curl/docs/libcurl/curl_multi_assign.3
Jay Satiro e0dc9765a7 multi: allow user callbacks to call curl_multi_assign
Several years ago a change was made to block user callbacks from calling
back into the API when not supported (recursive calls). One of the calls
blocked was curl_multi_assign. Recently the blocking was extended to the
multi interface API, however curl_multi_assign may need to be called
from within those user callbacks (eg CURLMOPT_SOCKETFUNCTION).

I can't think of any callback where it would be unsafe to call
curl_multi_assign so I removed the restriction entirely.

Reported-by: Michael Wallner

Ref: https://github.com/curl/curl/commit/b46cfbc
Ref: https://github.com/curl/curl/commit/340bb19

Fixes https://github.com/curl/curl/issues/8480
Closes https://github.com/curl/curl/pull/8483
2022-02-21 03:23:12 -05:00

73 lines
3.1 KiB
Groff

.\" **************************************************************************
.\" * _ _ ____ _
.\" * Project ___| | | | _ \| |
.\" * / __| | | | |_) | |
.\" * | (__| |_| | _ <| |___
.\" * \___|\___/|_| \_\_____|
.\" *
.\" * Copyright (C) 1998 - 2021, 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.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 "9 Jul 2006" "libcurl 7.16.0" "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) "