static char char_flag;// 1111 ,figure ,lowercase ,uppercase,special charstd::string generateString(){    std::string result = "";    srand((unsigned)time(NULL));    char_flag = 0;    for(int i=0; i<8; i++){    char c =  rand()%(127-33)+33;        if(c >=48 &&c <= 57){            char_flag = char_flag|8;    }else if(c >= 65 && c <= 90){            char_flag = char_flag|2;    }else if(c >= 97 && c <= 122){            char_flag = char_flag|4;    }else{            char_flag = char_flag|1;        }        result += c;    }    if(char_flag == 0xf)        return result;    if(char_flag %2 == 0){        char c =  rand()%(127-33)+33;    while((c>=48&& c<= 57 )|| (c>=65&&c<=90)||(c>=97&&c<=122)){            c =  rand()%(127-33)+33;    }        result +=  c;        }    if((char_flag>>1 )%2 == 0){        char c =  rand()%(91-65)+65;        result += c;                }    if((char_flag>>2) %2 == 0){        char c =  rand()%(127-97)+97;        result +=  c;                    }    if((char_flag>>3 )%2 == 0){        char c =  rand()%(58-48)+48;        result += c;                    }    result+="\0";    SVP_INFO("------size = %d ----rand() = %s",result.size(),result.c_str());    return result;}