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.google.android.exoplayer2.util;
  
  /**
   * An interruptible condition variable whose {@link #open()} and {@link #close()} methods return
   * whether they resulted in a change of state.
   */
  public final class ConditionVariable {
  
    private boolean isOpen;
  
    /**
     * Opens the condition and releases all threads that are blocked.
     *
     * @return True if the condition variable was opened. False if it was already open.
     */
    public synchronized boolean open() {
      if (isOpen) {
        return false;
      }
      isOpen = true;
      notifyAll();
      return true;
    }
  
    /**
     * Closes the condition.
     *
     * @return True if the condition variable was closed. False if it was already closed.
     */
    public synchronized boolean close() {
      boolean wasOpen = isOpen;
      isOpen = false;
      return wasOpen;
    }
  
    /**
     * Blocks until the condition is opened.
     *
     * @throws InterruptedException If the thread is interrupted.
     */
    public synchronized void block() throws InterruptedException {
      while (!isOpen) {
        wait();
      }
    }
  
    /**
     * Blocks until the condition is opened or until {@code timeout} milliseconds have passed.
     *
     * @param timeout The maximum time to wait in milliseconds.
     * @return True if the condition was opened, false if the call returns because of the timeout.
     * @throws InterruptedException If the thread is interrupted.
     */
    public synchronized boolean block(long timeout) throws InterruptedException {
      long now = android.os.SystemClock.elapsedRealtime();
      long end = now + timeout;
      while (!isOpen && now < end) {
        wait(end - now);
        now = android.os.SystemClock.elapsedRealtime();
      }
      return isOpen;
    }
  
  }
  