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/*******************************************************************************
* Copyright 2015 See AUTHORS file.
*
* 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.badlogic.gdx.utils;
import java.util.Iterator;
import java.util.NoSuchElementException;
import com.badlogic.gdx.utils.reflect.ArrayReflection;
/** A resizable, ordered array of objects with efficient add and remove at the beginning and end. Values in the backing array may
* wrap back to the beginning, making add and remove at the beginning and end O(1) (unless the backing array needs to resize when
* adding). Deque functionality is provided via {@link #removeLast()} and {@link #addFirst(Object)}. */
public class Queue implements Iterable {
/** Contains the values in the queue. Head and tail indices go in a circle around this array, wrapping at the end. */
protected T[] values;
/** Index of first element. Logically smaller than tail. Unless empty, it points to a valid element inside queue. */
protected int head = 0;
/** Index of last element. Logically bigger than head. Usually points to an empty position, but points to the head when full
* (size == values.length). */
protected int tail = 0;
/** Number of elements in the queue. */
public int size = 0;
private transient QueueIterable iterable;
/** Creates a new Queue which can hold 16 values without needing to resize backing array. */
public Queue () {
this(16);
}
/** Creates a new Queue which can hold the specified number of values without needing to resize backing array. */
public Queue (int initialSize) {
// noinspection unchecked
this.values = (T[])new Object[initialSize];
}
/** Creates a new Queue which can hold the specified number of values without needing to resize backing array. This creates
* backing array of the specified type via reflection, which is necessary only when accessing the backing array directly. */
public Queue (int initialSize, Class type) {
// noinspection unchecked
this.values = (T[])ArrayReflection.newInstance(type, initialSize);
}
/** Append given object to the tail. (enqueue to tail) Unless backing array needs resizing, operates in O(1) time.
* @param object can be null */
public void addLast (@Null T object) {
T[] values = this.values;
if (size == values.length) {
resize(values.length << 1);// * 2
values = this.values;
}
values[tail++] = object;
if (tail == values.length) {
tail = 0;
}
size++;
}
/** Prepend given object to the head. (enqueue to head) Unless backing array needs resizing, operates in O(1) time.
* @see #addLast(Object)
* @param object can be null */
public void addFirst (@Null T object) {
T[] values = this.values;
if (size == values.length) {
resize(values.length << 1);// * 2
values = this.values;
}
int head = this.head;
head--;
if (head == -1) {
head = values.length - 1;
}
values[head] = object;
this.head = head;
this.size++;
}
/** Increases the size of the backing array to accommodate the specified number of additional items. Useful before adding many
* items to avoid multiple backing array resizes. */
public void ensureCapacity (int additional) {
final int needed = size + additional;
if (values.length < needed) {
resize(needed);
}
}
/** Resize backing array. newSize must be bigger than current size. */
protected void resize (int newSize) {
final T[] values = this.values;
final int head = this.head;
final int tail = this.tail;
final T[] newArray = (T[])ArrayReflection.newInstance(values.getClass().getComponentType(), newSize);
if (head < tail) {
// Continuous
System.arraycopy(values, head, newArray, 0, tail - head);
} else if (size > 0) {
// Wrapped
final int rest = values.length - head;
System.arraycopy(values, head, newArray, 0, rest);
System.arraycopy(values, 0, newArray, rest, tail);
}
this.values = newArray;
this.head = 0;
this.tail = size;
}
/** Remove the first item from the queue. (dequeue from head) Always O(1).
* @return removed object
* @throws NoSuchElementException when queue is empty */
public T removeFirst () {
if (size == 0) {
// Underflow
throw new NoSuchElementException("Queue is empty.");
}
final T[] values = this.values;
final T result = values[head];
values[head] = null;
head++;
if (head == values.length) {
head = 0;
}
size--;
return result;
}
/** Remove the last item from the queue. (dequeue from tail) Always O(1).
* @see #removeFirst()
* @return removed object
* @throws NoSuchElementException when queue is empty */
public T removeLast () {
if (size == 0) {
throw new NoSuchElementException("Queue is empty.");
}
final T[] values = this.values;
int tail = this.tail;
tail--;
if (tail == -1) {
tail = values.length - 1;
}
final T result = values[tail];
values[tail] = null;
this.tail = tail;
size--;
return result;
}
/** Returns the index of first occurrence of value in the queue, or -1 if no such value exists.
* @param identity If true, == comparison will be used. If false, .equals() comparison will be used.
* @return An index of first occurrence of value in queue or -1 if no such value exists */
public int indexOf (T value, boolean identity) {
if (size == 0) return -1;
T[] values = this.values;
final int head = this.head, tail = this.tail;
if (identity || value == null) {
if (head < tail) {
for (int i = head; i < tail; i++)
if (values[i] == value) return i - head;
} else {
for (int i = head, n = values.length; i < n; i++)
if (values[i] == value) return i - head;
for (int i = 0; i < tail; i++)
if (values[i] == value) return i + values.length - head;
}
} else {
if (head < tail) {
for (int i = head; i < tail; i++)
if (value.equals(values[i])) return i - head;
} else {
for (int i = head, n = values.length; i < n; i++)
if (value.equals(values[i])) return i - head;
for (int i = 0; i < tail; i++)
if (value.equals(values[i])) return i + values.length - head;
}
}
return -1;
}
/** Removes the first instance of the specified value in the queue.
* @param identity If true, == comparison will be used. If false, .equals() comparison will be used.
* @return true if value was found and removed, false otherwise */
public boolean removeValue (T value, boolean identity) {
int index = indexOf(value, identity);
if (index == -1) return false;
removeIndex(index);
return true;
}
/** Removes and returns the item at the specified index. */
public T removeIndex (int index) {
if (index < 0) throw new IndexOutOfBoundsException("index can't be < 0: " + index);
if (index >= size) throw new IndexOutOfBoundsException("index can't be >= size: " + index + " >= " + size);
T[] values = this.values;
int head = this.head, tail = this.tail;
index += head;
T value;
if (head < tail) { // index is between head and tail.
value = values[index];
System.arraycopy(values, index + 1, values, index, tail - index);
values[tail] = null;
this.tail--;
} else if (index >= values.length) { // index is between 0 and tail.
index -= values.length;
value = values[index];
System.arraycopy(values, index + 1, values, index, tail - index);
this.tail--;
} else { // index is between head and values.length.
value = values[index];
System.arraycopy(values, head, values, head + 1, index - head);
values[head] = null;
this.head++;
if (this.head == values.length) {
this.head = 0;
}
}
size--;
return value;
}
/** Returns true if the queue has one or more items. */
public boolean notEmpty () {
return size > 0;
}
/** Returns true if the queue is empty. */
public boolean isEmpty () {
return size == 0;
}
/** Returns the first (head) item in the queue (without removing it).
* @see #addFirst(Object)
* @see #removeFirst()
* @throws NoSuchElementException when queue is empty */
public T first () {
if (size == 0) {
// Underflow
throw new NoSuchElementException("Queue is empty.");
}
return values[head];
}
/** Returns the last (tail) item in the queue (without removing it).
* @see #addLast(Object)
* @see #removeLast()
* @throws NoSuchElementException when queue is empty */
public T last () {
if (size == 0) {
// Underflow
throw new NoSuchElementException("Queue is empty.");
}
final T[] values = this.values;
int tail = this.tail;
tail--;
if (tail == -1) {
tail = values.length - 1;
}
return values[tail];
}
/** Retrieves the value in queue without removing it. Indexing is from the front to back, zero based. Therefore get(0) is the
* same as {@link #first()}.
* @throws IndexOutOfBoundsException when the index is negative or >= size */
public T get (int index) {
if (index < 0) throw new IndexOutOfBoundsException("index can't be < 0: " + index);
if (index >= size) throw new IndexOutOfBoundsException("index can't be >= size: " + index + " >= " + size);
final T[] values = this.values;
int i = head + index;
if (i >= values.length) {
i -= values.length;
}
return values[i];
}
/** Removes all values from this queue. Values in backing array are set to null to prevent memory leak, so this operates in
* O(n). */
public void clear () {
if (size == 0) return;
final T[] values = this.values;
final int head = this.head;
final int tail = this.tail;
if (head < tail) {
// Continuous
for (int i = head; i < tail; i++) {
values[i] = null;
}
} else {
// Wrapped
for (int i = head; i < values.length; i++) {
values[i] = null;
}
for (int i = 0; i < tail; i++) {
values[i] = null;
}
}
this.head = 0;
this.tail = 0;
this.size = 0;
}
/** Returns an iterator for the items in the queue. Remove is supported.
*
* If {@link Collections#allocateIterators} is false, the same iterator instance is returned each time this method is called.
* Use the {@link QueueIterator} constructor for nested or multithreaded iteration. */
public Iterator iterator () {
if (Collections.allocateIterators) return new QueueIterator(this, true);
if (iterable == null) iterable = new QueueIterable(this);
return iterable.iterator();
}
public String toString () {
if (size == 0) {
return "[]";
}
final T[] values = this.values;
final int head = this.head;
final int tail = this.tail;
StringBuilder sb = new StringBuilder(64);
sb.append('[');
sb.append(values[head]);
for (int i = (head + 1) % values.length; i != tail; i = (i + 1) % values.length) {
sb.append(", ").append(values[i]);
}
sb.append(']');
return sb.toString();
}
public String toString (String separator) {
if (size == 0) return "";
final T[] values = this.values;
final int head = this.head;
final int tail = this.tail;
StringBuilder sb = new StringBuilder(64);
sb.append(values[head]);
for (int i = (head + 1) % values.length; i != tail; i = (i + 1) % values.length)
sb.append(separator).append(values[i]);
return sb.toString();
}
public int hashCode () {
final int size = this.size;
final T[] values = this.values;
final int backingLength = values.length;
int index = this.head;
int hash = size + 1;
for (int s = 0; s < size; s++) {
final T value = values[index];
hash *= 31;
if (value != null) hash += value.hashCode();
index++;
if (index == backingLength) index = 0;
}
return hash;
}
public boolean equals (Object o) {
if (this == o) return true;
if (o == null || !(o instanceof Queue)) return false;
Queue q = (Queue)o;
final int size = this.size;
if (q.size != size) return false;
final T[] myValues = this.values;
final int myBackingLength = myValues.length;
final Object[] itsValues = q.values;
final int itsBackingLength = itsValues.length;
int myIndex = head;
int itsIndex = q.head;
for (int s = 0; s < size; s++) {
T myValue = myValues[myIndex];
Object itsValue = itsValues[itsIndex];
if (!(myValue == null ? itsValue == null : myValue.equals(itsValue))) return false;
myIndex++;
itsIndex++;
if (myIndex == myBackingLength) myIndex = 0;
if (itsIndex == itsBackingLength) itsIndex = 0;
}
return true;
}
/** Uses == for comparison of each item. */
public boolean equalsIdentity (Object o) {
if (this == o) return true;
if (o == null || !(o instanceof Queue)) return false;
Queue q = (Queue)o;
final int size = this.size;
if (q.size != size) return false;
final T[] myValues = this.values;
final int myBackingLength = myValues.length;
final Object[] itsValues = q.values;
final int itsBackingLength = itsValues.length;
int myIndex = head;
int itsIndex = q.head;
for (int s = 0; s < size; s++) {
if (myValues[myIndex] != itsValues[itsIndex]) return false;
myIndex++;
itsIndex++;
if (myIndex == myBackingLength) myIndex = 0;
if (itsIndex == itsBackingLength) itsIndex = 0;
}
return true;
}
static public class QueueIterator implements Iterator, Iterable {
private final Queue queue;
private final boolean allowRemove;
int index;
boolean valid = true;
// QueueIterable iterable;
public QueueIterator (Queue queue) {
this(queue, true);
}
public QueueIterator (Queue queue, boolean allowRemove) {
this.queue = queue;
this.allowRemove = allowRemove;
}
public boolean hasNext () {
if (!valid) {
// System.out.println(iterable.lastAcquire);
throw new GdxRuntimeException("#iterator() cannot be used nested.");
}
return index < queue.size;
}
public T next () {
if (index >= queue.size) throw new NoSuchElementException(String.valueOf(index));
if (!valid) {
// System.out.println(iterable.lastAcquire);
throw new GdxRuntimeException("#iterator() cannot be used nested.");
}
return queue.get(index++);
}
public void remove () {
if (!allowRemove) throw new GdxRuntimeException("Remove not allowed.");
index--;
queue.removeIndex(index);
}
public void reset () {
index = 0;
}
public Iterator iterator () {
return this;
}
}
static public class QueueIterable implements Iterable {
private final Queue queue;
private final boolean allowRemove;
private QueueIterator iterator1, iterator2;
// java.io.StringWriter lastAcquire = new java.io.StringWriter();
public QueueIterable (Queue queue) {
this(queue, true);
}
public QueueIterable (Queue queue, boolean allowRemove) {
this.queue = queue;
this.allowRemove = allowRemove;
}
/** @see Collections#allocateIterators */
public Iterator iterator () {
if (Collections.allocateIterators) return new QueueIterator(queue, allowRemove);
// lastAcquire.getBuffer().setLength(0);
// new Throwable().printStackTrace(new java.io.PrintWriter(lastAcquire));
if (iterator1 == null) {
iterator1 = new QueueIterator(queue, allowRemove);
iterator2 = new QueueIterator(queue, allowRemove);
// iterator1.iterable = this;
// iterator2.iterable = this;
}
if (!iterator1.valid) {
iterator1.index = 0;
iterator1.valid = true;
iterator2.valid = false;
return iterator1;
}
iterator2.index = 0;
iterator2.valid = true;
iterator1.valid = false;
return iterator2;
}
}
}