hu.akarnokd.rxjava2.internal.operators.OperatorElementAt Maven / Gradle / Ivy

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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 org.reactivestreams.*;

import hu.akarnokd.rxjava2.Observable.Operator;
import hu.akarnokd.rxjava2.plugins.RxJavaPlugins;

public final class OperatorElementAt implements Operator {
    final long index;
    final T defaultValue;
    public OperatorElementAt(long index, T defaultValue) {
        this.index = index;
        this.defaultValue = defaultValue;
    }
    @Override
    public Subscriber apply(Subscriber t) {
        return new ElementAtSubscriber(t, index, defaultValue);
    }
    
    static final class ElementAtSubscriber implements Subscriber, Subscription {
        final Subscriber actual;
        final long index;
        final T defaultValue;
        
        Subscription s;
        
        long count;
        
        boolean done;
        
        public ElementAtSubscriber(Subscriber actual, long index, T defaultValue) {
            this.actual = actual;
            this.index = index;
            this.defaultValue = defaultValue;
        }
        
        @Override
        public void onSubscribe(Subscription s) {
            if (this.s != null) {
                s.cancel();
                RxJavaPlugins.onError(new IllegalStateException("Subscription already set!"));
                return;
            }
            this.s = s;
            actual.onSubscribe(this);
        }
        
        @Override
        public void onNext(T t) {
            if (done) {
                return;
            }
            long c = count;
            if (c == index) {
                done = true;
                s.cancel();
                actual.onNext(t);
                actual.onComplete();
                return;
            }
            count = c + 1;
        }
        
        @Override
        public void onError(Throwable t) {
            if (done) {
                return;
            }
            done = true;
            actual.onError(t);
        }
        
        @Override
        public void onComplete() {
            if (index <= count && !done) {
                done = true;
                T v = defaultValue;
                if (v == null) {
                    actual.onError(new IndexOutOfBoundsException());
                } else {
                    actual.onNext(v);
                    actual.onComplete();
                }
            }
        }
        
        @Override
        public void request(long n) {
            if (n <= 0) {
                RxJavaPlugins.onError(new IllegalArgumentException("n > required but it was " + n));
                return;
            }
            s.request(Long.MAX_VALUE);
        }
        
        @Override
        public void cancel() {
            s.cancel();
        }
    }
}