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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 dc-square and the HiveMQ MQTT Client Project
*
* 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.Iterator;
import java.util.NoSuchElementException;
/**
* @author Silvio Giebl
*/
@NotThreadSafe
public class ChunkedArrayQueue implements Iterable {
private final int chunkSize;
private @Nullable E single;
private @Nullable Chunk producerChunk;
private @Nullable Chunk consumerChunk;
private int producerIndex;
private int consumerIndex;
private int size;
private final @NotNull ChunkedArrayQueueIterator iterator = new ChunkedArrayQueueIterator();
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 Chunk<>(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) {
Chunk producerChunk = this.producerChunk;
assert producerChunk != null;
int producerIndex = this.producerIndex;
if ((producerIndex == chunkSize) ||
((producerChunk == consumerChunk) && (producerChunk.values[producerIndex] != null))) {
if (size >= chunkSize) {
final Chunk chunk = new Chunk<>(chunkSize);
producerChunk.jumpIndex = producerIndex - 1;
producerChunk.next = chunk;
producerChunk = chunk;
this.producerChunk = chunk;
}
producerIndex = 0;
}
producerChunk.values[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 Chunk consumerChunk = this.consumerChunk;
int consumerIndex = this.consumerIndex;
final E e = consumerChunk.values[consumerIndex];
if (e == null) {
return null;
}
consumerChunk.values[consumerIndex] = null;
size--;
if (consumerIndex == consumerChunk.jumpIndex) {
assert consumerChunk.next != null;
consumerIndex = 0;
this.consumerChunk = consumerChunk.next;
} else {
consumerIndex++;
if (consumerIndex == chunkSize) {
consumerIndex = 0;
}
}
this.consumerIndex = consumerIndex;
return e;
}
public @Nullable E peek() {
if (single != null) {
return single;
}
if (consumerChunk == null) {
return null;
}
return consumerChunk.values[consumerIndex];
}
public void clear() {
//noinspection StatementWithEmptyBody
while (poll() != null) {
}
}
@Override
public @NotNull Iterator iterator() {
iterator.clear();
return iterator;
}
private static class Chunk {
final @Nullable E @NotNull [] values;
int jumpIndex = -1;
@Nullable Chunk next;
Chunk(final int chunkSize) {
//noinspection unchecked
values = (E[]) new Object[chunkSize];
}
}
private class ChunkedArrayQueueIterator implements Iterator {
private @Nullable E iteratorSingle;
private @Nullable Chunk iteratorChunk;
private int iteratorIndex;
private int iterated;
void clear() {
iteratorSingle = single;
iteratorChunk = consumerChunk;
iteratorIndex = consumerIndex;
iterated = 0;
}
@Override
public boolean hasNext() {
return iterated < size;
}
@Override
public @NotNull E next() {
final E iteratorSingle = this.iteratorSingle;
if (iteratorSingle != null) {
iterated = 1;
this.iteratorSingle = null;
return iteratorSingle;
}
if (iteratorChunk == null) {
throw new NoSuchElementException();
}
final E e = iteratorChunk.values[iteratorIndex];
if (e == null) {
throw new NoSuchElementException();
}
if (iteratorIndex == iteratorChunk.jumpIndex) {
iteratorIndex = 0;
iteratorChunk = iteratorChunk.next;
} else {
iteratorIndex++;
if (iteratorIndex == chunkSize) {
iteratorIndex = 0;
}
}
iterated++;
return e;
}
@Override
public void remove() {
if (iterated != 1) {
throw new IllegalStateException();
}
iterated = 0;
poll();
}
}
}