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curl_multi_fdset: explain the fd_set arguments

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Daniel Stenberg 2014-10-09 13:17:27 +02:00
parent 9e37a7f9a5
commit 93b268ade0
1 changed files with 18 additions and 6 deletions
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24
docs/libcurl/curl_multi_fdset.3
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@ -5,7 +5,7 @@
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" *
.\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms
@ -37,8 +37,20 @@ This function extracts file descriptor information from a given multi_handle.
libcurl returns its fd_set sets. The application can use these to select() on,
but be sure to FD_ZERO them before calling this function as
\fIcurl_multi_fdset(3)\fP only adds its own descriptors, it doesn't zero or
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.
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.
If the \fIread_fd_set\fP argument is not a null pointer, it points to an
object of type fd_set that on returns specifies the file descriptors to be
checked for being ready to read.
If the \fIwrite_fd_set\fP argument is not a null pointer, it points to an
object of type fd_set that on return specifies the file descriptors to be
checked for being ready to write.
If the \fIexc_fd_set\fP argument is not a null pointer, it points to an object
of type fd_set that on return specifies the file descriptors to be checked for
error conditions pending.
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
@ -47,8 +59,8 @@ 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.
long to wait? We 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
@ -67,4 +79,4 @@ CURLMcode type, general libcurl multi interface error code. See
\fIlibcurl-errors(3)\fP
.SH "SEE ALSO"
.BR curl_multi_cleanup "(3), " curl_multi_init "(3), "
.BR curl_multi_timeout "(3), " curl_multi_perform "(3) "
.BR curl_multi_timeout "(3), " curl_multi_perform "(3), " select "(2) "