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* 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,
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*
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package java.util.stream;
import java.util.Objects;
import java.util.Spliterator;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CountedCompleter;
import java.util.concurrent.ForkJoinTask;
import java.util.function.Consumer;
import java.util.function.DoubleConsumer;
import java.util.function.IntConsumer;
import java.util.function.IntFunction;
import java.util.function.LongConsumer;
/**
* Factory for creating instances of {@code TerminalOp} that perform an
* action for every element of a stream. Supported variants include unordered
* traversal (elements are provided to the {@code Consumer} as soon as they are
* available), and ordered traversal (elements are provided to the
* {@code Consumer} in encounter order.)
*
* <p>Elements are provided to the {@code Consumer} on whatever thread and
* whatever order they become available. For ordered traversals, it is
* guaranteed that processing an element <em>happens-before</em> processing
* subsequent elements in the encounter order.
*
* <p>Exceptions occurring as a result of sending an element to the
* {@code Consumer} will be relayed to the caller and traversal will be
* prematurely terminated.
*
* @since 1.8
*/
final class ForEachOps {
private ForEachOps() { }
/**
* Constructs a {@code TerminalOp} that perform an action for every element
* of a stream.
*
* @param action the {@code Consumer} that receives all elements of a
* stream
* @param ordered whether an ordered traversal is requested
* @param <T> the type of the stream elements
* @return the {@code TerminalOp} instance
*/
public static <T> TerminalOp<T, Void> makeRef(Consumer<? super T> action,
boolean ordered) {
Objects.requireNonNull(action);
return new ForEachOp.OfRef<>(action, ordered);
}
/**
* Constructs a {@code TerminalOp} that perform an action for every element
* of an {@code IntStream}.
*
* @param action the {@code IntConsumer} that receives all elements of a
* stream
* @param ordered whether an ordered traversal is requested
* @return the {@code TerminalOp} instance
*/
public static TerminalOp<Integer, Void> makeInt(IntConsumer action,
boolean ordered) {
Objects.requireNonNull(action);
return new ForEachOp.OfInt(action, ordered);
}
/**
* Constructs a {@code TerminalOp} that perform an action for every element
* of a {@code LongStream}.
*
* @param action the {@code LongConsumer} that receives all elements of a
* stream
* @param ordered whether an ordered traversal is requested
* @return the {@code TerminalOp} instance
*/
public static TerminalOp<Long, Void> makeLong(LongConsumer action,
boolean ordered) {
Objects.requireNonNull(action);
return new ForEachOp.OfLong(action, ordered);
}
/**
* Constructs a {@code TerminalOp} that perform an action for every element
* of a {@code DoubleStream}.
*
* @param action the {@code DoubleConsumer} that receives all elements of
* a stream
* @param ordered whether an ordered traversal is requested
* @return the {@code TerminalOp} instance
*/
public static TerminalOp<Double, Void> makeDouble(DoubleConsumer action,
boolean ordered) {
Objects.requireNonNull(action);
return new ForEachOp.OfDouble(action, ordered);
}
/**
* A {@code TerminalOp} that evaluates a stream pipeline and sends the
* output to itself as a {@code TerminalSink}. Elements will be sent in
* whatever thread they become available. If the traversal is unordered,
* they will be sent independent of the stream's encounter order.
*
* <p>This terminal operation is stateless. For parallel evaluation, each
* leaf instance of a {@code ForEachTask} will send elements to the same
* {@code TerminalSink} reference that is an instance of this class.
*
* @param <T> the output type of the stream pipeline
*/
abstract static class ForEachOp<T>
implements TerminalOp<T, Void>, TerminalSink<T, Void> {
private final boolean ordered;
protected ForEachOp(boolean ordered) {
this.ordered = ordered;
}
// TerminalOp
@Override
public int getOpFlags() {
return ordered ? 0 : StreamOpFlag.NOT_ORDERED;
}
@Override
public <S> Void evaluateSequential(PipelineHelper<T> helper,
Spliterator<S> spliterator) {
return helper.wrapAndCopyInto(this, spliterator).get();
}
@Override
public <S> Void evaluateParallel(PipelineHelper<T> helper,
Spliterator<S> spliterator) {
if (ordered)
new ForEachOrderedTask<>(helper, spliterator, this).invoke();
else
new ForEachTask<>(helper, spliterator, helper.wrapSink(this)).invoke();
return null;
}
// TerminalSink
@Override
public Void get() {
return null;
}
// Implementations
/** Implementation class for reference streams */
static final class OfRef<T> extends ForEachOp<T> {
final Consumer<? super T> consumer;
OfRef(Consumer<? super T> consumer, boolean ordered) {
super(ordered);
this.consumer = consumer;
}
@Override
public void accept(T t) {
consumer.accept(t);
}
}
/** Implementation class for {@code IntStream} */
static final class OfInt extends ForEachOp<Integer>
implements Sink.OfInt {
final IntConsumer consumer;
OfInt(IntConsumer consumer, boolean ordered) {
super(ordered);
this.consumer = consumer;
}
@Override
public StreamShape inputShape() {
return StreamShape.INT_VALUE;
}
@Override
public void accept(int t) {
consumer.accept(t);
}
}
/** Implementation class for {@code LongStream} */
static final class OfLong extends ForEachOp<Long>
implements Sink.OfLong {
final LongConsumer consumer;
OfLong(LongConsumer consumer, boolean ordered) {
super(ordered);
this.consumer = consumer;
}
@Override
public StreamShape inputShape() {
return StreamShape.LONG_VALUE;
}
@Override
public void accept(long t) {
consumer.accept(t);
}
}
/** Implementation class for {@code DoubleStream} */
static final class OfDouble extends ForEachOp<Double>
implements Sink.OfDouble {
final DoubleConsumer consumer;
OfDouble(DoubleConsumer consumer, boolean ordered) {
super(ordered);
this.consumer = consumer;
}
@Override
public StreamShape inputShape() {
return StreamShape.DOUBLE_VALUE;
}
@Override
public void accept(double t) {
consumer.accept(t);
}
}
}
/** A {@code ForkJoinTask} for performing a parallel for-each operation */
@SuppressWarnings("serial")
static final class ForEachTask<S, T> extends CountedCompleter<Void> {
private Spliterator<S> spliterator;
private final Sink<S> sink;
private final PipelineHelper<T> helper;
private long targetSize;
ForEachTask(PipelineHelper<T> helper,
Spliterator<S> spliterator,
Sink<S> sink) {
super(null);
this.sink = sink;
this.helper = helper;
this.spliterator = spliterator;
this.targetSize = 0L;
}
ForEachTask(ForEachTask<S, T> parent, Spliterator<S> spliterator) {
super(parent);
this.spliterator = spliterator;
this.sink = parent.sink;
this.targetSize = parent.targetSize;
this.helper = parent.helper;
}
// Similar to AbstractTask but doesn't need to track child tasks
public void compute() {
Spliterator<S> rightSplit = spliterator, leftSplit;
long sizeEstimate = rightSplit.estimateSize(), sizeThreshold;
if ((sizeThreshold = targetSize) == 0L)
targetSize = sizeThreshold = AbstractTask.suggestTargetSize(sizeEstimate);
boolean isShortCircuit = StreamOpFlag.SHORT_CIRCUIT.isKnown(helper.getStreamAndOpFlags());
boolean forkRight = false;
Sink<S> taskSink = sink;
ForEachTask<S, T> task = this;
while (!isShortCircuit || !taskSink.cancellationRequested()) {
if (sizeEstimate <= sizeThreshold ||
(leftSplit = rightSplit.trySplit()) == null) {
task.helper.copyInto(taskSink, rightSplit);
break;
}
ForEachTask<S, T> leftTask = new ForEachTask<>(task, leftSplit);
task.addToPendingCount(1);
ForEachTask<S, T> taskToFork;
if (forkRight) {
forkRight = false;
rightSplit = leftSplit;
taskToFork = task;
task = leftTask;
}
else {
forkRight = true;
taskToFork = leftTask;
}
taskToFork.fork();
sizeEstimate = rightSplit.estimateSize();
}
task.spliterator = null;
task.propagateCompletion();
}
}
/**
* A {@code ForkJoinTask} for performing a parallel for-each operation
* which visits the elements in encounter order
*/
@SuppressWarnings("serial")
static final class ForEachOrderedTask<S, T> extends CountedCompleter<Void> {
/*
* Our goal is to ensure that the elements associated with a task are
* processed according to an in-order traversal of the computation tree.
* We use completion counts for representing these dependencies, so that
* a task does not complete until all the tasks preceding it in this
* order complete. We use the "completion map" to associate the next
* task in this order for any left child. We increase the pending count
* of any node on the right side of such a mapping by one to indicate
* its dependency, and when a node on the left side of such a mapping
* completes, it decrements the pending count of its corresponding right
* side. As the computation tree is expanded by splitting, we must
* atomically update the mappings to maintain the invariant that the
* completion map maps left children to the next node in the in-order
* traversal.
*
* Take, for example, the following computation tree of tasks:
*
* a
* / \
* b c
* / \ / \
* d e f g
*
* The complete map will contain (not necessarily all at the same time)
* the following associations:
*
* d -> e
* b -> f
* f -> g
*
* Tasks e, f, g will have their pending counts increased by 1.
*
* The following relationships hold:
*
* - completion of d "happens-before" e;
* - completion of d and e "happens-before b;
* - completion of b "happens-before" f; and
* - completion of f "happens-before" g
*
* Thus overall the "happens-before" relationship holds for the
* reporting of elements, covered by tasks d, e, f and g, as specified
* by the forEachOrdered operation.
*/
private final PipelineHelper<T> helper;
private Spliterator<S> spliterator;
private final long targetSize;
private final ConcurrentHashMap<ForEachOrderedTask<S, T>, ForEachOrderedTask<S, T>> completionMap;
private final Sink<T> action;
private final ForEachOrderedTask<S, T> leftPredecessor;
private Node<T> node;
protected ForEachOrderedTask(PipelineHelper<T> helper,
Spliterator<S> spliterator,
Sink<T> action) {
super(null);
this.helper = helper;
this.spliterator = spliterator;
this.targetSize = AbstractTask.suggestTargetSize(spliterator.estimateSize());
// Size map to avoid concurrent re-sizes
this.completionMap = new ConcurrentHashMap<>(Math.max(16, AbstractTask.LEAF_TARGET << 1));
this.action = action;
this.leftPredecessor = null;
}
ForEachOrderedTask(ForEachOrderedTask<S, T> parent,
Spliterator<S> spliterator,
ForEachOrderedTask<S, T> leftPredecessor) {
super(parent);
this.helper = parent.helper;
this.spliterator = spliterator;
this.targetSize = parent.targetSize;
this.completionMap = parent.completionMap;
this.action = parent.action;
this.leftPredecessor = leftPredecessor;
}
@Override
public final void compute() {
doCompute(this);
}
private static <S, T> void doCompute(ForEachOrderedTask<S, T> task) {
Spliterator<S> rightSplit = task.spliterator, leftSplit;
long sizeThreshold = task.targetSize;
boolean forkRight = false;
while (rightSplit.estimateSize() > sizeThreshold &&
(leftSplit = rightSplit.trySplit()) != null) {
ForEachOrderedTask<S, T> leftChild =
new ForEachOrderedTask<>(task, leftSplit, task.leftPredecessor);
ForEachOrderedTask<S, T> rightChild =
new ForEachOrderedTask<>(task, rightSplit, leftChild);
// Fork the parent task
// Completion of the left and right children "happens-before"
// completion of the parent
task.addToPendingCount(1);
// Completion of the left child "happens-before" completion of
// the right child
rightChild.addToPendingCount(1);
task.completionMap.put(leftChild, rightChild);
// If task is not on the left spine
if (task.leftPredecessor != null) {
/*
* Completion of left-predecessor, or left subtree,
* "happens-before" completion of left-most leaf node of
* right subtree.
* The left child's pending count needs to be updated before
* it is associated in the completion map, otherwise the
* left child can complete prematurely and violate the
* "happens-before" constraint.
*/
leftChild.addToPendingCount(1);
// Update association of left-predecessor to left-most
// leaf node of right subtree
if (task.completionMap.replace(task.leftPredecessor, task, leftChild)) {
// If replaced, adjust the pending count of the parent
// to complete when its children complete
task.addToPendingCount(-1);
} else {
// Left-predecessor has already completed, parent's
// pending count is adjusted by left-predecessor;
// left child is ready to complete
leftChild.addToPendingCount(-1);
}
}
ForEachOrderedTask<S, T> taskToFork;
if (forkRight) {
forkRight = false;
rightSplit = leftSplit;
task = leftChild;
taskToFork = rightChild;
}
else {
forkRight = true;
task = rightChild;
taskToFork = leftChild;
}
taskToFork.fork();
}
/*
* Task's pending count is either 0 or 1. If 1 then the completion
* map will contain a value that is task, and two calls to
* tryComplete are required for completion, one below and one
* triggered by the completion of task's left-predecessor in
* onCompletion. Therefore there is no data race within the if
* block.
*/
if (task.getPendingCount() > 0) {
// Cannot complete just yet so buffer elements into a Node
// for use when completion occurs
@SuppressWarnings("unchecked")
IntFunction<T[]> generator = size -> (T[]) new Object[size];
Node.Builder<T> nb = task.helper.makeNodeBuilder(
task.helper.exactOutputSizeIfKnown(rightSplit),
generator);
task.node = task.helper.wrapAndCopyInto(nb, rightSplit).build();
task.spliterator = null;
}
task.tryComplete();
}
@Override
public void onCompletion(CountedCompleter<?> caller) {
if (node != null) {
// Dump buffered elements from this leaf into the sink
node.forEach(action);
node = null;
}
else if (spliterator != null) {
// Dump elements output from this leaf's pipeline into the sink
helper.wrapAndCopyInto(action, spliterator);
spliterator = null;
}
// The completion of this task *and* the dumping of elements
// "happens-before" completion of the associated left-most leaf task
// of right subtree (if any, which can be this task's right sibling)
//
ForEachOrderedTask<S, T> leftDescendant = completionMap.remove(this);
if (leftDescendant != null)
leftDescendant.tryComplete();
}
}
}