BDB 4.1.24

bdb/rpc_server/java/FreeList.java

@@ -0,0 +1,102 @@
+/*-
+ * See the file LICENSE for redistribution information.
+ *
+ * Copyright (c) 2001-2002
+ *      Sleepycat Software.  All rights reserved.
+ *
+ * $Id: FreeList.java,v 1.3 2002/08/09 01:56:09 bostic Exp $
+ */
+
+package com.sleepycat.db.rpcserver;
+
+import java.util.*;
+
+/**
+ * Keep track of a list of objects by id with a free list.
+ * Intentionally package-protected exposure.
+ */
+class FreeList
+{
+	class FreeIndex {
+		int index;
+		FreeIndex(int index) { this.index = index; }
+		int getIndex() { return index; }
+	}
+
+	Vector items = new Vector();
+	FreeIndex free_head = null;
+
+	public synchronized int add(Object obj) {
+		int pos;
+		if (free_head == null) {
+			pos = items.size();
+			items.addElement(obj);
+			if (pos % 1000 == 0)
+				DbServer.err.println(this + " grew to size " + pos);
+		} else {
+			pos = free_head.getIndex();
+			free_head = (FreeIndex)items.elementAt(pos);
+			items.setElementAt(obj, pos);
+		}
+		return pos;
+	}
+
+	public synchronized void del(int pos) {
+		Object obj = items.elementAt(pos);
+		if (obj != null && obj instanceof FreeIndex)
+			throw new NoSuchElementException("index " + pos + " has already been freed");
+		items.setElementAt(free_head, pos);
+		free_head = new FreeIndex(pos);
+	}
+
+	public void del(Object obj) {
+		del(items.indexOf(obj));
+	}
+
+	public Object get(int pos) {
+		Object obj = items.elementAt(pos);
+		if (obj instanceof FreeIndex)
+			obj = null;
+		return obj;
+	}
+
+	public LocalIterator iterator() {
+		return new FreeListIterator();
+	}
+
+	/**
+	 * Iterator for a FreeList.  Note that this class doesn't implement
+	 * java.util.Iterator to maintain compatibility with Java 1.1
+	 * Intentionally package-protected exposure.
+	 */
+	class FreeListIterator implements LocalIterator {
+		int current;
+
+		FreeListIterator() { current = findNext(-1); }
+
+		private int findNext(int start) {
+			int next = start;
+			while (++next < items.size()) {
+				Object obj = items.elementAt(next);
+				if (obj == null || !(obj instanceof FreeIndex))
+					break;
+			}
+			return next;
+		}
+
+		public boolean hasNext() {
+			return (findNext(current) < items.size());
+		}
+
+		public Object next() {
+			current = findNext(current);
+			if (current == items.size())
+				throw new NoSuchElementException("enumerated past end of FreeList");
+			return items.elementAt(current);
+		}
+
+		public void remove() {
+			del(current);
+		}
+	}
+}