Simplify FlacExtractor (step toward enabling nullness checking)

- Inline some unnecessarily split out helper methods
- Clear ExtractorInput from FlacDecoderJni data after usage
- Clean up exception handling for StreamInfo decode failures

PiperOrigin-RevId: 256524955

extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacBinarySearchSeekerTest.java

@@ -52,7 +52,7 @@ public final class FlacBinarySearchSeekerTest {
 
     FlacBinarySearchSeeker seeker =
         new FlacBinarySearchSeeker(
-            decoderJni.decodeMetadata(), /* firstFramePosition= */ 0, data.length, decoderJni);
+            decoderJni.decodeStreamInfo(), /* firstFramePosition= */ 0, data.length, decoderJni);
 
     SeekMap seekMap = seeker.getSeekMap();
     assertThat(seekMap).isNotNull();
@@ -70,7 +70,7 @@ public final class FlacBinarySearchSeekerTest {
     decoderJni.setData(input);
     FlacBinarySearchSeeker seeker =
         new FlacBinarySearchSeeker(
-            decoderJni.decodeMetadata(), /* firstFramePosition= */ 0, data.length, decoderJni);
+            decoderJni.decodeStreamInfo(), /* firstFramePosition= */ 0, data.length, decoderJni);
 
     seeker.setSeekTargetUs(/* timeUs= */ 1000);
     assertThat(seeker.isSeeking()).isTrue();

extensions/flac/src/androidTest/java/com/google/android/exoplayer2/ext/flac/FlacExtractorTest.java

@@ -28,7 +28,7 @@ import org.junit.runner.RunWith;
 public class FlacExtractorTest {
 
   @Before
-  public void setUp() throws Exception {
+  public void setUp() {
     if (!FlacLibrary.isAvailable()) {
       fail("Flac library not available.");
     }

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/FlacDecoder.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.ext.flac;
 
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.ParserException;
 import com.google.android.exoplayer2.decoder.DecoderInputBuffer;
 import com.google.android.exoplayer2.decoder.SimpleDecoder;
 import com.google.android.exoplayer2.decoder.SimpleOutputBuffer;
@@ -59,14 +60,13 @@ import java.util.List;
     decoderJni.setData(ByteBuffer.wrap(initializationData.get(0)));
     FlacStreamInfo streamInfo;
     try {
-      streamInfo = decoderJni.decodeMetadata();
+      streamInfo = decoderJni.decodeStreamInfo();
+    } catch (ParserException e) {
+      throw new FlacDecoderException("Failed to decode StreamInfo", e);
     } catch (IOException | InterruptedException e) {
       // Never happens.
       throw new IllegalStateException(e);
     }
-    if (streamInfo == null) {
-      throw new FlacDecoderException("Metadata decoding failed");
-    }
 
     int initialInputBufferSize =
         maxInputBufferSize != Format.NO_VALUE ? maxInputBufferSize : streamInfo.maxFrameSize;

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/FlacDecoderJni.java

@@ -17,6 +17,7 @@ package com.google.android.exoplayer2.ext.flac;
 
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.ParserException;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.util.FlacStreamInfo;
 import com.google.android.exoplayer2.util.Util;
@@ -48,7 +49,6 @@ import java.nio.ByteBuffer;
   @Nullable private byte[] tempBuffer;
   private boolean endOfExtractorInput;
 
-  @SuppressWarnings("nullness:method.invocation.invalid")
   public FlacDecoderJni() throws FlacDecoderException {
     if (!FlacLibrary.isAvailable()) {
       throw new FlacDecoderException("Failed to load decoder native libraries.");
@@ -60,37 +60,46 @@ import java.nio.ByteBuffer;
   }
 
   /**
-   * Sets data to be parsed by libflac.
+   * Sets the data to be parsed.
    *
    * @param byteBufferData Source {@link ByteBuffer}.
    */
   public void setData(ByteBuffer byteBufferData) {
     this.byteBufferData = byteBufferData;
     this.extractorInput = null;
-    this.tempBuffer = null;
   }
 
   /**
-   * Sets data to be parsed by libflac.
+   * Sets the data to be parsed.
    *
    * @param extractorInput Source {@link ExtractorInput}.
    */
   public void setData(ExtractorInput extractorInput) {
     this.byteBufferData = null;
     this.extractorInput = extractorInput;
-    if (tempBuffer == null) {
-      this.tempBuffer = new byte[TEMP_BUFFER_SIZE];
-    }
     endOfExtractorInput = false;
+    if (tempBuffer == null) {
+      tempBuffer = new byte[TEMP_BUFFER_SIZE];
+    }
   }
 
+  /**
+   * Returns whether the end of the data to be parsed has been reached, or true if no data was set.
+   */
   public boolean isEndOfData() {
     if (byteBufferData != null) {
       return byteBufferData.remaining() == 0;
     } else if (extractorInput != null) {
       return endOfExtractorInput;
+    } else {
+      return true;
     }
-    return true;
+  }
+
+  /** Clears the data to be parsed. */
+  public void clearData() {
+    byteBufferData = null;
+    extractorInput = null;
   }
 
   /**
@@ -99,12 +108,11 @@ import java.nio.ByteBuffer;
    * <p>This method blocks until at least one byte of data can be read, the end of the input is
    * detected or an exception is thrown.
    *
-   * <p>This method is called from the native code.
-   *
    * @param target A target {@link ByteBuffer} into which data should be written.
    * @return Returns the number of bytes read, or -1 on failure. If all of the data has already been
    *     read from the source, then 0 is returned.
    */
+  @SuppressWarnings("unused") // Called from native code.
   public int read(ByteBuffer target) throws IOException, InterruptedException {
     int byteCount = target.remaining();
     if (byteBufferData != null) {
@@ -135,8 +143,12 @@ import java.nio.ByteBuffer;
   }
 
   /** Decodes and consumes the StreamInfo section from the FLAC stream. */
-  public FlacStreamInfo decodeMetadata() throws IOException, InterruptedException {
-    return flacDecodeMetadata(nativeDecoderContext);
+  public FlacStreamInfo decodeStreamInfo() throws IOException, InterruptedException {
+    FlacStreamInfo streamInfo = flacDecodeMetadata(nativeDecoderContext);
+    if (streamInfo == null) {
+      throw new ParserException("Failed to decode StreamInfo");
+    }
+    return streamInfo;
   }
 
   /**

extensions/flac/src/main/java/com/google/android/exoplayer2/ext/flac/FlacExtractor.java

@@ -21,7 +21,7 @@ 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.extractor.BinarySearchSeeker;
+import com.google.android.exoplayer2.extractor.BinarySearchSeeker.OutputFrameHolder;
 import com.google.android.exoplayer2.extractor.Extractor;
 import com.google.android.exoplayer2.extractor.ExtractorInput;
 import com.google.android.exoplayer2.extractor.ExtractorOutput;
@@ -75,22 +75,19 @@ public final class FlacExtractor implements Extractor {
   private static final byte[] FLAC_SIGNATURE = {'f', 'L', 'a', 'C', 0, 0, 0, 0x22};
 
   private final Id3Peeker id3Peeker;
-  private final boolean isId3MetadataDisabled;
+  private final boolean id3MetadataDisabled;
 
-  private FlacDecoderJni decoderJni;
+  @Nullable private FlacDecoderJni decoderJni;
+  @Nullable private ExtractorOutput extractorOutput;
+  @Nullable private TrackOutput trackOutput;
 
-  private ExtractorOutput extractorOutput;
-  private TrackOutput trackOutput;
+  private boolean streamInfoDecoded;
+  @Nullable private FlacStreamInfo streamInfo;
+  @Nullable private ParsableByteArray outputBuffer;
+  @Nullable private OutputFrameHolder outputFrameHolder;
 
-  private ParsableByteArray outputBuffer;
-  private ByteBuffer outputByteBuffer;
-  private BinarySearchSeeker.OutputFrameHolder outputFrameHolder;
-  private FlacStreamInfo streamInfo;
-
-  private Metadata id3Metadata;
-  private @Nullable FlacBinarySearchSeeker flacBinarySearchSeeker;
-
-  private boolean readPastStreamInfo;
+  @Nullable private Metadata id3Metadata;
+  @Nullable private FlacBinarySearchSeeker binarySearchSeeker;
 
   /** Constructs an instance with flags = 0. */
   public FlacExtractor() {
@@ -104,7 +101,7 @@ public final class FlacExtractor implements Extractor {
    */
   public FlacExtractor(int flags) {
     id3Peeker = new Id3Peeker();
-    isId3MetadataDisabled = (flags & FLAG_DISABLE_ID3_METADATA) != 0;
+    id3MetadataDisabled = (flags & FLAG_DISABLE_ID3_METADATA) != 0;
   }
 
   @Override
@@ -130,48 +127,53 @@ public final class FlacExtractor implements Extractor {
   @Override
   public int read(final ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
-    if (input.getPosition() == 0 && !isId3MetadataDisabled && id3Metadata == null) {
+    if (input.getPosition() == 0 && !id3MetadataDisabled && id3Metadata == null) {
       id3Metadata = peekId3Data(input);
     }
 
     decoderJni.setData(input);
-    readPastStreamInfo(input);
-
-    if (flacBinarySearchSeeker != null && flacBinarySearchSeeker.isSeeking()) {
-      return handlePendingSeek(input, seekPosition);
-    }
-
-    long lastDecodePosition = decoderJni.getDecodePosition();
     try {
-      decoderJni.decodeSampleWithBacktrackPosition(outputByteBuffer, lastDecodePosition);
-    } catch (FlacDecoderJni.FlacFrameDecodeException e) {
-      throw new IOException("Cannot read frame at position " + lastDecodePosition, e);
-    }
-    int outputSize = outputByteBuffer.limit();
-    if (outputSize == 0) {
-      return RESULT_END_OF_INPUT;
-    }
+      decodeStreamInfo(input);
 
-    writeLastSampleToOutput(outputSize, decoderJni.getLastFrameTimestamp());
-    return decoderJni.isEndOfData() ? RESULT_END_OF_INPUT : RESULT_CONTINUE;
+      if (binarySearchSeeker != null && binarySearchSeeker.isSeeking()) {
+        return handlePendingSeek(input, seekPosition);
+      }
+
+      ByteBuffer outputByteBuffer = outputFrameHolder.byteBuffer;
+      long lastDecodePosition = decoderJni.getDecodePosition();
+      try {
+        decoderJni.decodeSampleWithBacktrackPosition(outputByteBuffer, lastDecodePosition);
+      } catch (FlacDecoderJni.FlacFrameDecodeException e) {
+        throw new IOException("Cannot read frame at position " + lastDecodePosition, e);
+      }
+      int outputSize = outputByteBuffer.limit();
+      if (outputSize == 0) {
+        return RESULT_END_OF_INPUT;
+      }
+
+      outputSample(outputBuffer, outputSize, decoderJni.getLastFrameTimestamp());
+      return decoderJni.isEndOfData() ? RESULT_END_OF_INPUT : RESULT_CONTINUE;
+    } finally {
+      decoderJni.clearData();
+    }
   }
 
   @Override
   public void seek(long position, long timeUs) {
     if (position == 0) {
-      readPastStreamInfo = false;
+      streamInfoDecoded = false;
     }
     if (decoderJni != null) {
       decoderJni.reset(position);
     }
-    if (flacBinarySearchSeeker != null) {
-      flacBinarySearchSeeker.setSeekTargetUs(timeUs);
+    if (binarySearchSeeker != null) {
+      binarySearchSeeker.setSeekTargetUs(timeUs);
     }
   }
 
   @Override
   public void release() {
-    flacBinarySearchSeeker = null;
+    binarySearchSeeker = null;
     if (decoderJni != null) {
       decoderJni.release();
       decoderJni = null;
@@ -179,16 +181,15 @@ public final class FlacExtractor implements Extractor {
   }
 
   /**
-   * Peeks ID3 tag data (if present) at the beginning of the input.
+   * Peeks ID3 tag data at the beginning of the input.
    *
-   * @return The first ID3 tag decoded into a {@link Metadata} object. May be null if ID3 tag is not
-   *     present in the input.
+   * @return The first ID3 tag {@link Metadata}, or null if an ID3 tag is not present in the input.
    */
   @Nullable
   private Metadata peekId3Data(ExtractorInput input) throws IOException, InterruptedException {
     input.resetPeekPosition();
     Id3Decoder.FramePredicate id3FramePredicate =
-        isId3MetadataDisabled ? Id3Decoder.NO_FRAMES_PREDICATE : null;
+        id3MetadataDisabled ? Id3Decoder.NO_FRAMES_PREDICATE : null;
     return id3Peeker.peekId3Data(input, id3FramePredicate);
   }
 
@@ -199,68 +200,61 @@ public final class FlacExtractor implements Extractor {
    */
   private boolean peekFlacSignature(ExtractorInput input) throws IOException, InterruptedException {
     byte[] header = new byte[FLAC_SIGNATURE.length];
-    input.peekFully(header, 0, FLAC_SIGNATURE.length);
+    input.peekFully(header, /* offset= */ 0, FLAC_SIGNATURE.length);
     return Arrays.equals(header, FLAC_SIGNATURE);
   }
 
-  private void readPastStreamInfo(ExtractorInput input) throws InterruptedException, IOException {
-    if (readPastStreamInfo) {
+  private void decodeStreamInfo(ExtractorInput input) throws InterruptedException, IOException {
+    if (streamInfoDecoded) {
       return;
     }
 
-    FlacStreamInfo streamInfo = decodeStreamInfo(input);
-    readPastStreamInfo = true;
-    if (this.streamInfo == null) {
-      updateFlacStreamInfo(input, streamInfo);
-    }
-  }
-
-  private void updateFlacStreamInfo(ExtractorInput input, FlacStreamInfo streamInfo) {
-    this.streamInfo = streamInfo;
-    outputSeekMap(input, streamInfo);
-    outputFormat(streamInfo);
-    outputBuffer = new ParsableByteArray(streamInfo.maxDecodedFrameSize());
-    outputByteBuffer = ByteBuffer.wrap(outputBuffer.data);
-    outputFrameHolder = new BinarySearchSeeker.OutputFrameHolder(outputByteBuffer);
-  }
-
-  private FlacStreamInfo decodeStreamInfo(ExtractorInput input)
-      throws InterruptedException, IOException {
+    FlacStreamInfo streamInfo;
     try {
-      FlacStreamInfo streamInfo = decoderJni.decodeMetadata();
-      if (streamInfo == null) {
-        throw new IOException("Metadata decoding failed");
-      }
-      return streamInfo;
+      streamInfo = decoderJni.decodeStreamInfo();
     } catch (IOException e) {
-      decoderJni.reset(0);
-      input.setRetryPosition(0, e);
+      decoderJni.reset(/* newPosition= */ 0);
+      input.setRetryPosition(/* position= */ 0, e);
       throw e;
     }
+
+    streamInfoDecoded = true;
+    if (this.streamInfo == null) {
+      this.streamInfo = streamInfo;
+      outputSeekMap(streamInfo, input.getLength());
+      outputFormat(streamInfo, id3MetadataDisabled ? null : id3Metadata);
+      outputBuffer = new ParsableByteArray(streamInfo.maxDecodedFrameSize());
+      outputFrameHolder = new OutputFrameHolder(ByteBuffer.wrap(outputBuffer.data));
+    }
   }
 
-  private void outputSeekMap(ExtractorInput input, FlacStreamInfo streamInfo) {
-    boolean hasSeekTable = decoderJni.getSeekPosition(0) != -1;
-    SeekMap seekMap =
-        hasSeekTable
-            ? new FlacSeekMap(streamInfo.durationUs(), decoderJni)
-            : getSeekMapForNonSeekTableFlac(input, streamInfo);
+  private int handlePendingSeek(ExtractorInput input, PositionHolder seekPosition)
+      throws InterruptedException, IOException {
+    int seekResult = binarySearchSeeker.handlePendingSeek(input, seekPosition, outputFrameHolder);
+    ByteBuffer outputByteBuffer = outputFrameHolder.byteBuffer;
+    if (seekResult == RESULT_CONTINUE && outputByteBuffer.limit() > 0) {
+      outputSample(outputBuffer, outputByteBuffer.limit(), outputFrameHolder.timeUs);
+    }
+    return seekResult;
+  }
+
+  private void outputSeekMap(FlacStreamInfo streamInfo, long inputLength) {
+    boolean hasSeekTable = decoderJni.getSeekPosition(/* timeUs= */ 0) != -1;
+    SeekMap seekMap;
+    if (hasSeekTable) {
+      seekMap = new FlacSeekMap(streamInfo.durationUs(), decoderJni);
+    } else if (inputLength != C.LENGTH_UNSET) {
+      long firstFramePosition = decoderJni.getDecodePosition();
+      binarySearchSeeker =
+          new FlacBinarySearchSeeker(streamInfo, firstFramePosition, inputLength, decoderJni);
+      seekMap = binarySearchSeeker.getSeekMap();
+    } else {
+      seekMap = new SeekMap.Unseekable(streamInfo.durationUs());
+    }
     extractorOutput.seekMap(seekMap);
   }
 
-  private SeekMap getSeekMapForNonSeekTableFlac(ExtractorInput input, FlacStreamInfo streamInfo) {
-    long inputLength = input.getLength();
-    if (inputLength != C.LENGTH_UNSET) {
-      long firstFramePosition = decoderJni.getDecodePosition();
-      flacBinarySearchSeeker =
-          new FlacBinarySearchSeeker(streamInfo, firstFramePosition, inputLength, decoderJni);
-      return flacBinarySearchSeeker.getSeekMap();
-    } else { // can't seek at all, because there's no SeekTable and the input length is unknown.
-      return new SeekMap.Unseekable(streamInfo.durationUs());
-    }
-  }
-
-  private void outputFormat(FlacStreamInfo streamInfo) {
+  private void outputFormat(FlacStreamInfo streamInfo, Metadata metadata) {
     Format mediaFormat =
         Format.createAudioSampleFormat(
             /* id= */ null,
@@ -277,25 +271,15 @@ public final class FlacExtractor implements Extractor {
             /* drmInitData= */ null,
             /* selectionFlags= */ 0,
             /* language= */ null,
-            isId3MetadataDisabled ? null : id3Metadata);
+            metadata);
     trackOutput.format(mediaFormat);
   }
 
-  private int handlePendingSeek(ExtractorInput input, PositionHolder seekPosition)
-      throws InterruptedException, IOException {
-    int seekResult =
-        flacBinarySearchSeeker.handlePendingSeek(input, seekPosition, outputFrameHolder);
-    ByteBuffer outputByteBuffer = outputFrameHolder.byteBuffer;
-    if (seekResult == RESULT_CONTINUE && outputByteBuffer.limit() > 0) {
-      writeLastSampleToOutput(outputByteBuffer.limit(), outputFrameHolder.timeUs);
-    }
-    return seekResult;
-  }
-
-  private void writeLastSampleToOutput(int size, long lastSampleTimestamp) {
-    outputBuffer.setPosition(0);
-    trackOutput.sampleData(outputBuffer, size);
-    trackOutput.sampleMetadata(lastSampleTimestamp, C.BUFFER_FLAG_KEY_FRAME, size, 0, null);
+  private void outputSample(ParsableByteArray sampleData, int size, long timeUs) {
+    sampleData.setPosition(0);
+    trackOutput.sampleData(sampleData, size);
+    trackOutput.sampleMetadata(
+        timeUs, C.BUFFER_FLAG_KEY_FRAME, size, /* offset= */ 0, /* encryptionData= */ null);
   }
 
   /** A {@link SeekMap} implementation using a SeekTable within the Flac stream. */