b9ecf9b9ac
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>
38 lines
988 B
Rust
38 lines
988 B
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Kernel types.
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use core::{cell::UnsafeCell, mem::MaybeUninit};
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/// Stores an opaque value.
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///
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/// This is meant to be used with FFI objects that are never interpreted by Rust code.
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#[repr(transparent)]
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pub struct Opaque<T>(MaybeUninit<UnsafeCell<T>>);
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impl<T> Opaque<T> {
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/// Creates a new opaque value.
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pub const fn new(value: T) -> Self {
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Self(MaybeUninit::new(UnsafeCell::new(value)))
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}
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/// Creates an uninitialised value.
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pub const fn uninit() -> Self {
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Self(MaybeUninit::uninit())
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}
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/// Returns a raw pointer to the opaque data.
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pub fn get(&self) -> *mut T {
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UnsafeCell::raw_get(self.0.as_ptr())
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}
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}
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/// A sum type that always holds either a value of type `L` or `R`.
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pub enum Either<L, R> {
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/// Constructs an instance of [`Either`] containing a value of type `L`.
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Left(L),
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/// Constructs an instance of [`Either`] containing a value of type `R`.
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Right(R),
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}
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