1 std::string GetRandomStr(int len) {
 2         //毫秒
 3         struct timeb time_seed;
 4         ftime(&time_seed);
 5         srand(time_seed.time * 1000 + time_seed.millitm);
 6 
 7         //秒
 8         //srand(time(0));
 9 
10         std::string random_str("");
11         for (int i = 0; i < len; ++i) {
12             switch (rand() % 3) {
13             case 1:
14                 random_str += ('A' + rand() % 26);
15                 break;
16             case 2:
17                 random_str += ('a' + rand() % 26);
18                 break;
19             default:
20                 random_str += ('0' + rand() % 10);
21                 break;
22             }
23         }
24 
25         return random_str;
26     }
27