BandwidthMeter.java
/*
* 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 androidx.media3.exoplayer.upstream;
import android.os.Handler;
import androidx.annotation.Nullable;
import androidx.media3.common.C;
import androidx.media3.common.util.Assertions;
import androidx.media3.common.util.UnstableApi;
import androidx.media3.datasource.TransferListener;
import java.util.concurrent.CopyOnWriteArrayList;
/** Provides estimates of the currently available bandwidth. */
@UnstableApi
public interface BandwidthMeter {
/** A listener of {@link BandwidthMeter} events. */
interface EventListener {
/**
* Called periodically to indicate that bytes have been transferred or the estimated bitrate has
* changed.
*
* <p>Note: The estimated bitrate is typically derived from more information than just {@code
* bytesTransferred} and {@code elapsedMs}.
*
* @param elapsedMs The time taken to transfer {@code bytesTransferred}, in milliseconds. This
* is at most the elapsed time since the last callback, but may be less if there were
* periods during which data was not being transferred.
* @param bytesTransferred The number of bytes transferred since the last callback.
* @param bitrateEstimate The estimated bitrate in bits/sec.
*/
void onBandwidthSample(int elapsedMs, long bytesTransferred, long bitrateEstimate);
/** Event dispatcher which allows listener registration. */
final class EventDispatcher {
private final CopyOnWriteArrayList<HandlerAndListener> listeners;
/** Creates an event dispatcher. */
public EventDispatcher() {
listeners = new CopyOnWriteArrayList<>();
}
/** Adds a listener to the event dispatcher. */
public void addListener(Handler eventHandler, BandwidthMeter.EventListener eventListener) {
Assertions.checkNotNull(eventHandler);
Assertions.checkNotNull(eventListener);
removeListener(eventListener);
listeners.add(new HandlerAndListener(eventHandler, eventListener));
}
/** Removes a listener from the event dispatcher. */
public void removeListener(BandwidthMeter.EventListener eventListener) {
for (HandlerAndListener handlerAndListener : listeners) {
if (handlerAndListener.listener == eventListener) {
handlerAndListener.release();
listeners.remove(handlerAndListener);
}
}
}
public void bandwidthSample(int elapsedMs, long bytesTransferred, long bitrateEstimate) {
for (HandlerAndListener handlerAndListener : listeners) {
if (!handlerAndListener.released) {
handlerAndListener.handler.post(
() ->
handlerAndListener.listener.onBandwidthSample(
elapsedMs, bytesTransferred, bitrateEstimate));
}
}
}
private static final class HandlerAndListener {
private final Handler handler;
private final BandwidthMeter.EventListener listener;
private boolean released;
public HandlerAndListener(Handler handler, BandwidthMeter.EventListener eventListener) {
this.handler = handler;
this.listener = eventListener;
}
public void release() {
released = true;
}
}
}
}
/** Returns the estimated bitrate. */
long getBitrateEstimate();
/**
* Returns the estimated time to first byte, in microseconds, or {@link C#TIME_UNSET} if no
* estimate is available.
*/
default long getTimeToFirstByteEstimateUs() {
return C.TIME_UNSET;
}
/**
* Returns the {@link TransferListener} that this instance uses to gather bandwidth information
* from data transfers. May be null if the implementation does not listen to data transfers.
*/
@Nullable
TransferListener getTransferListener();
/**
* Adds an {@link EventListener}.
*
* @param eventHandler A handler for events.
* @param eventListener A listener of events.
*/
void addEventListener(Handler eventHandler, EventListener eventListener);
/**
* Removes an {@link EventListener}.
*
* @param eventListener The listener to be removed.
*/
void removeEventListener(EventListener eventListener);
}