Sample code for decompressing the header of Dragon Mania Legends PAK files

DragonManiaLegendsPAK.cs

// iterate each sample file
foreach (var sample in Directory.GetFiles(@"C:\Users\temp\Downloads\sample"))
{
    // open the file stream and create a reader
    using var stream = File.OpenRead(sample);
    using var reader = new BinaryReader(stream);

    // read the header
    var magic = reader.ReadString(4);
    var fileTableCompressedSize = reader.ReadInt32();
    var fileTableDecompressedSize = reader.ReadInt32();

    // create our zstd decompressor
    var decompressor = new ZstdSharp.Decompressor();

    // read and decompress the compressed file table bytes
    var compressedFileTableBytes = reader.ReadBytes(fileTableCompressedSize);
    var decompressedFileTableBytes = decompressor.Unwrap(compressedFileTableBytes);
    
    // check it decompressed correctly
    Debug.Assert(decompressedFileTableBytes.Length == fileTableDecompressedSize);

    // convert our decompressed bytes to a stream
    // and create a new reader to simplify things
    using var tblStream = new MemoryStream(decompressedFileTableBytes.ToArray());
    using var tblReader = new BinaryReader(tblStream);

    // create a filetable collection
    var fileTable = new List<FileTableEntry>();

    // iterate to end of 
    while (tblReader.BaseStream.Position != tblReader.BaseStream.Length)
    {
        // read the entry and add to collection
        var nameLen = tblReader.ReadInt32();
        var name = tblReader.ReadString(nameLen);
        var compressedSize = tblReader.ReadInt32();
        var decompressedSize = tblReader.ReadInt32();

        fileTable.Add(new FileTableEntry()
        {
            NameLen = nameLen,
            Name = name,
            CompressedSize = compressedSize,
            DecompressedSize = decompressedSize
        });
    }
}

This example uses oleg-st's ZstdSharp for ZStandard decompression.