std::endian

enum class endian
{
    little = /*implementation-defined*/,
    big    = /*implementation-defined*/,
    native = /*implementation-defined*/
};

Indicates the endianness of all scalar types:

• If all scalar types are little-endian, std::endian::native equals std::endian::little
• If all scalar types are big-endian, std::endian::native equals std::endian::big

Corner case platforms are also supported:

• If all scalar types have sizeof equal to 1, endianness does not matter and all three values, std::endian::little, std::endian::big, and std::endian::native are the same.
• If the platform uses mixed endian, std::endian::native equals neither std::endian::big nor std::endian::little.

Possible implementation

enum class endian
{
#ifdef _WIN32
    little = 0,
    big    = 1,
    native = little
#else
    little = __ORDER_LITTLE_ENDIAN__,
    big    = __ORDER_BIG_ENDIAN__,
    native = __BYTE_ORDER__
#endif
};

Notes

Feature testing macro: __cpp_lib_endian.

Example

#include <bit>
#include <iostream>
 
int main() {
 
    if constexpr (std::endian::native == std::endian::big)
        std::cout << "big-endian\n";
    else if constexpr (std::endian::native == std::endian::little)
        std::cout << "little-endian\n";
    else std::cout << "mixed-endian\n";
}

little-endian

See also