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Conversant Disruptor - very high throughput Java BlockingQueue
package com.conversantmedia.util.concurrent;
/*
* #%L
* Conversant Disruptor
* ~~
* Conversantmedia.com © 2016, Conversant, Inc. Conversant® is a trademark of Conversant, Inc.
* ~~
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* #L%
*/
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;
import java.util.concurrent.locks.LockSupport;
/**
* Created by jcairns on 12/11/14.
*/
// abstract condition supporting common condition code
abstract class AbstractWaitingCondition implements Condition {
// keep track of whos waiting so we don't have to synchronize
// or notify needlessly - when nobody is waiting
private static final int MAX_WAITERS = 8;
private static final int WAITER_MASK = MAX_WAITERS-1;
private static final long WAIT_TIME = PARK_TIMEOUT;
private final AtomicReferenceArray waiter = new AtomicReferenceArray(MAX_WAITERS);
private final AtomicInteger waitCount = new PaddedAtomicInteger(0);
private final PaddedInt waitCache = new PaddedInt(0);
/**
* code below will block until test() returns false
*
* @return boolean - true if condition is not satisfied
*/
@Override
public abstract boolean test();
@Override
public void awaitNanos(long timeout) throws InterruptedException {
for (;;) {
try {
final int waitCount = this.waitCount.get();
int waitSequence = waitCount;
if (this.waitCount.compareAndSet(waitCount, waitCount + 1)) {
waitCache.value = waitCount+1;
long timeNow = System.nanoTime();
final long expires = timeNow+timeout;
final Thread t = Thread.currentThread();
if(waitCount == 0) {
// first thread spins
int spin = 0;
while(test() && expires>timeNow && !t.isInterrupted()) {
spin = Condition.progressiveYield(spin);
timeNow = System.nanoTime();
}
if(t.isInterrupted()) {
throw new InterruptedException();
}
return;
} else {
// wait to become a waiter
int spin = 0;
while(test() && !waiter.compareAndSet(waitSequence++ & WAITER_MASK, null, t) && expires>timeNow) {
if(spin < Condition.MAX_PROG_YIELD) {
spin = Condition.progressiveYield(spin);
} else {
LockSupport.parkNanos(MAX_WAITERS*Condition.PARK_TIMEOUT);
}
timeNow = System.nanoTime();
}
// are we a waiter? wait until we are awakened
while(test() && (waiter.get((waitSequence-1) & WAITER_MASK) == t) && expires>timeNow && !t.isInterrupted()) {
LockSupport.parkNanos((expires-timeNow)>>2);
timeNow = System.nanoTime();
}
if(t.isInterrupted()) {
// we are not waiting we are interrupted
while(!waiter.compareAndSet((waitSequence-1) & WAITER_MASK, t, null) && waiter.get(0) == t) {
LockSupport.parkNanos(PARK_TIMEOUT);
}
throw new InterruptedException();
}
return;
}
}
}finally{
waitCache.value = waitCount.decrementAndGet();
}
}
}
@Override
public void await() throws InterruptedException {
for(;;) {
try {
final int waitCount = this.waitCount.get();
int waitSequence = waitCount;
if (this.waitCount.compareAndSet(waitCount, waitCount + 1)) {
waitCache.value = waitCount+1;
final Thread t = Thread.currentThread();
if(waitCount == 0) {
int spin = 0;
// first thread spinning
while(test() && !t.isInterrupted()) {
spin = Condition.progressiveYield(spin);
}
if(t.isInterrupted()) {
throw new InterruptedException();
}
return;
} else {
// wait to become a waiter
int spin = 0;
while(test() && !waiter.compareAndSet(waitSequence++ & WAITER_MASK, null, t) && !t.isInterrupted()) {
if(spin < Condition.MAX_PROG_YIELD) {
spin = Condition.progressiveYield(spin);
} else {
LockSupport.parkNanos(MAX_WAITERS*Condition.PARK_TIMEOUT);
}
}
// are we a waiter? wait until we are awakened
while(test() && (waiter.get((waitSequence-1) & WAITER_MASK) == t) && !t.isInterrupted()) {
LockSupport.parkNanos(1_000_000L);
}
if(t.isInterrupted()) {
// we are not waiting we are interrupted
while(!waiter.compareAndSet((waitSequence-1) & WAITER_MASK, t, null) && waiter.get(0) == t) {
LockSupport.parkNanos(WAIT_TIME);
}
throw new InterruptedException();
}
return;
}
}
} finally {
waitCache.value = waitCount.decrementAndGet();
}
}
}
@Override
public void signal() {
// only signal if somebody is blocking for it
if (waitCache.value > 0 || (waitCache.value = waitCount.get()) > 0) {
int waitSequence = 0;
for(;;) {
Thread t;
while((t = waiter.get(waitSequence++ & WAITER_MASK)) != null) {
if(waiter.compareAndSet((waitSequence-1) & WAITER_MASK, t, null)) {
LockSupport.unpark(t);
} else {
LockSupport.parkNanos(WAIT_TIME);
}
// go through all waiters once, or return if we are finished
if(((waitSequence & WAITER_MASK) == WAITER_MASK) || (waitCache.value = waitCount.get()) == 0) {
return;
}
}
// go through all waiters once, or return if we are finished
if(((waitSequence & WAITER_MASK) == WAITER_MASK) || (waitCache.value = waitCount.get()) == 0) {
return;
}
}
}
}
}
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