判断大小端

int main()
{
        int i = 0x04030201;
        char *p = (char *)&i;

        if(*p == 1)
                printf("littel\n");
        else if(*p == 4)
                printf("big\n");
        else
                printf("???\n");

        int a[4] = {1, 2, 3, 4}; 
        char *pa = (char *)a;

        if(*pa == 1)
                printf("littel\n");
        else if(*pa == 4)
                printf("big\n");
        else
                printf("???\n");

/*
低地址  <-  0      +1     +2      +3  ->  高地址
littel:   a[0]    a[1]   a[2]    a[3]    
            1       2      3       4
big   :   a[4]    a[3]   a[2]    a[1]    
            4       3      2       1

littel:     1       2      3       4 
big   :     4       3      2       1
*/

}