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/*
* Copyright (c) 1998-2018 Caucho Technology -- all rights reserved
*
* This file is part of Resin(R) Open Source
*
* Each copy or derived work must preserve the copyright notice and this
* notice unmodified.
*
* Resin Open Source is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* Resin Open Source is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, or any warranty
* of NON-INFRINGEMENT. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with Resin Open Source; if not, write to the
*
* Free Software Foundation, Inc.
* 59 Temple Place, Suite 330
* Boston, MA 02111-1307 USA
*
* @author Scott Ferguson
*/
package com.caucho.util;
/**
* FreeList provides a simple class to manage free objects. This is useful
* for large data structures that otherwise would gobble up huge GC time.
*
* The free list is bounded. Freeing an object when the list is full will
* do nothing.
*/
public final class FreeRing {
private final RingValueQueue _ringQueue;
/**
* Create a new free list.
*
* @param initialSize maximum number of free objects to store.
*/
public FreeRing(int capacity)
{
_ringQueue = new RingValueQueue(capacity);
}
public int getSize()
{
return _ringQueue.size();
}
public long getHead()
{
return _ringQueue.getHead();
}
public long getHeadAlloc()
{
return _ringQueue.getHeadAlloc();
}
public long getTail()
{
return _ringQueue.getTail();
}
public long getTailAlloc()
{
return _ringQueue.getTail();
}
/**
* 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()
{
return _ringQueue.poll();
}
/**
* 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 value)
{
return _ringQueue.offer(value);
}
/**
* Frees the object. If the free list is full, the object will be garbage
* collected.
*
* @param obj the object to be freed.
*/
public boolean freeCareful(T value)
{
if (checkDuplicate(value)) {
throw new IllegalStateException("tried to free object twice: " + value);
}
return free(value);
}
/**
* Debugging to see if the object has already been freed.
*/
public boolean checkDuplicate(T obj)
{
/*
for (int i = 0; i < _size; i++) {
if (_ring.get(i) == obj) {
return true;
}
}
*/
return false;
}
}