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[COLLECTIONS-432] Add CircularFifoQueue based on CircularFifoBuffer. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1468578 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Thomas Neidhart 2013-04-16 19:53:49 +00:00
parent 8961704ab4
commit d2280c28ec
5 changed files with 882 additions and 1 deletions
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415
src/main/java/org/apache/commons/collections/queue/CircularFifoQueue.java Normal file
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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.commons.collections.queue;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Queue;
import org.apache.commons.collections.BoundedCollection;
/**
* CircularFifoQueue is a first-in first-out queue with a fixed size that
* replaces its oldest element if full.
* <p>
* The removal order of a {@link CircularFifoQueue} is based on the
* insertion order; elements are removed in the same order in which they
* were added. The iteration order is the same as the removal order.
* <p>
* The {@link #add(Object)}, {@link #remove()} and {@link #get()} operations
* all perform in constant time. All other operations perform in linear
* time or worse.
* <p>
* This queue prevents null objects from being added.
*
* @since 4.0
* @version $Id$
*/
public class CircularFifoQueue<E> extends AbstractCollection<E>
implements Queue<E>, BoundedCollection<E>, Serializable {
/** Serialization version. */
private static final long serialVersionUID = -8423413834657610406L;
/** Underlying storage array. */
private transient E[] elements;
/** Array index of first (oldest) queue element. */
private transient int start = 0;
/**
* Index mod maxElements of the array position following the last queue
* element. Queue elements start at elements[start] and "wrap around"
* elements[maxElements-1], ending at elements[decrement(end)].
* For example, elements = {c,a,b}, start=1, end=1 corresponds to
* the queue [a,b,c].
*/
private transient int end = 0;
/** Flag to indicate if the queue is currently full. */
private transient boolean full = false;
/** Capacity of the queue. */
private final int maxElements;
/**
* Constructor that creates a queue with the default size of 32.
*/
public CircularFifoQueue() {
this(32);
}
/**
* Constructor that creates a queue with the specified size.
*
* @param size the size of the queue (cannot be changed)
* @throws IllegalArgumentException if the size is &lt; 1
*/
@SuppressWarnings("unchecked")
public CircularFifoQueue(final int size) {
if (size <= 0) {
throw new IllegalArgumentException("The size must be greater than 0");
}
elements = (E[]) new Object[size];
maxElements = elements.length;
}
/**
* Constructor that creates a queue from the specified collection.
* The collection size also sets the queue size.
*
* @param coll the collection to copy into the queue, may not be null
* @throws NullPointerException if the collection is null
*/
public CircularFifoQueue(final Collection<E> coll) {
this(coll.size());
addAll(coll);
}
//-----------------------------------------------------------------------
/**
* Write the queue out using a custom routine.
*
* @param out the output stream
* @throws IOException if an I/O error occurs while writing to the output stream
*/
private void writeObject(final ObjectOutputStream out) throws IOException {
out.defaultWriteObject();
out.writeInt(size());
for (final E e : this) {
out.writeObject(e);
}
}
/**
* Read the queue in using a custom routine.
*
* @param in the input stream
* @throws IOException if an I/O error occurs while writing to the output stream
* @throws ClassNotFoundException if the class of a serialized object can not be found
*/
@SuppressWarnings("unchecked")
private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
in.defaultReadObject();
elements = (E[]) new Object[maxElements];
final int size = in.readInt();
for (int i = 0; i < size; i++) {
elements[i] = (E) in.readObject();
}
start = 0;
full = size == maxElements;
if (full) {
end = 0;
} else {
end = size;
}
}
//-----------------------------------------------------------------------
/**
* Returns the number of elements stored in the queue.
*
* @return this queue's size
*/
@Override
public int size() {
int size = 0;
if (end < start) {
size = maxElements - start + end;
} else if (end == start) {
size = full ? maxElements : 0;
} else {
size = end - start;
}
return size;
}
/**
* Returns true if this queue is empty; false otherwise.
*
* @return true if this queue is empty
*/
@Override
public boolean isEmpty() {
return size() == 0;
}
/**
* {@inheritDoc}
* <p>
* A {@code CircularFifoQueue} can never be full, thus this returns always
* {@code false}.
*
* @return always returns {@code false}
*/
public boolean isFull() {
return false;
}
private boolean isAtFullCapacity() {
return size() == maxElements;
}
/**
* Gets the maximum size of the collection (the bound).
*
* @return the maximum number of elements the collection can hold
*/
public int maxSize() {
return maxElements;
}
/**
* Clears this queue.
*/
@Override
public void clear() {
full = false;
start = 0;
end = 0;
Arrays.fill(elements, null);
}
/**
* Adds the given element to this queue. If the queue is full, the least recently added
* element is discarded so that a new element can be inserted.
*
* @param element the element to add
* @return true, always
* @throws NullPointerException if the given element is null
*/
@Override
public boolean add(final E element) {
if (null == element) {
throw new NullPointerException("Attempted to add null object to queue");
}
if (isAtFullCapacity()) {
remove();
}
elements[end++] = element;
if (end >= maxElements) {
end = 0;
}
if (end == start) {
full = true;
}
return true;
}
/**
* Returns the element at the specified position in this queue.
*
* @param index the position of the element in the queue
* @return the element at position {@code index}
* @throws NoSuchElementException if the requested position is outside the range [0, size)
*/
public E get(final int index) {
final int sz = size();
if (index < 0 || index >= sz) {
throw new NoSuchElementException(
String.format("The specified index (%1$d) is outside the available range [0, %2$d)",
index, sz));
}
final int idx = (start + index) % maxElements;
return elements[idx];
}
//-----------------------------------------------------------------------
/**
* Adds the given element to this queue. If the queue is full, the least recently added
* element is discarded so that a new element can be inserted.
*
* @param element the element to add
* @return true, always
* @throws NullPointerException if the given element is null
*/
public boolean offer(E element) {
return add(element);
}
public E poll() {
if (isEmpty()) {
return null;
} else {
return remove();
}
}
public E element() {
if (isEmpty()) {
throw new NoSuchElementException("queue is empty");
} else {
return peek();
}
}
public E peek() {
if (isEmpty()) {
return null;
}
return elements[start];
}
public E remove() {
if (isEmpty()) {
throw new NoSuchElementException("queue is empty");
}
final E element = elements[start];
if (null != element) {
elements[start++] = null;
if (start >= maxElements) {
start = 0;
}
full = false;
}
return element;
}
//-----------------------------------------------------------------------
/**
* Increments the internal index.
*
* @param index the index to increment
* @return the updated index
*/
private int increment(int index) {
index++;
if (index >= maxElements) {
index = 0;
}
return index;
}
/**
* Decrements the internal index.
*
* @param index the index to decrement
* @return the updated index
*/
private int decrement(int index) {
index--;
if (index < 0) {
index = maxElements - 1;
}
return index;
}
/**
* Returns an iterator over this queue's elements.
*
* @return an iterator over this queue's elements
*/
@Override
public Iterator<E> iterator() {
return new Iterator<E>() {
private int index = start;
private int lastReturnedIndex = -1;
private boolean isFirst = full;
public boolean hasNext() {
return isFirst || index != end;
}
public E next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
isFirst = false;
lastReturnedIndex = index;
index = increment(index);
return elements[lastReturnedIndex];
}
public void remove() {
if (lastReturnedIndex == -1) {
throw new IllegalStateException();
}
// First element can be removed quickly
if (lastReturnedIndex == start) {
CircularFifoQueue.this.remove();
lastReturnedIndex = -1;
return;
}
int pos = lastReturnedIndex + 1;
if (start < lastReturnedIndex && pos < end) {
// shift in one part
System.arraycopy(elements, pos, elements, lastReturnedIndex, end - pos);
} else {
// Other elements require us to shift the subsequent elements
while (pos != end) {
if (pos >= maxElements) {
elements[pos - 1] = elements[0];
pos = 0;
} else {
elements[decrement(pos)] = elements[pos];
pos = increment(pos);
}
}
}
lastReturnedIndex = -1;
end = decrement(end);
elements[end] = null;
full = false;
index = decrement(index);
}
};
}
}

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src/main/java/org/apache/commons/collections/queue/package-info.java
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* limitations under the License. * limitations under the License.
*/ */
/** /**
* This package contains decorators for the {@link java.util.Queue Queue} interface. * This package contains implementations for the {@link java.util.Queue Queue} interface.
* <p>
* The following implementations are provided in the package:
* <ul>
* <li>CircularFifoQueue - implements a queue with a fixed size that discards oldest when full
* </ul>
* <p> * <p>
* The following decorators are provided in the package: * The following decorators are provided in the package:
* <ul> * <ul>

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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.commons.collections.queue;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Queue;
import junit.framework.Test;
import org.apache.commons.collections.BulkTest;
import org.apache.commons.collections.collection.AbstractCollectionTest;
/**
* Test cases for CircularFifoQueue.
*
* @version $Id$
*/
public class CircularFifoQueueTest<E> extends AbstractCollectionTest<E> {
public CircularFifoQueueTest(final String n) {
super(n);
}
public static Test suite() {
return BulkTest.makeSuite(CircularFifoQueueTest.class);
}
//-----------------------------------------------------------------------
/**
* Runs through the regular verifications, but also verifies that
* the buffer contains the same elements in the same sequence as the
* list.
*/
@Override
public void verify() {
super.verify();
final Iterator<E> iterator1 = getCollection().iterator();
final Iterator<E> iterator2 = getConfirmed().iterator();
while (iterator2.hasNext()) {
assertTrue(iterator1.hasNext());
final Object o1 = iterator1.next();
final Object o2 = iterator2.next();
assertEquals(o1, o2);
}
}
//-----------------------------------------------------------------------
/**
* Overridden because CircularFifoQueue doesn't allow null elements.
* @return false
*/
@Override
public boolean isNullSupported() {
return false;
}
/**
* Overridden because CircularFifoQueue isn't fail fast.
* @return false
*/
@Override
public boolean isFailFastSupported() {
return false;
}
//-----------------------------------------------------------------------
/**
* Returns an empty ArrayList.
*
* @return an empty ArrayList
*/
@Override
public Collection<E> makeConfirmedCollection() {
return new ArrayList<E>();
}
/**
* Returns a full ArrayList.
*
* @return a full ArrayList
*/
@Override
public Collection<E> makeConfirmedFullCollection() {
final Collection<E> c = makeConfirmedCollection();
c.addAll(java.util.Arrays.asList(getFullElements()));
return c;
}
/**
* Returns an empty CircularFifoQueue that won't overflow.
*
* @return an empty CircularFifoQueue
*/
@Override
public Collection<E> makeObject() {
return new CircularFifoQueue<E>(100);
}
//-----------------------------------------------------------------------
/**
* Tests that the removal operation actually removes the first element.
*/
@SuppressWarnings("unchecked")
public void testCircularFifoQueueCircular() {
final List<E> list = new ArrayList<E>();
list.add((E) "A");
list.add((E) "B");
list.add((E) "C");
final Queue<E> queue = new CircularFifoQueue<E>(list);
assertEquals(true, queue.contains("A"));
assertEquals(true, queue.contains("B"));
assertEquals(true, queue.contains("C"));
queue.add((E) "D");
assertEquals(false, queue.contains("A"));
assertEquals(true, queue.contains("B"));
assertEquals(true, queue.contains("C"));
assertEquals(true, queue.contains("D"));
assertEquals("B", queue.peek());
assertEquals("B", queue.remove());
assertEquals("C", queue.remove());
assertEquals("D", queue.remove());
}
/**
* Tests that the removal operation actually removes the first element.
*/
public void testCircularFifoQueueRemove() {
resetFull();
final int size = getConfirmed().size();
for (int i = 0; i < size; i++) {
final Object o1 = getCollection().remove();
final Object o2 = getConfirmed().remove(0);
assertEquals("Removed objects should be equal", o1, o2);
verify();
}
try {
getCollection().remove();
fail("Empty queue should raise Underflow.");
} catch (final NoSuchElementException e) {
// expected
}
}
/**
* Tests that the constructor correctly throws an exception.
*/
public void testConstructorException1() {
try {
new CircularFifoQueue<E>(0);
} catch (final IllegalArgumentException ex) {
return;
}
fail();
}
/**
* Tests that the constructor correctly throws an exception.
*/
public void testConstructorException2() {
try {
new CircularFifoQueue<E>(-20);
} catch (final IllegalArgumentException ex) {
return;
}
fail();
}
/**
* Tests that the constructor correctly throws an exception.
*/
public void testConstructorException3() {
try {
new CircularFifoQueue<E>(null);
} catch (final NullPointerException ex) {
return;
}
fail();
}
@SuppressWarnings("unchecked")
public void testRemoveError1() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5");
assertEquals("[1, 2, 3, 4, 5]", fifo.toString());
fifo.remove("3");
assertEquals("[1, 2, 4, 5]", fifo.toString());
fifo.remove("4");
assertEquals("[1, 2, 5]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError2() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5");
fifo.add((E) "6");
assertEquals(5, fifo.size());
assertEquals("[2, 3, 4, 5, 6]", fifo.toString());
fifo.remove("3");
assertEquals("[2, 4, 5, 6]", fifo.toString());
fifo.remove("4");
assertEquals("[2, 5, 6]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError3() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5");
assertEquals("[1, 2, 3, 4, 5]", fifo.toString());
fifo.remove("3");
assertEquals("[1, 2, 4, 5]", fifo.toString());
fifo.add((E) "6");
fifo.add((E) "7");
assertEquals("[2, 4, 5, 6, 7]", fifo.toString());
fifo.remove("4");
assertEquals("[2, 5, 6, 7]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError4() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5"); // end=0
fifo.add((E) "6"); // end=1
fifo.add((E) "7"); // end=2
assertEquals("[3, 4, 5, 6, 7]", fifo.toString());
fifo.remove("4"); // remove element in middle of array, after start
assertEquals("[3, 5, 6, 7]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError5() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5"); // end=0
fifo.add((E) "6"); // end=1
fifo.add((E) "7"); // end=2
assertEquals("[3, 4, 5, 6, 7]", fifo.toString());
fifo.remove("5"); // remove element at last pos in array
assertEquals("[3, 4, 6, 7]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError6() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5"); // end=0
fifo.add((E) "6"); // end=1
fifo.add((E) "7"); // end=2
assertEquals("[3, 4, 5, 6, 7]", fifo.toString());
fifo.remove("6"); // remove element at position zero in array
assertEquals("[3, 4, 5, 7]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError7() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5"); // end=0
fifo.add((E) "6"); // end=1
fifo.add((E) "7"); // end=2
assertEquals("[3, 4, 5, 6, 7]", fifo.toString());
fifo.remove("7"); // remove element at position one in array
assertEquals("[3, 4, 5, 6]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError8() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5"); // end=0
fifo.add((E) "6"); // end=1
fifo.add((E) "7"); // end=2
fifo.add((E) "8"); // end=3
assertEquals("[4, 5, 6, 7, 8]", fifo.toString());
fifo.remove("7"); // remove element at position one in array, need to shift 8
assertEquals("[4, 5, 6, 8]", fifo.toString());
}
@SuppressWarnings("unchecked")
public void testRemoveError9() throws Exception {
// based on bug 33071
final CircularFifoQueue<E> fifo = new CircularFifoQueue<E>(5);
fifo.add((E) "1");
fifo.add((E) "2");
fifo.add((E) "3");
fifo.add((E) "4");
fifo.add((E) "5"); // end=0
fifo.add((E) "6"); // end=1
fifo.add((E) "7"); // end=2
fifo.add((E) "8"); // end=3
assertEquals("[4, 5, 6, 7, 8]", fifo.toString());
fifo.remove("8"); // remove element at position two in array
assertEquals("[4, 5, 6, 7]", fifo.toString());
}
//-----------------------------------------------------------------------
@SuppressWarnings("unchecked")
public void testRepeatedSerialization() throws Exception {
// bug 31433
final CircularFifoQueue<E> b = new CircularFifoQueue<E>(2);
b.add((E) "a");
assertEquals(1, b.size());
assertEquals(true, b.contains("a"));
ByteArrayOutputStream bos = new ByteArrayOutputStream();
new ObjectOutputStream(bos).writeObject(b);
final CircularFifoQueue<E> b2 = (CircularFifoQueue<E>) new ObjectInputStream(
new ByteArrayInputStream(bos.toByteArray())).readObject();
assertEquals(1, b2.size());
assertEquals(true, b2.contains("a"));
b2.add((E) "b");
assertEquals(2, b2.size());
assertEquals(true, b2.contains("a"));
assertEquals(true, b2.contains("b"));
bos = new ByteArrayOutputStream();
new ObjectOutputStream(bos).writeObject(b2);
final CircularFifoQueue<E> b3 = (CircularFifoQueue<E>) new ObjectInputStream(
new ByteArrayInputStream(bos.toByteArray())).readObject();
assertEquals(2, b3.size());
assertEquals(true, b3.contains("a"));
assertEquals(true, b3.contains("b"));
b3.add((E) "c");
assertEquals(2, b3.size());
assertEquals(true, b3.contains("b"));
assertEquals(true, b3.contains("c"));
}
public void testGetIndex() {
resetFull();
final CircularFifoQueue<E> queue = getCollection();
final List<E> confirmed = getConfirmed();
for (int i = 0; i < confirmed.size(); i++) {
assertEquals(confirmed.get(i), queue.get(i));
}
// remove the first two elements and check again
queue.remove();
queue.remove();
for (int i = 0; i < queue.size(); i++) {
assertEquals(confirmed.get(i + 2), queue.get(i));
}
}
@Override
public String getCompatibilityVersion() {
return "4";
}
// public void testCreate() throws Exception {
// resetEmpty();
// writeExternalFormToDisk((java.io.Serializable) getCollection(), "src/test/resources/data/test/CircularFifoQueue.emptyCollection.version4.obj");
// resetFull();
// writeExternalFormToDisk((java.io.Serializable) getCollection(), "src/test/resources/data/test/CircularFifoQueue.fullCollection.version4.obj");
// }
/**
* {@inheritDoc}
*/
@Override
public CircularFifoQueue<E> getCollection() {
return (CircularFifoQueue<E>) super.getCollection();
}
/**
* {@inheritDoc}
*/
@Override
public List<E> getConfirmed() {
return (List<E>) super.getConfirmed();
}
}

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