Copyright (c) 2016-present, RxJava Contributors.
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.
/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * 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 io.reactivex.internal.subscriptions;

import java.util.concurrent.atomic.AtomicReferenceArray;

import org.reactivestreams.Subscription;

import io.reactivex.disposables.Disposable;

A composite disposable with a fixed number of slots.
Note that since the implementation leaks the methods of AtomicReferenceArray, one must be
careful to only call setResource, replaceResource and dispose on it. All other methods may lead to undefined behavior
and should be used by internal means only.
/**
 * A composite disposable with a fixed number of slots.
 *
 * <p>Note that since the implementation leaks the methods of AtomicReferenceArray, one must be
 * careful to only call setResource, replaceResource and dispose on it. All other methods may lead to undefined behavior
 * and should be used by internal means only.
 */
public final class ArrayCompositeSubscription extends AtomicReferenceArray<Subscription> implements Disposable {

    private static final long serialVersionUID = 2746389416410565408L;

    public ArrayCompositeSubscription(int capacity) {
        super(capacity);
    }

    
Sets the resource at the specified index and disposes the old resource.
Params:
index – the index of the resource to set
resource – the new resource
Returns:
true if the resource has ben set, false if the composite has been disposed/**
     * Sets the resource at the specified index and disposes the old resource.
     * @param index the index of the resource to set
     * @param resource the new resource
     * @return true if the resource has ben set, false if the composite has been disposed
     */
    public boolean setResource(int index, Subscription resource) {
        for (;;) {
            Subscription o = get(index);
            if (o == SubscriptionHelper.CANCELLED) {
                if (resource != null) {
                    resource.cancel();
                }
                return false;
            }
            if (compareAndSet(index, o, resource)) {
                if (o != null) {
                    o.cancel();
                }
                return true;
            }
        }
    }

    
Replaces the resource at the specified index and returns the old resource.
Params:
index – the index of the resource to replace
resource – the new resource
Returns:
the old resource, can be null/**
     * Replaces the resource at the specified index and returns the old resource.
     * @param index the index of the resource to replace
     * @param resource the new resource
     * @return the old resource, can be null
     */
    public Subscription replaceResource(int index, Subscription resource) {
        for (;;) {
            Subscription o = get(index);
            if (o == SubscriptionHelper.CANCELLED) {
                if (resource != null) {
                    resource.cancel();
                }
                return null;
            }
            if (compareAndSet(index, o, resource)) {
                return o;
            }
        }
    }

    @Override
    public void dispose() {
        if (get(0) != SubscriptionHelper.CANCELLED) {
            int s = length();
            for (int i = 0; i < s; i++) {
                Subscription o = get(i);
                if (o != SubscriptionHelper.CANCELLED) {
                    o = getAndSet(i, SubscriptionHelper.CANCELLED);
                    if (o != SubscriptionHelper.CANCELLED && o != null) {
                        o.cancel();
                    }
                }
            }
        }
    }

    @Override
    public boolean isDisposed() {
        return get(0) == SubscriptionHelper.CANCELLED;
    }
}