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curl_share_setopt(3) libcurl Manual curl_share_setopt(3)

curl_share_setopt - Set options for a shared object

#include <curl/curl.h>

CURLSHcode curl_share_setopt(CURLSH *share, CURLSHoption option, parameter);

Set the option to parameter for the given share.

The parameter must be a pointer to a function matching the following prototype:

void lock_function(CURL *handle, curl_lock_data data, curl_lock_access access, void *userptr);

The data argument tells what kind of data libcurl wants to lock. Make sure that the callback uses a different lock for each kind of data.

access defines what access type libcurl wants, shared or single.

userptr is the pointer you set with CURLSHOPT_USERDATA.

The parameter must be a pointer to a function matching the following prototype:

void unlock_function(CURL *handle, curl_lock_data data, void *userptr);

data defines what data libcurl wants to unlock, and you must make sure that only one lock is given at any time for each kind of data.

userptr is the pointer you set with CURLSHOPT_USERDATA.

The parameter specifies a type of data that should be shared. This may be set to one of the values described below.
Cookie data will be shared across the easy handles using this shared object. Note that this does not activate an easy handle's cookie handling. You can do that separately by using CURLOPT_COOKIEFILE(3) for example.
Cached DNS hosts will be shared across the easy handles using this shared object. Note that when you use the multi interface, all easy handles added to the same multi handle will share DNS cache by default without using this option.
SSL session IDs will be shared across the easy handles using this shared object. This will reduce the time spent in the SSL handshake when reconnecting to the same server. Note SSL session IDs are reused within the same easy handle by default. Note this symbol was added in 7.10.3 but was not implemented until 7.23.0.
Put the connection cache in the share object and make all easy handles using this share object share the connection cache.

Note that due to a known bug, it is not safe to share connections this way between multiple concurrent threads.

Connections that are used for HTTP/1.1 Pipelining or HTTP/2 multiplexing only get additional transfers added to them if the existing connection is held by the same multi or easy handle. libcurl does not support doing HTTP/2 streams in different threads using a shared connection.

Support for CURL_LOCK_DATA_CONNECT was added in 7.57.0, but the symbol existed before this.

Note that when you use the multi interface, all easy handles added to the same multi handle will share connection cache by default without using this option.

The Public Suffix List stored in the share object is made available to all easy handle bound to the later. Since the Public Suffix List is periodically refreshed, this avoids updates in too many different contexts.

CURL_LOCK_DATA_PSL exists since 7.61.0.

Note that when you use the multi interface, all easy handles added to the same multi handle will share PSL cache by default without using this option.

This option does the opposite of CURLSHOPT_SHARE. It specifies that the specified parameter will no longer be shared. Valid values are the same as those for CURLSHOPT_SHARE.
The parameter allows you to specify a pointer to data that will be passed to the lock_function and unlock_function each time it is called.

CURLSHE_OK (zero) means that the option was set properly, non-zero means an error occurred as <curl/curl.h> defines. See the libcurl-errors.3 man page for the full list with descriptions.

curl_share_cleanup(3), curl_share_init(3)

November 4, 2020 libcurl 7.74.0