From: Gary Guo <[email protected]> Add a `KnownSize` trait which is used obtain a size from a raw pointer's metadata. This makes it possible to obtain size information on a raw slice pointer. This is similar to Rust `core::mem::size_of_val_raw` which is not yet stable.
Signed-off-by: Gary Guo <[email protected]> Reviewed-by: Benno Lossin <[email protected]> Acked-by: Miguel Ojeda <[email protected]> --- rust/kernel/lib.rs | 1 + rust/kernel/ptr.rs | 27 ++++++++++++++++++++++++++- 2 files changed, 27 insertions(+), 1 deletion(-) diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 3da92f18f4eed16335c3c251e6bff68dcf7e781e..510cc7fe496113f85c34f420b1c4be95596297ad 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -20,6 +20,7 @@ #![feature(generic_nonzero)] #![feature(inline_const)] #![feature(pointer_is_aligned)] +#![feature(slice_ptr_len)] // // Stable since Rust 1.80.0. #![feature(slice_flatten)] diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs index 5b6a382637fef11e9c0ae9122906422a970d7fcd..cf980a103acf19ee3bd17bb1dfdbcadfe30467ae 100644 --- a/rust/kernel/ptr.rs +++ b/rust/kernel/ptr.rs @@ -2,7 +2,10 @@ //! Types and functions to work with pointers and addresses. -use core::mem::align_of; +use core::mem::{ + align_of, + size_of, // +}; use core::num::NonZero; /// Type representing an alignment, which is always a power of two. @@ -225,3 +228,25 @@ fn align_up(self, alignment: Alignment) -> Option<Self> { } impl_alignable_uint!(u8, u16, u32, u64, usize); + +/// Trait to represent compile-time known size information. +/// +/// This is a generalization of what [`size_of`] which works for dynamically sized types. +pub trait KnownSize { + /// Get the size of an object of this type in bytes, with the metadata of the given pointer. + fn size(p: *const Self) -> usize; +} + +impl<T> KnownSize for T { + #[inline(always)] + fn size(_: *const Self) -> usize { + size_of::<T>() + } +} + +impl<T> KnownSize for [T] { + #[inline(always)] + fn size(p: *const Self) -> usize { + p.len() * size_of::<T>() + } +} -- 2.53.0
