Support decode-only metadata buffers

PiperOrigin-RevId: 319798613

library/common/src/main/java/com/google/android/exoplayer2/metadata/MetadataDecoder.java

@@ -31,7 +31,8 @@ public interface MetadataDecoder {
    * ByteBuffer#hasArray()} is true.
    *
    * @param inputBuffer The input buffer to decode.
-   * @return The decoded metadata object, or null if the metadata could not be decoded.
+   * @return The decoded metadata object, or {@code null} if the metadata could not be decoded or if
+   *     {@link MetadataInputBuffer#isDecodeOnly()} was set on the input buffer.
    */
   @Nullable
   Metadata decode(MetadataInputBuffer inputBuffer);

library/common/src/main/java/com/google/android/exoplayer2/metadata/SimpleMetadataDecoder.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+package com.google.android.exoplayer2.metadata;
+
+import androidx.annotation.Nullable;
+import com.google.android.exoplayer2.util.Assertions;
+import java.nio.ByteBuffer;
+
+/**
+ * A {@link MetadataDecoder} base class that validates input buffers and discards any for which
+ * {@link MetadataInputBuffer#isDecodeOnly()} is {@code true}.
+ */
+public abstract class SimpleMetadataDecoder implements MetadataDecoder {
+
+  @Override
+  @Nullable
+  public final Metadata decode(MetadataInputBuffer inputBuffer) {
+    ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
+    Assertions.checkArgument(
+        buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
+    return inputBuffer.isDecodeOnly() ? null : decode(inputBuffer, buffer);
+  }
+
+  /**
+   * Called by {@link #decode(MetadataInputBuffer)} after input buffer validation has been
+   * performed, except in the case that {@link MetadataInputBuffer#isDecodeOnly()} is {@code true}.
+   *
+   * @param inputBuffer The input buffer to decode.
+   * @param buffer The input buffer's {@link MetadataInputBuffer#data data buffer}, for convenience.
+   *     Validation by {@link #decode} guarantees that {@link ByteBuffer#hasArray()}, {@link
+   *     ByteBuffer#position()} and {@link ByteBuffer#arrayOffset()} are {@code true}, {@code 0} and
+   *     {@code 0} respectively.
+   * @return The decoded metadata object, or {@code null} if the metadata could not be decoded.
+   */
+  @Nullable
+  protected abstract Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer);
+}

library/common/src/main/java/com/google/android/exoplayer2/metadata/emsg/EventMessageDecoder.java

@@ -16,21 +16,19 @@
 package com.google.android.exoplayer2.metadata.emsg;
 
 import com.google.android.exoplayer2.metadata.Metadata;
-import com.google.android.exoplayer2.metadata.MetadataDecoder;
 import com.google.android.exoplayer2.metadata.MetadataInputBuffer;
+import com.google.android.exoplayer2.metadata.SimpleMetadataDecoder;
 import com.google.android.exoplayer2.util.Assertions;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import java.nio.ByteBuffer;
 import java.util.Arrays;
 
 /** Decodes data encoded by {@link EventMessageEncoder}. */
-public final class EventMessageDecoder implements MetadataDecoder {
+public final class EventMessageDecoder extends SimpleMetadataDecoder {
 
   @Override
-  public Metadata decode(MetadataInputBuffer inputBuffer) {
-    ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
-    Assertions.checkArgument(
-        buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
+  @SuppressWarnings("ByteBufferBackingArray") // Buffer validated by SimpleMetadataDecoder.decode
+  protected Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer) {
     return new Metadata(decode(new ParsableByteArray(buffer.array(), buffer.limit())));
   }
 

library/common/src/main/java/com/google/android/exoplayer2/metadata/id3/Id3Decoder.java

@@ -18,9 +18,8 @@ package com.google.android.exoplayer2.metadata.id3;
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.metadata.Metadata;
-import com.google.android.exoplayer2.metadata.MetadataDecoder;
 import com.google.android.exoplayer2.metadata.MetadataInputBuffer;
-import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.metadata.SimpleMetadataDecoder;
 import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.ParsableBitArray;
 import com.google.android.exoplayer2.util.ParsableByteArray;
@@ -32,10 +31,8 @@ import java.util.Arrays;
 import java.util.List;
 import java.util.Locale;
 
-/**
- * Decodes ID3 tags.
- */
-public final class Id3Decoder implements MetadataDecoder {
+/** Decodes ID3 tags. */
+public final class Id3Decoder extends SimpleMetadataDecoder {
 
   /**
    * A predicate for determining whether individual frames should be decoded.
@@ -98,10 +95,8 @@ public final class Id3Decoder implements MetadataDecoder {
 
   @Override
   @Nullable
-  public Metadata decode(MetadataInputBuffer inputBuffer) {
-    ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
-    Assertions.checkArgument(
-        buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
+  @SuppressWarnings("ByteBufferBackingArray") // Buffer validated by SimpleMetadataDecoder.decode
+  protected Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer) {
     return decode(buffer.array(), buffer.limit());
   }
 
@@ -118,7 +113,7 @@ public final class Id3Decoder implements MetadataDecoder {
     List<Id3Frame> id3Frames = new ArrayList<>();
     ParsableByteArray id3Data = new ParsableByteArray(data, size);
 
-    Id3Header id3Header = decodeHeader(id3Data);
+    @Nullable Id3Header id3Header = decodeHeader(id3Data);
     if (id3Header == null) {
       return null;
     }
@@ -142,8 +137,14 @@ public final class Id3Decoder implements MetadataDecoder {
     }
 
     while (id3Data.bytesLeft() >= frameHeaderSize) {
-      Id3Frame frame = decodeFrame(id3Header.majorVersion, id3Data, unsignedIntFrameSizeHack,
-          frameHeaderSize, framePredicate);
+      @Nullable
+      Id3Frame frame =
+          decodeFrame(
+              id3Header.majorVersion,
+              id3Data,
+              unsignedIntFrameSizeHack,
+              frameHeaderSize,
+              framePredicate);
       if (frame != null) {
         id3Frames.add(frame);
       }
@@ -660,8 +661,10 @@ public final class Id3Decoder implements MetadataDecoder {
     ArrayList<Id3Frame> subFrames = new ArrayList<>();
     int limit = framePosition + frameSize;
     while (id3Data.getPosition() < limit) {
-      Id3Frame frame = decodeFrame(majorVersion, id3Data, unsignedIntFrameSizeHack,
-          frameHeaderSize, framePredicate);
+      @Nullable
+      Id3Frame frame =
+          decodeFrame(
+              majorVersion, id3Data, unsignedIntFrameSizeHack, frameHeaderSize, framePredicate);
       if (frame != null) {
         subFrames.add(frame);
       }

library/common/src/test/java/com/google/android/exoplayer2/metadata/SimpleMetadataDecoderTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+package com.google.android.exoplayer2.metadata;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertThrows;
+
+import androidx.annotation.Nullable;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import com.google.android.exoplayer2.C;
+import java.nio.ByteBuffer;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Tests for {@link SimpleMetadataDecoder}. */
+@RunWith(AndroidJUnit4.class)
+public class SimpleMetadataDecoderTest {
+
+  @Test
+  public void decode_nullDataInputBuffer_throwsNullPointerException() {
+    TestSimpleMetadataDecoder decoder = new TestSimpleMetadataDecoder();
+    MetadataInputBuffer nullDataInputBuffer = new MetadataInputBuffer();
+    nullDataInputBuffer.data = null;
+
+    assertThrows(NullPointerException.class, () -> decoder.decode(nullDataInputBuffer));
+    assertThat(decoder.decodeWasCalled).isFalse();
+  }
+
+  @Test
+  public void decode_directDataInputBuffer_throwsIllegalArgumentException() {
+    TestSimpleMetadataDecoder decoder = new TestSimpleMetadataDecoder();
+    MetadataInputBuffer directDataInputBuffer = new MetadataInputBuffer();
+    directDataInputBuffer.data = ByteBuffer.allocateDirect(8);
+
+    assertThrows(IllegalArgumentException.class, () -> decoder.decode(directDataInputBuffer));
+    assertThat(decoder.decodeWasCalled).isFalse();
+  }
+
+  @Test
+  public void decode_nonZeroPositionDataInputBuffer_throwsIllegalArgumentException() {
+    TestSimpleMetadataDecoder decoder = new TestSimpleMetadataDecoder();
+    MetadataInputBuffer nonZeroPositionDataInputBuffer = new MetadataInputBuffer();
+    nonZeroPositionDataInputBuffer.data = ByteBuffer.wrap(new byte[8]);
+    nonZeroPositionDataInputBuffer.data.position(1);
+
+    assertThrows(
+        IllegalArgumentException.class, () -> decoder.decode(nonZeroPositionDataInputBuffer));
+    assertThat(decoder.decodeWasCalled).isFalse();
+  }
+
+  @Test
+  public void decode_nonZeroOffsetDataInputBuffer_throwsIllegalArgumentException() {
+    TestSimpleMetadataDecoder decoder = new TestSimpleMetadataDecoder();
+    MetadataInputBuffer directDataInputBuffer = new MetadataInputBuffer();
+    directDataInputBuffer.data = ByteBuffer.wrap(new byte[8], /* offset= */ 4, /* length= */ 4);
+
+    assertThrows(IllegalArgumentException.class, () -> decoder.decode(directDataInputBuffer));
+    assertThat(decoder.decodeWasCalled).isFalse();
+  }
+
+  @Test
+  public void decode_decodeOnlyBuffer_notPassedToDecodeInternal() {
+    TestSimpleMetadataDecoder decoder = new TestSimpleMetadataDecoder();
+    MetadataInputBuffer decodeOnlyBuffer = new MetadataInputBuffer();
+    decodeOnlyBuffer.data = ByteBuffer.wrap(new byte[8]);
+    decodeOnlyBuffer.setFlags(C.BUFFER_FLAG_DECODE_ONLY);
+
+    assertThat(decoder.decode(decodeOnlyBuffer)).isNull();
+    assertThat(decoder.decodeWasCalled).isFalse();
+  }
+
+  @Test
+  public void decode_returnsDecodeInternalResult() {
+    TestSimpleMetadataDecoder decoder = new TestSimpleMetadataDecoder();
+    MetadataInputBuffer buffer = new MetadataInputBuffer();
+    buffer.data = ByteBuffer.wrap(new byte[8]);
+
+    assertThat(decoder.decode(buffer)).isSameInstanceAs(decoder.result);
+    assertThat(decoder.decodeWasCalled).isTrue();
+  }
+
+  private static final class TestSimpleMetadataDecoder extends SimpleMetadataDecoder {
+
+    public final Metadata result;
+
+    public boolean decodeWasCalled;
+
+    public TestSimpleMetadataDecoder() {
+      result = new Metadata();
+    }
+
+    @Nullable
+    @Override
+    protected Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer) {
+      decodeWasCalled = true;
+      return result;
+    }
+  }
+}

library/core/src/main/java/com/google/android/exoplayer2/metadata/MetadataRenderer.java

@@ -129,10 +129,6 @@ public final class MetadataRenderer extends BaseRenderer implements Callback {
       if (result == C.RESULT_BUFFER_READ) {
         if (buffer.isEndOfStream()) {
           inputStreamEnded = true;
-        } else if (buffer.isDecodeOnly()) {
-          // Do nothing. Note this assumes that all metadata buffers can be decoded independently.
-          // If we ever need to support a metadata format where this is not the case, we'll need to
-          // pass the buffer to the decoder and discard the output.
         } else {
           buffer.subsampleOffsetUs = subsampleOffsetUs;
           buffer.flip();

library/core/src/main/java/com/google/android/exoplayer2/metadata/dvbsi/AppInfoTableDecoder.java

@@ -17,9 +17,8 @@ package com.google.android.exoplayer2.metadata.dvbsi;
 
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.metadata.Metadata;
-import com.google.android.exoplayer2.metadata.MetadataDecoder;
 import com.google.android.exoplayer2.metadata.MetadataInputBuffer;
-import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.metadata.SimpleMetadataDecoder;
 import com.google.android.exoplayer2.util.ParsableBitArray;
 import com.google.common.base.Charsets;
 import java.nio.ByteBuffer;
@@ -32,7 +31,7 @@ import java.util.ArrayList;
  * href="https://www.etsi.org/deliver/etsi_ts/102800_102899/102809/01.01.01_60/ts_102809v010101p.pdf">
  * DVB ETSI TS 102 809 v1.1.1 spec</a>.
  */
-public final class AppInfoTableDecoder implements MetadataDecoder {
+public final class AppInfoTableDecoder extends SimpleMetadataDecoder {
 
   /** See section 5.3.6. */
   private static final int DESCRIPTOR_TRANSPORT_PROTOCOL = 0x02;
@@ -47,10 +46,8 @@ public final class AppInfoTableDecoder implements MetadataDecoder {
 
   @Override
   @Nullable
-  public Metadata decode(MetadataInputBuffer inputBuffer) {
-    ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
-    Assertions.checkArgument(
-        buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
+  @SuppressWarnings("ByteBufferBackingArray") // Buffer validated by SimpleMetadataDecoder.decode
+  protected Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer) {
     int tableId = buffer.get();
     return tableId == APPLICATION_INFORMATION_TABLE_ID
         ? parseAit(new ParsableBitArray(buffer.array(), buffer.limit()))

library/core/src/main/java/com/google/android/exoplayer2/metadata/icy/IcyDecoder.java

@@ -17,9 +17,8 @@ package com.google.android.exoplayer2.metadata.icy;
 
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.metadata.Metadata;
-import com.google.android.exoplayer2.metadata.MetadataDecoder;
 import com.google.android.exoplayer2.metadata.MetadataInputBuffer;
-import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.metadata.SimpleMetadataDecoder;
 import com.google.android.exoplayer2.util.Util;
 import com.google.common.base.Charsets;
 import java.nio.ByteBuffer;
@@ -29,7 +28,7 @@ import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
 /** Decodes ICY stream information. */
-public final class IcyDecoder implements MetadataDecoder {
+public final class IcyDecoder extends SimpleMetadataDecoder {
 
   private static final Pattern METADATA_ELEMENT = Pattern.compile("(.+?)='(.*?)';", Pattern.DOTALL);
   private static final String STREAM_KEY_NAME = "streamtitle";
@@ -44,10 +43,7 @@ public final class IcyDecoder implements MetadataDecoder {
   }
 
   @Override
-  public Metadata decode(MetadataInputBuffer inputBuffer) {
-    ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
-    Assertions.checkArgument(
-        buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
+  protected Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer) {
     @Nullable String icyString = decodeToString(buffer);
     byte[] icyBytes = new byte[buffer.limit()];
     buffer.get(icyBytes);

library/core/src/main/java/com/google/android/exoplayer2/metadata/scte35/SpliceInfoDecoder.java

@@ -17,19 +17,16 @@ package com.google.android.exoplayer2.metadata.scte35;
 
 import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.metadata.Metadata;
-import com.google.android.exoplayer2.metadata.MetadataDecoder;
 import com.google.android.exoplayer2.metadata.MetadataInputBuffer;
-import com.google.android.exoplayer2.util.Assertions;
+import com.google.android.exoplayer2.metadata.SimpleMetadataDecoder;
 import com.google.android.exoplayer2.util.ParsableBitArray;
 import com.google.android.exoplayer2.util.ParsableByteArray;
 import com.google.android.exoplayer2.util.TimestampAdjuster;
 import java.nio.ByteBuffer;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 
-/**
- * Decodes splice info sections and produces splice commands.
- */
-public final class SpliceInfoDecoder implements MetadataDecoder {
+/** Decodes splice info sections and produces splice commands. */
+public final class SpliceInfoDecoder extends SimpleMetadataDecoder {
 
   private static final int TYPE_SPLICE_NULL = 0x00;
   private static final int TYPE_SPLICE_SCHEDULE = 0x04;
@@ -48,11 +45,8 @@ public final class SpliceInfoDecoder implements MetadataDecoder {
   }
 
   @Override
-  public Metadata decode(MetadataInputBuffer inputBuffer) {
-    ByteBuffer buffer = Assertions.checkNotNull(inputBuffer.data);
-    Assertions.checkArgument(
-        buffer.position() == 0 && buffer.hasArray() && buffer.arrayOffset() == 0);
-
+  @SuppressWarnings("ByteBufferBackingArray") // Buffer validated by SimpleMetadataDecoder.decode
+  protected Metadata decode(MetadataInputBuffer inputBuffer, ByteBuffer buffer) {
     // Internal timestamps adjustment.
     if (timestampAdjuster == null
         || inputBuffer.subsampleOffsetUs != timestampAdjuster.getTimestampOffsetUs()) {

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

@@ -361,12 +361,15 @@ public final class PlayerEmsgHandler implements Handler.Callback {
 
     private void parseAndDiscardSamples() {
       while (sampleQueue.isReady(/* loadingFinished= */ false)) {
-        MetadataInputBuffer inputBuffer = dequeueSample();
+        @Nullable MetadataInputBuffer inputBuffer = dequeueSample();
         if (inputBuffer == null) {
           continue;
         }
         long eventTimeUs = inputBuffer.timeUs;
-        Metadata metadata = decoder.decode(inputBuffer);
+        @Nullable Metadata metadata = decoder.decode(inputBuffer);
+        if (metadata == null) {
+          continue;
+        }
         EventMessage eventMessage = (EventMessage) metadata.get(0);
         if (isPlayerEmsgEvent(eventMessage.schemeIdUri, eventMessage.value)) {
           parsePlayerEmsgEvent(eventTimeUs, eventMessage);