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OptimizedQueue.java
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170 lines (137 loc) · 3.71 KB
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package com.highstar.casqueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
public class OptimizedQueue {
public interface BarrierHolder {
Object getBarrier();
}
public void test(){
OptimisticQueue<String> oq = new OptimisticQueue<String>(10);
BarrierHolder bh = new BarrierHolder() {
@Override
public Object getBarrier() {
return new Object();
}
};
for(int i=0; i<100; i++){
try {
oq.offer(bh, "shit" + i);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
for(int i=0; i<10; i++){
try {
System.out.println(oq.take(new BarrierHolder() {
@Override
public Object getBarrier() {
// TODO Auto-generated method stub
return new Object();
}
}));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
public class OptimisticQueue<T> {
private Object[] ringBuffer = null;
private AtomicInteger offerSeq = new AtomicInteger(-1);
private AtomicInteger takeSeq = new AtomicInteger(-1);
private int size;
private int mask;
public OptimisticQueue(int sizePower) {
this.size = 1 << sizePower;
this.ringBuffer = new Object[size];
for (int i = 0; i < size; i++) {
ringBuffer[i] = new Entry(i + 1);
}
this.mask = 0x7FFFFFFF >> (31 - sizePower);
}
@SuppressWarnings("unchecked")
private Entry nextOffer() {
return (Entry) ringBuffer[offerSeq.incrementAndGet() & mask];
}
@SuppressWarnings("unchecked")
private Entry nextTake() {
return (Entry) ringBuffer[takeSeq.incrementAndGet() & mask];
}
public void offer(BarrierHolder holder, T event) throws
InterruptedException {
Entry entry = nextOffer();
Object barrier = holder.getBarrier();
if (!entry.enterFront(barrier)) {
offer(holder, event);
return;
}
if (entry.event != null) {
synchronized (barrier) {
while (entry.event != null) {
barrier.wait();
}
}
}
entry.publish(event);
}
public T take(BarrierHolder consumer) throws InterruptedException {
Entry entry = nextTake();
Object barrier = consumer.getBarrier();
if (!entry.enterBack(barrier))
return take(consumer);
if (entry.event == null) {
synchronized (barrier) {
while (entry.event == null) {
barrier.wait();
}
}
}
return entry.take();
}
private class Entry {
private volatile T event = null ;
private AtomicReference < Object > backDoor = new AtomicReference < Object > ( ) ;
private AtomicReference < Object > frontDoor = new AtomicReference < Object > ( ) ;
private int id ;
public Entry ( int id ) {
this . id = id ;
}
public void publish ( T event ) {
this . event = event ;
frontDoor. set ( null ) ;
Object barrier = backDoor. get ( ) ;
if ( barrier != null ) {
synchronized ( barrier ) {
barrier. notify ( ) ;
}
}
}
public boolean enterFront ( Object barrier ) {
return frontDoor. compareAndSet ( null , barrier ) ;
}
public boolean enterBack ( Object barrier ) {
return backDoor. compareAndSet ( null , barrier ) ;
}
public T take ( ) {
T e = event ;
event = null ;
backDoor. set ( null ) ;
Object barrier = frontDoor. get ( ) ;
if ( barrier != null ) {
synchronized ( barrier ) {
barrier. notify ( ) ;
}
}
return e ;
}
public int getId() {
return id ;
}
}
}
public static void main(String[] args) {
OptimizedQueue queue = new OptimizedQueue();
queue.test();
}
}