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## NonZeroU64

# Type Alias NonZeroU64

1.28.0 · Source

    pub type NonZeroU64 = NonZero<u64>;

Expand description

A `u64` that is known not to equal zero.

This enables some memory layout optimization. For example, `Option<NonZeroU64>` is the same size as `u64`:

    assert_eq!(size_of::<Option<core::num::NonZeroU64>>(), size_of::<u64>());

## §Layout

`NonZeroU64` is guaranteed to have the same layout and bit validity as `u64` with the exception that `0` is not a valid instance. `Option<NonZeroU64>` is guaranteed to be compatible with `u64`, including in FFI.

Thanks to the null pointer optimization, `NonZeroU64` and `Option<NonZeroU64>` are guaranteed to have the same size and alignment:

    use std::num::NonZeroU64;

    assert_eq!(size_of::<NonZeroU64>(), size_of::<Option<NonZeroU64>>());
    assert_eq!(align_of::<NonZeroU64>(), align_of::<Option<NonZeroU64>>());

## §Compile-time creation

Since both `Option::unwrap()` and `Option::expect()` are `const`, it is possible to define a new `NonZeroU64` at compile time via:

    use std::num::NonZeroU64;

    const TEN: NonZeroU64 = NonZeroU64::new(10).expect("ten is non-zero");

## Aliased Type§

    pub struct NonZeroU64(/* private fields */);