测试
static std::string_view get_state_name(int s) {
switch (s) {
case STATE_CLOSED: return "closed";
case STATE_OPENING: return "opening";
case STATE_OPEN: return "open";
case STATE_CLOSING: return "closing";
case STATE_STALE: return "stale";
case STATE_KILLING: return "killing";
default: return "???";
}
}