Program.cs

using System.Text;
using ICSharpCode.SharpZipLib.GZip;

namespace BFLExtractCsharp;

internal abstract class Program
{
    private static int Main(string[] args)
    {
        foreach (var arg in args)
        {
            if (!File.Exists(arg))
            {
                Console.WriteLine("File not found: {0}", arg);
                return 1;
            }
            Stream decompressed = new MemoryStream();
            Console.WriteLine("Decompressing...");
            try
            {
                GZip.Decompress(File.OpenRead(arg), decompressed, false);
            }
            catch (GZipException)
            {
                Console.WriteLine("Decompression failed - will continue assuming the file is not actually compressed");
                decompressed = File.OpenRead(arg);
            }
            var buff = new byte[4];
            decompressed.Position = 0;
            decompressed.ReadExactly(buff);
            var magic = Encoding.ASCII.GetString(buff);
            var headerSize = magic == "CMPR" ? 8 : 0;
            decompressed.Position = 0;
            var outDir = Path.Join(new FileInfo(arg).DirectoryName, Path.GetFileNameWithoutExtension(arg) + "_extracted");
            if (!Directory.Exists(outDir)) Directory.CreateDirectory(outDir);
            _ = new BflFormat(decompressed, outDir, headerSize);
        }

        return 0;
    }
}