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/*
* 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 com.google.common.annotations.GwtCompatible;
import java.util.Comparator;
import java.util.Spliterator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.function.IntConsumer;
import java.util.function.IntFunction;
import java.util.function.Predicate;
import java.util.stream.IntStream;
import org.checkerframework.checker.nullness.qual.Nullable;
/** Spliterator utilities for {@code common.collect} internals. */
@GwtCompatible
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,
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
public @Nullable 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
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
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 {
T holder = null;
@Override
public void accept(T t) {
this.holder = t;
}
@Override
public boolean tryAdvance(Consumer action) {
while (fromSpliterator.tryAdvance(this)) {
try {
if (predicate.test(holder)) {
action.accept(holder);
return true;
}
} finally {
holder = null;
}
}
return false;
}
@Override
public Spliterator trySplit() {
Spliterator fromSplit = fromSpliterator.trySplit();
return (fromSplit == null) ? null : filter(fromSplit, predicate);
}
@Override
public long estimateSize() {
return fromSpliterator.estimateSize() / 2;
}
@Override
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);
class FlatMapSpliterator implements Spliterator {
@Nullable Spliterator prefix;
final Spliterator from;
int characteristics;
long estimatedSize;
FlatMapSpliterator(
Spliterator prefix, Spliterator from, int characteristics, long estimatedSize) {
this.prefix = prefix;
this.from = from;
this.characteristics = characteristics;
this.estimatedSize = estimatedSize;
}
@Override
public 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 void forEachRemaining(Consumer action) {
if (prefix != null) {
prefix.forEachRemaining(action);
prefix = null;
}
from.forEachRemaining(fromElement -> function.apply(fromElement).forEachRemaining(action));
estimatedSize = 0;
}
@Override
public Spliterator 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;
}
Spliterator result =
new FlatMapSpliterator(this.prefix, fromSplit, splitCharacteristics, estSplitSize);
this.prefix = null;
return result;
} else if (prefix != null) {
Spliterator result = prefix;
this.prefix = null;
return result;
} else {
return null;
}
}
@Override
public long estimateSize() {
if (prefix != null) {
estimatedSize = Math.max(estimatedSize, prefix.estimateSize());
}
return Math.max(estimatedSize, 0);
}
@Override
public int characteristics() {
return characteristics;
}
}
return new FlatMapSpliterator(null, fromSpliterator, topCharacteristics, topSize);
}
}