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47f27155f1
The core library's `From` implementations do not cover conversions that are not portable or future-proof. For instance, even though it is safe today, `From<usize>` is not implemented for `u64` because of the possibility of supporting larger-than-64bit architectures in the future. However, the kernel supports a narrower set of architectures, with a considerable amount of code that is architecture-specific. This makes it helpful and desirable to provide more infallible conversions, lest we rely on the `as` keyword and carry the risk of silently losing data. Thus, introduce a new module `num::casts` that provides safe const functions performing more conversions allowed by the build target, as well as `FromSafeCast` and `IntoSafeCast` traits that are just extensions of `From` and `Into` to conversions that are known to be lossless. Some conversions are architecture-specific: for instance, converting a `u64` to a `usize` is only lossless on 64-bit platforms. These conversions are made available via a dedicated `arch` sub-module. Suggested-by: Danilo Krummrich <dakr@kernel.org> Link: https://lore.kernel.org/rust-for-linux/DDK4KADWJHMG.1FUPL3SDR26XF@kernel.org/ Signed-off-by: Alexandre Courbot <acourbot@nvidia.com> Reviewed-by: Danilo Krummrich <dakr@kernel.org> Link: https://patch.msgid.link/20260806-as_casts-v2-1-cb76a4d3a6ef@nvidia.com [ Added a few more intra-doc links. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
82 lines
1.6 KiB
Rust
82 lines
1.6 KiB
Rust
// SPDX-License-Identifier: GPL-2.0
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//! Additional numerical features for the kernel.
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use core::ops;
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pub mod bounded;
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pub mod casts;
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pub use bounded::*;
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/// Designates unsigned primitive types.
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pub enum Unsigned {}
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/// Designates signed primitive types.
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pub enum Signed {}
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/// Describes core properties of integer types.
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pub trait Integer:
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Sized
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+ Copy
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+ Clone
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+ PartialEq
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+ Eq
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+ PartialOrd
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+ Ord
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+ ops::Add<Output = Self>
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+ ops::AddAssign
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+ ops::Sub<Output = Self>
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+ ops::SubAssign
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+ ops::Mul<Output = Self>
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+ ops::MulAssign
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+ ops::Div<Output = Self>
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+ ops::DivAssign
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+ ops::Rem<Output = Self>
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+ ops::RemAssign
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+ ops::BitAnd<Output = Self>
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+ ops::BitAndAssign
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+ ops::BitOr<Output = Self>
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+ ops::BitOrAssign
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+ ops::BitXor<Output = Self>
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+ ops::BitXorAssign
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+ ops::Shl<u32, Output = Self>
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+ ops::ShlAssign<u32>
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+ ops::Shr<u32, Output = Self>
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+ ops::ShrAssign<u32>
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+ ops::Not
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{
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/// Whether this type is [`Signed`] or [`Unsigned`].
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type Signedness;
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/// Number of bits used for value representation.
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const BITS: u32;
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}
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macro_rules! impl_integer {
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($($type:ty: $signedness:ty), *) => {
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$(
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impl Integer for $type {
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type Signedness = $signedness;
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const BITS: u32 = <$type>::BITS;
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}
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)*
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};
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}
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impl_integer!(
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u8: Unsigned,
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u16: Unsigned,
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u32: Unsigned,
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u64: Unsigned,
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u128: Unsigned,
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usize: Unsigned,
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i8: Signed,
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i16: Signed,
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i32: Signed,
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i64: Signed,
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i128: Signed,
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isize: Signed
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);
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