static class Program
{
    static byte[] lockkey;//自行从libtolua.so中取出
    static byte[] unlockkey;//自行从libtolua.so中取出

    static void Main(string[] args)
    {
        var bytes = File.ReadAllBytes(args[0]);
        var reader = new BinaryReader(new MemoryStream(bytes));
        //_read_header
        var magic = reader.ReadBytes(3);
        var version = reader.ReadByte();
        var bits = reader.ReadUleb128();
        var is_stripped = ((bits & 2u) != 0u);
        if (!is_stripped)
        {
            var length = reader.ReadUleb128();
            var name = Encoding.UTF8.GetString(reader.ReadBytes((int)length));
        }
        //_read_prototypes
        while (reader.BaseStream.Position < reader.BaseStream.Length)
        {
            var size = reader.ReadUleb128();
            if (size == 0)
                break;
            var next = reader.BaseStream.Position + size;
            bits = reader.ReadByte();//_read_flags
            var arguments_count = reader.ReadByte();//_read_counts_and_sizes
            var framesize = reader.ReadByte();
            var upvalues_count = reader.ReadByte();
            var complex_constants_count = reader.ReadUleb128();
            var numeric_constants_count = reader.ReadUleb128();
            var instructions_count = reader.ReadUleb128();
            var start = (int)reader.BaseStream.Position;
            //加密
            /*bytes[3] = 0x80;
            bytes = lj_bclock(start, bytes, (int)instructions_count);*/
            //解密
            bytes[3] = 2;
            bytes = lj_bcunlock(start, bytes, (int)instructions_count);
            //
            reader.BaseStream.Position = next;
        }
        File.WriteAllBytes(args[0], bytes);
    }

    static byte[] lj_bclock(int start, byte[] bytes, int count)
    {
        var result = start;
        result += 4;
        var v2 = 0;
        do
        {
            var v3 = bytes[result - 4];
            result += 4;
            var v4 = bytes[result - 7] ^ v2++;
            bytes[result - 8] = (byte)(lockkey[v3] ^ v4);
        }
        while (v2 != count);
        return bytes;
    }

    static byte[] lj_bcunlock(int start, byte[] bytes, int count)
    {
        var result = start;
        result += 4;
        var v2 = 0;
        do
        {
            var v3 = bytes[result - 4];
            result += 4;
            var v4 = bytes[result - 7] ^ v3 ^ (v2++ & 0xFF);
            bytes[result - 8] = unlockkey[v4];
        }
        while (v2 != count);
        return bytes;
    }

    static public uint ReadUleb128(this BinaryReader reader)
    {
        uint value = reader.ReadByte();
        if (value >= 0x80)
        {
            var bitshift = 0;
            value &= 0x7f;
            while (true)
            {
                var b = reader.ReadByte();
                bitshift += 7;
                value |= (uint)((b & 0x7f) << bitshift);
                if (b < 0x80)
                    break;
            }
        }
        return value;
    }
}