Clean up MP3 synchronization and fix handling < 4 frames.

Also add a test MP3 stream with one frame.

Make FakeExtractorInput's end of input detection to apply also for peekFully, and
make its skip and read methods read at least one byte.

Issue: #1732

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133241641

library/src/androidTest/assets/mp3/play-trimmed.mp3.0.dump

+seekMap:
+  isSeekable = true
+  duration = 26125
+  getPosition(0) = 0
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = -1
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/mpeg
+    maxInputSize = 4096
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = -1
+    pixelWidthHeightRatio = -1.0
+    channelCount = 2
+    sampleRate = 44100
+    pcmEncoding = -1
+    encoderDelay = -1
+    encoderPadding = -1
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  sample count = 1
+  sample 0:
+    time = 0
+    flags = 1
+    data = length 418, hash B819987
+tracksEnded = true

library/src/androidTest/assets/mp3/play-trimmed.mp3.1.dump

+seekMap:
+  isSeekable = true
+  duration = 26125
+  getPosition(0) = 0
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = -1
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/mpeg
+    maxInputSize = 4096
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = -1
+    pixelWidthHeightRatio = -1.0
+    channelCount = 2
+    sampleRate = 44100
+    pcmEncoding = -1
+    encoderDelay = -1
+    encoderPadding = -1
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  sample count = 0
+tracksEnded = true

library/src/androidTest/assets/mp3/play-trimmed.mp3.2.dump

+seekMap:
+  isSeekable = true
+  duration = 26125
+  getPosition(0) = 0
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = -1
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/mpeg
+    maxInputSize = 4096
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = -1
+    pixelWidthHeightRatio = -1.0
+    channelCount = 2
+    sampleRate = 44100
+    pcmEncoding = -1
+    encoderDelay = -1
+    encoderPadding = -1
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  sample count = 0
+tracksEnded = true

library/src/androidTest/assets/mp3/play-trimmed.mp3.3.dump

+seekMap:
+  isSeekable = true
+  duration = 26125
+  getPosition(0) = 0
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = -1
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/mpeg
+    maxInputSize = 4096
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = -1
+    pixelWidthHeightRatio = -1.0
+    channelCount = 2
+    sampleRate = 44100
+    pcmEncoding = -1
+    encoderDelay = -1
+    encoderPadding = -1
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  sample count = 0
+tracksEnded = true

library/src/androidTest/assets/mp3/play-trimmed.mp3.unklen.dump

+seekMap:
+  isSeekable = false
+  duration = UNSET TIME
+  getPosition(0) = 0
+numberOfTracks = 1
+track 0:
+  format:
+    bitrate = -1
+    id = null
+    containerMimeType = null
+    sampleMimeType = audio/mpeg
+    maxInputSize = 4096
+    width = -1
+    height = -1
+    frameRate = -1.0
+    rotationDegrees = -1
+    pixelWidthHeightRatio = -1.0
+    channelCount = 2
+    sampleRate = 44100
+    pcmEncoding = -1
+    encoderDelay = -1
+    encoderPadding = -1
+    subsampleOffsetUs = 9223372036854775807
+    selectionFlags = 0
+    language = null
+    drmInitData = -
+    initializationData:
+  sample count = 1
+  sample 0:
+    time = 0
+    flags = 1
+    data = length 418, hash B819987
+tracksEnded = true

library/src/androidTest/java/com/google/android/exoplayer2/extractor/mp3/Mp3ExtractorTest.java

@@ -33,4 +33,13 @@ public final class Mp3ExtractorTest extends InstrumentationTestCase {
     }, "mp3/bear.mp3", getInstrumentation());
   }
 
+  public void testTrimmedMp3Sample() throws Exception {
+    TestUtil.assertOutput(new TestUtil.ExtractorFactory() {
+      @Override
+      public Extractor create() {
+        return new Mp3Extractor();
+      }
+    }, "mp3/play-trimmed.mp3", getInstrumentation());
+  }
+
 }

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

@@ -131,8 +131,12 @@ public final class Mp3Extractor implements Extractor {
   @Override
   public int read(ExtractorInput input, PositionHolder seekPosition)
       throws IOException, InterruptedException {
-    if (synchronizedHeaderData == 0 && !synchronizeCatchingEndOfInput(input)) {
-      return RESULT_END_OF_INPUT;
+    if (synchronizedHeaderData == 0) {
+      try {
+        synchronize(input, false);
+      } catch (EOFException e) {
+        return RESULT_END_OF_INPUT;
+      }
     }
     if (seeker == null) {
       seeker = setupSeeker(input);
@@ -147,9 +151,20 @@ public final class Mp3Extractor implements Extractor {
 
   private int readSample(ExtractorInput extractorInput) throws IOException, InterruptedException {
     if (sampleBytesRemaining == 0) {
-      if (!maybeResynchronize(extractorInput)) {
+      extractorInput.resetPeekPosition();
+      if (!extractorInput.peekFully(scratch.data, 0, 4, true)) {
         return RESULT_END_OF_INPUT;
       }
+      scratch.setPosition(0);
+      int sampleHeaderData = scratch.readInt();
+      if ((sampleHeaderData & HEADER_MASK) != (synchronizedHeaderData & HEADER_MASK)
+          || MpegAudioHeader.getFrameSize(sampleHeaderData) == C.LENGTH_UNSET) {
+        // We have lost synchronization, so attempt to resynchronize starting at the next byte.
+        extractorInput.skipFully(1);
+        synchronizedHeaderData = 0;
+        return RESULT_CONTINUE;
+      }
+      MpegAudioHeader.populateHeader(sampleHeaderData, synchronizedHeader);
       if (basisTimeUs == C.TIME_UNSET) {
         basisTimeUs = seeker.getTimeUs(extractorInput.getPosition());
         if (forcedFirstSampleTimestampUs != C.TIME_UNSET) {
@@ -175,49 +190,13 @@ public final class Mp3Extractor implements Extractor {
     return RESULT_CONTINUE;
   }
 
-  /**
-   * Attempts to read an MPEG audio header at the current offset, resynchronizing if necessary.
-   */
-  private boolean maybeResynchronize(ExtractorInput extractorInput)
-      throws IOException, InterruptedException {
-    extractorInput.resetPeekPosition();
-    if (!extractorInput.peekFully(scratch.data, 0, 4, true)) {
-      return false;
-    }
-
-    scratch.setPosition(0);
-    int sampleHeaderData = scratch.readInt();
-    if ((sampleHeaderData & HEADER_MASK) == (synchronizedHeaderData & HEADER_MASK)) {
-      int frameSize = MpegAudioHeader.getFrameSize(sampleHeaderData);
-      if (frameSize != C.LENGTH_UNSET) {
-        MpegAudioHeader.populateHeader(sampleHeaderData, synchronizedHeader);
-        return true;
-      }
-    }
-
-    synchronizedHeaderData = 0;
-    extractorInput.skipFully(1);
-    return synchronizeCatchingEndOfInput(extractorInput);
-  }
-
-  private boolean synchronizeCatchingEndOfInput(ExtractorInput input)
-      throws IOException, InterruptedException {
-    // An EOFException will be raised if any peek operation was partially satisfied. If a seek
-    // operation resulted in reading from within the last frame, we may try to peek past the end of
-    // the file in a partially-satisfied read operation, so we need to catch the exception.
-    try {
-      return synchronize(input, false);
-    } catch (EOFException e) {
-      return false;
-    }
-  }
-
   private boolean synchronize(ExtractorInput input, boolean sniffing)
       throws IOException, InterruptedException {
-    int searched = 0;
     int validFrameCount = 0;
     int candidateSynchronizedHeaderData = 0;
     int peekedId3Bytes = 0;
+    int searchedBytes = 0;
+    int searchLimitBytes = sniffing ? MAX_SNIFF_BYTES : MAX_SYNC_BYTES;
     input.resetPeekPosition();
     if (input.getPosition() == 0) {
       Id3Util.parseId3(input, gaplessInfoHolder);
@@ -227,14 +206,9 @@ public final class Mp3Extractor implements Extractor {
       }
     }
     while (true) {
-      if (sniffing && searched == MAX_SNIFF_BYTES) {
-        return false;
-      }
-      if (!sniffing && searched == MAX_SYNC_BYTES) {
-        throw new ParserException("Searched too many bytes.");
-      }
-      if (!input.peekFully(scratch.data, 0, 4, true)) {
-        return false;
+      if (!input.peekFully(scratch.data, 0, 4, validFrameCount > 0)) {
+        // We reached the end of the stream but found at least one valid frame.
+        break;
       }
       scratch.setPosition(0);
       int headerData = scratch.readInt();
@@ -242,18 +216,23 @@ public final class Mp3Extractor implements Extractor {
       if ((candidateSynchronizedHeaderData != 0
           && (headerData & HEADER_MASK) != (candidateSynchronizedHeaderData & HEADER_MASK))
           || (frameSize = MpegAudioHeader.getFrameSize(headerData)) == C.LENGTH_UNSET) {
-        // The header is invalid or doesn't match the candidate header. Try the next byte offset.
+        // The header doesn't match the candidate header or is invalid. Try the next byte offset.
+        if (searchedBytes++ == searchLimitBytes) {
+          if (!sniffing) {
+            throw new ParserException("Searched too many bytes.");
+          }
+          return false;
+        }
         validFrameCount = 0;
         candidateSynchronizedHeaderData = 0;
-        searched++;
         if (sniffing) {
           input.resetPeekPosition();
-          input.advancePeekPosition(peekedId3Bytes + searched);
+          input.advancePeekPosition(peekedId3Bytes + searchedBytes);
         } else {
           input.skipFully(1);
         }
       } else {
-        // The header is valid and matches the candidate header.
+        // The header matches the candidate header and/or is valid.
         validFrameCount++;
         if (validFrameCount == 1) {
           MpegAudioHeader.populateHeader(headerData, synchronizedHeader);
@@ -266,7 +245,7 @@ public final class Mp3Extractor implements Extractor {
     }
     // Prepare to read the synchronized frame.
     if (sniffing) {
-      input.skipFully(peekedId3Bytes + searched);
+      input.skipFully(peekedId3Bytes + searchedBytes);
     } else {
       input.resetPeekPosition();
     }

testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeExtractorInput.java

@@ -84,7 +84,7 @@ public final class FakeExtractorInput implements ExtractorInput {
    * @param position The position to set.
    */
   public void setPosition(int position) {
-    Assert.assertTrue(0 <= position && position < data.length);
+    Assert.assertTrue(0 <= position && position <= data.length);
     readPosition = position;
     peekPosition = position;
   }
@@ -203,7 +203,7 @@ public final class FakeExtractorInput implements ExtractorInput {
       peekPosition = readPosition;
       throw new SimulatedIOException("Simulated IO error at position: " + position);
     }
-    if (isEof()) {
+    if (length > 0 && position == data.length) {
       if (allowEndOfInput) {
         return false;
       }
@@ -217,6 +217,10 @@ public final class FakeExtractorInput implements ExtractorInput {
   }
 
   private int getReadLength(int requestedLength) {
+    if (readPosition == data.length) {
+      // If the requested length is non-zero, the end of the input will be read.
+      return requestedLength == 0 ? 0 : Integer.MAX_VALUE;
+    }
     int targetPosition = readPosition + requestedLength;
     if (simulatePartialReads && requestedLength > 1
         && !partiallySatisfiedTargetPositions.get(targetPosition)) {
@@ -226,10 +230,6 @@ public final class FakeExtractorInput implements ExtractorInput {
     return Math.min(requestedLength, data.length - readPosition);
   }
 
-  private boolean isEof() {
-    return readPosition == data.length;
-  }
-
   /**
    * Builder of {@link FakeExtractorInput} instances.
    */