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/*
* Copyright (C) 2003-2021 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;
import java.util.Comparator;
import java.util.NoSuchElementException;
/** A class providing static methods and objects that do useful things with indirect priority queues.
*
* @see IndirectPriorityQueue
*/
public class IndirectPriorityQueues {
private IndirectPriorityQueues() {}
/** An immutable class representing the empty indirect priority queue.
*
* This class may be useful to implement your own in case you subclass
* {@link IndirectPriorityQueue}.
*/
@SuppressWarnings("rawtypes")
public static class EmptyIndirectPriorityQueue implements IndirectPriorityQueue {
protected EmptyIndirectPriorityQueue() {}
@Override
public void enqueue(final int i) { throw new UnsupportedOperationException(); }
@Override
public int dequeue() { throw new NoSuchElementException(); }
@Override
public boolean isEmpty() { return true; }
@Override
public int size() { return 0; }
@Override
public boolean contains(final int index) { return false; }
@Override
public void clear() {}
@Override
public int first() { throw new NoSuchElementException(); }
@Override
public int last() { throw new NoSuchElementException(); }
@Override
public void changed() { throw new NoSuchElementException(); }
@Override
public void allChanged() {}
@Override
public Comparator comparator() { return null; }
@Override
public void changed(final int i) { throw new IllegalArgumentException("Index " + i + " is not in the queue"); }
@Override
public boolean remove(final int i) { return false; }
@Override
public int front(final int[] a) { return 0; }
}
/** An empty indirect priority queue (immutable).
*/
public static final EmptyIndirectPriorityQueue EMPTY_QUEUE = new EmptyIndirectPriorityQueue();
/** A synchronized wrapper class for indirect priority queues. */
public static class SynchronizedIndirectPriorityQueue implements IndirectPriorityQueue {
public static final long serialVersionUID = -7046029254386353129L;
protected final IndirectPriorityQueue q;
protected final Object sync;
protected SynchronizedIndirectPriorityQueue(final IndirectPriorityQueue q, final Object sync) {
this.q = q;
this.sync = sync;
}
protected SynchronizedIndirectPriorityQueue(final IndirectPriorityQueue q) {
this.q = q;
this.sync = this;
}
@Override
public void enqueue(final int x) { synchronized(sync) { q.enqueue(x); } }
@Override
public int dequeue() { synchronized(sync) { return q.dequeue(); } }
@Override
public boolean contains(final int index) { synchronized(sync) { return q.contains(index); } }
@Override
public int first() { synchronized(sync) { return q.first(); } }
@Override
public int last() { synchronized(sync) { return q.last(); } }
@Override
public boolean isEmpty() { synchronized(sync) { return q.isEmpty(); } }
@Override
public int size() { synchronized(sync) { return q.size(); } }
@Override
public void clear() { synchronized(sync) { q.clear(); } }
@Override
public void changed() { synchronized(sync) { q.changed(); } }
@Override
public void allChanged() { synchronized(sync) { q.allChanged(); } }
@Override
public void changed(final int i) { synchronized(sync) { q.changed(i); } }
@Override
public boolean remove(final int i) { synchronized(sync) { return q.remove(i); } }
@Override
public Comparator comparator() { synchronized(sync) { return q.comparator(); } }
@Override
public int front(final int[] a) { return q.front(a); }
}
/** Returns a synchronized type-specific indirect priority queue backed by the specified type-specific indirect priority queue.
*
* @param q the indirect priority queue to be wrapped in a synchronized indirect priority queue.
* @return a synchronized view of the specified indirect priority queue.
*/
public static IndirectPriorityQueue synchronize(final IndirectPriorityQueue q) { return new SynchronizedIndirectPriorityQueue<>(q); }
/** Returns a synchronized type-specific indirect priority queue backed by the specified type-specific indirect priority queue, using an assigned object to synchronize.
*
* @param q the indirect priority queue to be wrapped in a synchronized indirect priority queue.
* @param sync an object that will be used to synchronize the access to the indirect priority queue.
* @return a synchronized view of the specified indirect priority queue.
*/
public static IndirectPriorityQueue synchronize(final IndirectPriorityQueue q, final Object sync) { return new SynchronizedIndirectPriorityQueue<>(q, sync); }
}