6 releases
0.3.2 | Sep 23, 2024 |
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0.3.1 | May 18, 2024 |
0.3.0 | Mar 21, 2024 |
0.2.1 | Dec 24, 2023 |
0.1.0 | Jan 20, 2023 |
#312 in Rust patterns
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97KB
2K
SLoC
const-type-layout
is a type layout comparison aid, providing a #[derive]
able TypeLayout
trait
that reports:
- The type's name, size, and minimum alignment
- The type's structure, i.e. struct vs. union vs. enum
- Each field's name and offset
- Each variant's name and discriminant
Through the auto-implemented TypeGraphLayout
trait, the deep type layout is also reported as a graph.
This crate heavily builds on the original runtime type-layout crate by Lucien Greathouse.
Examples
The layout of types is only defined if they're #[repr(C)]
. This crate works on
non-#[repr(C)]
types, but their layout is unpredictable.
use const_type_layout::TypeLayout;
#[derive(TypeLayout)]
#[repr(C)]
struct Foo {
a: u8,
b: u32,
}
assert_eq!(
format!("{:#?}", Foo::TYPE_LAYOUT),
r#"TypeLayoutInfo {
name: "mycrate::mymodule::Foo",
size: 8,
alignment: 4,
structure: Struct {
repr: "C",
fields: [
Field {
name: "a",
offset: Inhabited(
0,
),
ty: "u8",
},
Field {
name: "b",
offset: Inhabited(
4,
),
ty: "u32",
},
],
},
}"#
);
Over-aligned types have trailing padding, which can be a source of bugs in some FFI scenarios:
use const_type_layout::TypeLayout;
#[derive(TypeLayout)]
#[repr(C, align(128))]
struct OverAligned {
value: u8,
}
assert_eq!(
format!("{:#?}", OverAligned::TYPE_LAYOUT),
r#"TypeLayoutInfo {
name: "mycrate::mymodule::OverAligned",
size: 128,
alignment: 128,
structure: Struct {
repr: "C,align(128)",
fields: [
Field {
name: "value",
offset: Inhabited(
0,
),
ty: "u8",
},
],
},
}"#
)
License
Licensed under either of
- Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
Dependencies
~0–375KB