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/anybitpattern.rs | 61 ++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) create mode 100644 vendor/bytemuck/src/anybitpattern.rs (limited to 'vendor/bytemuck/src/anybitpattern.rs') diff --git a/vendor/bytemuck/src/anybitpattern.rs b/vendor/bytemuck/src/anybitpattern.rs new file mode 100644 index 0000000..a759738 --- /dev/null +++ b/vendor/bytemuck/src/anybitpattern.rs @@ -0,0 +1,61 @@ +use crate::{Pod, Zeroable}; + +/// Marker trait for "plain old data" types that are valid for any bit pattern. +/// +/// The requirements for this is very similar to [`Pod`], +/// except that the type can allow uninit (or padding) bytes. +/// This limits what you can do with a type of this kind, but also broadens the +/// included types to `repr(C)` `struct`s that contain padding as well as +/// `union`s. Notably, you can only cast *immutable* references and *owned* +/// values into [`AnyBitPattern`] types, not *mutable* references. +/// +/// [`Pod`] is a subset of [`AnyBitPattern`], meaning that any `T: Pod` is also +/// [`AnyBitPattern`] but any `T: AnyBitPattern` is not necessarily [`Pod`]. +/// +/// [`AnyBitPattern`] is a subset of [`Zeroable`], meaning that any `T: +/// AnyBitPattern` is also [`Zeroable`], but any `T: Zeroable` is not +/// necessarily [`AnyBitPattern ] +/// +/// # Derive +/// +/// A `#[derive(AnyBitPattern)]` 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 structs and enums. 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. +/// +/// * *NOTE: even `C-style`, fieldless enums are intentionally **excluded** from +/// this trait, since it is **unsound** for an enum to have a discriminant value +/// that is not one of its defined variants. +/// +/// # Safety +/// +/// Similar to [`Pod`] except we disregard the rule about it must not contain +/// uninit bytes. Still, this is a quite strong guarantee about a type, so *be +/// careful* when implementing it manually. +/// +/// * The type must be inhabited (eg: no +/// [Infallible](core::convert::Infallible)). +/// * The type must be valid for any bit pattern of its backing memory. +/// * Structs need to have all fields also be `AnyBitPattern`. +/// * 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 AnyBitPattern: + Zeroable + Sized + Copy + 'static +{ +} + +unsafe impl AnyBitPattern for T {} + +#[cfg(feature = "zeroable_maybe_uninit")] +#[cfg_attr(feature = "nightly_docs", doc(cfg(feature = "zeroable_maybe_uninit")))] +unsafe impl AnyBitPattern for core::mem::MaybeUninit where T: AnyBitPattern +{} -- cgit v1.2.3