Chunnel patch 28392: Add: Basic tunnel pool. (no save)

https://www.tt-forums.net/viewtopic.php?p=1183416#p1183416

src/tunnel_base.h

@@ -0,0 +1,40 @@
+/* $Id$ */
+
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file tunnel_base.h Base for all tunnels */
+
+#ifndef TUNNEL_BASE_H
+#define TUNNEL_BASE_H
+
+#include "tunnel_map.h"
+#include "core/pool_type.hpp"
+
+struct Tunnel;
+
+typedef Pool<Tunnel, TunnelID, 64, 64000> TunnelPool;
+extern TunnelPool _tunnel_pool;
+
+struct Tunnel : TunnelPool::PoolItem<&_tunnel_pool> {
+
+	TileIndex tile_n; // North tile of tunnel.
+	TileIndex tile_s; // South tile of tunnel.
+
+	Tunnel(TileIndex tile_n = INVALID_TILE) : tile_n(tile_n) {}
+	~Tunnel();
+
+	static inline Tunnel *GetByTile(TileIndex tile)
+	{
+		return Tunnel::Get(GetTunnelIndex(tile));
+	}
+};
+
+#define FOR_ALL_TUNNELS_FROM(var, start) FOR_ALL_ITEMS_FROM(Tunnel, tunnel_index, var, start)
+#define FOR_ALL_TUNNELS(var) FOR_ALL_TUNNELS_FROM(var, 0)
+
+#endif /* TUNNEL_BASE_H */