src.it.unimi.dsi.fastutil.ints.IntArrayFIFOQueue Maven / Gradle / Ivy
/* Generic definitions */
/* Assertions (useful to generate conditional code) */
/* Current type and class (and size, if applicable) */
/* Value methods */
/* Interfaces (keys) */
/* Interfaces (values) */
/* Abstract implementations (keys) */
/* Abstract implementations (values) */
/* Static containers (keys) */
/* Static containers (values) */
/* Implementations */
/* Synchronized wrappers */
/* Unmodifiable wrappers */
/* Other wrappers */
/* Methods (keys) */
/* Methods (values) */
/* Methods (keys/values) */
/* Methods that have special names depending on keys (but the special names depend on values) */
/* Equality */
/* Object/Reference-only definitions (keys) */
/* Primitive-type-only definitions (keys) */
/* Object/Reference-only definitions (values) */
/*
* Copyright (C) 2010-2013 Sebastiano Vigna
*
* 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 it.unimi.dsi.fastutil.ints;
import java.io.Serializable;
import it.unimi.dsi.fastutil.Arrays;
import it.unimi.dsi.fastutil.HashCommon;
import java.util.NoSuchElementException;
/** A type-specific array-based FIFO queue, supporting also deque operations.
*
* Instances of this class represent a FIFO queue using a backing
* array in a circular way. The array is enlarged and shrunk as needed. You can use the {@link #trim()} method
* to reduce its memory usage, if necessary.
*
*
This class provides additional methods that implement a deque (double-ended queue).
*/
public class IntArrayFIFOQueue extends AbstractIntPriorityQueue implements Serializable {
private static final long serialVersionUID = 0L;
/** The standard initial capacity of a queue. */
public final static int INITIAL_CAPACITY = 4;
/** The backing array. */
@SuppressWarnings("unchecked")
protected transient int array[];
/** The current (cached) length of {@link #array}. */
protected transient int length;
/** The start position in {@link #array}. It is always strictly smaller than {@link #length}.*/
protected transient int start;
/** The end position in {@link #array}. It is always strictly smaller than {@link #length}.
* Might be actually smaller than {@link #start} because {@link #array} is used cyclically. */
protected transient int end;
/** Creates a new empty queue with given capacity.
*
* @param capacity the initial capacity of this queue.
*/
@SuppressWarnings("unchecked")
public IntArrayFIFOQueue( final int capacity ) {
if ( capacity < 0 ) throw new IllegalArgumentException( "Initial capacity (" + capacity + ") is negative" );
array = new int[ Math.max( 1, capacity ) ]; // Never build a queue with zero-sized backing array.
length = capacity;
}
/** Creates a new empty queue with standard {@linkplain #INITIAL_CAPACITY initial capacity}.
*/
public IntArrayFIFOQueue() {
this( INITIAL_CAPACITY );
}
/** Returns null (FIFO queues have no comparator).
* @return null.
*/
@Override
public IntComparator comparator() {
return null;
}
@Override
public int dequeueInt() {
if ( start == end ) throw new NoSuchElementException();
final int t = array[ start ];
if ( ++start == length ) start = 0;
reduce();
return t;
}
/** Dequeues the {@linkplain #last() last} element from the queue.
*
* @return the dequeued element.
* @throws NoSuchElementException if the queue is empty.
*/
public int dequeueLastInt() {
if ( start == end ) throw new NoSuchElementException();
if ( end == 0 ) end = length;
final int t = array[ --end ];
reduce();
return t;
}
@SuppressWarnings("unchecked")
private final void resize( final int size, final int newLength ) {
final int[] newArray = new int[ newLength ];
if ( start >= end ) {
if ( size != 0 ) {
System.arraycopy( array, start, newArray, 0, length - start );
System.arraycopy( array, 0, newArray, length - start, end );
}
}
else System.arraycopy( array, start, newArray, 0, end - start );
start = 0;
end = size;
array = newArray;
length = newLength;
}
private final void expand() {
resize( length, (int)Math.min( Arrays.MAX_ARRAY_SIZE, 2L * length ) );
}
private final void reduce() {
final int size = size();
if ( length > INITIAL_CAPACITY && size <= length / 4 ) resize( size, length / 2 );
}
@Override
public void enqueue( int x ) {
array[ end++ ] = x;
if ( end == length ) end = 0;
if ( end == start ) expand();
}
/** Enqueues a new element as the {@linkplain #first() first} element (in dequeuing order) of the queue.
*/
public void enqueueFirst( int x ) {
if ( start == 0 ) start = length;
array[ --start ] = x;
if ( end == start ) expand();
}
/** Returns the first element of the queue.
* @return the first element of the queue.
*/
public int firstInt() {
if ( start == end ) throw new NoSuchElementException();
return array[ start ];
}
/** Returns the last element of the queue.
* @return the last element of the queue.
*/
public int lastInt() {
if ( start == end ) throw new NoSuchElementException();
return array[ ( end == 0 ? length : end ) - 1 ];
}
@Override
public void clear() {
start = end = 0;
}
/** Trims the queue to the smallest possible size. */
@SuppressWarnings("unchecked")
public void trim() {
final int size = size();
final int[] newArray =
new int[ size + 1 ];
if ( start <= end ) System.arraycopy( array, start, newArray, 0, end - start );
else {
System.arraycopy( array, start, newArray, 0, length - start );
System.arraycopy( array, 0, newArray, length - start, end );
}
start = 0;
length = ( end = size ) + 1;
array = newArray;
}
@Override
public int size() {
final int apparentLength = end - start;
return apparentLength >= 0 ? apparentLength : length + apparentLength;
}
private void writeObject( java.io.ObjectOutputStream s ) throws java.io.IOException {
s.defaultWriteObject();
int size = size();
s.writeInt( size );
for( int i = start; size-- != 0; ) {
s.writeInt( array[ i++ ] );
if ( i == length ) i = 0;
}
}
@SuppressWarnings("unchecked")
private void readObject( java.io.ObjectInputStream s ) throws java.io.IOException, ClassNotFoundException {
s.defaultReadObject();
end = s.readInt();
array = new int[ length = HashCommon.nextPowerOfTwo( end + 1 ) ];
for( int i = 0; i < end; i++ ) array[ i ] = s.readInt();
}
}