.\" generated by cd2nroff 0.1 from CURLSHOPT_LOCKFUNC.md
.TH CURLSHOPT_LOCKFUNC 3 "2024-04-19" libcurl
.SH NAME
CURLSHOPT_LOCKFUNC \- mutex lock callback
.SH SYNOPSIS
.nf
#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);
.fi
.SH DESCRIPTION
Set a mutex lock callback for the share object, to allow it to get used by
multiple threads concurrently. There is a corresponding
\fICURLSHOPT_UNLOCKFUNC(3)\fP callback called when the mutex is again released.

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

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

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

\fIaccess\fP defines what access type libcurl wants, shared or single.

\fIclientp\fP is the private pointer you set with \fICURLSHOPT_USERDATA(3)\fP.
This pointer is not used by libcurl itself.
.SH PROTOCOLS
All
.SH EXAMPLE
.nf
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));
}
.fi
.SH AVAILABILITY
Added in 7.10
.SH RETURN VALUE
CURLSHE_OK (zero) means that the option was set properly, non\-zero means an
error occurred. See \fIlibcurl\-errors(3)\fP for the full list with
descriptions.
.SH SEE ALSO
.BR CURLSHOPT_UNLOCKFUNC (3),
.BR curl_share_cleanup (3),
.BR curl_share_init (3),
.BR curl_share_setopt (3)