/*
* 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 org.jctools.util.Pow2;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Queue;
import static org.jctools.util.UnsafeAccess.UNSAFE;
abstract class BQueueL0Pad {
protected long p00, p01, p02, p03, p04, p05, p06, p07;
protected long p10, p11, p12, p13, p14, p15, p16, p17;
}
abstract class BQueueColdFields<E> extends BQueueL0Pad {
protected static final int BUFFER_PAD = 32;
protected static final long ARRAY_BASE;
protected static final int ELEMENT_SHIFT;
protected static final int TICKS = Integer.getInteger("spin.ticks", 200);
static {
final int scale = UNSAFE.arrayIndexScale(Object[].class);
if (4 == scale) {
ELEMENT_SHIFT = 2;
} else if (8 == scale) {
ELEMENT_SHIFT = 3;
} else {
throw new IllegalStateException("Unknown pointer size");
}
ARRAY_BASE = UNSAFE.arrayBaseOffset(Object[].class)
+ (BUFFER_PAD << ELEMENT_SHIFT);
}
protected static final int OFFER_BATCH_SIZE = Integer.getInteger("offer.batch.size", 32);
protected static final int POLL_BATCH_SIZE = Integer.getInteger("poll.batch.size", 4096);
protected final int capacity;
protected final long mask;
protected final E[] buffer;
@SuppressWarnings("unchecked")
protected BQueueColdFields(int capacity) {
if (Pow2.isPowerOfTwo(capacity)) {
this.capacity = capacity;
} else {
this.capacity = Pow2.roundToPowerOfTwo(capacity);
}
mask = this.capacity - 1;
buffer = (E[]) new Object[this.capacity + BUFFER_PAD * 2];
}
}
abstract class BQueueL1Pad<E> extends BQueueColdFields<E> {
protected long p00, p01, p02, p03, p04, p05, p06, p07;
protected long p10, p11, p12, p13, p14, p15, p16, p17;
protected BQueueL1Pad(int capacity) {
super(capacity);
}
}
abstract class BQueueOfferFields<E> extends BQueueL1Pad<E> {
protected long tail;
protected long batchTail;
protected BQueueOfferFields(int capacity) {
super(capacity);
}
}
abstract class BQueueL2Pad<E> extends BQueueOfferFields<E> {
protected long p00, p01, p02, p03, p04, p05, p06, p07;
protected long p30, p31, p32, p33, p34, p35, p36, p37;
public BQueueL2Pad(int capacity) {
super(capacity);
}
}
abstract class BQueuePollFields<E> extends BQueueL2Pad<E> {
protected long head;
protected long batchHead;
protected int batchHistory = POLL_BATCH_SIZE;
protected int batchSize;
public BQueuePollFields(int capacity) {
super(capacity);
}
}
abstract class BQueueL3Pad<E> extends BQueuePollFields<E> {
protected long p00, p01, p02, p03, p04, p05, p06, p07;
protected long p50, p51, p52, p53, p54, p55, p56, p57;
protected BQueueL3Pad(int capacity) {
super(capacity);
}
}
public final class BQueue<E> extends BQueueL3Pad<E> implements Queue<E> {
public BQueue(final int capacity) {
super(capacity);
}
public boolean add(final E e) {
if (offer(e)) {
return true;
}
throw new IllegalStateException("Queue is full");
}
private long offset(long index) {
return ARRAY_BASE + ((index & mask) << ELEMENT_SHIFT);
}
public boolean offer(final E e) {
if (null == e) {
throw new NullPointerException("Null is not a valid element");
}
if (tail >= batchTail) {
if (null != UNSAFE.getObjectVolatile(buffer, offset(tail + OFFER_BATCH_SIZE))) {
return false;
}
batchTail = tail + OFFER_BATCH_SIZE;
}
UNSAFE.putOrderedObject(buffer, offset(tail), e);
tail++;
return true;
}
public E poll() {
if (head >= batchHead) {
if (!backtrackPoll()) {
return null;
}
}
final long offset = offset(head);
@SuppressWarnings("unchecked")
final E e = (E) UNSAFE.getObject(buffer, offset);
UNSAFE.putOrderedObject(buffer, offset, null);
head++;
return e;
}
boolean backtrackPoll() {
if (batchHistory < POLL_BATCH_SIZE) {
batchHistory = Math.min(POLL_BATCH_SIZE, batchHistory << 1);
}
batchSize = batchHistory;
batchHead = head + batchSize - 1;
while (UNSAFE.getObjectVolatile(buffer, offset(batchHead)) == null) {
spinWait();
if (batchSize > 1) {
batchSize = batchSize >> 1;
batchHead = head + batchSize - 1;
} else {
batchHead = head;
return false;
}
}
batchHistory = batchSize;
return true;
}
private void spinWait() {
if(TICKS == 0){
return;
}
final long deadline = System.nanoTime() + TICKS;
while(deadline >= System.nanoTime());
}
public E remove() {
final E e = poll();
if (null == e) {
throw new NoSuchElementException("Queue is empty");
}
return e;
}
public E element() {
final E e = peek();
if (null == e) {
throw new NoSuchElementException("Queue is empty");
}
return e;
}
public E peek() {
throw new UnsupportedOperationException();
}
public int size() {
return (int) (tail - head);
}
public boolean isEmpty() {
return tail == head;
}
public boolean contains(final Object o) {
throw new UnsupportedOperationException();
}
public Iterator<E> iterator() {
throw new UnsupportedOperationException();
}
public Object[] toArray() {
throw new UnsupportedOperationException();
}
public <T> T[] toArray(final T[] a) {
throw new UnsupportedOperationException();
}
public boolean remove(final Object o) {
throw new UnsupportedOperationException();
}
public boolean containsAll(final Collection<?> c) {
throw new UnsupportedOperationException();
}
public boolean addAll(final Collection<? extends E> c) {
for (final E e : c) {
add(e);
}
return true;
}
public boolean removeAll(final Collection<?> c) {
throw new UnsupportedOperationException();
}
public boolean retainAll(final Collection<?> c) {
throw new UnsupportedOperationException();
}
public void clear() {
Object value;
do {
value = poll();
} while (null != value);
}
}