My class lets call it A looked like this:

class A {
        A();
        size_t curl_write_data(void *buffer, size_t size, size_t nmemb, void
*userp);
};

then in implementing

size_t A::curl_write_data(void *buffer, size_t size, size_t nmemb, void
*userp) {
        // do some memory stuff here allot like the example from the curl
site
        return whateversize_t;
}

This cause it to blow up. BUT after doing what you suggested. I moved my
definition of curl_write_date out of my class and wrapped it with extern "C"
and then removed the A::curl_write_data to be curl_write_data, all was
happy. Only 6 hours wasted on this :) Thank goodness for mailing
lists!!!!!!!

Thanks so much.

-----Original Message-----
From: RBramante_at_on.com [mailto:RBramante_at_on.com]
Sent: Wednesday, September 18, 2002 4:23 PM
To: curl-library_at_lists.sourceforge.net
Subject: WriteMemoryCallback (was "(no subject)")

It looks like WriteMemoryCallback is a member function of a C++ class. How
is this defined? It needs to have C linkage for the callback to work.
Normally when you want to callback into C++ member function, a C helper
function makes life easier, e.g.

/* header file */
extern "C"
{
size_t curl_write_data(void *buffer, size_t size, size_t nmemb, void
*userp);
}

/* impl */
size_t curl_write_data(void *buffer, size_t size, size_t nmemb, void
*userp)
{
        MyClass* p = reinterpret_cast<MyClass*>(userp);
        return p->write_data(buffer, size, nmemb);
}

You pass the 'this' into the CURLOPT_WRITEFILE argument and then your
helper function redirects it to the proper object member function.

Just a thought anyway. This is how I've setup the callbacks with C++ code
in the past and they work fine.

I have a issue with trying to get a call back function to work. For some
reason when WriteMemoryCallback is called a "The memory could not be read"
error occurs.

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on Hammer Technology! Open Source & Linux Developers, register now
for the AMD Developer Symposium. Code: EX8664
http://www.developwithamd.com/developerlab
Received on 2002-09-18