/// <summary>
/// Decodes a lavalink track identifier.
/// </summary>
/// <param name="buffer">the raw track identifier</param>
/// <param name="verify">a value indicating whether the track header should be verified</param>
/// <returns>the decoded track info</returns>
/// <exception cref="InvalidOperationException">thrown if the track header is invalid</exception>
/// <exception cref="ArgumentNullException">
/// thrown if the specified <paramref name="buffer"/> is <see langword="null"/>.
/// </exception>
public static LavalinkTrackInfo DecodeTrackInfo(byte[] buffer, bool verify = true)
{
if (buffer is null)
{
throw new ArgumentNullException(nameof(buffer));
}
using (var memoryStream = new MemoryStream(buffer))
using (var reader = new DataInputReader(memoryStream))
{
ReadHeader(reader, buffer.Length, verify);
var title = reader.ReadString();
var author = reader.ReadString();
var length = reader.ReadInt64();
var identifier = reader.ReadString();
var isStream = reader.ReadBoolean();
var uri = reader.ReadBoolean() ? reader.ReadString() : null;
return(new LavalinkTrackInfo
{
Title = title,
Author = author,
Duration = TimeSpan.FromMilliseconds(length),
TrackIdentifier = identifier,
IsLiveStream = isStream,
IsSeekable = !isStream,
Source = uri
});
}
}
/// <summary>
/// Reads the track header.
/// </summary>
/// <param name="reader">the reader to read from</param>
/// <param name="length">the length of raw binary data</param>
/// <param name="verify">a value indicating whether the track header should be verified</param>
/// <exception cref="InvalidOperationException">thrown if the track header is invalid</exception>
/// <exception cref="ArgumentNullException">
/// thrown if the specified <paramref name="reader"/> is <see langword="null"/>.
/// </exception>
private static void ReadHeader(DataInputReader reader, int length, bool verify = true)
{
if (reader is null)
{
throw new ArgumentNullException(nameof(reader));
}
// the header is four bytes long, subtract
length -= 4;
var header = reader.ReadInt32();
var flags = (int)((header & 0xC0000000L) >> 30);
var hasVersion = (flags & 1) != 0;
var version = hasVersion ? reader.ReadSByte() : 1;
var size = header & 0x3FFFFFFF;
// verify size
if (verify && size != length)
{
throw new InvalidOperationException($"Error while verifying track header: Track Identifier length was {length}, but expected: {size}");
}
// verify version
if (verify && version != 2)
{
throw new InvalidOperationException($"Error while verifying track header: Invalid track version: Was: {version}, expected: 2.");
}
}
