com.google.common.collect.CollectSpliterators Maven / Gradle / Ivy
/*
* Copyright (C) 2015 The Guava Authors
*
* 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.google.common.collect;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.NullnessCasts.uncheckedCastNullableTToT;
import static java.lang.Math.max;
import com.google.common.annotations.GwtCompatible;
import com.google.j2objc.annotations.Weak;
import java.util.Comparator;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.DoubleConsumer;
import java.util.function.Function;
import java.util.function.IntConsumer;
import java.util.function.IntFunction;
import java.util.function.LongConsumer;
import java.util.function.Predicate;
import java.util.stream.IntStream;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;
/** Spliterator utilities for {@code common.collect} internals. */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class CollectSpliterators {
private CollectSpliterators() {}
static Spliterator indexed(
int size, int extraCharacteristics, IntFunction function) {
return indexed(size, extraCharacteristics, function, null);
}
static Spliterator indexed(
int size,
int extraCharacteristics,
IntFunction function,
@CheckForNull Comparator comparator) {
if (comparator != null) {
checkArgument((extraCharacteristics & Spliterator.SORTED) != 0);
}
class WithCharacteristics implements Spliterator {
private final Spliterator.OfInt delegate;
WithCharacteristics(Spliterator.OfInt delegate) {
this.delegate = delegate;
}
@Override
public boolean tryAdvance(Consumer action) {
return delegate.tryAdvance((IntConsumer) i -> action.accept(function.apply(i)));
}
@Override
public void forEachRemaining(Consumer action) {
delegate.forEachRemaining((IntConsumer) i -> action.accept(function.apply(i)));
}
@Override
@CheckForNull
public Spliterator trySplit() {
Spliterator.OfInt split = delegate.trySplit();
return (split == null) ? null : new WithCharacteristics(split);
}
@Override
public long estimateSize() {
return delegate.estimateSize();
}
@Override
public int characteristics() {
return Spliterator.ORDERED
| Spliterator.SIZED
| Spliterator.SUBSIZED
| extraCharacteristics;
}
@Override
@CheckForNull
public Comparator getComparator() {
if (hasCharacteristics(Spliterator.SORTED)) {
return comparator;
} else {
throw new IllegalStateException();
}
}
}
return new WithCharacteristics(IntStream.range(0, size).spliterator());
}
/**
* Returns a {@code Spliterator} over the elements of {@code fromSpliterator} mapped by {@code
* function}.
*/
static
Spliterator map(
Spliterator fromSpliterator,
Function function) {
checkNotNull(fromSpliterator);
checkNotNull(function);
return new Spliterator() {
@Override
public boolean tryAdvance(Consumer action) {
return fromSpliterator.tryAdvance(
fromElement -> action.accept(function.apply(fromElement)));
}
@Override
public void forEachRemaining(Consumer action) {
fromSpliterator.forEachRemaining(fromElement -> action.accept(function.apply(fromElement)));
}
@Override
@CheckForNull
public Spliterator trySplit() {
Spliterator fromSplit = fromSpliterator.trySplit();
return (fromSplit != null) ? map(fromSplit, function) : null;
}
@Override
public long estimateSize() {
return fromSpliterator.estimateSize();
}
@Override
public int characteristics() {
return fromSpliterator.characteristics()
& ~(Spliterator.DISTINCT | Spliterator.NONNULL | Spliterator.SORTED);
}
};
}
/** Returns a {@code Spliterator} filtered by the specified predicate. */
static Spliterator filter(
Spliterator fromSpliterator, Predicate predicate) {
checkNotNull(fromSpliterator);
checkNotNull(predicate);
class Splitr implements Spliterator, Consumer {
@CheckForNull T holder = null;
@Override
public void accept(@ParametricNullness T t) {
this.holder = t;
}
@Override
public boolean tryAdvance(Consumer action) {
while (fromSpliterator.tryAdvance(this)) {
try {
// The cast is safe because tryAdvance puts a T into `holder`.
T next = uncheckedCastNullableTToT(holder);
if (predicate.test(next)) {
action.accept(next);
return true;
}
} finally {
holder = null;
}
}
return false;
}
@Override
@CheckForNull
public Spliterator trySplit() {
Spliterator fromSplit = fromSpliterator.trySplit();
return (fromSplit == null) ? null : filter(fromSplit, predicate);
}
@Override
public long estimateSize() {
return fromSpliterator.estimateSize() / 2;
}
@Override
@CheckForNull
public Comparator getComparator() {
return fromSpliterator.getComparator();
}
@Override
public int characteristics() {
return fromSpliterator.characteristics()
& (Spliterator.DISTINCT
| Spliterator.NONNULL
| Spliterator.ORDERED
| Spliterator.SORTED);
}
}
return new Splitr();
}
/**
* Returns a {@code Spliterator} that iterates over the elements of the spliterators generated by
* applying {@code function} to the elements of {@code fromSpliterator}.
*/
static
Spliterator flatMap(
Spliterator fromSpliterator,
Function> function,
int topCharacteristics,
long topSize) {
checkArgument(
(topCharacteristics & Spliterator.SUBSIZED) == 0,
"flatMap does not support SUBSIZED characteristic");
checkArgument(
(topCharacteristics & Spliterator.SORTED) == 0,
"flatMap does not support SORTED characteristic");
checkNotNull(fromSpliterator);
checkNotNull(function);
return new FlatMapSpliteratorOfObject<>(
null, fromSpliterator, function, topCharacteristics, topSize);
}
/**
* Returns a {@code Spliterator.OfInt} that iterates over the elements of the spliterators
* generated by applying {@code function} to the elements of {@code fromSpliterator}. (If {@code
* function} returns {@code null} for an input, it is replaced with an empty stream.)
*/
static Spliterator.OfInt flatMapToInt(
Spliterator fromSpliterator,
Function function,
int topCharacteristics,
long topSize) {
checkArgument(
(topCharacteristics & Spliterator.SUBSIZED) == 0,
"flatMap does not support SUBSIZED characteristic");
checkArgument(
(topCharacteristics & Spliterator.SORTED) == 0,
"flatMap does not support SORTED characteristic");
checkNotNull(fromSpliterator);
checkNotNull(function);
return new FlatMapSpliteratorOfInt<>(
null, fromSpliterator, function, topCharacteristics, topSize);
}
/**
* Returns a {@code Spliterator.OfLong} that iterates over the elements of the spliterators
* generated by applying {@code function} to the elements of {@code fromSpliterator}. (If {@code
* function} returns {@code null} for an input, it is replaced with an empty stream.)
*/
static Spliterator.OfLong flatMapToLong(
Spliterator fromSpliterator,
Function function,
int topCharacteristics,
long topSize) {
checkArgument(
(topCharacteristics & Spliterator.SUBSIZED) == 0,
"flatMap does not support SUBSIZED characteristic");
checkArgument(
(topCharacteristics & Spliterator.SORTED) == 0,
"flatMap does not support SORTED characteristic");
checkNotNull(fromSpliterator);
checkNotNull(function);
return new FlatMapSpliteratorOfLong<>(
null, fromSpliterator, function, topCharacteristics, topSize);
}
/**
* Returns a {@code Spliterator.OfDouble} that iterates over the elements of the spliterators
* generated by applying {@code function} to the elements of {@code fromSpliterator}. (If {@code
* function} returns {@code null} for an input, it is replaced with an empty stream.)
*/
static Spliterator.OfDouble flatMapToDouble(
Spliterator fromSpliterator,
Function function,
int topCharacteristics,
long topSize) {
checkArgument(
(topCharacteristics & Spliterator.SUBSIZED) == 0,
"flatMap does not support SUBSIZED characteristic");
checkArgument(
(topCharacteristics & Spliterator.SORTED) == 0,
"flatMap does not support SORTED characteristic");
checkNotNull(fromSpliterator);
checkNotNull(function);
return new FlatMapSpliteratorOfDouble<>(
null, fromSpliterator, function, topCharacteristics, topSize);
}
/**
* Implements the {@link Stream#flatMap} operation on spliterators.
*
* @param the element type of the input spliterator
* @param the element type of the output spliterators
* @param the type of the output spliterators
*/
abstract static class FlatMapSpliterator<
InElementT extends @Nullable Object,
OutElementT extends @Nullable Object,
OutSpliteratorT extends Spliterator>
implements Spliterator {
/** Factory for constructing {@link FlatMapSpliterator} instances. */
@FunctionalInterface
interface Factory> {
OutSpliteratorT newFlatMapSpliterator(
@CheckForNull OutSpliteratorT prefix,
Spliterator fromSplit,
Function function,
int splitCharacteristics,
long estSplitSize);
}
@Weak @CheckForNull OutSpliteratorT prefix;
final Spliterator from;
final Function function;
final Factory factory;
int characteristics;
long estimatedSize;
FlatMapSpliterator(
@CheckForNull OutSpliteratorT prefix,
Spliterator from,
Function function,
Factory factory,
int characteristics,
long estimatedSize) {
this.prefix = prefix;
this.from = from;
this.function = function;
this.factory = factory;
this.characteristics = characteristics;
this.estimatedSize = estimatedSize;
}
/*
* The tryAdvance and forEachRemaining in FlatMapSpliteratorOfPrimitive are overloads of these
* methods, not overrides. They are annotated @Override because they implement methods from
* Spliterator.OfPrimitive (and override default implementations from Spliterator.OfPrimitive or
* a subtype like Spliterator.OfInt).
*/
@Override
public final boolean tryAdvance(Consumer action) {
while (true) {
if (prefix != null && prefix.tryAdvance(action)) {
if (estimatedSize != Long.MAX_VALUE) {
estimatedSize--;
}
return true;
} else {
prefix = null;
}
if (!from.tryAdvance(fromElement -> prefix = function.apply(fromElement))) {
return false;
}
}
}
@Override
public final void forEachRemaining(Consumer action) {
if (prefix != null) {
prefix.forEachRemaining(action);
prefix = null;
}
from.forEachRemaining(
fromElement -> {
Spliterator elements = function.apply(fromElement);
if (elements != null) {
elements.forEachRemaining(action);
}
});
estimatedSize = 0;
}
@Override
@CheckForNull
public final OutSpliteratorT trySplit() {
Spliterator fromSplit = from.trySplit();
if (fromSplit != null) {
int splitCharacteristics = characteristics & ~Spliterator.SIZED;
long estSplitSize = estimateSize();
if (estSplitSize < Long.MAX_VALUE) {
estSplitSize /= 2;
this.estimatedSize -= estSplitSize;
this.characteristics = splitCharacteristics;
}
OutSpliteratorT result =
factory.newFlatMapSpliterator(
this.prefix, fromSplit, function, splitCharacteristics, estSplitSize);
this.prefix = null;
return result;
} else if (prefix != null) {
OutSpliteratorT result = prefix;
this.prefix = null;
return result;
} else {
return null;
}
}
@Override
public final long estimateSize() {
if (prefix != null) {
estimatedSize = max(estimatedSize, prefix.estimateSize());
}
return max(estimatedSize, 0);
}
@Override
public final int characteristics() {
return characteristics;
}
}
/**
* Implementation of {@link Stream#flatMap} with an object spliterator output type.
*
* To avoid having this type, we could use {@code FlatMapSpliterator} directly. The main
* advantages to having the type are the ability to use its constructor reference below and the
* parallelism with the primitive version. In short, it makes its caller ({@code flatMap})
* simpler.
*
* @param the element type of the input spliterator
* @param the element type of the output spliterators
*/
static final class FlatMapSpliteratorOfObject<
InElementT extends @Nullable Object, OutElementT extends @Nullable Object>
extends FlatMapSpliterator> {
FlatMapSpliteratorOfObject(
@CheckForNull Spliterator prefix,
Spliterator from,
Function> function,
int characteristics,
long estimatedSize) {
super(
prefix, from, function, FlatMapSpliteratorOfObject::new, characteristics, estimatedSize);
}
}
/**
* Implementation of {@link Stream#flatMap} with a primitive spliterator output type.
*
* @param the element type of the input spliterator
* @param the (boxed) element type of the output spliterators
* @param the specialized consumer type for the primitive output type
* @param the primitive spliterator type associated with {@code OutElementT}
*/
abstract static class FlatMapSpliteratorOfPrimitive<
InElementT extends @Nullable Object,
OutElementT extends @Nullable Object,
OutConsumerT,
OutSpliteratorT extends
Spliterator.OfPrimitive>
extends FlatMapSpliterator
implements Spliterator.OfPrimitive {
FlatMapSpliteratorOfPrimitive(
@CheckForNull OutSpliteratorT prefix,
Spliterator from,
Function function,
Factory factory,
int characteristics,
long estimatedSize) {
super(prefix, from, function, factory, characteristics, estimatedSize);
}
@Override
public final boolean tryAdvance(OutConsumerT action) {
while (true) {
if (prefix != null && prefix.tryAdvance(action)) {
if (estimatedSize != Long.MAX_VALUE) {
estimatedSize--;
}
return true;
} else {
prefix = null;
}
if (!from.tryAdvance(fromElement -> prefix = function.apply(fromElement))) {
return false;
}
}
}
@Override
public final void forEachRemaining(OutConsumerT action) {
if (prefix != null) {
prefix.forEachRemaining(action);
prefix = null;
}
from.forEachRemaining(
fromElement -> {
OutSpliteratorT elements = function.apply(fromElement);
if (elements != null) {
elements.forEachRemaining(action);
}
});
estimatedSize = 0;
}
}
/** Implementation of {@link #flatMapToInt}. */
static final class FlatMapSpliteratorOfInt
extends FlatMapSpliteratorOfPrimitive
implements Spliterator.OfInt {
FlatMapSpliteratorOfInt(
@CheckForNull Spliterator.OfInt prefix,
Spliterator from,
Function function,
int characteristics,
long estimatedSize) {
super(prefix, from, function, FlatMapSpliteratorOfInt::new, characteristics, estimatedSize);
}
}
/** Implementation of {@link #flatMapToLong}. */
static final class FlatMapSpliteratorOfLong
extends FlatMapSpliteratorOfPrimitive
implements Spliterator.OfLong {
FlatMapSpliteratorOfLong(
@CheckForNull Spliterator.OfLong prefix,
Spliterator from,
Function function,
int characteristics,
long estimatedSize) {
super(prefix, from, function, FlatMapSpliteratorOfLong::new, characteristics, estimatedSize);
}
}
/** Implementation of {@link #flatMapToDouble}. */
static final class FlatMapSpliteratorOfDouble
extends FlatMapSpliteratorOfPrimitive<
InElementT, Double, DoubleConsumer, Spliterator.OfDouble>
implements Spliterator.OfDouble {
FlatMapSpliteratorOfDouble(
@CheckForNull Spliterator.OfDouble prefix,
Spliterator from,
Function function,
int characteristics,
long estimatedSize) {
super(
prefix, from, function, FlatMapSpliteratorOfDouble::new, characteristics, estimatedSize);
}
}
}