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Prohibit duplicate TrackGroups in TrackGroupArray
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Allowing duplicate groups caused some other code working with the
array to use reference equality comparison. This is error-prone,
easily forgotten (e.g. when using the TrackGroups in a map) and
causes bugs when TrackGroups are serialized to disk or to another
process.

All TrackGroups created by ExoPlayer are already unique and custom
code creating TrackGroupArrays with identical groups can easily
distringuish them by adding an id to each group.

Issue: google/ExoPlayer#9718
PiperOrigin-RevId: 413617005
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@tonihei
tonihei committed Dec 2, 2021
1 parent e077edd commit 417c242
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Showing 6 changed files with 70 additions and 47 deletions.
50 changes: 31 additions & 19 deletions libraries/common/src/main/java/androidx/media3/common/TrackGroupArray.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,34 +19,40 @@
import androidx.annotation.IntDef;
import androidx.annotation.Nullable;
import androidx.media3.common.util.BundleableUtil;
import androidx.media3.common.util.Log;
import androidx.media3.common.util.UnstableApi;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.util.Arrays;
import java.util.List;

/** An immutable array of {@link TrackGroup}s. */
@UnstableApi
public final class TrackGroupArray implements Bundleable {

private static final String TAG = "TrackGroupArray";

/** The empty array. */
public static final TrackGroupArray EMPTY = new TrackGroupArray();

/** The number of groups in the array. Greater than or equal to zero. */
public final int length;

private final TrackGroup[] trackGroups;
private final ImmutableList<TrackGroup> trackGroups;

// Lazily initialized hashcode.
private int hashCode;

/** Construct a {@code TrackGroupArray} from an array of (possibly empty) trackGroups. */
/**
* Construct a {@code TrackGroupArray} from an array of {@link TrackGroup TrackGroups}.
*
* <p>The groups must not contain duplicates.
*/
public TrackGroupArray(TrackGroup... trackGroups) {
this.trackGroups = trackGroups;
this.trackGroups = ImmutableList.copyOf(trackGroups);
this.length = trackGroups.length;
verifyCorrectness();
}

/**
Expand All @@ -56,7 +62,7 @@ public TrackGroupArray(TrackGroup... trackGroups) {
* @return The group.
*/
public TrackGroup get(int index) {
return trackGroups[index];
return trackGroups.get(index);
}

/**
Expand All @@ -65,16 +71,9 @@ public TrackGroup get(int index) {
* @param group The group.
* @return The index of the group, or {@link C#INDEX_UNSET} if no such group exists.
*/
@SuppressWarnings("ReferenceEquality")
public int indexOf(TrackGroup group) {
for (int i = 0; i < length; i++) {
// Suppressed reference equality warning because this is looking for the index of a specific
// TrackGroup object, not the index of a potential equal TrackGroup.
if (trackGroups[i] == group) {
return i;
}
}
return C.INDEX_UNSET;
int index = trackGroups.indexOf(group);
return index >= 0 ? index : C.INDEX_UNSET;
}

/** Returns whether this track group array is empty. */
Expand All @@ -85,7 +84,7 @@ public boolean isEmpty() {
@Override
public int hashCode() {
if (hashCode == 0) {
hashCode = Arrays.hashCode(trackGroups);
hashCode = trackGroups.hashCode();
}
return hashCode;
}
Expand All @@ -99,7 +98,7 @@ public boolean equals(@Nullable Object obj) {
return false;
}
TrackGroupArray other = (TrackGroupArray) obj;
return length == other.length && Arrays.equals(trackGroups, other.trackGroups);
return length == other.length && trackGroups.equals(other.trackGroups);
}

// Bundleable implementation.
Expand All @@ -117,8 +116,7 @@ public boolean equals(@Nullable Object obj) {
public Bundle toBundle() {
Bundle bundle = new Bundle();
bundle.putParcelableArrayList(
keyForField(FIELD_TRACK_GROUPS),
BundleableUtil.toBundleArrayList(Lists.newArrayList(trackGroups)));
keyForField(FIELD_TRACK_GROUPS), BundleableUtil.toBundleArrayList(trackGroups));
return bundle;
}

Expand All @@ -133,6 +131,20 @@ public Bundle toBundle() {
return new TrackGroupArray(trackGroups.toArray(new TrackGroup[0]));
};

private void verifyCorrectness() {
for (int i = 0; i < trackGroups.size(); i++) {
for (int j = i + 1; j < trackGroups.size(); j++) {
if (trackGroups.get(i).equals(trackGroups.get(j))) {
Log.e(
TAG,
"",
new IllegalArgumentException(
"Multiple identical TrackGroups added to one TrackGroupArray."));
}
}
}
}

private static String keyForField(@FieldNumber int field) {
return Integer.toString(field, Character.MAX_RADIX);
}
Expand Down
4 changes: 1 addition & 3 deletions libraries/exoplayer/src/main/java/androidx/media3/exoplayer/offline/DownloadHelper.java
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Original file line number Diff line number Diff line change
Expand Up @@ -835,8 +835,6 @@ private void assertPreparedWithMedia() {
* Runs the track selection for a given period index with the current parameters. The selected
* tracks will be added to {@link #trackSelectionsByPeriodAndRenderer}.
*/
// Intentional reference comparison of track group instances.
@SuppressWarnings("ReferenceEquality")
@RequiresNonNull({
"trackGroupArrays",
"trackSelectionsByPeriodAndRenderer",
Expand All @@ -861,7 +859,7 @@ private TrackSelectorResult runTrackSelection(int periodIndex) {
boolean mergedWithExistingSelection = false;
for (int j = 0; j < existingSelectionList.size(); j++) {
ExoTrackSelection existingSelection = existingSelectionList.get(j);
if (existingSelection.getTrackGroup() == newSelection.getTrackGroup()) {
if (existingSelection.getTrackGroup().equals(newSelection.getTrackGroup())) {
// Merge with existing selection.
scratchSet.clear();
for (int k = 0; k < existingSelection.length(); k++) {
Expand Down
9 changes: 3 additions & 6 deletions ...xoplayer/src/main/java/androidx/media3/exoplayer/trackselection/MappingTrackSelector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -563,13 +563,10 @@ private static int[] getMixedMimeTypeAdaptationSupports(
for (int trackIndex = 0; trackIndex < trackGroup.length; trackIndex++) {
trackSupport[trackIndex] =
mappedTrackInfo.getTrackSupport(rendererIndex, groupIndex, trackIndex);
// Suppressing reference equality warning because the track group stored in the track
// selection must point to the exact track group object to be considered part of it.
@SuppressWarnings("ReferenceEquality")
boolean isTrackSelected =
(trackSelection != null)
&& (trackSelection.getTrackGroup() == trackGroup)
&& (trackSelection.indexOf(trackIndex) != C.INDEX_UNSET);
trackSelection != null
&& trackSelection.getTrackGroup().equals(trackGroup)
&& trackSelection.indexOf(trackIndex) != C.INDEX_UNSET;
selected[trackIndex] = isTrackSelected;
}
@C.TrackType int trackGroupType = mappedTrackInfo.getRendererType(rendererIndex);
Expand Down
5 changes: 1 addition & 4 deletions libraries/exoplayer/src/main/java/androidx/media3/exoplayer/util/EventLogger.java
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Original file line number Diff line number Diff line change
Expand Up @@ -655,14 +655,11 @@ private static String getAdaptiveSupportString(
}
}

// Suppressing reference equality warning because the track group stored in the track selection
// must point to the exact track group object to be considered part of it.
@SuppressWarnings("ReferenceEquality")
private static String getTrackStatusString(
@Nullable TrackSelection selection, TrackGroup group, int trackIndex) {
return getTrackStatusString(
selection != null
&& selection.getTrackGroup() == group
&& selection.getTrackGroup().equals(group)
&& selection.indexOf(trackIndex) != C.INDEX_UNSET);
}

Expand Down
24 changes: 19 additions & 5 deletions ...ayer/src/test/java/androidx/media3/exoplayer/trackselection/DefaultTrackSelectorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -250,6 +250,8 @@ public void selectTrack_withMixedEmptyAndNonEmptyTrackOverrides_appliesNonEmptyO
@Test
public void selectTracks_withEmptyTrackOverrideForDifferentTracks_hasNoEffect()
throws ExoPlaybackException {
TrackGroup videoGroup0 = VIDEO_TRACK_GROUP.copyWithId("0");
TrackGroup videoGroup1 = VIDEO_TRACK_GROUP.copyWithId("1");
trackSelector.setParameters(
trackSelector
.buildUponParameters()
Expand All @@ -263,11 +265,16 @@ public void selectTracks_withEmptyTrackOverrideForDifferentTracks_hasNoEffect()
TrackSelectorResult result =
trackSelector.selectTracks(
RENDERER_CAPABILITIES,
new TrackGroupArray(VIDEO_TRACK_GROUP, AUDIO_TRACK_GROUP, VIDEO_TRACK_GROUP),
new TrackGroupArray(videoGroup0, AUDIO_TRACK_GROUP, videoGroup1),
periodId,
TIMELINE);

assertThat(result.selections).asList().containsExactlyElementsIn(TRACK_SELECTIONS).inOrder();
assertThat(result.selections)
.asList()
.containsExactly(
new FixedTrackSelection(videoGroup0, /* track= */ 0),
new FixedTrackSelection(AUDIO_TRACK_GROUP, /* track= */ 0))
.inOrder();
assertThat(result.rendererConfigurations)
.isEqualTo(new RendererConfiguration[] {DEFAULT, DEFAULT});
}
Expand Down Expand Up @@ -366,17 +373,24 @@ public void selectTracks_withOverrideForUnmappedGroup_disablesAllRenderersOfSame
/** Tests that an override is not applied for a different set of available track groups. */
@Test
public void selectTracksWithNullOverrideForDifferentTracks() throws ExoPlaybackException {
TrackGroup videoGroup0 = VIDEO_TRACK_GROUP.copyWithId("0");
TrackGroup videoGroup1 = VIDEO_TRACK_GROUP.copyWithId("1");
trackSelector.setParameters(
trackSelector
.buildUponParameters()
.setSelectionOverride(0, new TrackGroupArray(VIDEO_TRACK_GROUP), null));
.setSelectionOverride(0, new TrackGroupArray(VIDEO_TRACK_GROUP.copyWithId("2")), null));
TrackSelectorResult result =
trackSelector.selectTracks(
RENDERER_CAPABILITIES,
new TrackGroupArray(VIDEO_TRACK_GROUP, AUDIO_TRACK_GROUP, VIDEO_TRACK_GROUP),
new TrackGroupArray(videoGroup0, AUDIO_TRACK_GROUP, videoGroup1),
periodId,
TIMELINE);
assertSelections(result, TRACK_SELECTIONS);
assertThat(result.selections)
.asList()
.containsExactly(
new FixedTrackSelection(videoGroup0, /* track= */ 0),
new FixedTrackSelection(AUDIO_TRACK_GROUP, /* track= */ 0))
.inOrder();
assertThat(result.rendererConfigurations)
.isEqualTo(new RendererConfiguration[] {DEFAULT, DEFAULT});
}
Expand Down
25 changes: 15 additions & 10 deletions ...ayer/src/test/java/androidx/media3/exoplayer/trackselection/MappingTrackSelectorTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -96,27 +96,32 @@ public void selectTracks_audioAndVideo_reverseOrderToRenderers_mappedToCorrectRe
@Test
public void selectTracks_multipleVideoAndAudioTracks_mappedToSameRenderer()
throws ExoPlaybackException {
TrackGroup videoGroup0 = VIDEO_TRACK_GROUP.copyWithId("0");
TrackGroup videoGroup1 = VIDEO_TRACK_GROUP.copyWithId("1");
TrackGroup audioGroup0 = AUDIO_TRACK_GROUP.copyWithId("0");
TrackGroup audioGroup1 = AUDIO_TRACK_GROUP.copyWithId("1");
FakeMappingTrackSelector trackSelector = new FakeMappingTrackSelector();
TrackGroupArray trackGroups =
new TrackGroupArray(
VIDEO_TRACK_GROUP, AUDIO_TRACK_GROUP, AUDIO_TRACK_GROUP, VIDEO_TRACK_GROUP);
new TrackGroupArray(videoGroup0, audioGroup0, audioGroup1, videoGroup1);
RendererCapabilities[] rendererCapabilities =
new RendererCapabilities[] {
VIDEO_CAPABILITIES, AUDIO_CAPABILITIES, VIDEO_CAPABILITIES, AUDIO_CAPABILITIES
};

trackSelector.selectTracks(rendererCapabilities, trackGroups, periodId, TIMELINE);

trackSelector.assertMappedTrackGroups(0, VIDEO_TRACK_GROUP, VIDEO_TRACK_GROUP);
trackSelector.assertMappedTrackGroups(1, AUDIO_TRACK_GROUP, AUDIO_TRACK_GROUP);
trackSelector.assertMappedTrackGroups(0, videoGroup0, videoGroup1);
trackSelector.assertMappedTrackGroups(1, audioGroup0, audioGroup1);
}

@Test
public void selectTracks_multipleMetadataTracks_mappedToDifferentRenderers()
throws ExoPlaybackException {
TrackGroup metadataGroup0 = METADATA_TRACK_GROUP.copyWithId("0");
TrackGroup metadataGroup1 = METADATA_TRACK_GROUP.copyWithId("1");
FakeMappingTrackSelector trackSelector = new FakeMappingTrackSelector();
TrackGroupArray trackGroups =
new TrackGroupArray(VIDEO_TRACK_GROUP, METADATA_TRACK_GROUP, METADATA_TRACK_GROUP);
new TrackGroupArray(VIDEO_TRACK_GROUP, metadataGroup0, metadataGroup1);
RendererCapabilities[] rendererCapabilities =
new RendererCapabilities[] {
VIDEO_CAPABILITIES, METADATA_CAPABILITIES, METADATA_CAPABILITIES
Expand All @@ -125,8 +130,8 @@ public void selectTracks_multipleMetadataTracks_mappedToDifferentRenderers()
trackSelector.selectTracks(rendererCapabilities, trackGroups, periodId, TIMELINE);

trackSelector.assertMappedTrackGroups(0, VIDEO_TRACK_GROUP);
trackSelector.assertMappedTrackGroups(1, METADATA_TRACK_GROUP);
trackSelector.assertMappedTrackGroups(2, METADATA_TRACK_GROUP);
trackSelector.assertMappedTrackGroups(1, metadataGroup0);
trackSelector.assertMappedTrackGroups(2, metadataGroup1);
}

private static TrackGroup buildTrackGroup(String sampleMimeType) {
Expand All @@ -141,10 +146,10 @@ public void buildTrackInfos_withTestValues_isAsExpected() {
new int[] {C.TRACK_TYPE_AUDIO, C.TRACK_TYPE_VIDEO},
new TrackGroupArray[] {
new TrackGroupArray(
new TrackGroup(new Format.Builder().build()),
new TrackGroup(new Format.Builder().build())),
new TrackGroup("0", new Format.Builder().build()),
new TrackGroup("1", new Format.Builder().build())),
new TrackGroupArray(
new TrackGroup(new Format.Builder().build(), new Format.Builder().build()))
new TrackGroup("2", new Format.Builder().build(), new Format.Builder().build()))
},
new int[] {
RendererCapabilities.ADAPTIVE_SEAMLESS, RendererCapabilities.ADAPTIVE_NOT_SUPPORTED
Expand Down

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