Method which

CvPlot/ext/catch2/inc/catch.hpp:14728–14734

            enum Arch { Big, Little };

            static Arch which() {
                int one = 1;
                // If the lowest byte we read is non-zero, we can assume
                // that little endian format is used.
                auto value = *reinterpret_cast<char*>(&one);
                return value ? Little : Big;
            }
        };
    }