private static Stream GetStream(Stream stream)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream));
}
var position = stream.Position;
var parse = RNCHeader.TryParse(stream, out var header);
stream.Position = position; // restore position in case of not-RNC
if (!parse)
{
return(stream);
}
var input = new byte[stream.Length];
var output = new byte[header.UncompressedSize];
var read = stream.Read(input, 0, input.Length);
if (read != input.Length)
{
throw new EndOfStreamException("Couldn't read entire stream.");
}
var p1 = Marshal.AllocHGlobal(input.Length);
var p2 = Marshal.AllocHGlobal(output.Length);
Marshal.Copy(input, 0, p1, input.Length);
Marshal.Copy(output, 0, p2, output.Length);
var status = Unpack(p1, p2);
if (status == RNCStatus.Ok)
{
Marshal.Copy(p2, output, 0, output.Length);
}
Marshal.FreeHGlobal(p1);
Marshal.FreeHGlobal(p2);
if (status != RNCStatus.Ok)
{
throw new InvalidOperationException($"Error while unpacking: '{status}'.");
}
return(new MemoryStream(output));
}
/// <summary>
/// Tries to parse an instance from a stream.
/// </summary>
/// <param name="stream"></param>
/// <param name="result"></param>
/// <returns>
/// <c>true</c> if a header was found and compression scheme is supported.
/// </returns>
public static bool TryParse(Stream stream, out RNCHeader result)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream));
}
result = default(RNCHeader);
var reader = new BinaryReader(stream);
var signature = Encoding.ASCII.GetString(reader.ReadBytes(3));
if (signature != "RNC")
{
return(false);
}
var compression = (RNCCompression)reader.ReadByte();
if (compression != RNCCompression.Method1)
{
return(false);
}
var uncompressedSize = ReadUInt32BE(reader);
var compressedSize = ReadUInt32BE(reader);
var uncompressedSum = ReadUInt16BE(reader);
var compressedSum = ReadUInt16BE(reader);
var leeway = reader.ReadByte();
var packChunks = reader.ReadByte();
result = new RNCHeader(
signature, compression, uncompressedSize, compressedSize,
uncompressedSum, compressedSum, leeway, packChunks
);
return(true);
}
