C语言如何拆分数值

typedef unsigned int u16;
typedef unsigned char u8;
struct hl
{u8 hbyte;
u8 lbyte;
};
union
{u16 x;
struct hl z;
}aa;

//放在函数体内
        aa.x=0x12fa;
assert(aa.z.hbyte==0x0012);
assert(aa.z.lbyte==0x00fa);