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HiveMQ MQTT Client is an MQTT 5.0 and MQTT 3.1.1 compatible and feature-rich high-performance Java client library with different API flavours and backpressure support
/*
* Copyright 2018-present HiveMQ and the HiveMQ Community
*
* 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 com.hivemq.client.internal.util.collections;
import com.hivemq.client.internal.annotations.NotThreadSafe;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.util.NoSuchElementException;
/**
* @author Silvio Giebl
*/
@NotThreadSafe
public class ChunkedArrayQueue implements Iterable {
private final int chunkSize;
private @Nullable E single;
private @Nullable Object @Nullable [] producerChunk;
private @Nullable Object @Nullable [] consumerChunk;
private int producerIndex;
private int consumerIndex;
private int size;
public ChunkedArrayQueue(final int chunkSize) {
this.chunkSize = chunkSize;
}
public int size() {
return size;
}
public boolean isEmpty() {
return size == 0;
}
public void offer(final @NotNull E e) {
if (size == 0) {
size = 1;
single = e;
return;
}
if (size == 1) {
if (producerChunk == null) {
producerChunk = consumerChunk = new Object[chunkSize];
}
final E single = this.single;
if (single != null) {
size = 0;
this.single = null;
offerQueue(single);
}
}
offerQueue(e);
}
private void offerQueue(final @NotNull E e) {
Object[] producerChunk = this.producerChunk;
assert producerChunk != null;
int producerIndex = this.producerIndex;
if ((producerIndex == chunkSize) ||
((producerChunk == consumerChunk) && (producerChunk[producerIndex] != null))) {
if (size >= chunkSize) {
final Object[] chunk = new Object[chunkSize];
final Object o = producerChunk[producerIndex - 1];
producerChunk[producerIndex - 1] = chunk;
producerChunk = chunk;
producerChunk[0] = o;
this.producerChunk = chunk;
producerIndex = 1;
} else {
producerIndex = 0;
}
}
producerChunk[producerIndex] = e;
this.producerIndex = producerIndex + 1;
size++;
}
public @Nullable E poll() {
final E single = this.single;
if (single != null) {
size = 0;
this.single = null;
return single;
}
if (consumerChunk == null) {
return null;
}
final Object[] consumerChunk = this.consumerChunk;
int consumerIndex = this.consumerIndex;
final Object o = consumerChunk[consumerIndex];
if (o == null) {
return null;
}
consumerChunk[consumerIndex] = null;
final E e;
if (o.getClass() == Object[].class) {
final Object[] nextChunk = (Object[]) o;
this.consumerChunk = nextChunk;
consumerIndex = 1;
//noinspection unchecked
e = (E) nextChunk[0];
nextChunk[0] = null;
} else {
//noinspection unchecked
e = (E) o;
consumerIndex++;
if (consumerIndex == chunkSize) {
consumerIndex = 0;
}
}
size--;
this.consumerIndex = consumerIndex;
return e;
}
public @Nullable E peek() {
if (single != null) {
return single;
}
if (consumerChunk == null) {
return null;
}
final Object o = consumerChunk[consumerIndex];
if (o == null) {
return null;
}
final E e;
if (o.getClass() == Object[].class) {
final Object[] nextChunk = (Object[]) o;
//noinspection unchecked
e = (E) nextChunk[0];
} else {
//noinspection unchecked
e = (E) o;
}
return e;
}
public void clear() {
//noinspection StatementWithEmptyBody
while (poll() != null) {
}
}
@Override
public @NotNull Iterator iterator() {
return new Iterator();
}
public class Iterator implements java.util.Iterator {
private @Nullable Object @Nullable [] iteratorChunk;
private int iteratorIndex;
private int iterated;
Iterator() {
reset();
}
public void reset() {
iteratorChunk = consumerChunk;
iteratorIndex = consumerIndex;
iterated = 0;
}
@Override
public boolean hasNext() {
return iterated < size;
}
@Override
public @NotNull E next() {
final E iteratorSingle = single;
if (iteratorSingle != null) {
if (iterated > 0) {
throw new NoSuchElementException();
}
iterated = 1;
return iteratorSingle;
}
if (iteratorChunk == null) {
throw new NoSuchElementException();
}
final Object o = iteratorChunk[iteratorIndex];
if (o == null) {
throw new NoSuchElementException();
}
final E e;
if (o.getClass() == Object[].class) {
final Object[] nextChunk = (Object[]) o;
this.iteratorChunk = nextChunk;
iteratorIndex = 1;
//noinspection unchecked
e = (E) nextChunk[0];
} else {
//noinspection unchecked
e = (E) o;
iteratorIndex++;
if (iteratorIndex == chunkSize) {
iteratorIndex = 0;
}
}
iterated++;
return e;
}
@Override
public void remove() {
for (int i = 0; i < iterated; i++) {
poll();
}
iterated = 0;
}
public int getIterated() {
return iterated;
}
}
}