/*
* Created on 15-Mar-2006
* Created by Paul Gardner
* Copyright (C) 2006 Aelitis, All Rights Reserved.
*
* 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 2
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* AELITIS, SAS au capital de 46,603.30 euros
* 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
*
*/
package com.aelitis.azureus.core.util;
import java.lang.ref.WeakReference;
import java.util.*;
import org.gudy.azureus2.core3.util.AEDiagnostics;
import org.gudy.azureus2.core3.util.AEDiagnosticsEvidenceGenerator;
import org.gudy.azureus2.core3.util.IndentWriter;
public class
CopyOnWriteList<T>
implements Iterable<T>
{
private static final boolean LOG_STATS = false;
//private int mutation_count = 0;
private List<T> list = Collections.EMPTY_LIST;
private boolean visible = false;
private int initialCapacity;
private static CopyOnWriteList stats;
static {
if (LOG_STATS) {
stats = new CopyOnWriteList(10);
AEDiagnostics.addEvidenceGenerator(new AEDiagnosticsEvidenceGenerator() {
public void generate(IndentWriter writer) {
writer.println("COWList Info");
writer.indent();
try {
long count = 0;
long size = 0;
for (Iterator iter = stats.iterator(); iter.hasNext();) {
WeakReference wf = (WeakReference) iter.next();
CopyOnWriteList cowList = (CopyOnWriteList) wf.get();
if (cowList != null) {
count++;
size += cowList.size();
}
}
writer.println(count + " lists with " + size + " total entries");
writer.println((size/count) + " avg size");
} catch (Throwable t) {
} finally {
writer.exdent();
}
}
});
}
}
/**
* @param i
*/
public CopyOnWriteList(int initialCapacity) {
this.initialCapacity = initialCapacity;
if (stats != null) {
stats.add(new WeakReference(this));
}
}
/**
*
*/
public CopyOnWriteList() {
// Smaller default initial capacity as most of our lists are small
// Last check on 7/24/2008: 444 lists with 456 total entries
this.initialCapacity = 1;
if (stats != null) {
stats.add(new WeakReference(this));
}
}
public void
add(
T obj )
{
synchronized( this ){
if ( visible ){
List<T> new_list = new ArrayList<T>( list );
//mutated();
new_list.add( obj );
list = new_list;
visible = false;
}else{
if (list == Collections.EMPTY_LIST) {
list = new ArrayList<T>(initialCapacity);
}
list.add( obj );
}
}
}
public void
add(
int index,
T obj )
{
synchronized( this ){
if ( visible ){
List<T> new_list = new ArrayList<T>( list );
//mutated();
new_list.add( index, obj );
list = new_list;
visible = false;
}else{
if (list == Collections.EMPTY_LIST) {
list = new ArrayList<T>(initialCapacity);
}
list.add( index, obj );
}
}
}
public void
addAll(
Collection<T> c )
{
synchronized( this ){
if ( visible ){
List<T> new_list = new ArrayList<T>( list );
//mutated();
new_list.addAll( c );
list = new_list;
visible = false;
}else{
if (list == Collections.EMPTY_LIST) {
list = new ArrayList<T>(initialCapacity);
}
list.addAll( c );
}
}
}
public T
get(
int index )
{
synchronized( this ){
return( list.get(index));
}
}
public boolean
remove(
T obj )
{
synchronized( this ){
if ( visible ){
List<T> new_list = new ArrayList<T>( list );
//mutated();
boolean result = new_list.remove( obj );
list = new_list;
visible = false;
return( result );
}else{
return( list.remove( obj ));
}
}
}
public void
clear()
{
synchronized( this ){
list = Collections.EMPTY_LIST;
visible = false;
}
}
public boolean
contains(
T obj )
{
synchronized( this ){
return( list.contains( obj ));
}
}
public Iterator<T>
iterator()
{
synchronized( this ){
visible = true;
return( new CopyOnWriteListIterator( list.iterator()));
}
}
public List<T>
getList()
{
// TODO: we need to either make this a read-only-list or obey the copy-on-write semantics correctly...
synchronized( this ){
visible = true;
return( list );
}
}
public int
size()
{
synchronized( this ){
return( list.size());
}
}
public boolean
isEmpty()
{
synchronized( this ){
return list.isEmpty();
}
}
public Object[]
toArray()
{
synchronized( this ){
return( list.toArray());
}
}
public T[]
toArray(
T[] x )
{
synchronized( this ){
return( list.toArray(x));
}
}
/*
private void
mutated()
{
mutation_count++;
if ( mutation_count%10 == 0 ){
System.out.println( this + ": mut=" + mutation_count );
}
}
*/
private class
CopyOnWriteListIterator
implements Iterator<T>
{
private Iterator<T> it;
private T last;
protected
CopyOnWriteListIterator(
Iterator<T> _it )
{
it = _it;
}
public boolean
hasNext()
{
return( it.hasNext());
}
public T
next()
{
last = it.next();
return( last );
}
public void
remove()
{
// don't actually remove it from the iterator. can't go backwards with this iterator so this is
// not a problem
if ( last == null ){
throw( new IllegalStateException( "next has not been called!" ));
}
CopyOnWriteList.this.remove( last );
}
}
public int getInitialCapacity() {
return initialCapacity;
}
public void setInitialCapacity(int initialCapacity) {
this.initialCapacity = initialCapacity;
}
}