Type Alias std::num::NonZeroUsize
1.28.0 · source · pub type NonZeroUsize = NonZero<usize>;
Expand description
An integer that is known not to equal zero.
This enables some memory layout optimization.
For example, Option<NonZeroUsize>
is the same size as usize
:
use std::mem::size_of;
assert_eq!(size_of::<Option<core::num::NonZeroUsize>>(), size_of::<usize>());
Run§Layout
NonZeroUsize
is guaranteed to have the same layout and bit validity as usize
with the exception that 0
is not a valid instance.
Option<NonZeroUsize>
is guaranteed to be compatible with usize
,
including in FFI.
Thanks to the null pointer optimization,
NonZeroUsize
and Option<NonZeroUsize>
are guaranteed to have the same size and alignment:
use std::num::NonZeroUsize;
assert_eq!(size_of::<NonZeroUsize>(), size_of::<Option<NonZeroUsize>>());
assert_eq!(align_of::<NonZeroUsize>(), align_of::<Option<NonZeroUsize>>());
RunAliased Type§
struct NonZeroUsize(/* private fields */);