82 lines
2.3 KiB
Markdown
82 lines
2.3 KiB
Markdown
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---
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c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
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SPDX-License-Identifier: curl
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Title: curl_multi_assign
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Section: 3
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Source: libcurl
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See-also:
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- curl_multi_setopt (3)
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- curl_multi_socket_action (3)
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---
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# NAME
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curl_multi_assign - set data to associate with an internal socket
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# SYNOPSIS
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~~~c
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#include <curl/curl.h>
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CURLMcode curl_multi_assign(CURLM *multi_handle, curl_socket_t sockfd,
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void *sockptr);
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~~~
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# DESCRIPTION
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This function creates an association in the multi handle between the given
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socket and a private pointer of the application. This is designed for
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curl_multi_socket_action(3) uses.
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When set, the *sockptr* pointer is passed to all future socket callbacks
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for the specific *sockfd* socket.
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If the given *sockfd* is not already in use by libcurl, this function
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returns an error.
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libcurl only keeps one single pointer associated with a socket, so calling
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this function several times for the same socket makes the last set pointer get
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used.
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The idea here being that this association (socket to private pointer) is
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something that just about every application that uses this API needs and then
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libcurl can just as well do it since it already has the necessary
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functionality.
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It is acceptable to call this function from your multi callback functions.
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# EXAMPLE
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~~~c
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int main(void)
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{
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CURLM *multi = curl_multi_init();
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void *ourstructp; /* pointer to our data */
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curl_socket_t fd; /* file descriptor to associate our data with */
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/* make our struct pointer associated with socket fd */
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CURLMcode mc = curl_multi_assign(multi, fd, ourstructp);
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if(mc)
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printf("error: %s\n", curl_multi_strerror(mc));
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}
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~~~
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# AVAILABILITY
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Added in 7.15.5
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# RETURN VALUE
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The standard CURLMcode for multi interface error codes.
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# TYPICAL USAGE
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In a typical application you allocate a struct or at least use some kind of
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semi-dynamic data for each socket that we must wait for action on when using
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the curl_multi_socket_action(3) approach.
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When our socket-callback gets called by libcurl and we get to know about yet
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another socket to wait for, we can use curl_multi_assign(3) to point out
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the particular data so that when we get updates about this same socket again,
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we do not have to find the struct associated with this socket by ourselves.
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