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.TH curl_multi_assign 3 "May 17, 2022" "libcurl 7.86.0" "libcurl Manual"

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

CURLMcode curl_multi_assign(CURLM *multi_handle, curl_socket_t sockfd,
                            void *sockptr);
.fi
.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 is not 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.

It is acceptable to call this function from your multi callback functions.
.SH EXAMPLE
.nf
 /* make our struct pointer associated with socket fd */
 mc = curl_multi_assign(multi_handle, fd, ourstructp);
.fi
.SH AVAILABILITY
Added in 7.15.5
.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 do not have to find the struct associated with this socket by ourselves.
.SH "SEE ALSO"
.BR curl_multi_setopt "(3), " curl_multi_socket_action "(3) "