Fix some extractor nullness checks

Fix Matroska, Heif, FLAC, Ogg, Opus, Vorbis
extractor nullness check.

There should be no functional change.
Every media that fail to be parsed should still fail.
Every media that parsed successfully should still succeed.

This refactor aims to push all nullness constraints up the call stack to clarify each API nullness contract. This ensures implementation and caller have to prove their respective contract close to where such logic is implemented. This also allows to fail early if an nullness contract is broken instead of deep in the call stack.

For example, by adding a requirement that all implementation of `StreamReader.readHeaders` have to initialize `setupData.format` if the return false, each overriding method is forced to prove this next to the logic initializing it. This also means the runtime check might not be needed because the nullnessChecker can prove itself the contract holds.

This is in contrast with adding a null check at the point of usage, which will not catch logic errors where they are produce, but later when they are perceived; making it harder to debug and catching the issue at run time instead of compile time.

#exofixit

PiperOrigin-RevId: 346163124

library/extractor/src/main/java/com/google/android/exoplayer2/extractor/mp4/PsshAtomUtil.java

@@ -138,7 +138,7 @@ public final class PsshAtomUtil {
     if (parsedAtom == null) {
       return null;
     }
-    if (uuid != null && !uuid.equals(parsedAtom.uuid)) {
+    if (!uuid.equals(parsedAtom.uuid)) {
       Log.w(TAG, "UUID mismatch. Expected: " + uuid + ", got: " + parsedAtom.uuid + ".");
       return null;
     }

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

@@ -15,6 +15,9 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
+import static com.google.android.exoplayer2.util.Assertions.checkState;
+
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.FlacFrameReader;
@@ -23,11 +26,11 @@ import com.google.android.exoplayer2.extractor.FlacSeekTableSeekMap;
 import com.google.android.exoplayer2.extractor.FlacStreamMetadata;
 import com.google.android.exoplayer2.extractor.FlacStreamMetadata.SeekTable;
 import com.google.android.exoplayer2.extractor.SeekMap;
-import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.FlacConstants;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.Util;
 import java.util.Arrays;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 
 /**
  * {@link StreamReader} to extract Flac data out of Ogg byte stream.
@@ -68,6 +71,7 @@ import java.util.Arrays;
   }
 
   @Override
+  @EnsuresNonNullIf(expression = "#3.format", result = false)
   protected boolean readHeaders(ParsableByteArray packet, long position, SetupData setupData) {
     byte[] data = packet.getData();
     @Nullable FlacStreamMetadata streamMetadata = this.streamMetadata;
@@ -76,18 +80,26 @@ import java.util.Arrays;
       this.streamMetadata = streamMetadata;
       byte[] metadata = Arrays.copyOfRange(data, 9, packet.limit());
       setupData.format = streamMetadata.getFormat(metadata, /* id3Metadata= */ null);
-    } else if ((data[0] & 0x7F) == FlacConstants.METADATA_TYPE_SEEK_TABLE) {
+      return true;
+    }
+
+    if ((data[0] & 0x7F) == FlacConstants.METADATA_TYPE_SEEK_TABLE) {
       SeekTable seekTable = FlacMetadataReader.readSeekTableMetadataBlock(packet);
       streamMetadata = streamMetadata.copyWithSeekTable(seekTable);
       this.streamMetadata = streamMetadata;
       flacOggSeeker = new FlacOggSeeker(streamMetadata, seekTable);
-    } else if (isAudioPacket(data)) {
+      return true;
+    }
+
+    if (isAudioPacket(data)) {
       if (flacOggSeeker != null) {
         flacOggSeeker.setFirstFrameOffset(position);
         setupData.oggSeeker = flacOggSeeker;
       }
+      checkNotNull(setupData.format);
       return false;
     }
+
     return true;
   }
 
@@ -142,7 +154,7 @@ import java.util.Arrays;
 
     @Override
     public SeekMap createSeekMap() {
-      Assertions.checkState(firstFrameOffset != -1);
+      checkState(firstFrameOffset != -1);
       return new FlacSeekTableSeekMap(streamMetadata, firstFrameOffset);
     }
 

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

@@ -15,6 +15,7 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
 import static java.lang.Math.min;
 
 import com.google.android.exoplayer2.C;
@@ -25,7 +26,6 @@ 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;
@@ -73,7 +73,7 @@ public class OggExtractor implements Extractor {
 
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition) throws IOException {
-    Assertions.checkStateNotNull(output); // Asserts that init has been called.
+    checkStateNotNull(output); // Check that init has been called.
     if (streamReader == null) {
       if (!sniffInternal(input)) {
         throw new ParserException("Failed to determine bitstream type");

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

@@ -15,12 +15,15 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
+
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.audio.OpusUtil;
 import com.google.android.exoplayer2.util.MimeTypes;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.util.Arrays;
 import java.util.List;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 
 /**
  * {@link StreamReader} to extract Opus data out of Ogg byte stream.
@@ -55,6 +58,7 @@ import java.util.List;
   }
 
   @Override
+  @EnsuresNonNullIf(expression = "#3.format", result = false)
   protected boolean readHeaders(ParsableByteArray packet, long position, SetupData setupData) {
     if (!headerRead) {
       byte[] headerBytes = Arrays.copyOf(packet.getData(), packet.limit());
@@ -68,12 +72,13 @@ import java.util.List;
               .setInitializationData(initializationData)
               .build();
       headerRead = true;
+      return true;
     } else {
+      checkNotNull(setupData.format); // Has been set when the header was read.
       boolean headerPacket = packet.readInt() == OPUS_CODE;
       packet.setPosition(0);
       return headerPacket;
     }
-    return true;
   }
 
   /**

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

@@ -15,7 +15,9 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
-import androidx.annotation.Nullable;
+import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
+import static com.google.android.exoplayer2.util.Util.castNonNull;
+
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.Format;
 import com.google.android.exoplayer2.extractor.Extractor;
@@ -24,10 +26,12 @@ 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.EnsuresNonNull;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
 /** StreamReader abstract class. */
 @SuppressWarnings("UngroupedOverloads")
@@ -39,8 +43,8 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   private static final int STATE_END_OF_INPUT = 3;
 
   static class SetupData {
-    Format format;
-    OggSeeker oggSeeker;
+    @MonotonicNonNull Format format;
+    @MonotonicNonNull OggSeeker oggSeeker;
   }
 
   private final OggPacket oggPacket;
@@ -53,13 +57,14 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
   private long currentGranule;
   private int state;
   private int sampleRate;
-  @Nullable private SetupData setupData;
+  private SetupData setupData;
   private long lengthOfReadPacket;
   private boolean seekMapSet;
   private boolean formatSet;
 
   public StreamReader() {
     oggPacket = new OggPacket();
+    setupData = new SetupData();
   }
 
   void init(ExtractorOutput output, TrackOutput trackOutput) {
@@ -95,7 +100,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     } else {
       if (state != STATE_READ_HEADERS) {
         targetGranule = convertTimeToGranule(timeUs);
-        oggSeeker.startSeek(targetGranule);
+        castNonNull(oggSeeker).startSeek(targetGranule);
         state = STATE_READ_PAYLOAD;
       }
     }
@@ -103,14 +108,16 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
   /** @see Extractor#read(ExtractorInput, PositionHolder) */
   final int read(ExtractorInput input, PositionHolder seekPosition) throws IOException {
+    assertInitialized();
     switch (state) {
       case STATE_READ_HEADERS:
-        return readHeaders(input);
+        return readHeadersAndUpdateState(input);
       case STATE_SKIP_HEADERS:
         input.skipFully((int) payloadStartPosition);
         state = STATE_READ_PAYLOAD;
         return Extractor.RESULT_CONTINUE;
       case STATE_READ_PAYLOAD:
+        castNonNull(oggSeeker);
         return readPayload(input, seekPosition);
       default:
         // Never happens.
@@ -118,20 +125,42 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     }
   }
 
-  private int readHeaders(ExtractorInput input) throws IOException {
-    boolean readingHeaders = true;
-    while (readingHeaders) {
+  @EnsuresNonNull({"trackOutput", "extractorOutput"})
+  private void assertInitialized() {
+    checkStateNotNull(trackOutput);
+    castNonNull(extractorOutput);
+  }
+
+  /**
+   * Read all header packets.
+   *
+   * @param input The {@link ExtractorInput} to read data from.
+   * @return {@code true} if all headers were read. {@code false} if end of the input is
+   *     encountered.
+   * @throws IOException If reading from the input fails.
+   */
+  @EnsuresNonNullIf(expression = "setupData.format", result = true)
+  private boolean readHeaders(ExtractorInput input) throws IOException {
+    while (true) {
       if (!oggPacket.populate(input)) {
         state = STATE_END_OF_INPUT;
-        return Extractor.RESULT_END_OF_INPUT;
+        return false;
       }
       lengthOfReadPacket = input.getPosition() - payloadStartPosition;
 
-      readingHeaders = readHeaders(oggPacket.getPayload(), payloadStartPosition, setupData);
-      if (readingHeaders) {
+      if (readHeaders(oggPacket.getPayload(), payloadStartPosition, setupData)) {
         payloadStartPosition = input.getPosition();
+      } else {
+        return true; // Current packet is not a header, therefore all headers have been read.
       }
     }
+  }
+
+  @RequiresNonNull({"trackOutput"})
+  private int readHeadersAndUpdateState(ExtractorInput input) throws IOException {
+    if (!readHeaders(input)) {
+      return Extractor.RESULT_END_OF_INPUT;
+    }
 
     sampleRate = setupData.format.sampleRate;
     if (!formatSet) {
@@ -156,13 +185,13 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
               isLastPage);
     }
 
-    setupData = null;
     state = STATE_READ_PAYLOAD;
     // First payload packet. Trim the payload array of the ogg packet after headers have been read.
     oggPacket.trimPayload();
     return Extractor.RESULT_CONTINUE;
   }
 
+  @RequiresNonNull({"trackOutput", "oggSeeker", "extractorOutput"})
   private int readPayload(ExtractorInput input, PositionHolder seekPosition) throws IOException {
     long position = oggSeeker.read(input);
     if (position >= 0) {
@@ -173,7 +202,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     }
 
     if (!seekMapSet) {
-      SeekMap seekMap = Assertions.checkStateNotNull(oggSeeker.createSeekMap());
+      SeekMap seekMap = checkStateNotNull(oggSeeker.createSeekMap());
       extractorOutput.seekMap(seekMap);
       seekMapSet = true;
     }
@@ -234,6 +263,7 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
    * @param setupData Setup data to be filled.
    * @return Whether the packet contains header data.
    */
+  @EnsuresNonNullIf(expression = "#3.format", result = false)
   protected abstract boolean readHeaders(
       ParsableByteArray packet, long position, SetupData setupData) throws IOException;
 

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

@@ -15,6 +15,9 @@
  */
 package com.google.android.exoplayer2.extractor.ogg;
 
+import static com.google.android.exoplayer2.util.Assertions.checkNotNull;
+import static com.google.android.exoplayer2.util.Assertions.checkStateNotNull;
+
 import androidx.annotation.Nullable;
 import androidx.annotation.VisibleForTesting;
 import com.google.android.exoplayer2.Format;
@@ -26,6 +29,7 @@ import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 
 /**
  * {@link StreamReader} to extract Vorbis data out of Ogg byte stream.
@@ -74,7 +78,7 @@ import java.util.Arrays;
     }
 
     // ... we need to decode the block size
-    int packetBlockSize = decodeBlockSize(packet.getData()[0], vorbisSetup);
+    int packetBlockSize = decodeBlockSize(packet.getData()[0], checkStateNotNull(vorbisSetup));
     // a packet contains samples produced from overlapping the previous and current frame data
     // (https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-350001.3.2)
     int samplesInPacket = seenFirstAudioPacket ? (packetBlockSize + previousPacketBlockSize) / 4
@@ -89,9 +93,11 @@ import java.util.Arrays;
   }
 
   @Override
+  @EnsuresNonNullIf(expression = "#3.format", result = false)
   protected boolean readHeaders(ParsableByteArray packet, long position, SetupData setupData)
       throws IOException {
     if (vorbisSetup != null) {
+      checkNotNull(setupData.format);
       return false;
     }
 
@@ -99,6 +105,7 @@ import java.util.Arrays;
     if (vorbisSetup == null) {
       return true;
     }
+    VorbisSetup vorbisSetup = this.vorbisSetup;
 
     VorbisUtil.VorbisIdHeader idHeader = vorbisSetup.idHeader;
 
@@ -131,6 +138,8 @@ import java.util.Arrays;
       commentHeader = VorbisUtil.readVorbisCommentHeader(scratch);
       return null;
     }
+    VorbisUtil.VorbisIdHeader vorbisIdHeader = this.vorbisIdHeader;
+    VorbisUtil.CommentHeader commentHeader = this.commentHeader;
 
     // the third packet contains the setup header
     byte[] setupHeaderData = new byte[scratch.limit()];