如何在libcurl中使用成员函数指针 [英] How can I use a member function pointer in libcurl

问题描述

我使用libcurl我有我下载的文件里面的类，我想看到一个进度功能。我注意到我可以设置一个典型的函数指针

I am using libcurl I have my downloading of files inside of a class, to which I want to see a progress function. I notice I can set a typical function pointer by

curl_easy_setopt(mCurl, CURLOPT_PROGRESSFUNCTION, progress_func3);

但是，我想将它设置为指向我类的函数指针。我可以得到代码编译与

However, I would like to set it to a function pointer to my class. I can get the code to compile with

curl_easy_setopt(mCurl, CURLOPT_PROGRESSFUNCTION, &MyClass::progress_func3);

并且 progress_func3 函数将被调用。问题是，一旦返回就会有一个缓冲区溢出检测！错误通过，说程序不能安全地继续和执行，必须终止。 （这是一个Microsoft Visual C ++运行库错误窗口，我使用Visual Studio 2010）。

and the progress_func3 function will get called. The problem is, as soon as it returns there will be a "Buffer overrun detected!" error through, saying the program can not safely continue and execute, and must be terminated. (It is a Microsoft Visual C++ Runtime Library error window, I am using Visual Studio 2010).

当我使用一个函数，没有问题，但是当我使用一个成员函数指针，我会得到这个错误。如何在libcurl中使用成员函数指针？

When I use a function, there is no problem, but when I use a member function pointer, I will get this error. How can I use a member function pointer in libcurl?

推荐答案

非静态成员函数需要这个指针是可调用的。您无法使用此类型的接口提供此指针，因此无法使用非静态成员函数。

A non-static member function needs a this pointer to be callable. You can't provide that this pointer with this type of interface, so using a non-static member function is not possible.

您应该创建一个plain C函数作为回调函数，并在相应的 MyClass 实例上调用该函数的成员函数。

You should create a "plain C" function as your callback, and have that function call the member function on the appropriate MyClass instance.

尝试类似：

int my_progress_func(void *clientp, ...)
{
   MyClass *mc = static_cast<MyClass*>(clientp);
   mc->your_function(...);
   return 0; // or something else
}

然后：

curl_easy_setopt(mCurl, CURLOPT_PROGRESSDATA,     &your_myclass_object);
curl_easy_setopt(mCurl, CURLOPT_PROGRESSFUNCTION, my_progress_func);

（你必须负责这里的类型匹配， code> MyClass 指向进度数据的指针，你是自己的。）

(You're responsible for the type match here, obviously. If you attach anything else but a MyClass pointer to the progress data, you're on your own.)

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