int to char casting

Question

int i = 259;       /* 03010000 in Little Endian ; 00000103 in Big Endian */
char c = (char)i;  /* returns 03 in both Little and Big Endian?? */

In

Answer 1

If you want to test for little/big endian, you can use a union:

int isBigEndian (void)
{
    union foo {
        size_t i;
        char cp[sizeof(size_t)];
    } u;

    u.i = 1;
    return *u.cp != 1;
}

It works because in little endian, it would look like 01 00 ... 00, but in big endian, it would be 00 ... 00 01 (the ... is made up of zeros). So if the first byte is 0, the test returns true. Otherwise it returns false. Beware, however, that there also exist mixed endian machines that store data differently (some can switch endianness; others just store the data differently). The PDP-11 stored a 32-bit int as two 16-bit words, except the order of the words was reversed (e.g. 0x01234567 was 4567 0123).