elain

Crates.ioelain
lib.rselain
version
sourcesrc
created_at2021-04-08 18:27:53.824305
updated_at2024-10-17 12:42:42.222453
descriptionSet a type's minimum alignment with const generics.
homepage
repositoryhttps://github.com/jswrenn/elain
max_upload_size
id380988
Cargo.toml error:TOML parse error at line 18, column 1 | 18 | autolib = false | ^^^^^^^ unknown field `autolib`, expected one of `name`, `version`, `edition`, `authors`, `description`, `readme`, `license`, `repository`, `homepage`, `documentation`, `build`, `resolver`, `links`, `default-run`, `default_dash_run`, `rust-version`, `rust_dash_version`, `rust_version`, `license-file`, `license_dash_file`, `license_file`, `licenseFile`, `license_capital_file`, `forced-target`, `forced_dash_target`, `autobins`, `autotests`, `autoexamples`, `autobenches`, `publish`, `metadata`, `keywords`, `categories`, `exclude`, `include`
size0
Jack Wrenn (jswrenn)

documentation

README

Elain

Set the minimum alignments of types using const generics, rather than #[repr(align(N))].

Basic Use

The type Align<N> is a zero-sized-type with alignment equal to N:

use elain::Align;
use core::mem::{align_of, align_of_val};

assert_eq!(align_of::<Align<1>>(), 1);
assert_eq!(align_of::<Align<2>>(), 2);
assert_eq!(align_of::<Align<4>>(), 4);

const FOO_ALIGN: usize = 8;

#[repr(C)]
struct Foo {
    _align: Align<FOO_ALIGN>,
}

let foo: Foo = Foo { _align: Align::NEW };

assert_eq!(align_of_val(&foo), 8);

Valid alignments are powers of two less-than-or-equal to 228. Supplying an invalid alignment to [Align] is a type error:

use elain::Align;

struct Foo(Align<3>); // Compile Error

Generic Use

Because only some integers are valid alignments, supplying the alignment of a type generically requires some extra work:

use elain::Align;

struct Foo<const N: usize> {
    _align: Align<N>,
}

To resolve this error, add a where bound like so, using the [Alignment] trait to check that Align<N> is valid.

use elain::{Align, Alignment};
use core::mem::align_of;

struct Foo<const MIN_ALIGNMENT: usize>
where
    Align<MIN_ALIGNMENT>: Alignment
{
    _align: Align<MIN_ALIGNMENT>,
    bar: u8,
    baz: u16,
}

assert_eq!(align_of::<Foo<1>>(), 2);
assert_eq!(align_of::<Foo<2>>(), 2);
assert_eq!(align_of::<Foo<4>>(), 4);
Commit count: 7

cargo fmt