curl_multi_assign(3) Library Functions Manual curl_multi_assign(3)
NAME
curl_multi_assign - set data to associate with an internal socket
SYNOPSIS
#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.
PROTOCOLS
This functionality affects all supported protocols
EXAMPLE
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));
}
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.
AVAILABILITY
Added in curl 7.15.5
RETURN VALUE
The standard CURLMcode for multi interface error codes.
SEE ALSO
curl_multi_setopt(3), curl_multi_socket_action(3)
libcurl 2024-08-05 curl_multi_assign(3)
curl 8.9.1 - Generated Sat Aug 10 12:16:41 CDT 2024