/*
* 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.
*/
package org.jctools.queues;
import static org.jctools.util.UnsafeAccess.UNSAFE;
import static org.jctools.util.UnsafeRefArrayAccess.lpElement;
import static org.jctools.util.UnsafeRefArrayAccess.lvElement;
import static org.jctools.util.UnsafeRefArrayAccess.soElement;
import org.jctools.util.UnsafeRefArrayAccess;
abstract class SpmcArrayQueueL1Pad<E> extends ConcurrentCircularArrayQueue<E> {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpmcArrayQueueL1Pad(int capacity) {
super(capacity);
}
}
abstract class SpmcArrayQueueProducerField<E> extends SpmcArrayQueueL1Pad<E> {
protected final static long P_INDEX_OFFSET;
static {
try {
P_INDEX_OFFSET =
UNSAFE.objectFieldOffset(SpmcArrayQueueProducerField.class.getDeclaredField("producerIndex"));
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
}
}
protected long producerIndex;
public final long lvProducerIndex() {
return UNSAFE.getLongVolatile(this, P_INDEX_OFFSET);
}
protected final void soProducerIndex(long v) {
UNSAFE.putOrderedLong(this, P_INDEX_OFFSET, v);
}
public SpmcArrayQueueProducerField(int capacity) {
super(capacity);
}
}
abstract class SpmcArrayQueueL2Pad<E> extends SpmcArrayQueueProducerField<E> {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpmcArrayQueueL2Pad(int capacity) {
super(capacity);
}
}
abstract class SpmcArrayQueueConsumerField<E> extends SpmcArrayQueueL2Pad<E> {
protected final static long C_INDEX_OFFSET;
static {
try {
C_INDEX_OFFSET =
UNSAFE.objectFieldOffset(SpmcArrayQueueConsumerField.class.getDeclaredField("consumerIndex"));
} catch (NoSuchFieldException e) {
throw new RuntimeException(e);
}
}
private volatile long consumerIndex;
public SpmcArrayQueueConsumerField(int capacity) {
super(capacity);
}
public final long lvConsumerIndex() {
return consumerIndex;
}
protected final boolean casHead(long expect, long newValue) {
return UNSAFE.compareAndSwapLong(this, C_INDEX_OFFSET, expect, newValue);
}
}
abstract class SpmcArrayQueueMidPad<E> extends SpmcArrayQueueConsumerField<E> {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpmcArrayQueueMidPad(int capacity) {
super(capacity);
}
}
abstract class SpmcArrayQueueProducerIndexCacheField<E> extends SpmcArrayQueueMidPad<E> {
// This is separated from the consumerIndex which will be highly contended in the hope that this value spends most
// of it's time in a cache line that is Shared(and rarely invalidated)
private volatile long producerIndexCache;
public SpmcArrayQueueProducerIndexCacheField(int capacity) {
super(capacity);
}
protected final long lvProducerIndexCache() {
return producerIndexCache;
}
protected final void svProducerIndexCache(long v) {
producerIndexCache = v;
}
}
abstract class SpmcArrayQueueL3Pad<E> extends SpmcArrayQueueProducerIndexCacheField<E> {
long p01, p02, p03, p04, p05, p06, p07;
long p10, p11, p12, p13, p14, p15, p16, p17;
public SpmcArrayQueueL3Pad(int capacity) {
super(capacity);
}
}
public class SpmcArrayQueue<E> extends SpmcArrayQueueL3Pad<E> implements QueueProgressIndicators {
public SpmcArrayQueue(final int capacity) {
super(capacity);
}
@Override
public boolean offer(final E e) {
if (null == e) {
throw new NullPointerException();
}
final E[] buffer = this.buffer;
final long mask = this.mask;
final long currProducerIndex = lvProducerIndex();
final long offset = calcElementOffset(currProducerIndex, mask);
if (null != UnsafeRefArrayAccess.lvElement(buffer, offset)) {
long size = currProducerIndex - lvConsumerIndex();
if(size > mask) {
return false;
}
else {
// spin wait for slot to clear, buggers wait freedom
while(null != UnsafeRefArrayAccess.lvElement(buffer, offset));
}
}
UnsafeRefArrayAccess.spElement(buffer, offset, e);
// single producer, so store ordered is valid. It is also required to correctly publish the element
// and for the consumers to pick up the tail value.
soProducerIndex(currProducerIndex + 1);
return true;
}
@Override
public E poll() {
long currentConsumerIndex;
long currProducerIndexCache = lvProducerIndexCache();
do {
currentConsumerIndex = lvConsumerIndex();
if (currentConsumerIndex >= currProducerIndexCache) {
long currProducerIndex = lvProducerIndex();
if (currentConsumerIndex >= currProducerIndex) {
return null;
} else {
currProducerIndexCache = currProducerIndex;
svProducerIndexCache(currProducerIndex);
}
}
} while (!casHead(currentConsumerIndex, currentConsumerIndex + 1));
// consumers are gated on latest visible tail, and so can't see a null value in the queue or overtake
// and wrap to hit same location.
return removeElement(buffer, currentConsumerIndex, mask);
}
private E removeElement(final E[] buffer, long index, final long mask) {
final long offset = calcElementOffset(index, mask);
// load plain, element happens before it's index becomes visible
final E e = lpElement(buffer, offset);
// store ordered, make sure nulling out is visible. Producer is waiting for this value.
soElement(buffer, offset, null);
return e;
}
@Override
public E peek() {
final long mask = this.mask;
final long currProducerIndexCache = lvProducerIndexCache();
long currentConsumerIndex;
E e;
do {
currentConsumerIndex = lvConsumerIndex();
if (currentConsumerIndex >= currProducerIndexCache) {
long currProducerIndex = lvProducerIndex();
if (currentConsumerIndex >= currProducerIndex) {
return null;
} else {
svProducerIndexCache(currProducerIndex);
}
}
} while (null == (e = lvElement(buffer, calcElementOffset(currentConsumerIndex, mask))));
return e;
}
@Override
public boolean relaxedOffer(E e) {
if (null == e) {
throw new NullPointerException("Null is not a valid element");
}
final E[] buffer = this.buffer;
final long mask = this.mask;
final long producerIndex = lvProducerIndex();
final long offset = calcElementOffset(producerIndex, mask);
if (null != UnsafeRefArrayAccess.lvElement(buffer, offset)) {
return false;
}
UnsafeRefArrayAccess.spElement(buffer, offset, e);
// single producer, so store ordered is valid. It is also required to correctly publish the element
// and for the consumers to pick up the tail value.
soProducerIndex(producerIndex + 1);
return true;
}
@Override
public E relaxedPoll() {
return poll();
}
@Override
public E relaxedPeek() {
final E[] buffer = this.buffer;
final long mask = this.mask;
final long consumerIndex = lvConsumerIndex();
return lvElement(buffer, calcElementOffset(consumerIndex, mask));
}
@Override
public int drain(final Consumer<E> c) {
final int capacity = capacity();
int sum = 0;
while (sum < capacity) {
int drained = 0;
if((drained = drain(c, MpmcArrayQueue.RECOMENDED_POLL_BATCH)) == 0) {
break;
}
sum+=drained;
}
return sum;
}
@Override
public int fill(final Supplier<E> s) {
return fill(s, capacity());
}
@Override
public int drain(final Consumer<E> c, final int limit) {
final E[] buffer = this.buffer;
final long mask = this.mask;
long currProducerIndexCache = lvProducerIndexCache();
int adjustedLimit = 0;
long currentConsumerIndex;
do {
currentConsumerIndex = lvConsumerIndex();
// is there any space in the queue?
if (currentConsumerIndex >= currProducerIndexCache) {
long currProducerIndex = lvProducerIndex();
if (currentConsumerIndex >= currProducerIndex) {
return 0;
} else {
currProducerIndexCache = currProducerIndex;
svProducerIndexCache(currProducerIndex);
}
}
// try and claim up to 'limit' elements in one go
int remaining = (int) (currProducerIndexCache - currentConsumerIndex);
adjustedLimit = Math.min(remaining, limit);
} while (!casHead(currentConsumerIndex, currentConsumerIndex + adjustedLimit));
for (int i = 0; i < adjustedLimit; i++) {
c.accept(removeElement(buffer, currentConsumerIndex + i, mask));
}
return adjustedLimit;
}
@Override
public int fill(final Supplier<E> s, final int limit) {
final E[] buffer = this.buffer;
final long mask = this.mask;
long producerIndex = this.producerIndex;
for (int i = 0; i < limit; i++) {
final long offset = calcElementOffset(producerIndex, mask);
if (null != lvElement(buffer, offset)){
return i;
}
producerIndex++;
soElement(buffer, offset, s.get()); // StoreStore
soProducerIndex(producerIndex); // ordered store -> atomic and ordered for size()
}
return limit;
}
@Override
public void drain(final Consumer<E> c, final WaitStrategy w, final ExitCondition exit) {
int idleCounter = 0;
while (exit.keepRunning()) {
if(drain(c, MpmcArrayQueue.RECOMENDED_POLL_BATCH) == 0) {
idleCounter = w.idle(idleCounter);
continue;
}
idleCounter = 0;
}
}
@Override
public void fill(final Supplier<E> s, final WaitStrategy w, final ExitCondition e) {
final E[] buffer = this.buffer;
final long mask = this.mask;
long producerIndex = this.producerIndex;
int counter = 0;
while (e.keepRunning()) {
for (int i = 0; i < 4096; i++) {
final long offset = calcElementOffset(producerIndex, mask);
if (null != lvElement(buffer, offset)){// LoadLoad
counter = w.idle(counter);
continue;
}
producerIndex++;
counter=0;
soElement(buffer, offset, s.get()); // StoreStore
soProducerIndex(producerIndex); // ordered store -> atomic and ordered for size()
}
}
}
}