content: /*
   * Copyright (C) 2016 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.extractor.mp3;
  
  import android.support.annotation.IntDef;
  import com.google.android.exoplayer2.C;
  import com.google.android.exoplayer2.Format;
  import com.google.android.exoplayer2.ParserException;
  import com.google.android.exoplayer2.extractor.Extractor;
  import com.google.android.exoplayer2.extractor.ExtractorInput;
  import com.google.android.exoplayer2.extractor.ExtractorOutput;
  import com.google.android.exoplayer2.extractor.ExtractorsFactory;
  import com.google.android.exoplayer2.extractor.GaplessInfoHolder;
  import com.google.android.exoplayer2.extractor.MpegAudioHeader;
  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.metadata.Metadata;
  import com.google.android.exoplayer2.metadata.id3.Id3Decoder;
  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.Retention;
  import java.lang.annotation.RetentionPolicy;
  
  /**
   * Extracts data from the MP3 container format.
   */
  public final class Mp3Extractor implements Extractor {
  
    /**
     * Factory for {@link Mp3Extractor} instances.
     */
    public static final ExtractorsFactory FACTORY = new ExtractorsFactory() {
  
      @Override
      public Extractor[] createExtractors() {
        return new Extractor[] {new Mp3Extractor()};
      }
  
    };
  
    /**
     * Flags controlling the behavior of the extractor.
     */
    @Retention(RetentionPolicy.SOURCE)
    @IntDef(flag = true, value = {FLAG_ENABLE_CONSTANT_BITRATE_SEEKING, FLAG_DISABLE_ID3_METADATA})
    public @interface Flags {}
    /**
     * Flag to force enable seeking using a constant bitrate assumption in cases where seeking would
     * otherwise not be possible.
     */
    public static final int FLAG_ENABLE_CONSTANT_BITRATE_SEEKING = 1;
    /**
     * Flag to disable parsing of ID3 metadata. Can be set to save memory if ID3 metadata is not
     * required.
     */
    public static final int FLAG_DISABLE_ID3_METADATA = 2;
  
    /**
     * The maximum number of bytes to search when synchronizing, before giving up.
     */
    private static final int MAX_SYNC_BYTES = 128 * 1024;
    /**
     * The maximum number of bytes to peek when sniffing, excluding the ID3 header, before giving up.
     */
    private static final int MAX_SNIFF_BYTES = 16 * 1024;
    /**
     * Maximum length of data read into {@link #scratch}.
     */
    private static final int SCRATCH_LENGTH = 10;
  
    /**
     * Mask that includes the audio header values that must match between frames.
     */
    private static final int MPEG_AUDIO_HEADER_MASK = 0xFFFE0C00;
  
    private static final int SEEK_HEADER_XING = Util.getIntegerCodeForString("Xing");
    private static final int SEEK_HEADER_INFO = Util.getIntegerCodeForString("Info");
    private static final int SEEK_HEADER_VBRI = Util.getIntegerCodeForString("VBRI");
    private static final int SEEK_HEADER_UNSET = 0;
  
    @Flags private final int flags;
    private final long forcedFirstSampleTimestampUs;
    private final ParsableByteArray scratch;
    private final MpegAudioHeader synchronizedHeader;
    private final GaplessInfoHolder gaplessInfoHolder;
  
    // Extractor outputs.
    private ExtractorOutput extractorOutput;
    private TrackOutput trackOutput;
  
    private int synchronizedHeaderData;
  
    private Metadata metadata;
    private Seeker seeker;
    private long basisTimeUs;
    private long samplesRead;
    private int sampleBytesRemaining;
  
    public Mp3Extractor() {
      this(0);
    }
  
    /**
     * @param flags Flags that control the extractor's behavior.
     */
    public Mp3Extractor(@Flags int flags) {
      this(flags, C.TIME_UNSET);
    }
  
    /**
     * @param flags Flags that control the extractor's behavior.
     * @param forcedFirstSampleTimestampUs A timestamp to force for the first sample, or
     *     {@link C#TIME_UNSET} if forcing is not required.
     */
    public Mp3Extractor(@Flags int flags, long forcedFirstSampleTimestampUs) {
      this.flags = flags;
      this.forcedFirstSampleTimestampUs = forcedFirstSampleTimestampUs;
      scratch = new ParsableByteArray(SCRATCH_LENGTH);
      synchronizedHeader = new MpegAudioHeader();
      gaplessInfoHolder = new GaplessInfoHolder();
      basisTimeUs = C.TIME_UNSET;
    }
  
    // Extractor implementation.
  
    @Override
    public boolean sniff(ExtractorInput input) throws IOException, InterruptedException {
      return synchronize(input, true);
    }
  
    @Override
    public void init(ExtractorOutput output) {
      extractorOutput = output;
      trackOutput = extractorOutput.track(0, C.TRACK_TYPE_AUDIO);
      extractorOutput.endTracks();
    }
  
    @Override
    public void seek(long position, long timeUs) {
      synchronizedHeaderData = 0;
      basisTimeUs = C.TIME_UNSET;
      samplesRead = 0;
      sampleBytesRemaining = 0;
    }
  
    @Override
    public void release() {
      // Do nothing
    }
  
    @Override
    public int read(ExtractorInput input, PositionHolder seekPosition)
        throws IOException, InterruptedException {
      if (synchronizedHeaderData == 0) {
        try {
          synchronize(input, false);
        } catch (EOFException e) {
          return RESULT_END_OF_INPUT;
        }
      }
      if (seeker == null) {
        seeker = maybeReadSeekFrame(input);
        if (seeker == null
            || (!seeker.isSeekable() && (flags & FLAG_ENABLE_CONSTANT_BITRATE_SEEKING) != 0)) {
          seeker = getConstantBitrateSeeker(input);
        }
        extractorOutput.seekMap(seeker);
        trackOutput.format(Format.createAudioSampleFormat(null, synchronizedHeader.mimeType, null,
            Format.NO_VALUE, MpegAudioHeader.MAX_FRAME_SIZE_BYTES, synchronizedHeader.channels,
            synchronizedHeader.sampleRate, Format.NO_VALUE, gaplessInfoHolder.encoderDelay,
            gaplessInfoHolder.encoderPadding, null, null, 0, null,
            (flags & FLAG_DISABLE_ID3_METADATA) != 0 ? null : metadata));
      }
      return readSample(input);
    }
  
    // Internal methods.
  
    private int readSample(ExtractorInput extractorInput) throws IOException, InterruptedException {
      if (sampleBytesRemaining == 0) {
        extractorInput.resetPeekPosition();
        if (!extractorInput.peekFully(scratch.data, 0, 4, true)) {
          return RESULT_END_OF_INPUT;
        }
        scratch.setPosition(0);
        int sampleHeaderData = scratch.readInt();
        if (!headersMatch(sampleHeaderData, synchronizedHeaderData)
            || 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) {
            long embeddedFirstSampleTimestampUs = seeker.getTimeUs(0);
            basisTimeUs += forcedFirstSampleTimestampUs - embeddedFirstSampleTimestampUs;
          }
        }
        sampleBytesRemaining = synchronizedHeader.frameSize;
      }
      int bytesAppended = trackOutput.sampleData(extractorInput, sampleBytesRemaining, true);
      if (bytesAppended == C.RESULT_END_OF_INPUT) {
        return RESULT_END_OF_INPUT;
      }
      sampleBytesRemaining -= bytesAppended;
      if (sampleBytesRemaining > 0) {
        return RESULT_CONTINUE;
      }
      long timeUs = basisTimeUs + (samplesRead * C.MICROS_PER_SECOND / synchronizedHeader.sampleRate);
      trackOutput.sampleMetadata(timeUs, C.BUFFER_FLAG_KEY_FRAME, synchronizedHeader.frameSize, 0,
          null);
      samplesRead += synchronizedHeader.samplesPerFrame;
      sampleBytesRemaining = 0;
      return RESULT_CONTINUE;
    }
  
    private boolean synchronize(ExtractorInput input, boolean sniffing)
        throws IOException, InterruptedException {
      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) {
        peekId3Data(input);
        peekedId3Bytes = (int) input.getPeekPosition();
        if (!sniffing) {
          input.skipFully(peekedId3Bytes);
        }
      }
      while (true) {
        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();
        int frameSize;
        if ((candidateSynchronizedHeaderData != 0
            && !headersMatch(headerData, candidateSynchronizedHeaderData))
            || (frameSize = MpegAudioHeader.getFrameSize(headerData)) == C.LENGTH_UNSET) {
          // 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;
          if (sniffing) {
            input.resetPeekPosition();
            input.advancePeekPosition(peekedId3Bytes + searchedBytes);
          } else {
            input.skipFully(1);
          }
        } else {
          // The header matches the candidate header and/or is valid.
          validFrameCount++;
          if (validFrameCount == 1) {
            MpegAudioHeader.populateHeader(headerData, synchronizedHeader);
            candidateSynchronizedHeaderData = headerData;
          } else if (validFrameCount == 4) {
            break;
          }
          input.advancePeekPosition(frameSize - 4);
        }
      }
      // Prepare to read the synchronized frame.
      if (sniffing) {
        input.skipFully(peekedId3Bytes + searchedBytes);
      } else {
        input.resetPeekPosition();
      }
      synchronizedHeaderData = candidateSynchronizedHeaderData;
      return true;
    }
  
    /**
     * Peeks ID3 data from the input, including gapless playback information.
     *
     * @param input The {@link ExtractorInput} from which data should be peeked.
     * @throws IOException If an error occurred peeking from the input.
     * @throws InterruptedException If the thread was interrupted.
     */
    private void peekId3Data(ExtractorInput input) throws IOException, InterruptedException {
      int peekedId3Bytes = 0;
      while (true) {
        input.peekFully(scratch.data, 0, Id3Decoder.ID3_HEADER_LENGTH);
        scratch.setPosition(0);
        if (scratch.readUnsignedInt24() != Id3Decoder.ID3_TAG) {
          // Not an ID3 tag.
          break;
        }
        scratch.skipBytes(3); // Skip major version, minor version and flags.
        int framesLength = scratch.readSynchSafeInt();
        int tagLength = Id3Decoder.ID3_HEADER_LENGTH + framesLength;
  
        if (metadata == null) {
          byte[] id3Data = new byte[tagLength];
          System.arraycopy(scratch.data, 0, id3Data, 0, Id3Decoder.ID3_HEADER_LENGTH);
          input.peekFully(id3Data, Id3Decoder.ID3_HEADER_LENGTH, framesLength);
          // We need to parse enough ID3 metadata to retrieve any gapless playback information even
          // if ID3 metadata parsing is disabled.
          Id3Decoder.FramePredicate id3FramePredicate = (flags & FLAG_DISABLE_ID3_METADATA) != 0
              ? GaplessInfoHolder.GAPLESS_INFO_ID3_FRAME_PREDICATE : null;
          metadata = new Id3Decoder(id3FramePredicate).decode(id3Data, tagLength);
          if (metadata != null) {
            gaplessInfoHolder.setFromMetadata(metadata);
          }
        } else {
          input.advancePeekPosition(framesLength);
        }
  
        peekedId3Bytes += tagLength;
      }
  
      input.resetPeekPosition();
      input.advancePeekPosition(peekedId3Bytes);
    }
  
    /**
     * Consumes the next frame from the {@code input} if it contains VBRI or Xing seeking metadata,
     * returning a {@link Seeker} if the metadata was present and valid, or {@code null} otherwise.
     * After this method returns, the input position is the start of the first frame of audio.
     *
     * @param input The {@link ExtractorInput} from which to read.
     * @return A {@link Seeker} if seeking metadata was present and valid, or {@code null} otherwise.
     * @throws IOException Thrown if there was an error reading from the stream. Not expected if the
     *     next two frames were already peeked during synchronization.
     * @throws InterruptedException Thrown if reading from the stream was interrupted. Not expected if
     *     the next two frames were already peeked during synchronization.
     */
    private Seeker maybeReadSeekFrame(ExtractorInput input) throws IOException, InterruptedException {
      ParsableByteArray frame = new ParsableByteArray(synchronizedHeader.frameSize);
      input.peekFully(frame.data, 0, synchronizedHeader.frameSize);
      int xingBase = (synchronizedHeader.version & 1) != 0
          ? (synchronizedHeader.channels != 1 ? 36 : 21) // MPEG 1
          : (synchronizedHeader.channels != 1 ? 21 : 13); // MPEG 2 or 2.5
      int seekHeader = getSeekFrameHeader(frame, xingBase);
      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()) {
          // If there is a Xing header, read gapless playback metadata at a fixed offset.
          input.resetPeekPosition();
          input.advancePeekPosition(xingBase + 141);
          input.peekFully(scratch.data, 0, 3);
          scratch.setPosition(0);
          gaplessInfoHolder.setFromXingHeaderValue(scratch.readUnsignedInt24());
        }
        input.skipFully(synchronizedHeader.frameSize);
        if (seeker != null && !seeker.isSeekable() && seekHeader == SEEK_HEADER_INFO) {
          // Fall back to constant bitrate seeking for Info headers missing a table of contents.
          return getConstantBitrateSeeker(input);
        }
      } else if (seekHeader == SEEK_HEADER_VBRI) {
        seeker = VbriSeeker.create(input.getLength(), input.getPosition(), synchronizedHeader, frame);
        input.skipFully(synchronizedHeader.frameSize);
      } else { // seekerHeader == SEEK_HEADER_UNSET
        // This frame doesn't contain seeking information, so reset the peek position.
        seeker = null;
        input.resetPeekPosition();
      }
      return seeker;
    }
  
    /**
     * Peeks the next frame and returns a {@link ConstantBitrateSeeker} based on its bitrate.
     */
    private Seeker getConstantBitrateSeeker(ExtractorInput input)
        throws IOException, InterruptedException {
      input.peekFully(scratch.data, 0, 4);
      scratch.setPosition(0);
      MpegAudioHeader.populateHeader(scratch.readInt(), synchronizedHeader);
      return new ConstantBitrateSeeker(input.getLength(), input.getPosition(), synchronizedHeader);
    }
  
    /**
     * Returns whether the headers match in those bits masked by {@link #MPEG_AUDIO_HEADER_MASK}.
     */
    private static boolean headersMatch(int headerA, long headerB) {
      return (headerA & MPEG_AUDIO_HEADER_MASK) == (headerB & MPEG_AUDIO_HEADER_MASK);
    }
  
    /**
     * Returns {@link #SEEK_HEADER_XING}, {@link #SEEK_HEADER_INFO} or {@link #SEEK_HEADER_VBRI} if
     * the provided {@code frame} may have seeking metadata, or {@link #SEEK_HEADER_UNSET} otherwise.
     * If seeking metadata is present, {@code frame}'s position is advanced past the header.
     */
    private static int getSeekFrameHeader(ParsableByteArray frame, int xingBase) {
      if (frame.limit() >= xingBase + 4) {
        frame.setPosition(xingBase);
        int headerData = frame.readInt();
        if (headerData == SEEK_HEADER_XING || headerData == SEEK_HEADER_INFO) {
          return headerData;
        }
      }
      if (frame.limit() >= 40) {
        frame.setPosition(36); // MPEG audio header (4 bytes) + 32 bytes.
        if (frame.readInt() == SEEK_HEADER_VBRI) {
          return SEEK_HEADER_VBRI;
        }
      }
      return SEEK_HEADER_UNSET;
    }
  
    /**
     * {@link SeekMap} that also allows mapping from position (byte offset) back to time, which can be
     * used to work out the new sample basis timestamp after seeking and resynchronization.
     */
    /* package */ interface Seeker extends SeekMap {
  
      /**
       * Maps a position (byte offset) to a corresponding sample timestamp.
       *
       * @param position A seek position (byte offset) relative to the start of the stream.
       * @return The corresponding timestamp of the next sample to be read, in microseconds.
       */
      long getTimeUs(long position);
  
    }
  
  }
  