using System;
using System.Runtime.InteropServices;

namespace exeinfo
{
    public static class MZ
    {
        public const ushort Signature = 0x5A4D;

		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		public struct Header
        {
			public ushort signature;
			public ushort bytes_in_last_block;
			public ushort blocks_in_file;
			public ushort num_relocs;
			public ushort header_paragraphs;
			public ushort min_extra_paragraphs;
			public ushort max_extra_paragraphs;
			public ushort ss;
			public ushort sp;
			public ushort checksum;
			public ushort ip;
			public ushort cs;
			public ushort reloc_table_offset;
			public ushort overlay_number;
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 4)]
            public ushort[] reserved;
            public ushort oem_id;
            public ushort oem_info;
			[MarshalAs(UnmanagedType.ByValArray, SizeConst = 10)]
			public ushort[] reserved2;
            public uint new_offset;
        }

		[StructLayout(LayoutKind.Sequential, Pack = 1)]
		struct RelocationTableEntry
		{
			public ushort offset;
			public ushort segment;
		}

        public static void PrintInfo(Header header)
        {
            Console.WriteLine("DOS MZ executable:");
			Console.WriteLine("\tBlocks in file: {0}", header.blocks_in_file);
			Console.WriteLine("\t{0} bytes used in last block", header.bytes_in_last_block == 0 ? 512 : header.bytes_in_last_block);
			Console.WriteLine("\t{0} relocations present after the header", header.num_relocs);
			Console.WriteLine("\t{0} paragraphs in header", header.header_paragraphs);
			Console.WriteLine("\t{0} paragraphs of additional memory required", header.min_extra_paragraphs);
			Console.WriteLine("\t{0} paragraphs of additional memory requested", header.max_extra_paragraphs);
            Console.WriteLine("\tSegment address for SS: {0:X4}h", header.ss);
            Console.WriteLine("\tInitial value of SP: {0:X4}h", header.sp);
            Console.WriteLine("\tInitial value of IP: {0:X4}h", header.ip);
            Console.WriteLine("\tInitial value of CS: {0:X4}h", header.cs);
			Console.WriteLine("\tOffset to relocation table: {0}", header.reloc_table_offset);
			Console.WriteLine("\tFile contains {0} overlays", header.overlay_number);
			Console.WriteLine("\tFile checksum: 0x{0:X4}", header.checksum);
            Console.WriteLine("\tOEM ID: {0}", header.oem_id);
			Console.WriteLine("\tOEM information: 0x{0:X4}", header.oem_info);
			Console.WriteLine("\tOffset to new header: {0}", header.new_offset);
		}
    }
}