bytemuck/
pod.rs

1use super::*;
2
3/// Marker trait for "plain old data".
4///
5/// The point of this trait is that once something is marked "plain old data"
6/// you can really go to town with the bit fiddling and bit casting. Therefore,
7/// it's a relatively strong claim to make about a type. Do not add this to your
8/// type casually.
9///
10/// **Reminder:** The results of casting around bytes between data types are
11/// _endian dependant_. Little-endian machines are the most common, but
12/// big-endian machines do exist (and big-endian is also used for "network
13/// order" bytes).
14///
15/// ## Safety
16///
17/// * The type must be inhabited (eg: no
18///   [Infallible](core::convert::Infallible)).
19/// * The type must allow any bit pattern (eg: no `bool` or `char`, which have
20///   illegal bit patterns).
21/// * The type must not contain any uninit (or padding) bytes, either in the
22///   middle or on the end (eg: no `#[repr(C)] struct Foo(u8, u16)`, which has
23///   padding in the middle, and also no `#[repr(C)] struct Foo(u16, u8)`, which
24///   has padding on the end).
25/// * The type needs to have all fields also be `Pod`.
26/// * The type needs to be `repr(C)` or `repr(transparent)`. In the case of
27///   `repr(C)`, the `packed` and `align` repr modifiers can be used as long as
28///   all other rules end up being followed.
29/// * It is disallowed for types to contain pointer types, `Cell`, `UnsafeCell`,
30///   atomics, and any other forms of interior mutability.
31/// * More precisely: A shared reference to the type must allow reads, and
32///   *only* reads. RustBelt's separation logic is based on the notion that a
33///   type is allowed to define a sharing predicate, its own invariant that must
34///   hold for shared references, and this predicate is the reasoning that allow
35///   it to deal with atomic and cells etc. We require the sharing predicate to
36///   be trivial and permit only read-only access.
37pub unsafe trait Pod: Zeroable + Copy + 'static {}
38
39unsafe impl Pod for () {}
40unsafe impl Pod for u8 {}
41unsafe impl Pod for i8 {}
42unsafe impl Pod for u16 {}
43unsafe impl Pod for i16 {}
44unsafe impl Pod for u32 {}
45unsafe impl Pod for i32 {}
46unsafe impl Pod for u64 {}
47unsafe impl Pod for i64 {}
48unsafe impl Pod for usize {}
49unsafe impl Pod for isize {}
50unsafe impl Pod for u128 {}
51unsafe impl Pod for i128 {}
52unsafe impl Pod for f32 {}
53unsafe impl Pod for f64 {}
54unsafe impl<T: Pod> Pod for Wrapping<T> {}
55
56#[cfg(feature = "unsound_ptr_pod_impl")]
57#[cfg_attr(
58  feature = "nightly_docs",
59  doc(cfg(feature = "unsound_ptr_pod_impl"))
60)]
61unsafe impl<T: 'static> Pod for *mut T {}
62#[cfg(feature = "unsound_ptr_pod_impl")]
63#[cfg_attr(
64  feature = "nightly_docs",
65  doc(cfg(feature = "unsound_ptr_pod_impl"))
66)]
67unsafe impl<T: 'static> Pod for *const T {}
68#[cfg(feature = "unsound_ptr_pod_impl")]
69#[cfg_attr(
70  feature = "nightly_docs",
71  doc(cfg(feature = "unsound_ptr_pod_impl"))
72)]
73unsafe impl<T: 'static> PodInOption for NonNull<T> {}
74
75unsafe impl<T: ?Sized + 'static> Pod for PhantomData<T> {}
76unsafe impl Pod for PhantomPinned {}
77unsafe impl<T: Pod> Pod for ManuallyDrop<T> {}
78
79// Note(Lokathor): MaybeUninit can NEVER be Pod.
80
81#[cfg(feature = "min_const_generics")]
82#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "min_const_generics")))]
83unsafe impl<T, const N: usize> Pod for [T; N] where T: Pod {}
84
85#[cfg(not(feature = "min_const_generics"))]
86impl_unsafe_marker_for_array!(
87  Pod, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
88  20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 48, 64, 96, 128, 256,
89  512, 1024, 2048, 4096
90);
91
92impl_unsafe_marker_for_simd!(
93  #[cfg(all(target_arch = "wasm32", feature = "wasm_simd"))]
94  unsafe impl Pod for wasm32::{v128}
95);
96
97impl_unsafe_marker_for_simd!(
98  #[cfg(all(target_arch = "aarch64", feature = "aarch64_simd"))]
99  unsafe impl Pod for aarch64::{
100    float32x2_t, float32x2x2_t, float32x2x3_t, float32x2x4_t, float32x4_t,
101    float32x4x2_t, float32x4x3_t, float32x4x4_t, float64x1_t, float64x1x2_t,
102    float64x1x3_t, float64x1x4_t, float64x2_t, float64x2x2_t, float64x2x3_t,
103    float64x2x4_t, int16x4_t, int16x4x2_t, int16x4x3_t, int16x4x4_t, int16x8_t,
104    int16x8x2_t, int16x8x3_t, int16x8x4_t, int32x2_t, int32x2x2_t, int32x2x3_t,
105    int32x2x4_t, int32x4_t, int32x4x2_t, int32x4x3_t, int32x4x4_t, int64x1_t,
106    int64x1x2_t, int64x1x3_t, int64x1x4_t, int64x2_t, int64x2x2_t, int64x2x3_t,
107    int64x2x4_t, int8x16_t, int8x16x2_t, int8x16x3_t, int8x16x4_t, int8x8_t,
108    int8x8x2_t, int8x8x3_t, int8x8x4_t, poly16x4_t, poly16x4x2_t, poly16x4x3_t,
109    poly16x4x4_t, poly16x8_t, poly16x8x2_t, poly16x8x3_t, poly16x8x4_t,
110    poly64x1_t, poly64x1x2_t, poly64x1x3_t, poly64x1x4_t, poly64x2_t,
111    poly64x2x2_t, poly64x2x3_t, poly64x2x4_t, poly8x16_t, poly8x16x2_t,
112    poly8x16x3_t, poly8x16x4_t, poly8x8_t, poly8x8x2_t, poly8x8x3_t, poly8x8x4_t,
113    uint16x4_t, uint16x4x2_t, uint16x4x3_t, uint16x4x4_t, uint16x8_t,
114    uint16x8x2_t, uint16x8x3_t, uint16x8x4_t, uint32x2_t, uint32x2x2_t,
115    uint32x2x3_t, uint32x2x4_t, uint32x4_t, uint32x4x2_t, uint32x4x3_t,
116    uint32x4x4_t, uint64x1_t, uint64x1x2_t, uint64x1x3_t, uint64x1x4_t,
117    uint64x2_t, uint64x2x2_t, uint64x2x3_t, uint64x2x4_t, uint8x16_t,
118    uint8x16x2_t, uint8x16x3_t, uint8x16x4_t, uint8x8_t, uint8x8x2_t,
119    uint8x8x3_t, uint8x8x4_t,
120  }
121);
122
123impl_unsafe_marker_for_simd!(
124  #[cfg(target_arch = "x86")]
125  unsafe impl Pod for x86::{
126    __m128i, __m128, __m128d,
127    __m256i, __m256, __m256d,
128  }
129);
130
131impl_unsafe_marker_for_simd!(
132  #[cfg(target_arch = "x86_64")]
133  unsafe impl Pod for x86_64::{
134    __m128i, __m128, __m128d,
135    __m256i, __m256, __m256d,
136  }
137);
138
139#[cfg(feature = "nightly_portable_simd")]
140#[cfg_attr(
141  feature = "nightly_docs",
142  doc(cfg(feature = "nightly_portable_simd"))
143)]
144unsafe impl<T, const N: usize> Pod for core::simd::Simd<T, N>
145where
146  T: core::simd::SimdElement + Pod,
147  core::simd::LaneCount<N>: core::simd::SupportedLaneCount,
148{
149}
150
151impl_unsafe_marker_for_simd!(
152  #[cfg(all(target_arch = "x86", feature = "nightly_stdsimd"))]
153  unsafe impl Pod for x86::{
154    __m128bh, __m256bh, __m512,
155    __m512bh, __m512d, __m512i,
156  }
157);
158
159impl_unsafe_marker_for_simd!(
160  #[cfg(all(target_arch = "x86_64", feature = "nightly_stdsimd"))]
161  unsafe impl Pod for x86_64::{
162    __m128bh, __m256bh, __m512,
163    __m512bh, __m512d, __m512i,
164  }
165);
bytemuck/pod.rs

bytemuck/
pod.rs
