| 1 | #![ allow(dead_code)] | 
| 2 | use crate::Error; | 
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| 3 | use core::{mem::MaybeUninit, ptr, slice}; | 
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| 4 |  | 
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| 5 | /// Polyfill for `maybe_uninit_slice` feature's | 
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| 6 | /// `MaybeUninit::slice_assume_init_mut`. Every element of `slice` must have | 
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| 7 | /// been initialized. | 
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| 8 | #[ inline(always)] | 
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| 9 | #[ allow(unused_unsafe)] // TODO(MSRV 1.65): Remove this. | 
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| 10 | pub unsafe fn slice_assume_init_mut<T>(slice: &mut [MaybeUninit<T>]) -> &mut [T] { | 
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| 11 | let ptr: *mut [T] = ptr_from_mut::<[MaybeUninit<T>]>(slice) as *mut [T]; | 
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| 12 | // SAFETY: `MaybeUninit<T>` is guaranteed to be layout-compatible with `T`. | 
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| 13 | unsafe { &mut *ptr } | 
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| 14 | } | 
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| 15 |  | 
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| 16 | #[ inline] | 
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| 17 | pub fn uninit_slice_fill_zero(slice: &mut [MaybeUninit<u8>]) -> &mut [u8] { | 
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| 18 | unsafe { ptr::write_bytes(dst:slice.as_mut_ptr(), val:0, count:slice.len()) }; | 
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| 19 | unsafe { slice_assume_init_mut(slice) } | 
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| 20 | } | 
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| 21 |  | 
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| 22 | #[ inline(always)] | 
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| 23 | pub fn slice_as_uninit<T>(slice: &[T]) -> &[MaybeUninit<T>] { | 
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| 24 | let ptr: *const [MaybeUninit] = ptr_from_ref::<[T]>(slice) as *const [MaybeUninit<T>]; | 
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| 25 | // SAFETY: `MaybeUninit<T>` is guaranteed to be layout-compatible with `T`. | 
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| 26 | unsafe { &*ptr } | 
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| 27 | } | 
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| 28 |  | 
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| 29 | /// View an mutable initialized array as potentially-uninitialized. | 
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| 30 | /// | 
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| 31 | /// This is unsafe because it allows assigning uninitialized values into | 
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| 32 | /// `slice`, which would be undefined behavior. | 
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| 33 | #[ inline(always)] | 
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| 34 | #[ allow(unused_unsafe)] // TODO(MSRV 1.65): Remove this. | 
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| 35 | pub unsafe fn slice_as_uninit_mut<T>(slice: &mut [T]) -> &mut [MaybeUninit<T>] { | 
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| 36 | let ptr: *mut [MaybeUninit] = ptr_from_mut::<[T]>(slice) as *mut [MaybeUninit<T>]; | 
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| 37 | // SAFETY: `MaybeUninit<T>` is guaranteed to be layout-compatible with `T`. | 
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| 38 | unsafe { &mut *ptr } | 
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| 39 | } | 
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| 40 |  | 
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| 41 | // TODO: MSRV(1.76.0): Replace with `core::ptr::from_mut`. | 
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| 42 | fn ptr_from_mut<T: ?Sized>(r: &mut T) -> *mut T { | 
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| 43 | r | 
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| 44 | } | 
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| 45 |  | 
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| 46 | // TODO: MSRV(1.76.0): Replace with `core::ptr::from_ref`. | 
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| 47 | fn ptr_from_ref<T: ?Sized>(r: &T) -> *const T { | 
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| 48 | r | 
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| 49 | } | 
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| 50 |  | 
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| 51 | /// Default implementation of `inner_u32` on top of `fill_uninit` | 
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| 52 | pub fn inner_u32() -> Result<u32, Error> { | 
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| 53 | let mut res: MaybeUninit = MaybeUninit::<u32>::uninit(); | 
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| 54 | // SAFETY: the created slice has the same size as `res` | 
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| 55 | let dst: &mut [MaybeUninit] = unsafe { | 
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| 56 | let p: *mut MaybeUninit<u8> = res.as_mut_ptr().cast(); | 
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| 57 | slice::from_raw_parts_mut(data:p, len:core::mem::size_of::<u32>()) | 
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| 58 | }; | 
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| 59 | crate::fill_uninit(dest:dst)?; | 
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| 60 | // SAFETY: `dst` has been fully initialized by `imp::fill_inner` | 
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| 61 | // since it returned `Ok`. | 
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| 62 | Ok(unsafe { res.assume_init() }) | 
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| 63 | } | 
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| 64 |  | 
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| 65 | /// Default implementation of `inner_u64` on top of `fill_uninit` | 
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| 66 | pub fn inner_u64() -> Result<u64, Error> { | 
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| 67 | let mut res: MaybeUninit = MaybeUninit::<u64>::uninit(); | 
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| 68 | // SAFETY: the created slice has the same size as `res` | 
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| 69 | let dst: &mut [MaybeUninit] = unsafe { | 
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| 70 | let p: *mut MaybeUninit<u8> = res.as_mut_ptr().cast(); | 
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| 71 | slice::from_raw_parts_mut(data:p, len:core::mem::size_of::<u64>()) | 
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| 72 | }; | 
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| 73 | crate::fill_uninit(dest:dst)?; | 
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| 74 | // SAFETY: `dst` has been fully initialized by `imp::fill_inner` | 
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| 75 | // since it returned `Ok`. | 
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| 76 | Ok(unsafe { res.assume_init() }) | 
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| 77 | } | 
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| 78 |  | 
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| 79 | /// Truncates `u64` and returns the lower 32 bits as `u32` | 
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| 80 | pub(crate) fn truncate(val: u64) -> u32 { | 
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| 81 | u32::try_from(val & u64::from(u32::MAX)).expect(msg: "The higher 32 bits are masked") | 
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| 82 | } | 
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| 83 |  | 
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