c/c++判断ipv4地址

 1 bool is_ipv4_str(const char* ipv4)  2 {  3     if (!ipv4 || !ipv4[0]) {  4         return false;  5     }  6   7     size_t len = strlen(ipv4);  8     if (len < MIN_IPV4_LEN || len > MAX_IPV4_LEN) {  9         return false; 10     } 11  12     int num[4] = {0}; 13     char c = 0; 14  15     if (sscanf(ipv4, "%d.%d.%d.%d%c", num, num+1, num+2, num+3, &c) != 4) { 16         return false; 17     } 18  19     int i = 0; 20     for (; i < 4; i++) { 21         if (num[i] < 0 || num[i] > 255) { 22             return false; 23         } 24     } 25  26     return true; 27 }