(myint + 3) & ~0x03

3的加法使得4的下一个倍数成为4的上一个倍数，这是通过模运算产生的，因为除数是2的幂，所以可以通过掩膜实现.

The addition of 3 is so that the next multiple of 4 becomes previous multiple of 4, which is produced by a modulo operation, doable by masking since the divisor is a power of 2.