由数字转换到子网掩码

https://blog.csdn.net/u012258978/article/details/54022480

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// testconv.cpp : 定义控制台应用程序的入口点。 //   #include "stdafx.h" #include <cstring> #include <stdio.h> #include<stdlib.h> #include <iostream> #include <string> #define LMOVE(m,n) ((m)<<(n)) #define RMOVE(m,n) ((m)>>(n))   using namespace std; #ifdef WIN32 #define snprintf _snprintf #endif static std::string convert(int n) {     char buf[32] = {0};     unsigned int addr = LMOVE(0xffffffff,32 - n);     snprintf(buf, sizeof(buf), "%u.%u.%u.%u",         RMOVE(addr,24), RMOVE(addr,16)&0xff, RMOVE(addr,8)&0xff, addr&0xff);     return buf; } int _tmain(int argc, _TCHAR* argv[]) {     int pnum = 252;     string str11 = convert(pnum);     std::cout<<str11<<std::endl;     system("PAUSE");     return 0; }