/// <summary>
/// Extracts the field data from the raw data portion of an
/// ID3v2 frame.
/// </summary>
/// <param name="frameData">
/// A <see cref="ByteVector" /> object containing fraw frame
/// data.
/// </param>
/// <param name="offset">
/// A <see cref="int" /> value containing the index at which
/// the data is contained.
/// </param>
/// <param name="version">
/// A <see cref="byte" /> value containing the ID3v2 version
/// of the data.
/// </param>
/// <returns>
/// A <see cref="ByteVector" /> object containing the
/// extracted field data.
/// </returns>
/// <remarks>
/// This method is necessary for extracting extra data
/// prepended to the frame such as the grouping ID.
/// </remarks>
/// <exception cref="ArgumentNullException">
/// <paramref name="frameData" /> is <see langword="null" />.
/// </exception>
protected ByteVector FieldData(ByteVector frameData,
int offset, byte version)
{
if (frameData == null)
{
throw new ArgumentNullException("frameData");
}
int data_offset = offset + (int)FrameHeader.Size(version);
int data_length = (int)Size;
if ((Flags & (FrameFlags.Compression |
FrameFlags.DataLengthIndicator)) != 0)
{
data_offset += 4;
data_length -= 4;
}
if ((Flags & FrameFlags.GroupingIdentity) != 0)
{
if (frameData.Count >= data_offset)
{
throw new CorruptFileException(
"Frame data incomplete.");
}
group_id = frameData [data_offset++];
data_length--;
}
if ((Flags & FrameFlags.Encryption) != 0)
{
if (frameData.Count >= data_offset)
{
throw new CorruptFileException(
"Frame data incomplete.");
}
encryption_id = frameData [data_offset++];
data_length--;
}
data_length = Math.Min(data_length, frameData.Count - data_offset);
if (data_length < 0)
{
throw new CorruptFileException(
"Frame size less than zero.");
}
ByteVector data = frameData.Mid(data_offset,
data_length);
if ((Flags & FrameFlags.Unsynchronisation) != 0)
{
int before_length = data.Count;
SynchData.ResynchByteVector(data);
data_length -= (data.Count - before_length);
}
// FIXME: Implement encryption.
if ((Flags & FrameFlags.Encryption) != 0)
{
throw new NotImplementedException();
}
// FIXME: Implement compression.
if ((Flags & FrameFlags.Compression) != 0)
{
throw new NotImplementedException();
}
/*
* if(d->header->compression()) {
* ByteVector data(frameDataLength);
* uLongf uLongTmp = frameDataLength;
* ::uncompress((Bytef *) data.data(),
* (uLongf *) &uLongTmp,
* (Bytef *) frameData.data() + frameDataOffset,
* size());
* return data;
* }
*/
return(data);
}
/// <summary>
/// Creates a <see cref="Frame" /> object by reading it from
/// raw ID3v2 frame data.
/// </summary>
/// <param name="data">
/// A <see cref="ByteVector" /> object containing a raw ID3v2
/// frame.
/// </param>
/// <param name="offset">
/// A <see cref="int" /> value reference specifying at what
/// index in <paramref name="data" /> at which the frame
/// begins. After reading, it contains the offset of the next
/// frame to be read.
/// </param>
/// <param name="version">
/// A <see cref="byte" /> value specifying the ID3v2 version
/// the frame in <paramref name="data"/> is encoded in.
/// </param>
/// <param name="alreadyUnsynched">
/// A <see cref="bool" /> value specifying whether the entire
/// tag has already been unsynchronized.
/// </param>
/// <returns>
/// A <see cref="Frame" /> object read from the data, or <see
/// langword="null" /> if none is found.
/// </returns>
/// <exception cref="System.NotImplementedException">
/// The frame contained in the raw data could not be
/// converted to ID3v2 or uses encryption or compression.
/// </exception>
public static Frame CreateFrame(ByteVector data,
ref int offset, byte version, bool alreadyUnsynched)
{
int position = offset;
FrameHeader header = new FrameHeader(data.Mid(position,
(int)FrameHeader.Size(version)), version);
offset += (int)(header.FrameSize + FrameHeader.Size(
version));
if (header.FrameId == null)
{
throw new System.NotImplementedException();
}
foreach (byte b in header.FrameId)
{
char c = (char)b;
if ((c < 'A' || c > 'Z') &&
(c < '1' || c > '9'))
{
return(null);
}
}
if (alreadyUnsynched)
{
// Mark the frame as not Unsynchronozed because the entire
// tag has already been Unsynchronized
header.Flags &= ~FrameFlags.Unsynchronisation;
}
// Windows Media Player may create zero byte frames.
// Just send them off as unknown and delete them.
if (header.FrameSize == 0)
{
header.Flags |= FrameFlags.TagAlterPreservation;
return(new UnknownFrame(data, position, header,
version));
}
// TODO: Support Compression.
if ((header.Flags & FrameFlags.Compression) != 0)
{
throw new System.NotImplementedException();
}
// TODO: Support Encryption.
if ((header.Flags & FrameFlags.Encryption) != 0)
{
throw new System.NotImplementedException();
}
foreach (FrameCreator creator in frame_creators)
{
Frame frame = creator(data, position, header,
version);
if (frame != null)
{
return(frame);
}
}
// This is where things get necissarily nasty. Here we
// determine which Frame subclass (or if none is found
// simply an Frame) based on the frame ID. Since there
// are a lot of possibilities, that means a lot of if
// blocks.
// Text Identification (frames 4.2)
if (header.FrameId == FrameType.TXXX)
{
return(new UserTextInformationFrame(data,
position, header, version));
}
if (header.FrameId [0] == (byte)'T')
{
return(new TextInformationFrame(data, position,
header, version));
}
// Unique File Identifier (frames 4.1)
if (header.FrameId == FrameType.UFID)
{
return(new UniqueFileIdentifierFrame(data,
position, header, version));
}
// Music CD Identifier (frames 4.5)
if (header.FrameId == FrameType.MCDI)
{
return(new MusicCdIdentifierFrame(data,
position, header, version));
}
// Unsynchronized Lyrics (frames 4.8)
if (header.FrameId == FrameType.USLT)
{
return(new UnsynchronisedLyricsFrame(data,
position, header, version));
}
// Synchronized Lyrics (frames 4.9)
if (header.FrameId == FrameType.SYLT)
{
return(new SynchronisedLyricsFrame(data,
position, header, version));
}
// Comments (frames 4.10)
if (header.FrameId == FrameType.COMM)
{
return(new CommentsFrame(data, position,
header, version));
}
// Relative Volume Adjustment (frames 4.11)
if (header.FrameId == FrameType.RVA2)
{
return(new RelativeVolumeFrame(data, position,
header, version));
}
// Attached Picture (frames 4.14)
if (header.FrameId == FrameType.APIC)
{
return(new AttachedPictureFrame(data, position,
header, version));
}
// General Encapsulated Object (frames 4.15)
if (header.FrameId == FrameType.GEOB)
{
return(new GeneralEncapsulatedObjectFrame(data,
position, header, version));
}
// Play Count (frames 4.16)
if (header.FrameId == FrameType.PCNT)
{
return(new PlayCountFrame(data, position,
header, version));
}
// Play Count (frames 4.17)
if (header.FrameId == FrameType.POPM)
{
return(new PopularimeterFrame(data, position,
header, version));
}
// Terms of Use (frames 4.22)
if (header.FrameId == FrameType.USER)
{
return(new TermsOfUseFrame(data, position,
header, version));
}
// Private (frames 4.27)
if (header.FrameId == FrameType.PRIV)
{
return(new PrivateFrame(data, position, header,
version));
}
return(new UnknownFrame(data, position, header,
version));
}