--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.net.http/share/classes/java/net/http/internal/BufferingSubscriber.java Wed Feb 07 14:17:24 2018 +0000
@@ -0,0 +1,315 @@
+/*
+ * Copyright (c) 2017, 2018, 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.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package java.net.http.internal;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.ListIterator;
+import java.util.Objects;
+import java.util.concurrent.CompletionStage;
+import java.util.concurrent.Flow;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.net.http.HttpResponse.BodySubscriber;
+import java.net.http.internal.common.Demand;
+import java.net.http.internal.common.SequentialScheduler;
+import java.net.http.internal.common.Utils;
+
+/**
+ * A buffering BodySubscriber. When subscribed, accumulates ( buffers ) a given
+ * amount ( in bytes ) of a publisher's data before pushing it to a downstream
+ * subscriber.
+ */
+public class BufferingSubscriber<T> implements BodySubscriber<T>
+{
+ /** The downstream consumer of the data. */
+ private final BodySubscriber<T> downstreamSubscriber;
+ /** The amount of data to be accumulate before pushing downstream. */
+ private final int bufferSize;
+
+ /** The subscription, created lazily. */
+ private volatile Flow.Subscription subscription;
+ /** The downstream subscription, created lazily. */
+ private volatile DownstreamSubscription downstreamSubscription;
+
+ /** Must be held when accessing the internal buffers. */
+ private final Object buffersLock = new Object();
+ /** The internal buffers holding the buffered data. */
+ private ArrayList<ByteBuffer> internalBuffers;
+ /** The actual accumulated remaining bytes in internalBuffers. */
+ private int accumulatedBytes;
+
+ /** Holds the Throwable from upstream's onError. */
+ private volatile Throwable throwable;
+
+ /** State of the buffering subscriber:
+ * 1) [UNSUBSCRIBED] when initially created
+ * 2) [ACTIVE] when subscribed and can receive data
+ * 3) [ERROR | CANCELLED | COMPLETE] (terminal state)
+ */
+ static final int UNSUBSCRIBED = 0x01;
+ static final int ACTIVE = 0x02;
+ static final int ERROR = 0x04;
+ static final int CANCELLED = 0x08;
+ static final int COMPLETE = 0x10;
+
+ private volatile int state;
+
+ public BufferingSubscriber(BodySubscriber<T> downstreamSubscriber,
+ int bufferSize) {
+ this.downstreamSubscriber = Objects.requireNonNull(downstreamSubscriber);
+ this.bufferSize = bufferSize;
+ synchronized (buffersLock) {
+ internalBuffers = new ArrayList<>();
+ }
+ state = UNSUBSCRIBED;
+ }
+
+ /** Returns the number of bytes remaining in the given buffers. */
+ private static final long remaining(List<ByteBuffer> buffers) {
+ return buffers.stream().mapToLong(ByteBuffer::remaining).sum();
+ }
+
+ /**
+ * Tells whether, or not, there is at least a sufficient number of bytes
+ * accumulated in the internal buffers. If the subscriber is COMPLETE, and
+ * has some buffered data, then there is always enough ( to pass downstream ).
+ */
+ private final boolean hasEnoughAccumulatedBytes() {
+ assert Thread.holdsLock(buffersLock);
+ return accumulatedBytes >= bufferSize
+ || (state == COMPLETE && accumulatedBytes > 0);
+ }
+
+ /**
+ * Returns a new, unmodifiable, List<ByteBuffer> containing exactly the
+ * amount of data as required before pushing downstream. The amount of data
+ * may be less than required ( bufferSize ), in the case where the subscriber
+ * is COMPLETE.
+ */
+ private List<ByteBuffer> fromInternalBuffers() {
+ assert Thread.holdsLock(buffersLock);
+ int leftToFill = bufferSize;
+ int state = this.state;
+ assert (state == ACTIVE || state == CANCELLED)
+ ? accumulatedBytes >= leftToFill : true;
+ List<ByteBuffer> dsts = new ArrayList<>();
+
+ ListIterator<ByteBuffer> itr = internalBuffers.listIterator();
+ while (itr.hasNext()) {
+ ByteBuffer b = itr.next();
+ if (b.remaining() <= leftToFill) {
+ itr.remove();
+ if (b.position() != 0)
+ b = b.slice(); // ensure position = 0 when propagated
+ dsts.add(b);
+ leftToFill -= b.remaining();
+ accumulatedBytes -= b.remaining();
+ if (leftToFill == 0)
+ break;
+ } else {
+ int prevLimit = b.limit();
+ b.limit(b.position() + leftToFill);
+ ByteBuffer slice = b.slice();
+ dsts.add(slice);
+ b.limit(prevLimit);
+ b.position(b.position() + leftToFill);
+ accumulatedBytes -= leftToFill;
+ leftToFill = 0;
+ break;
+ }
+ }
+ assert (state == ACTIVE || state == CANCELLED)
+ ? leftToFill == 0 : state == COMPLETE;
+ assert (state == ACTIVE || state == CANCELLED)
+ ? remaining(dsts) == bufferSize : state == COMPLETE;
+ assert accumulatedBytes >= 0;
+ assert dsts.stream().noneMatch(b -> b.position() != 0);
+ return Collections.unmodifiableList(dsts);
+ }
+
+ /** Subscription that is passed to the downstream subscriber. */
+ private class DownstreamSubscription implements Flow.Subscription {
+ private final AtomicBoolean cancelled = new AtomicBoolean(); // false
+ private final Demand demand = new Demand();
+ private volatile boolean illegalArg;
+
+ @Override
+ public void request(long n) {
+ if (cancelled.get() || illegalArg) {
+ return;
+ }
+ if (n <= 0L) {
+ // pass the "bad" value upstream so the Publisher can deal with
+ // it appropriately, i.e. invoke onError
+ illegalArg = true;
+ subscription.request(n);
+ return;
+ }
+
+ demand.increase(n);
+
+ pushDemanded();
+ }
+
+ private final SequentialScheduler pushDemandedScheduler =
+ new SequentialScheduler(new PushDemandedTask());
+
+ void pushDemanded() {
+ if (cancelled.get())
+ return;
+ pushDemandedScheduler.runOrSchedule();
+ }
+
+ class PushDemandedTask extends SequentialScheduler.CompleteRestartableTask {
+ @Override
+ public void run() {
+ try {
+ Throwable t = throwable;
+ if (t != null) {
+ pushDemandedScheduler.stop(); // stop the demand scheduler
+ downstreamSubscriber.onError(t);
+ return;
+ }
+
+ while (true) {
+ List<ByteBuffer> item;
+ synchronized (buffersLock) {
+ if (cancelled.get())
+ return;
+ if (!hasEnoughAccumulatedBytes())
+ break;
+ if (!demand.tryDecrement())
+ break;
+ item = fromInternalBuffers();
+ }
+ assert item != null;
+
+ downstreamSubscriber.onNext(item);
+ }
+ if (cancelled.get())
+ return;
+
+ // complete only if all data consumed
+ boolean complete;
+ synchronized (buffersLock) {
+ complete = state == COMPLETE && internalBuffers.isEmpty();
+ }
+ if (complete) {
+ assert internalBuffers.isEmpty();
+ pushDemandedScheduler.stop(); // stop the demand scheduler
+ downstreamSubscriber.onComplete();
+ return;
+ }
+ } catch (Throwable t) {
+ cancel(); // cancel if there is any error
+ throw t;
+ }
+
+ boolean requestMore = false;
+ synchronized (buffersLock) {
+ if (!hasEnoughAccumulatedBytes() && !demand.isFulfilled()) {
+ // request more upstream data
+ requestMore = true;
+ }
+ }
+ if (requestMore)
+ subscription.request(1);
+ }
+ }
+
+ @Override
+ public void cancel() {
+ if (cancelled.compareAndExchange(false, true))
+ return; // already cancelled
+
+ state = CANCELLED; // set CANCELLED state of upstream subscriber
+ subscription.cancel(); // cancel upstream subscription
+ pushDemandedScheduler.stop(); // stop the demand scheduler
+ }
+ }
+
+ @Override
+ public void onSubscribe(Flow.Subscription subscription) {
+ Objects.requireNonNull(subscription);
+ if (this.subscription != null) {
+ subscription.cancel();
+ return;
+ }
+
+ int s = this.state;
+ assert s == UNSUBSCRIBED;
+ state = ACTIVE;
+ this.subscription = subscription;
+ downstreamSubscription = new DownstreamSubscription();
+ downstreamSubscriber.onSubscribe(downstreamSubscription);
+ }
+
+ @Override
+ public void onNext(List<ByteBuffer> item) {
+ Objects.requireNonNull(item);
+
+ int s = state;
+ if (s == CANCELLED)
+ return;
+
+ if (s != ACTIVE)
+ throw new InternalError("onNext on inactive subscriber");
+
+ synchronized (buffersLock) {
+ internalBuffers.addAll(item);
+ accumulatedBytes += remaining(item);
+ }
+
+ downstreamSubscription.pushDemanded();
+ }
+
+ @Override
+ public void onError(Throwable incomingThrowable) {
+ Objects.requireNonNull(incomingThrowable);
+ int s = state;
+ assert s == ACTIVE : "Expected ACTIVE, got:" + s;
+ state = ERROR;
+ Throwable t = this.throwable;
+ assert t == null : "Expected null, got:" + t;
+ this.throwable = incomingThrowable;
+ downstreamSubscription.pushDemanded();
+ }
+
+ @Override
+ public void onComplete() {
+ int s = state;
+ assert s == ACTIVE : "Expected ACTIVE, got:" + s;
+ state = COMPLETE;
+ downstreamSubscription.pushDemanded();
+ }
+
+ @Override
+ public CompletionStage<T> getBody() {
+ return downstreamSubscriber.getBody();
+ }
+}