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;
  
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.PlaybackParameters;
  
  /**
   * A {@link MediaClock} whose position advances with real time based on the playback parameters when
   * started.
   */
  public final class StandaloneMediaClock implements MediaClock {
  
    private final Clock clock;
  
    private boolean started;
    private long baseUs;
    private long baseElapsedMs;
    private PlaybackParameters playbackParameters;
  
    /**
     * Creates a new standalone media clock using the given {@link Clock} implementation.
     *
     * @param clock A {@link Clock}.
     */
    public StandaloneMediaClock(Clock clock) {
      this.clock = clock;
      this.playbackParameters = PlaybackParameters.DEFAULT;
    }
  
    /**
     * Starts the clock. Does nothing if the clock is already started.
     */
    public void start() {
      if (!started) {
        baseElapsedMs = clock.elapsedRealtime();
        started = true;
      }
    }
  
    /**
     * Stops the clock. Does nothing if the clock is already stopped.
     */
    public void stop() {
      if (started) {
        resetPosition(getPositionUs());
        started = false;
      }
    }
  
    /**
     * Resets the clock's position.
     *
     * @param positionUs The position to set in microseconds.
     */
    public void resetPosition(long positionUs) {
      baseUs = positionUs;
      if (started) {
        baseElapsedMs = clock.elapsedRealtime();
      }
    }
  
    @Override
    public long getPositionUs() {
      long positionUs = baseUs;
      if (started) {
        long elapsedSinceBaseMs = clock.elapsedRealtime() - baseElapsedMs;
        if (playbackParameters.speed == 1f) {
          positionUs += C.msToUs(elapsedSinceBaseMs);
        } else {
          positionUs += playbackParameters.getMediaTimeUsForPlayoutTimeMs(elapsedSinceBaseMs);
        }
      }
      return positionUs;
    }
  
    @Override
    public PlaybackParameters setPlaybackParameters(PlaybackParameters playbackParameters) {
      // Store the current position as the new base, in case the playback speed has changed.
      if (started) {
        resetPosition(getPositionUs());
      }
      this.playbackParameters = playbackParameters;
      return playbackParameters;
    }
  
    @Override
    public PlaybackParameters getPlaybackParameters() {
      return playbackParameters;
    }
  
  }
  