NAME

       CURLSHOPT_LOCKFUNC - mutex lock callback

SYNOPSIS

       #include <curl/curl.h>

       void lockcb(CURL *handle, curl_lock_data data, curl_lock_access access,
                   void *clientp);

       CURLSHcode curl_share_setopt(CURLSH *share, CURLSHOPT_LOCKFUNC, lockcb);

DESCRIPTION

       Set a mutex lock callback for the share object, to allow it to get used by multiple threads concurrently.
       There is a corresponding CURLSHOPT_UNLOCKFUNC(3) callback called when the mutex is again released.

       The  lockcb argument must be a pointer to a function matching the prototype shown above. The arguments to
       the callback are:

       handle is the currently active easy handle in use when the share object is intended to get used.

       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.

       clientp  is  the private pointer you set with CURLSHOPT_USERDATA(3).  This pointer is not used by libcurl
       itself.

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

       extern void mutex_lock(CURL *handle, curl_lock_data data,
                              curl_lock_access access, void *clientp);

       int main(void)
       {
         CURLSHcode sh;
         CURLSH *share = curl_share_init();
         sh = curl_share_setopt(share, CURLSHOPT_LOCKFUNC, mutex_lock);
         if(sh)
           printf("Error: %s\n", curl_share_strerror(sh));
       }

AVAILABILITY

       Added in curl 7.10.3

RETURN VALUE

       CURLSHE_OK (zero) means that the  option  was  set  properly,  non-zero  means  an  error  occurred.  See
       libcurl-errors(3) for the full list with descriptions.

SEE ALSO

       CURLSHOPT_UNLOCKFUNC(3), curl_share_cleanup(3), curl_share_init(3), curl_share_setopt(3)

libcurl                                            2025-06-16                              CURLSHOPT_LOCKFUNC(3)