content: /*
   * Copyright (C) 2016 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.internal.util;
  
  import android.os.Process;
  import android.util.Slog;
  
  import java.util.concurrent.CountDownLatch;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.concurrent.ThreadFactory;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicInteger;
  
  /**
   * Utility methods for common functionality using java.util.concurrent package
   *
   * @hide
   */
  public class ConcurrentUtils {
  
      private ConcurrentUtils() {
      }
  
      /**
       * Creates a thread pool using
       * {@link java.util.concurrent.Executors#newFixedThreadPool(int, ThreadFactory)}
       *
       * @param nThreads the number of threads in the pool
       * @param poolName base name of the threads in the pool
       * @param linuxThreadPriority a Linux priority level. see {@link Process#setThreadPriority(int)}
       * @return the newly created thread pool
       */
      public static ExecutorService newFixedThreadPool(int nThreads, String poolName,
              int linuxThreadPriority) {
          return Executors.newFixedThreadPool(nThreads,
                  new ThreadFactory() {
                      private final AtomicInteger threadNum = new AtomicInteger(0);
  
                      @Override
                      public Thread newThread(final Runnable r) {
                          return new Thread(poolName + threadNum.incrementAndGet()) {
                              @Override
                              public void run() {
                                  Process.setThreadPriority(linuxThreadPriority);
                                  r.run();
                              }
                          };
                      }
                  });
      }
  
      /**
       * Waits if necessary for the computation to complete, and then retrieves its result.
       * <p>If {@code InterruptedException} occurs, this method will interrupt the current thread
       * and throw {@code IllegalStateException}</p>
       *
       * @param future future to wait for result
       * @param description short description of the operation
       * @return the computed result
       * @throws IllegalStateException if interrupted during wait
       * @throws RuntimeException if an error occurs while waiting for {@link Future#get()}
       * @see Future#get()
       */
      public static <T> T waitForFutureNoInterrupt(Future<T> future, String description) {
          try {
              return future.get();
          } catch (InterruptedException e) {
              Thread.currentThread().interrupt();
              throw new IllegalStateException(description + " interrupted");
          } catch (ExecutionException e) {
              throw new RuntimeException(description + " failed", e);
          }
      }
  
      /**
       * Waits for {@link CountDownLatch#countDown()} to be called on the {@param countDownLatch}.
       * <p>If {@link CountDownLatch#countDown()} doesn't occur within {@param timeoutMs}, this
       * method will throw {@code IllegalStateException}
       * <p>If {@code InterruptedException} occurs, this method will interrupt the current thread
       * and throw {@code IllegalStateException}
       *
       * @param countDownLatch the CountDownLatch which {@link CountDownLatch#countDown()} is
       *                       being waited on.
       * @param timeoutMs the maximum time waited for {@link CountDownLatch#countDown()}
       * @param description a short description of the operation
       */
      public static void waitForCountDownNoInterrupt(CountDownLatch countDownLatch, long timeoutMs,
              String description) {
          try {
              if (!countDownLatch.await(timeoutMs, TimeUnit.MILLISECONDS)) {
                  throw new IllegalStateException(description + " timed out.");
              }
          } catch (InterruptedException e) {
              Thread.currentThread().interrupt();
              throw new IllegalStateException(description + " interrupted.");
          }
      }
  
      /**
       * Calls {@link Slog#wtf} if a given lock is held.
       */
      public static void wtfIfLockHeld(String tag, Object lock) {
          if (Thread.holdsLock(lock)) {
              Slog.wtf(tag, "Lock mustn't be held");
          }
      }
  
      /**
       * Calls {@link Slog#wtf} if a given lock is not held.
       */
      public static void wtfIfLockNotHeld(String tag, Object lock) {
          if (!Thread.holdsLock(lock)) {
              Slog.wtf(tag, "Lock must be held");
          }
      }
  }
  