static FrameBase ReadFrame(BinaryReader reader, string frameId, FrameFlags flags, uint frameSize)
{
#if NETSTANDARD2_0
var frameDataBuffer = reader.ReadBytes((int)frameSize);
#else
// Use heap allocations for frames > 256kB (usually pictures)
var frameDataBuffer = frameSize < 0x40000
? stackalloc byte[(int)frameSize]
: new byte[(int)frameSize];
reader.Read(frameDataBuffer);
#endif
return(FrameFactory.Build(frameId, flags, frameDataBuffer));
}
internal static TagModel Deserialize(Stream stream)
{
var tagModel = new TagModel();
tagModel.Header.Deserialize(stream);
if (tagModel.Header.Version != 3 & tagModel.Header.Version != 4)
{
throw new AudioUnsupportedException("ID3v2 Version " + tagModel.Header.Version + " is not supported.");
}
var id3TagSize = tagModel.Header.TagSize;
MemoryStream?memory = null;
try
{
if (tagModel.Header.Unsynchronisation)
{
memory = new(new byte[stream.Length]);
id3TagSize -= Sync.Unsafe(stream, memory, id3TagSize);
stream = memory;
if (id3TagSize <= 0)
{
throw new AudioInvalidException("Data is missing after the header.");
}
}
uint rawSize;
// Seek past the extended header
if (tagModel.Header.HasExtendedHeader)
{
tagModel.ExtendedHeader.Deserialize(stream);
rawSize = id3TagSize - 4 - tagModel.ExtendedHeader.Size;
if (id3TagSize <= 0)
{
throw new AudioInvalidException("Data is missing after the extended header.");
}
}
else
{
rawSize = id3TagSize;
}
// Tags should have at least one frame
if (rawSize <= 0)
{
throw new AudioInvalidException("No frames are present in the tag.");
}
uint index = 0;
#if NETSTANDARD2_0
var frameIdBuffer = new byte[4];
#else
Span <byte> frameIdBuffer = stackalloc byte[4];
#endif
while (index < rawSize)
{
// Read one byte first, looking for padding
#if NETSTANDARD2_0
stream.Read(frameIdBuffer, 0, 1);
#else
stream.Read(frameIdBuffer.Slice(0, 1));
#endif
// We reached the padding
if (frameIdBuffer[0] == 0)
{
tagModel.Header.PaddingSize = rawSize - index;
stream.Seek(tagModel.Header.PaddingSize - 1, SeekOrigin.Current);
break;
}
// 10 is the minimum size of a valid frame
if (index + 10 > rawSize)
{
throw new AudioInvalidException("Tag is corrupt: incomplete frame.");
}
// Read the rest of the frame ID
#if NETSTANDARD2_0
stream.Read(frameIdBuffer, 1, 3);
#else
stream.Read(frameIdBuffer.Slice(1, 3));
#endif
index += 4;
using (var reader = new TagReader(stream))
{
var frameSize = tagModel.Header.Version == 4
? reader.ReadUInt32SyncSafe()
: reader.ReadUInt32BigEndian();
index += 4;
// The size of the frame can't be larger than the available space
if (frameSize > rawSize - index)
{
throw new AudioInvalidException(
"A frame is corrupt: can't be larger than the available space remaining.");
}
var flags = new FrameFlags(reader.ReadUInt16BigEndian(), tagModel.Header.Version);
index += 2;
tagModel.Frames.Add(ReadFrame(reader,
#if NETSTANDARD2_0
Encoding.ASCII.GetString(frameIdBuffer, 0, 4), flags, frameSize));
#else
Encoding.ASCII.GetString(frameIdBuffer), flags, frameSize));
#endif
index += frameSize;
}
}
return(tagModel);
}
finally
{
memory?.Close();
}
}
