From b9ecf9b9ac5969d7b7ea786ce5c76e24246df2c5 Mon Sep 17 00:00:00 2001 From: Wedson Almeida Filho Date: Thu, 10 Nov 2022 17:41:40 +0100 Subject: rust: types: add `Opaque` type Add the `Opaque` type, which is meant to be used with FFI objects that are never interpreted by Rust code, e.g.: struct Waiter { completion: Opaque, next: *mut Waiter, } It has the advantage that the objects don't have to be zero-initialised before calling their init functions, making the code performance closer to C. Signed-off-by: Wedson Almeida Filho [Reworded, adapted for upstream and applied latest changes] Signed-off-by: Miguel Ojeda --- rust/kernel/types.rs | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index 3b0c44769708..e84e51ec9716 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -2,6 +2,31 @@ //! Kernel types. +use core::{cell::UnsafeCell, mem::MaybeUninit}; + +/// Stores an opaque value. +/// +/// This is meant to be used with FFI objects that are never interpreted by Rust code. +#[repr(transparent)] +pub struct Opaque(MaybeUninit>); + +impl Opaque { + /// Creates a new opaque value. + pub const fn new(value: T) -> Self { + Self(MaybeUninit::new(UnsafeCell::new(value))) + } + + /// Creates an uninitialised value. + pub const fn uninit() -> Self { + Self(MaybeUninit::uninit()) + } + + /// Returns a raw pointer to the opaque data. + pub fn get(&self) -> *mut T { + UnsafeCell::raw_get(self.0.as_ptr()) + } +} + /// A sum type that always holds either a value of type `L` or `R`. pub enum Either { /// Constructs an instance of [`Either`] containing a value of type `L`. -- cgit v1.2.3-70-g09d2