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.text.webvtt;
  
  import com.google.android.exoplayer2.text.Cue;
  import com.google.android.exoplayer2.text.SimpleSubtitleDecoder;
  import com.google.android.exoplayer2.text.SubtitleDecoderException;
  import com.google.android.exoplayer2.util.ParsableByteArray;
  import com.google.android.exoplayer2.util.Util;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.List;
  
  /**
   * A {@link SimpleSubtitleDecoder} for Webvtt embedded in a Mp4 container file.
   */
  public final class Mp4WebvttDecoder extends SimpleSubtitleDecoder {
  
    private static final int BOX_HEADER_SIZE = 8;
  
    private static final int TYPE_payl = Util.getIntegerCodeForString("payl");
    private static final int TYPE_sttg = Util.getIntegerCodeForString("sttg");
    private static final int TYPE_vttc = Util.getIntegerCodeForString("vttc");
  
    private final ParsableByteArray sampleData;
    private final WebvttCue.Builder builder;
  
    public Mp4WebvttDecoder() {
      super("Mp4WebvttDecoder");
      sampleData = new ParsableByteArray();
      builder = new WebvttCue.Builder();
    }
  
    @Override
    protected Mp4WebvttSubtitle decode(byte[] bytes, int length, boolean reset)
        throws SubtitleDecoderException {
      // Webvtt in Mp4 samples have boxes inside of them, so we have to do a traditional box parsing:
      // first 4 bytes size and then 4 bytes type.
      sampleData.reset(bytes, length);
      List<Cue> resultingCueList = new ArrayList<>();
      while (sampleData.bytesLeft() > 0) {
        if (sampleData.bytesLeft() < BOX_HEADER_SIZE) {
          throw new SubtitleDecoderException("Incomplete Mp4Webvtt Top Level box header found.");
        }
        int boxSize = sampleData.readInt();
        int boxType = sampleData.readInt();
        if (boxType == TYPE_vttc) {
          resultingCueList.add(parseVttCueBox(sampleData, builder, boxSize - BOX_HEADER_SIZE));
        } else {
          // Peers of the VTTCueBox are still not supported and are skipped.
          sampleData.skipBytes(boxSize - BOX_HEADER_SIZE);
        }
      }
      return new Mp4WebvttSubtitle(resultingCueList);
    }
  
    private static Cue parseVttCueBox(ParsableByteArray sampleData, WebvttCue.Builder builder,
          int remainingCueBoxBytes) throws SubtitleDecoderException {
      builder.reset();
      while (remainingCueBoxBytes > 0) {
        if (remainingCueBoxBytes < BOX_HEADER_SIZE) {
          throw new SubtitleDecoderException("Incomplete vtt cue box header found.");
        }
        int boxSize = sampleData.readInt();
        int boxType = sampleData.readInt();
        remainingCueBoxBytes -= BOX_HEADER_SIZE;
        int payloadLength = boxSize - BOX_HEADER_SIZE;
        String boxPayload = new String(sampleData.data, sampleData.getPosition(), payloadLength);
        sampleData.skipBytes(payloadLength);
        remainingCueBoxBytes -= payloadLength;
        if (boxType == TYPE_sttg) {
          WebvttCueParser.parseCueSettingsList(boxPayload, builder);
        } else if (boxType == TYPE_payl) {
          WebvttCueParser.parseCueText(null, boxPayload.trim(), builder,
              Collections.<WebvttCssStyle>emptyList());
        } else {
          // Other VTTCueBox children are still not supported and are ignored.
        }
      }
      return builder.build();
    }
  
  }
  