sshd-common/src/main/java/org/apache/sshd/common/util/closeable/ParallelCloseable.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you 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 org.apache.sshd.common.util.closeable;

import java.util.Collections;
import java.util.concurrent.atomic.AtomicInteger;

import org.apache.sshd.common.Closeable;
import org.apache.sshd.common.future.CloseFuture;
import org.apache.sshd.common.future.SshFutureListener;

/**
 * Waits for a group of {@link Closeable}s to complete in any order, then signals the completion by setting the
 * "parent" future as closed
 *
 * @author <a href="mailto:dev@mina.apache.org">Apache MINA SSHD Project</a>
 */
public class ParallelCloseable extends SimpleCloseable {
    private final Iterable<? extends Closeable> closeables;

    public ParallelCloseable(Object id, Object lock, Iterable<? extends Closeable> closeables) {
        super(id, lock);
        this.closeables = (closeables == null) ? Collections.emptyList() : closeables;
    }

    @Override
    protected void doClose(boolean immediately) {
        AtomicInteger count = new AtomicInteger(1);
        boolean traceEnabled = log.isTraceEnabled();
        SshFutureListener<CloseFuture> listener = f -> {
            int pendingCount = count.decrementAndGet();
            if (traceEnabled) {
                log.trace("doClose({}) completed pending: {}", immediately, pendingCount);
            }
            if (pendingCount == 0) {
                future.setClosed();
            }
        };

        for (Closeable c : closeables) {
            if (c == null) {
                continue;
            }

            int pendingCount = count.incrementAndGet();
            if (traceEnabled) {
                log.trace("doClose({}) pending closeables: {}", immediately, pendingCount);
            }
            c.close(immediately).addListener(listener);
        }
        /*
         * Trigger the last "decrementAndGet" so that the future is marked as closed when last "operationComplete" is
         * invoked (which could be this call...)
         */
        listener.operationComplete(null);
    }
}