Trim allocator on stop/reset by default

This prevents a large amount of memory from being held
in the case that a player instance is released, but the
application is holding dangling references to the player
that are preventing it from being garbage collected.

Issue: #1855

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=134992945

library/src/main/java/com/google/android/exoplayer2/DefaultLoadControl.java

@@ -68,7 +68,7 @@ public final class DefaultLoadControl implements LoadControl {
    * Constructs a new instance, using the {@code DEFAULT_*} constants defined in this class.
    */
   public DefaultLoadControl() {
-    this(new DefaultAllocator(C.DEFAULT_BUFFER_SEGMENT_SIZE));
+    this(new DefaultAllocator(true, C.DEFAULT_BUFFER_SEGMENT_SIZE));
   }
 
   /**
@@ -104,6 +104,11 @@ public final class DefaultLoadControl implements LoadControl {
     bufferForPlaybackAfterRebufferUs = bufferForPlaybackAfterRebufferMs * 1000L;
   }
 
+  @Override
+  public void onPrepared() {
+    reset(false);
+  }
+
   @Override
   public void onTracksSelected(Renderer[] renderers, TrackGroupArray trackGroups,
       TrackSelections<?> trackSelections) {
@@ -117,9 +122,13 @@ public final class DefaultLoadControl implements LoadControl {
   }
 
   @Override
-  public void onTracksDisabled() {
-    targetBufferSize = 0;
-    isBuffering = false;
+  public void onStopped() {
+    reset(true);
+  }
+
+  @Override
+  public void onReleased() {
+    reset(true);
   }
 
   @Override
@@ -147,4 +156,12 @@ public final class DefaultLoadControl implements LoadControl {
         : (bufferedDurationUs < minBufferUs ? BELOW_LOW_WATERMARK : BETWEEN_WATERMARKS);
   }
 
+  private void reset(boolean resetAllocator) {
+    targetBufferSize = 0;
+    isBuffering = false;
+    if (resetAllocator) {
+      allocator.reset();
+    }
+  }
+
 }

library/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -106,7 +106,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
   @Override
   public void prepare(MediaSource mediaSource, boolean resetPosition) {
     timeline = null;
-    internalPlayer.setMediaSource(mediaSource, resetPosition);
+    internalPlayer.prepare(mediaSource, resetPosition);
   }
 
   @Override

library/src/main/java/com/google/android/exoplayer2/ExoPlayerImplInternal.java

@@ -75,7 +75,7 @@ import java.io.IOException;
   public static final int MSG_ERROR = 6;
 
   // Internal messages
-  private static final int MSG_SET_MEDIA_SOURCE = 0;
+  private static final int MSG_PREPARE = 0;
   private static final int MSG_SET_PLAY_WHEN_READY = 1;
   private static final int MSG_DO_SOME_WORK = 2;
   private static final int MSG_SEEK_TO = 3;
@@ -164,8 +164,8 @@ import java.io.IOException;
     handler = new Handler(internalPlaybackThread.getLooper(), this);
   }
 
-  public void setMediaSource(MediaSource mediaSource, boolean resetPosition) {
-    handler.obtainMessage(MSG_SET_MEDIA_SOURCE, resetPosition ? 1 : 0, 0, mediaSource)
+  public void prepare(MediaSource mediaSource, boolean resetPosition) {
+    handler.obtainMessage(MSG_PREPARE, resetPosition ? 1 : 0, 0, mediaSource)
         .sendToTarget();
   }
 
@@ -253,8 +253,8 @@ import java.io.IOException;
   public boolean handleMessage(Message msg) {
     try {
       switch (msg.what) {
-        case MSG_SET_MEDIA_SOURCE: {
-          setMediaSourceInternal((MediaSource) msg.obj, msg.arg1 != 0);
+        case MSG_PREPARE: {
+          prepareInternal((MediaSource) msg.obj, msg.arg1 != 0);
           return true;
         }
         case MSG_SET_PLAY_WHEN_READY: {
@@ -335,9 +335,10 @@ import java.io.IOException;
     }
   }
 
-  private void setMediaSourceInternal(MediaSource mediaSource, boolean resetPosition)
+  private void prepareInternal(MediaSource mediaSource, boolean resetPosition)
       throws ExoPlaybackException {
     resetInternal();
+    loadControl.onPrepared();
     if (resetPosition) {
       playbackInfo = new PlaybackInfo(0, C.TIME_UNSET);
     }
@@ -597,11 +598,13 @@ import java.io.IOException;
 
   private void stopInternal() {
     resetInternal();
+    loadControl.onStopped();
     setState(ExoPlayer.STATE_IDLE);
   }
 
   private void releaseInternal() {
     resetInternal();
+    loadControl.onReleased();
     setState(ExoPlayer.STATE_IDLE);
     synchronized (this) {
       released = true;
@@ -638,7 +641,6 @@ import java.io.IOException;
     loadingPeriodHolder = null;
     timeline = null;
     bufferAheadPeriodCount = 0;
-    loadControl.onTracksDisabled();
     setIsLoading(false);
   }
 

library/src/main/java/com/google/android/exoplayer2/LoadControl.java

@@ -25,6 +25,11 @@ import com.google.android.exoplayer2.upstream.Allocator;
  */
 public interface LoadControl {
 
+  /**
+   * Called by the player when prepared with a new source.
+   */
+  void onPrepared();
+
   /**
    * Called by the player when a track selection occurs.
    *
@@ -36,9 +41,14 @@ public interface LoadControl {
       TrackSelections<?> trackSelections);
 
   /**
-   * Called by the player when all tracks are disabled.
+   * Called by the player when stopped.
    */
-  void onTracksDisabled();
+  void onStopped();
+
+  /**
+   * Called by the player when released.
+   */
+  void onReleased();
 
   /**
    * Returns the {@link Allocator} that should be used to obtain media buffer allocations.

library/src/main/java/com/google/android/exoplayer2/upstream/DefaultAllocator.java

@@ -26,6 +26,7 @@ public final class DefaultAllocator implements Allocator {
 
   private static final int AVAILABLE_EXTRA_CAPACITY = 100;
 
+  private final boolean trimOnReset;
   private final int individualAllocationSize;
   private final byte[] initialAllocationBlock;
   private final Allocation[] singleAllocationReleaseHolder;
@@ -38,10 +39,12 @@ public final class DefaultAllocator implements Allocator {
   /**
    * Constructs an instance without creating any {@link Allocation}s up front.
    *
+   * @param trimOnReset Whether memory is freed when the allocator is reset. Should be true unless
+   *     the allocator will be re-used by multiple player instances.
    * @param individualAllocationSize The length of each individual {@link Allocation}.
    */
-  public DefaultAllocator(int individualAllocationSize) {
-    this(individualAllocationSize, 0);
+  public DefaultAllocator(boolean trimOnReset, int individualAllocationSize) {
+    this(trimOnReset, individualAllocationSize, 0);
   }
 
   /**
@@ -49,12 +52,16 @@ public final class DefaultAllocator implements Allocator {
    * <p>
    * Note: {@link Allocation}s created up front will never be discarded by {@link #trim()}.
    *
+   * @param trimOnReset Whether memory is freed when the allocator is reset. Should be true unless
+   *     the allocator will be re-used by multiple player instances.
    * @param individualAllocationSize The length of each individual {@link Allocation}.
    * @param initialAllocationCount The number of allocations to create up front.
    */
-  public DefaultAllocator(int individualAllocationSize, int initialAllocationCount) {
+  public DefaultAllocator(boolean trimOnReset, int individualAllocationSize,
+      int initialAllocationCount) {
     Assertions.checkArgument(individualAllocationSize > 0);
     Assertions.checkArgument(initialAllocationCount >= 0);
+    this.trimOnReset = trimOnReset;
     this.individualAllocationSize = individualAllocationSize;
     this.availableCount = initialAllocationCount;
     this.availableAllocations = new Allocation[initialAllocationCount + AVAILABLE_EXTRA_CAPACITY];
@@ -70,6 +77,12 @@ public final class DefaultAllocator implements Allocator {
     singleAllocationReleaseHolder = new Allocation[1];
   }
 
+  public synchronized void reset() {
+    if (trimOnReset) {
+      setTargetBufferSize(0);
+    }
+  }
+
   public synchronized void setTargetBufferSize(int targetBufferSize) {
     boolean targetBufferSizeReduced = targetBufferSize < this.targetBufferSize;
     this.targetBufferSize = targetBufferSize;