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Automatic binding+disposal of RxJava 2 streams.

There is a newer version: 1.4.1

/*
 * 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 com.uber.autodispose;

import io.reactivex.exceptions.CompositeException;
import java.util.concurrent.atomic.AtomicReference;
import javax.annotation.Nullable;

/**
 * Terminal atomics for Throwable containers.
 */
final class ExceptionHelper {

  /** Utility class. */
  private ExceptionHelper() {
    throw new IllegalStateException("No instances!");
  }

  /**
   * A singleton instance of a Throwable indicating a terminal state for exceptions,
   * don't leak this.
   */
  public static final Throwable TERMINATED = new Termination();

  public static boolean addThrowable(AtomicReference field, Throwable exception) {
    for (; ; ) {
      Throwable current = field.get();

      if (current == TERMINATED) {
        return false;
      }

      Throwable update;
      if (current == null) {
        update = exception;
      } else {
        update = new CompositeException(current, exception);
      }

      if (field.compareAndSet(current, update)) {
        return true;
      }
    }
  }

  @Nullable
  public static Throwable terminate(AtomicReference field) {
    Throwable current = field.get();
    if (current != TERMINATED) {
      current = field.getAndSet(TERMINATED);
    }
    return current;
  }

  static final class Termination extends Throwable {

    Termination() {
      super("No further exceptions");
    }

    @Override public synchronized Throwable fillInStackTrace() {
      return this;
    }
  }
}