1 | //! Miscellaneous minor utilities. |
2 | |
3 | #![allow (dead_code)] |
4 | #![allow (unused_macros)] |
5 | |
6 | use core::ffi::c_void; |
7 | use core::mem::{align_of, size_of}; |
8 | use core::ptr::{null, null_mut, NonNull}; |
9 | |
10 | /// Convert a `&T` into a `*const T` without using an `as`. |
11 | #[inline ] |
12 | pub(crate) const fn as_ptr<T>(t: &T) -> *const T { |
13 | t |
14 | } |
15 | |
16 | /// Convert a `&mut T` into a `*mut T` without using an `as`. |
17 | #[inline ] |
18 | pub(crate) fn as_mut_ptr<T>(t: &mut T) -> *mut T { |
19 | t |
20 | } |
21 | |
22 | /// Convert an `Option<&T>` into a possibly-null `*const T`. |
23 | #[inline ] |
24 | pub(crate) const fn option_as_ptr<T>(t: Option<&T>) -> *const T { |
25 | match t { |
26 | Some(t: &T) => t, |
27 | None => null(), |
28 | } |
29 | } |
30 | |
31 | /// Convert an `Option<&mut T>` into a possibly-null `*mut T`. |
32 | #[inline ] |
33 | pub(crate) fn option_as_mut_ptr<T>(t: Option<&mut T>) -> *mut T { |
34 | match t { |
35 | Some(t: &mut T) => t, |
36 | None => null_mut(), |
37 | } |
38 | } |
39 | |
40 | /// Convert a `*mut c_void` to a `*mut T`, checking that it is not null, |
41 | /// misaligned, or pointing to a region of memory that wraps around the address |
42 | /// space. |
43 | pub(crate) fn check_raw_pointer<T>(value: *mut c_void) -> Option<NonNull<T>> { |
44 | if (value as usize).checked_add(size_of::<T>()).is_none() |
45 | || (value as usize) % align_of::<T>() != 0 |
46 | { |
47 | return None; |
48 | } |
49 | |
50 | NonNull::new(ptr:value.cast()) |
51 | } |
52 | |
53 | /// Create an array value containing all default values, inferring the type. |
54 | #[inline ] |
55 | pub(crate) fn default_array<T: Default + Copy, const N: usize>() -> [T; N] { |
56 | [T::default(); N] |
57 | } |
58 | |
59 | /// Create a union value containing a default value in one of its arms. |
60 | /// |
61 | /// The field names a union field which must have the same size as the union |
62 | /// itself. |
63 | macro_rules! default_union { |
64 | ($union:ident, $field:ident) => {{ |
65 | let u = $union { |
66 | $field: Default::default(), |
67 | }; |
68 | |
69 | // Assert that the given field initializes the whole union. |
70 | #[cfg(test)] |
71 | unsafe { |
72 | let field_value = u.$field; |
73 | assert_eq!( |
74 | core::mem::size_of_val(&u), |
75 | core::mem::size_of_val(&field_value) |
76 | ); |
77 | const_assert_eq!(memoffset::offset_of_union!($union, $field), 0); |
78 | } |
79 | |
80 | u |
81 | }}; |
82 | } |
83 | |