com.sun.electric.tool.util.concurrent.datastructures.UnboundedDEQueue Maven / Gradle / Ivy
/* -*- tab-width: 4 -*-
*
* Electric(tm) VLSI Design System
*
* File: UnboundedDEQueue.java
*
* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
*
* Electric(tm) 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 3 of the License, or
* (at your option) any later version.
*
* Electric(tm) 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. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Electric(tm); see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, Mass 02111-1307, USA.
*/
package com.sun.electric.tool.util.concurrent.datastructures;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Unbounded double ended data structure - thread safe - unbounded
*
* @author Felix Schmidt
*/
public class UnboundedDEQueue extends IDEStructure {
private volatile CircularArray elements;
private volatile int bottom;
private AtomicInteger top;
/**
* Constructor
*/
public UnboundedDEQueue(int LOG_CAPACITY) {
elements = new CircularArray(LOG_CAPACITY);
top = new AtomicInteger(0);
bottom = 0;
}
/*
* (non-Javadoc)
*
* @see
* com.sun.electric.tool.placement.forceDirected2.utils.concurrent.IDEStructure
* #getFromTop()
*/
@Override
public T getFromTop() {
int oldTop = top.get();
int newTop = oldTop + 1;
int oldBottom = bottom;
int size = oldBottom - oldTop;
if (size <= 0) {
return null;
}
T elem = elements.get(oldTop);
if (top.compareAndSet(oldTop, newTop))
return elem;
return null;
}
/*
* (non-Javadoc)
*
* @see
* com.sun.electric.tool.placement.forceDirected2.utils.concurrent.IStructure
* #add(java.lang.Object)
*/
@Override
public void add(T item) {
int oldBottom = bottom;
int oldTop = top.get();
CircularArray currentElements = elements;
int size = oldBottom - top.get();
if (size >= currentElements.getCapacity() - 1) {
currentElements = currentElements.resize(oldBottom, oldTop);
elements = currentElements;
}
elements.add(item, oldBottom);
bottom = oldBottom + 1;
}
/*
* (non-Javadoc)
*
* @see
* com.sun.electric.tool.placement.forceDirected2.utils.concurrent.IStructure
* #get()
*/
@Override
public T remove() {
bottom--;
int oldTop = top.get();
int newTop = oldTop + 1;
int size = bottom - oldTop;
if (size < 0) {
bottom = oldTop;
return null;
}
T item = elements.get(bottom);
if (size > 0) {
return item;
}
if (!top.compareAndSet(oldTop, newTop)) {
item = null;
}
bottom = oldTop + 1;
return item;
}
/*
* (non-Javadoc)
*
* @see
* com.sun.electric.tool.placement.forceDirected2.utils.concurrent.IStructure
* #isEmpty()
*/
@Override
public boolean isEmpty() {
return (bottom <= top.get());
}
/*
* (non-Javadoc)
*
* @see com.sun.electric.tool.util.IDEStructure#isFull()
*/
@Override
@Deprecated
public boolean isFull() {
throw new UnsupportedOperationException();
}
/*
* (non-Javadoc)
*
* @see com.sun.electric.tool.util.IDEStructure#tryAdd(java.lang.Object)
*/
@Override
@Deprecated
public boolean tryAdd(T item) {
throw new UnsupportedOperationException();
}
}