From 1b6a04ca5504955c571d1c97504fb45ea0befee4 Mon Sep 17 00:00:00 2001 From: Valentin Popov Date: Mon, 8 Jan 2024 01:21:28 +0400 Subject: Initial vendor packages Signed-off-by: Valentin Popov --- vendor/bytemuck/src/no_uninit.rs | 80 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 vendor/bytemuck/src/no_uninit.rs (limited to 'vendor/bytemuck/src/no_uninit.rs') diff --git a/vendor/bytemuck/src/no_uninit.rs b/vendor/bytemuck/src/no_uninit.rs new file mode 100644 index 0000000..5fda0c9 --- /dev/null +++ b/vendor/bytemuck/src/no_uninit.rs @@ -0,0 +1,80 @@ +use crate::Pod; +use core::num::{ + NonZeroI128, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI8, NonZeroIsize, + NonZeroU128, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU8, NonZeroUsize, +}; + +/// Marker trait for "plain old data" types with no uninit (or padding) bytes. +/// +/// The requirements for this is very similar to [`Pod`], +/// except that it doesn't require that all bit patterns of the type are valid, +/// i.e. it does not require the type to be [`Zeroable`][crate::Zeroable]. +/// This limits what you can do with a type of this kind, but also broadens the +/// included types to things like C-style enums. Notably, you can only cast from +/// *immutable* references to a [`NoUninit`] type into *immutable* references of +/// any other type, no casting of mutable references or mutable references to +/// slices etc. +/// +/// [`Pod`] is a subset of [`NoUninit`], meaning that any `T: Pod` is also +/// [`NoUninit`] but any `T: NoUninit` is not necessarily [`Pod`]. If possible, +/// prefer implementing [`Pod`] directly. To get more [`Pod`]-like functionality +/// for a type that is only [`NoUninit`], consider also implementing +/// [`CheckedBitPattern`][crate::CheckedBitPattern]. +/// +/// # Derive +/// +/// A `#[derive(NoUninit)]` macro is provided under the `derive` feature flag +/// which will automatically validate the requirements of this trait and +/// implement the trait for you for both enums and structs. This is the +/// recommended method for implementing the trait, however it's also possible to +/// do manually. If you implement it manually, you *must* carefully follow the +/// below safety rules. +/// +/// # Safety +/// +/// The same as [`Pod`] except we disregard the rule about it must +/// allow any bit pattern (i.e. it does not need to be +/// [`Zeroable`][crate::Zeroable]). Still, this is a quite strong guarantee +/// about a type, so *be careful* whem implementing it manually. +/// +/// * The type must be inhabited (eg: no +/// [Infallible](core::convert::Infallible)). +/// * The type must not contain any uninit (or padding) bytes, either in the +/// middle or on the end (eg: no `#[repr(C)] struct Foo(u8, u16)`, which has +/// padding in the middle, and also no `#[repr(C)] struct Foo(u16, u8)`, which +/// has padding on the end). +/// * Structs need to have all fields also be `NoUninit`. +/// * Structs need to be `repr(C)` or `repr(transparent)`. In the case of +/// `repr(C)`, the `packed` and `align` repr modifiers can be used as long as +/// all other rules end up being followed. +/// * Enums need to have an explicit `#[repr(Int)]` +/// * Enums must have only fieldless variants +/// * It is disallowed for types to contain pointer types, `Cell`, `UnsafeCell`, +/// atomics, and any other forms of interior mutability. +/// * More precisely: A shared reference to the type must allow reads, and +/// *only* reads. RustBelt's separation logic is based on the notion that a +/// type is allowed to define a sharing predicate, its own invariant that must +/// hold for shared references, and this predicate is the reasoning that allow +/// it to deal with atomic and cells etc. We require the sharing predicate to +/// be trivial and permit only read-only access. +/// * There's probably more, don't mess it up (I mean it). +pub unsafe trait NoUninit: Sized + Copy + 'static {} + +unsafe impl NoUninit for T {} + +unsafe impl NoUninit for char {} + +unsafe impl NoUninit for bool {} + +unsafe impl NoUninit for NonZeroU8 {} +unsafe impl NoUninit for NonZeroI8 {} +unsafe impl NoUninit for NonZeroU16 {} +unsafe impl NoUninit for NonZeroI16 {} +unsafe impl NoUninit for NonZeroU32 {} +unsafe impl NoUninit for NonZeroI32 {} +unsafe impl NoUninit for NonZeroU64 {} +unsafe impl NoUninit for NonZeroI64 {} +unsafe impl NoUninit for NonZeroU128 {} +unsafe impl NoUninit for NonZeroI128 {} +unsafe impl NoUninit for NonZeroUsize {} +unsafe impl NoUninit for NonZeroIsize {} -- cgit v1.2.3