NonZeroI128 in std::num - Rust (original) (raw)

Type Alias NonZeroI128

1.34.0 · Source

pub type NonZeroI128 = NonZero<i128>;

Expand description

An i128 that is known not to equal zero.

This enables some memory layout optimization. For example, Option<NonZeroI128> is the same size as i128:

use std::mem::size_of;
assert_eq!(size_of::<Option<core::num::NonZeroI128>>(), size_of::<i128>());

§Layout

NonZeroI128 is guaranteed to have the same layout and bit validity as i128with the exception that 0 is not a valid instance.Option<NonZeroI128> is guaranteed to be compatible with i128, including in FFI.

Thanks to the null pointer optimization,NonZeroI128 and Option<NonZeroI128>are guaranteed to have the same size and alignment:

use std::num::NonZeroI128;

assert_eq!(size_of::<NonZeroI128>(), size_of::<Option<NonZeroI128>>());
assert_eq!(align_of::<NonZeroI128>(), align_of::<Option<NonZeroI128>>());

struct NonZeroI128(/* private fields */);