/*
* Created on May 30, 2008
* Created by Paul Gardner
*
* Copyright 2008 Vuze, Inc. 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; version 2 of the License only.
*
* 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.
*/
package com.aelitis.azureus.core.util;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
public class
CopyOnWriteSet<T>
{
private boolean is_identify;
private volatile Set<T> set;
private boolean visible = false;
public
CopyOnWriteSet(
boolean identity_hash_set )
{
is_identify = identity_hash_set;
if ( is_identify ){
set = new IdentityHashSet<T>();
}else{
set = new HashSet<T>();
}
}
public void
add(
T o )
{
synchronized( this ){
if ( visible ){
Set<T> new_set;
if ( is_identify ){
new_set = new IdentityHashSet<T>( set );
}else{
new_set = new HashSet<T>( set );
}
new_set.add( o );
set = new_set;
visible = false;
}else{
set.add( o );
}
}
}
public boolean
remove(
T o )
{
synchronized( this ){
if ( visible ){
Set<T> new_set;
if ( is_identify ){
new_set = new IdentityHashSet<T>( set );
}else{
new_set = new HashSet<T>( set );
}
boolean res = new_set.remove( o );
set = new_set;
visible = false;
return( res );
}else{
return( set.remove( o ));
}
}
}
public boolean
contains(
T o )
{
return( set.contains( o ));
}
public int
size()
{
return( set.size());
}
public Set<T>
getSet()
{
synchronized( this ){
visible = true;
return( set );
}
}
public Iterator<T>
iterator()
{
synchronized( this ){
visible = true;
return( new CopyOnWriteSetIterator( set.iterator()));
}
}
private class
CopyOnWriteSetIterator
implements Iterator<T>
{
private Iterator<T> it;
private T last;
protected
CopyOnWriteSetIterator(
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!" ));
}
CopyOnWriteSet.this.remove( last );
}
}
}