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Kernel for Resin Java Application Server
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/*
* Copyright (c) 1998-2012 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;
import java.util.concurrent.atomic.AtomicReferenceArray;
final class RingValueArray
{
private static final L10N L = new L10N(RingValueArray.class);
private final AtomicReferenceArray _ring;
private final int _length;
private final int _mask;
RingValueArray(int length)
{
_length = length;
if (Integer.bitCount(_length) != 1) {
throw new IllegalArgumentException(L.l("Invalid ring capacity {0}",
Long.toHexString(_length)));
}
_ring = new AtomicReferenceArray(_length);
_mask = _length - 1;
}
public final int getLength()
{
return _length;
}
public final T get(long ptr)
{
return _ring.get(getIndex(ptr));
}
public final void set(long ptr, T value)
{
_ring.set(getIndex(ptr), value);
}
public final T takeAndClear(long ptr)
{
final int index = getIndex(ptr);
final AtomicReferenceArray ring = _ring;
T value;
while ((value = ring.getAndSet(index, null)) == null) {
}
return value;
}
public final T pollAndClear(long ptr)
{
final int index = getIndex(ptr);
final AtomicReferenceArray ring = _ring;
T value = ring.get(index);
if (value != null && ring.compareAndSet(index, value, null)) {
return value;
}
else {
return null;
}
}
public final int getIndex(long ptr)
{
return (int) (ptr & _mask);
}
@Override
public String toString()
{
return (getClass().getSimpleName()
+ "[" + _ring.getClass().getSimpleName()
+ "," + getLength() + "]");
}
}