.\" **************************************************************************
.\" *                                  _   _ ____  _
.\" *  Project                     ___| | | |  _ \| |
.\" *                             / __| | | | |_) | |
.\" *                            | (__| |_| |  _ <| |___
.\" *                             \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2020, 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
.\" * are also available at https://curl.haxx.se/docs/copyright.html.
.\" *
.\" * You may opt to use, copy, modify, merge, publish, distribute and/or sell
.\" * copies of the Software, and permit persons to whom the Software is
.\" * furnished to do so, under the terms of the COPYING file.
.\" *
.\" * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
.\" * KIND, either express or implied.
.\" *
.\" **************************************************************************
.TH curl_multi_assign 3 "March 23, 2020" "libcurl 7.73.0" "libcurl Manual"

.SH NAME
curl_multi_assign \- set data to associate with an internal socket
.SH SYNOPSIS
#include <curl/curl.h>

CURLMcode curl_multi_assign(CURLM *multi_handle, curl_socket_t sockfd,
                            void *sockptr);
.SH DESCRIPTION
This function creates an association in the multi handle between the given
socket and a private pointer of the application. This is designed for
\fIcurl_multi_socket_action(3)\fP uses.

When set, the \fIsockptr\fP pointer will be passed to all future socket
callbacks for the specific \fIsockfd\fP socket.

If the given \fIsockfd\fP isn't already in use by libcurl, this function will
return an error.

libcurl only keeps one single pointer associated with a socket, so calling
this function several times for the same socket will make the last set pointer
get used.

The idea here being that this association (socket to private pointer) is
something that just about every application that uses this API will need and
then libcurl can just as well do it since it already has an internal hash
table lookup for this.
.SH "RETURN VALUE"
The standard CURLMcode for multi interface error codes.
.SH "TYPICAL USAGE"
In a typical application you allocate a struct or at least use some kind of
semi-dynamic data for each socket that we must wait for action on when using
the \fIcurl_multi_socket_action(3)\fP approach.

When our socket-callback gets called by libcurl and we get to know about yet
another socket to wait for, we can use \fIcurl_multi_assign(3)\fP to point out
the particular data so that when we get updates about this same socket again,
we don't have to find the struct associated with this socket by ourselves.
.SH AVAILABILITY
This function was added in libcurl 7.15.5.
.SH "SEE ALSO"
.BR curl_multi_setopt "(3), " curl_multi_socket_action "(3) "