# std::endian

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< cpp‎ | types

Defined in header `<bit>` |  |
enum class endian { little = /*implementation-defined*/, big = /*implementation-defined*/, native = /*implementation-defined*/, }; |  | (since C++20)

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
    {
    #if defined(_MSC_VER) && !defined(__clang__)
        little = 0,
        big    = 1,
        native = little
    #else
        little = __ORDER_LITTLE_ENDIAN__,
        big    = __ORDER_BIG_ENDIAN__,
        native = __BYTE_ORDER__
    #endif
    };

### Notes

Feature-test macro | Value | Std | Comment
--- | --- | --- | ---
`__cpp_lib_endian` | 201907L | (C++20) | std::endian

### Example

Run this code

    #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";
    }

Possible output:

    mixed-endian

### See also

byteswap (C++23) | reverses the bytes in the given integer value (function template)

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