/*
* GNU LESSER GENERAL PUBLIC LICENSE Copyright (C) 2006 The Lobo Project
*
* This library is free software; you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License as published by the Free
* Software Foundation; either version 2.1 of the License, or (at your option)
* any later version.
*
* This library 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 Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* Contact info: lobochief@users.sourceforge.net
*/
package com.nvarghese.beowulf.common.cobra.util;
import java.util.ArrayList;
import java.util.EventListener;
import java.util.EventObject;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TreeSet;
/**
* A cache with least-recently-used policy. Note that this class is not thread
* safe by itself.
*/
public class LRUCache /* implements java.io.Serializable */{
// private static final long serialVersionUID = 940427225784212823L;
private int approxMaxSize;
private final Map cacheMap = new HashMap();
private volatile transient EventDispatch2 removalEvent;
/**
* Ascending timestamp order. First is least recently used.
*/
private final TreeSet timedSet = new TreeSet();
private int currentSize = 0;
public LRUCache(final int approxMaxSize) {
this.approxMaxSize = approxMaxSize;
this.removalEvent = new RemovalDispatch();
}
private void readObject(final java.io.ObjectInputStream in) throws java.io.IOException, ClassNotFoundException {
in.defaultReadObject();
// Need to initialize transient fields here.
this.removalEvent = new RemovalDispatch();
}
public int getApproxMaxSize() {
return approxMaxSize;
}
public void setApproxMaxSize(final int approxMaxSize) {
this.approxMaxSize = approxMaxSize;
}
public void put(final Object key, final Object value, final int approxSize) {
if (approxSize > this.approxMaxSize) {
// Can't be inserted.
return;
}
OrderedValue ordVal = (OrderedValue) this.cacheMap.get(key);
if (ordVal != null) {
if (ordVal.value != value) {
this.removalEvent.fireEvent(new RemovalEvent(this, ordVal.value));
}
this.currentSize += (approxSize - ordVal.approximateSize);
this.timedSet.remove(ordVal);
ordVal.approximateSize = approxSize;
ordVal.value = value;
ordVal.touch();
this.timedSet.add(ordVal);
} else {
ordVal = new OrderedValue(key, value, approxSize);
this.cacheMap.put(key, ordVal);
this.timedSet.add(ordVal);
this.currentSize += approxSize;
}
while (this.currentSize > this.approxMaxSize) {
this.removeLRU();
}
}
private void removeLRU() {
OrderedValue ordVal = (OrderedValue) this.timedSet.first();
if (ordVal != null) {
this.removalEvent.fireEvent(new RemovalEvent(this, ordVal.value));
if (this.timedSet.remove(ordVal)) {
this.cacheMap.remove(ordVal.key);
this.currentSize -= ordVal.approximateSize;
} else {
throw new IllegalStateException("Could not remove existing tree node.");
}
} else {
throw new IllegalStateException("Cannot remove LRU since the cache is empty.");
}
}
public Object get(final Object key) {
OrderedValue ordVal = (OrderedValue) this.cacheMap.get(key);
if (ordVal != null) {
this.timedSet.remove(ordVal);
ordVal.touch();
this.timedSet.add(ordVal);
return ordVal.value;
} else {
return null;
}
}
public Object remove(final Object key) {
OrderedValue ordVal = (OrderedValue) this.cacheMap.get(key);
if (ordVal != null) {
this.removalEvent.fireEvent(new RemovalEvent(this, ordVal.value));
this.currentSize -= ordVal.approximateSize;
this.timedSet.remove(ordVal);
return ordVal.value;
} else {
return null;
}
}
public void addRemovalListener(final RemovalListener listener) {
this.removalEvent.addListener(listener);
}
public void removeRemovalListener(final RemovalListener listener) {
this.removalEvent.removeListener(listener);
}
public int getApproxSize() {
return this.currentSize;
}
public int getNumEntries() {
return this.cacheMap.size();
}
public List getEntryInfoList() {
List list = new ArrayList();
Iterator i = this.cacheMap.values().iterator();
while (i.hasNext()) {
OrderedValue ov = (OrderedValue) i.next();
Object value = ov.value;
Class vc = value == null ? null : value.getClass();
list.add(new EntryInfo(vc, ov.approximateSize));
}
return list;
}
public static class EntryInfo {
public final Class valueClass;
public final int approximateSize;
public EntryInfo(final Class valueClass, final int approximateSize) {
super();
this.valueClass = valueClass;
this.approximateSize = approximateSize;
}
public String toString() {
Class vc = this.valueClass;
String vcName = vc == null ? "<none>" : vc.getName();
return "[class=" + vcName + ",approx-size=" + this.approximateSize + "]";
}
}
private class OrderedValue implements Comparable, java.io.Serializable {
private static final long serialVersionUID = 340227625744215821L;
private long timestamp;
private int approximateSize;
private Object value;
private Object key;
private OrderedValue(final Object key, final Object value, final int approxSize) {
this.key = key;
this.value = value;
this.approximateSize = approxSize;
this.touch();
}
private final void touch() {
this.timestamp = System.currentTimeMillis();
}
public int compareTo(final Object arg0) {
if (this == arg0) {
return 0;
}
OrderedValue other = (OrderedValue) arg0;
long diff = this.timestamp - other.timestamp;
if (diff > 0) {
return +1;
} else if (diff < 0) {
return -1;
}
int hc1 = System.identityHashCode(this);
int hc2 = System.identityHashCode(other);
if (hc1 == hc2) {
hc1 = System.identityHashCode(this.value);
hc2 = System.identityHashCode(other.value);
}
return hc1 - hc2;
}
@Override
public boolean equals(Object obj) {
return super.equals(obj);
}
@Override
public int hashCode() {
return super.hashCode();
}
}
private class RemovalDispatch extends EventDispatch2 {
protected void dispatchEvent(final EventListener listener, final EventObject event) {
((RemovalListener) listener).removed((RemovalEvent) event);
}
}
}