1 stable release
1.0.0 | Jan 1, 2021 |
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#1453 in Rust patterns
6KB
75 lines
repr-trait
Traits to represent Rust repr
s
If it is important for a generic parameter to have a particular repr
, you can use
the traits in this crate to ensure that it has the needed repr
.
For example, if you have an unsafe
function that requires a specific repr
,
you can use these traits to create a safe wrapper around it.
use repr_trait::Packed;
// Safety: Only safe to call when T has #[repr(packed)]
unsafe fn safe_when_packed<T>(_param: T) {
unimplemented!()
}
fn safe_wrapper<T: Packed>(param: T) {
// Safety: Safe because T is guaranteed to be #[repr(packed)]
unsafe {
safe_when_packed(param)
}
}
Implementing the traits from this crate is easy using derive macros. There is a derive macro for each included trait.
#[derive(Packed, Default)]
#[repr(packed)]
struct PackedData(u32, u8);
safe_wrapper(PackedData(123, 45));
If the appropriate repr
is not specified, the derive macro will refuse to compile.
#[derive(Packed)]
struct NotPacked(u32, u8);
Structure
This repo contains two crates: repr-trait holds the traits and reexports the derive macros. It is the only trait that should be used in general. repr-trait-derive holds the derive macro implementations. It is an implementation detail, and should generally not be relied on directly.
Dependencies
~1.5MB
~36K SLoC