+ if (now < next_sample) {
+ // not yet
+ return;
+ }
+ tx_kbps = float(tx_bytes) * (1.0f / 1024.0f);
+ rx_kbps = float(rx_bytes) * (1.0f / 1024.0f);
+ tx_bytes = 0;
+ rx_bytes = 0;
+ next_sample += 1000;
+ UpdateMode();
+}
+
+void CongestionControl::UpdateMode() noexcept {
+ Mode now_mode = Conditions();
+ if (now_mode > mode) {
+ ChangeMode(now_mode);
+ } else if (now_mode < mode) {
+ CheckUpgrade(now_mode);
+ } else {
+ KeepMode();
+ }
+}
+
+void CongestionControl::CheckUpgrade(Mode m) noexcept {
+ Uint32 now = SDL_GetTicks();
+ Uint32 time_in_mode = now - mode_entered;
+ if (time_in_mode < mode_keep_time) {
+ return;
+ }
+ ChangeMode(m);
+}
+
+void CongestionControl::ChangeMode(Mode m) noexcept {
+ Uint32 now = SDL_GetTicks();
+ if (m > mode) {
+ // changed to worse mode
+ // if we spent less than 10 seconds in better mode
+ // double keep time till up to 64 seconds
+ if (now - mode_entered < 10000) {
+ if (mode_keep_time < 64000) {
+ mode_keep_time *= 2;
+ }
+ }
+ }
+ mode = m;
+ mode_entered = now;
+ mode_reset = mode_entered;
+}
+
+void CongestionControl::KeepMode() noexcept {
+ mode_reset = SDL_GetTicks();
+ // if in good mode for 10 seconds, halve keep time till down to one second
+ if (mode == GOOD && mode_keep_time > 1000 && mode_step - mode_reset > 10000) {
+ mode_keep_time /= 2;
+ mode_step = mode_reset;
+ }
+}
+
+CongestionControl::Mode CongestionControl::Conditions() const noexcept {
+ if (rtt > ugly_rtt || packet_loss > ugly_loss) {
+ return UGLY;
+ } else if (rtt > bad_rtt || packet_loss > bad_loss) {
+ return BAD;
+ } else {
+ return GOOD;