Commit 1db476d2 authored by Alexandre Courbot's avatar Alexandre Courbot
Browse files

rust: transmute: add `as_bytes` method for `AsBytes` trait 



Every type that implements `AsBytes` should be able to provide its byte
representation. Introduce the `as_bytes` method that returns the
implementer as a stream of bytes, and provide a default implementation
that should be suitable for any type that satisfies `AsBytes`'s safety
requirements.

[acourbot@nvidia.com: use fully qualified `core::mem::size_of_val` to
build with Rust 1.78.]

Reviewed-by: default avatarDanilo Krummrich <dakr@kernel.org>
Reviewed-by: default avatarBenno Lossin <lossin@kernel.org>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Acked-by: default avatarMiguel Ojeda <ojeda@kernel.org>
Link: https://lore.kernel.org/r/20250801-as_bytes-v5-1-975f87d5dc85@nvidia.com


Signed-off-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
parent 99e7f8e8

rust/kernel/transmute.rs

+11 −1
Original line number Diff line number Diff line
@@ -47,7 +47,17 @@ macro_rules! impl_frombytes { 
///

/// Values of this type may not contain any uninitialized bytes. This type must not have interior

/// mutability.

pub unsafe trait AsBytes {}

pub unsafe trait AsBytes {

    /// Returns `self` as a slice of bytes.

    fn as_bytes(&self) -> &[u8] {

        // CAST: `Self` implements `AsBytes` thus all bytes of `self` are initialized.

        let data = core::ptr::from_ref(self).cast::<u8>();

        let len = core::mem::size_of_val(self);



        // SAFETY: `data` is non-null and valid for reads of `len * sizeof::<u8>()` bytes.

        unsafe { core::slice::from_raw_parts(data, len) }

    }

}



macro_rules! impl_asbytes {

    ($($({$($generics:tt)*})? $t:ty, )*) => {