Struct std::num::NonZeroUsize

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

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>());

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>>());

Implementations

impl NonZeroUsize

pub const unsafe fn new_unchecked(n: usize) -> NonZeroUsize

Creates a non-zero without checking whether the value is non-zero. This results in undefined behaviour if the value is zero.

Safety

The value must not be zero.

pub const fn new(n: usize) -> Option<NonZeroUsize>

Creates a non-zero if the given value is not zero.

pub unsafe fn from_mut_unchecked(n: &mut usize) -> &mut NonZeroUsize

🔬This is a nightly-only experimental API. (nonzero_from_mut #106290)

Converts a primitive mutable reference to a non-zero mutable reference without checking whether the referenced value is non-zero. This results in undefined behavior if *n is zero.

Safety

The referenced value must not be currently zero.

pub fn from_mut(n: &mut usize) -> Option<&mut NonZeroUsize>

🔬This is a nightly-only experimental API. (nonzero_from_mut #106290)

Converts a primitive mutable reference to a non-zero mutable reference if the referenced integer is not zero.

pub const fn get(self) -> usize

Returns the value as a primitive type.

pub const BITS: u32 = 64u32

The size of this non-zero integer type in bits.

This value is equal to usize::BITS.

Examples

assert_eq!(NonZeroUsize::BITS, usize::BITS);

pub const fn leading_zeros(self) -> u32

Returns the number of leading zeros in the binary representation of self.

On many architectures, this function can perform better than leading_zeros() on the underlying integer type, as special handling of zero can be avoided.

Examples

Basic usage:

let n = std::num::NonZeroUsize::new(usize::MAX).unwrap();

assert_eq!(n.leading_zeros(), 0);

pub const fn trailing_zeros(self) -> u32

Returns the number of trailing zeros in the binary representation of self.

On many architectures, this function can perform better than trailing_zeros() on the underlying integer type, as special handling of zero can be avoided.

Examples

Basic usage:

let n = std::num::NonZeroUsize::new(0b0101000).unwrap();

assert_eq!(n.trailing_zeros(), 3);

pub fn count_ones(self) -> NonZeroU32

🔬This is a nightly-only experimental API. (non_zero_count_ones #120287)

Returns the number of ones in the binary representation of self.

Examples

Basic usage:

#![feature(non_zero_count_ones)]

let one = num::NonZeroU32::new(1)?;
let three = num::NonZeroU32::new(3)?;
let a = NonZeroUsize::new(0b100_0000)?;
let b = NonZeroUsize::new(0b100_0011)?;

assert_eq!(a.count_ones(), one);
assert_eq!(b.count_ones(), three);

pub const MIN: NonZeroUsize = _

The smallest value that can be represented by this non-zero integer type, 1.

Examples

assert_eq!(NonZeroUsize::MIN.get(), 1usize);

pub const MAX: NonZeroUsize = _

The largest value that can be represented by this non-zero integer type, equal to usize::MAX.

Examples

assert_eq!(NonZeroUsize::MAX.get(), usize::MAX);

pub const fn checked_add(self, other: usize) -> Option<NonZeroUsize>

Adds an unsigned integer to a non-zero value. Checks for overflow and returns None on overflow. As a consequence, the result cannot wrap to zero.

Examples

let one = NonZeroUsize::new(1)?;
let two = NonZeroUsize::new(2)?;
let max = NonZeroUsize::new(usize::MAX)?;

assert_eq!(Some(two), one.checked_add(1));
assert_eq!(None, max.checked_add(1));

pub const fn saturating_add(self, other: usize) -> NonZeroUsize

Adds an unsigned integer to a non-zero value. Return NonZeroUsize::MAX on overflow.

Examples

let one = NonZeroUsize::new(1)?;
let two = NonZeroUsize::new(2)?;
let max = NonZeroUsize::new(usize::MAX)?;

assert_eq!(two, one.saturating_add(1));
assert_eq!(max, max.saturating_add(1));

pub const unsafe fn unchecked_add(self, other: usize) -> NonZeroUsize

🔬This is a nightly-only experimental API. (nonzero_ops #84186)

Adds an unsigned integer to a non-zero value, assuming overflow cannot occur. Overflow is unchecked, and it is undefined behaviour to overflow even if the result would wrap to a non-zero value. The behaviour is undefined as soon as self + rhs > usize::MAX.

Examples

#![feature(nonzero_ops)]

let one = NonZeroUsize::new(1)?;
let two = NonZeroUsize::new(2)?;

assert_eq!(two, unsafe { one.unchecked_add(1) });

pub const fn checked_next_power_of_two(self) -> Option<NonZeroUsize>

Returns the smallest power of two greater than or equal to n. Checks for overflow and returns None if the next power of two is greater than the type’s maximum value. As a consequence, the result cannot wrap to zero.

Examples

let two = NonZeroUsize::new(2)?;
let three = NonZeroUsize::new(3)?;
let four = NonZeroUsize::new(4)?;
let max = NonZeroUsize::new(usize::MAX)?;

assert_eq!(Some(two), two.checked_next_power_of_two() );
assert_eq!(Some(four), three.checked_next_power_of_two() );
assert_eq!(None, max.checked_next_power_of_two() );

pub const fn ilog2(self) -> u32

Returns the base 2 logarithm of the number, rounded down.

This is the same operation as usize::ilog2, except that it has no failure cases to worry about since this value can never be zero.

Examples

assert_eq!(NonZeroUsize::new(7).unwrap().ilog2(), 2);
assert_eq!(NonZeroUsize::new(8).unwrap().ilog2(), 3);
assert_eq!(NonZeroUsize::new(9).unwrap().ilog2(), 3);

pub const fn ilog10(self) -> u32

Returns the base 10 logarithm of the number, rounded down.

This is the same operation as usize::ilog10, except that it has no failure cases to worry about since this value can never be zero.

Examples

assert_eq!(NonZeroUsize::new(99).unwrap().ilog10(), 1);
assert_eq!(NonZeroUsize::new(100).unwrap().ilog10(), 2);
assert_eq!(NonZeroUsize::new(101).unwrap().ilog10(), 2);

pub fn midpoint(self, rhs: NonZeroUsize) -> NonZeroUsize

🔬This is a nightly-only experimental API. (num_midpoint #110840)

Calculates the middle point of self and rhs.

midpoint(a, b) is (a + b) >> 1 as if it were performed in a sufficiently-large signed integral type. This implies that the result is always rounded towards negative infinity and that no overflow will ever occur.

Examples

#![feature(num_midpoint)]

let one = NonZeroUsize::new(1)?;
let two = NonZeroUsize::new(2)?;
let four = NonZeroUsize::new(4)?;

assert_eq!(one.midpoint(four), two);
assert_eq!(four.midpoint(one), two);

pub const fn is_power_of_two(self) -> bool

Returns true if and only if self == (1 << k) for some k.

On many architectures, this function can perform better than is_power_of_two() on the underlying integer type, as special handling of zero can be avoided.

Examples

Basic usage:

let eight = std::num::NonZeroUsize::new(8).unwrap();
assert!(eight.is_power_of_two());
let ten = std::num::NonZeroUsize::new(10).unwrap();
assert!(!ten.is_power_of_two());

pub const fn checked_mul(self, other: NonZeroUsize) -> Option<NonZeroUsize>

Multiplies two non-zero integers together. Checks for overflow and returns None on overflow. As a consequence, the result cannot wrap to zero.

Examples

let two = NonZeroUsize::new(2)?;
let four = NonZeroUsize::new(4)?;
let max = NonZeroUsize::new(usize::MAX)?;

assert_eq!(Some(four), two.checked_mul(two));
assert_eq!(None, max.checked_mul(two));

pub const fn saturating_mul(self, other: NonZeroUsize) -> NonZeroUsize

Multiplies two non-zero integers together. Return NonZeroUsize::MAX on overflow.

Examples

let two = NonZeroUsize::new(2)?;
let four = NonZeroUsize::new(4)?;
let max = NonZeroUsize::new(usize::MAX)?;

assert_eq!(four, two.saturating_mul(two));
assert_eq!(max, four.saturating_mul(max));

pub const unsafe fn unchecked_mul(self, other: NonZeroUsize) -> NonZeroUsize

🔬This is a nightly-only experimental API. (nonzero_ops #84186)

Multiplies two non-zero integers together, assuming overflow cannot occur. Overflow is unchecked, and it is undefined behaviour to overflow even if the result would wrap to a non-zero value. The behaviour is undefined as soon as self * rhs > usize::MAX.

Examples

#![feature(nonzero_ops)]

let two = NonZeroUsize::new(2)?;
let four = NonZeroUsize::new(4)?;

assert_eq!(four, unsafe { two.unchecked_mul(two) });

pub const fn checked_pow(self, other: u32) -> Option<NonZeroUsize>

Raises non-zero value to an integer power. Checks for overflow and returns None on overflow. As a consequence, the result cannot wrap to zero.

Examples

let three = NonZeroUsize::new(3)?;
let twenty_seven = NonZeroUsize::new(27)?;
let half_max = NonZeroUsize::new(usize::MAX / 2)?;

assert_eq!(Some(twenty_seven), three.checked_pow(3));
assert_eq!(None, half_max.checked_pow(3));

pub const fn saturating_pow(self, other: u32) -> NonZeroUsize

Raise non-zero value to an integer power. Return NonZeroUsize::MAX on overflow.

Examples

let three = NonZeroUsize::new(3)?;
let twenty_seven = NonZeroUsize::new(27)?;
let max = NonZeroUsize::new(usize::MAX)?;

assert_eq!(twenty_seven, three.saturating_pow(3));
assert_eq!(max, max.saturating_pow(3));

Trait Implementations

impl Binary for NonZeroUsize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl BitOr<NonZeroUsize> for usize

type Output = NonZeroUsize

The resulting type after applying the | operator.

fn bitor(self, rhs: NonZeroUsize) -> <usize as BitOr<NonZeroUsize>>::Output

Performs the | operation.

impl BitOr<usize> for NonZeroUsize

type Output = NonZeroUsize

The resulting type after applying the | operator.

fn bitor(self, rhs: usize) -> <NonZeroUsize as BitOr<usize>>::Output

Performs the | operation.

impl BitOr for NonZeroUsize

type Output = NonZeroUsize

The resulting type after applying the | operator.

fn bitor(self, rhs: NonZeroUsize) -> <NonZeroUsize as BitOr>::Output

Performs the | operation.

impl BitOrAssign<usize> for NonZeroUsize

fn bitor_assign(&mut self, rhs: usize)

Performs the |= operation.

impl BitOrAssign for NonZeroUsize

fn bitor_assign(&mut self, rhs: NonZeroUsize)

Performs the |= operation.

impl Clone for NonZeroUsize

fn clone(&self) -> NonZeroUsize

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for NonZeroUsize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Display for NonZeroUsize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Div<NonZeroUsize> for usize

fn div(self, other: NonZeroUsize) -> usize

This operation rounds towards zero, truncating any fractional part of the exact result, and cannot panic.

type Output = usize

The resulting type after applying the / operator.

impl From<Alignment> for NonZeroUsize

fn from(align: Alignment) -> NonZeroUsize

Converts to this type from the input type.

impl From<NonZeroU16> for NonZeroUsize

fn from(small: NonZeroU16) -> NonZeroUsize

Converts NonZeroU16 to NonZeroUsize losslessly.

impl From<NonZeroU8> for NonZeroUsize

fn from(small: NonZeroU8) -> NonZeroUsize

Converts NonZeroU8 to NonZeroUsize losslessly.

impl From<NonZeroUsize> for usize

fn from(nonzero: NonZeroUsize) -> usize

Converts a NonZeroUsize into an usize

impl FromStr for NonZeroUsize

type Err = ParseIntError

The associated error which can be returned from parsing.

fn from_str(src: &str) -> Result<NonZeroUsize, <NonZeroUsize as FromStr>::Err>

Parses a string s to return a value of this type.

impl Hash for NonZeroUsize

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl LowerHex for NonZeroUsize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Octal for NonZeroUsize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Ord for NonZeroUsize

fn cmp(&self, other: &NonZeroUsize) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: NonZeroUsize) -> NonZeroUsize

Compares and returns the maximum of two values.

fn min(self, other: NonZeroUsize) -> NonZeroUsize

Compares and returns the minimum of two values.

fn clamp(self, min: NonZeroUsize, max: NonZeroUsize) -> NonZeroUsize

Restrict a value to a certain interval.

impl PartialEq for NonZeroUsize

fn eq(&self, other: &NonZeroUsize) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &NonZeroUsize) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for NonZeroUsize

fn partial_cmp(&self, other: &NonZeroUsize) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &NonZeroUsize) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &NonZeroUsize) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &NonZeroUsize) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &NonZeroUsize) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Rem<NonZeroUsize> for usize

fn rem(self, other: NonZeroUsize) -> usize

This operation satisfies n % d == n - (n / d) * d, and cannot panic.

type Output = usize

The resulting type after applying the % operator.

impl TryFrom<NonZeroI128> for NonZeroUsize

fn try_from( value: NonZeroI128 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroI128>>::Error>

Attempts to convert NonZeroI128 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroI16> for NonZeroUsize

fn try_from( value: NonZeroI16 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroI16>>::Error>

Attempts to convert NonZeroI16 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroI32> for NonZeroUsize

fn try_from( value: NonZeroI32 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroI32>>::Error>

Attempts to convert NonZeroI32 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroI64> for NonZeroUsize

fn try_from( value: NonZeroI64 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroI64>>::Error>

Attempts to convert NonZeroI64 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroI8> for NonZeroUsize

fn try_from( value: NonZeroI8 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroI8>>::Error>

Attempts to convert NonZeroI8 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroIsize> for NonZeroUsize

fn try_from( value: NonZeroIsize ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroIsize>>::Error>

Attempts to convert NonZeroIsize to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroU128> for NonZeroUsize

fn try_from( value: NonZeroU128 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroU128>>::Error>

Attempts to convert NonZeroU128 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroU32> for NonZeroUsize

fn try_from( value: NonZeroU32 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroU32>>::Error>

Attempts to convert NonZeroU32 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroU64> for NonZeroUsize

fn try_from( value: NonZeroU64 ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<NonZeroU64>>::Error>

Attempts to convert NonZeroU64 to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for Alignment

type Error = TryFromIntError

The type returned in the event of a conversion error.

fn try_from( align: NonZeroUsize ) -> Result<Alignment, <Alignment as TryFrom<NonZeroUsize>>::Error>

Performs the conversion.

impl TryFrom<NonZeroUsize> for NonZeroI128

fn try_from( value: NonZeroUsize ) -> Result<NonZeroI128, <NonZeroI128 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroI128.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroI16

fn try_from( value: NonZeroUsize ) -> Result<NonZeroI16, <NonZeroI16 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroI16.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroI32

fn try_from( value: NonZeroUsize ) -> Result<NonZeroI32, <NonZeroI32 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroI32.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroI64

fn try_from( value: NonZeroUsize ) -> Result<NonZeroI64, <NonZeroI64 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroI64.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroI8

fn try_from( value: NonZeroUsize ) -> Result<NonZeroI8, <NonZeroI8 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroI8.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroIsize

fn try_from( value: NonZeroUsize ) -> Result<NonZeroIsize, <NonZeroIsize as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroIsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroU128

fn try_from( value: NonZeroUsize ) -> Result<NonZeroU128, <NonZeroU128 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroU128.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroU16

fn try_from( value: NonZeroUsize ) -> Result<NonZeroU16, <NonZeroU16 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroU16.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroU32

fn try_from( value: NonZeroUsize ) -> Result<NonZeroU32, <NonZeroU32 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroU32.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroU64

fn try_from( value: NonZeroUsize ) -> Result<NonZeroU64, <NonZeroU64 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroU64.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<NonZeroUsize> for NonZeroU8

fn try_from( value: NonZeroUsize ) -> Result<NonZeroU8, <NonZeroU8 as TryFrom<NonZeroUsize>>::Error>

Attempts to convert NonZeroUsize to NonZeroU8.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<usize> for NonZeroUsize

fn try_from( value: usize ) -> Result<NonZeroUsize, <NonZeroUsize as TryFrom<usize>>::Error>

Attempts to convert usize to NonZeroUsize.

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl UpperHex for NonZeroUsize

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Copy for NonZeroUsize

impl Eq for NonZeroUsize

impl StructuralEq for NonZeroUsize

impl StructuralPartialEq for NonZeroUsize