ringbuf/
utils.rs

1#[cfg(feature = "alloc")]
2use alloc::{boxed::Box, vec::Vec};
3use core::{
4    mem::{self, MaybeUninit},
5    ptr,
6};
7
8// TODO: Remove on `maybe_uninit_uninit_array` stabilization.
9pub fn uninit_array<T, const N: usize>() -> [MaybeUninit<T>; N] {
10    unsafe { MaybeUninit::<[MaybeUninit<T>; N]>::uninit().assume_init() }
11}
12
13// TODO: Remove on `maybe_uninit_slice` stabilization.
14pub unsafe fn slice_as_uninit_mut<T>(slice: &mut [T]) -> &mut [MaybeUninit<T>] {
15    &mut *(slice as *mut [T] as *mut [MaybeUninit<T>])
16}
17
18// TODO: Remove on `maybe_uninit_slice` stabilization.
19pub unsafe fn slice_assume_init_ref<T>(slice: &[MaybeUninit<T>]) -> &[T] {
20    &*(slice as *const [MaybeUninit<T>] as *const [T])
21}
22// TODO: Remove on `maybe_uninit_slice` stabilization.
23pub unsafe fn slice_assume_init_mut<T>(slice: &mut [MaybeUninit<T>]) -> &mut [T] {
24    &mut *(slice as *mut [MaybeUninit<T>] as *mut [T])
25}
26
27// TODO: Remove on `maybe_uninit_write_slice` stabilization.
28pub fn write_slice<'a, T: Copy>(dst: &'a mut [MaybeUninit<T>], src: &[T]) -> &'a mut [T] {
29    let uninit_src: &[MaybeUninit<T>] = unsafe { mem::transmute(src) };
30    dst.copy_from_slice(uninit_src);
31    unsafe { slice_assume_init_mut(dst) }
32}
33
34pub fn move_uninit_slice<T>(dst: &mut [MaybeUninit<T>], src: &[MaybeUninit<T>]) {
35    assert_eq!(dst.len(), src.len());
36    for i in 0..dst.len() {
37        unsafe { *dst.get_unchecked_mut(i) = ptr::read(src.get_unchecked(i) as *const _) };
38    }
39}
40
41pub fn array_to_uninit<T, const N: usize>(value: [T; N]) -> [MaybeUninit<T>; N] {
42    let value = mem::ManuallyDrop::new(value);
43    let ptr = &value as *const _ as *const [MaybeUninit<T>; N];
44    unsafe { ptr.read() }
45}
46
47#[cfg(feature = "alloc")]
48pub fn vec_to_uninit<T>(value: Vec<T>) -> Vec<MaybeUninit<T>> {
49    let value = mem::ManuallyDrop::new(value);
50    let ptr = &value as *const _ as *const Vec<MaybeUninit<T>>;
51    unsafe { ptr.read() }
52}
53
54#[cfg(feature = "alloc")]
55pub fn boxed_slice_to_uninit<T>(value: Box<[T]>) -> Box<[MaybeUninit<T>]> {
56    let value = mem::ManuallyDrop::new(value);
57    let ptr = &value as *const _ as *const Box<[MaybeUninit<T>]>;
58    unsafe { ptr.read() }
59}