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engines/ultima/ultima8/misc/id_man.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program 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, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef ULTIMA8_MISC_IDMAN_H
+#define ULTIMA8_MISC_IDMAN_H
+
+#include "ultima/shared/std/containers.h"
+
+namespace Ultima {
+namespace Ultima8 {
+
+//
+// idMan. Used to allocate and keep track of unused ids.
+// Supposed to be used by Kernel and World for pID and ObjId
+//
+// The idMan itself uses a nifty linked list that is also an array.
+// As such it has the advantages of both. Adds and removals are fast,
+// As is checking to see if an ID is used.
+//
+// idMan works as a LILO (last in last out) for id recycling. So an id that has
+// been cleared will not be used until all other currently unused ids have been
+// allocated.
+//
+
+class idMan {
+	uint16      _begin;          //!< start of the available range of IDs
+	uint16      _end;            //!< current end of the range
+	uint16      _maxEnd;         //!< end of the available range
+	uint16      _startCount;     //!< number of IDs to make available initially
+
+	uint16      _usedCount;      //!< number of IDs currently in use
+
+	Std::vector<uint16> _ids;    //!< the 'next' field in a list of free IDs
+	uint16      _first;          //!< the first ID in the free list
+	uint16      _last;           //!< the last ID in the last list
+public:
+	//! \param begin start of the range of available IDs
+	//! \param max_end end of the range of available IDs
+	//! \param startcount number of IDs to make available initially (0 = all)
+	idMan(uint16 begin, uint16 max_end, uint16 startcount = 0);
+	~idMan();
+
+	//! check if this idMan is full
+	bool        isFull() const {
+		return _first == 0 && _end >= _maxEnd;
+	}
+
+	//! clear all IDs, reset size to the startcount, and set max_end to new_max
+	void        clearAll(uint16 new_max = 0);
+
+	//! get a free ID
+	//! \return a free ID, or 0 if none are available
+	uint16      getNewID();
+
+	//! mark a given ID as used, expanding if necessary.
+	//! Note: reserveID is O(n), so don't use too often.
+	//! \return false if the ID was already used or is out of range
+	bool        reserveID(uint16 id);
+
+	//! release an id
+	void        clearID(uint16 id);
+
+	//! check if an ID is in use
+	bool        isIDUsed(uint16 id) const {
+		return id >= _begin && id <= _end && _ids[id] == 0 && id != _last;
+	}
+
+	//! increase the maximum size
+	//! Note: this shouldn't be used in normal circumstances.
+	//!       It exists for dumpMap currently. If that is rewritten not
+	//!       to need more than 32768 object IDs, this function should be
+	//!       deleted.
+	void        setNewMax(uint16 maxEnd) {
+		_maxEnd = maxEnd;
+	}
+
+	void save(Common::WriteStream *ws) const;
+	bool load(Common::ReadStream *rs, uint32 version);
+
+private:
+	//! double the amount of available IDs (up to the maximum passed
+	//! to the constructor)
+	void expand();
+};
+
+} // End of namespace Ultima8
+} // End of namespace Ultima
+
+#endif