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rxjava2-extensions developed by David Karnok
There is a newer version: 0.20.10
/*
 * Copyright 2016-2017 David Karnok
 *
 * 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 hu.akarnokd.rxjava2.parallel;

import org.reactivestreams.*;

import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.subscriptions.SubscriptionHelper;
import io.reactivex.plugins.RxJavaPlugins;

/**
 * Maps each 'rail' of the source ParallelFlowable with a mapper function.
 *
 * @param  the input value type
 * @param  the output value type
 */
@SuppressWarnings("deprecation")
final class ParallelMap extends ParallelFlowable {

    final ParallelFlowable source;

    final Function mapper;

    ParallelMap(ParallelFlowable source, Function mapper) {
        this.source = source;
        this.mapper = mapper;
    }

    @Override
    public void subscribe(Subscriber[] subscribers) {
        if (!validate(subscribers)) {
            return;
        }

        int n = subscribers.length;
        @SuppressWarnings("unchecked")
        Subscriber[] parents = new Subscriber[n];

        for (int i = 0; i < n; i++) {
            parents[i] = new ParallelMapSubscriber(subscribers[i], mapper);
        }

        source.subscribe(parents);
    }

    @Override
    public int parallelism() {
        return source.parallelism();
    }

    static final class ParallelMapSubscriber implements Subscriber, Subscription {

        final Subscriber actual;

        final Function mapper;

        Subscription s;

        boolean done;

        ParallelMapSubscriber(Subscriber actual, Function mapper) {
            this.actual = actual;
            this.mapper = mapper;
        }

        @Override
        public void request(long n) {
            s.request(n);
        }

        @Override
        public void cancel() {
            s.cancel();
        }

        @Override
        public void onSubscribe(Subscription s) {
            if (SubscriptionHelper.validate(this.s, s)) {
                this.s = s;

                actual.onSubscribe(this);
            }
        }

        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }
            R v;

            try {
                v = ObjectHelper.requireNonNull(mapper.apply(t), "The mapper returned a null value");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                cancel();
                onError(ex);
                return;
            }

            actual.onNext(v);
        }

        @Override
        public void onError(Throwable t) {
            if (done) {
                RxJavaPlugins.onError(t);
                return;
            }
            done = true;
            actual.onError(t);
        }

        @Override
        public void onComplete() {
            if (done) {
                return;
            }
            done = true;
            actual.onComplete();
        }

    }
}