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/* @filename ipToNum.cpp @author caonan @date 2022-04-28 12:21:18 @reference 个人收集 @url @brief 将字符串类型的点分十进制IPv4转换为无符号整数 */ #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; /* 首先需要理解IP地址可以用4个字节表示，每个字节代表一段 需要注意IP地址每段最大为255，故需要用无符号整数表示 遍历一次即可完成，每段转换为10进制数字，一次点分左移8位或乘以255；最后一段也需要加上 如果有IP地址合法性检查加分 */ unsigned int ipToNum(string ip) { vector ip_arr; int pos = 0; while (true) { int pre = pos; pos = ip.find('.', pos); if (pos == std::string::npos) { ip_arr.push_back(std::stoi(ip.substr(pre))); break; } pos++; ip_arr.push_back(std::stoi(ip.substr(pre, pos - pre))); } string number; for (auto n : ip_arr) { bitset<8> b(n); // 主机序 number += b.to_string(); } bitset<32> ans(number); return ans.to_ullong(); } // 优化版本 unsigned int ipToNum2(string ip) { int num = 0; int left_offset = 3; unsigned int total_num = 0; ip += "."; for (int i = 0; i < ip.length(); i++) { if (ip[i] != '.') { int n = ip[i] - '0'; num = num * 10 + n; continue; } total_num = total_num == 0 ? num : total_num + num; total_num = left_offset-- > 0 ? total_num << 8 : total_num; num = 0; } return total_num; } uint32_t check(string ip) { struct in_addr addr; inet_pton(AF_INET, ip.c_str(), &addr.s_addr); return ntohl(addr.s_addr); } void uinttest() { char buf[15]; for (int r1 = 0; r1 <= 255; r1++) { for (int r2 = 0; r2 <= 255; r2++) { for (int r3 = 0; r3 <= 255; r3++) { for (int r4 = 0; r4 <= 255; r4++) { snprintf(buf, sizeof(buf), "%d.%d.%d.%d", r1, r2, r3, r4); string s(buf); // cout << s << endl; int ans1 = ipToNum2(s); int ans2 = check(s); assert(ans1 == ans2); } } } } } int main() { string ip = "192.168.1.1"; auto ret = ipToNum(ip); // 3232235777 cout << "iptonum: " << ret << endl; struct in_addr addr; inet_pton(AF_INET, ip.c_str(), &addr.s_addr); cout << "inet_pton: " << addr.s_addr << endl; uint32_t iaddr = ntohl(addr.s_addr); cout << "ntohl: " << iaddr << endl; uinttest(); // ipToNum2("192.168.1.1"); return 0; }