Hi,

I'm using libcurl to write C++ wrappers over https functionality.

I'm using CallBack functions to get the server response and headers in
memory. I have a function with the code snipet as shown below:

...
switch (request_type)
{
case HTTPS_POST:
   struct ServerResponse response;
   response.szResponse = NULL;
   response.size = 0;

   struct Header header;
   header.szHeader = NULL;
   header.size = 0;

    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_POST, TRUE);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_POSTFIELDS,
szPostFields);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle,
CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_FILE,
(void*)&response);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle,
CURLOPT_HEADERFUNCTION, WriteMemoryCallback);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_WRITEHEADER,
(void*)&header);
case HTTPS_GET: // Excuse the code duplication
    struct ServerResponse get_response;
    get_response.szResponse = NULL;
    get_response.size = 0;

    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_HTTPGET,
TRUE);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_UPLOAD,
FALSE);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle,
CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
    m_CurlReturnCode = curl_easy_setopt(m_pCurlHandle, CURLOPT_FILE,
(void*)&get_response);
case HTTPS_PUT:
...
}
m_CurlReturnCode = curl_easy_perform(m_pCurlHandle);
...

The call back function is as below:
size_t WriteMemoryCallback(void* ptr, size_t size, size_t nmemb, void* data)
{
     register int realsize = size * nmemb;
     struct ServerResponse* mem = (struct ServerResponse*)data;
     mem->szResponse = (char*)realloc(mem->szResponse, mem->size + realsize
+ 1);
     if (mem->szResponse)
     {
       memcpy(&(mem->szResponse[mem->size]), ptr, realsize);
       mem->size += realsize;
       mem->szResponse[mem->size] = 0;
     }
     return realsize;
}

From my client application, But when I call Post followed by Get, it crashes
in the callback as the data becomes invalid and mem->size shows garbage
value(3435973836) . So it fails in realloc. But If I call Get and then Put
it works fine. (sounds insane...just writing what is happening and hoping
for some clue).
However if I comment out the code for reading the headers, it works fine for
both sequence.

I'm not able to explain clearly ( I can see that), but I feel that I'm
missing something trivial here. Any inputs will be highly appreciated.

Thanks and Regards,
Naved

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Received on 2003-04-25