std::bit_reverse - cppreference.com
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    std::bit_reverse

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    Defined in header <bit> 
    template< class T >
constexpr T bit_reverse( T x ) noexcept;
    		(since C++29)

    Returns x with the order of the bits reversed.

    Parameters

    x - a value whose bits to reverse
    Type requirements
    T - must be an unsigned integer type (that is, unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long, or an extended unsigned integer type) in order to participate in overload resolution.

    Return value

    x with the order of the bits reversed.

    Notes

    The function is typically implemented using an intrinsic such as Clang's __builtin_bitreverse, and has the same effect as the rbit instruction on ARM CPUs.

    Feature-test macro Value Std Feature
    __cpp_lib_bitops 202607L (C++29) Bit permutations

    Example

    Run this code
    #include <bit>
#include <cstdint>

static_assert(
    std::bit_reverse(
        std::uint8_t{0b1010'0011}) ==
        std::uint8_t{0b1100'0101} and
    std::bit_reverse(
        std::uint16_t{0b1010'0011}) ==
        std::uint16_t{0b1100'0101'0000'0000}
);

int main() {}

    See also