Sonic 4 PC AMB Repacker

Sonic4AMB.cs

using System;
using System.IO;
using System.Text;

namespace AMBRepack
{
    class Program
    {
        private const uint MAGIC = 0x424d4123u; // #AMB
        private const uint MAGIC_2 = 0x00000020u;
        private const uint MAGIC_WITH_A_VENGEANCE = 0x00040000u;
        private const uint LIVE_FREE_OR_MAGIC_HARD = 0xFFFFFFFFu;

        static void Main(string[] args)
        {
            if (args.Length < 1)
                return;

            var directory = args[0];
            var output = args[1];
            output = Path.ChangeExtension(output, "AMB").ToUpperInvariant();

            var files = new DirectoryInfo(directory).GetFiles();

            using (var fileStream = File.Create(output))
            using (var writer = new BinaryWriter(fileStream, Encoding.ASCII, true))
            {
                writer.Write(MAGIC);
                writer.Write(MAGIC_2); // unused in game :omegalul:
                writer.Write(MAGIC_WITH_A_VENGEANCE);
                writer.Write(0);

                // file count now
                writer.Write(files.Length);

                // entry table offset next
                writer.Write(0x20); // safe to assume

                // then data offset
                writer.Write(0x20 + (0x10 * files.Length)); // easy to calculate

                // then string table offset (we'll write this later)

                fileStream.Position = 0x20;

                var offset = (long)(0x20 + (0x10 * files.Length));

                // let's write the entries then
                for (var i = 0; i < files.Length; i++)
                {
                    var file = files[i];

                    writer.Write((uint)offset);
                    writer.Write((uint)file.Length);
                    writer.Write(LIVE_FREE_OR_MAGIC_HARD);
                    writer.Write(0);

                    offset += file.Length;
                }

                // now the content
                for (int i = 0; i < files.Length; i++)
                {
                    var file = files[i];
                    using (var newFileStream = file.OpenRead())
                    {
                        newFileStream.CopyTo(fileStream);
                    }
                }

                // now we're at the string offset table
                var stringTablePosition = (uint)fileStream.Position;

                // let's write that
                fileStream.Seek(0x1C, SeekOrigin.Begin);
                writer.Write(stringTablePosition);

                fileStream.Seek(stringTablePosition, SeekOrigin.Begin);

                var array = new char[0x20];
                // and let's write the table itself
                for (int i = 0; i < files.Length; i++)
                {
                    for (int j = 0; j < array.Length; j++)
                        array[j] = (char)0; // clear the array

                    var file = files[i];
                    var fileName = file.Name.ToUpperInvariant();
                    if (fileName.Length > 0x20)
                    {
                        Console.WriteLine($"Truncating {fileName}! This is bad!!");
                        fileName = fileName.Substring(0, 0x20);
                    }

                    fileName.CopyTo(0, array, 0, fileName.Length);

                    for (int j = 0; j < array.Length; j++)
                        writer.Write((byte)array[j]);
                }
            }
        }
    }
}