content: /*
   * Copyright (C) 2017 The Android Open Source Project
   *
   * 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 android.net.util;
  
  import android.content.BroadcastReceiver;
  import android.content.Context;
  import android.content.Intent;
  import android.content.IntentFilter;
  import android.os.Handler;
  import android.util.Log;
  
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.function.Consumer;
  
  
  /**
   * A utility class that runs the provided callback on the provided handler when
   * intents matching the provided filter arrive. Intents received by a stale
   * receiver are safely ignored.
   *
   * Calls to startListening() and stopListening() must happen on the same thread.
   *
   * @hide
   */
  public class VersionedBroadcastListener {
      private static final boolean DBG = false;
  
      public interface IntentCallback {
          public void run(Intent intent);
      }
  
      private final String mTag;
      private final Context mContext;
      private final Handler mHandler;
      private final IntentFilter mFilter;
      private final Consumer<Intent> mCallback;
      private final AtomicInteger mGenerationNumber;
      private BroadcastReceiver mReceiver;
  
      public VersionedBroadcastListener(String tag, Context ctx, Handler handler,
              IntentFilter filter, Consumer<Intent> callback) {
          mTag = tag;
          mContext = ctx;
          mHandler = handler;
          mFilter = filter;
          mCallback = callback;
          mGenerationNumber = new AtomicInteger(0);
      }
  
      public void startListening() {
          if (DBG) Log.d(mTag, "startListening");
          if (mReceiver != null) return;
  
          mReceiver = new Receiver(mTag, mGenerationNumber, mCallback);
          mContext.registerReceiver(mReceiver, mFilter, null, mHandler);
      }
  
      public void stopListening() {
          if (DBG) Log.d(mTag, "stopListening");
          if (mReceiver == null) return;
  
          mGenerationNumber.incrementAndGet();
          mContext.unregisterReceiver(mReceiver);
          mReceiver = null;
      }
  
      private static class Receiver extends BroadcastReceiver {
          public final String tag;
          public final AtomicInteger atomicGenerationNumber;
          public final Consumer<Intent> callback;
          // Used to verify this receiver is still current.
          public final int generationNumber;
  
          public Receiver(
                  String tag, AtomicInteger atomicGenerationNumber, Consumer<Intent> callback) {
              this.tag = tag;
              this.atomicGenerationNumber = atomicGenerationNumber;
              this.callback = callback;
              generationNumber = atomicGenerationNumber.incrementAndGet();
          }
  
          @Override
          public void onReceive(Context context, Intent intent) {
              final int currentGenerationNumber = atomicGenerationNumber.get();
  
              if (DBG) {
                  Log.d(tag, "receiver generationNumber=" + generationNumber +
                          ", current generationNumber=" + currentGenerationNumber);
              }
              if (generationNumber != currentGenerationNumber) return;
  
              callback.accept(intent);
          }
      }
  }
  