PseudoPublisher.java

/*
 * Copyright (c) 2016, 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
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package jdk.incubator.http;

import java.util.concurrent.Flow;
import java.util.concurrent.atomic.AtomicBoolean;

// Completes the subscription on first request. Never calls onNext()

class PseudoPublisher<T> implements Flow.Publisher<T> {

    private final Throwable throwable;

    PseudoPublisher() {
        this(null);
    }

    PseudoPublisher(Throwable throwable) {
        this.throwable = throwable;
    }

    @Override
    public void subscribe(Flow.Subscriber<? super T> subscriber) {
        subscriber.onSubscribe(new Subscription(subscriber));
    }

    private class Subscription implements Flow.Subscription {

        private final Flow.Subscriber<? super T> subscriber;
        private final AtomicBoolean done = new AtomicBoolean();

        Subscription(Flow.Subscriber<? super T> subscriber) {
            this.subscriber = subscriber;
        }

        @Override
        public void request(long n) {
            if (done.compareAndSet(false, true)) {
                if (n > 0) {
                    if (throwable == null) {
                        subscriber.onComplete();
                    } else {
                        subscriber.onError(throwable);
                    }
                } else {
                    subscriber.onError(new IllegalArgumentException("request(" + n + ")"));
                }
            }
        }

        @Override
        public void cancel() {
            done.set(true);
        }

    }
}