Java Code Examples for com.google.android.exoplayer2.util.ParsableByteArray#readString()

/**
 * Reads a vorbis comment header.
 *
 * @see <a href="https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-640004.2.3">
 *     Vorbis spec/Comment header</a>
 * @param headerData a {@link ParsableByteArray} wrapping the header data.
 * @return a {@link CommentHeader} with all the comments.
 * @throws ParserException thrown if invalid capture pattern is detected.
 */
public static CommentHeader readVorbisCommentHeader(ParsableByteArray headerData)
    throws ParserException {

  verifyVorbisHeaderCapturePattern(0x03, headerData, false);
  int length = 7;

  int len = (int) headerData.readLittleEndianUnsignedInt();
  length += 4;
  String vendor = headerData.readString(len);
  length += vendor.length();

  long commentListLen = headerData.readLittleEndianUnsignedInt();
  String[] comments = new String[(int) commentListLen];
  length += 4;
  for (int i = 0; i < commentListLen; i++) {
    len = (int) headerData.readLittleEndianUnsignedInt();
    length += 4;
    comments[i] = headerData.readString(len);
    length += comments[i].length();
  }
  if ((headerData.readUnsignedByte() & 0x01) == 0) {
    throw new ParserException("framing bit expected to be set");
  }
  length += 1;
  return new CommentHeader(vendor, comments, length);
}
 

private static String readSubtitleText(ParsableByteArray parsableByteArray)
    throws SubtitleDecoderException {
  assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
  int textLength = parsableByteArray.readUnsignedShort();
  if (textLength == 0) {
    return "";
  }
  if (parsableByteArray.bytesLeft() >= SIZE_BOM_UTF16) {
    char firstChar = parsableByteArray.peekChar();
    if (firstChar == BOM_UTF16_BE || firstChar == BOM_UTF16_LE) {
      return parsableByteArray.readString(textLength, Charset.forName(C.UTF16_NAME));
    }
  }
  return parsableByteArray.readString(textLength, Charset.forName(C.UTF8_NAME));
}
 

/**
 * If the LA_URL tag is missing, injects a mock LA_URL value to avoid causing the CDM to throw
 * when creating the key request. The LA_URL attribute is optional but some Android PlayReady
 * implementations are known to require it. Does nothing it the provided {@code data} already
 * contains an LA_URL value.
 */
private static byte[] addLaUrlAttributeIfMissing(byte[] data) {
  ParsableByteArray byteArray = new ParsableByteArray(data);
  // See https://docs.microsoft.com/en-us/playready/specifications/specifications for more
  // information about the init data format.
  int length = byteArray.readLittleEndianInt();
  int objectRecordCount = byteArray.readLittleEndianShort();
  int recordType = byteArray.readLittleEndianShort();
  if (objectRecordCount != 1 || recordType != 1) {
    Log.i(TAG, "Unexpected record count or type. Skipping LA_URL workaround.");
    return data;
  }
  int recordLength = byteArray.readLittleEndianShort();
  String xml = byteArray.readString(recordLength, Charset.forName(C.UTF16LE_NAME));
  if (xml.contains("<LA_URL>")) {
    // LA_URL already present. Do nothing.
    return data;
  }
  // This PlayReady object record does not include an LA_URL. We add a mock value for it.
  int endOfDataTagIndex = xml.indexOf("</DATA>");
  if (endOfDataTagIndex == -1) {
    Log.w(TAG, "Could not find the </DATA> tag. Skipping LA_URL workaround.");
  }
  String xmlWithMockLaUrl =
      xml.substring(/* beginIndex= */ 0, /* endIndex= */ endOfDataTagIndex)
          + MOCK_LA_URL
          + xml.substring(/* beginIndex= */ endOfDataTagIndex);
  int extraBytes = MOCK_LA_URL.length() * UTF_16_BYTES_PER_CHARACTER;
  ByteBuffer newData = ByteBuffer.allocate(length + extraBytes);
  newData.order(ByteOrder.LITTLE_ENDIAN);
  newData.putInt(length + extraBytes);
  newData.putShort((short) objectRecordCount);
  newData.putShort((short) recordType);
  newData.putShort((short) (xmlWithMockLaUrl.length() * UTF_16_BYTES_PER_CHARACTER));
  newData.put(xmlWithMockLaUrl.getBytes(Charset.forName(C.UTF16LE_NAME)));
  return newData.array();
}
 

/**
 * Returns a string containing the selector. The input is expected to have the form
 * {@code ::cue(tag#id.class1.class2[voice="someone"]}, where every element is optional.
 *
 * @param input From which the selector is obtained.
 * @return A string containing the target, empty string if the selector is universal
 *     (targets all cues) or null if an error was encountered.
 */
private static String parseSelector(ParsableByteArray input, StringBuilder stringBuilder) {
  skipWhitespaceAndComments(input);
  if (input.bytesLeft() < 5) {
    return null;
  }
  String cueSelector = input.readString(5);
  if (!"::cue".equals(cueSelector)) {
    return null;
  }
  int position = input.getPosition();
  String token = parseNextToken(input, stringBuilder);
  if (token == null) {
    return null;
  }
  if (BLOCK_START.equals(token)) {
    input.setPosition(position);
    return "";
  }
  String target = null;
  if ("(".equals(token)) {
    target = readCueTarget(input);
  }
  token = parseNextToken(input, stringBuilder);
  if (!")".equals(token) || token == null) {
    return null;
  }
  return target;
}
 

/**
 * Returns a string containing the selector. The input is expected to have the form
 * {@code ::cue(tag#id.class1.class2[voice="someone"]}, where every element is optional.
 *
 * @param input From which the selector is obtained.
 * @return A string containing the target, empty string if the selector is universal
 *     (targets all cues) or null if an error was encountered.
 */
private static String parseSelector(ParsableByteArray input, StringBuilder stringBuilder) {
  skipWhitespaceAndComments(input);
  if (input.bytesLeft() < 5) {
    return null;
  }
  String cueSelector = input.readString(5);
  if (!"::cue".equals(cueSelector)) {
    return null;
  }
  int position = input.getPosition();
  String token = parseNextToken(input, stringBuilder);
  if (token == null) {
    return null;
  }
  if (BLOCK_START.equals(token)) {
    input.setPosition(position);
    return "";
  }
  String target = null;
  if ("(".equals(token)) {
    target = readCueTarget(input);
  }
  token = parseNextToken(input, stringBuilder);
  if (!")".equals(token) || token == null) {
    return null;
  }
  return target;
}
 

/**
 * Returns a string containing the selector. The input is expected to have the form
 * {@code ::cue(tag#id.class1.class2[voice="someone"]}, where every element is optional.
 *
 * @param input From which the selector is obtained.
 * @return A string containing the target, empty string if the selector is universal
 *     (targets all cues) or null if an error was encountered.
 */
private static String parseSelector(ParsableByteArray input, StringBuilder stringBuilder) {
  skipWhitespaceAndComments(input);
  if (input.bytesLeft() < 5) {
    return null;
  }
  String cueSelector = input.readString(5);
  if (!"::cue".equals(cueSelector)) {
    return null;
  }
  int position = input.getPosition();
  String token = parseNextToken(input, stringBuilder);
  if (token == null) {
    return null;
  }
  if (BLOCK_START.equals(token)) {
    input.setPosition(position);
    return "";
  }
  String target = null;
  if ("(".equals(token)) {
    target = readCueTarget(input);
  }
  token = parseNextToken(input, stringBuilder);
  if (!")".equals(token) || token == null) {
    return null;
  }
  return target;
}
 

private static String readSubtitleText(ParsableByteArray parsableByteArray)
    throws SubtitleDecoderException {
  assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
  int textLength = parsableByteArray.readUnsignedShort();
  if (textLength == 0) {
    return "";
  }
  if (parsableByteArray.bytesLeft() >= SIZE_BOM_UTF16) {
    char firstChar = parsableByteArray.peekChar();
    if (firstChar == BOM_UTF16_BE || firstChar == BOM_UTF16_LE) {
      return parsableByteArray.readString(textLength, Charset.forName(C.UTF16_NAME));
    }
  }
  return parsableByteArray.readString(textLength, Charset.forName(C.UTF8_NAME));
}
 

static Pair<Integer, TrackEncryptionBox> parseCommonEncryptionSinfFromParent(
    ParsableByteArray parent, int position, int size) {
  int childPosition = position + Atom.HEADER_SIZE;
  int schemeInformationBoxPosition = C.POSITION_UNSET;
  int schemeInformationBoxSize = 0;
  String schemeType = null;
  Integer dataFormat = null;
  while (childPosition - position < size) {
    parent.setPosition(childPosition);
    int childAtomSize = parent.readInt();
    int childAtomType = parent.readInt();
    if (childAtomType == Atom.TYPE_frma) {
      dataFormat = parent.readInt();
    } else if (childAtomType == Atom.TYPE_schm) {
      parent.skipBytes(4);
      // Common encryption scheme_type values are defined in ISO/IEC 23001-7:2016, section 4.1.
      schemeType = parent.readString(4);
    } else if (childAtomType == Atom.TYPE_schi) {
      schemeInformationBoxPosition = childPosition;
      schemeInformationBoxSize = childAtomSize;
    }
    childPosition += childAtomSize;
  }

  if (C.CENC_TYPE_cenc.equals(schemeType) || C.CENC_TYPE_cbc1.equals(schemeType)
      || C.CENC_TYPE_cens.equals(schemeType) || C.CENC_TYPE_cbcs.equals(schemeType)) {
    Assertions.checkArgument(dataFormat != null, "frma atom is mandatory");
    Assertions.checkArgument(schemeInformationBoxPosition != C.POSITION_UNSET,
        "schi atom is mandatory");
    TrackEncryptionBox encryptionBox = parseSchiFromParent(parent, schemeInformationBoxPosition,
        schemeInformationBoxSize, schemeType);
    Assertions.checkArgument(encryptionBox != null, "tenc atom is mandatory");
    return Pair.create(dataFormat, encryptionBox);
  } else {
    return null;
  }
}
 

/**
 * Reads a vorbis comment header.
 *
 * @see <a href="https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-640004.2.3">
 *     Vorbis spec/Comment header</a>
 * @param headerData a {@link ParsableByteArray} wrapping the header data.
 * @return a {@link VorbisUtil.CommentHeader} with all the comments.
 * @throws ParserException thrown if invalid capture pattern is detected.
 */
public static CommentHeader readVorbisCommentHeader(ParsableByteArray headerData)
    throws ParserException {

  verifyVorbisHeaderCapturePattern(0x03, headerData, false);
  int length = 7;

  int len = (int) headerData.readLittleEndianUnsignedInt();
  length += 4;
  String vendor = headerData.readString(len);
  length += vendor.length();

  long commentListLen = headerData.readLittleEndianUnsignedInt();
  String[] comments = new String[(int) commentListLen];
  length += 4;
  for (int i = 0; i < commentListLen; i++) {
    len = (int) headerData.readLittleEndianUnsignedInt();
    length += 4;
    comments[i] = headerData.readString(len);
    length += comments[i].length();
  }
  if ((headerData.readUnsignedByte() & 0x01) == 0) {
    throw new ParserException("framing bit expected to be set");
  }
  length += 1;
  return new CommentHeader(vendor, comments, length);
}
 

static Pair<Integer, TrackEncryptionBox> parseCommonEncryptionSinfFromParent(
    ParsableByteArray parent, int position, int size) {
  int childPosition = position + Atom.HEADER_SIZE;
  int schemeInformationBoxPosition = C.POSITION_UNSET;
  int schemeInformationBoxSize = 0;
  String schemeType = null;
  Integer dataFormat = null;
  while (childPosition - position < size) {
    parent.setPosition(childPosition);
    int childAtomSize = parent.readInt();
    int childAtomType = parent.readInt();
    if (childAtomType == Atom.TYPE_frma) {
      dataFormat = parent.readInt();
    } else if (childAtomType == Atom.TYPE_schm) {
      parent.skipBytes(4);
      // Common encryption scheme_type values are defined in ISO/IEC 23001-7:2016, section 4.1.
      schemeType = parent.readString(4);
    } else if (childAtomType == Atom.TYPE_schi) {
      schemeInformationBoxPosition = childPosition;
      schemeInformationBoxSize = childAtomSize;
    }
    childPosition += childAtomSize;
  }

  if (C.CENC_TYPE_cenc.equals(schemeType) || C.CENC_TYPE_cbc1.equals(schemeType)
      || C.CENC_TYPE_cens.equals(schemeType) || C.CENC_TYPE_cbcs.equals(schemeType)) {
    Assertions.checkArgument(dataFormat != null, "frma atom is mandatory");
    Assertions.checkArgument(schemeInformationBoxPosition != C.POSITION_UNSET,
        "schi atom is mandatory");
    TrackEncryptionBox encryptionBox = parseSchiFromParent(parent, schemeInformationBoxPosition,
        schemeInformationBoxSize, schemeType);
    Assertions.checkArgument(encryptionBox != null, "tenc atom is mandatory");
    return Pair.create(dataFormat, encryptionBox);
  } else {
    return null;
  }
}
 

private static String readSubtitleText(ParsableByteArray parsableByteArray)
    throws SubtitleDecoderException {
  assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
  int textLength = parsableByteArray.readUnsignedShort();
  if (textLength == 0) {
    return "";
  }
  if (parsableByteArray.bytesLeft() >= SIZE_BOM_UTF16) {
    char firstChar = parsableByteArray.peekChar();
    if (firstChar == BOM_UTF16_BE || firstChar == BOM_UTF16_LE) {
      return parsableByteArray.readString(textLength, Charset.forName(C.UTF16_NAME));
    }
  }
  return parsableByteArray.readString(textLength, Charset.forName(C.UTF8_NAME));
}
 

static Pair<Integer, TrackEncryptionBox> parseCommonEncryptionSinfFromParent(
    ParsableByteArray parent, int position, int size) {
  int childPosition = position + Atom.HEADER_SIZE;
  int schemeInformationBoxPosition = C.POSITION_UNSET;
  int schemeInformationBoxSize = 0;
  String schemeType = null;
  Integer dataFormat = null;
  while (childPosition - position < size) {
    parent.setPosition(childPosition);
    int childAtomSize = parent.readInt();
    int childAtomType = parent.readInt();
    if (childAtomType == Atom.TYPE_frma) {
      dataFormat = parent.readInt();
    } else if (childAtomType == Atom.TYPE_schm) {
      parent.skipBytes(4);
      // Common encryption scheme_type values are defined in ISO/IEC 23001-7:2016, section 4.1.
      schemeType = parent.readString(4);
    } else if (childAtomType == Atom.TYPE_schi) {
      schemeInformationBoxPosition = childPosition;
      schemeInformationBoxSize = childAtomSize;
    }
    childPosition += childAtomSize;
  }

  if (C.CENC_TYPE_cenc.equals(schemeType) || C.CENC_TYPE_cbc1.equals(schemeType)
      || C.CENC_TYPE_cens.equals(schemeType) || C.CENC_TYPE_cbcs.equals(schemeType)) {
    Assertions.checkArgument(dataFormat != null, "frma atom is mandatory");
    Assertions.checkArgument(schemeInformationBoxPosition != C.POSITION_UNSET,
        "schi atom is mandatory");
    TrackEncryptionBox encryptionBox = parseSchiFromParent(parent, schemeInformationBoxPosition,
        schemeInformationBoxSize, schemeType);
    Assertions.checkArgument(encryptionBox != null, "tenc atom is mandatory");
    return Pair.create(dataFormat, encryptionBox);
  } else {
    return null;
  }
}
 

/**
 * Reads a vorbis comment header.
 *
 * @see <a href="https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-640004.2.3">
 *     Vorbis spec/Comment header</a>
 * @param headerData a {@link ParsableByteArray} wrapping the header data.
 * @return a {@link VorbisUtil.CommentHeader} with all the comments.
 * @throws ParserException thrown if invalid capture pattern is detected.
 */
public static CommentHeader readVorbisCommentHeader(ParsableByteArray headerData)
    throws ParserException {

  verifyVorbisHeaderCapturePattern(0x03, headerData, false);
  int length = 7;

  int len = (int) headerData.readLittleEndianUnsignedInt();
  length += 4;
  String vendor = headerData.readString(len);
  length += vendor.length();

  long commentListLen = headerData.readLittleEndianUnsignedInt();
  String[] comments = new String[(int) commentListLen];
  length += 4;
  for (int i = 0; i < commentListLen; i++) {
    len = (int) headerData.readLittleEndianUnsignedInt();
    length += 4;
    comments[i] = headerData.readString(len);
    length += comments[i].length();
  }
  if ((headerData.readUnsignedByte() & 0x01) == 0) {
    throw new ParserException("framing bit expected to be set");
  }
  length += 1;
  return new CommentHeader(vendor, comments, length);
}
 

/**
 * If the LA_URL tag is missing, injects a mock LA_URL value to avoid causing the CDM to throw
 * when creating the key request. The LA_URL attribute is optional but some Android PlayReady
 * implementations are known to require it. Does nothing it the provided {@code data} already
 * contains an LA_URL value.
 */
private static byte[] addLaUrlAttributeIfMissing(byte[] data) {
  ParsableByteArray byteArray = new ParsableByteArray(data);
  // See https://docs.microsoft.com/en-us/playready/specifications/specifications for more
  // information about the init data format.
  int length = byteArray.readLittleEndianInt();
  int objectRecordCount = byteArray.readLittleEndianShort();
  int recordType = byteArray.readLittleEndianShort();
  if (objectRecordCount != 1 || recordType != 1) {
    Log.i(TAG, "Unexpected record count or type. Skipping LA_URL workaround.");
    return data;
  }
  int recordLength = byteArray.readLittleEndianShort();
  String xml = byteArray.readString(recordLength, Charset.forName(C.UTF16LE_NAME));
  if (xml.contains("<LA_URL>")) {
    // LA_URL already present. Do nothing.
    return data;
  }
  // This PlayReady object record does not include an LA_URL. We add a mock value for it.
  int endOfDataTagIndex = xml.indexOf("</DATA>");
  if (endOfDataTagIndex == -1) {
    Log.w(TAG, "Could not find the </DATA> tag. Skipping LA_URL workaround.");
  }
  String xmlWithMockLaUrl =
      xml.substring(/* beginIndex= */ 0, /* endIndex= */ endOfDataTagIndex)
          + MOCK_LA_URL
          + xml.substring(/* beginIndex= */ endOfDataTagIndex);
  int extraBytes = MOCK_LA_URL.length() * UTF_16_BYTES_PER_CHARACTER;
  ByteBuffer newData = ByteBuffer.allocate(length + extraBytes);
  newData.order(ByteOrder.LITTLE_ENDIAN);
  newData.putInt(length + extraBytes);
  newData.putShort((short) objectRecordCount);
  newData.putShort((short) recordType);
  newData.putShort((short) (xmlWithMockLaUrl.length() * UTF_16_BYTES_PER_CHARACTER));
  newData.put(xmlWithMockLaUrl.getBytes(Charset.forName(C.UTF16LE_NAME)));
  return newData.array();
}
 

private static String readSubtitleText(ParsableByteArray parsableByteArray)
    throws SubtitleDecoderException {
  assertTrue(parsableByteArray.bytesLeft() >= SIZE_SHORT);
  int textLength = parsableByteArray.readUnsignedShort();
  if (textLength == 0) {
    return "";
  }
  if (parsableByteArray.bytesLeft() >= SIZE_BOM_UTF16) {
    char firstChar = parsableByteArray.peekChar();
    if (firstChar == BOM_UTF16_BE || firstChar == BOM_UTF16_LE) {
      return parsableByteArray.readString(textLength, Charset.forName(C.UTF16_NAME));
    }
  }
  return parsableByteArray.readString(textLength, Charset.forName(C.UTF8_NAME));
}
 

/**
 * Returns a string containing the selector. The input is expected to have the form
 * {@code ::cue(tag#id.class1.class2[voice="someone"]}, where every element is optional.
 *
 * @param input From which the selector is obtained.
 * @return A string containing the target, empty string if the selector is universal
 *     (targets all cues) or null if an error was encountered.
 */
private static String parseSelector(ParsableByteArray input, StringBuilder stringBuilder) {
  skipWhitespaceAndComments(input);
  if (input.bytesLeft() < 5) {
    return null;
  }
  String cueSelector = input.readString(5);
  if (!"::cue".equals(cueSelector)) {
    return null;
  }
  int position = input.getPosition();
  String token = parseNextToken(input, stringBuilder);
  if (token == null) {
    return null;
  }
  if (RULE_START.equals(token)) {
    input.setPosition(position);
    return "";
  }
  String target = null;
  if ("(".equals(token)) {
    target = readCueTarget(input);
  }
  token = parseNextToken(input, stringBuilder);
  if (!")".equals(token) || token == null) {
    return null;
  }
  return target;
}
 

/**
 * Reads a vorbis comment header.
 *
 * @see <a href="https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-640004.2.3">
 *     Vorbis spec/Comment header</a>
 * @param headerData a {@link ParsableByteArray} wrapping the header data.
 * @return a {@link VorbisUtil.CommentHeader} with all the comments.
 * @throws ParserException thrown if invalid capture pattern is detected.
 */
public static CommentHeader readVorbisCommentHeader(ParsableByteArray headerData)
    throws ParserException {

  verifyVorbisHeaderCapturePattern(0x03, headerData, false);
  int length = 7;

  int len = (int) headerData.readLittleEndianUnsignedInt();
  length += 4;
  String vendor = headerData.readString(len);
  length += vendor.length();

  long commentListLen = headerData.readLittleEndianUnsignedInt();
  String[] comments = new String[(int) commentListLen];
  length += 4;
  for (int i = 0; i < commentListLen; i++) {
    len = (int) headerData.readLittleEndianUnsignedInt();
    length += 4;
    comments[i] = headerData.readString(len);
    length += comments[i].length();
  }
  if ((headerData.readUnsignedByte() & 0x01) == 0) {
    throw new ParserException("framing bit expected to be set");
  }
  length += 1;
  return new CommentHeader(vendor, comments, length);
}
 

/**
 * Parses a metadata meta atom if it contains metadata with handler 'mdta'.
 *
 * @param meta The metadata atom to decode.
 * @return Parsed metadata, or null.
 */
@Nullable
public static Metadata parseMdtaFromMeta(Atom.ContainerAtom meta) {
  Atom.LeafAtom hdlrAtom = meta.getLeafAtomOfType(Atom.TYPE_hdlr);
  Atom.LeafAtom keysAtom = meta.getLeafAtomOfType(Atom.TYPE_keys);
  Atom.LeafAtom ilstAtom = meta.getLeafAtomOfType(Atom.TYPE_ilst);
  if (hdlrAtom == null
      || keysAtom == null
      || ilstAtom == null
      || AtomParsers.parseHdlr(hdlrAtom.data) != TYPE_mdta) {
    // There isn't enough information to parse the metadata, or the handler type is unexpected.
    return null;
  }

  // Parse metadata keys.
  ParsableByteArray keys = keysAtom.data;
  keys.setPosition(Atom.FULL_HEADER_SIZE);
  int entryCount = keys.readInt();
  String[] keyNames = new String[entryCount];
  for (int i = 0; i < entryCount; i++) {
    int entrySize = keys.readInt();
    keys.skipBytes(4); // keyNamespace
    int keySize = entrySize - 8;
    keyNames[i] = keys.readString(keySize);
  }

  // Parse metadata items.
  ParsableByteArray ilst = ilstAtom.data;
  ilst.setPosition(Atom.HEADER_SIZE);
  ArrayList<Metadata.Entry> entries = new ArrayList<>();
  while (ilst.bytesLeft() > Atom.HEADER_SIZE) {
    int atomPosition = ilst.getPosition();
    int atomSize = ilst.readInt();
    int keyIndex = ilst.readInt() - 1;
    if (keyIndex >= 0 && keyIndex < keyNames.length) {
      String key = keyNames[keyIndex];
      Metadata.Entry entry =
          MetadataUtil.parseMdtaMetadataEntryFromIlst(ilst, atomPosition + atomSize, key);
      if (entry != null) {
        entries.add(entry);
      }
    } else {
      Log.w(TAG, "Skipped metadata with unknown key index: " + keyIndex);
    }
    ilst.setPosition(atomPosition + atomSize);
  }
  return entries.isEmpty() ? null : new Metadata(entries);
}
 

/**
 * Parses a metadata meta atom if it contains metadata with handler 'mdta'.
 *
 * @param meta The metadata atom to decode.
 * @return Parsed metadata, or null.
 */
@Nullable
public static Metadata parseMdtaFromMeta(Atom.ContainerAtom meta) {
  Atom.LeafAtom hdlrAtom = meta.getLeafAtomOfType(Atom.TYPE_hdlr);
  Atom.LeafAtom keysAtom = meta.getLeafAtomOfType(Atom.TYPE_keys);
  Atom.LeafAtom ilstAtom = meta.getLeafAtomOfType(Atom.TYPE_ilst);
  if (hdlrAtom == null
      || keysAtom == null
      || ilstAtom == null
      || AtomParsers.parseHdlr(hdlrAtom.data) != TYPE_mdta) {
    // There isn't enough information to parse the metadata, or the handler type is unexpected.
    return null;
  }

  // Parse metadata keys.
  ParsableByteArray keys = keysAtom.data;
  keys.setPosition(Atom.FULL_HEADER_SIZE);
  int entryCount = keys.readInt();
  String[] keyNames = new String[entryCount];
  for (int i = 0; i < entryCount; i++) {
    int entrySize = keys.readInt();
    keys.skipBytes(4); // keyNamespace
    int keySize = entrySize - 8;
    keyNames[i] = keys.readString(keySize);
  }

  // Parse metadata items.
  ParsableByteArray ilst = ilstAtom.data;
  ilst.setPosition(Atom.HEADER_SIZE);
  ArrayList<Metadata.Entry> entries = new ArrayList<>();
  while (ilst.bytesLeft() > Atom.HEADER_SIZE) {
    int atomPosition = ilst.getPosition();
    int atomSize = ilst.readInt();
    int keyIndex = ilst.readInt() - 1;
    if (keyIndex >= 0 && keyIndex < keyNames.length) {
      String key = keyNames[keyIndex];
      Metadata.Entry entry =
          MetadataUtil.parseMdtaMetadataEntryFromIlst(ilst, atomPosition + atomSize, key);
      if (entry != null) {
        entries.add(entry);
      }
    } else {
      Log.w(TAG, "Skipped metadata with unknown key index: " + keyIndex);
    }
    ilst.setPosition(atomPosition + atomSize);
  }
  return entries.isEmpty() ? null : new Metadata(entries);
}
 

/**
 * Parses a metadata meta atom if it contains metadata with handler 'mdta'.
 *
 * @param meta The metadata atom to decode.
 * @return Parsed metadata, or null.
 */
@Nullable
public static Metadata parseMdtaFromMeta(Atom.ContainerAtom meta) {
  Atom.LeafAtom hdlrAtom = meta.getLeafAtomOfType(Atom.TYPE_hdlr);
  Atom.LeafAtom keysAtom = meta.getLeafAtomOfType(Atom.TYPE_keys);
  Atom.LeafAtom ilstAtom = meta.getLeafAtomOfType(Atom.TYPE_ilst);
  if (hdlrAtom == null
      || keysAtom == null
      || ilstAtom == null
      || AtomParsers.parseHdlr(hdlrAtom.data) != TYPE_mdta) {
    // There isn't enough information to parse the metadata, or the handler type is unexpected.
    return null;
  }

  // Parse metadata keys.
  ParsableByteArray keys = keysAtom.data;
  keys.setPosition(Atom.FULL_HEADER_SIZE);
  int entryCount = keys.readInt();
  String[] keyNames = new String[entryCount];
  for (int i = 0; i < entryCount; i++) {
    int entrySize = keys.readInt();
    keys.skipBytes(4); // keyNamespace
    int keySize = entrySize - 8;
    keyNames[i] = keys.readString(keySize);
  }

  // Parse metadata items.
  ParsableByteArray ilst = ilstAtom.data;
  ilst.setPosition(Atom.HEADER_SIZE);
  ArrayList<Metadata.Entry> entries = new ArrayList<>();
  while (ilst.bytesLeft() > Atom.HEADER_SIZE) {
    int atomPosition = ilst.getPosition();
    int atomSize = ilst.readInt();
    int keyIndex = ilst.readInt() - 1;
    if (keyIndex >= 0 && keyIndex < keyNames.length) {
      String key = keyNames[keyIndex];
      Metadata.Entry entry =
          MetadataUtil.parseMdtaMetadataEntryFromIlst(ilst, atomPosition + atomSize, key);
      if (entry != null) {
        entries.add(entry);
      }
    } else {
      Log.w(TAG, "Skipped metadata with unknown key index: " + keyIndex);
    }
    ilst.setPosition(atomPosition + atomSize);
  }
  return entries.isEmpty() ? null : new Metadata(entries);
}