content: /*
   * 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.beam.sdk.fn.stream;
  
  import org.apache.beam.vendor.grpc.v1p69p0.io.grpc.stub.StreamObserver;
  
  /**
   * A {@link StreamObserver} which provides synchronous access access to an underlying {@link
   * StreamObserver}.
   *
   * <p>The underlying {@link StreamObserver} must not be used by any other clients.
   */
  public class SynchronizedStreamObserver<V> implements StreamObserver<V> {
    private final StreamObserver<V> underlying;
  
    private SynchronizedStreamObserver(StreamObserver<V> underlying) {
      this.underlying = underlying;
    }
  
    /**
     * Create a new {@link SynchronizedStreamObserver} which will delegate all calls to the underlying
     * {@link StreamObserver}, synchronizing access to that observer.
     */
    public static <V> StreamObserver<V> wrapping(StreamObserver<V> underlying) {
      return new SynchronizedStreamObserver<>(underlying);
    }
  
    @Override
    public void onNext(V value) {
      synchronized (underlying) {
        underlying.onNext(value);
      }
    }
  
    @Override
    public synchronized void onError(Throwable t) {
      synchronized (underlying) {
        underlying.onError(t);
      }
    }
  
    @Override
    public synchronized void onCompleted() {
      synchronized (underlying) {
        underlying.onCompleted();
      }
    }
  }
  