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.upstream;
  
  import android.os.Handler;
  import com.google.android.exoplayer2.util.Assertions;
  import com.google.android.exoplayer2.util.Clock;
  import com.google.android.exoplayer2.util.SlidingPercentile;
  
  /**
   * Estimates bandwidth by listening to data transfers. The bandwidth estimate is calculated using
   * a {@link SlidingPercentile} and is updated each time a transfer ends.
   */
  public final class DefaultBandwidthMeter implements BandwidthMeter, TransferListener<Object> {
  
    /**
     * The default maximum weight for the sliding window.
     */
    public static final int DEFAULT_MAX_WEIGHT = 2000;
  
    private static final int ELAPSED_MILLIS_FOR_ESTIMATE = 2000;
    private static final int BYTES_TRANSFERRED_FOR_ESTIMATE = 512 * 1024;
  
    private final Handler eventHandler;
    private final EventListener eventListener;
    private final SlidingPercentile slidingPercentile;
    private final Clock clock;
  
    private int streamCount;
    private long sampleStartTimeMs;
    private long sampleBytesTransferred;
  
    private long totalElapsedTimeMs;
    private long totalBytesTransferred;
    private long bitrateEstimate;
  
    public DefaultBandwidthMeter() {
      this(null, null);
    }
  
    public DefaultBandwidthMeter(Handler eventHandler, EventListener eventListener) {
      this(eventHandler, eventListener, DEFAULT_MAX_WEIGHT);
    }
  
    public DefaultBandwidthMeter(Handler eventHandler, EventListener eventListener, int maxWeight) {
      this(eventHandler, eventListener, maxWeight, Clock.DEFAULT);
    }
  
    public DefaultBandwidthMeter(Handler eventHandler, EventListener eventListener, int maxWeight,
        Clock clock) {
      this.eventHandler = eventHandler;
      this.eventListener = eventListener;
      this.slidingPercentile = new SlidingPercentile(maxWeight);
      this.clock = clock;
      bitrateEstimate = NO_ESTIMATE;
    }
  
    @Override
    public synchronized long getBitrateEstimate() {
      return bitrateEstimate;
    }
  
    @Override
    public synchronized void onTransferStart(Object source, DataSpec dataSpec) {
      if (streamCount == 0) {
        sampleStartTimeMs = clock.elapsedRealtime();
      }
      streamCount++;
    }
  
    @Override
    public synchronized void onBytesTransferred(Object source, int bytes) {
      sampleBytesTransferred += bytes;
    }
  
    @Override
    public synchronized void onTransferEnd(Object source) {
      Assertions.checkState(streamCount > 0);
      long nowMs = clock.elapsedRealtime();
      int sampleElapsedTimeMs = (int) (nowMs - sampleStartTimeMs);
      totalElapsedTimeMs += sampleElapsedTimeMs;
      totalBytesTransferred += sampleBytesTransferred;
      if (sampleElapsedTimeMs > 0) {
        float bitsPerSecond = (sampleBytesTransferred * 8000) / sampleElapsedTimeMs;
        slidingPercentile.addSample((int) Math.sqrt(sampleBytesTransferred), bitsPerSecond);
        if (totalElapsedTimeMs >= ELAPSED_MILLIS_FOR_ESTIMATE
            || totalBytesTransferred >= BYTES_TRANSFERRED_FOR_ESTIMATE) {
          float bitrateEstimateFloat = slidingPercentile.getPercentile(0.5f);
          bitrateEstimate = Float.isNaN(bitrateEstimateFloat) ? NO_ESTIMATE
              : (long) bitrateEstimateFloat;
        }
      }
      notifyBandwidthSample(sampleElapsedTimeMs, sampleBytesTransferred, bitrateEstimate);
      if (--streamCount > 0) {
        sampleStartTimeMs = nowMs;
      }
      sampleBytesTransferred = 0;
    }
  
    private void notifyBandwidthSample(final int elapsedMs, final long bytes, final long bitrate) {
      if (eventHandler != null && eventListener != null) {
        eventHandler.post(new Runnable()  {
          @Override
          public void run() {
            eventListener.onBandwidthSample(elapsedMs, bytes, bitrate);
          }
        });
      }
    }
  
  }
  