c++ - curl WRITEFUNCTION 和类

Question

class Filter{
private:
    string contents;
    bool Server(void);
public:
    void handle(void *, size_t, size_t, void *);
   };

我有一个这样的类标题。我想在函数服务器内调用 curl WRITEFUNCTION，它将使用句柄写入字符串内容。虽然它一直给我错误

error: invalid use of member (did you forget the ‘&’ ?)

错误指向的行是 CURLOPT_WRITEFUNCTION....我的 curl 请求看起来像这样...

curl_easy_setopt(curl,CURLOPT_URL, address.c_str());
curl_easy_setopt(curl,CURLOPT_WRITEFUNCTION,handle);
curl_easy_perform(curl);

这意味着它无法访问 handle()..我该如何纠正这个问题？

Answer 1

句柄必须是静态成员函数。您可以使用 CURLOPT_WRITEDATA 将指向 Filter 实例的指针作为最后一个参数传递

class Filter
{ 
private:
    std::string content_;
    static size_t handle(char * data, size_t size, size_t nmemb, void * p);
    size_t handle_impl(char * data, size_t size, size_t nmemb);
};

size_t Filter::handle(char * data, size_t size, size_t nmemb, void * p)
{
    return static_cast<Filter*>(p)->handle_impl(data, size, nmemb);
}

size_t Filter::handle_impl(char* data, size_t size, size_t nmemb)
{
    content_.append(data, size * nmemb);
    return size * nmemb;
}

int main()
{
   // curl initialization... should be done in a constructor
   Filter f;
   curl_easy_setopt(curl, CURLOPT_WRITEDATA, &f);
   curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, &Filter::handle);
   // curl cleanup... should be done in a destructor
   return 0;
}