pub unsafe trait NoUninit { }Expand description
A marker trait for types without uninitialized (padding) bytes
This is modelled after the NoUninit trait of the
bytemuck crate.
In order for writing a value of a type T to a WNF state to be sound, T is required to implement NoUninit.
§Implementation
This trait is already implemented by the wnf crate for many primitive types and types from the standard
library. There are several ways to implement it for your own types:
- Implement it directly, requiring
unsafecode - Derive the
NoUninittrait of thebytemuckcrate and derive this trait from it via thederive_from_bytemuck_v1macro:
use wnf::{derive_from_bytemuck_v1, OwnedState};
#[derive(bytemuck::NoUninit, bytemuck::AnyBitPattern, Copy, Clone)]
#[repr(transparent)]
struct MyType(u32);
derive_from_bytemuck_v1!(NoUninit for MyType);
derive_from_bytemuck_v1!(AnyBitPattern for MyType);
let state: OwnedState<MyType> = OwnedState::create_temporary()?;
state.set(&MyType(42))?;
let data = state.get()?;
assert_eq!(data.0, 42);- Derive the
FromBytestrait of thezerocopycrate and derive this trait from it via thederive_from_zerocopymacro:
use wnf::{derive_from_zerocopy, OwnedState};
#[derive(zerocopy::FromBytes, zerocopy::FromZeroes, zerocopy::AsBytes, Copy, Clone)]
#[repr(transparent)]
struct MyType(u32);
derive_from_zerocopy!(NoUninit for MyType);
derive_from_zerocopy!(AnyBitPattern for MyType);
let state: OwnedState<MyType> = OwnedState::create_temporary()?;
state.set(&MyType(42))?;
let data = state.get()?;
assert_eq!(data.0, 42);§Safety
Implementing this trait for a type T is sound if the memory representation of any T contains no uninitialized
(i.e. padding) bytes.