ratpack.stream.bytebuf.internal.ByteBufComposingPublisher.java Source code

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Here is the source code for ratpack.stream.bytebuf.internal.ByteBufComposingPublisher.java

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/*
 * Copyright 2017 the original author or 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 ratpack.stream.bytebuf.internal;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.buffer.CompositeByteBuf;
import io.netty.util.ReferenceCountUtil;
import org.reactivestreams.Publisher;
import org.reactivestreams.Subscriber;
import org.reactivestreams.Subscription;
import ratpack.stream.TransformablePublisher;
import ratpack.stream.internal.ManagedSubscription;

public class ByteBufComposingPublisher implements TransformablePublisher<CompositeByteBuf> {

    private enum State {
        Fetching, Writing, Closed
    }

    private final Publisher<? extends ByteBuf> upstream;
    private final ByteBufAllocator alloc;
    private final int maxNum;
    private final long watermark;

    public ByteBufComposingPublisher(int maxNum, long sizeWatermark, ByteBufAllocator alloc,
            Publisher<? extends ByteBuf> upstream) {
        this.upstream = upstream;
        this.alloc = alloc;
        this.maxNum = maxNum;
        this.watermark = sizeWatermark;
    }

    @Override
    public void subscribe(Subscriber<? super CompositeByteBuf> subscriber) {
        subscriber.onSubscribe(new ManagedSubscription<CompositeByteBuf>(subscriber, ByteBuf::release) {

            private Subscription subscription;
            private CompositeByteBuf composite;

            private volatile State state;

            @Override
            protected void onRequest(long n) {
                if (subscription == null) {
                    upstream.subscribe(new Subscriber<ByteBuf>() {

                        @Override
                        public void onSubscribe(Subscription s) {
                            subscription = s;
                            state = State.Fetching;
                            s.request(1);
                        }

                        @Override
                        public void onNext(ByteBuf t) {
                            if (state == State.Closed) {
                                t.release();
                                return;
                            }

                            if (composite == null) {
                                composite = alloc.compositeBuffer(maxNum);
                            }
                            composite.addComponent(true, t);
                            if (composite.numComponents() == maxNum || composite.readableBytes() >= watermark) {
                                state = State.Writing;
                                emitNext(composite);
                                composite = null;
                                maybeFetch();
                            } else {
                                subscription.request(1);
                            }
                        }

                        @Override
                        public void onError(Throwable t) {
                            state = State.Closed;
                            ReferenceCountUtil.release(composite);
                            emitError(t);
                        }

                        @Override
                        public void onComplete() {
                            state = State.Closed;

                            if (composite != null) {
                                emitNext(composite);
                            }

                            emitComplete();
                        }
                    });
                } else {
                    maybeFetch();
                }
            }

            private void maybeFetch() {
                if (getDemand() > 0 && state != State.Fetching) {
                    state = State.Fetching;
                    subscription.request(1);
                }
            }

            @Override
            protected void onCancel() {
                state = State.Closed;
                ReferenceCountUtil.release(composite);
                if (subscription != null) {
                    subscription.cancel();
                }
            }
        });
    }
}