/*
* xx xx xx xx Frame identifier
* xx xx xx xx Frame size excluding frame header
* xx xx Frame flags
* additinal header bytes(group identifier, encryption, compression)
* Frame content
* Note: Unsynchronisation is done on Tag level, Compression and Encryption on Frame level.
*/
private static void EncodeID3v2_3Frame(Stream s, Frame frame, ID3v2Tag tag)
{
byte flagByteHi, flagByteLo, encryptionSymbol = 0;
byte[] data = frame.EncodeContent(tag);
int additionalBytes = 0, originalSize = data.Length;
/* generate frame flags */
flagByteHi = 0;
if ((frame.Flags & FrameFlags.PreserveTagAltered) == 0) {
/* discard frame if tag altered is 1! */
flagByteHi |= 0x80;
}
if ((frame.Flags & FrameFlags.PreserveFileAltered) == 0) {
/* discard frame if file altered is 1! */
flagByteHi |= 0x40;
}
if ((frame.Flags & FrameFlags.ReadOnly) == FrameFlags.ReadOnly) {
flagByteHi |= 0x20;
}
flagByteLo = 0;
if ((frame.Flags & FrameFlags.Compress) == FrameFlags.Compress) {
/* set bit 0x80 in flag and append 4 bytes of uncompressed size after header */
flagByteLo |= 0x80;
additionalBytes += 4;
data = CompressData(data);
}
if ((frame.Flags & FrameFlags.Encrypt) == FrameFlags.Encrypt) {
/* set bit 0x40 in flag and append 1 byte indicating encryption method after header */
flagByteLo |= 0x40;
additionalBytes++;
data = EncryptData(data, frame, out encryptionSymbol);
}
if (frame.GroupIdentifier != Frame.GroupIdNotSet) {
flagByteLo |= 0x20;
additionalBytes++;
}
/* Write Header */
StringEncoder.WriteLatin1String(s, frame.FrameId, 4);
NumberConverter.WriteInt(data.Length + additionalBytes, s, 4, false);
s.WriteByte(flagByteHi);
s.WriteByte(flagByteLo);
/* Write additional information */
if ((frame.Flags & FrameFlags.Compress) == FrameFlags.Compress) {
NumberConverter.WriteInt(originalSize, s, 4, false);
}
if ((frame.Flags & FrameFlags.Encrypt) == FrameFlags.Encrypt) {
s.WriteByte(encryptionSymbol);
}
if (frame.GroupIdentifier != Frame.GroupIdNotSet) {
s.WriteByte((byte)frame.GroupIdentifier);
}
/* write data */
s.Write(data, 0, data.Length);
}
/*
* xx xx xx Frame identifier
* xx xx xx Frame size excluding frame header
* Frame content
* Note: Unsynchronisation is done on Tag level, no Compression or Encryption schema defined.
*/
private static void EncodeID3v2_2Frame(Stream s, Frame frame, ID3v2Tag tag)
{
string id;
byte[] data;
id = FrameFactory.ID3v2_3IdToID3v2_2Id(frame.FrameId);
data = frame.EncodeContent(tag);
StringEncoder.WriteLatin1String(s, id, 3);
NumberConverter.WriteInt(data.Length, s, 3, false);
s.Write(data, 0, data.Length);
}
internal static void EncodeFrame(Stream s, Frame frame, ID3v2Tag tag)
{
switch (tag.Version) {
case ID3v2Version.ID3v2_2:
EncodeID3v2_2Frame(s, frame, tag);
break;
case ID3v2Version.ID3v2_3:
EncodeID3v2_3Frame(s, frame, tag);
break;
case ID3v2Version.ID3v2_4:
EncodeID3v2_4Frame(s, frame, tag);
break;
default:
throw new InvalidEnumArgumentException("tag.Version", (int)tag.Version, typeof(ID3v2Version));
}
}
private static byte[] EncryptData(byte[] frameData, Frame f, out byte encryptionSymbol)
{
throw new NotImplementedException("Encrytion is not yet implemented");
}
/*
* xx xx xx xx Frame identifier
* xx xx xx xx Frame size excluding frame header as sync safe integer
* xx xx Frame flags
* additinal header bytes(group identifier, encryption, compression, data length indicator)
* Frame content
* Note: Unsynchronisation, Compression and Encryption is done on Frame level.
*/
private static void EncodeID3v2_4Frame(Stream s, Frame frame, ID3v2Tag tag)
{
bool setDataLengthIndicator = false;
byte flagByteHi, flagByteLo, encryptionSymbol = 0;
byte[] data = frame.EncodeContent(tag);
int additionalBytes = 0, originalSize = data.Length;
/* build the flag bytes */
flagByteHi = 0;
if ((frame.Flags & FrameFlags.PreserveTagAltered) == 0) {
flagByteHi |= 0x40;
}
if ((frame.Flags & FrameFlags.PreserveFileAltered) == 0) {
flagByteHi |= 0x20;
}
if ((frame.Flags & FrameFlags.ReadOnly) == FrameFlags.ReadOnly) {
flagByteHi |= 0x20;
}
flagByteLo = 0;
if (frame.GroupIdentifier != Frame.GroupIdNotSet) {
/* add one byte after header(group identifier) */
flagByteLo |= 0x40;
additionalBytes++;
}
if ((frame.Flags & FrameFlags.Compress) == FrameFlags.Compress) {
flagByteLo |= 0x08;
setDataLengthIndicator = true;
data = CompressData(data);
}
if ((frame.Flags & FrameFlags.Encrypt) == FrameFlags.Encrypt) {
flagByteLo |= 0x04;
additionalBytes++;
setDataLengthIndicator = true;
data = EncryptData(data, frame, out encryptionSymbol);
}
if ((tag.Flags & ID3v2TagFlags.Unsync) == ID3v2TagFlags.Unsync) {
flagByteLo |= 0x02;
setDataLengthIndicator = true;
data = Util.ApplyUnsynchronization(data);
}
if (setDataLengthIndicator) {
flagByteLo |= 0x01;
additionalBytes += 4;
}
/* write frame header */
StringEncoder.WriteLatin1String(s, frame.FrameId, 4);
NumberConverter.WriteInt(data.Length + additionalBytes, s, 4, true);
s.WriteByte(flagByteHi);
s.WriteByte(flagByteLo);
/* write attached data */
if (frame.GroupIdentifier != Frame.GroupIdNotSet) {
s.WriteByte((byte)frame.GroupIdentifier);
}
if ((frame.Flags & FrameFlags.Encrypt) == FrameFlags.Encrypt) {
s.WriteByte(encryptionSymbol);
}
if (setDataLengthIndicator) {
NumberConverter.WriteInt(originalSize, s, 4, true);
}
s.Write(data, 0, data.Length);
}
