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/*
* Copyright (C) 2002-2021 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.longs;
import java.util.Collection;
import java.util.Objects;
import java.util.function.Consumer;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.IntFunction;
import java.util.function.Supplier;
import it.unimi.dsi.fastutil.objects.ObjectArrays;
/**
* A class providing static methods and objects that do useful things with
* type-specific collections.
*
* @see java.util.Collections
*/
public final class LongCollections {
private LongCollections() {
}
/*
* Only in the EmptyCollection class, where performance is critical, do we
* override the deprecated, Object based functional methods. For the rest, we
* just override the non-deprecated type-specific method, and let the default
* method from the interface filter into that. This is an extra method call and
* lambda creation, but it isn't worth complexifying the code generation for a
* case that is already marked as being inefficient.
*/
/**
* An immutable class representing an empty type-specific collection.
*
*
* This class may be useful to implement your own in case you subclass a
* type-specific collection.
*/
public abstract static class EmptyCollection extends AbstractLongCollection {
protected EmptyCollection() {
}
@Override
public boolean contains(long k) {
return false;
}
@Override
public Object[] toArray() {
return ObjectArrays.EMPTY_ARRAY;
}
@Override
public T[] toArray(T[] array) {
if (array.length > 0)
array[0] = null;
return array;
}
@Override
public LongBidirectionalIterator iterator() {
return LongIterators.EMPTY_ITERATOR;
}
@Override
public LongSpliterator spliterator() {
return LongSpliterators.EMPTY_SPLITERATOR;
}
@Override
public int size() {
return 0;
}
@Override
public void clear() {
}
@Override
public int hashCode() {
return 0;
}
@Override
public boolean equals(Object o) {
if (o == this)
return true;
if (!(o instanceof Collection))
return false;
return ((Collection) o).isEmpty();
}
@Deprecated
@Override
public void forEach(final Consumer action) {
}
@Override
public boolean containsAll(final Collection c) {
return c.isEmpty();
}
@Override
public boolean addAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(final Collection c) {
throw new UnsupportedOperationException();
}
@Deprecated
@Override
public boolean removeIf(final java.util.function.Predicate filter) {
Objects.requireNonNull(filter);
return false;
}
@Override
public long[] toLongArray() {
return LongArrays.EMPTY_ARRAY;
}
/*
* {@inheritDoc}
*
* @deprecated Please use {@code toArray()} instead—this method is
* redundant and will be removed in the future.
*/
@Deprecated
@Override
public long[] toLongArray(long[] a) {
return a;
}
@Override
public void forEach(final java.util.function.LongConsumer action) {
}
@Override
public boolean containsAll(final LongCollection c) {
return c.isEmpty();
}
@Override
public boolean addAll(final LongCollection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(final LongCollection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(final LongCollection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeIf(final java.util.function.LongPredicate filter) {
Objects.requireNonNull(filter);
return false;
}
}
/** A synchronized wrapper class for collections. */
static class SynchronizedCollection implements LongCollection, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected final LongCollection collection;
protected final Object sync;
protected SynchronizedCollection(final LongCollection c, final Object sync) {
this.collection = Objects.requireNonNull(c);
this.sync = sync;
}
protected SynchronizedCollection(final LongCollection c) {
this.collection = Objects.requireNonNull(c);
this.sync = this;
}
@Override
public boolean add(final long k) {
synchronized (sync) {
return collection.add(k);
}
}
@Override
public boolean contains(final long k) {
synchronized (sync) {
return collection.contains(k);
}
}
@Override
public boolean rem(final long k) {
synchronized (sync) {
return collection.rem(k);
}
}
@Override
public int size() {
synchronized (sync) {
return collection.size();
}
}
@Override
public boolean isEmpty() {
synchronized (sync) {
return collection.isEmpty();
}
}
@Override
public long[] toLongArray() {
synchronized (sync) {
return collection.toLongArray();
}
}
@Override
public Object[] toArray() {
synchronized (sync) {
return collection.toArray();
}
}
/*
* {@inheritDoc}
*
* @deprecated Please use {@code toArray()} instead—this method is
* redundant and will be removed in the future.
*/
@Deprecated
@Override
public long[] toLongArray(final long[] a) {
return toArray(a);
}
@Override
public long[] toArray(final long[] a) {
synchronized (sync) {
return collection.toArray(a);
}
}
@Override
public boolean addAll(final LongCollection c) {
synchronized (sync) {
return collection.addAll(c);
}
}
@Override
public boolean containsAll(final LongCollection c) {
synchronized (sync) {
return collection.containsAll(c);
}
}
@Override
public boolean removeAll(final LongCollection c) {
synchronized (sync) {
return collection.removeAll(c);
}
}
@Override
public boolean retainAll(final LongCollection c) {
synchronized (sync) {
return collection.retainAll(c);
}
}
@Override
@Deprecated
public boolean add(final Long k) {
synchronized (sync) {
return collection.add(k);
}
}
@Override
@Deprecated
public boolean contains(final Object k) {
synchronized (sync) {
return collection.contains(k);
}
}
@Override
@Deprecated
public boolean remove(final Object k) {
synchronized (sync) {
return collection.remove(k);
}
}
@Override
public LongIterator longIterator() {
return collection.longIterator();
}
@Override
public LongSpliterator longSpliterator() {
return collection.longSpliterator();
}
@Override
public java.util.stream.LongStream longStream() {
return collection.longStream();
}
@Override
public java.util.stream.LongStream longParallelStream() {
return collection.longParallelStream();
}
@Override
public T[] toArray(final T[] a) {
synchronized (sync) {
return collection.toArray(a);
}
}
@Override
public LongIterator iterator() {
return collection.iterator();
}
@Override
public LongSpliterator spliterator() {
return collection.spliterator();
}
@Deprecated
@Override
public java.util.stream.Stream stream() {
return collection.stream();
}
@Deprecated
@Override
public java.util.stream.Stream parallelStream() {
return collection.parallelStream();
}
@Override
public void forEach(final java.util.function.LongConsumer action) {
synchronized (sync) {
collection.forEach(action);
}
}
@Override
public boolean addAll(final Collection c) {
synchronized (sync) {
return collection.addAll(c);
}
}
@Override
public boolean containsAll(final Collection c) {
synchronized (sync) {
return collection.containsAll(c);
}
}
@Override
public boolean removeAll(final Collection c) {
synchronized (sync) {
return collection.removeAll(c);
}
}
@Override
public boolean retainAll(final Collection c) {
synchronized (sync) {
return collection.retainAll(c);
}
}
@Override
public boolean removeIf(final java.util.function.LongPredicate filter) {
synchronized (sync) {
return collection.removeIf(filter);
}
}
@Override
public void clear() {
synchronized (sync) {
collection.clear();
}
}
@Override
public String toString() {
synchronized (sync) {
return collection.toString();
}
}
@Override
public int hashCode() {
synchronized (sync) {
return collection.hashCode();
}
}
@Override
public boolean equals(final Object o) {
if (o == this)
return true;
synchronized (sync) {
return collection.equals(o);
}
}
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
synchronized (sync) {
s.defaultWriteObject();
}
}
}
/**
* Returns a synchronized collection backed by the specified collection.
*
* @param c
* the collection to be wrapped in a synchronized collection.
* @return a synchronized view of the specified collection.
* @see java.util.Collections#synchronizedCollection(Collection)
*/
public static LongCollection synchronize(final LongCollection c) {
return new SynchronizedCollection(c);
}
/**
* Returns a synchronized collection backed by the specified collection, using
* an assigned object to synchronize.
*
* @param c
* the collection to be wrapped in a synchronized collection.
* @param sync
* an object that will be used to synchronize the list access.
* @return a synchronized view of the specified collection.
* @see java.util.Collections#synchronizedCollection(Collection)
*/
public static LongCollection synchronize(final LongCollection c, final Object sync) {
return new SynchronizedCollection(c, sync);
}
/** An unmodifiable wrapper class for collections. */
static class UnmodifiableCollection implements LongCollection, java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected final LongCollection collection;
protected UnmodifiableCollection(final LongCollection c) {
this.collection = Objects.requireNonNull(c);
}
@Override
public boolean add(final long k) {
throw new UnsupportedOperationException();
}
@Override
public boolean rem(final long k) {
throw new UnsupportedOperationException();
}
@Override
public int size() {
return collection.size();
}
@Override
public boolean isEmpty() {
return collection.isEmpty();
}
@Override
public boolean contains(final long o) {
return collection.contains(o);
}
@Override
public LongIterator iterator() {
return LongIterators.unmodifiable(collection.iterator());
}
@Override
public LongSpliterator spliterator() {
return collection.spliterator();
}
@Deprecated
@Override
public java.util.stream.Stream stream() {
return collection.stream();
}
@Deprecated
@Override
public java.util.stream.Stream parallelStream() {
return collection.parallelStream();
}
@Override
public void clear() {
throw new UnsupportedOperationException();
}
@Override
public T[] toArray(final T[] a) {
return collection.toArray(a);
}
@Override
public Object[] toArray() {
return collection.toArray();
}
@Override
public void forEach(final java.util.function.LongConsumer action) {
collection.forEach(action);
}
@Override
public boolean containsAll(Collection c) {
return collection.containsAll(c);
}
@Override
public boolean addAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeIf(final java.util.function.LongPredicate filter) {
throw new UnsupportedOperationException();
}
@Override
@Deprecated
public boolean add(final Long k) {
throw new UnsupportedOperationException();
}
@Override
@Deprecated
public boolean contains(final Object k) {
return collection.contains(k);
}
@Override
@Deprecated
public boolean remove(final Object k) {
throw new UnsupportedOperationException();
}
@Override
public long[] toLongArray() {
return collection.toLongArray();
}
/*
* {@inheritDoc}
*
* @deprecated Please use {@code toArray()} instead—this method is
* redundant.
*/
@Deprecated
@Override
public long[] toLongArray(final long[] a) {
return toArray(a);
}
@Override
public long[] toArray(final long[] a) {
return collection.toArray(a);
}
@Override
public boolean containsAll(LongCollection c) {
return collection.containsAll(c);
}
@Override
public boolean addAll(LongCollection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean removeAll(LongCollection c) {
throw new UnsupportedOperationException();
}
@Override
public boolean retainAll(LongCollection c) {
throw new UnsupportedOperationException();
}
@Override
public LongIterator longIterator() {
return collection.longIterator();
}
@Override
public LongSpliterator longSpliterator() {
return collection.longSpliterator();
}
@Override
public java.util.stream.LongStream longStream() {
return collection.longStream();
}
@Override
public java.util.stream.LongStream longParallelStream() {
return collection.longParallelStream();
}
@Override
public String toString() {
return collection.toString();
}
@Override
public int hashCode() {
return collection.hashCode();
}
@Override
public boolean equals(final Object o) {
if (o == this)
return true;
return collection.equals(o);
}
}
/**
* Returns an unmodifiable collection backed by the specified collection.
*
* @param c
* the collection to be wrapped in an unmodifiable collection.
* @return an unmodifiable view of the specified collection.
* @see java.util.Collections#unmodifiableCollection(Collection)
*/
public static LongCollection unmodifiable(final LongCollection c) {
return new UnmodifiableCollection(c);
}
/** A collection wrapper class for iterables. */
public static class IterableCollection extends AbstractLongCollection implements java.io.Serializable {
private static final long serialVersionUID = -7046029254386353129L;
protected final LongIterable iterable;
protected IterableCollection(final LongIterable iterable) {
this.iterable = Objects.requireNonNull(iterable);
}
@Override
public int size() {
long size = iterable.spliterator().getExactSizeIfKnown();
if (size >= 0)
return (int) Math.min(Integer.MAX_VALUE, size);
int c = 0;
final LongIterator iterator = iterator();
while (iterator.hasNext()) {
iterator.nextLong();
c++;
}
return c;
}
@Override
public boolean isEmpty() {
return !iterable.iterator().hasNext();
}
@Override
public LongIterator iterator() {
return iterable.iterator();
}
@Override
public LongSpliterator spliterator() {
return iterable.spliterator();
}
@Override
public LongIterator longIterator() {
return iterable.longIterator();
}
@Override
public LongSpliterator longSpliterator() {
return iterable.longSpliterator();
}
}
/**
* Returns an unmodifiable collection backed by the specified iterable.
*
* @param iterable
* the iterable object to be wrapped in an unmodifiable collection.
* @return an unmodifiable collection view of the specified iterable.
*/
public static LongCollection asCollection(final LongIterable iterable) {
if (iterable instanceof LongCollection)
return (LongCollection) iterable;
// TODO test for Collection but not our collection, and make a wrapper for it.
return new IterableCollection(iterable);
}
/**
* Helper class for size decreasing size estimation.
*
*
* Used to implement {@code toXWithExpectedSize} to prevent allocating a data
* structure big enough for the full stream in every thread, when only one
* thread (typically the first one) is going to need to "see" all of it at some
* point.
*
*
* Currently set to always assume a roughly split-by-two strategy from the
* {@link java.util.Spliterator} backing the {@link java.util.stream.Stream} (or
* primitive equivalent). This may perform worse for {@code Spliterator}s that
* don't (for example the ones that wrap an {@link java.util.Iterator} as a
* {@code Spliterator}). This is quite rare in practice however. But note that
* even in such cases, this would still perform no worse (modulo some
* trivial amount) then the default "flat size for every list" method of
* combining. A way to detect such cases and use a different size estimation
* strategy may come in the future.
*
*
* See the {@linkplain #SizeDecreasingSupplier constructor} for requirements of
* the {@link #builder} functor.
*/
static class SizeDecreasingSupplier implements Supplier {
static final int RECOMMENDED_MIN_SIZE = 8;
final AtomicInteger suppliedCount = new AtomicInteger(0);
final int expectedFinalSize;
final IntFunction builder;
/**
* Construct this {@link SizeDecreasingSupplier}.
*
* @param expectedFinalSize
* The expected size of the entire remaining contents of the
* {@code Stream} and thus what size the Collection holding the final
* results should try to be preallocated to.
* @param builder
* the builder function.
*
* The input integer will be the size of the collection to
* preallocate.
*
* It is recommended that you allocate a minimum size if the given
* {@code size} is small. {@link #RECOMMENDED_MIN_SIZE} gives a good
* enough ballpark for most cases.
*
* The subclass is free to use the default constructor for the
* Collection construction instead of the {@code size} given if
* {@code size} falls below the default size used for the default
* initial capacity for that Collection implementation. Often such
* default constructors contain additional optimizations that giving
* an explicit initial capacity would not do (even if given the
* default capacity as the initial capacity explicitly).
*
* {@link Supplier#get() get()} of the {@link IntFunction} must
* return non-{@code null}.
*/
SizeDecreasingSupplier(int expectedFinalSize, IntFunction builder) {
this.expectedFinalSize = expectedFinalSize;
this.builder = builder;
}
// This method may be worth pulling into a shared superclass.
@Override
public C get() {
// The "correct" splitting (assuming split by two) would be
// expectedFinalSize / floor(ln_2(++suppliedCount)). But that seems too much
// trouble to be worth it.
// Instead we will take a simple harmonically decreasing ratio (1, 1/2, 1/3,
// 1/4)
//
// Round up int math (to round up, not down) adapted from
// https://stackoverflow.com/a/503201.
int expectedNeededNextSize = 1 + ((expectedFinalSize - 1) / suppliedCount.incrementAndGet());
if (expectedNeededNextSize < 0) {
// Overflow (and weird below zero results) failsafe
expectedNeededNextSize = RECOMMENDED_MIN_SIZE;
}
return builder.apply(expectedNeededNextSize);
}
}
}