NonZeroU32 in core::num - Rust
Description: A `u32` that is known not to equal zero.

## NonZeroU32

# Type Alias NonZeroU32

1.28.0 · Source

    pub type NonZeroU32 = NonZero<u32>;

Expand description

A `u32` that is known not to equal zero.

This enables some memory layout optimization. For example, `Option<NonZeroU32>` is the same size as `u32`:

    assert_eq!(size_of::<Option<core::num::NonZeroU32>>(), size_of::<u32>());

## §Layout

`NonZeroU32` is guaranteed to have the same layout and bit validity as `u32` with the exception that `0` is not a valid instance. `Option<NonZeroU32>` is guaranteed to be compatible with `u32`, including in FFI.

Thanks to the null pointer optimization, `NonZeroU32` and `Option<NonZeroU32>` are guaranteed to have the same size and alignment:

    use std::num::NonZeroU32;

    assert_eq!(size_of::<NonZeroU32>(), size_of::<Option<NonZeroU32>>());
    assert_eq!(align_of::<NonZeroU32>(), align_of::<Option<NonZeroU32>>());

## §Compile-time creation

Since both `Option::unwrap()` and `Option::expect()` are `const`, it is possible to define a new `NonZeroU32` at compile time via:

    use std::num::NonZeroU32;

    const TEN: NonZeroU32 = NonZeroU32::new(10).expect("ten is non-zero");

## Aliased Type§

    pub struct NonZeroU32(/* private fields */);