Function posrelat

freebsd/contrib/openzfs/module/lua/lstrlib.c:56–60

translate a relative string position: negative means back from end */

/* translate a relative string position: negative means back from end */
static size_t posrelat (ptrdiff_t pos, size_t len) {
  if (pos >= 0) return (size_t)pos;
  else if (0u - (size_t)pos > len) return 0;
  else return len - ((size_t)-pos) + 1;
}


static int str_sub (lua_State *L) {