AsyncDownstream.java

/*
 * Copyright 2017 the original author or authors.
 *
 * 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 ratpack.exec.internal;

import ratpack.exec.Downstream;
import ratpack.exec.OverlappingExecutionException;

import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;

class AsyncDownstream<T> implements Downstream<T> {

  @SuppressWarnings("rawtypes")
  private static final AtomicIntegerFieldUpdater<AsyncDownstream> FIRED_UPDATER = AtomicIntegerFieldUpdater.newUpdater(AsyncDownstream.class, "fired");

  @SuppressWarnings("unused")
  volatile int fired;

  private final Continuation continuation;
  private final Downstream<? super T> downstream;

  AsyncDownstream(Continuation continuation, Downstream<? super T> downstream) {
    this.continuation = continuation;
    this.downstream = downstream;
  }

  boolean fire() {
    return FIRED_UPDATER.compareAndSet(this, 0, 1);
  }

  @Override
  public void error(Throwable throwable) {
    if (fire()) {
      continuation.resume(() -> downstream.error(throwable));
    } else {
      DefaultExecution.LOGGER.error("", new OverlappingExecutionException("promise already fulfilled", throwable));
    }
  }

  @Override
  public void success(T value) {
    if (fire()) {
      continuation.resume(() -> downstream.success(value));
    } else {
      DefaultExecution.LOGGER.error("", new OverlappingExecutionException("promise already fulfilled"));
    }
  }

  @Override
  public void complete() {
    if (fire()) {
      continuation.resume(downstream::complete);
    } else {
      DefaultExecution.LOGGER.error("", new OverlappingExecutionException("promise already fulfilled"));
    }
  }
}