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Code Issues Releases Wiki Activity

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 .\" * This software is licensed as described in the file COPYING, which
.\" * you should have received as part of this distribution. The terms .\" * 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, 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 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 \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 otherwise remove any others. The \fIcurl_multi_perform(3)\fP function should
called as soon as one of them is ready to be read from or written to. 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 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 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 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 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 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 long to wait? We suggest 100 milliseconds at least, but you may want to test
test it out in your own particular conditions to find a suitable value. 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 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 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 \fIlibcurl-errors(3)\fP
.SH "SEE ALSO" .SH "SEE ALSO"
.BR curl_multi_cleanup "(3), " curl_multi_init "(3), " .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) "