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rxjava2-backport developed by David Karnok

There is a newer version: 2.0.0-RC3

/**
 * Copyright 2015 David Karnok and Netflix, Inc.
 * 
 * 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.internal.operators;

import java.util.concurrent.Callable;

import org.reactivestreams.*;

import hu.akarnokd.rxjava2.internal.subscriptions.ScalarAsyncSubscription;

public final class PublisherScalarAsyncSource implements Publisher {
    final Callable callable;
    public PublisherScalarAsyncSource(Callable callable) {
        this.callable = callable;
    }
    @Override
    public void subscribe(Subscriber s) {
        ScalarAsyncSubscription sub = new ScalarAsyncSubscription(s);
        s.onSubscribe(sub);
        if (sub.isComplete()) {
            return;
        }
        T value;
        try {
            value = callable.call();
        } catch (Throwable e) {
            if (!sub.isComplete()) {
                s.onError(e);
            }
            return;
        }
        if (sub.isComplete()) {
            return;
        }
        sub.setValue(value);
    }
}