co.paralleluniverse.strands.queues.CircularObjectBuffer Maven / Gradle / Ivy
/*
* Quasar: lightweight threads and actors for the JVM.
* Copyright (c) 2013-2014, Parallel Universe Software Co. All rights reserved.
*
* This program and the accompanying materials are dual-licensed under
* either the terms of the Eclipse Public License v1.0 as published by
* the Eclipse Foundation
*
* or (per the licensee's choosing)
*
* under the terms of the GNU Lesser General Public License version 3.0
* as published by the Free Software Foundation.
*/
package co.paralleluniverse.strands.queues;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
/**
*
* @author pron
*/
public class CircularObjectBuffer extends CircularBuffer {
private final Object[] array;
public CircularObjectBuffer(int size, boolean singleProducer) {
super(size, singleProducer);
this.array = new Object[capacity];
}
@Override
public boolean enq(E elem) {
long index = preEnq();
orderedSet((int) index & mask, elem); // must be orderedSet so as to not be re-ordered with tail bump in postEnq
postEnq();
return true;
}
@Override
public Consumer newConsumer() {
return new ObjectConsumer();
}
private class ObjectConsumer extends Consumer {
private Object value;
@Override
protected void grabValue(int index) {
value = array[index];
}
@Override
protected void clearValue() {
value = null;
}
@Override
protected E getValue() {
return (E) value;
}
}
//////////////////////////
private static final VarHandle ARRAY = MethodHandles.arrayElementVarHandle(Object[].class);
private void orderedSet(int i, Object value) {
ARRAY.setOpaque(array, i, value);
}
// private static final int base;
// private static final int shift;
//
// static {
// try {
// base = UNSAFE.arrayBaseOffset(Object[].class);
// int scale = UNSAFE.arrayIndexScale(Object[].class);
// if ((scale & (scale - 1)) != 0)
// throw new Error("data type scale not a power of two");
// shift = 31 - Integer.numberOfLeadingZeros(scale);
// } catch (Exception ex) {
// throw new Error(ex);
// }
// }
//
// private static long byteOffset(int i) {
// return ((long) i << shift) + base;
// }
//
// private void orderedSet(int i, Object value) {
// UNSAFE.putOrderedObject(array, byteOffset(i), value);
// }
}