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/*-
* 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);
}
}
}
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