content: /*
   * Copyright (C) 2007 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 com.android.server;
  
  import android.os.SystemClock;
  
  import android.annotation.UnsupportedAppUsage;
  import android.os.ConditionVariable;
  
  /**
   * Utility class that you can call on with a timeout, and get called back
   * after a given time, dealing correctly with restarting the timeout.
   *
   * <p>For example, this class is used by the android.os.Vibrator class.
   */
  abstract class ResettableTimeout
  {
      /**
       * Override this do what you need to do when it's starting
       * This is called with the monitor on this method held, so be careful.
       *
       * @param alreadyOn is true if it's currently running
       */
      public abstract void on(boolean alreadyOn);
  
      /**
       * Override this to do what you need to do when it's stopping.
       * This is called with the monitor on this method held, so be careful.
       */
      public abstract void off();
  
      /**
       * Does the following steps.
       * <p>1. Call on()</p>
       * <p>2. Start the timer.</p>
       * <p>3. At the timeout, calls off()<p>
       * <p>If you call this again, the timeout is reset to the new one</p>
       */
      public void go(long milliseconds)
      {
          synchronized (this) {
              mOffAt = SystemClock.uptimeMillis() + milliseconds;
  
              boolean alreadyOn;
  
              // By starting the thread first and waiting, we ensure that if the
              // thread to stop it can't start, we don't turn the vibrator on
              // forever.  This still isn't really sufficient, because we don't
              // have another processor watching us.  We really should have a
              // service for this in case our process crashes.
              if (mThread == null) {
                  alreadyOn = false;
                  mLock.close();
                  mThread = new T();
                  mThread.start();
                  mLock.block();
                  mOffCalled = false;
              } else {
                  alreadyOn = true;
                  // poke the thread so it gets the new timeout.
                  mThread.interrupt();
              }
              on(alreadyOn);
          }
      }
  
      /**
       * Cancel the timeout and call off now.
       */
      public void cancel()
      {
          synchronized (this) {
              mOffAt = 0;
              if (mThread != null) {
                  mThread.interrupt();
                  mThread = null;
              }
              if (!mOffCalled) {
                  mOffCalled = true;
                  off();
              }
          }
      }
  
      private class T extends Thread
      {
          public void run()
          {
              mLock.open();
              while (true) {
                  long diff;
                  synchronized (this) {
                      diff = mOffAt - SystemClock.uptimeMillis();
                      if (diff <= 0) {
                          mOffCalled = true;
                          off();
                          mThread = null;
                          break;
                      }
                  }
                  try {
                      sleep(diff);
                  }
                  catch (InterruptedException e) {
                  }
              }
          }
      }
  
      @UnsupportedAppUsage
      private ConditionVariable mLock = new ConditionVariable();
  
      // turn it off at this time.
      @UnsupportedAppUsage
      private volatile long mOffAt;
      private volatile boolean mOffCalled;
  
      private Thread mThread;
  
  }
  
  