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

Examples

Basic usage:

assert_eq!(u8::MIN, 0);

The largest value that can be represented by this integer type (2⁸ − 1).

Examples

Basic usage:

assert_eq!(u8::MAX, 255);

The size of this integer type in bits.

Examples

assert_eq!(u8::BITS, 8);

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!(u8::from_str_radix("A", 16), Ok(10));

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

Examples

Basic usage:

let n = 0b01001100u8;

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

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

Examples

Basic usage:

assert_eq!(u8::MAX.count_zeros(), 0);

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

Depending on what you’re doing with the value, you might also be interested in the ilog2 function which returns a consistent number, even if the type widens.

Examples

Basic usage:

let n = u8::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 = 0b0101000u8;

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

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

Examples

Basic usage:

let n = !(u8::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 = 0b1010111u8;

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 = 0x82u8;
let m = 0xa;

assert_eq!(n.rotate_left(2), 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 = 0xau8;
let m = 0x82;

assert_eq!(n.rotate_right(2), m);

Reverses the byte order of the integer.

Examples

Basic usage:

let n = 0x12u8;
let m = n.swap_bytes();

assert_eq!(m, 0x12);

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 = 0x12u8;
let m = n.reverse_bits();

assert_eq!(m, 0x48);
assert_eq!(0, 0u8.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 = 0x1Au8;

if cfg!(target_endian = "big") {
    assert_eq!(u8::from_be(n), n)
} else {
    assert_eq!(u8::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 = 0x1Au8;

if cfg!(target_endian = "little") {
    assert_eq!(u8::from_le(n), n)
} else {
    assert_eq!(u8::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 = 0x1Au8;

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 = 0x1Au8;

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!((u8::MAX - 2).checked_add(1), Some(u8::MAX - 1));
assert_eq!((u8::MAX - 2).checked_add(3), None);

Unchecked integer addition. Computes self + rhs, assuming overflow cannot occur.

Safety

This results in undefined behavior when self + rhs > u8::MAX or self + rhs < u8::MIN, i.e. when checked_add would return None.

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

Examples

Basic usage:

assert_eq!(1u8.checked_add_signed(2), Some(3));
assert_eq!(1u8.checked_add_signed(-2), None);
assert_eq!((u8::MAX - 2).checked_add_signed(3), None);

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

Examples

Basic usage:

assert_eq!(1u8.checked_sub(1), Some(0));
assert_eq!(0u8.checked_sub(1), None);

Unchecked integer subtraction. Computes self - rhs, assuming overflow cannot occur.

Safety

This results in undefined behavior when self - rhs > u8::MAX or self - rhs < u8::MIN, i.e. when checked_sub would return None.

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

Examples

Basic usage:

assert_eq!(5u8.checked_mul(1), Some(5));
assert_eq!(u8::MAX.checked_mul(2), None);

Unchecked integer multiplication. Computes self * rhs, assuming overflow cannot occur.

Safety

This results in undefined behavior when self * rhs > u8::MAX or self * rhs < u8::MIN, i.e. when checked_mul would return None.

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

Examples

Basic usage:

assert_eq!(128u8.checked_div(2), Some(64));
assert_eq!(1u8.checked_div(0), None);

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

Examples

Basic usage:

assert_eq!(128u8.checked_div_euclid(2), Some(64));
assert_eq!(1u8.checked_div_euclid(0), None);

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

Examples

Basic usage:

assert_eq!(5u8.checked_rem(2), Some(1));
assert_eq!(5u8.checked_rem(0), None);

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

Examples

Basic usage:

assert_eq!(5u8.checked_rem_euclid(2), Some(1));
assert_eq!(5u8.checked_rem_euclid(0), None);

Returns the logarithm of the number with respect to an arbitrary base, rounded down.

This method might not be optimized owing to implementation details; ilog2 can produce results more efficiently for base 2, and ilog10 can produce results more efficiently for base 10.

Panics

This function will panic if self is zero, or if base is less than 2.

Examples

assert_eq!(5u8.ilog(5), 1);

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

Panics

This function will panic if self is zero.

Examples

assert_eq!(2u8.ilog2(), 1);

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

Panics

This function will panic if self is zero.

Example

assert_eq!(10u8.ilog10(), 1);

Returns the logarithm of the number with respect to an arbitrary base, rounded down.

Returns None if the number is zero, or if the base is not at least 2.

This method might not be optimized owing to implementation details; checked_ilog2 can produce results more efficiently for base 2, and checked_ilog10 can produce results more efficiently for base 10.

Examples

assert_eq!(5u8.checked_ilog(5), Some(1));

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

Returns None if the number is zero.

Examples

assert_eq!(2u8.checked_ilog2(), Some(1));

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

Returns None if the number is zero.

Examples

assert_eq!(10u8.checked_ilog10(), Some(1));

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

Note that negating any positive integer will overflow.

Examples

Basic usage:

assert_eq!(0u8.checked_neg(), Some(0));
assert_eq!(1u8.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!(0x1u8.checked_shl(4), Some(0x10));
assert_eq!(0x10u8.checked_shl(129), None);

Unchecked shift left. Computes self << rhs, assuming that rhs is less than the number of bits in self.

Safety

This results in undefined behavior if rhs is larger than or equal to the number of bits in self, i.e. when checked_shl would return 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!(0x10u8.checked_shr(4), Some(0x1));
assert_eq!(0x10u8.checked_shr(129), None);

Unchecked shift right. Computes self >> rhs, assuming that rhs is less than the number of bits in self.

Safety

This results in undefined behavior if rhs is larger than or equal to the number of bits in self, i.e. when checked_shr would return None.

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

Examples

Basic usage:

assert_eq!(2u8.checked_pow(5), Some(32));
assert_eq!(u8::MAX.checked_pow(2), None);

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

Examples

Basic usage:

assert_eq!(100u8.saturating_add(1), 101);
assert_eq!(u8::MAX.saturating_add(127), u8::MAX);

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

Examples

Basic usage:

assert_eq!(1u8.saturating_add_signed(2), 3);
assert_eq!(1u8.saturating_add_signed(-2), 0);
assert_eq!((u8::MAX - 2).saturating_add_signed(4), u8::MAX);

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

Examples

Basic usage:

assert_eq!(100u8.saturating_sub(27), 73);
assert_eq!(13u8.saturating_sub(127), 0);

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

Examples

Basic usage:

assert_eq!(2u8.saturating_mul(10), 20);
assert_eq!((u8::MAX).saturating_mul(10), u8::MAX);

Saturating integer division. Computes self / rhs, saturating at the numeric bounds instead of overflowing.

Examples

Basic usage:

assert_eq!(5u8.saturating_div(2), 2);

let _ = 1u8.saturating_div(0);

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

Examples

Basic usage:

assert_eq!(4u8.saturating_pow(3), 64);
assert_eq!(u8::MAX.saturating_pow(2), u8::MAX);

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

Examples

Basic usage:

assert_eq!(200u8.wrapping_add(55), 255);
assert_eq!(200u8.wrapping_add(u8::MAX), 199);

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

Examples

Basic usage:

assert_eq!(1u8.wrapping_add_signed(2), 3);
assert_eq!(1u8.wrapping_add_signed(-2), u8::MAX);
assert_eq!((u8::MAX - 2).wrapping_add_signed(4), 1);

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

Examples

Basic usage:

assert_eq!(100u8.wrapping_sub(100), 0);
assert_eq!(100u8.wrapping_sub(u8::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.

Panics

This function will panic if rhs is 0.

Examples

Basic usage:

assert_eq!(100u8.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).

Panics

This function will panic if rhs is 0.

Examples

Basic usage:

assert_eq!(100u8.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.

Panics

This function will panic if rhs is 0.

Examples

Basic usage:

assert_eq!(100u8.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).

Panics

This function will panic if rhs is 0.

Examples

Basic usage:

assert_eq!(100u8.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:

assert_eq!(0_u8.wrapping_neg(), 0);
assert_eq!(u8::MAX.wrapping_neg(), 1);
assert_eq!(13_u8.wrapping_neg(), (!13) + 1);
assert_eq!(42_u8.wrapping_neg(), !(42 - 1));

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!(1u8.wrapping_shl(7), 128);
assert_eq!(1u8.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!(128u8.wrapping_shr(7), 1);
assert_eq!(128u8.wrapping_shr(128), 128);

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

Examples

Basic usage:

assert_eq!(3u8.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!(5u8.overflowing_add(2), (7, false));
assert_eq!(u8::MAX.overflowing_add(1), (0, true));

Calculates self + rhs + carry and returns a tuple containing the sum and the output carry.

Performs “ternary addition” of two integer operands and a carry-in bit, and returns an output integer and a carry-out bit. This allows chaining together multiple additions to create a wider addition, and can be useful for bignum addition.

This can be thought of as a 8-bit “full adder”, in the electronics sense.

If the input carry is false, this method is equivalent to overflowing_add, and the output carry is equal to the overflow flag. Note that although carry and overflow flags are similar for unsigned integers, they are different for signed integers.

Examples

#![feature(bigint_helper_methods)]

//    3  MAX    (a = 3 × 2^8 + 2^8 - 1)
// +  5    7    (b = 5 × 2^8 + 7)
// ---------
//    9    6    (sum = 9 × 2^8 + 6)

let (a1, a0): (u8, u8) = (3, u8::MAX);
let (b1, b0): (u8, u8) = (5, 7);
let carry0 = false;

let (sum0, carry1) = a0.carrying_add(b0, carry0);
assert_eq!(carry1, true);
let (sum1, carry2) = a1.carrying_add(b1, carry1);
assert_eq!(carry2, false);

assert_eq!((sum1, sum0), (9, 6));

Calculates self + rhs with a signed 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!(1u8.overflowing_add_signed(2), (3, false));
assert_eq!(1u8.overflowing_add_signed(-2), (u8::MAX, true));
assert_eq!((u8::MAX - 2).overflowing_add_signed(4), (1, 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!(5u8.overflowing_sub(2), (3, false));
assert_eq!(0u8.overflowing_sub(1), (u8::MAX, true));

Calculates self − rhs − borrow and returns a tuple containing the difference and the output borrow.

Performs “ternary subtraction” by subtracting both an integer operand and a borrow-in bit from self, and returns an output integer and a borrow-out bit. This allows chaining together multiple subtractions to create a wider subtraction, and can be useful for bignum subtraction.

Examples

#![feature(bigint_helper_methods)]

//    9    6    (a = 9 × 2^8 + 6)
// -  5    7    (b = 5 × 2^8 + 7)
// ---------
//    3  MAX    (diff = 3 × 2^8 + 2^8 - 1)

let (a1, a0): (u8, u8) = (9, 6);
let (b1, b0): (u8, u8) = (5, 7);
let borrow0 = false;

let (diff0, borrow1) = a0.borrowing_sub(b0, borrow0);
assert_eq!(borrow1, true);
let (diff1, borrow2) = a1.borrowing_sub(b1, borrow1);
assert_eq!(borrow2, false);

assert_eq!((diff1, diff0), (3, u8::MAX));

Computes the absolute difference between self and other.

Examples

Basic usage:

assert_eq!(100u8.abs_diff(80), 20u8);
assert_eq!(100u8.abs_diff(110), 10u8);

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!(5u8.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!(5u8.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!(5u8.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!(5u8.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!(0u8.overflowing_neg(), (0, false));
assert_eq!(2u8.overflowing_neg(), (-2i32 as u8, 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!(0x1u8.overflowing_shl(4), (0x10, false));
assert_eq!(0x1u8.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!(0x10u8.overflowing_shr(4), (0x1, false));
assert_eq!(0x10u8.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!(3u8.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!(2u8.pow(5), 32);

Returns the square root of the number, rounded down.

Examples

Basic usage:

#![feature(isqrt)]
assert_eq!(10u8.isqrt(), 3);

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!(7u8.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!(7u8.rem_euclid(4), 3); // or any other integer type

Calculates the quotient of self and rhs, rounding the result towards negative infinity.

This is the same as performing self / rhs for all unsigned integers.

Panics

This function will panic if rhs is zero.

Examples

Basic usage:

#![feature(int_roundings)]
assert_eq!(7_u8.div_floor(4), 1);

Calculates the quotient of self and rhs, rounding the result towards positive infinity.

Panics

This function will panic if rhs is zero.

Overflow behavior

On overflow, this function will panic if overflow checks are enabled (default in debug mode) and wrap if overflow checks are disabled (default in release mode).

Examples

Basic usage:

assert_eq!(7_u8.div_ceil(4), 2);

Calculates the smallest value greater than or equal to self that is a multiple of rhs.

Panics

This function will panic if rhs is zero.

Overflow behavior

On overflow, this function will panic if overflow checks are enabled (default in debug mode) and wrap if overflow checks are disabled (default in release mode).

Examples

Basic usage:

assert_eq!(16_u8.next_multiple_of(8), 16);
assert_eq!(23_u8.next_multiple_of(8), 24);

Calculates the smallest value greater than or equal to self that is a multiple of rhs. Returns None if rhs is zero or the operation would result in overflow.

Examples

Basic usage:

assert_eq!(16_u8.checked_next_multiple_of(8), Some(16));
assert_eq!(23_u8.checked_next_multiple_of(8), Some(24));
assert_eq!(1_u8.checked_next_multiple_of(0), None);
assert_eq!(u8::MAX.checked_next_multiple_of(2), None);

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

Examples

Basic usage:

assert!(16u8.is_power_of_two());
assert!(!10u8.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 the return value is wrapped to 0 in release mode (the only situation in which method can return 0).

Examples

Basic usage:

assert_eq!(2u8.next_power_of_two(), 2);
assert_eq!(3u8.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!(2u8.checked_next_power_of_two(), Some(2));
assert_eq!(3u8.checked_next_power_of_two(), Some(4));
assert_eq!(u8::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!(2u8.wrapping_next_power_of_two(), 2);
assert_eq!(3u8.wrapping_next_power_of_two(), 4);
assert_eq!(u8::MAX.wrapping_next_power_of_two(), 0);

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

Examples

let bytes = 0x12u8.to_be_bytes();
assert_eq!(bytes, [0x12]);

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

Examples

let bytes = 0x12u8.to_le_bytes();
assert_eq!(bytes, [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.

Examples

let bytes = 0x12u8.to_ne_bytes();
assert_eq!(
    bytes,
    if cfg!(target_endian = "big") {
        [0x12]
    } else {
        [0x12]
    }
);

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

Examples

let value = u8::from_be_bytes([0x12]);
assert_eq!(value, 0x12);

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

fn read_be_u8(input: &mut &[u8]) -> u8 {
    let (int_bytes, rest) = input.split_at(std::mem::size_of::<u8>());
    *input = rest;
    u8::from_be_bytes(int_bytes.try_into().unwrap())
}

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

Examples

let value = u8::from_le_bytes([0x12]);
assert_eq!(value, 0x12);

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

fn read_le_u8(input: &mut &[u8]) -> u8 {
    let (int_bytes, rest) = input.split_at(std::mem::size_of::<u8>());
    *input = rest;
    u8::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.

Examples

let value = u8::from_ne_bytes(if cfg!(target_endian = "big") {
    [0x12]
} else {
    [0x12]
});
assert_eq!(value, 0x12);

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

fn read_ne_u8(input: &mut &[u8]) -> u8 {
    let (int_bytes, rest) = input.split_at(std::mem::size_of::<u8>());
    *input = rest;
    u8::from_ne_bytes(int_bytes.try_into().unwrap())
}

New code should prefer to use u8::MIN instead.

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

New code should prefer to use u8::MAX instead.

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

Calculates the complete product self * rhs without the possibility to overflow.

This returns the low-order (wrapping) bits and the high-order (overflow) bits of the result as two separate values, in that order.

If you also need to add a carry to the wide result, then you want Self::carrying_mul instead.

Examples

Basic usage:

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

#![feature(bigint_helper_methods)]
assert_eq!(5u32.widening_mul(2), (10, 0));
assert_eq!(1_000_000_000u32.widening_mul(10), (1410065408, 2));

Calculates the “full multiplication” self * rhs + carry without the possibility to overflow.

This returns the low-order (wrapping) bits and the high-order (overflow) bits of the result as two separate values, in that order.

Performs “long multiplication” which takes in an extra amount to add, and may return an additional amount of overflow. This allows for chaining together multiple multiplications to create “big integers” which represent larger values.

If you don’t need the carry, then you can use Self::widening_mul instead.

Examples

Basic usage:

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

#![feature(bigint_helper_methods)]
assert_eq!(5u32.carrying_mul(2, 0), (10, 0));
assert_eq!(5u32.carrying_mul(2, 10), (20, 0));
assert_eq!(1_000_000_000u32.carrying_mul(10, 0), (1410065408, 2));
assert_eq!(1_000_000_000u32.carrying_mul(10, 10), (1410065418, 2));
assert_eq!(u8::MAX.carrying_mul(u8::MAX, u8::MAX), (0, u8::MAX));

This is the core operation needed for scalar multiplication when implementing it for wider-than-native types.

#![feature(bigint_helper_methods)]
fn scalar_mul_eq(little_endian_digits: &mut Vec<u16>, multiplicand: u16) {
    let mut carry = 0;
    for d in little_endian_digits.iter_mut() {
        (*d, carry) = d.carrying_mul(multiplicand, carry);
    }
    if carry != 0 {
        little_endian_digits.push(carry);
    }
}

let mut v = vec![10, 20];
scalar_mul_eq(&mut v, 3);
assert_eq!(v, [30, 60]);

assert_eq!(0x87654321_u64 * 0xFEED, 0x86D3D159E38D);
let mut v = vec![0x4321, 0x8765];
scalar_mul_eq(&mut v, 0xFEED);
assert_eq!(v, [0xE38D, 0xD159, 0x86D3]);

If carry is zero, this is similar to overflowing_mul, except that it gives the value of the overflow instead of just whether one happened:

#![feature(bigint_helper_methods)]
let r = u8::carrying_mul(7, 13, 0);
assert_eq!((r.0, r.1 != 0), u8::overflowing_mul(7, 13));
let r = u8::carrying_mul(13, 42, 0);
assert_eq!((r.0, r.1 != 0), u8::overflowing_mul(13, 42));

The value of the first field in the returned tuple matches what you’d get by combining the wrapping_mul and wrapping_add methods:

#![feature(bigint_helper_methods)]
assert_eq!(
    789_u16.carrying_mul(456, 123).0,
    789_u16.wrapping_mul(456).wrapping_add(123),
);

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)]
assert_eq!(0u8.midpoint(4), 2);
assert_eq!(1u8.midpoint(4), 2);

Checks if the value is within the ASCII range.

Examples

let ascii = 97u8;
let non_ascii = 150u8;

assert!(ascii.is_ascii());
assert!(!non_ascii.is_ascii());

If the value of this byte is within the ASCII range, returns it as an ASCII character. Otherwise, returns None.

Makes a copy of the value in its ASCII upper case equivalent.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To uppercase the value in-place, use make_ascii_uppercase.

Examples

let lowercase_a = 97u8;

assert_eq!(65, lowercase_a.to_ascii_uppercase());

Makes a copy of the value in its ASCII lower case equivalent.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To lowercase the value in-place, use make_ascii_lowercase.

Examples

let uppercase_a = 65u8;

assert_eq!(97, uppercase_a.to_ascii_lowercase());

Checks that two values are an ASCII case-insensitive match.

This is equivalent to to_ascii_lowercase(a) == to_ascii_lowercase(b).

Examples

let lowercase_a = 97u8;
let uppercase_a = 65u8;

assert!(lowercase_a.eq_ignore_ascii_case(&uppercase_a));

Converts this value to its ASCII upper case equivalent in-place.

ASCII letters ‘a’ to ‘z’ are mapped to ‘A’ to ‘Z’, but non-ASCII letters are unchanged.

To return a new uppercased value without modifying the existing one, use to_ascii_uppercase.

Examples

let mut byte = b'a';

byte.make_ascii_uppercase();

assert_eq!(b'A', byte);

Converts this value to its ASCII lower case equivalent in-place.

ASCII letters ‘A’ to ‘Z’ are mapped to ‘a’ to ‘z’, but non-ASCII letters are unchanged.

To return a new lowercased value without modifying the existing one, use to_ascii_lowercase.

Examples

let mut byte = b'A';

byte.make_ascii_lowercase();

assert_eq!(b'a', byte);

Checks if the value is an ASCII alphabetic character:

• U+0041 ‘A’ ..= U+005A ‘Z’, or
• U+0061 ‘a’ ..= U+007A ‘z’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(uppercase_a.is_ascii_alphabetic());
assert!(uppercase_g.is_ascii_alphabetic());
assert!(a.is_ascii_alphabetic());
assert!(g.is_ascii_alphabetic());
assert!(!zero.is_ascii_alphabetic());
assert!(!percent.is_ascii_alphabetic());
assert!(!space.is_ascii_alphabetic());
assert!(!lf.is_ascii_alphabetic());
assert!(!esc.is_ascii_alphabetic());

Checks if the value is an ASCII uppercase character: U+0041 ‘A’ ..= U+005A ‘Z’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(uppercase_a.is_ascii_uppercase());
assert!(uppercase_g.is_ascii_uppercase());
assert!(!a.is_ascii_uppercase());
assert!(!g.is_ascii_uppercase());
assert!(!zero.is_ascii_uppercase());
assert!(!percent.is_ascii_uppercase());
assert!(!space.is_ascii_uppercase());
assert!(!lf.is_ascii_uppercase());
assert!(!esc.is_ascii_uppercase());

Checks if the value is an ASCII lowercase character: U+0061 ‘a’ ..= U+007A ‘z’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(!uppercase_a.is_ascii_lowercase());
assert!(!uppercase_g.is_ascii_lowercase());
assert!(a.is_ascii_lowercase());
assert!(g.is_ascii_lowercase());
assert!(!zero.is_ascii_lowercase());
assert!(!percent.is_ascii_lowercase());
assert!(!space.is_ascii_lowercase());
assert!(!lf.is_ascii_lowercase());
assert!(!esc.is_ascii_lowercase());

Checks if the value is an ASCII alphanumeric character:

• U+0041 ‘A’ ..= U+005A ‘Z’, or
• U+0061 ‘a’ ..= U+007A ‘z’, or
• U+0030 ‘0’ ..= U+0039 ‘9’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(uppercase_a.is_ascii_alphanumeric());
assert!(uppercase_g.is_ascii_alphanumeric());
assert!(a.is_ascii_alphanumeric());
assert!(g.is_ascii_alphanumeric());
assert!(zero.is_ascii_alphanumeric());
assert!(!percent.is_ascii_alphanumeric());
assert!(!space.is_ascii_alphanumeric());
assert!(!lf.is_ascii_alphanumeric());
assert!(!esc.is_ascii_alphanumeric());

Checks if the value is an ASCII decimal digit: U+0030 ‘0’ ..= U+0039 ‘9’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(!uppercase_a.is_ascii_digit());
assert!(!uppercase_g.is_ascii_digit());
assert!(!a.is_ascii_digit());
assert!(!g.is_ascii_digit());
assert!(zero.is_ascii_digit());
assert!(!percent.is_ascii_digit());
assert!(!space.is_ascii_digit());
assert!(!lf.is_ascii_digit());
assert!(!esc.is_ascii_digit());

Checks if the value is an ASCII octal digit: U+0030 ‘0’ ..= U+0037 ‘7’.

Examples

#![feature(is_ascii_octdigit)]

let uppercase_a = b'A';
let a = b'a';
let zero = b'0';
let seven = b'7';
let nine = b'9';
let percent = b'%';
let lf = b'\n';

assert!(!uppercase_a.is_ascii_octdigit());
assert!(!a.is_ascii_octdigit());
assert!(zero.is_ascii_octdigit());
assert!(seven.is_ascii_octdigit());
assert!(!nine.is_ascii_octdigit());
assert!(!percent.is_ascii_octdigit());
assert!(!lf.is_ascii_octdigit());

Checks if the value is an ASCII hexadecimal digit:

• U+0030 ‘0’ ..= U+0039 ‘9’, or
• U+0041 ‘A’ ..= U+0046 ‘F’, or
• U+0061 ‘a’ ..= U+0066 ‘f’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(uppercase_a.is_ascii_hexdigit());
assert!(!uppercase_g.is_ascii_hexdigit());
assert!(a.is_ascii_hexdigit());
assert!(!g.is_ascii_hexdigit());
assert!(zero.is_ascii_hexdigit());
assert!(!percent.is_ascii_hexdigit());
assert!(!space.is_ascii_hexdigit());
assert!(!lf.is_ascii_hexdigit());
assert!(!esc.is_ascii_hexdigit());

Checks if the value is an ASCII punctuation character:

• U+0021 ..= U+002F ! " # $ % & ' ( ) * + , - . /, or
• U+003A ..= U+0040 : ; < = > ? @, or
• U+005B ..= U+0060 [ \ ] ^ _ `, or
• U+007B ..= U+007E { | } ~

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(!uppercase_a.is_ascii_punctuation());
assert!(!uppercase_g.is_ascii_punctuation());
assert!(!a.is_ascii_punctuation());
assert!(!g.is_ascii_punctuation());
assert!(!zero.is_ascii_punctuation());
assert!(percent.is_ascii_punctuation());
assert!(!space.is_ascii_punctuation());
assert!(!lf.is_ascii_punctuation());
assert!(!esc.is_ascii_punctuation());

Checks if the value is an ASCII graphic character: U+0021 ‘!’ ..= U+007E ‘~’.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(uppercase_a.is_ascii_graphic());
assert!(uppercase_g.is_ascii_graphic());
assert!(a.is_ascii_graphic());
assert!(g.is_ascii_graphic());
assert!(zero.is_ascii_graphic());
assert!(percent.is_ascii_graphic());
assert!(!space.is_ascii_graphic());
assert!(!lf.is_ascii_graphic());
assert!(!esc.is_ascii_graphic());

Checks if the value is an ASCII whitespace character: U+0020 SPACE, U+0009 HORIZONTAL TAB, U+000A LINE FEED, U+000C FORM FEED, or U+000D CARRIAGE RETURN.

Rust uses the WhatWG Infra Standard’s definition of ASCII whitespace. There are several other definitions in wide use. For instance, the POSIX locale includes U+000B VERTICAL TAB as well as all the above characters, but—from the very same specification—the default rule for “field splitting” in the Bourne shell considers only SPACE, HORIZONTAL TAB, and LINE FEED as whitespace.

If you are writing a program that will process an existing file format, check what that format’s definition of whitespace is before using this function.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(!uppercase_a.is_ascii_whitespace());
assert!(!uppercase_g.is_ascii_whitespace());
assert!(!a.is_ascii_whitespace());
assert!(!g.is_ascii_whitespace());
assert!(!zero.is_ascii_whitespace());
assert!(!percent.is_ascii_whitespace());
assert!(space.is_ascii_whitespace());
assert!(lf.is_ascii_whitespace());
assert!(!esc.is_ascii_whitespace());

Checks if the value is an ASCII control character: U+0000 NUL ..= U+001F UNIT SEPARATOR, or U+007F DELETE. Note that most ASCII whitespace characters are control characters, but SPACE is not.

Examples

let uppercase_a = b'A';
let uppercase_g = b'G';
let a = b'a';
let g = b'g';
let zero = b'0';
let percent = b'%';
let space = b' ';
let lf = b'\n';
let esc = b'\x1b';

assert!(!uppercase_a.is_ascii_control());
assert!(!uppercase_g.is_ascii_control());
assert!(!a.is_ascii_control());
assert!(!g.is_ascii_control());
assert!(!zero.is_ascii_control());
assert!(!percent.is_ascii_control());
assert!(!space.is_ascii_control());
assert!(lf.is_ascii_control());
assert!(esc.is_ascii_control());

Returns an iterator that produces an escaped version of a u8, treating it as an ASCII character.

The behavior is identical to ascii::escape_default.

Examples

assert_eq!("0", b'0'.escape_ascii().to_string());
assert_eq!("\\t", b'\t'.escape_ascii().to_string());
assert_eq!("\\r", b'\r'.escape_ascii().to_string());
assert_eq!("\\n", b'\n'.escape_ascii().to_string());
assert_eq!("\\'", b'\''.escape_ascii().to_string());
assert_eq!("\\\"", b'"'.escape_ascii().to_string());
assert_eq!("\\\\", b'\\'.escape_ascii().to_string());
assert_eq!("\\x9d", b'\x9d'.escape_ascii().to_string());

Returns the default value of 0

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

Converts a NonZeroU8 into an u8

Converts a bool to a u8. The resulting value is 0 for false and 1 for true values.

Examples

assert_eq!(u8::from(true), 1);
assert_eq!(u8::from(false), 0);

Converts an u8 into an AtomicU8.

Construct an ExitCode from an arbitrary u8 value.

Converts a u8 into a char.

Examples

use std::mem;

let u = 32 as u8;
let c = char::from(u);
assert!(4 == mem::size_of_val(&c))

Converts u8 to f32 losslessly.

Converts u8 to f64 losslessly.

Converts u8 to i128 losslessly.

Converts u8 to i16 losslessly.

Converts u8 to i32 losslessly.

Converts u8 to i64 losslessly.

Converts u8 to isize losslessly.

Converts u8 to u128 losslessly.

Converts u8 to u16 losslessly.

Converts u8 to u32 losslessly.

Converts u8 to u64 losslessly.

Converts u8 to usize losslessly.

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