Clean up period identifiers.

SinglePeriodTimelines can all use the same identifier, as their identifier is
wrapped in a pair with the (fixed) source index when they are concatenated with
other sources' timelines.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130386297

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

@@ -62,13 +62,7 @@ public interface Timeline {
   /**
    * Returns a unique identifier for the period at {@code periodIndex}, or {@code null} if the
    * period at {@code periodIndex} is not known. The identifier is stable across {@link Timeline}
-   * instances.
-   * <p>
-   * When the timeline changes the player uses period identifiers to determine what periods are
-   * unchanged. Implementations that associate an object with each period can return the object for
-   * the provided index to guarantee uniqueness. Other implementations must be careful to return
-   * identifiers that can't clash with (for example) identifiers used by other timelines that may be
-   * concatenated with this one.
+   * changes.
    *
    * @param periodIndex A period index.
    * @return An identifier for the period, or {@code null} if the period is not known.
@@ -79,7 +73,7 @@ public interface Timeline {
    * Returns the index of the window to which the period with the specified index belongs.
    *
    * @param periodIndex The period index.
-   * @return The index of the corresponding seek window.
+   * @return The index of the corresponding window.
    */
   int getPeriodWindowIndex(int periodIndex);
 

library/src/main/java/com/google/android/exoplayer2/source/ConcatenatingMediaSource.java

@@ -210,18 +210,23 @@ public final class ConcatenatingMediaSource implements MediaSource {
 
     @Override
     public int getIndexOfPeriod(Object id) {
-      // The id was returned by getPeriodId, so it is always a Pair<Integer, Object>.
+      if (!(id instanceof Pair)) {
+        return NO_PERIOD_INDEX;
+      }
       @SuppressWarnings("unchecked")
       Pair<Integer, Object> sourceIndexAndPeriodId = (Pair<Integer, Object>) id;
+      if (!(sourceIndexAndPeriodId.first instanceof Integer)) {
+        return NO_PERIOD_INDEX;
+      }
       int sourceIndex = sourceIndexAndPeriodId.first;
       Object periodId = sourceIndexAndPeriodId.second;
-      int periodIndexInSource = timelines[sourceIndex].getIndexOfPeriod(periodId);
-      if (periodIndexInSource != NO_PERIOD_INDEX) {
-        int firstPeriodIndexInSource = getFirstPeriodIndexInSource(sourceIndex);
-        return firstPeriodIndexInSource + periodIndexInSource;
-      }
+      if (sourceIndex < 0 || sourceIndex >= timelines.length) {
         return NO_PERIOD_INDEX;
       }
+      int periodIndexInSource = timelines[sourceIndex].getIndexOfPeriod(periodId);
+      return periodIndexInSource == NO_PERIOD_INDEX ? NO_PERIOD_INDEX
+          : getFirstPeriodIndexInSource(sourceIndex) + periodIndexInSource;
+    }
 
     @Override
     public int getWindowCount() {

library/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaPeriod.java

@@ -298,7 +298,7 @@ import java.util.Arrays;
       durationUs = largestQueuedTimestampUs == Long.MIN_VALUE ? 0
           : largestQueuedTimestampUs + DEFAULT_LAST_SAMPLE_DURATION_US;
       sourceListener.onSourceInfoRefreshed(
-          new SinglePeriodTimeline(0, durationUs, seekMap.isSeekable()), null);
+          new SinglePeriodTimeline(durationUs, seekMap.isSeekable()), null);
     }
   }
 
@@ -381,7 +381,7 @@ import java.util.Arrays;
     tracks = new TrackGroupArray(trackArray);
     prepared = true;
     sourceListener.onSourceInfoRefreshed(
-        new SinglePeriodTimeline(0, durationUs, seekMap.isSeekable()), null);
+        new SinglePeriodTimeline(durationUs, seekMap.isSeekable()), null);
     callback.onPrepared(this);
   }
 

library/src/main/java/com/google/android/exoplayer2/source/ExtractorMediaSource.java

@@ -135,7 +135,7 @@ public final class ExtractorMediaSource implements MediaSource, MediaSource.List
   @Override
   public void prepareSource(MediaSource.Listener listener) {
     sourceListener = listener;
-    timeline = new SinglePeriodTimeline(0, C.UNSET_TIME_US, false);
+    timeline = new SinglePeriodTimeline(C.UNSET_TIME_US, false);
     listener.onSourceInfoRefreshed(timeline, null);
   }
 

library/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java

@@ -26,7 +26,8 @@ import com.google.android.exoplayer2.util.Assertions;
  */
 public final class SinglePeriodTimeline implements Timeline {
 
-  private final Object id;
+  private static final Object ID = new Object();
+
   private final boolean isFinal;
   private final long durationUs;
   private final Window window;
@@ -35,24 +36,21 @@ public final class SinglePeriodTimeline implements Timeline {
    * Creates a final timeline with one period of known duration and a window extending from
    * zero to its duration.
    *
-   * @param id The identifier for the period.
    * @param durationUs The duration of the period, in microseconds.
    * @param isSeekable Whether seeking is supported within the period.
    */
-  public SinglePeriodTimeline(Object id, long durationUs, boolean isSeekable) {
-    this(id, durationUs, Window.createWindowFromZero(durationUs, isSeekable));
+  public SinglePeriodTimeline(long durationUs, boolean isSeekable) {
+    this(durationUs, Window.createWindowFromZero(durationUs, isSeekable));
   }
 
   /**
    * Creates a final timeline with one period of known duration and a window extending from
    * zero to its duration.
    *
-   * @param id The identifier for the period.
    * @param durationUs The duration of the period, in microseconds.
    * @param window The available window within the period.
    */
-  public SinglePeriodTimeline(Object id, long durationUs, Window window) {
-    this.id = Assertions.checkNotNull(id);
+  public SinglePeriodTimeline(long durationUs, Window window) {
     this.durationUs = durationUs;
     this.window = window;
     this.isFinal = true; // TODO: Remove.
@@ -88,7 +86,7 @@ public final class SinglePeriodTimeline implements Timeline {
   @Override
   public Object getPeriodId(int periodIndex) {
     Assertions.checkIndex(periodIndex, 0, 1);
-    return id;
+    return ID;
   }
 
   @Override
@@ -99,7 +97,7 @@ public final class SinglePeriodTimeline implements Timeline {
 
   @Override
   public int getIndexOfPeriod(Object id) {
-    return id.equals(this.id) ? 0 : Timeline.NO_PERIOD_INDEX;
+    return ID.equals(id) ? 0 : Timeline.NO_PERIOD_INDEX;
   }
 
   @Override

library/src/main/java/com/google/android/exoplayer2/source/SingleSampleMediaSource.java

@@ -79,7 +79,7 @@ public final class SingleSampleMediaSource implements MediaSource {
     this.eventHandler = eventHandler;
     this.eventListener = eventListener;
     this.eventSourceId = eventSourceId;
-    timeline = new SinglePeriodTimeline(0, durationUs, true);
+    timeline = new SinglePeriodTimeline(durationUs, true);
   }
 
   // MediaSource implementation.

library/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java

@@ -539,7 +539,12 @@ public final class DashMediaSource implements MediaSource {
 
     @Override
     public int getIndexOfPeriod(Object id) {
-      return ((Integer) id) - firstPeriodId;
+      if (!(id instanceof Integer)) {
+        return NO_PERIOD_INDEX;
+      }
+      int periodId = (int) id;
+      return periodId < firstPeriodId || periodId >= firstPeriodId + getPeriodCount()
+          ? NO_PERIOD_INDEX : periodId - firstPeriodId;
     }
 
     @Override

library/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaPeriod.java

@@ -281,7 +281,7 @@ import java.util.List;
     callback.onPrepared(this);
 
     // TODO[playlists]: Calculate the window.
-    Timeline timeline = new SinglePeriodTimeline(0, durationUs, !isLive);
+    Timeline timeline = new SinglePeriodTimeline(durationUs, !isLive);
     sourceListener.onSourceInfoRefreshed(timeline, playlist);
   }
 

library/src/main/java/com/google/android/exoplayer2/source/hls/HlsMediaSource.java

@@ -65,8 +65,7 @@ public final class HlsMediaSource implements MediaSource {
   public void prepareSource(MediaSource.Listener listener) {
     sourceListener = listener;
     // TODO: Defer until the playlist has been loaded.
-    listener.onSourceInfoRefreshed(
-        new SinglePeriodTimeline(this, C.UNSET_TIME_US, false), null);
+    listener.onSourceInfoRefreshed(new SinglePeriodTimeline(C.UNSET_TIME_US, false), null);
   }
 
   @Override

library/src/main/java/com/google/android/exoplayer2/source/smoothstreaming/SsMediaSource.java

@@ -185,16 +185,16 @@ public final class SsMediaSource implements MediaSource,
       }
       if (startTimeUs == Long.MAX_VALUE || manifest.dvrWindowLengthUs == C.UNSET_TIME_US
           || manifest.dvrWindowLengthUs == 0) {
-        timeline = new SinglePeriodTimeline(0, C.UNSET_TIME_US, false);
+        timeline = new SinglePeriodTimeline(C.UNSET_TIME_US, false);
       } else {
         long periodDurationUs = startTimeUs + manifest.dvrWindowLengthUs;
         Window window = Window.createWindow(0, startTimeUs, 0, periodDurationUs,
             manifest.dvrWindowLengthUs, true);
-        timeline = new SinglePeriodTimeline(0, periodDurationUs, window);
+        timeline = new SinglePeriodTimeline(periodDurationUs, window);
       }
     } else {
       boolean isSeekable = manifest.durationUs != C.UNSET_TIME_US;
-      timeline = new SinglePeriodTimeline(0, manifest.durationUs, isSeekable);
+      timeline = new SinglePeriodTimeline(manifest.durationUs, isSeekable);
     }
     window = timeline.getWindow(0);
     sourceListener.onSourceInfoRefreshed(timeline, manifest);