Commit 337252bd authored by Daniel Stenberg's avatar Daniel Stenberg
Browse files

curl_multi_fdset: clarify the max_fd == -1 case 

Elaborate what max_fd == -1 means

Remove the reference to CURLM_CALL_MULTI_PERFORM as modern libcurl
versions don't ever return that.
parent 840eff44

docs/libcurl/curl_multi_fdset.3

+7 −6
Original line number Diff line number Diff line
@@ -40,14 +40,15 @@ but be sure to FD_ZERO them before calling this function as 
otherwise remove any others. The \fIcurl_multi_perform(3)\fP function should be

called as soon as one of them is ready to be read from or written to.



To be sure to have up-to-date results, you should call

\fIcurl_multi_perform\fP until it does not return CURLM_CALL_MULTI_PERFORM

prior to calling \fIcurl_multi_fdset\fP.  This will make sure that libcurl has

updated the handles' socket states.



If no file descriptors are set by libcurl, \fImax_fd\fP will contain -1 when

this function returns. Otherwise it will contain the higher descriptor number

libcurl set.

libcurl set. When libcurl returns -1 in \fImax_fd\fP, it is because libcurl

currently does something that isn't possible for your application to monitor

with a socket and unfortunately you can then not know exactly when the current

action is completed using select(). When max_fd returns with -1, you need to

wait a while and then proceed and call \fIcurl_multi_perform\fP anyway. How

long to wait? I would suggest 100 milliseconds at least, but you may want to

test it out in your own particular conditions to find a suitable value.



When doing select(), you should use \fBcurl_multi_timeout\fP to figure out how

long to wait for action. Call \fIcurl_multi_perform\fP even if no activity has