https://blog.faceutil.com/2017/03/28/%eb%8c%80%ec%9a%a9%eb%9f%89-%eb%b3%b5%ec%82%ac-%eb%b3%b5%ec%82%ac-%ec%9c%a0%ed%8b%b8-%eb%ac%b4%ec%84%a4%ec%b9%98-%eb%b3%b5%ec%82%ac%ed%94%84%eb%a1%9c%ea%b7%b8%eb%9e%a8-fastcopy-%e3%81%a2/