/*
* Copyright (C) 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.facebook.collections.specialized;
import cern.colt.list.LongArrayList;
import cern.colt.map.OpenLongObjectHashMap;
import java.util.AbstractSet;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* uses
*
* http://acs.lbl.gov/software/colt/
*
* to implement a memory efficient hash set
*/
public class ColtHashSet extends AbstractSet<Long>
implements SnapshotableSet<Long> {
private static final Object TRUE = new Object();
private final OpenLongObjectHashMap map;
private volatile long version = Long.MIN_VALUE;
public ColtHashSet(
int initialCapacity, double minLoadFactor, double maxLoadFactor
) {
map = new OpenLongObjectHashMap(
initialCapacity, minLoadFactor, maxLoadFactor
);
}
public ColtHashSet(int initialCapacity) {
map = new OpenLongObjectHashMap(initialCapacity);
}
@Override
public synchronized boolean add(Long aLong) {
version++;
return map.put(aLong, TRUE);
}
@Override
public Iterator<Long> iterator() {
return new Iter();
}
@Override
public synchronized int size() {
return map.size();
}
private class Iter implements Iterator<Long> {
private final LongArrayList mapKeyList = map.keys();
private int index = 0;
private long versionSnapshot = version;
private boolean canRemove = false;
@Override
public boolean hasNext() {
synchronized (ColtHashSet.this) {
return index < mapKeyList.size();
}
}
@Override
public Long next() {
synchronized (ColtHashSet.this) {
if (versionSnapshot != version) {
throw new ConcurrentModificationException();
}
if (index >= mapKeyList.size()) {
throw new NoSuchElementException();
}
long value = mapKeyList.getQuick(index);
index++;
canRemove = true;
return value;
}
}
@Override
public void remove() {
synchronized (ColtHashSet.this) {
if (!canRemove) {
throw new IllegalStateException(
"repeated remove() calls or next() not called"
);
}
map.removeKey(mapKeyList.get(index-1));
canRemove = false;
version++;
versionSnapshot = version;
}
}
}
@Override
public SnapshotableSet<Long> makeSnapshot() {
// map.clone() makes a proper deep copy
return (SnapshotableSet<Long>) map.clone();
}
@Override
public SnapshotableSet<Long> makeTransientSnapshot() {
return makeSnapshot();
}
}