std::num

# Type Alias NonZeroU8

1.28.0 · Source

    pub type NonZeroU8 = NonZero<u8>;

Expand description

A `u8` that is known not to equal zero.

This enables some memory layout optimization. For example, `Option<NonZeroU8>` is the same size as `u8`:

    use std::mem::size_of;
    assert_eq!(size_of::<Option<core::num::NonZeroU8>>(), size_of::<u8>());

## §Layout

`NonZeroU8` is guaranteed to have the same layout and bit validity as `u8` with the exception that `0` is not a valid instance. `Option<NonZeroU8>` is guaranteed to be compatible with `u8`, including in FFI.

Thanks to the null pointer optimization, `NonZeroU8` and `Option<NonZeroU8>` are guaranteed to have the same size and alignment:

    use std::num::NonZeroU8;

    assert_eq!(size_of::<NonZeroU8>(), size_of::<Option<NonZeroU8>>());
    assert_eq!(align_of::<NonZeroU8>(), align_of::<Option<NonZeroU8>>());

## Aliased Type§

    struct NonZeroU8(/* private fields */);