Function GetTrainForReservation

src/pbs.cpp:331–369

* Find the train which has reserved a specific path. * * @param tile A tile on the path. * @param track A reserved track on the tile. * @return The vehicle holding the reservation or nullptr if the path is stray. */

 * @return The vehicle holding the reservation or nullptr if the path is stray.
 */
Train *GetTrainForReservation(TileIndex tile, Track track)
{
	assert(HasReservedTracks(tile, TrackToTrackBits(track)));
	Trackdir  trackdir = TrackToTrackdir(track);

	RailTypes rts = GetRailTypeInfo(GetTileRailType(tile))->compatible_railtypes;

	/* Follow the path from tile to both ends, one of the end tiles should
	 * have a train on it. We need FollowReservation to ignore one-way signals
	 * here, as one of the two search directions will be the "wrong" way. */
	for (int i = 0; i < 2; ++i, trackdir = ReverseTrackdir(trackdir)) {
		/* If the tile has a one-way block signal in the current trackdir, skip the
		 * search in this direction as the reservation can't come from this side.*/
		if (HasOnewaySignalBlockingTrackdir(tile, ReverseTrackdir(trackdir)) && !HasPbsSignalOnTrackdir(tile, trackdir)) continue;

		FindTrainOnTrackInfo ftoti;
		ftoti.res = FollowReservation(GetTileOwner(tile), rts, tile, trackdir, true);

		CheckTrainsOnTrack(ftoti, ftoti.res.tile);
		if (ftoti.best != nullptr) return ftoti.best;

		/* Special case for stations: check the whole platform for a vehicle. */
		if (IsRailStationTile(ftoti.res.tile)) {
			TileIndexDiff diff = TileOffsByDiagDir(TrackdirToExitdir(ReverseTrackdir(ftoti.res.trackdir)));
			for (TileIndex st_tile = ftoti.res.tile + diff; IsCompatibleTrainStationTile(st_tile, ftoti.res.tile); st_tile += diff) {
				CheckTrainsOnTrack(ftoti, st_tile);
				if (ftoti.best != nullptr) return ftoti.best;
			}
		}

		/* Special case for bridges/tunnels: check the other end as well. */
		if (IsTileType(ftoti.res.tile, MP_TUNNELBRIDGE)) {
			CheckTrainsOnTrack(ftoti, GetOtherTunnelBridgeEnd(ftoti.res.tile));
			if (ftoti.best != nullptr) return ftoti.best;
		}
	}

	return nullptr;
}

/**
 * Determine whether a certain track on a tile is a safe position to end a path.