| /* |
| * Copyright (c) 2001-2008 Caucho Technology, Inc. All rights reserved. |
| * |
| * The Apache Software License, Version 1.1 |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. The end-user documentation included with the redistribution, if |
| * any, must include the following acknowlegement: |
| * "This product includes software developed by the |
| * Caucho Technology (http://www.caucho.com/)." |
| * Alternately, this acknowlegement may appear in the software itself, |
| * if and wherever such third-party acknowlegements normally appear. |
| * |
| * 4. The names "Burlap", "Resin", and "Caucho" must not be used to |
| * endorse or promote products derived from this software without prior |
| * written permission. For written permission, please contact |
| * info@caucho.com. |
| * |
| * 5. Products derived from this software may not be called "Resin" |
| * nor may "Resin" appear in their names without prior written |
| * permission of Caucho Technology. |
| * |
| * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
| * DISCLAIMED. IN NO EVENT SHALL CAUCHO TECHNOLOGY OR ITS CONTRIBUTORS |
| * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, |
| * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT |
| * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR |
| * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE |
| * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN |
| * IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| * @author Scott Ferguson |
| */ |
| |
| package com.alibaba.com.caucho.hessian.util; |
| |
| import java.util.concurrent.atomic.AtomicInteger; |
| import java.util.concurrent.atomic.AtomicReferenceArray; |
| |
| /** |
| * FreeList provides a simple class to manage free objects. This is useful |
| * for large data structures that otherwise would gobble up huge GC time. |
| * |
| * <p>The free list is bounded. Freeing an object when the list is full will |
| * do nothing. |
| */ |
| public final class HessianFreeList<T> { |
| private final AtomicReferenceArray<T> _freeStack; |
| private final AtomicInteger _top = new AtomicInteger(); |
| |
| /** |
| * Create a new free list. |
| * |
| * @param initialSize maximum number of free objects to store. |
| */ |
| public HessianFreeList(int size) { |
| _freeStack = new AtomicReferenceArray(size); |
| } |
| |
| /** |
| * Try to get an object from the free list. Returns null if the free list |
| * is empty. |
| * |
| * @return the new object or null. |
| */ |
| public T allocate() { |
| int top = _top.get(); |
| |
| if (top > 0 && _top.compareAndSet(top, top - 1)) |
| return _freeStack.getAndSet(top - 1, null); |
| else |
| return null; |
| } |
| |
| /** |
| * Frees the object. If the free list is full, the object will be garbage |
| * collected. |
| * |
| * @param obj the object to be freed. |
| */ |
| public boolean free(T obj) { |
| int top = _top.get(); |
| |
| if (top < _freeStack.length()) { |
| boolean isFree = _freeStack.compareAndSet(top, null, obj); |
| |
| _top.compareAndSet(top, top + 1); |
| |
| return isFree; |
| } else |
| return false; |
| } |
| |
| public boolean allowFree(T obj) { |
| return _top.get() < _freeStack.length(); |
| } |
| |
| /** |
| * Frees the object. If the free list is full, the object will be garbage |
| * collected. |
| * |
| * @param obj the object to be freed. |
| */ |
| public void freeCareful(T obj) { |
| if (checkDuplicate(obj)) |
| throw new IllegalStateException("tried to free object twice"); |
| |
| free(obj); |
| } |
| |
| /** |
| * Debugging to see if the object has already been freed. |
| */ |
| public boolean checkDuplicate(T obj) { |
| int top = _top.get(); |
| |
| for (int i = top - 1; i >= 0; i--) { |
| if (_freeStack.get(i) == obj) |
| return true; |
| } |
| |
| return false; |
| } |
| } |