit<T>] {
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// SAFETY: `MaybeUninit<T>` is guaranteed to be layout-compatible with `T`.
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// There is no risk of writing a `MaybeUninit<T>` into the result since
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// the result isn't mutable.
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unsafe { &*(slice as *const [T] as *const [MaybeUninit<T>]) }
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}
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/// View an mutable initialized array as potentially-uninitialized.
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///
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/// This is unsafe because it allows assigning uninitialized values into
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/// `slice`, which would be undefined behavior.
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#[inline(always)]
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pub unsafe fn slice_as_uninit_mut<T>(slice: &mut [T]) -> &mut [MaybeUninit<T>] {
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// SAFETY: `MaybeUninit<T>` is guaranteed to be layout-compatible with `T`.
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&mut *(slice as *mut [T] as *mut [MaybeUninit<T>])
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}
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