/*
* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package java.util.stream;
import java.util.Objects;
import java.util.Optional;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.OptionalLong;
import java.util.Spliterator;
import java.util.concurrent.CountedCompleter;
import java.util.function.BiConsumer;
import java.util.function.BiFunction;
import java.util.function.BinaryOperator;
import java.util.function.DoubleBinaryOperator;
import java.util.function.IntBinaryOperator;
import java.util.function.LongBinaryOperator;
import java.util.function.ObjDoubleConsumer;
import java.util.function.ObjIntConsumer;
import java.util.function.ObjLongConsumer;
import java.util.function.Supplier;
/**
* Factory for creating instances of {@code TerminalOp} that implement
* reductions.
*
* @since 1.8
*/
final class ReduceOps {
private ReduceOps() { }
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* reference values.
*
* @param <T> the type of the input elements
* @param <U> the type of the result
* @param seed the identity element for the reduction
* @param reducer the accumulating function that incorporates an additional
* input element into the result
* @param combiner the combining function that combines two intermediate
* results
* @return a {@code TerminalOp} implementing the reduction
*/
public static <T, U> TerminalOp<T, U>
makeRef(U seed, BiFunction<U, ? super T, U> reducer, BinaryOperator<U> combiner) {
Objects.requireNonNull(reducer);
Objects.requireNonNull(combiner);
class ReducingSink extends Box<U> implements AccumulatingSink<T, U, ReducingSink> {
@Override
public void begin(long size) {
state = seed;
}
@Override
public void accept(T t) {
state = reducer.apply(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp<T, U, ReducingSink>(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* reference values producing an optional reference result.
*
* @param <T> The type of the input elements, and the type of the result
* @param operator The reducing function
* @return A {@code TerminalOp} implementing the reduction
*/
public static <T> TerminalOp<T, Optional<T>>
makeRef(BinaryOperator<T> operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<T, Optional<T>, ReducingSink> {
private boolean empty;
private T state;
public void begin(long size) {
empty = true;
state = null;
}
@Override
public void accept(T t) {
if (empty) {
empty = false;
state = t;
} else {
state = operator.apply(state, t);
}
}
@Override
public Optional<T> get() {
return empty ? Optional.empty() : Optional.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp<T, Optional<T>, ReducingSink>(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* reference values.
*
* @param <T> the type of the input elements
* @param <I> the type of the intermediate reduction result
* @param collector a {@code Collector} defining the reduction
* @return a {@code ReduceOp} implementing the reduction
*/
public static <T, I> TerminalOp<T, I>
makeRef(Collector<? super T, I, ?> collector) {
Supplier<I> supplier = Objects.requireNonNull(collector).supplier();
BiConsumer<I, ? super T> accumulator = collector.accumulator();
BinaryOperator<I> combiner = collector.combiner();
class ReducingSink extends Box<I>
implements AccumulatingSink<T, I, ReducingSink> {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(T t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp<T, I, ReducingSink>(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
@Override
public int getOpFlags() {
return collector.characteristics().contains(Collector.Characteristics.UNORDERED)
? StreamOpFlag.NOT_ORDERED
: 0;
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* reference values.
*
* @param <T> the type of the input elements
* @param <R> the type of the result
* @param seedFactory a factory to produce a new base accumulator
* @param accumulator a function to incorporate an element into an
* accumulator
* @param reducer a function to combine an accumulator into another
* @return a {@code TerminalOp} implementing the reduction
*/
public static <T, R> TerminalOp<T, R>
makeRef(Supplier<R> seedFactory,
BiConsumer<R, ? super T> accumulator,
BiConsumer<R,R> reducer) {
Objects.requireNonNull(seedFactory);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(reducer);
class ReducingSink extends Box<R>
implements AccumulatingSink<T, R, ReducingSink> {
@Override
public void begin(long size) {
state = seedFactory.get();
}
@Override
public void accept(T t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
reducer.accept(state, other.state);
}
}
return new ReduceOp<T, R, ReducingSink>(StreamShape.REFERENCE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code int} values.
*
* @param identity the identity for the combining function
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp<Integer, Integer>
makeInt(int identity, IntBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<Integer, Integer, ReducingSink>, Sink.OfInt {
private int state;
@Override
public void begin(long size) {
state = identity;
}
@Override
public void accept(int t) {
state = operator.applyAsInt(state, t);
}
@Override
public Integer get() {
return state;
}
@Override
public void combine(ReducingSink other) {
accept(other.state);
}
}
return new ReduceOp<Integer, Integer, ReducingSink>(StreamShape.INT_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code int} values, producing an optional integer result.
*
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp<Integer, OptionalInt>
makeInt(IntBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<Integer, OptionalInt, ReducingSink>, Sink.OfInt {
private boolean empty;
private int state;
public void begin(long size) {
empty = true;
state = 0;
}
@Override
public void accept(int t) {
if (empty) {
empty = false;
state = t;
}
else {
state = operator.applyAsInt(state, t);
}
}
@Override
public OptionalInt get() {
return empty ? OptionalInt.empty() : OptionalInt.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp<Integer, OptionalInt, ReducingSink>(StreamShape.INT_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* {@code int} values.
*
* @param <R> The type of the result
* @param supplier a factory to produce a new accumulator of the result type
* @param accumulator a function to incorporate an int into an
* accumulator
* @param combiner a function to combine an accumulator into another
* @return A {@code ReduceOp} implementing the reduction
*/
public static <R> TerminalOp<Integer, R>
makeInt(Supplier<R> supplier,
ObjIntConsumer<R> accumulator,
BinaryOperator<R> combiner) {
Objects.requireNonNull(supplier);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(combiner);
class ReducingSink extends Box<R>
implements AccumulatingSink<Integer, R, ReducingSink>, Sink.OfInt {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(int t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp<Integer, R, ReducingSink>(StreamShape.INT_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code long} values.
*
* @param identity the identity for the combining function
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp<Long, Long>
makeLong(long identity, LongBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<Long, Long, ReducingSink>, Sink.OfLong {
private long state;
@Override
public void begin(long size) {
state = identity;
}
@Override
public void accept(long t) {
state = operator.applyAsLong(state, t);
}
@Override
public Long get() {
return state;
}
@Override
public void combine(ReducingSink other) {
accept(other.state);
}
}
return new ReduceOp<Long, Long, ReducingSink>(StreamShape.LONG_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code long} values, producing an optional long result.
*
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp<Long, OptionalLong>
makeLong(LongBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<Long, OptionalLong, ReducingSink>, Sink.OfLong {
private boolean empty;
private long state;
public void begin(long size) {
empty = true;
state = 0;
}
@Override
public void accept(long t) {
if (empty) {
empty = false;
state = t;
}
else {
state = operator.applyAsLong(state, t);
}
}
@Override
public OptionalLong get() {
return empty ? OptionalLong.empty() : OptionalLong.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp<Long, OptionalLong, ReducingSink>(StreamShape.LONG_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* {@code long} values.
*
* @param <R> the type of the result
* @param supplier a factory to produce a new accumulator of the result type
* @param accumulator a function to incorporate an int into an
* accumulator
* @param combiner a function to combine an accumulator into another
* @return a {@code TerminalOp} implementing the reduction
*/
public static <R> TerminalOp<Long, R>
makeLong(Supplier<R> supplier,
ObjLongConsumer<R> accumulator,
BinaryOperator<R> combiner) {
Objects.requireNonNull(supplier);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(combiner);
class ReducingSink extends Box<R>
implements AccumulatingSink<Long, R, ReducingSink>, Sink.OfLong {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(long t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp<Long, R, ReducingSink>(StreamShape.LONG_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code double} values.
*
* @param identity the identity for the combining function
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp<Double, Double>
makeDouble(double identity, DoubleBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<Double, Double, ReducingSink>, Sink.OfDouble {
private double state;
@Override
public void begin(long size) {
state = identity;
}
@Override
public void accept(double t) {
state = operator.applyAsDouble(state, t);
}
@Override
public Double get() {
return state;
}
@Override
public void combine(ReducingSink other) {
accept(other.state);
}
}
return new ReduceOp<Double, Double, ReducingSink>(StreamShape.DOUBLE_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a functional reduce on
* {@code double} values, producing an optional double result.
*
* @param operator the combining function
* @return a {@code TerminalOp} implementing the reduction
*/
public static TerminalOp<Double, OptionalDouble>
makeDouble(DoubleBinaryOperator operator) {
Objects.requireNonNull(operator);
class ReducingSink
implements AccumulatingSink<Double, OptionalDouble, ReducingSink>, Sink.OfDouble {
private boolean empty;
private double state;
public void begin(long size) {
empty = true;
state = 0;
}
@Override
public void accept(double t) {
if (empty) {
empty = false;
state = t;
}
else {
state = operator.applyAsDouble(state, t);
}
}
@Override
public OptionalDouble get() {
return empty ? OptionalDouble.empty() : OptionalDouble.of(state);
}
@Override
public void combine(ReducingSink other) {
if (!other.empty)
accept(other.state);
}
}
return new ReduceOp<Double, OptionalDouble, ReducingSink>(StreamShape.DOUBLE_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* Constructs a {@code TerminalOp} that implements a mutable reduce on
* {@code double} values.
*
* @param <R> the type of the result
* @param supplier a factory to produce a new accumulator of the result type
* @param accumulator a function to incorporate an int into an
* accumulator
* @param combiner a function to combine an accumulator into another
* @return a {@code TerminalOp} implementing the reduction
*/
public static <R> TerminalOp<Double, R>
makeDouble(Supplier<R> supplier,
ObjDoubleConsumer<R> accumulator,
BinaryOperator<R> combiner) {
Objects.requireNonNull(supplier);
Objects.requireNonNull(accumulator);
Objects.requireNonNull(combiner);
class ReducingSink extends Box<R>
implements AccumulatingSink<Double, R, ReducingSink>, Sink.OfDouble {
@Override
public void begin(long size) {
state = supplier.get();
}
@Override
public void accept(double t) {
accumulator.accept(state, t);
}
@Override
public void combine(ReducingSink other) {
state = combiner.apply(state, other.state);
}
}
return new ReduceOp<Double, R, ReducingSink>(StreamShape.DOUBLE_VALUE) {
@Override
public ReducingSink makeSink() {
return new ReducingSink();
}
};
}
/**
* A type of {@code TerminalSink} that implements an associative reducing
* operation on elements of type {@code T} and producing a result of type
* {@code R}.
*
* @param <T> the type of input element to the combining operation
* @param <R> the result type
* @param <K> the type of the {@code AccumulatingSink}.
*/
private interface AccumulatingSink<T, R, K extends AccumulatingSink<T, R, K>>
extends TerminalSink<T, R> {
public void combine(K other);
}
/**
* State box for a single state element, used as a base class for
* {@code AccumulatingSink} instances
*
* @param <U> The type of the state element
*/
private static abstract class Box<U> {
U state;
Box() {} // Avoid creation of special accessor
public U get() {
return state;
}
}
/**
* A {@code TerminalOp} that evaluates a stream pipeline and sends the
* output into an {@code AccumulatingSink}, which performs a reduce
* operation. The {@code AccumulatingSink} must represent an associative
* reducing operation.
*
* @param <T> the output type of the stream pipeline
* @param <R> the result type of the reducing operation
* @param <S> the type of the {@code AccumulatingSink}
*/
private static abstract class ReduceOp<T, R, S extends AccumulatingSink<T, R, S>>
implements TerminalOp<T, R> {
private final StreamShape inputShape;
/**
* Create a {@code ReduceOp} of the specified stream shape which uses
* the specified {@code Supplier} to create accumulating sinks.
*
* @param shape The shape of the stream pipeline
*/
ReduceOp(StreamShape shape) {
inputShape = shape;
}
public abstract S makeSink();
@Override
public StreamShape inputShape() {
return inputShape;
}
@Override
public <P_IN> R evaluateSequential(PipelineHelper<T> helper,
Spliterator<P_IN> spliterator) {
return helper.wrapAndCopyInto(makeSink(), spliterator).get();
}
@Override
public <P_IN> R evaluateParallel(PipelineHelper<T> helper,
Spliterator<P_IN> spliterator) {
return new ReduceTask<>(this, helper, spliterator).invoke().get();
}
}
/**
* A {@code ForkJoinTask} for performing a parallel reduce operation.
*/
@SuppressWarnings("serial")
private static final class ReduceTask<P_IN, P_OUT, R,
S extends AccumulatingSink<P_OUT, R, S>>
extends AbstractTask<P_IN, P_OUT, S, ReduceTask<P_IN, P_OUT, R, S>> {
private final ReduceOp<P_OUT, R, S> op;
ReduceTask(ReduceOp<P_OUT, R, S> op,
PipelineHelper<P_OUT> helper,
Spliterator<P_IN> spliterator) {
super(helper, spliterator);
this.op = op;
}
ReduceTask(ReduceTask<P_IN, P_OUT, R, S> parent,
Spliterator<P_IN> spliterator) {
super(parent, spliterator);
this.op = parent.op;
}
@Override
protected ReduceTask<P_IN, P_OUT, R, S> makeChild(Spliterator<P_IN> spliterator) {
return new ReduceTask<>(this, spliterator);
}
@Override
protected S doLeaf() {
return helper.wrapAndCopyInto(op.makeSink(), spliterator);
}
@Override
public void onCompletion(CountedCompleter<?> caller) {
if (!isLeaf()) {
S leftResult = leftChild.getLocalResult();
leftResult.combine(rightChild.getLocalResult());
setLocalResult(leftResult);
}
// GC spliterator, left and right child
super.onCompletion(caller);
}
}
}
