| /** |
| * 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.activemq.memory; |
| |
| /** |
| * Maintains a simple linked list of CacheEntry objects. It is thread safe. |
| * |
| * |
| */ |
| public class CacheEntryList { |
| |
| // Points at the tail of the CacheEntry list |
| public final CacheEntry tail = new CacheEntry(null, null); |
| |
| public CacheEntryList() { |
| tail.next = tail; |
| tail.previous = tail; |
| } |
| |
| public void add(CacheEntry ce) { |
| addEntryBefore(tail, ce); |
| } |
| |
| private void addEntryBefore(CacheEntry position, CacheEntry ce) { |
| assert ce.key != null && ce.next == null && ce.owner == null; |
| |
| synchronized (tail) { |
| ce.owner = this; |
| ce.next = position; |
| ce.previous = position.previous; |
| ce.previous.next = ce; |
| ce.next.previous = ce; |
| } |
| } |
| |
| public void clear() { |
| synchronized (tail) { |
| tail.next = tail; |
| tail.previous = tail; |
| } |
| } |
| |
| public CacheEvictor createFIFOCacheEvictor() { |
| return new CacheEvictor() { |
| public CacheEntry evictCacheEntry() { |
| CacheEntry rc; |
| synchronized (tail) { |
| rc = tail.next; |
| } |
| return rc.remove() ? rc : null; |
| } |
| }; |
| } |
| |
| public CacheEvictor createLIFOCacheEvictor() { |
| return new CacheEvictor() { |
| public CacheEntry evictCacheEntry() { |
| CacheEntry rc; |
| synchronized (tail) { |
| rc = tail.previous; |
| } |
| return rc.remove() ? rc : null; |
| } |
| }; |
| } |
| |
| } |