From what I understand (and I very well might be mistaken ;-) ) the
write and read function callbacks should function in the manner similar
to stdio's fwrite and fread functions... that means returning 0 is not
enough , you also need to set the error to end-of-file (even though you
are not actually working with files). I need to check my old code, I
made something like that once or twice... AGAIN , I MIGHT BE MISTAKEN :)
if so , I am sorry ;)

Venkatesh Prabu Narayanan wrote:
> Hi,
>
> I have some issues in using call back function which I would like to
> share with you and get some ideas.
>
> First let me explain the scenario,
>
> From client side, I need to upload GBs of data (char buffer, not a
> actual file, since I have to do some operations like compression on
> the fly) to server. In the client side, I am using libcurl (version
> 7.19.3) to upload data (not file) using call back function to remote
> server where in the data was received from the socket and write into
> the file. Since I don't know the actual size to be uploaded earlier, I
> couldn't set the exact CURLOPT_INFILESIZE_LARGE. If I didn't set the
> above option, my call back wasn't getting called and so I set this
> option to some large value say 50GB using the curl_easy_setopt call.
> In the server side, a socket program is running which is continuously
> streaming the data from the socket in which we sent data from the
> libcurl in the client side.
>
> The problem I faced here is, after sending the final block of data, I
> return 0 to the call back function. But still curl_easy_perform()
> doesn't return instead it is still hanging in this function and leaves
> the socket connection open,
>
> select() call in the function Curl_socket_ready().
>
> While debugging the application, in server side, the application seems
> to be wait in the 'SSL_Read()' function.
>
> My understanding is that whenever I return zero in the call back
> function, it should come out of call back function and in turn the
> curl_easy_perform(). But that is not happening in my case. Is there
> any way to close the current libcurl call after sending all the data ?
>
> My sample code (slightly modified):
>
> double contLength = 50GB; //Just added GB here for easy reference.
> curl_easy_setopt(curlPtr, CURLOPT_READFUNCTION, ReadData);
> curl_easy_setopt(curlPtr, CURLOPT_READDATA, userpointer);
> curl_easy_setopt(curlPtr, CURLOPT_UPLOAD, 1L);
> curl_easy_setopt(curlPtr, CURLOPT_PUT, 1L);
> curl_easy_setopt(curlPtr, CURLOPT_WRITEFUNCTION, WriteResponseData);
> curl_easy_setopt(curlPtr, CURLOPT_WRITEDATA, userpointer);
> //curl_easy_setopt(curlPtr, CURLOPT_IGNORE_CONTENT_LENGTH, 1);
> curl_easy_setopt(curlPtr, CURLOPT_INFILESIZE_LARGE,
> (curl_off_t)contLength);
>
> size_t ReadData(void *ptr, size_t size, size_t nmemb, void* userp)
> {
> MyClass* myObj = (MyClass*)userp;
> size_t bufSize = size * nmemb;
> size_t toRet = myObj->ReadDataFromMemory((
> char*)ptr, bufSize);
> return toRet;
> };
>
> size_t WriteResponseData(void *ptr, size_t size, size_t nmemb, void*
> userp)
> {
> MyClass* myObj = (MyClass*)userp;
> size_t bufSize = size * nmemb;
> size_t toRet = myObj->WriteDataToMemory((char*)ptr, bufSize);
> return toRet;
> };
>
> Please correct me if I am doing anything wrong here.
>
> Regards,
> Venkatesh
>
>
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Received on 2013-05-24