Messages in this thread Patch in this message | | | From | Miguel Ojeda <> | Subject | [PATCH v1 28/28] rust: types: add `Opaque` type | Date | Thu, 10 Nov 2022 17:41:40 +0100 |
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From: Wedson Almeida Filho <wedsonaf@gmail.com>
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: Wedson Almeida Filho <wedsonaf@gmail.com> [Reworded, adapted for upstream and applied latest changes] Signed-off-by: Miguel Ojeda <ojeda@kernel.org> --- 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<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`. -- 2.38.1
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