Struct std::num::NonZeroUsize

1.28.0 · source · 
pub struct NonZeroUsize(_);
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

Implementations§

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.

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

Returns the value as a primitive type.

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);
Run

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);
Run

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));
Run

Adds an unsigned integer to a non-zero value. Return usize::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));
Run
🔬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) });
Run

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() );
Run

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);
Run

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);
Run

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));
Run

Multiplies two non-zero integers together. Return usize::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));
Run
🔬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) });
Run

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));
Run

Raise non-zero value to an integer power. Return usize::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));
Run

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());
Run
🔬This is a nightly-only experimental API. (nonzero_min_max #89065)

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

Examples
#![feature(nonzero_min_max)]

assert_eq!(NonZeroUsize::MIN.get(), 1usize);
Run
🔬This is a nightly-only experimental API. (nonzero_min_max #89065)

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

Examples
#![feature(nonzero_min_max)]

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

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

This value is equal to usize::BITS.

Examples

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

Trait Implementations§

Formats the value using the given formatter.
The resulting type after applying the | operator.
Performs the | operation. Read more
The resulting type after applying the | operator.
Performs the | operation. Read more
The resulting type after applying the | operator.
Performs the | operation. Read more
Performs the |= operation. Read more
Performs the |= operation. Read more
Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Formats the value using the given formatter. Read more

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

The resulting type after applying the / operator.
Converts to this type from the input type.

Converts NonZeroU16 to NonZeroUsize losslessly.

Converts NonZeroU8 to NonZeroUsize losslessly.

Converts a NonZeroUsize into an usize

The associated error which can be returned from parsing.
Parses a string s to return a value of this type. Read more
Feeds this value into the given Hasher. Read more
Feeds a slice of this type into the given Hasher. Read more
Formats the value using the given formatter.
Formats the value using the given formatter.
This method returns an Ordering between self and other. Read more
Compares and returns the maximum of two values. Read more
Compares and returns the minimum of two values. Read more
Restrict a value to a certain interval. Read more
This method tests for self and other values to be equal, and is used by ==.
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
This method returns an ordering between self and other values if one exists. Read more
This method tests less than (for self and other) and is used by the < operator. Read more
This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
This method tests greater than (for self and other) and is used by the > operator. Read more
This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

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

The resulting type after applying the % operator.

Attempts to convert NonZeroI128 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroI16 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroI32 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroI64 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroI8 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroIsize to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroU128 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroU32 to NonZeroUsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroU64 to NonZeroUsize.

The type returned in the event of a conversion error.
The type returned in the event of a conversion error.
Performs the conversion.

Attempts to convert NonZeroUsize to NonZeroI128.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroI16.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroI32.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroI64.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroI8.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroIsize.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroU128.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroU16.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroU32.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroU64.

The type returned in the event of a conversion error.

Attempts to convert NonZeroUsize to NonZeroU8.

The type returned in the event of a conversion error.

Attempts to convert usize to NonZeroUsize.

The type returned in the event of a conversion error.
Formats the value using the given formatter.

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
Converts the given value to a String. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.