Support for catching up if the netplay peer is ahead of us.

network/netplay/netplay.h

@@ -43,6 +43,7 @@ enum rarch_netplay_ctl_state
    RARCH_NETPLAY_CTL_IS_DATA_INITED,
    RARCH_NETPLAY_CTL_PAUSE,
    RARCH_NETPLAY_CTL_UNPAUSE,
+   RARCH_NETPLAY_CTL_CATCH_UP,
    RARCH_NETPLAY_CTL_LOAD_SAVESTATE,
    RARCH_NETPLAY_CTL_DISCONNECT
 };

network/netplay/netplay_frontend.c

@@ -927,6 +927,9 @@ bool netplay_driver_ctl(enum rarch_netplay_ctl_state state, void *data)
       case RARCH_NETPLAY_CTL_UNPAUSE:
          netplay_frontend_paused(netplay_data, false);
          break;
+      case RARCH_NETPLAY_CTL_CATCH_UP:
+         ret = netplay_data->catch_up;
+         break;
       case RARCH_NETPLAY_CTL_LOAD_SAVESTATE:
          netplay_load_savestate(netplay_data, (retro_ctx_serialize_info_t*)data, true);
          break;

network/netplay/netplay_private.h

@@ -409,6 +409,9 @@ struct netplay
    enum rarch_netplay_stall_reason stall;
    retro_time_t stall_time;
 
+   /* Opposite of stalling, should we be catching up? */
+   bool catch_up;
+
    /* Frequency with which to check CRCs */
    uint32_t check_frames;
 };

network/netplay/netplay_sync.c

@@ -347,6 +347,7 @@ void netplay_sync_post_frame(netplay_t *netplay)
    {
       netplay->other_frame_count = netplay->self_frame_count;
       netplay->other_ptr = netplay->self_ptr;
+      netplay->catch_up = false;
       return;
    }
 
@@ -454,6 +455,12 @@ void netplay_sync_post_frame(netplay_t *netplay)
       netplay->force_rewind = false;
    }
 
+   /* If we're behind, try to catch up */
+   if (netplay->self_frame_count < netplay->unread_frame_count - 2)
+      netplay->catch_up = true;
+   else
+      netplay->catch_up = false;
+
    /* If we're supposed to stall, rewind (we shouldn't get this far if we're
     * stalled, so this is a last resort) */
    if (netplay->stall)

runloop.c

@@ -1226,6 +1226,11 @@ int runloop_iterate(unsigned *sleep_ms)
    if (!settings->fastforward_ratio)
       return 0;
 
+#ifdef HAVE_NETWORKING
+   if (netplay_driver_ctl(RARCH_NETPLAY_CTL_CATCH_UP, NULL))
+      return 0;
+#endif
+
 end:
 
    current                        = cpu_features_get_time_usec();