/*
* 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.IntFunction;
import java.util.function.Predicate;
import java.util.stream.IntStream;
import javax.annotation.Nullable;
/**
* Spliterator utilities for {@code common.collect} internals.
*/
@GwtCompatible
final class CollectSpliterators {
private CollectSpliterators() {}
static <T> Spliterator<T> indexed(int size, int extraCharacteristics, IntFunction<T> function) {
return indexed(size, extraCharacteristics, function, null);
}
static <T> Spliterator<T> indexed(
int size,
int extraCharacteristics,
IntFunction<T> function,
Comparator<? super T> comparator) {
if (comparator != null) {
checkArgument((extraCharacteristics & (Spliterator.SORTED)) != 0);
}
class WithCharacteristics implements Spliterator<T> {
private final Spliterator<T> delegate;
WithCharacteristics(Spliterator<T> delegate) {
this.delegate = delegate;
}
@Override
public boolean tryAdvance(Consumer<? super T> action) {
return delegate.tryAdvance(action);
}
@Override
public void forEachRemaining(Consumer<? super T> action) {
delegate.forEachRemaining(action);
}
@Override
@Nullable
public Spliterator<T> trySplit() {
Spliterator<T> split = delegate.trySplit();
return (split == null) ? null : new WithCharacteristics(split);
}
@Override
public long estimateSize() {
return delegate.estimateSize();
}
@Override
public int characteristics() {
return delegate.characteristics() | extraCharacteristics;
}
@Override
public Comparator<? super T> getComparator() {
if (hasCharacteristics(Spliterator.SORTED)) {
return comparator;
} else {
throw new IllegalStateException();
}
}
}
return new WithCharacteristics(IntStream.range(0, size).mapToObj(function).spliterator());
}
/**
* Returns a {@code Spliterator} over the elements of {@code fromSpliterator} mapped by {@code
* function}.
*/
static <F, T> Spliterator<T> map(
Spliterator<F> fromSpliterator, Function<? super F, ? extends T> function) {
checkNotNull(fromSpliterator);
checkNotNull(function);
return new Spliterator<T>() {
@Override
public boolean tryAdvance(Consumer<? super T> action) {
return fromSpliterator.tryAdvance(
fromElement -> action.accept(function.apply(fromElement)));
}
@Override
public void forEachRemaining(Consumer<? super T> action) {
fromSpliterator.forEachRemaining(fromElement -> action.accept(function.apply(fromElement)));
}
@Override
public Spliterator<T> trySplit() {
Spliterator<F> 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 <T> Spliterator<T> filter(Spliterator<T> fromSpliterator, Predicate<? super T> predicate) {
checkNotNull(fromSpliterator);
checkNotNull(predicate);
class Splitr implements Spliterator<T>, Consumer<T> {
T holder = null;
@Override
public void accept(T t) {
this.holder = t;
}
@Override
public boolean tryAdvance(Consumer<? super T> action) {
while (fromSpliterator.tryAdvance(this)) {
try {
if (predicate.test(holder)) {
action.accept(holder);
return true;
}
} finally {
holder = null;
}
}
return false;
}
@Override
public Spliterator<T> trySplit() {
Spliterator<T> fromSplit = fromSpliterator.trySplit();
return (fromSplit == null) ? null : filter(fromSplit, predicate);
}
@Override
public long estimateSize() {
return fromSpliterator.estimateSize() / 2;
}
@Override
public Comparator<? super T> 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 <F, T> Spliterator<T> flatMap(
Spliterator<F> fromSpliterator,
Function<? super F, Spliterator<T>> 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<T> {
@Nullable Spliterator<T> prefix;
final Spliterator<F> from;
int characteristics;
long estimatedSize;
FlatMapSpliterator(
Spliterator<T> prefix, Spliterator<F> from, int characteristics, long estimatedSize) {
this.prefix = prefix;
this.from = from;
this.characteristics = characteristics;
this.estimatedSize = estimatedSize;
}
@Override
public boolean tryAdvance(Consumer<? super T> 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<? super T> action) {
if (prefix != null) {
prefix.forEachRemaining(action);
prefix = null;
}
from.forEachRemaining(fromElement -> function.apply(fromElement).forEachRemaining(action));
estimatedSize = 0;
}
@Override
public Spliterator<T> trySplit() {
Spliterator<F> 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<T> result =
new FlatMapSpliterator(this.prefix, fromSplit, splitCharacteristics, estSplitSize);
this.prefix = null;
return result;
} else if (prefix != null) {
Spliterator<T> 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);
}
}