# Type Alias core::num::NonZeroU128

1.28.0 · source ·

    pub type NonZeroU128 = NonZero<u128>;

Expand description

An integer that is known not to equal zero.

This enables some memory layout optimization. For example, `Option<NonZeroU128>` is the same size as `u128`:

    use std::mem::size_of;
    assert_eq!(size_of::<Option<core::num::NonZeroU128>>(), size_of::<u128>());

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## §Layout

`NonZeroU128` is guaranteed to have the same layout and bit validity as `u128` with the exception that `0` is not a valid instance. `Option<NonZeroU128>` is guaranteed to be compatible with `u128`, including in FFI.

Thanks to the null pointer optimization, `NonZeroU128` and `Option<NonZeroU128>` are guaranteed to have the same size and alignment:

    use std::num::NonZeroU128;

    assert_eq!(size_of::<NonZeroU128>(), size_of::<Option<NonZeroU128>>());
    assert_eq!(align_of::<NonZeroU128>(), align_of::<Option<NonZeroU128>>());

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## Aliased Type§

    struct NonZeroU128(/* private fields */);