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libcurl.3: for multi interface connections are held in the multi handle

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... and a few more cleanups/clarifications
This commit is contained in:
Daniel Stenberg 2013-09-12 13:59:05 +02:00
parent 6f5b46855c
commit 345955e87e
1 changed files with 23 additions and 13 deletions
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36
docs/libcurl/libcurl.3
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@ -5,7 +5,7 @@
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
.\" * Copyright (C) 1998 - 2013, 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
@ -39,8 +39,15 @@ maintain while using libcurl. This essentially means you call
for details.
To transfer files, you always set up an "easy handle" using
\fIcurl_easy_init(3)\fP, but when you want the file(s) transferred you have
the option of using the "easy" interface, or the "multi" interface.
\fIcurl_easy_init(3)\fP for a single specific transfer (in either
direction). You then set your desired set of options in that handle with
\fIcurk_easy_setopt(3)\fP. Options you set with \fIcurl_easy_setopt(3)\fP will
be used on every repeated use of this handle until you either call the
function again and change the option, or you reset them all with
\fIcurl_easy_reset(3)\fP.
To actually transfer data you have the option of using the "easy" interface,
or the "multi" interface.
The easy interface is a synchronous interface with which you call
\fIcurl_easy_perform(3)\fP and let it perform the transfer. When it is
@ -51,7 +58,8 @@ The multi interface on the other hand is an asynchronous interface, that you
call and that performs only a little piece of the transfer on each invoke. It
is perfect if you want to do things while the transfer is in progress, or
similar. The multi interface allows you to select() on libcurl action, and
even to easily download multiple files simultaneously using a single thread. See further details in the \fIlibcurl-multi(3)\fP man page.
even to easily download multiple files simultaneously using a single
thread. See further details in the \fIlibcurl-multi(3)\fP man page.
You can have multiple easy handles share certain data, even if they are used
in different threads. This magic is setup using the share interface, as
@ -115,19 +123,21 @@ Persistent connections means that libcurl can re-use the same connection for
several transfers, if the conditions are right.
libcurl will \fBalways\fP attempt to use persistent connections. Whenever you
use \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP, libcurl will
attempt to use an existing connection to do the transfer, and if none exists
it'll open a new one that will be subject for re-use on a possible following
call to \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP.
use \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP etc, libcurl
will attempt to use an existing connection to do the transfer, and if none
exists it'll open a new one that will be subject for re-use on a possible
following call to \fIcurl_easy_perform(3)\fP or \fIcurl_multi_perform(3)\fP.
To allow libcurl to take full advantage of persistent connections, you should
do as many of your file transfers as possible using the same curl handle. When
you call \fIcurl_easy_cleanup(3)\fP, all the possibly open connections held by
libcurl will be closed and forgotten.
do as many of your file transfers as possible using the same handle.
Note that the options set with \fIcurl_easy_setopt(3)\fP will be used on
every repeated \fIcurl_easy_perform(3)\fP call.
If you use the easy interface, and you call \fIcurl_easy_cleanup(3)\fP, all
the possibly open connections held by libcurl will be closed and forgotten.
When you've created a multi handle and are using the multi interface, the
connection pool is instead kept in the multi handle so closing and creating
new easy handles to do transfers will not affect them. Instead all added easy
handles can take advantage of the single shared pool.
.SH "GLOBAL CONSTANTS"
There are a variety of constants that libcurl uses, mainly through its
internal use of other libraries, which are too complicated for the