CURLSHOPT_LOCKFUNC - Man Page
mutex lock callback
#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);
Set a mutex lock callback for the share object, to allow it to get used by multiple threads concurrently. There's 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. This pointer is not used by libcurl itself.
CURLSHcode sh; share = curl_share_init(); sh = curl_share_setopt(share, CURLSHOPT_LOCKFUNC, mutex_lock); if(sh) printf("Error: %s\n", curl_share_strerror(sh));
Added in 7.10
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.
CURLSHOPT_UNLOCKFUNC(3), curl_share_setopt(3), curl_share_cleanup(3), curl_share_init(3)
curl_share_setopt(3), CURLSHOPT_UNLOCKFUNC(3), CURLSHOPT_USERDATA(3).