Firmware.cs

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

namespace BootMan
{
    internal static class Firmware
    {
        public enum FirmwareType
        {
            FirmwareTypeUnknown,
            FirmwareTypeBios,
            FirmwareTypeUefi,
            FirmwareTypeMax,
        }

        public static readonly string EFI_GLOBAL_VARIABLE = "{8BE4DF61-93CA-11D2-AA0D-00E098032B8C}";

        private static class NativeMethods
        {
            [DllImport("Kernel32.dll", SetLastError = true)]
            internal static extern bool GetFirmwareType(out FirmwareType firmwareType);

            [DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
            internal static extern uint GetFirmwareEnvironmentVariable(
                string lpName,
                string lpGuid,
                byte[] lpBuffer,
                int nBufferSizeInBytes
            );

            [DllImport("Kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
            internal static extern bool SetFirmwareEnvironmentVariable(
                string lpName,
                string lpGuid,
                byte[] lpBuffer,
                int nBufferSizeInBytes
            );
        }

        public static unsafe T GetFirmwareEnvironmentVariable<T>(string name, string guid) where T : unmanaged
        {
            var buffer = new byte[sizeof(T)];
            uint size = NativeMethods.GetFirmwareEnvironmentVariable(name, guid, buffer, buffer.Length);
            if (size == 0)
            {
                throw new Win32Exception();
            }
            return MemoryMarshal.Cast<byte, T>(buffer)[0];
        }

        public static FirmwareType GetFirmwareType()
        {
            bool success = NativeMethods.GetFirmwareType(out FirmwareType firmwareType);
            if (!success)
            {
                throw new Win32Exception();
            }
            return firmwareType;
        }
    }
}