#include <curl/curl.h> CURLMcode curl_multi_perform(CURLM *multi_handle, int *running_handles);
|multi_handle||Pointer to a curl multi handle.|
|running_handles||Pointer to running handles.|
CURLMcode type, general libcurl multi interface error code.
Before version 7.20.0: If you receive
CURLM_CALL_MULTI_PERFORM, this indicates that you should call
curl_multi_perform again, before you select on more actions.
You do not have to perform this call immediately, but the return code indicates that libcurl may have more data available to return or that there may be more data to send off before it is "satisfied".
Do note that
curl_multi_perform will return
CURLM_CALL_MULTI_PERFORM only when it wants to be called again immediately. When things are fine and there is nothing immediate it wants
done, it will return
CURLM_OK and you need to wait for "action" and then call this function again.
This function only returns errors, etc., regarding the whole multi stack. Problems still might have occurred on individual transfers even when this function returns
When the app deems there is data available for the
multi_handle, it should call this function to read/write whatever there is to read or write at this time.
curl_multi_perform returns as soon as the reads/writes are done. This function does not require that there actually is any data available for reading or that data can be written, it can be called just in case. It will write the number of handles that still transfer data in the second argument's integer-pointer.
When you call
curl_multi_perform and the amount of running_handles is changed from the previous call (or is less than the amount of easy handles you have added to the multi-handle), you know that there is one or more transfers less "running". You can then call
curl_multi_info_read to get
information about each individual completed transfer, and that returned info includes
CURLcode and more.
If an added handle quickly fails, it may never be counted as a running_handle.
When running_handles is set to zero (0) on the return of this function, there is no longer any transfers in progress.
curl_multi_performallocates memory from the user stack during name resolution. Refer to
SOGetAddrInfofor the amount.
Most applications will use
curl_multi_fdset to get the multi_handle's file descriptors, then it will wait for action on them using select and as soon as one or more of them are ready,
curl_multi_perform gets called.
2014/04/07 Note about stack consumption.
2013/05/08 Automated cleanup pass.
2012/05/04 Initial version.