core/core/src/main/java/androidx/core/provider/SelfDestructiveThread.java - platform/frameworks/support - Git at Google

 /*
  * 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 androidx.core.provider;


 import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;

 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.Message;

 import androidx.annotation.GuardedBy;
 import androidx.annotation.RestrictTo;
 import androidx.annotation.VisibleForTesting;

 import java.util.concurrent.Callable;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicReference;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.ReentrantLock;

 /**
  * Background thread which is destructed after certain period after all pending activities are
  * finished.
  * @hide
  */
 @RestrictTo(LIBRARY_GROUP_PREFIX)
 public class SelfDestructiveThread {
     private final Object mLock = new Object();

     @GuardedBy("mLock")
     private HandlerThread mThread;

     @GuardedBy("mLock")
     private Handler mHandler;

     @GuardedBy("mLock")
     private int mGeneration;  // The thread generation. Only for testing purpose.

     private static final int MSG_INVOKE_RUNNABLE = 1;
     private static final int MSG_DESTRUCTION = 0;

     private Handler.Callback mCallback = new Handler.Callback() {
         @Override
         public boolean handleMessage(Message msg) {
             switch (msg.what) {
                 case MSG_INVOKE_RUNNABLE:
                     onInvokeRunnable((Runnable) msg.obj);
                     return true;
                 case MSG_DESTRUCTION:
                     onDestruction();
                     return true;
             }
             return true;
         }
     };

     // Milliseconds the thread will be destructed after the last activity.
     private final int mDestructAfterMillisec;
     private final int mPriority;  // The priority of the thread.
     private final String mThreadName;  // The name of the thread.

     public SelfDestructiveThread(
             String threadName, int priority, int destructAfterMillisec) {
         mThreadName = threadName;
         mPriority = priority;
         mDestructAfterMillisec = destructAfterMillisec;
         mGeneration = 0;
     }

     /**
      * Returns true if the thread is alive.
      */
     @VisibleForTesting
     public boolean isRunning() {
         synchronized (mLock) {
             return mThread != null;
         }
     }

     /**
      * Returns the thread generation.
      */
     @VisibleForTesting
     public int getGeneration() {
         synchronized (mLock) {
             return mGeneration;
         }
     }

     private void post(Runnable runnable) {
         synchronized (mLock) {
             if (mThread == null) {
                 mThread = new HandlerThread(mThreadName, mPriority);
                 mThread.start();
                 mHandler = new Handler(mThread.getLooper(), mCallback);
                 mGeneration++;
             }
             mHandler.removeMessages(MSG_DESTRUCTION);
             mHandler.sendMessage(mHandler.obtainMessage(MSG_INVOKE_RUNNABLE, runnable));
         }
     }

     /**
      * Reply callback for postAndReply
      *
      * @param <T> A type which will be received as the argument.
      */
     public interface ReplyCallback<T> {
         /**
          * Called when the task was finished.
          */
         void onReply(T value);
     }

     /**
      * Execute the specific callable object on this thread and call the reply callback on the
      * calling thread once it finishes.
      */
     @SuppressWarnings("deprecation")
     public <T> void postAndReply(final Callable<T> callable, final ReplyCallback<T> reply) {
         final Handler callingHandler = new Handler();
         post(new Runnable() {
             @Override
             public void run() {
                 T t;
                 try {
                     t = callable.call();
                 } catch (Exception e) {
                     t = null;
                 }
                 final T result = t;
                 callingHandler.post(new Runnable() {
                     @Override
                     public void run() {
                         reply.onReply(result);
                     }
                 });
             }
         });
     }

     /**
      * Execute the specified callable object on this thread and returns the returned value to the
      * caller.
      *
      * If the execution takes longer time than specified timeout duration, this function throws
      * InterruptedException.
      */
     public <T> T postAndWait(final Callable<T> callable, int timeoutMillis)
             throws InterruptedException {
         final ReentrantLock lock = new ReentrantLock();
         final Condition cond = lock.newCondition();

         final AtomicReference<T> holder = new AtomicReference<>();
         final AtomicBoolean running = new AtomicBoolean(true);
         post(new Runnable() {
             @Override
             public void run() {
                 try {
                     holder.set(callable.call());
                 } catch (Exception e) {
                     // Do nothing.
                 }
                 lock.lock();
                 try {
                     running.set(false);
                     cond.signal();
                 } finally {
                     lock.unlock();
                 }
             }
         });

         lock.lock();
         try {
             if (!running.get()) {
                 return holder.get();  // already finished.
             }
             long remaining = TimeUnit.MILLISECONDS.toNanos(timeoutMillis);
             for (;;) {
                 try {
                     remaining = cond.awaitNanos(remaining);
                 } catch (InterruptedException e) {
                     // ignore
                 }
                 if (!running.get()) {
                     return holder.get();  // Successfully finished.
                 }
                 if (remaining <= 0) {
                     throw new InterruptedException("timeout");  // Timeout
                 }
             }
         } finally {
             lock.unlock();
         }
     }

     void onInvokeRunnable(Runnable runnable) {
         runnable.run();
         synchronized (mLock) {
             mHandler.removeMessages(MSG_DESTRUCTION);
             mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_DESTRUCTION),
                     mDestructAfterMillisec);
         }
     }

     void onDestruction() {
         synchronized (mLock) {
             if (mHandler.hasMessages(MSG_INVOKE_RUNNABLE)) {
                 // This happens if post() is called after onDestruction and before synchronization
                 // block.
                 return;
             }
             mThread.quit();
             mThread = null;
             mHandler = null;
         }
     }
 }
	/*
	* 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 androidx.core.provider;


	import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP_PREFIX;

	import android.os.Handler;
	import android.os.HandlerThread;
	import android.os.Message;

	import androidx.annotation.GuardedBy;
	import androidx.annotation.RestrictTo;
	import androidx.annotation.VisibleForTesting;

	import java.util.concurrent.Callable;
	import java.util.concurrent.TimeUnit;
	import java.util.concurrent.atomic.AtomicBoolean;
	import java.util.concurrent.atomic.AtomicReference;
	import java.util.concurrent.locks.Condition;
	import java.util.concurrent.locks.ReentrantLock;

	/**
	* Background thread which is destructed after certain period after all pending activities are
	* finished.
	* @hide
	*/
	@RestrictTo(LIBRARY_GROUP_PREFIX)
	public class SelfDestructiveThread {
	private final Object mLock = new Object();

	@GuardedBy("mLock")
	private HandlerThread mThread;

	@GuardedBy("mLock")
	private Handler mHandler;

	@GuardedBy("mLock")
	private int mGeneration; // The thread generation. Only for testing purpose.

	private static final int MSG_INVOKE_RUNNABLE = 1;
	private static final int MSG_DESTRUCTION = 0;

	private Handler.Callback mCallback = new Handler.Callback() {
	@Override
	public boolean handleMessage(Message msg) {
	switch (msg.what) {
	case MSG_INVOKE_RUNNABLE:
	onInvokeRunnable((Runnable) msg.obj);
	return true;
	case MSG_DESTRUCTION:
	onDestruction();
	return true;
	}
	return true;
	}
	};

	// Milliseconds the thread will be destructed after the last activity.
	private final int mDestructAfterMillisec;
	private final int mPriority; // The priority of the thread.
	private final String mThreadName; // The name of the thread.

	public SelfDestructiveThread(
	String threadName, int priority, int destructAfterMillisec) {
	mThreadName = threadName;
	mPriority = priority;
	mDestructAfterMillisec = destructAfterMillisec;
	mGeneration = 0;
	}

	/**
	* Returns true if the thread is alive.
	*/
	@VisibleForTesting
	public boolean isRunning() {
	synchronized (mLock) {
	return mThread != null;
	}
	}

	/**
	* Returns the thread generation.
	*/
	@VisibleForTesting
	public int getGeneration() {
	synchronized (mLock) {
	return mGeneration;
	}
	}

	private void post(Runnable runnable) {
	synchronized (mLock) {
	if (mThread == null) {
	mThread = new HandlerThread(mThreadName, mPriority);
	mThread.start();
	mHandler = new Handler(mThread.getLooper(), mCallback);
	mGeneration++;
	}
	mHandler.removeMessages(MSG_DESTRUCTION);
	mHandler.sendMessage(mHandler.obtainMessage(MSG_INVOKE_RUNNABLE, runnable));
	}
	}

	/**
	* Reply callback for postAndReply
	*
	* @param <T> A type which will be received as the argument.
	*/
	public interface ReplyCallback<T> {
	/**
	* Called when the task was finished.
	*/
	void onReply(T value);
	}

	/**
	* Execute the specific callable object on this thread and call the reply callback on the
	* calling thread once it finishes.
	*/
	@SuppressWarnings("deprecation")
	public <T> void postAndReply(final Callable<T> callable, final ReplyCallback<T> reply) {
	final Handler callingHandler = new Handler();
	post(new Runnable() {
	@Override
	public void run() {
	T t;
	try {
	t = callable.call();
	} catch (Exception e) {
	t = null;
	}
	final T result = t;
	callingHandler.post(new Runnable() {
	@Override
	public void run() {
	reply.onReply(result);
	}
	});
	}
	});
	}

	/**
	* Execute the specified callable object on this thread and returns the returned value to the
	* caller.
	*
	* If the execution takes longer time than specified timeout duration, this function throws
	* InterruptedException.
	*/
	public <T> T postAndWait(final Callable<T> callable, int timeoutMillis)
	throws InterruptedException {
	final ReentrantLock lock = new ReentrantLock();
	final Condition cond = lock.newCondition();

	final AtomicReference<T> holder = new AtomicReference<>();
	final AtomicBoolean running = new AtomicBoolean(true);
	post(new Runnable() {
	@Override
	public void run() {
	try {
	holder.set(callable.call());
	} catch (Exception e) {
	// Do nothing.
	}
	lock.lock();
	try {
	running.set(false);
	cond.signal();
	} finally {
	lock.unlock();
	}
	}
	});

	lock.lock();
	try {
	if (!running.get()) {
	return holder.get(); // already finished.
	}
	long remaining = TimeUnit.MILLISECONDS.toNanos(timeoutMillis);
	for (;;) {
	try {
	remaining = cond.awaitNanos(remaining);
	} catch (InterruptedException e) {
	// ignore
	}
	if (!running.get()) {
	return holder.get(); // Successfully finished.
	}
	if (remaining <= 0) {
	throw new InterruptedException("timeout"); // Timeout
	}
	}
	} finally {
	lock.unlock();
	}
	}

	void onInvokeRunnable(Runnable runnable) {
	runnable.run();
	synchronized (mLock) {
	mHandler.removeMessages(MSG_DESTRUCTION);
	mHandler.sendMessageDelayed(mHandler.obtainMessage(MSG_DESTRUCTION),
	mDestructAfterMillisec);
	}
	}

	void onDestruction() {
	synchronized (mLock) {
	if (mHandler.hasMessages(MSG_INVOKE_RUNNABLE)) {
	// This happens if post() is called after onDestruction and before synchronization
	// block.
	return;
	}
	mThread.quit();
	mThread = null;
	mHandler = null;
	}
	}
	}