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engines/saga2/priqueue.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/>.
+ *
+ *
+ * Based on the original sources
+ *   Faery Tale II -- The Halls of the Dead
+ *   (c) 1993-1996 The Wyrmkeep Entertainment Co.
+ */
+
+#ifndef SAGA2_PRIQUEUE_H
+#define SAGA2_PRIQUEUE_H
+
+namespace Saga2 {
+
+template <class ITEM, int size>
+class PriorityQueue {
+	int16           _tail;                   // end index of queue
+	ITEM            _queue[size + 1];
+
+	static int16 parentIndex(int16 index) {
+		return index >> 1;
+	}
+	static int16 child1Index(int16 index) {
+		return index << 1;
+	}
+	static int16 child2Index(int16 index) {
+		return (index >> 1) + 1;
+	}
+
+public:
+	PriorityQueue() {                    // constructor
+		_tail = 1;
+	}
+
+	bool insert(ITEM &newItem);              // insert an item
+	bool remove(ITEM &result);           // remove an item
+	void clear() {
+		_tail = 1;    // clear the queue
+	}
+	int16 getCount() {
+		return _tail - 1;
+	}
+};
+
+//  Function to insert an element into the queue
+
+template <class ITEM, int size>
+bool PriorityQueue<ITEM, size>::insert(ITEM &newItem) {
+	int16           index,
+	                parentIndex,
+	                newVal = (int)newItem;
+	ITEM            *qi,
+	                *parentItem;
+
+	if (_tail >= size + 1) return false;
+
+	for (index = _tail, qi = &_queue[index];
+	        index > 1;
+	        index = parentIndex, qi = parentItem) {
+		parentIndex = PriorityQueue::parentIndex(index);
+		parentItem = &_queue[parentIndex];
+
+		if ((int)*parentItem <= newVal) break;
+		*qi = *parentItem;
+	}
+	*qi = newItem;
+	_tail++;
+
+	return true;
+}
+
+//  Function to remove the lowest element from the queue
+
+template <class ITEM, int size>
+bool PriorityQueue<ITEM, size>::remove(ITEM &result) {
+	ITEM            *item = &_queue[1],
+	                 *child;
+	int16           itemNum = 1,
+	                childNum,
+	                tailVal;
+
+	if (_tail <= 1) return false;
+
+	result = *item;
+	_tail--;
+	tailVal = (int)_queue[_tail];
+
+	for (;;) {
+		childNum = child1Index(itemNum);
+		if (childNum >= _tail) break;
+
+		child = &_queue[childNum];
+
+		//  Select the lowest of the two children
+		if (childNum + 1 < _tail
+		        && (int)child[0] > (int)child[1]) {
+			childNum++;
+			child++;
+		}
+
+		if ((int)*child >= tailVal) break;
+		*item = *child;
+		item = child;
+		itemNum = childNum;
+	}
+
+	if (itemNum != _tail) {
+		*item = _queue[_tail];
+	}
+	return true;
+}
+
+} // end of namepsace Saga2
+
+#endif