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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.tools.ant.types.resources;
import java.util.ConcurrentModificationException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.WeakHashMap;
import org.apache.tools.ant.types.Resource;
/**
* Helper class for ResourceCollections to return Iterators
* that fail on changes to the object.
* @since Ant 1.7
*/
/*package-private*/ class FailFast implements Iterator<Resource> {
private static final WeakHashMap<Object, Set<FailFast>> MAP = new WeakHashMap<Object, Set<FailFast>>();
/**
* Invalidate any in-use Iterators from the specified Object.
* @param o the parent Object.
*/
static synchronized void invalidate(Object o) {
Set<FailFast> s = MAP.get(o);
if (s != null) {
s.clear();
}
}
private static synchronized void add(FailFast f) {
Set<FailFast> s = MAP.get(f.parent);
if (s == null) {
s = new HashSet<FailFast>();
MAP.put(f.parent, s);
}
s.add(f);
}
private static synchronized void remove(FailFast f) {
Set<FailFast> s = MAP.get(f.parent);
if (s != null) {
s.remove(f);
}
}
private static synchronized void failFast(FailFast f) {
Set<FailFast> s = MAP.get(f.parent);
if (!s.contains(f)) {
throw new ConcurrentModificationException();
}
}
private final Object parent;
private Iterator<Resource> wrapped;
/**
* Construct a new FailFast Iterator wrapping the specified Iterator
* and dependent upon the specified parent Object.
* @param o the parent Object.
* @param i the wrapped Iterator.
*/
FailFast(Object o, Iterator<Resource> i) {
if (o == null) {
throw new IllegalArgumentException("parent object is null");
}
if (i == null) {
throw new IllegalArgumentException("cannot wrap null iterator");
}
parent = o;
if (i.hasNext()) {
wrapped = i;
add(this);
}
}
/**
* Fulfill the Iterator contract.
* @return true if there are more elements.
*/
public boolean hasNext() {
if (wrapped == null) {
return false;
}
failFast(this);
return wrapped.hasNext();
}
/**
* Fulfill the Iterator contract.
* @return the next element.
* @throws NoSuchElementException if no more elements.
*/
public Resource next() {
if (wrapped == null || !wrapped.hasNext()) {
throw new NoSuchElementException();
}
failFast(this);
try {
return wrapped.next();
} finally {
if (!wrapped.hasNext()) {
wrapped = null;
remove(this);
}
}
}
/**
* Fulfill the Iterator contract.
* @throws UnsupportedOperationException always.
*/
public void remove() {
throw new UnsupportedOperationException();
}
}
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