Function FreeTrainTrackReservation

src/train_cmd.cpp:2419–2478

* Free the reserved path in front of a vehicle. * @param v %Train owning the reserved path. */

 * @param v %Train owning the reserved path.
 */
void FreeTrainTrackReservation(const Train *v)
{
	assert(v->IsFrontEngine());

	TileIndex tile = v->tile;
	Trackdir  td = v->GetVehicleTrackdir();
	bool      free_tile = !(IsRailStationTile(v->tile) || IsTileType(v->tile, MP_TUNNELBRIDGE));
	StationID station_id = IsRailStationTile(v->tile) ? GetStationIndex(v->tile) : StationID::Invalid();

	/* Can't be holding a reservation if we enter a depot. */
	if (IsRailDepotTile(tile) && TrackdirToExitdir(td) != GetRailDepotDirection(tile)) return;
	if (v->track == TRACK_BIT_DEPOT) {
		/* Front engine is in a depot. We enter if some part is not in the depot. */
		for (const Train *u = v; u != nullptr; u = u->Next()) {
			if (u->track != TRACK_BIT_DEPOT || u->tile != v->tile) return;
		}
	}
	/* Don't free reservation if it's not ours. */
	if (TracksOverlap(GetReservedTrackbits(tile) | TrackToTrackBits(TrackdirToTrack(td)))) return;

	CFollowTrackRail ft(v, GetAllCompatibleRailTypes(v->railtypes));
	while (ft.Follow(tile, td)) {
		tile = ft.new_tile;
		TrackdirBits bits = ft.new_td_bits & TrackBitsToTrackdirBits(GetReservedTrackbits(tile));
		td = RemoveFirstTrackdir(&bits);
		assert(bits == TRACKDIR_BIT_NONE);

		if (!IsValidTrackdir(td)) break;

		if (IsTileType(tile, MP_RAILWAY)) {
			if (HasSignalOnTrackdir(tile, td) && !IsPbsSignal(GetSignalType(tile, TrackdirToTrack(td)))) {
				/* Conventional signal along trackdir: remove reservation and stop. */
				UnreserveRailTrack(tile, TrackdirToTrack(td));
				break;
			}
			if (HasPbsSignalOnTrackdir(tile, td)) {
				if (GetSignalStateByTrackdir(tile, td) == SIGNAL_STATE_RED) {
					/* Red PBS signal? Can't be our reservation, would be green then. */
					break;
				} else {
					/* Turn the signal back to red. */
					SetSignalStateByTrackdir(tile, td, SIGNAL_STATE_RED);
					MarkTileDirtyByTile(tile);
				}
			} else if (HasPbsSignalOnTrackdir(tile, ReverseTrackdir(td))) {
				/* Reservation passes an opposing path signal. Mark signal for update to re-establish the proper default state. */
				AddSideToSignalBuffer(tile, TrackdirToExitdir(ReverseTrackdir(td)), v->owner);
			} else if (HasSignalOnTrackdir(tile, ReverseTrackdir(td)) && IsOnewaySignal(tile, TrackdirToTrack(td))) {
				break;
			}
		}

		/* Don't free first station/bridge/tunnel if we are on it. */
		if (free_tile || (!(ft.is_station && GetStationIndex(ft.new_tile) == station_id) && !ft.is_tunnel && !ft.is_bridge)) ClearPathReservation(v, tile, td);

		free_tile = true;
	}