com.google.gapid.rpc.SingleInFlight.java Source code

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Here is the source code for com.google.gapid.rpc.SingleInFlight.java

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/*
 * Copyright (C) 2017 Google 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 com.google.gapid.rpc;

import com.google.common.base.Preconditions;
import com.google.common.util.concurrent.ListenableFuture;

import java.util.concurrent.atomic.AtomicReference;

public class SingleInFlight {
    private final AtomicReference<Context> active = new AtomicReference<Context>();

    public SingleInFlight() {
    }

    public Context start() {
        Context result = new Context() {
            private ListenableFuture<?> future = null;
            private boolean cancelled = false;

            @Override
            public synchronized <T> void listen(ListenableFuture<T> f, Rpc.Callback<T> callback) {
                Preconditions.checkState(future == null);
                if (cancelled) {
                    future.cancel(true);
                }
                future = f;
                Rpc.listen(f, callback);
            }

            @Override
            public synchronized void cancel() {
                cancelled = true;
                if (future != null) {
                    future.cancel(true);
                }
            }
        };
        Context previous = active.getAndSet(result);
        if (previous != null) {
            previous.cancel();
        }
        return result;
    }

    public interface Context {
        public <T> void listen(ListenableFuture<T> future, Rpc.Callback<T> callback);

        public void cancel();
    }
}