Here is what I do:
In the header function (set with CURLOPT_HEADERFUNCTION) I read the headers
until I get a blank header since a blank header indicates the end of the
headers. There is an exception to this however since you can get an HTTP
continue header followed by a blank header which is then followed by more
headers. Once I get a blank header that is NOT directly following the continue
I set a flag to indicatd I’m done reading headers. I also set that flag if the
write function (set with CURLOPT_WRITEFUNCTION) gets called as this also
indicates that the headers are complete. Once that flag is set, I call
curl_easy_getinfo to the response code.
No guarantees that this works with every server but it works with the servers
that my app uses.
Here is the relevant code:
bool IsContinueHeader(const CString& header)
{
return header.GetLength() > 12 && header.Left(5) == "HTTP/" &&
header.Right(12) == "100 Continue";
}
size_t headerCallback(char* data, size_t size, size_t nmemb,
CurlOperationState* state)
{
CString header = UTF8Convert::UTF8ToWide(std::string_view(data, size *
nmemb));
header.TrimRight(); // remove the trailing crlf
if (header.IsEmpty()) {
// An empty header signals end of headers, but not if it is after a
"HTTP/1.1 100 Continue" which comes before reading input data
if (!state->m_response_headers.empty()) {
const CString& last_header =
state->m_response_headers.at(state->m_response_headers.size() - 1);
if (!IsContinueHeader(last_header))
state->m_finished_reading_headers = true;
}
}
else {
state->m_response_headers.push_back(header);
}
return size * nmemb;
}
bool CurlHttpConnection::RunLoop()
{
int numfds;
CURLMcode mc = curl_multi_wait(m_multi_handle, NULL, 0, 1000, &numfds);
if (mc != CURLM_OK)
throw SyncException(L"Network error");
if (!numfds)
Sleep(100);
int still_running = 0;
curl_multi_perform(m_multi_handle, &still_running);
CheckForErrors();
return still_running > 0;
}
HttpResponse CurlHttpConnection::Request(const HttpRequest& request)
{
Cleanup();
m_state = std::make_unique<CurlOperationState>(request, m_listener);
SetupEasyHandle();
curl_multi_add_handle(m_multi_handle, m_state->m_easy_handle);
int still_running;
curl_multi_perform(m_multi_handle, &still_running);
while (!m_state->m_finished_reading_headers) {
RunLoop();
}
int http_status;
curl_easy_getinfo(m_state->m_easy_handle, CURLINFO_RESPONSE_CODE,
&http_status);
HttpResponse response(http_status, m_state->m_response_headers);
> On Feb 6, 2021, at 1:22 AM, Idan Freiberg via curl-library
> <curl-library@cool.haxx.se> wrote:
>
> Hi curl developers,
>
> I'm using the multi-stack interface in order to read a large response body in
> chunk, with the help of the CURLOPT_WRITEFUNCTION and some code similar to
> the one in fcurl project.
>
> I wonder if its possible to fetch info like response code, cookies, response
> headers before the running easy handle is done (which means all the response
> body was read).
>
> Technically reading the response headers should be possible as they are the
> first thing received. The thing is i'm not sure how to check they are fully
> received after a curl_multi_perform() call?
> Some times when using HTTP auth, you will receive the subsequent 401 response
> code instead of the actual response code returns after authentication.
>
> Any suggestions?
>
> Thanks
>
> --
> Idan Freiberg
> Mobile: +972-52-2925213
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