/*
* JBoss, Home of Professional Open Source.
* Copyright 2014 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* 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 io.undertow.util;
import java.util.
Collection;
import java.util.
Collections;
import java.util.
HashMap;
import java.util.
Map;
import java.util.
Set;
import java.util.concurrent.
ConcurrentMap;
/**
* A basic copy on write map. It simply delegates to an underlying map, that is swapped out
* every time the map is updated.
*
* Note: this is not a secure map. It should not be used in situations where the map is populated
* from user input.
*
* @author Stuart Douglas
*/
public class
CopyOnWriteMap<K,V> implements
ConcurrentMap<K, V> {
private volatile
Map<K, V>
delegate =
Collections.
emptyMap();
public
CopyOnWriteMap() {
}
public
CopyOnWriteMap(
Map<K, V>
existing) {
this.
delegate = new
HashMap<>(
existing);
}
@
Override
public synchronized V
putIfAbsent(K
key, V
value) {
final
Map<K, V>
delegate = this.
delegate;
V
existing =
delegate.
get(
key);
if(
existing != null) {
return
existing;
}
putInternal(
key,
value);
return null;
}
@
Override
public synchronized boolean
remove(
Object key,
Object value) {
final
Map<K, V>
delegate = this.
delegate;
V
existing =
delegate.
get(
key);
if(
existing.
equals(
value)) {
removeInternal(
key);
return true;
}
return false;
}
@
Override
public synchronized boolean
replace(K
key, V
oldValue, V
newValue) {
final
Map<K, V>
delegate = this.
delegate;
V
existing =
delegate.
get(
key);
if(
existing.
equals(
oldValue)) {
putInternal(
key,
newValue);
return true;
}
return false;
}
@
Override
public synchronized V
replace(K
key, V
value) {
final
Map<K, V>
delegate = this.
delegate;
V
existing =
delegate.
get(
key);
if(
existing != null) {
putInternal(
key,
value);
return
existing;
}
return null;
}
@
Override
public int
size() {
return
delegate.
size();
}
@
Override
public boolean
isEmpty() {
return
delegate.
isEmpty();
}
@
Override
public boolean
containsKey(
Object key) {
return
delegate.
containsKey(
key);
}
@
Override
public boolean
containsValue(
Object value) {
return
delegate.
containsValue(
value);
}
@
Override
public V
get(
Object key) {
return
delegate.
get(
key);
}
@
Override
public synchronized V
put(K
key, V
value) {
return
putInternal(
key,
value);
}
@
Override
public synchronized V
remove(
Object key) {
return
removeInternal(
key);
}
@
Override
public synchronized void
putAll(
Map<? extends K, ? extends V>
m) {
final
Map<K, V>
delegate = new
HashMap<>(this.
delegate);
for(
Entry<? extends K, ? extends V>
e :
m.
entrySet()) {
delegate.
put(
e.
getKey(),
e.
getValue());
}
this.
delegate =
delegate;
}
@
Override
public synchronized void
clear() {
delegate =
Collections.
emptyMap();
}
@
Override
public
Set<K>
keySet() {
return
delegate.
keySet();
}
@
Override
public
Collection<V>
values() {
return
delegate.
values();
}
@
Override
public
Set<
Entry<K, V>>
entrySet() {
return
delegate.
entrySet();
}
//must be called under lock
private V
putInternal(final K
key, final V
value) {
final
Map<K, V>
delegate = new
HashMap<>(this.
delegate);
V
existing =
delegate.
put(
key,
value);
this.
delegate =
delegate;
return
existing;
}
public V
removeInternal(final
Object key) {
final
Map<K, V>
delegate = new
HashMap<>(this.
delegate);
V
existing =
delegate.
remove(
key);
this.
delegate =
delegate;
return
existing;
}
}