big endian and little endian

unsigned char test_bigendian( void ) 
{ 
    int test_var = 1; 
    unsigned char test_endian* = (unsigned char*)&test_var; 
 
    return (test_endian[0] == NULL); 
} 

int little_endian_to_big_endian(int i)
{
    return((i&0xff)<<24)+((i&0xff00)<<8)+((i&0xff0000)>>8)+((i>>24)&0xff);
}