hu.akarnokd.rxjava2.interop.ZeroOneIterator Maven / Gradle / Ivy

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/*
 * Copyright 2016 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.interop;

import java.util.*;
import java.util.concurrent.CountDownLatch;
import java.util.stream.*;

import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.util.ExceptionHelper;

/**
 * Iterator that emits 0 or 1 values from a reactive source of Single, Maybe or Completable.
 *
 * @param  the value type
 */
final class ZeroOneIterator extends CountDownLatch implements Iterator, Disposable, MaybeObserver,
SingleObserver, CompletableObserver {

    T value;

    Throwable error;

    Disposable d;
    
    volatile boolean disposed;
    
    ZeroOneIterator() {
        super(1);
    }

    @Override
    public boolean hasNext() {
        if (getCount() != 0) {
            try {
                await();
            } catch (InterruptedException ex) {
                dispose();
                throw ExceptionHelper.wrapOrThrow(ex);
            }
        }
        Throwable ex = error;
        if (ex != null) {
            throw ExceptionHelper.wrapOrThrow(ex);
        }
        return value != null;
    }
    
    @Override
    public T next() {
        if (hasNext()) {
            T v = value;
            value = null;
            return v;
        }
        throw new NoSuchElementException();
    }

    @Override
    public void onSubscribe(Disposable d) {
        if (DisposableHelper.validate(this.d, d)) {
            this.d = d;
            if (disposed) {
                d.dispose();
            }
        }
    }
    
    @Override
    public void onSuccess(T value) {
        this.value = value;
        countDown();
    }
    
    @Override
    public void onError(Throwable e) {
        this.error = e;
        countDown();
    }
    
    @Override
    public void onComplete() {
        countDown();
    }
    
    @Override
    public void dispose() {
        disposed = true;
        Disposable d = this.d;
        if (d != null) {
            d.dispose();
        }
    }
    
    @Override
    public boolean isDisposed() {
        return disposed;
    }

    /**
     * Creates a Stream from an Iterator which also calls dispose() when closed.
     * @param  the value type
     * @param it the source iterator
     * @return the new Stream instance
     */
    public static  Stream toStream(Iterator it) {
        Stream s = StreamSupport.stream(Spliterators.spliterator(it, 0, 0), false);

        return s.onClose(() -> ((Disposable)it).dispose());
    }
}