The smallest value that can be represented by this integer type.

Examples

Basic usage:

assert_eq!(usize::MIN, 0);

The largest value that can be represented by this integer type.

Examples

Basic usage:

assert_eq!(usize::MAX, 18446744073709551615);

The size of this integer type in bits.

Examples

assert_eq!(usize::BITS, 64);

Converts a string slice in a given base to an integer.

The string is expected to be an optional + sign followed by digits. Leading and trailing whitespace represent an error. Digits are a subset of these characters, depending on radix:

• 0-9
• a-z
• A-Z

Panics

This function panics if radix is not in the range from 2 to 36.

Examples

Basic usage:

assert_eq!(usize::from_str_radix("A", 16), Ok(10));

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

Examples

Basic usage:

let n = 0b01001100usize;

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

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

Examples

Basic usage:

assert_eq!(usize::MAX.count_zeros(), 0);

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

Examples

Basic usage:

let n = usize::MAX >> 2;

assert_eq!(n.leading_zeros(), 2);

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

Examples

Basic usage:

let n = 0b0101000usize;

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

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

Examples

Basic usage:

let n = !(usize::MAX >> 2);

assert_eq!(n.leading_ones(), 2);

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

Examples

Basic usage:

let n = 0b1010111usize;

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

Shifts the bits to the left by a specified amount, n, wrapping the truncated bits to the end of the resulting integer.

Please note this isn’t the same operation as the << shifting operator!

Examples

Basic usage:

let n = 0xaa00000000006e1usize;
let m = 0x6e10aa;

assert_eq!(n.rotate_left(12), m);

Shifts the bits to the right by a specified amount, n, wrapping the truncated bits to the beginning of the resulting integer.

Please note this isn’t the same operation as the >> shifting operator!

Examples

Basic usage:

let n = 0x6e10aausize;
let m = 0xaa00000000006e1;

assert_eq!(n.rotate_right(12), m);

Reverses the byte order of the integer.

Examples

Basic usage:

let n = 0x1234567890123456usize;
let m = n.swap_bytes();

assert_eq!(m, 0x5634129078563412);

Reverses the order of bits in the integer. The least significant bit becomes the most significant bit, second least-significant bit becomes second most-significant bit, etc.

Examples

Basic usage:

let n = 0x1234567890123456usize;
let m = n.reverse_bits();

assert_eq!(m, 0x6a2c48091e6a2c48);
assert_eq!(0, 0usize.reverse_bits());

Converts an integer from big endian to the target’s endianness.

On big endian this is a no-op. On little endian the bytes are swapped.

Examples

Basic usage:

let n = 0x1Ausize;

if cfg!(target_endian = "big") {
    assert_eq!(usize::from_be(n), n)
} else {
    assert_eq!(usize::from_be(n), n.swap_bytes())
}

Converts an integer from little endian to the target’s endianness.

On little endian this is a no-op. On big endian the bytes are swapped.

Examples

Basic usage:

let n = 0x1Ausize;

if cfg!(target_endian = "little") {
    assert_eq!(usize::from_le(n), n)
} else {
    assert_eq!(usize::from_le(n), n.swap_bytes())
}

Converts self to big endian from the target’s endianness.

On big endian this is a no-op. On little endian the bytes are swapped.

Examples

Basic usage:

let n = 0x1Ausize;

if cfg!(target_endian = "big") {
    assert_eq!(n.to_be(), n)
} else {
    assert_eq!(n.to_be(), n.swap_bytes())
}

Converts self to little endian from the target’s endianness.

On little endian this is a no-op. On big endian the bytes are swapped.

Examples

Basic usage:

let n = 0x1Ausize;

if cfg!(target_endian = "little") {
    assert_eq!(n.to_le(), n)
} else {
    assert_eq!(n.to_le(), n.swap_bytes())
}

Checked integer addition. Computes self + rhs, returning None if overflow occurred.

Examples

Basic usage:

assert_eq!((usize::MAX - 2).checked_add(1), Some(usize::MAX - 1));
assert_eq!((usize::MAX - 2).checked_add(3), None);

Unchecked integer addition. Computes self + rhs, assuming overflow cannot occur. This results in undefined behavior when self + rhs > usize::MAX or self + rhs < usize::MIN.

Checked integer subtraction. Computes self - rhs, returning None if overflow occurred.

Examples

Basic usage:

assert_eq!(1usize.checked_sub(1), Some(0));
assert_eq!(0usize.checked_sub(1), None);

Unchecked integer subtraction. Computes self - rhs, assuming overflow cannot occur. This results in undefined behavior when self - rhs > usize::MAX or self - rhs < usize::MIN.

Checked integer multiplication. Computes self * rhs, returning None if overflow occurred.

Examples

Basic usage:

assert_eq!(5usize.checked_mul(1), Some(5));
assert_eq!(usize::MAX.checked_mul(2), None);

Unchecked integer multiplication. Computes self * rhs, assuming overflow cannot occur. This results in undefined behavior when self * rhs > usize::MAX or self * rhs < usize::MIN.

Checked integer division. Computes self / rhs, returning None if rhs == 0.

Examples

Basic usage:

assert_eq!(128usize.checked_div(2), Some(64));
assert_eq!(1usize.checked_div(0), None);

Checked Euclidean division. Computes self.div_euclid(rhs), returning None if rhs == 0.

Examples

Basic usage:

assert_eq!(128usize.checked_div_euclid(2), Some(64));
assert_eq!(1usize.checked_div_euclid(0), None);

Checked integer remainder. Computes self % rhs, returning None if rhs == 0.

Examples

Basic usage:

assert_eq!(5usize.checked_rem(2), Some(1));
assert_eq!(5usize.checked_rem(0), None);

Checked Euclidean modulo. Computes self.rem_euclid(rhs), returning None if rhs == 0.

Examples

Basic usage:

assert_eq!(5usize.checked_rem_euclid(2), Some(1));
assert_eq!(5usize.checked_rem_euclid(0), None);

Checked negation. Computes -self, returning None unless self == 0.

Note that negating any positive integer will overflow.

Examples

Basic usage:

assert_eq!(0usize.checked_neg(), Some(0));
assert_eq!(1usize.checked_neg(), None);

Checked shift left. Computes self << rhs, returning None if rhs is larger than or equal to the number of bits in self.

Examples

Basic usage:

assert_eq!(0x1usize.checked_shl(4), Some(0x10));
assert_eq!(0x10usize.checked_shl(129), None);

Checked shift right. Computes self >> rhs, returning None if rhs is larger than or equal to the number of bits in self.

Examples

Basic usage:

assert_eq!(0x10usize.checked_shr(4), Some(0x1));
assert_eq!(0x10usize.checked_shr(129), None);

Checked exponentiation. Computes self.pow(exp), returning None if overflow occurred.

Examples

Basic usage:

assert_eq!(2usize.checked_pow(5), Some(32));
assert_eq!(usize::MAX.checked_pow(2), None);

Saturating integer addition. Computes self + rhs, saturating at the numeric bounds instead of overflowing.

Examples

Basic usage:

assert_eq!(100usize.saturating_add(1), 101);
assert_eq!(usize::MAX.saturating_add(127), usize::MAX);

Saturating integer subtraction. Computes self - rhs, saturating at the numeric bounds instead of overflowing.

Examples

Basic usage:

assert_eq!(100usize.saturating_sub(27), 73);
assert_eq!(13usize.saturating_sub(127), 0);

Saturating integer multiplication. Computes self * rhs, saturating at the numeric bounds instead of overflowing.

Examples

Basic usage:

assert_eq!(2usize.saturating_mul(10), 20);
assert_eq!((usize::MAX).saturating_mul(10), usize::MAX);

Saturating integer exponentiation. Computes self.pow(exp), saturating at the numeric bounds instead of overflowing.

Examples

Basic usage:

assert_eq!(4usize.saturating_pow(3), 64);
assert_eq!(usize::MAX.saturating_pow(2), usize::MAX);

Wrapping (modular) addition. Computes self + rhs, wrapping around at the boundary of the type.

Examples

Basic usage:

assert_eq!(200usize.wrapping_add(55), 255);
assert_eq!(200usize.wrapping_add(usize::MAX), 199);

Wrapping (modular) subtraction. Computes self - rhs, wrapping around at the boundary of the type.

Examples

Basic usage:

assert_eq!(100usize.wrapping_sub(100), 0);
assert_eq!(100usize.wrapping_sub(usize::MAX), 101);

Wrapping (modular) multiplication. Computes self * rhs, wrapping around at the boundary of the type.

Examples

Basic usage:

Please note that this example is shared between integer types. Which explains why u8 is used here.

assert_eq!(10u8.wrapping_mul(12), 120);
assert_eq!(25u8.wrapping_mul(12), 44);

Wrapping (modular) division. Computes self / rhs. Wrapped division on unsigned types is just normal division. There’s no way wrapping could ever happen. This function exists, so that all operations are accounted for in the wrapping operations.

Examples

Basic usage:

assert_eq!(100usize.wrapping_div(10), 10);

Wrapping Euclidean division. Computes self.div_euclid(rhs). Wrapped division on unsigned types is just normal division. There’s no way wrapping could ever happen. This function exists, so that all operations are accounted for in the wrapping operations. Since, for the positive integers, all common definitions of division are equal, this is exactly equal to self.wrapping_div(rhs).

Examples

Basic usage:

assert_eq!(100usize.wrapping_div_euclid(10), 10);

Wrapping (modular) remainder. Computes self % rhs. Wrapped remainder calculation on unsigned types is just the regular remainder calculation. There’s no way wrapping could ever happen. This function exists, so that all operations are accounted for in the wrapping operations.

Examples

Basic usage:

assert_eq!(100usize.wrapping_rem(10), 0);

Wrapping Euclidean modulo. Computes self.rem_euclid(rhs). Wrapped modulo calculation on unsigned types is just the regular remainder calculation. There’s no way wrapping could ever happen. This function exists, so that all operations are accounted for in the wrapping operations. Since, for the positive integers, all common definitions of division are equal, this is exactly equal to self.wrapping_rem(rhs).

Examples

Basic usage:

assert_eq!(100usize.wrapping_rem_euclid(10), 0);

Wrapping (modular) negation. Computes -self, wrapping around at the boundary of the type.

Since unsigned types do not have negative equivalents all applications of this function will wrap (except for -0). For values smaller than the corresponding signed type’s maximum the result is the same as casting the corresponding signed value. Any larger values are equivalent to MAX + 1 - (val - MAX - 1) where MAX is the corresponding signed type’s maximum.

Examples

Basic usage:

Please note that this example is shared between integer types. Which explains why i8 is used here.

assert_eq!(100i8.wrapping_neg(), -100);
assert_eq!((-128i8).wrapping_neg(), -128);

Panic-free bitwise shift-left; yields self << mask(rhs), where mask removes any high-order bits of rhs that would cause the shift to exceed the bitwidth of the type.

Note that this is not the same as a rotate-left; the RHS of a wrapping shift-left is restricted to the range of the type, rather than the bits shifted out of the LHS being returned to the other end. The primitive integer types all implement a rotate_left function, which may be what you want instead.

Examples

Basic usage:

assert_eq!(1usize.wrapping_shl(7), 128);
assert_eq!(1usize.wrapping_shl(128), 1);

Panic-free bitwise shift-right; yields self >> mask(rhs), where mask removes any high-order bits of rhs that would cause the shift to exceed the bitwidth of the type.

Note that this is not the same as a rotate-right; the RHS of a wrapping shift-right is restricted to the range of the type, rather than the bits shifted out of the LHS being returned to the other end. The primitive integer types all implement a rotate_right function, which may be what you want instead.

Examples

Basic usage:

assert_eq!(128usize.wrapping_shr(7), 1);
assert_eq!(128usize.wrapping_shr(128), 128);

Wrapping (modular) exponentiation. Computes self.pow(exp), wrapping around at the boundary of the type.

Examples

Basic usage:

assert_eq!(3usize.wrapping_pow(5), 243);
assert_eq!(3u8.wrapping_pow(6), 217);

Calculates self + rhs

Returns a tuple of the addition along with a boolean indicating whether an arithmetic overflow would occur. If an overflow would have occurred then the wrapped value is returned.

Examples

Basic usage

assert_eq!(5usize.overflowing_add(2), (7, false));
assert_eq!(usize::MAX.overflowing_add(1), (0, true));

Calculates self - rhs

Returns a tuple of the subtraction along with a boolean indicating whether an arithmetic overflow would occur. If an overflow would have occurred then the wrapped value is returned.

Examples

Basic usage

assert_eq!(5usize.overflowing_sub(2), (3, false));
assert_eq!(0usize.overflowing_sub(1), (usize::MAX, true));

Calculates the multiplication of self and rhs.

Returns a tuple of the multiplication along with a boolean indicating whether an arithmetic overflow would occur. If an overflow would have occurred then the wrapped value is returned.

Examples

Basic usage:

Please note that this example is shared between integer types. Which explains why u32 is used here.

assert_eq!(5u32.overflowing_mul(2), (10, false));
assert_eq!(1_000_000_000u32.overflowing_mul(10), (1410065408, true));

Calculates the divisor when self is divided by rhs.

Returns a tuple of the divisor along with a boolean indicating whether an arithmetic overflow would occur. Note that for unsigned integers overflow never occurs, so the second value is always false.

Panics

This function will panic if rhs is 0.

Examples

Basic usage

assert_eq!(5usize.overflowing_div(2), (2, false));

Calculates the quotient of Euclidean division self.div_euclid(rhs).

Returns a tuple of the divisor along with a boolean indicating whether an arithmetic overflow would occur. Note that for unsigned integers overflow never occurs, so the second value is always false. Since, for the positive integers, all common definitions of division are equal, this is exactly equal to self.overflowing_div(rhs).

Panics

This function will panic if rhs is 0.

Examples

Basic usage

assert_eq!(5usize.overflowing_div_euclid(2), (2, false));

Calculates the remainder when self is divided by rhs.

Returns a tuple of the remainder after dividing along with a boolean indicating whether an arithmetic overflow would occur. Note that for unsigned integers overflow never occurs, so the second value is always false.

Panics

This function will panic if rhs is 0.

Examples

Basic usage

assert_eq!(5usize.overflowing_rem(2), (1, false));

Calculates the remainder self.rem_euclid(rhs) as if by Euclidean division.

Returns a tuple of the modulo after dividing along with a boolean indicating whether an arithmetic overflow would occur. Note that for unsigned integers overflow never occurs, so the second value is always false. Since, for the positive integers, all common definitions of division are equal, this operation is exactly equal to self.overflowing_rem(rhs).

Panics

This function will panic if rhs is 0.

Examples

Basic usage

assert_eq!(5usize.overflowing_rem_euclid(2), (1, false));

Negates self in an overflowing fashion.

Returns !self + 1 using wrapping operations to return the value that represents the negation of this unsigned value. Note that for positive unsigned values overflow always occurs, but negating 0 does not overflow.

Examples

Basic usage

assert_eq!(0usize.overflowing_neg(), (0, false));
assert_eq!(2usize.overflowing_neg(), (-2i32 as usize, true));

Shifts self left by rhs bits.

Returns a tuple of the shifted version of self along with a boolean indicating whether the shift value was larger than or equal to the number of bits. If the shift value is too large, then value is masked (N-1) where N is the number of bits, and this value is then used to perform the shift.

Examples

Basic usage

assert_eq!(0x1usize.overflowing_shl(4), (0x10, false));
assert_eq!(0x1usize.overflowing_shl(132), (0x10, true));

Shifts self right by rhs bits.

Returns a tuple of the shifted version of self along with a boolean indicating whether the shift value was larger than or equal to the number of bits. If the shift value is too large, then value is masked (N-1) where N is the number of bits, and this value is then used to perform the shift.

Examples

Basic usage

assert_eq!(0x10usize.overflowing_shr(4), (0x1, false));
assert_eq!(0x10usize.overflowing_shr(132), (0x1, true));

Raises self to the power of exp, using exponentiation by squaring.

Returns a tuple of the exponentiation along with a bool indicating whether an overflow happened.

Examples

Basic usage:

assert_eq!(3usize.overflowing_pow(5), (243, false));
assert_eq!(3u8.overflowing_pow(6), (217, true));

Raises self to the power of exp, using exponentiation by squaring.

Examples

Basic usage:

assert_eq!(2usize.pow(5), 32);

Performs Euclidean division.

Since, for the positive integers, all common definitions of division are equal, this is exactly equal to self / rhs.

Panics

This function will panic if rhs is 0.

Examples

Basic usage:

assert_eq!(7usize.div_euclid(4), 1); // or any other integer type

Calculates the least remainder of self (mod rhs).

Since, for the positive integers, all common definitions of division are equal, this is exactly equal to self % rhs.

Panics

This function will panic if rhs is 0.

Examples

Basic usage:

assert_eq!(7usize.rem_euclid(4), 3); // or any other integer type

Returns true if and only if self == 2^k for some k.

Examples

Basic usage:

assert!(16usize.is_power_of_two());
assert!(!10usize.is_power_of_two());

Returns the smallest power of two greater than or equal to self.

When return value overflows (i.e., self > (1 << (N-1)) for type uN), it panics in debug mode and return value is wrapped to 0 in release mode (the only situation in which method can return 0).

Examples

Basic usage:

assert_eq!(2usize.next_power_of_two(), 2);
assert_eq!(3usize.next_power_of_two(), 4);

Returns the smallest power of two greater than or equal to n. If the next power of two is greater than the type’s maximum value, None is returned, otherwise the power of two is wrapped in Some.

Examples

Basic usage:

assert_eq!(2usize.checked_next_power_of_two(), Some(2));
assert_eq!(3usize.checked_next_power_of_two(), Some(4));
assert_eq!(usize::MAX.checked_next_power_of_two(), None);

Returns the smallest power of two greater than or equal to n. If the next power of two is greater than the type’s maximum value, the return value is wrapped to 0.

Examples

Basic usage:

#![feature(wrapping_next_power_of_two)]

assert_eq!(2usize.wrapping_next_power_of_two(), 2);
assert_eq!(3usize.wrapping_next_power_of_two(), 4);
assert_eq!(usize::MAX.wrapping_next_power_of_two(), 0);

Return the memory representation of this integer as a byte array in big-endian (network) byte order.

Note: This function returns an array of length 2, 4 or 8 bytes depending on the target pointer size.

Examples

let bytes = 0x1234567890123456usize.to_be_bytes();
assert_eq!(bytes, [0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]);

Return the memory representation of this integer as a byte array in little-endian byte order.

Note: This function returns an array of length 2, 4 or 8 bytes depending on the target pointer size.

Examples

let bytes = 0x1234567890123456usize.to_le_bytes();
assert_eq!(bytes, [0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]);

Return the memory representation of this integer as a byte array in native byte order.

As the target platform’s native endianness is used, portable code should use to_be_bytes or to_le_bytes, as appropriate, instead.

Note: This function returns an array of length 2, 4 or 8 bytes depending on the target pointer size.

Examples

let bytes = 0x1234567890123456usize.to_ne_bytes();
assert_eq!(
    bytes,
    if cfg!(target_endian = "big") {
        [0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]
    } else {
        [0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]
    }
);

Return the memory representation of this integer as a byte array in native byte order.

to_ne_bytes should be preferred over this whenever possible.

Examples

#![feature(num_as_ne_bytes)]
let num = 0x1234567890123456usize;
let bytes = num.as_ne_bytes();
assert_eq!(
    bytes,
    if cfg!(target_endian = "big") {
        &[0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]
    } else {
        &[0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]
    }
);

Create a native endian integer value from its representation as a byte array in big endian.

Note: This function takes an array of length 2, 4 or 8 bytes depending on the target pointer size.

Examples

let value = usize::from_be_bytes([0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]);
assert_eq!(value, 0x1234567890123456);

When starting from a slice rather than an array, fallible conversion APIs can be used:

use std::convert::TryInto;

fn read_be_usize(input: &mut &[u8]) -> usize {
    let (int_bytes, rest) = input.split_at(std::mem::size_of::<usize>());
    *input = rest;
    usize::from_be_bytes(int_bytes.try_into().unwrap())
}

Create a native endian integer value from its representation as a byte array in little endian.

Note: This function takes an array of length 2, 4 or 8 bytes depending on the target pointer size.

Examples

let value = usize::from_le_bytes([0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]);
assert_eq!(value, 0x1234567890123456);

When starting from a slice rather than an array, fallible conversion APIs can be used:

use std::convert::TryInto;

fn read_le_usize(input: &mut &[u8]) -> usize {
    let (int_bytes, rest) = input.split_at(std::mem::size_of::<usize>());
    *input = rest;
    usize::from_le_bytes(int_bytes.try_into().unwrap())
}

Create a native endian integer value from its memory representation as a byte array in native endianness.

As the target platform’s native endianness is used, portable code likely wants to use from_be_bytes or from_le_bytes, as appropriate instead.

Note: This function takes an array of length 2, 4 or 8 bytes depending on the target pointer size.

Examples

let value = usize::from_ne_bytes(if cfg!(target_endian = "big") {
    [0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]
} else {
    [0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]
});
assert_eq!(value, 0x1234567890123456);

When starting from a slice rather than an array, fallible conversion APIs can be used:

use std::convert::TryInto;

fn read_ne_usize(input: &mut &[u8]) -> usize {
    let (int_bytes, rest) = input.split_at(std::mem::size_of::<usize>());
    *input = rest;
    usize::from_ne_bytes(int_bytes.try_into().unwrap())
}

New code should prefer to use usize::MIN instead.

Returns the smallest value that can be represented by this integer type.

New code should prefer to use usize::MAX instead.

Returns the largest value that can be represented by this integer type.