2
0
mirror of https://github.com/curl/curl.git synced 2025-03-07 15:27:17 +08:00
curl/docs/libcurl/curl_multi_assign.md
Daniel Stenberg eefcc1bda4
docs: introduce "curldown" for libcurl man page format
curldown is this new file format for libcurl man pages. It is markdown
inspired with differences:

- Each file has a set of leading headers with meta-data
- Supports a small subset of markdown
- Uses .md file extensions for editors/IDE/GitHub to treat them nicely
- Generates man pages very similar to the previous ones
- Generates man pages that still convert nicely to HTML on the website
- Detects and highlights mentions of curl symbols automatically (when
  their man page section is specified)

tools:

- cd2nroff: converts from curldown to nroff man page
- nroff2cd: convert an (old) nroff man page to curldown
- cdall: convert many nroff pages to curldown versions
- cd2cd: verifies and updates a curldown to latest curldown

This setup generates .3 versions of all the curldown versions at build time.

CI:

Since the documentation is now technically markdown in the eyes of many
things, the CI runs many more tests and checks on this documentation,
including proselint, link checkers and tests that make sure we capitalize the
first letter after a period...

Closes 
2024-01-23 00:29:02 +01:00

82 lines
2.3 KiB
Markdown

---
c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
SPDX-License-Identifier: curl
Title: curl_multi_assign
Section: 3
Source: libcurl
See-also:
- curl_multi_setopt (3)
- curl_multi_socket_action (3)
---
# NAME
curl_multi_assign - set data to associate with an internal socket
# SYNOPSIS
~~~c
#include <curl/curl.h>
CURLMcode curl_multi_assign(CURLM *multi_handle, curl_socket_t sockfd,
void *sockptr);
~~~
# 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
curl_multi_socket_action(3) uses.
When set, the *sockptr* pointer is passed to all future socket callbacks
for the specific *sockfd* socket.
If the given *sockfd* is not already in use by libcurl, this function
returns an error.
libcurl only keeps one single pointer associated with a socket, so calling
this function several times for the same socket makes 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 needs and then
libcurl can just as well do it since it already has the necessary
functionality.
It is acceptable to call this function from your multi callback functions.
# EXAMPLE
~~~c
int main(void)
{
CURLM *multi = curl_multi_init();
void *ourstructp; /* pointer to our data */
curl_socket_t fd; /* file descriptor to associate our data with */
/* make our struct pointer associated with socket fd */
CURLMcode mc = curl_multi_assign(multi, fd, ourstructp);
if(mc)
printf("error: %s\n", curl_multi_strerror(mc));
}
~~~
# AVAILABILITY
Added in 7.15.5
# RETURN VALUE
The standard CURLMcode for multi interface error codes.
# 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 curl_multi_socket_action(3) approach.
When our socket-callback gets called by libcurl and we get to know about yet
another socket to wait for, we can use curl_multi_assign(3) 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.