Function auxupvalue

extlibs/lua/src/ldblib.c:257–266

** get (if 'get' is true) or set an upvalue from a closure */

** get (if 'get' is true) or set an upvalue from a closure
*/
static int auxupvalue (lua_State *L, int get) {
  const char *name;
  int n = (int)luaL_checkinteger(L, 2);  /* upvalue index */
  luaL_checktype(L, 1, LUA_TFUNCTION);  /* closure */
  name = get ? lua_getupvalue(L, 1, n) : lua_setupvalue(L, 1, n);
  if (name == NULL) return 0;
  lua_pushstring(L, name);
  lua_insert(L, -(get+1));  /* no-op if get is false */
  return get + 1;
}


static int db_getupvalue (lua_State *L) {