static int
lock_if_free (lock_info_type *clasher, register char *lfname)
{
while (lock_file_1 (lfname, 0) == 0)
{
int locker;
if (errno != EEXIST)
return -1;
locker = current_lock_owner (clasher, lfname);
if (locker == 2)
{
FREE_LOCK_INFO (*clasher);
return 0; /* We ourselves locked it. */
}
else if (locker == 1)
return 1; /* Someone else has it. */
else if (locker == -1)
return -1; /* current_lock_owner returned strange error. */
/* We deleted a stale lock; try again to lock the file. */
}
return 0;
}
void
lock_file (Lisp_Object fn)
{
register Lisp_Object attack, orig_fn, encoded_fn;
register char *lfname, *locker;
lock_info_type lock_info;
struct gcpro gcpro1;
/* Don't do locking while dumping Emacs.
Uncompressing wtmp files uses call-process, which does not work
in an uninitialized Emacs. */
if (! NILP (Vpurify_flag))
return;
orig_fn = fn;
GCPRO1 (fn);
fn = Fexpand_file_name (fn, Qnil);
encoded_fn = ENCODE_FILE (fn);
/* Create the name of the lock-file for file fn */
MAKE_LOCK_NAME (lfname, encoded_fn);
/* See if this file is visited and has changed on disk since it was
visited. */
{
register Lisp_Object subject_buf;
subject_buf = get_truename_buffer (orig_fn);
if (!NILP (subject_buf)
&& NILP (Fverify_visited_file_modtime (subject_buf))
&& !NILP (Ffile_exists_p (fn)))
call1 (intern ("ask-user-about-supersession-threat"), fn);
}
UNGCPRO;
/* Try to lock the lock. */
if (lock_if_free (&lock_info, lfname) <= 0)
/* Return now if we have locked it, or if lock creation failed */
return;
/* Else consider breaking the lock */
locker = (char *) alloca (strlen (lock_info.user) + strlen (lock_info.host)
+ LOCK_PID_MAX + 9);
sprintf (locker, "%s@%s (pid %lu)", lock_info.user, lock_info.host,
lock_info.pid);
FREE_LOCK_INFO (lock_info);
attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker));
if (!NILP (attack))
/* User says take the lock */
{
lock_file_1 (lfname, 1);
return;
}
/* User says ignore the lock */
}