【C++】実行時にバイト・オーダを判定するコードのメモ。

cpp_byteorder_check_test.cpp

#include <iostream>
#include <cstdint>

/*
1. Assigns 1 to 16bit variable.
 int16_t x16 = 1;
     BE : 00000000 00000001
     LE : 00000001 00000000

2. Cast it to 8bit variable, then get upper 8bits.
 int8_t x8 = *reinterpret_cast<int8_t*>(&x16);
     BE : 00000000
     LE : 00000001

3. (^_^)b
    bool is_be = x8 == 0;
    bool is_le = x8 == 1;
//*/

bool isBigEndian()
{
    int16_t x = 1;
    return *reinterpret_cast<int8_t*>(&x) == 0;
}
bool isLittleEndian()
{
    return !isBigEndian();
}

int main()
{
    std::cout << std::boolalpha;
    std::cout << "isBigEndian   : " << isBigEndian()    << std::endl;
    std::cout << "isLittleEndin : " << isLittleEndian() << std::endl;
    return 0;
}