Commit b9ecf9b9 authored by Wedson Almeida Filho's avatar Wedson Almeida Filho Committed by Miguel Ojeda
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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<bindings::completion>,
        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: default avatarWedson Almeida Filho <wedsonaf@gmail.com>
[Reworded, adapted for upstream and applied latest changes]
Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent ba20915b

rust/kernel/types.rs

+25 −0
Original line number Diff line number Diff line
@@ -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<T>(MaybeUninit<UnsafeCell<T>>);



impl<T> Opaque<T> {

    /// 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<L, R> {

    /// Constructs an instance of [`Either`] containing a value of type `L`.