Primitive Type usize
Operations and constants for pointer-sized unsigned integers (usize type)
This type was recently added to replace uint. The rollout of the
new type will gradually take place over the alpha cycle along with
the development of clearer conventions around integer types.
Methods
impl usize
fn min_value() -> usize
Returns the smallest value that can be represented by this integer type.
fn max_value() -> usize
Returns the largest value that can be represented by this integer type.
fn from_str_radix(src: &str, radix: u32) -> Result<usize, ParseIntError>
Converts a string slice in a given base to an integer.
Leading and trailing whitespace represent an error.
Arguments
- src - A string slice
- radix - The base to use. Must lie in the range [2 .. 36]
Return value
Err(ParseIntError) if the string did not represent a valid number.
Otherwise, Ok(n) where n is the integer represented by src.
fn count_ones(self) -> u32
Returns the number of ones in the binary representation of self.
Examples
fn main() { let n = 0b01001100u8; assert_eq!(n.count_ones(), 3); }let n = 0b01001100u8; assert_eq!(n.count_ones(), 3);
fn count_zeros(self) -> u32
Returns the number of zeros in the binary representation of self.
Examples
fn main() { let n = 0b01001100u8; assert_eq!(n.count_zeros(), 5); }let n = 0b01001100u8; assert_eq!(n.count_zeros(), 5);
fn leading_zeros(self) -> u32
Returns the number of leading zeros in the binary representation
of self.
Examples
fn main() { let n = 0b0101000u16; assert_eq!(n.leading_zeros(), 10); }let n = 0b0101000u16; assert_eq!(n.leading_zeros(), 10);
fn trailing_zeros(self) -> u32
Returns the number of trailing zeros in the binary representation
of self.
Examples
fn main() { let n = 0b0101000u16; assert_eq!(n.trailing_zeros(), 3); }let n = 0b0101000u16; assert_eq!(n.trailing_zeros(), 3);
fn rotate_left(self, n: u32) -> usize
Shifts the bits to the left by a specified amount, n,
wrapping the truncated bits to the end of the resulting integer.
Examples
fn main() { let n = 0x0123456789ABCDEFu64; let m = 0x3456789ABCDEF012u64; assert_eq!(n.rotate_left(12), m); }let n = 0x0123456789ABCDEFu64; let m = 0x3456789ABCDEF012u64; assert_eq!(n.rotate_left(12), m);
fn rotate_right(self, n: u32) -> usize
Shifts the bits to the right by a specified amount, n,
wrapping the truncated bits to the beginning of the resulting
integer.
Examples
fn main() { let n = 0x0123456789ABCDEFu64; let m = 0xDEF0123456789ABCu64; assert_eq!(n.rotate_right(12), m); }let n = 0x0123456789ABCDEFu64; let m = 0xDEF0123456789ABCu64; assert_eq!(n.rotate_right(12), m);
fn swap_bytes(self) -> usize
Reverses the byte order of the integer.
Examples
fn main() { let n = 0x0123456789ABCDEFu64; let m = 0xEFCDAB8967452301u64; assert_eq!(n.swap_bytes(), m); }let n = 0x0123456789ABCDEFu64; let m = 0xEFCDAB8967452301u64; assert_eq!(n.swap_bytes(), m);
fn from_be(x: usize) -> usize
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
fn main() { let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "big") { assert_eq!(u64::from_be(n), n) } else { assert_eq!(u64::from_be(n), n.swap_bytes()) } }let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "big") { assert_eq!(u64::from_be(n), n) } else { assert_eq!(u64::from_be(n), n.swap_bytes()) }
fn from_le(x: usize) -> usize
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
fn main() { let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "little") { assert_eq!(u64::from_le(n), n) } else { assert_eq!(u64::from_le(n), n.swap_bytes()) } }let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "little") { assert_eq!(u64::from_le(n), n) } else { assert_eq!(u64::from_le(n), n.swap_bytes()) }
fn to_be(self) -> usize
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
fn main() { let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "big") { assert_eq!(n.to_be(), n) } else { assert_eq!(n.to_be(), n.swap_bytes()) } }let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "big") { assert_eq!(n.to_be(), n) } else { assert_eq!(n.to_be(), n.swap_bytes()) }
fn to_le(self) -> usize
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
fn main() { let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "little") { assert_eq!(n.to_le(), n) } else { assert_eq!(n.to_le(), n.swap_bytes()) } }let n = 0x0123456789ABCDEFu64; if cfg!(target_endian = "little") { assert_eq!(n.to_le(), n) } else { assert_eq!(n.to_le(), n.swap_bytes()) }
fn checked_add(self, other: usize) -> Option<usize>
Checked integer addition. Computes self + other, returning None
if overflow occurred.
Examples
fn main() { assert_eq!(5u16.checked_add(65530), Some(65535)); assert_eq!(6u16.checked_add(65530), None); }assert_eq!(5u16.checked_add(65530), Some(65535)); assert_eq!(6u16.checked_add(65530), None);
fn checked_sub(self, other: usize) -> Option<usize>
Checked integer subtraction. Computes self - other, returning
None if underflow occurred.
Examples
fn main() { assert_eq!((-127i8).checked_sub(1), Some(-128)); assert_eq!((-128i8).checked_sub(1), None); }assert_eq!((-127i8).checked_sub(1), Some(-128)); assert_eq!((-128i8).checked_sub(1), None);
fn checked_mul(self, other: usize) -> Option<usize>
Checked integer multiplication. Computes self * other, returning
None if underflow or overflow occurred.
Examples
fn main() { assert_eq!(5u8.checked_mul(51), Some(255)); assert_eq!(5u8.checked_mul(52), None); }assert_eq!(5u8.checked_mul(51), Some(255)); assert_eq!(5u8.checked_mul(52), None);
fn checked_div(self, v: usize) -> Option<usize>
Checked integer division. Computes self / other, returning None
if other == 0 or the operation results in underflow or overflow.
Examples
fn main() { assert_eq!((-127i8).checked_div(-1), Some(127)); assert_eq!((-128i8).checked_div(-1), None); assert_eq!((1i8).checked_div(0), None); }assert_eq!((-127i8).checked_div(-1), Some(127)); assert_eq!((-128i8).checked_div(-1), None); assert_eq!((1i8).checked_div(0), None);
fn saturating_add(self, other: usize) -> usize
Saturating integer addition. Computes self + other, saturating at
the numeric bounds instead of overflowing.
fn saturating_sub(self, other: usize) -> usize
Saturating integer subtraction. Computes self - other, saturating
at the numeric bounds instead of overflowing.
fn wrapping_add(self, rhs: usize) -> usize
Wrapping (modular) addition. Computes self + other,
wrapping around at the boundary of the type.
fn wrapping_sub(self, rhs: usize) -> usize
Wrapping (modular) subtraction. Computes self - other,
wrapping around at the boundary of the type.
fn wrapping_mul(self, rhs: usize) -> usize
Wrapping (modular) multiplication. Computes self * other, wrapping around at the boundary of the type.
fn pow(self, exp: u32) -> usize
Raises self to the power of exp, using exponentiation by squaring.
Examples
fn main() { assert_eq!(2i32.pow(4), 16); }assert_eq!(2i32.pow(4), 16);
fn is_power_of_two(self) -> bool
Returns true iff self == 2^k for some k.
fn next_power_of_two(self) -> usize
Returns the smallest power of two greater than or equal to self.
Unspecified behavior on overflow.
fn checked_next_power_of_two(self) -> Option<usize>
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.