Primitive Type u64

1.0.0

Expand description

The 64-bit unsigned integer type.

Implementations§

Source §

let zero = 0u64;
assert_eq!(zero.count_zeros(), 64);

let max = u64::MAX;
assert_eq!(max.count_zeros(), 0);

This is heavily dependent on the width of the type, and thus might give surprising results depending on type inference:

let lucky = 7;
foo(lucky);
assert_eq!(lucky.count_zeros(), 5);
assert_eq!(lucky.count_ones(), 3);

let lucky = 7;
bar(lucky);
assert_eq!(lucky.count_zeros(), 13);
assert_eq!(lucky.count_ones(), 3);

You might want to use Self::count_ones instead, or emphasize the type you’re using in the call rather than method syntax:

let small = 1;
assert_eq!(u64::count_zeros(small), 63);

1.0.0 (const: 1.32.0) · Source

pub const fn leading_zeros(self) -> u32

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

let n = u64::MAX >> 2;
assert_eq!(n.leading_zeros(), 2);

let zero = 0u64;
assert_eq!(zero.leading_zeros(), 64);

let max = u64::MAX;
assert_eq!(max.leading_zeros(), 0);

1.0.0 (const: 1.32.0) · Source

pub const fn trailing_zeros(self) -> u32

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

§Examples

let n = 0b0101000u64;
assert_eq!(n.trailing_zeros(), 3);

let zero = 0u64;
assert_eq!(zero.trailing_zeros(), 64);

let max = u64::MAX;
assert_eq!(max.trailing_zeros(), 0);

1.46.0 (const: 1.46.0) · Source

pub const fn leading_ones(self) -> u32

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

§Examples

let n = !(u64::MAX >> 2);
assert_eq!(n.leading_ones(), 2);

let zero = 0u64;
assert_eq!(zero.leading_ones(), 0);

let max = u64::MAX;
assert_eq!(max.leading_ones(), 64);

1.0.0 (const: 1.32.0) · Source

pub const fn rotate_left(self, n: u32) -> Self

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

rotate_left(n) is equivalent to applying rotate_left(1) a total of n times. In particular, a rotation by the number of bits in self returns the input value unchanged.

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

§Examples

let n = 0xaa00000000006e1u64;
let m = 0x6e10aa;

assert_eq!(n.rotate_left(12), m);
assert_eq!(n.rotate_left(1024), n);

1.0.0 (const: 1.32.0) · Source

pub const fn rotate_right(self, n: u32) -> Self

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

rotate_right(n) is equivalent to applying rotate_right(1) a total of n times. In particular, a rotation by the number of bits in self returns the input value unchanged.

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

§Examples

let n = 0x6e10aau64;
let m = 0xaa00000000006e1;

assert_eq!(n.rotate_right(12), m);
assert_eq!(n.rotate_right(1024), n);

1.0.0 (const: 1.32.0) · Source

pub const fn swap_bytes(self) -> Self

Reverses the byte order of the integer.

§Examples

let n = 0x1234567890123456u64;
let m = n.swap_bytes();

assert_eq!(m, 0x5634129078563412);

1.37.0 (const: 1.37.0) · Source

pub const fn reverse_bits(self) -> Self

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

let n = 0x1234567890123456u64;
let m = n.reverse_bits();

assert_eq!(m, 0x6a2c48091e6a2c48);
assert_eq!(0, 0u64.reverse_bits());

1.0.0 (const: 1.32.0) · Source

pub const fn from_be(x: Self) -> Self

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

let n = 0x1Au64;

if cfg!(target_endian = "big") {
    assert_eq!(u64::from_be(n), n)
} else {
    assert_eq!(u64::from_be(n), n.swap_bytes())
}

1.0.0 (const: 1.32.0) · Source

pub const fn from_le(x: Self) -> Self

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

let n = 0x1Au64;

if cfg!(target_endian = "little") {
    assert_eq!(u64::from_le(n), n)
} else {
    assert_eq!(u64::from_le(n), n.swap_bytes())
}

1.0.0 (const: 1.32.0) · Source

pub const fn to_be(self) -> Self

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

let n = 0x1Au64;

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

1.0.0 (const: 1.32.0) · Source

pub const fn to_le(self) -> Self

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

let n = 0x1Au64;

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

1.0.0 (const: 1.47.0) · Source

pub const fn checked_add(self, rhs: Self) -> Option<Self>

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

§Examples

assert_eq!((u64::MAX - 2).checked_add(1), Some(u64::MAX - 1));
assert_eq!((u64::MAX - 2).checked_add(3), None);

1.79.0 (const: 1.79.0) · Source

pub const unsafe fn unchecked_add(self, rhs: Self) -> Self

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

Calling x.unchecked_add(y) is semantically equivalent to calling x.checked_add(y).unwrap_unchecked().

If you’re just trying to avoid the panic in debug mode, then do not use this. Instead, you’re looking for wrapping_add.

§Safety

This results in undefined behavior when self + rhs > u64::MAX or self + rhs < u64::MIN, i.e. when checked_add would return None.

1.0.0 (const: 1.47.0) · Source

pub const fn checked_sub(self, rhs: Self) -> Option<Self>

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

§Examples

assert_eq!(1u64.checked_sub(1), Some(0));
assert_eq!(0u64.checked_sub(1), None);

1.79.0 (const: 1.79.0) · Source

pub const unsafe fn unchecked_sub(self, rhs: Self) -> Self

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

Calling x.unchecked_sub(y) is semantically equivalent to calling x.checked_sub(y).unwrap_unchecked().

If you’re just trying to avoid the panic in debug mode, then do not use this. Instead, you’re looking for wrapping_sub.

If you find yourself writing code like this:

if foo >= bar {
    // SAFETY: just checked it will not overflow
    let diff = unsafe { foo.unchecked_sub(bar) };
    // ... use diff ...
}

Consider changing it to

if let Some(diff) = foo.checked_sub(bar) {
    // ... use diff ...
}

As that does exactly the same thing – including telling the optimizer that the subtraction cannot overflow – but avoids needing unsafe.

§Safety

This results in undefined behavior when self - rhs > u64::MAX or self - rhs < u64::MIN, i.e. when checked_sub would return None.

1.0.0 (const: 1.47.0) · Source

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

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

§Examples

assert_eq!(5u64.checked_mul(1), Some(5));
assert_eq!(u64::MAX.checked_mul(2), None);

1.67.0 (const: 1.67.0) · Source

pub const fn ilog(self, base: Self) -> u32

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!(5u64.ilog(5), 1);

1.67.0 (const: 1.67.0) · Source

pub const fn ilog2(self) -> u32

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

§Panics

This function will panic if self is zero.

§Examples

assert_eq!(2u64.ilog2(), 1);

1.67.0 (const: 1.67.0) · Source

pub const fn ilog10(self) -> u32

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

§Panics

This function will panic if self is zero.

§Example

assert_eq!(10u64.ilog10(), 1);

1.67.0 (const: 1.67.0) · Source

pub const fn checked_ilog(self, base: Self) -> Option<u32>

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!(5u64.checked_ilog(5), Some(1));

1.67.0 (const: 1.67.0) · Source

pub const fn checked_ilog2(self) -> Option<u32>

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

Returns None if the number is zero.

§Examples

assert_eq!(2u64.checked_ilog2(), Some(1));

1.67.0 (const: 1.67.0) · Source

pub const fn checked_ilog10(self) -> Option<u32>

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

Returns None if the number is zero.

§Examples

assert_eq!(10u64.checked_ilog10(), Some(1));

1.93.0 (const: 1.93.0) · Source

pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self

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.

1.93.0 (const: 1.93.0) · Source

pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self

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.

1.34.0 (const: 1.50.0) · Source

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

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

§Examples

assert_eq!(2u64.checked_pow(5), Some(32));
assert_eq!(0_u64.checked_pow(0), Some(1));
assert_eq!(u64::MAX.checked_pow(2), None);

1.0.0 (const: 1.47.0) · Source

pub const fn saturating_add(self, rhs: Self) -> Self

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

§Examples

assert_eq!(100u64.saturating_add(1), 101);
assert_eq!(u64::MAX.saturating_add(127), u64::MAX);

1.0.0 (const: 1.47.0) · Source

pub const fn saturating_sub(self, rhs: Self) -> Self

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

§Examples

assert_eq!(100u64.saturating_sub(27), 73);
assert_eq!(13u64.saturating_sub(127), 0);

1.7.0 (const: 1.47.0) · Source

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

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

§Examples

assert_eq!(2u64.saturating_mul(10), 20);
assert_eq!((u64::MAX).saturating_mul(10), u64::MAX);

1.0.0 (const: 1.32.0) · Source

pub const fn wrapping_add(self, rhs: Self) -> Self

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

§Examples

assert_eq!(200u64.wrapping_add(55), 255);
assert_eq!(200u64.wrapping_add(u64::MAX), 199);

1.66.0 (const: 1.66.0) · Source

pub const fn wrapping_add_signed(self, rhs: i64) -> Self

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

§Examples

assert_eq!(1u64.wrapping_add_signed(2), 3);
assert_eq!(1u64.wrapping_add_signed(-2), u64::MAX);
assert_eq!((u64::MAX - 2).wrapping_add_signed(4), 1);

1.0.0 (const: 1.32.0) · Source

pub const fn wrapping_sub(self, rhs: Self) -> Self

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

§Examples

assert_eq!(100u64.wrapping_sub(100), 0);
assert_eq!(100u64.wrapping_sub(u64::MAX), 101);

1.0.0 (const: 1.32.0) · Source

pub const fn wrapping_mul(self, rhs: Self) -> Self

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

§Examples

Please note that this example is shared among integer types, which is why u8 is used.

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

1.2.0 (const: 1.32.0) · Source

pub const fn wrapping_neg(self) -> Self

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

assert_eq!(0_u64.wrapping_neg(), 0);
assert_eq!(u64::MAX.wrapping_neg(), 1);
assert_eq!(13_u64.wrapping_neg(), (!13) + 1);
assert_eq!(42_u64.wrapping_neg(), !(42 - 1));

1.2.0 (const: 1.32.0) · Source

pub const fn wrapping_shl(self, rhs: u32) -> Self

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.

Beware that, unlike most other wrapping_* methods on integers, this does not give the same result as doing the shift in infinite precision then truncating as needed. The behaviour matches what shift instructions do on many processors, and is what the << operator does when overflow checks are disabled, but numerically it’s weird. Consider, instead, using [Self::unbounded_shl] which has nicer behaviour.

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

assert_eq!(1_u64.wrapping_shl(7), 128);
assert_eq!(0b101_u64.wrapping_shl(0), 0b101);
assert_eq!(0b101_u64.wrapping_shl(1), 0b1010);
assert_eq!(0b101_u64.wrapping_shl(2), 0b10100);
assert_eq!(u64::MAX.wrapping_shl(2), u64::MAX - 3);
assert_eq!(42_u64.wrapping_shl(64), 42);
assert_eq!(42_u64.wrapping_shl(1).wrapping_shl(63), 0);
assert_eq!(1_u64.wrapping_shl(128), 1);
assert_eq!(5_u64.wrapping_shl(1025), 10);

1.2.0 (const: 1.32.0) · Source

pub const fn wrapping_shr(self, rhs: u32) -> Self

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.

Beware that, unlike most other wrapping_* methods on integers, this does not give the same result as doing the shift in infinite precision then truncating as needed. The behaviour matches what shift instructions do on many processors, and is what the >> operator does when overflow checks are disabled, but numerically it’s weird. Consider, instead, using [Self::unbounded_shr] which has nicer behaviour.

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

assert_eq!(128_u64.wrapping_shr(7), 1);
assert_eq!(0b1010_u64.wrapping_shr(0), 0b1010);
assert_eq!(0b1010_u64.wrapping_shr(1), 0b101);
assert_eq!(0b1010_u64.wrapping_shr(2), 0b10);
assert_eq!(u64::MAX.wrapping_shr(1), i64::MAX.cast_unsigned());
assert_eq!(42_u64.wrapping_shr(64), 42);
assert_eq!(42_u64.wrapping_shr(1).wrapping_shr(63), 0);
assert_eq!(128_u64.wrapping_shr(128), 128);
assert_eq!(10_u64.wrapping_shr(1025), 5);

1.7.0 (const: 1.32.0) · Source

pub const fn overflowing_add(self, rhs: Self) -> (Self, bool)

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

assert_eq!(5u64.overflowing_add(2), (7, false));
assert_eq!(u64::MAX.overflowing_add(1), (0, true));

1.91.0 (const: unstable) · Source

pub fn carrying_add(self, rhs: Self, carry: bool) -> (Self, bool)

Calculates self + rhs + carry and returns a tuple containing the sum and the output carry (in that order).

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 64-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

//    3  MAX    (a = 3 × 2^64 + 2^64 - 1)
// +  5    7    (b = 5 × 2^64 + 7)
// ---------
//    9    6    (sum = 9 × 2^64 + 6)

let (a1, a0): (u64, u64) = (3, u64::MAX);
let (b1, b0): (u64, u64) = (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));

1.66.0 (const: 1.66.0) · Source

pub const fn overflowing_add_signed(self, rhs: i64) -> (Self, bool)

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

assert_eq!(1u64.overflowing_add_signed(2), (3, false));
assert_eq!(1u64.overflowing_add_signed(-2), (u64::MAX, true));
assert_eq!((u64::MAX - 2).overflowing_add_signed(4), (1, true));

1.7.0 (const: 1.32.0) · Source

pub const fn overflowing_sub(self, rhs: Self) -> (Self, bool)

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

assert_eq!(5u64.overflowing_sub(2), (3, false));
assert_eq!(0u64.overflowing_sub(1), (u64::MAX, true));

1.60.0 (const: 1.60.0) · Source

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

Computes the absolute difference between self and other.

§Examples

assert_eq!(100u64.abs_diff(80), 20u64);
assert_eq!(100u64.abs_diff(110), 10u64);

1.7.0 (const: 1.32.0) · Source

pub const fn overflowing_mul(self, rhs: Self) -> (Self, bool)

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.

If you want the value of the overflow, rather than just whether an overflow occurred, see Self::carrying_mul.

§Examples

Please note that this example is shared among integer types, which is why u32 is used.

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

Source

pub const fn widening_mul(self, rhs: Self) -> (Self, Self)

🔬This is a nightly-only experimental API. (bigint_helper_methods #85532)

Calculates the complete double-width product self * rhs.

This returns the low-order (wrapping) bits and the high-order (overflow) bits of the result as two separate values, in that order. As such, a.widening_mul(b).0 produces the same result as a.wrapping_mul(b).

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

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

If you just want to know whether the multiplication overflowed, then you want Self::overflowing_mul instead.

§Examples

#![feature(bigint_helper_methods)]
assert_eq!(5_u64.widening_mul(7), (35, 0));
assert_eq!(u64::MAX.widening_mul(u64::MAX), (1, u64::MAX - 1));

Compared to other *_mul methods:

#![feature(bigint_helper_methods)]
assert_eq!(u64::widening_mul(1 << 63, 6), (0, 3));
assert_eq!(u64::overflowing_mul(1 << 63, 6), (0, true));
assert_eq!(u64::wrapping_mul(1 << 63, 6), 0);
assert_eq!(u64::checked_mul(1 << 63, 6), None);

Please note that this example is shared among integer types, which is why u32 is used.

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

1.91.0 (const: unstable) · Source

pub fn carrying_mul(self, rhs: Self, carry: Self) -> (Self, Self)

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 also need to add a value, then use Self::carrying_mul_add.

§Examples

Please note that this example is shared among integer types, which is why u32 is used.

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!(u64::MAX.carrying_mul(u64::MAX, u64::MAX), (0, u64::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),
);

1.91.0 (const: unstable) · Source

pub fn carrying_mul_add(self, rhs: Self, carry: Self, add: Self) -> (Self, Self)

Calculates the “full multiplication” self * rhs + carry + add.

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

This cannot overflow, as the double-width result has exactly enough space for the largest possible result. This is equivalent to how, in decimal, 9 × 9 + 9 + 9 = 81 + 18 = 99 = 9×10⁰ + 9×10¹ = 10² - 1.

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 add part, then you can use Self::carrying_mul instead.

§Examples

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

assert_eq!(5u32.carrying_mul_add(2, 0, 0), (10, 0));
assert_eq!(5u32.carrying_mul_add(2, 10, 10), (30, 0));
assert_eq!(1_000_000_000u32.carrying_mul_add(10, 0, 0), (1410065408, 2));
assert_eq!(1_000_000_000u32.carrying_mul_add(10, 10, 10), (1410065428, 2));
assert_eq!(u64::MAX.carrying_mul_add(u64::MAX, u64::MAX, u64::MAX), (u64::MAX, u64::MAX));

This is the core per-digit operation for “grade school” O(n²) multiplication.

Please note that this example is shared between integer types, using u8 for simplicity of the demonstration.

fn quadratic_mul<const N: usize>(a: [u8; N], b: [u8; N]) -> [u8; N] {
    let mut out = [0; N];
    for j in 0..N {
        let mut carry = 0;
        for i in 0..(N - j) {
            (out[j + i], carry) = u8::carrying_mul_add(a[i], b[j], out[j + i], carry);
        }
    }
    out
}

// -1 * -1 == 1
assert_eq!(quadratic_mul([0xFF; 3], [0xFF; 3]), [1, 0, 0]);

assert_eq!(u32::wrapping_mul(0x9e3779b9, 0x7f4a7c15), 0xcffc982d);
assert_eq!(
    quadratic_mul(u32::to_le_bytes(0x9e3779b9), u32::to_le_bytes(0x7f4a7c15)),
    u32::to_le_bytes(0xcffc982d)
);

1.0.0 (const: 1.50.0) · Source

pub const fn pow(self, exp: u32) -> Self

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

§Examples

assert_eq!(2u64.pow(5), 32);
assert_eq!(0_u64.pow(0), 1);

1.73.0 (const: 1.73.0) · Source

pub const fn div_ceil(self, rhs: Self) -> Self

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

§Panics

This function will panic if rhs is zero.

§Examples

assert_eq!(7_u64.div_ceil(4), 2);

1.87.0 (const: 1.87.0) · Source

pub const fn is_multiple_of(self, rhs: Self) -> bool

Returns true if self is an integer multiple of rhs, and false otherwise.

This function is equivalent to self % rhs == 0, except that it will not panic for rhs == 0. Instead, 0.is_multiple_of(0) == true, and for any non-zero n, n.is_multiple_of(0) == false.

§Examples

assert!(6_u64.is_multiple_of(2));
assert!(!5_u64.is_multiple_of(2));

assert!(0_u64.is_multiple_of(0));
assert!(!6_u64.is_multiple_of(0));

1.0.0 (const: 1.32.0) · Source

pub const fn is_power_of_two(self) -> bool

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

§Examples

assert!(16u64.is_power_of_two());
assert!(!10u64.is_power_of_two());

1.32.0 (const: 1.44.0) · Source

pub const fn to_be_bytes(self) -> [u8; 8]

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

§Examples

let bytes = 0x1234567890123456u64.to_be_bytes();
assert_eq!(bytes, [0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56]);

1.32.0 (const: 1.44.0) · Source

pub const fn to_le_bytes(self) -> [u8; 8]

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

§Examples

let bytes = 0x1234567890123456u64.to_le_bytes();
assert_eq!(bytes, [0x56, 0x34, 0x12, 0x90, 0x78, 0x56, 0x34, 0x12]);

1.32.0 (const: 1.44.0) · Source

pub const fn to_ne_bytes(self) -> [u8; 8]

Returns 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 = 0x1234567890123456u64.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]
    }
);

1.32.0 (const: 1.44.0) · Source

pub const fn from_be_bytes(bytes: [u8; 8]) -> Self

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

§Examples

let value = u64::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:

fn read_be_u64(input: &mut &[u8]) -> u64 {
    let (int_bytes, rest) = input.split_at(size_of::<u64>());
    *input = rest;
    u64::from_be_bytes(int_bytes.try_into().unwrap())
}

1.32.0 (const: 1.44.0) · Source

pub const fn from_le_bytes(bytes: [u8; 8]) -> Self

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

§Examples

let value = u64::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:

fn read_le_u64(input: &mut &[u8]) -> u64 {
    let (int_bytes, rest) = input.split_at(size_of::<u64>());
    *input = rest;
    u64::from_le_bytes(int_bytes.try_into().unwrap())
}

1.32.0 (const: 1.44.0) · Source

pub const fn from_ne_bytes(bytes: [u8; 8]) -> Self

Creates 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 = u64::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:

fn read_ne_u64(input: &mut &[u8]) -> u64 {
    let (int_bytes, rest) = input.split_at(size_of::<u64>());
    *input = rest;
    u64::from_ne_bytes(int_bytes.try_into().unwrap())
}

Source §

impl u64

1.0.0 (const: 1.82.0) · Source

pub const fn from_str_radix(src: &str, radix: u32) -> Result<u64, ParseIntError>

Parses an integer from a string slice with digits in a given base.

The string is expected to be an optional + sign followed by only digits. Leading and trailing non-digit characters (including whitespace) represent an error. Underscores (which are accepted in Rust literals) also 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.

§See also

If the string to be parsed is in base 10 (decimal), from_str or str::parse can also be used.

§Examples

assert_eq!(u64::from_str_radix("A", 16), Ok(10));

Trailing space returns error:

assert!(u64::from_str_radix("1 ", 10).is_err());

Source

pub const fn from_ascii_radix( src: &[u8], radix: u32, ) -> Result<u64, ParseIntError>

🔬This is a nightly-only experimental API. (int_from_ascii #134821)

Parses an integer from an ASCII-byte slice with digits in a given base.

The characters are expected to be an optional + sign followed by only digits. Leading and trailing non-digit characters (including whitespace) represent an error. Underscores (which are accepted in Rust literals) also 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

#![feature(int_from_ascii)]

assert_eq!(u64::from_ascii_radix(b"A", 16), Ok(10));

Trailing space returns error:

assert!(u64::from_ascii_radix(b"1 ", 10).is_err());

Source §

impl u64

Source

pub fn format_into(self, buf: &mut NumBuffer<Self>) -> &str

🔬This is a nightly-only experimental API. (int_format_into #138215)

Available on WebAssembly only.

Allows users to write an integer (in signed decimal format) into a variable buf of type NumBuffer that is passed by the caller by mutable reference.

§Examples

#![feature(int_format_into)]
use core::fmt::NumBuffer;

let n = 0u64;
let mut buf = NumBuffer::new();
assert_eq!(n.format_into(&mut buf), "0");

let n1 = 32u64;
assert_eq!(n1.format_into(&mut buf), "32");

let n2 = u64 :: MAX;
assert_eq!(n2.format_into(&mut buf), u64 :: MAX.to_string());

🔬This is a nightly-only experimental API. (core_intrinsics_fallbacks)

1.0.0 (const: unstable) · Source§

impl Clone for u64

Source §

fn clone(&self) -> Self

Returns a duplicate of the value. Read more

fn div(self, other: NonZero<u64>) -> u64

Source §

fn from(small: bool) -> Self

Converts a bool to u64 losslessly. The resulting value is 0 for false and 1 for true values.

§Examples

assert_eq!(u64::from(true), 1);
assert_eq!(u64::from(false), 0);

fn hash_slice<H: Hasher>(data: &[u64], state: &mut H)

Feeds a slice of this type into the given Hasher. Read more

1.42.0 · Source§

impl LowerExp for u64

Available on WebAssembly only.

Performs the unary ! operation. Read more

1.0.0 (const: unstable) · Source§

impl Not for u64

Source §

type Output = u64

The resulting type after applying the ! operator.

Source §

fn not(self) -> u64

Performs the unary ! operation. Read more

impl Ord for u64

Source §

fn cmp(&self, other: &Self) -> Ordering

This method returns an Ordering between self and other. Read more

1.21.0 · Source§

fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more

1.21.0 · Source§

fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more

1.50.0 · Source§

fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized,

Restrict a value to a certain interval. Read more

1.0.0 (const: unstable) · Source§

impl PartialEq for u64

Source §

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

Source §

fn ne(&self, other: &Self) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

1.0.0 (const: unstable) · Source§

Tries to create the target number type from a source number type. This returns an error if the source value is outside of the range of the target type.

Source §

type Error = TryFromIntError

The type returned in the event of a conversion error.

1.42.0 · Source§

impl UpperExp for u64

Available on WebAssembly only.

Source §

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

1.0.0 · Source§

impl UpperHex for u64

Source §

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Format unsigned integers in the radix.

Source §

impl ConstParamTy_ for u64

1.0.0 · Source§

impl Copy for u64

1.0.0 (const: unstable) · Source§

impl Eq for u64

Source §

impl StructuralPartialEq for u64

fn try_from(value: U) -> Result<T, <T as TryFrom>::Error>

Performs the conversion.

Source §

impl<T, U> TryInto for T
where U: TryFrom<T>,

Source §

type Error = >::Error

The type returned in the event of a conversion error.

Source §

fn try_into(self) -> Result<U, >::Error>

Performs the conversion.

Primitive Type u64 Copy item path

Implementations§

impl u64

pub const MIN: Self = 0

§Examples

pub const MAX: Self

§Examples

pub const BITS: u32

§Examples

pub const fn count_ones(self) -> u32

§Examples

pub const fn count_zeros(self) -> u32

§Examples

pub const fn leading_zeros(self) -> u32

§Examples

pub const fn trailing_zeros(self) -> u32

§Examples

pub const fn leading_ones(self) -> u32

§Examples

pub const fn rotate_left(self, n: u32) -> Self

§Examples

pub const fn rotate_right(self, n: u32) -> Self

§Examples

pub const fn swap_bytes(self) -> Self

§Examples

pub const fn reverse_bits(self) -> Self

§Examples

pub const fn from_be(x: Self) -> Self

§Examples

pub const fn from_le(x: Self) -> Self

§Examples

pub const fn to_be(self) -> Self

§Examples

pub const fn to_le(self) -> Self

§Examples

pub const fn checked_add(self, rhs: Self) -> Option<Self>

§Examples

pub const unsafe fn unchecked_add(self, rhs: Self) -> Self

§Safety

pub const fn checked_sub(self, rhs: Self) -> Option<Self>

§Examples

pub const unsafe fn unchecked_sub(self, rhs: Self) -> Self

§Safety

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

§Examples

pub const fn ilog(self, base: Self) -> u32

§Panics

§Examples

pub const fn ilog2(self) -> u32

§Panics

§Examples

pub const fn ilog10(self) -> u32

§Panics

§Example

pub const fn checked_ilog(self, base: Self) -> Option<u32>

§Examples

pub const fn checked_ilog2(self) -> Option<u32>

§Examples

pub const fn checked_ilog10(self) -> Option<u32>

§Examples

pub const unsafe fn unchecked_shl(self, rhs: u32) -> Self

§Safety

pub const unsafe fn unchecked_shr(self, rhs: u32) -> Self

§Safety

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

§Examples

pub const fn saturating_add(self, rhs: Self) -> Self

§Examples

pub const fn saturating_sub(self, rhs: Self) -> Self

§Examples

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

§Examples

pub const fn wrapping_add(self, rhs: Self) -> Self

§Examples

pub const fn wrapping_add_signed(self, rhs: i64) -> Self

§Examples

pub const fn wrapping_sub(self, rhs: Self) -> Self

§Examples

pub const fn wrapping_mul(self, rhs: Self) -> Self

§Examples

Primitive Type u64