url编码函数

//摘自dansguardian 

std::string ConnectionHandler::miniURLEncode(std::string s)


{
    std::string encoded;
    char* buf = new char[16]; // way longer than needed

    unsigned char c;
    for(int i=0; i < (signed)s.length(); i++)


    {
        c = s[i];
        if ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') ||


             c == '.' || c == '-' || c == '_')


        {


            // allowed characters in a url that have non special meaning

            encoded += c;
            continue;
        }
        if(c == ' ')
        {
            encoded += '+';
            continue;
        }
        sprintf(buf, "%x", c);
        encoded += "%";
        encoded += buf;
    }
    delete[] buf;
    return encoded;
}