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libcurl-multi.3: mention curl_multi_wait

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... and some general rewordings to improve this docs.

Reported-by: Tim Stack

Closes #356
This commit is contained in:
Daniel Stenberg 2015-07-30 10:17:37 +02:00
parent bdd8cf4777
commit fc69e2f7ec
1 changed files with 24 additions and 25 deletions
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49
docs/libcurl/libcurl-multi.3
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@ -5,7 +5,7 @@
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2014, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" * Copyright (C) 1998 - 2015, 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
@ -51,28 +51,27 @@ To use the multi interface, you must first create a 'multi handle' with
\fIcurl_multi_init(3)\fP. This handle is then used as input to all further
curl_multi_* functions.
With a multi handle and the multi interface you can do any amount of
simultaneous transfers in parallel. Each single transfer is built up around an
easy handle. You must create the easy handles you need, and setup the
appropriate options for each easy handle, as outlined in the \fIlibcurl(3)\fP
man page, using \fIcurl_easy_setopt(3)\fP.
With a multi handle and the multi interface you can do several simultaneous
transfers in parallel. Each single transfer is built up around an easy
handle. You create all the easy handles you need, and setup the appropriate
options for each easy handle using \fIcurl_easy_setopt(3)\fP.
There are two flavours of the multi interface, the select() oriented one and
the event based one we called multi_socket. You will benefit from reading
through the description of both versions to full understand how they work and
the event based one we call multi_socket. You will benefit from reading
through the description of both versions to fully understand how they work and
differentiate. We start out with the select() oriented version.
When an easy handle is setup for a transfer, then instead of using
When an easy handle is setup and ready for transfer, then instead of using
\fIcurl_easy_perform(3)\fP like when using the easy interface for transfers,
you should add the easy handle to the multi handle with
\fIcurl_multi_add_handle(3)\fP. The multi handle is sometimes referred to as a
\'multi stack\' because of the fact that it may hold a large amount of easy
handles.
\fIcurl_multi_add_handle(3)\fP. You can add more easy handles to a multi
handle at any point, even if other transfers are already running.
Should you change your mind, the easy handle is again removed from the multi
stack using \fIcurl_multi_remove_handle(3)\fP. Once removed from the multi
handle, you can again use other easy interface functions like
\fIcurl_easy_perform(3)\fP on the handle or whatever you think is necessary.
\fIcurl_easy_perform(3)\fP on the handle or whatever you think is
necessary. You can remove handles at any point in time during transfers.
Adding the easy handle to the multi handle does not start the transfer.
Remember that one of the main ideas with this interface is to let your
@ -84,16 +83,16 @@ current transfers in the multi stack that are ready to transfer anything. It
may be all, it may be none. When there's nothing more to do for now, it
returns back to the calling application.
Your application can acquire knowledge from libcurl when it would like to get
invoked to transfer data, so that you don't have to busy-loop and call that
\fIcurl_multi_perform(3)\fP like crazy. \fIcurl_multi_fdset(3)\fP offers an
interface using which you can extract fd_sets from libcurl to use in select()
or poll() calls in order to get to know when the transfers in the multi stack
might need attention. This also makes it very easy for your program to wait
for input on your own private file descriptors at the same time or perhaps
timeout every now and then, should you want that. \fIcurl_multi_timeout(3)\fP
also helps you with providing a suitable timeout period for your select()
call.
Your application extracts info from libcurl about when it would like to get
invoked to transfer data or do other work. The most convenient way is to use
\fIcurl_multi_wait(3)\fP that will help you wait until the application should
call libcurl again. The older API to accomplish the same thing is
\fIcurl_multi_fdset(3)\fP that extracts fd_sets from libcurl to use in
select() or poll() calls in order to get to know when the transfers in the
multi stack might need attention. Both these APIs allow for your program to
wait for input on your own private file descriptors at the same time
\fIcurl_multi_timeout(3)\fP also helps you with providing a suitable timeout
period for your select() calls.
\fIcurl_multi_perform(3)\fP stores the number of still running transfers in
one of its input arguments, and by reading that you can figure out when all
@ -114,9 +113,9 @@ the multi stack. You need to first remove the easy handle with
\fIcurl_easy_cleanup(3)\fP, or possibly set new options to it and add it again
with \fIcurl_multi_add_handle(3)\fP to start another transfer.
When all transfers in the multi stack are done, cleanup the multi handle with
When all transfers in the multi stack are done, close the multi handle with
\fIcurl_multi_cleanup(3)\fP. Be careful and please note that you \fBMUST\fP
invoke separate \fIcurl_easy_cleanup(3)\fP calls on every single easy handle
invoke separate \fIcurl_easy_cleanup(3)\fP calls for every single easy handle
to clean them up properly.
If you want to re-use an easy handle that was added to the multi handle for