Add NonNull annotations to the most extractor packages

PiperOrigin-RevId: 285961788

library/core/src/main/java/com/google/android/exoplayer2/extractor/amr/AmrExtractor.java

@@ -16,7 +16,6 @@
 package com.google.android.exoplayer2.extractor.amr;
 
 import androidx.annotation.IntDef;
-import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.ParserException;
@@ -28,6 +27,7 @@ import com.google.android.exoplayer2.extractor.ExtractorsFactory;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.SeekMap;
 import com.google.android.exoplayer2.extractor.TrackOutput;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.Util;
 import java.io.EOFException;
@@ -36,6 +36,9 @@ import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.Arrays;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /**
  * Extracts data from the AMR containers format (either AMR or AMR-WB). This follows RFC-4867,
@@ -138,9 +141,9 @@ public final class AmrExtractor implements Extractor {
   private int numSamplesWithSameSize;
   private long timeOffsetUs;
 
-  private ExtractorOutput extractorOutput;
-  private TrackOutput trackOutput;
-  @Nullable private SeekMap seekMap;
+  @MonotonicNonNull private ExtractorOutput extractorOutput;
+  @MonotonicNonNull private TrackOutput trackOutput;
+  @MonotonicNonNull private SeekMap seekMap;
   private boolean hasOutputFormat;
 
   public AmrExtractor() {
@@ -171,6 +174,7 @@ public final class AmrExtractor implements Extractor {
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
+    assertInitialized();
     if (input.getPosition() == 0) {
       if (!readAmrHeader(input)) {
         throw new ParserException("Could not find AMR header.");
@@ -245,6 +249,7 @@ public final class AmrExtractor implements Extractor {
     return Arrays.equals(header, amrSignature);
   }
 
+  @RequiresNonNull("trackOutput")
   private void maybeOutputFormat() {
     if (!hasOutputFormat) {
       hasOutputFormat = true;
@@ -267,6 +272,7 @@ public final class AmrExtractor implements Extractor {
     }
   }
 
+  @RequiresNonNull("trackOutput")
   private int readSample(ExtractorInput extractorInput) throws IOException, InterruptedException {
     if (currentSampleBytesRemaining == 0) {
       try {
@@ -346,6 +352,7 @@ public final class AmrExtractor implements Extractor {
     return !isWideBand && (frameType < 12 || frameType > 14);
   }
 
+  @RequiresNonNull("extractorOutput")
   private void maybeOutputSeekMap(long inputLength, int sampleReadResult) {
     if (hasOutputSeekMap) {
       return;
@@ -370,6 +377,12 @@ public final class AmrExtractor implements Extractor {
     return new ConstantBitrateSeekMap(inputLength, firstSamplePosition, bitrate, firstSampleSize);
   }
 
+  @EnsuresNonNull({"extractorOutput", "trackOutput"})
+  private void assertInitialized() {
+    Assertions.checkStateNotNull(trackOutput);
+    Util.castNonNull(extractorOutput);
+  }
+
   /**
    * Returns the stream bitrate, given a frame size and the duration of that frame in microseconds.
    *

library/core/src/main/java/com/google/android/exoplayer2/extractor/amr/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.amr;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/flac/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.flac;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/flv/FlvExtractor.java

@@ -23,11 +23,14 @@ import com.google.android.exoplayer2.extractor.ExtractorOutput;
 import com.google.android.exoplayer2.extractor.ExtractorsFactory;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.SeekMap;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.io.IOException;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /**
  * Extracts data from the FLV container format.
@@ -71,7 +74,7 @@ public final class FlvExtractor implements Extractor {
   private final ParsableByteArray tagData;
   private final ScriptTagPayloadReader metadataReader;
 
-  private ExtractorOutput extractorOutput;
+  @MonotonicNonNull private ExtractorOutput extractorOutput;
   private @States int state;
   private boolean outputFirstSample;
   private long mediaTagTimestampOffsetUs;
@@ -80,8 +83,8 @@ public final class FlvExtractor implements Extractor {
   private int tagDataSize;
   private long tagTimestampUs;
   private boolean outputSeekMap;
-  private AudioTagPayloadReader audioReader;
-  private VideoTagPayloadReader videoReader;
+  @MonotonicNonNull private AudioTagPayloadReader audioReader;
+  @MonotonicNonNull private VideoTagPayloadReader videoReader;
 
   public FlvExtractor() {
     scratch = new ParsableByteArray(4);
@@ -143,6 +146,7 @@ public final class FlvExtractor implements Extractor {
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition) throws IOException,
       InterruptedException {
+    Assertions.checkStateNotNull(extractorOutput); // Asserts that init has been called.
     while (true) {
       switch (state) {
         case STATE_READING_FLV_HEADER:
@@ -178,6 +182,7 @@ public final class FlvExtractor implements Extractor {
    * @throws IOException If an error occurred reading or parsing data from the source.
    * @throws InterruptedException If the thread was interrupted.
    */
+  @RequiresNonNull("extractorOutput")
   private boolean readFlvHeader(ExtractorInput input) throws IOException, InterruptedException {
     if (!input.readFully(headerBuffer.data, 0, FLV_HEADER_SIZE, true)) {
       // We've reached the end of the stream.
@@ -250,6 +255,7 @@ public final class FlvExtractor implements Extractor {
    * @throws IOException If an error occurred reading or parsing data from the source.
    * @throws InterruptedException If the thread was interrupted.
    */
+  @RequiresNonNull("extractorOutput")
   private boolean readTagData(ExtractorInput input) throws IOException, InterruptedException {
     boolean wasConsumed = true;
     boolean wasSampleOutput = false;
@@ -293,6 +299,7 @@ public final class FlvExtractor implements Extractor {
     return tagData;
   }
 
+  @RequiresNonNull("extractorOutput")
   private void ensureReadyForMediaOutput() {
     if (!outputSeekMap) {
       extractorOutput.seekMap(new SeekMap.Unseekable(C.TIME_UNSET));

library/core/src/main/java/com/google/android/exoplayer2/extractor/flv/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.flv;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/mkv/DefaultEbmlReader.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.mkv;
 
+
 import androidx.annotation.IntDef;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ParserException;
@@ -26,6 +27,8 @@ import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.util.ArrayDeque;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /**
  * Default implementation of {@link EbmlReader}.
@@ -52,7 +55,7 @@ import java.util.ArrayDeque;
   private final ArrayDeque<MasterElement> masterElementsStack;
   private final VarintReader varintReader;
 
-  private EbmlProcessor processor;
+  @MonotonicNonNull private EbmlProcessor processor;
   private @ElementState int elementState;
   private int elementId;
   private long elementContentSize;
@@ -79,8 +82,8 @@ import java.util.ArrayDeque;
   public boolean read(ExtractorInput input) throws IOException, InterruptedException {
     Assertions.checkNotNull(processor);
     while (true) {
-      if (!masterElementsStack.isEmpty()
-          && input.getPosition() >= masterElementsStack.peek().elementEndPosition) {
+      MasterElement head = masterElementsStack.peek();
+      if (head != null && input.getPosition() >= head.elementEndPosition) {
         processor.endMasterElement(masterElementsStack.pop().elementId);
         return true;
       }
@@ -159,8 +162,9 @@ import java.util.ArrayDeque;
    * @throws IOException If an error occurs reading from the input.
    * @throws InterruptedException If the thread is interrupted.
    */
-  private long maybeResyncToNextLevel1Element(ExtractorInput input) throws IOException,
-      InterruptedException {
+  @RequiresNonNull("processor")
+  private long maybeResyncToNextLevel1Element(ExtractorInput input)
+      throws IOException, InterruptedException {
     input.resetPeekPosition();
     while (true) {
       input.peekFully(scratch, 0, MAX_ID_BYTES);

library/core/src/main/java/com/google/android/exoplayer2/extractor/mkv/MatroskaExtractor.java

@@ -57,6 +57,8 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.UUID;
+import org.checkerframework.checker.nullness.compatqual.NullableType;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 /** Extracts data from the Matroska and WebM container formats. */
 public class MatroskaExtractor implements Extractor {
@@ -342,7 +344,7 @@ public class MatroskaExtractor implements Extractor {
   private long durationUs = C.TIME_UNSET;
 
   // The track corresponding to the current TrackEntry element, or null.
-  private Track currentTrack;
+  @Nullable private Track currentTrack;
 
   // Whether a seek map has been sent to the output.
   private boolean sentSeekMap;
@@ -356,8 +358,8 @@ public class MatroskaExtractor implements Extractor {
   private long cuesContentPosition = C.POSITION_UNSET;
   private long seekPositionAfterBuildingCues = C.POSITION_UNSET;
   private long clusterTimecodeUs = C.TIME_UNSET;
-  private LongArray cueTimesUs;
-  private LongArray cueClusterPositions;
+  @Nullable private LongArray cueTimesUs;
+  @Nullable private LongArray cueClusterPositions;
   private boolean seenClusterPositionForCurrentCuePoint;
 
   // Reading state.
@@ -372,8 +374,7 @@ public class MatroskaExtractor implements Extractor {
   private int[] blockSampleSizes;
   private int blockTrackNumber;
   private int blockTrackNumberLength;
-  @C.BufferFlags
-  private int blockFlags;
+  @C.BufferFlags private int blockFlags;
   private int blockAdditionalId;
   private boolean blockHasReferenceBlock;
 
@@ -389,7 +390,7 @@ public class MatroskaExtractor implements Extractor {
   private boolean sampleInitializationVectorRead;
 
   // Extractor outputs.
-  private ExtractorOutput extractorOutput;
+  @MonotonicNonNull private ExtractorOutput extractorOutput;
 
   public MatroskaExtractor() {
     this(0);
@@ -415,6 +416,7 @@ public class MatroskaExtractor implements Extractor {
     encryptionInitializationVector = new ParsableByteArray(ENCRYPTION_IV_SIZE);
     encryptionSubsampleData = new ParsableByteArray();
     blockAdditionalData = new ParsableByteArray();
+    blockSampleSizes = new int[1];
   }
 
   @Override
@@ -1924,7 +1926,7 @@ public class MatroskaExtractor implements Extractor {
       String mimeType;
       int maxInputSize = Format.NO_VALUE;
       @C.PcmEncoding int pcmEncoding = Format.NO_VALUE;
-      List<byte[]> initializationData = null;
+      @Nullable List<byte[]> initializationData = null;
       switch (codecId) {
         case CODEC_ID_VP8:
           mimeType = MimeTypes.VIDEO_VP8;
@@ -1958,7 +1960,8 @@ public class MatroskaExtractor implements Extractor {
           nalUnitLengthFieldLength = hevcConfig.nalUnitLengthFieldLength;
           break;
         case CODEC_ID_FOURCC:
-          Pair<String, List<byte[]>> pair = parseFourCcPrivate(new ParsableByteArray(codecPrivate));
+          Pair<String, @NullableType List<byte[]>> pair =
+              parseFourCcPrivate(new ParsableByteArray(codecPrivate));
           mimeType = pair.first;
           initializationData = pair.second;
           break;
@@ -2220,8 +2223,8 @@ public class MatroskaExtractor implements Extractor {
      *     is {@code null}.
      * @throws ParserException If the initialization data could not be built.
      */
-    private static Pair<String, List<byte[]>> parseFourCcPrivate(ParsableByteArray buffer)
-        throws ParserException {
+    private static Pair<String, @NullableType List<byte[]>> parseFourCcPrivate(
+        ParsableByteArray buffer) throws ParserException {
       try {
         buffer.skipBytes(16); // size(4), width(4), height(4), planes(2), bitcount(2).
         long compression = buffer.readLittleEndianUnsignedInt();

library/core/src/main/java/com/google/android/exoplayer2/extractor/mkv/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.mkv;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp3/Mp3Extractor.java

@@ -34,12 +34,17 @@ import com.google.android.exoplayer2.metadata.Metadata;
 import com.google.android.exoplayer2.metadata.id3.Id3Decoder;
 import com.google.android.exoplayer2.metadata.id3.Id3Decoder.FramePredicate;
 import com.google.android.exoplayer2.metadata.id3.MlltFrame;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
+import com.google.android.exoplayer2.util.Util;
 import java.io.EOFException;
 import java.io.IOException;
 import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNull;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /**
  * Extracts data from the MP3 container format.
@@ -107,13 +112,13 @@ public final class Mp3Extractor implements Extractor {
   private final Id3Peeker id3Peeker;
 
   // Extractor outputs.
-  private ExtractorOutput extractorOutput;
-  private TrackOutput trackOutput;
+  @MonotonicNonNull private ExtractorOutput extractorOutput;
+  @MonotonicNonNull private TrackOutput trackOutput;
 
   private int synchronizedHeaderData;
 
-  private Metadata metadata;
-  @Nullable private Seeker seeker;
+  @Nullable private Metadata metadata;
+  @MonotonicNonNull private Seeker seeker;
   private boolean disableSeeking;
   private long basisTimeUs;
   private long samplesRead;
@@ -176,6 +181,7 @@ public final class Mp3Extractor implements Extractor {
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
+    assertInitialized();
     if (synchronizedHeaderData == 0) {
       try {
         synchronize(input, false);
@@ -242,6 +248,7 @@ public final class Mp3Extractor implements Extractor {
 
   // Internal methods.
 
+  @RequiresNonNull({"trackOutput", "seeker"})
   private int readSample(ExtractorInput extractorInput) throws IOException, InterruptedException {
     if (sampleBytesRemaining == 0) {
       extractorInput.resetPeekPosition();
@@ -390,6 +397,7 @@ public final class Mp3Extractor implements Extractor {
    * @throws InterruptedException Thrown if reading from the stream was interrupted. Not expected if
    *     the next two frames were already peeked during synchronization.
    */
+  @Nullable
   private Seeker maybeReadSeekFrame(ExtractorInput input) throws IOException, InterruptedException {
     ParsableByteArray frame = new ParsableByteArray(synchronizedHeader.frameSize);
     input.peekFully(frame.data, 0, synchronizedHeader.frameSize);
@@ -397,7 +405,7 @@ public final class Mp3Extractor implements Extractor {
         ? (synchronizedHeader.channels != 1 ? 36 : 21) // MPEG 1
         : (synchronizedHeader.channels != 1 ? 21 : 13); // MPEG 2 or 2.5
     int seekHeader = getSeekFrameHeader(frame, xingBase);
-    Seeker seeker;
+    @Nullable Seeker seeker;
     if (seekHeader == SEEK_HEADER_XING || seekHeader == SEEK_HEADER_INFO) {
       seeker = XingSeeker.create(input.getLength(), input.getPosition(), synchronizedHeader, frame);
       if (seeker != null && !gaplessInfoHolder.hasGaplessInfo()) {
@@ -435,6 +443,12 @@ public final class Mp3Extractor implements Extractor {
     return new ConstantBitrateSeeker(input.getLength(), input.getPosition(), synchronizedHeader);
   }
 
+  @EnsuresNonNull({"extractorOutput", "trackOutput"})
+  private void assertInitialized() {
+    Assertions.checkStateNotNull(trackOutput);
+    Util.castNonNull(extractorOutput);
+  }
+
   /**
    * Returns whether the headers match in those bits masked by {@link #MPEG_AUDIO_HEADER_MASK}.
    */
@@ -465,7 +479,8 @@ public final class Mp3Extractor implements Extractor {
   }
 
   @Nullable
-  private static MlltSeeker maybeHandleSeekMetadata(Metadata metadata, long firstFramePosition) {
+  private static MlltSeeker maybeHandleSeekMetadata(
+      @Nullable Metadata metadata, long firstFramePosition) {
     if (metadata != null) {
       int length = metadata.length();
       for (int i = 0; i < length; i++) {
@@ -477,6 +492,4 @@ public final class Mp3Extractor implements Extractor {
     }
     return null;
   }
-
-
 }

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp3/VbriSeeker.java

@@ -41,7 +41,8 @@ import com.google.android.exoplayer2.util.Util;
    * @return A {@link VbriSeeker} for seeking in the stream, or {@code null} if the required
    *     information is not present.
    */
-  public static @Nullable VbriSeeker create(
+  @Nullable
+  public static VbriSeeker create(
       long inputLength, long position, MpegAudioHeader mpegAudioHeader, ParsableByteArray frame) {
     frame.skipBytes(10);
     int numFrames = frame.readInt();

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp3/XingSeeker.java

@@ -42,7 +42,8 @@ import com.google.android.exoplayer2.util.Util;
    * @return A {@link XingSeeker} for seeking in the stream, or {@code null} if the required
    *     information is not present.
    */
-  public static @Nullable XingSeeker create(
+  @Nullable
+  public static XingSeeker create(
       long inputLength, long position, MpegAudioHeader mpegAudioHeader, ParsableByteArray frame) {
     int samplesPerFrame = mpegAudioHeader.samplesPerFrame;
     int sampleRate = mpegAudioHeader.sampleRate;

library/core/src/main/java/com/google/android/exoplayer2/extractor/mp3/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.mp3;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/DefaultOggSeeker.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ParserException;
@@ -39,7 +40,7 @@ import java.io.IOException;
   private static final int STATE_SKIP = 3;
   private static final int STATE_IDLE = 4;
 
-  private final OggPageHeader pageHeader = new OggPageHeader();
+  private final OggPageHeader pageHeader;
   private final long payloadStartPosition;
   private final long payloadEndPosition;
   private final StreamReader streamReader;
@@ -83,6 +84,7 @@ import java.io.IOException;
     } else {
       state = STATE_SEEK_TO_END;
     }
+    pageHeader = new OggPageHeader();
   }
 
   @Override
@@ -121,6 +123,7 @@ import java.io.IOException;
   }
 
   @Override
+  @Nullable
   public OggSeekMap createSeekMap() {
     return totalGranules != 0 ? new OggSeekMap() : null;
   }

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/FlacReader.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.FlacFrameReader;
 import com.google.android.exoplayer2.extractor.FlacMetadataReader;
@@ -37,8 +38,8 @@ import java.util.Arrays;
 
   private static final int FRAME_HEADER_SAMPLE_NUMBER_OFFSET = 4;
 
-  private FlacStreamMetadata streamMetadata;
-  private FlacOggSeeker flacOggSeeker;
+  @Nullable private FlacStreamMetadata streamMetadata;
+  @Nullable private FlacOggSeeker flacOggSeeker;
 
   public static boolean verifyBitstreamType(ParsableByteArray data) {
     return data.bytesLeft() >= 5 && data.readUnsignedByte() == 0x7F && // packet type

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/OggExtractor.java

@@ -23,8 +23,11 @@ import com.google.android.exoplayer2.extractor.ExtractorOutput;
 import com.google.android.exoplayer2.extractor.ExtractorsFactory;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.TrackOutput;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.io.IOException;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 /**
  * Extracts data from the Ogg container format.
@@ -36,8 +39,8 @@ public class OggExtractor implements Extractor {
 
   private static final int MAX_VERIFICATION_BYTES = 8;
 
-  private ExtractorOutput output;
-  private StreamReader streamReader;
+  @MonotonicNonNull private ExtractorOutput output;
+  @MonotonicNonNull private StreamReader streamReader;
   private boolean streamReaderInitialized;
 
   @Override
@@ -69,6 +72,7 @@ public class OggExtractor implements Extractor {
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
+    Assertions.checkStateNotNull(output); // Asserts that init has been called.
     if (streamReader == null) {
       if (!sniffInternal(input)) {
         throw new ParserException("Failed to determine bitstream type");
@@ -84,6 +88,7 @@ public class OggExtractor implements Extractor {
     return streamReader.read(input, seekPosition);
   }
 
+  @EnsuresNonNullIf(expression = "streamReader", result = true)
   private boolean sniffInternal(ExtractorInput input) throws IOException, InterruptedException {
     OggPageHeader header = new OggPageHeader();
     if (!header.populate(input, true) || (header.type & 0x02) != 0x02) {

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/OggSeeker.java

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.SeekMap;
 import java.io.IOException;
@@ -27,9 +28,10 @@ import java.io.IOException;
 /* package */ interface OggSeeker {
 
   /**
-   * Returns a {@link SeekMap} that returns an initial estimated position for progressive seeking
-   * or the final position for direct seeking. Returns null if {@link #read} has yet to return -1.
+   * Returns a {@link SeekMap} that returns an initial estimated position for progressive seeking or
+   * the final position for direct seeking. Returns null if {@link #read} has yet to return -1.
    */
+  @Nullable
   SeekMap createSeekMap();
 
   /**

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/StreamReader.java

@@ -25,6 +25,7 @@ import com.google.android.exoplayer2.extractor.SeekMap;
 import com.google.android.exoplayer2.extractor.TrackOutput;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.io.IOException;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
 /** StreamReader abstract class. */
 @SuppressWarnings("UngroupedOverloads")
@@ -42,9 +43,9 @@ import java.io.IOException;
 
   private final OggPacket oggPacket;
 
-  private TrackOutput trackOutput;
-  private ExtractorOutput extractorOutput;
-  private OggSeeker oggSeeker;
+  @MonotonicNonNull private TrackOutput trackOutput;
+  @MonotonicNonNull private ExtractorOutput extractorOutput;
+  @MonotonicNonNull private OggSeeker oggSeeker;
   private long targetGranule;
   private long payloadStartPosition;
   private long currentGranule;

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/VorbisReader.java

@@ -88,7 +88,7 @@ import java.util.ArrayList;
 
   @Override
   protected boolean readHeaders(ParsableByteArray packet, long position, SetupData setupData)
-      throws IOException, InterruptedException {
+      throws IOException {
     if (vorbisSetup != null) {
       return false;
     }

library/core/src/main/java/com/google/android/exoplayer2/extractor/ogg/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.ogg;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/rawcc/RawCcExtractor.java

@@ -24,8 +24,11 @@ import com.google.android.exoplayer2.extractor.ExtractorOutput;
 import com.google.android.exoplayer2.extractor.PositionHolder;
 import com.google.android.exoplayer2.extractor.SeekMap;
 import com.google.android.exoplayer2.extractor.TrackOutput;
+import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.io.IOException;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /**
  * Extracts data from the RawCC container format.
@@ -44,11 +47,9 @@ public final class RawCcExtractor implements Extractor {
   private static final int STATE_READING_SAMPLES = 2;
 
   private final Format format;
-
   private final ParsableByteArray dataScratch;
 
-  private TrackOutput trackOutput;
-
+  @MonotonicNonNull private TrackOutput trackOutput;
   private int parserState;
   private int version;
   private long timestampUs;
@@ -79,6 +80,7 @@ public final class RawCcExtractor implements Extractor {
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
+    Assertions.checkStateNotNull(trackOutput); // Asserts that init has been called.
     while (true) {
       switch (parserState) {
         case STATE_READING_HEADER:
@@ -153,6 +155,7 @@ public final class RawCcExtractor implements Extractor {
     return true;
   }
 
+  @RequiresNonNull("trackOutput")
   private void parseSamples(ExtractorInput input) throws IOException, InterruptedException {
     for (; remainingSampleCount > 0; remainingSampleCount--) {
       dataScratch.reset();
@@ -166,5 +169,4 @@ public final class RawCcExtractor implements Extractor {
       trackOutput.sampleMetadata(timestampUs, C.BUFFER_FLAG_KEY_FRAME, sampleBytesWritten, 0, null);
     }
   }
-
 }

library/core/src/main/java/com/google/android/exoplayer2/extractor/rawcc/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.rawcc;
+
+import com.google.android.exoplayer2.util.NonNullApi;

library/core/src/main/java/com/google/android/exoplayer2/extractor/wav/package-info.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+@NonNullApi
+package com.google.android.exoplayer2.extractor.wav;
+
+import com.google.android.exoplayer2.util.NonNullApi;