# Type Alias core::num::NonZeroU8

1.28.0 · source ·

    pub type NonZeroU8 = NonZero<u8>;

Expand description

An integer that is known not to equal zero.

This enables some memory layout optimization. For example, `Option<NonZeroU8>` is the same size as `u8`:

    use std::mem::size_of;
    assert_eq!(size_of::<Option<core::num::NonZeroU8>>(), size_of::<u8>());

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## §Layout

`NonZeroU8` is guaranteed to have the same layout and bit validity as `u8` with the exception that `0` is not a valid instance. `Option<NonZeroU8>` is guaranteed to be compatible with `u8`, including in FFI.

Thanks to the null pointer optimization, `NonZeroU8` and `Option<NonZeroU8>` are guaranteed to have the same size and alignment:

    use std::num::NonZeroU8;

    assert_eq!(size_of::<NonZeroU8>(), size_of::<Option<NonZeroU8>>());
    assert_eq!(align_of::<NonZeroU8>(), align_of::<Option<NonZeroU8>>());

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## Aliased Type§

    struct NonZeroU8(/* private fields */);

## Implementations§

source§

### impl NonZeroU8

1.67.0 · source

#### pub const BITS: u32 = 8u32

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

This value is equal to `u8::BITS`.

##### §Examples

    assert_eq!(NonZeroU8::BITS, u8::BITS);

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1.53.0 (const: 1.53.0) · source

#### 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::NonZeroU8::new(u8::MAX).unwrap();

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

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1.53.0 (const: 1.53.0) · source

#### 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::NonZeroU8::new(0b0101000).unwrap();

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

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const: unstable · source

#### pub fn count_ones(self) -> NonZero<u32>

🔬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(generic_nonzero, non_zero_count_ones)]
    let a = NonZero::<u8>::new(0b100_0000)?;
    let b = NonZero::<u8>::new(0b100_0011)?;

    assert_eq!(a.count_ones(), NonZero::new(1)?);
    assert_eq!(b.count_ones(), NonZero::new(3)?);

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1.70.0 · source

#### pub const MIN: Self = _

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

##### §Examples

    assert_eq!(NonZeroU8::MIN.get(), 1u8);

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1.70.0 · source

#### pub const MAX: Self = _

The largest value that can be represented by this non-zero integer type, equal to `u8::MAX`.

##### §Examples

    assert_eq!(NonZeroU8::MAX.get(), u8::MAX);

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1.64.0 (const: 1.64.0) · source

#### pub const fn checked_add(self, other: u8) -> Option<Self>

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 = NonZeroU8::new(1)?;
    let two = NonZeroU8::new(2)?;
    let max = NonZeroU8::new(u8::MAX)?;

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

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1.64.0 (const: 1.64.0) · source

#### pub const fn saturating_add(self, other: u8) -> Self

Adds an unsigned integer to a non-zero value. Return `NonZeroU8::MAX` on overflow.

##### §Examples

    let one = NonZeroU8::new(1)?;
    let two = NonZeroU8::new(2)?;
    let max = NonZeroU8::new(u8::MAX)?;

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

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source

#### pub const unsafe fn unchecked_add(self, other: u8) -> Self

🔬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 > u8::MAX`.

##### §Examples

    #![feature(nonzero_ops)]

    let one = NonZeroU8::new(1)?;
    let two = NonZeroU8::new(2)?;

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

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1.64.0 (const: 1.64.0) · source

#### pub const fn checked_next_power_of_two(self) -> Option<Self>

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 = NonZeroU8::new(2)?;
    let three = NonZeroU8::new(3)?;
    let four = NonZeroU8::new(4)?;
    let max = NonZeroU8::new(u8::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() );

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1.67.0 (const: 1.67.0) · source

#### pub const fn ilog2(self) -> u32

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

This is the same operation as `u8::ilog2`, except that it has no failure cases to worry about since this value can never be zero.

##### §Examples

    assert_eq!(NonZeroU8::new(7).unwrap().ilog2(), 2);
    assert_eq!(NonZeroU8::new(8).unwrap().ilog2(), 3);
    assert_eq!(NonZeroU8::new(9).unwrap().ilog2(), 3);

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1.67.0 (const: 1.67.0) · source

#### pub const fn ilog10(self) -> u32

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

This is the same operation as `u8::ilog10`, except that it has no failure cases to worry about since this value can never be zero.

##### §Examples

    assert_eq!(NonZeroU8::new(99).unwrap().ilog10(), 1);
    assert_eq!(NonZeroU8::new(100).unwrap().ilog10(), 2);
    assert_eq!(NonZeroU8::new(101).unwrap().ilog10(), 2);

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const: unstable · source

#### pub fn midpoint(self, rhs: Self) -> Self

🔬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 = NonZeroU8::new(1)?;
    let two = NonZeroU8::new(2)?;
    let four = NonZeroU8::new(4)?;

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

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1.59.0 (const: 1.59.0) · source

#### 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::NonZeroU8::new(8).unwrap();
    assert!(eight.is_power_of_two());
    let ten = std::num::NonZeroU8::new(10).unwrap();
    assert!(!ten.is_power_of_two());

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1.64.0 (const: 1.64.0) · source

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

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 = NonZeroU8::new(2)?;
    let four = NonZeroU8::new(4)?;
    let max = NonZeroU8::new(u8::MAX)?;

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

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1.64.0 (const: 1.64.0) · source

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

Multiplies two non-zero integers together. Return `NonZeroU8::MAX` on overflow.

##### §Examples

    let two = NonZeroU8::new(2)?;
    let four = NonZeroU8::new(4)?;
    let max = NonZeroU8::new(u8::MAX)?;

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

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source

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

🔬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 > u8::MAX`.

##### §Examples

    #![feature(nonzero_ops)]

    let two = NonZeroU8::new(2)?;
    let four = NonZeroU8::new(4)?;

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

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1.64.0 (const: 1.64.0) · source

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

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 = NonZeroU8::new(3)?;
    let twenty_seven = NonZeroU8::new(27)?;
    let half_max = NonZeroU8::new(u8::MAX / 2)?;

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

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1.64.0 (const: 1.64.0) · source

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

Raise non-zero value to an integer power. Return `NonZeroU8::MAX` on overflow.

##### §Examples

    let three = NonZeroU8::new(3)?;
    let twenty_seven = NonZeroU8::new(27)?;
    let max = NonZeroU8::new(u8::MAX)?;

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

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## Trait Implementations§

1.35.0 · source§

### impl FromStr for NonZeroU8

§

#### type Err = ParseIntError

The associated error which can be returned from parsing.
source§

#### fn from_str(src: &str) -> Result<Self, Self::Err>

Parses a string `s` to return a value of this type. Read more