content: /*
   * Copyright (C) 2014 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.hardware.camera2.legacy;
  
  import android.os.ConditionVariable;
  import android.os.Handler;
  import android.os.HandlerThread;
  import android.os.Looper;
  import android.os.MessageQueue;
  
  public class RequestHandlerThread extends HandlerThread {
  
      /**
       * Ensure that the MessageQueue's idle handler gets run by poking the message queue;
       * normally if the message queue is already idle, the idle handler won't get invoked.
       *
       * <p>Users of this handler thread should ignore this message.</p>
       */
      public final static int MSG_POKE_IDLE_HANDLER = -1;
  
      private final ConditionVariable mStarted = new ConditionVariable(false);
      private final ConditionVariable mIdle = new ConditionVariable(true);
      private Handler.Callback mCallback;
      private volatile Handler mHandler;
  
      public RequestHandlerThread(String name, Handler.Callback callback) {
          super(name, Thread.MAX_PRIORITY);
          mCallback = callback;
      }
  
      @Override
      protected void onLooperPrepared() {
          mHandler = new Handler(getLooper(), mCallback);
          mStarted.open();
      }
  
      // Blocks until thread has started
      public void waitUntilStarted() {
          mStarted.block();
      }
  
      // May return null if the handler is not set up yet.
      public Handler getHandler() {
          return mHandler;
      }
  
      // Blocks until thread has started
      public Handler waitAndGetHandler() {
          waitUntilStarted();
          return getHandler();
      }
  
      // Atomic multi-type message existence check
      public boolean hasAnyMessages(int[] what) {
          synchronized (mHandler.getLooper().getQueue()) {
              for (int i : what) {
                  if (mHandler.hasMessages(i)) {
                      return true;
                  }
              }
          }
          return false;
      }
  
      // Atomic multi-type message remove
      public void removeMessages(int[] what) {
          synchronized (mHandler.getLooper().getQueue()) {
              for (int i : what) {
                  mHandler.removeMessages(i);
              }
          }
      }
  
      private final MessageQueue.IdleHandler mIdleHandler = new MessageQueue.IdleHandler() {
          @Override
          public boolean queueIdle() {
              mIdle.open();
              return false;
          }
      };
  
      // Blocks until thread is idling
      public void waitUntilIdle() {
          Handler handler = waitAndGetHandler();
          MessageQueue queue = handler.getLooper().getQueue();
          if (queue.isIdle()) {
              return;
          }
          mIdle.close();
          queue.addIdleHandler(mIdleHandler);
          // Ensure that the idle handler gets run even if the looper already went idle
          handler.sendEmptyMessage(MSG_POKE_IDLE_HANDLER);
          if (queue.isIdle()) {
              return;
          }
          mIdle.block();
      }
  
  }
  