using System;
using System.Runtime.InteropServices;

class Program
{
    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
    public delegate uint Ret1ArgDelegate(uint arg1);

    [DllImport("kernel32.dll", SetLastError=true)]
    static extern IntPtr VirtualAlloc(IntPtr lpAddress, UIntPtr dwSize,
                                      AllocationType flAllocationType, MemoryProtection flProtect);
                                      
    [DllImport("kernel32.dll", SetLastError=true)]
    static extern bool VirtualFree(IntPtr lpAddress, UIntPtr dwSize,
                                   FreeType freeType);
                                   
  [Flags]
  public enum AllocationType:uint
  {
    COMMIT=0x1000,
    RESERVE=0x2000,
    RESET=0x80000,
    LARGE_PAGES=0x20000000,
    PHYSICAL=0x400000,
    TOP_DOWN=0x100000,
    WRITE_WATCH=0x200000
  }

  [Flags]
  public enum MemoryProtection:uint
  {
    EXECUTE=0x10,
    EXECUTE_READ=0x20,
    EXECUTE_READWRITE=0x40,
    EXECUTE_WRITECOPY=0x80,
    NOACCESS=0x01,
    READONLY=0x02,
    READWRITE=0x04,
    WRITECOPY=0x08,
    GUARD_Modifierflag=0x100,
    NOCACHE_Modifierflag = 0x200,
    WRITECOMBINE_Modifierflag = 0x400
  }

  [Flags]
  public enum FreeType:uint
  {
    DECOMMIT = 0x4000,
    RELEASE = 0x8000
  }    
  
  public static byte[] asmBytesX86 = new byte[]
        {        
0x55,             // push ebp
0x8B, 0xEC,       // mov ebp, esp 
0x8B, 0x45, 0x08, // mov eax, [ebp+8]
0xD1, 0xC8,       // ror eax, 1
0x5D,             // pop ebp 
0xC3              // ret
        };
        
  public static byte[] asmBytesX64 = new byte[]
        {        
0x89, 0xC8,       // mov rax, rcx 
0xD1, 0xC8,       // ror eax, 1
0xC3              // ret
        };
        
  static void Main(string[] args)
  {
    	byte[] asmBytes = (IntPtr.Size == 4)?asmBytesX86:asmBytesX64;
    	IntPtr executableMemory = VirtualAlloc(IntPtr.Zero, (UIntPtr) asmBytes.Length, AllocationType.COMMIT, MemoryProtection.EXECUTE_READWRITE);
    	Marshal.Copy(asmBytes, 0, executableMemory, asmBytes.Length);
        Ret1ArgDelegate del = (Ret1ArgDelegate) Marshal.GetDelegateForFunctionPointer (executableMemory, typeof(Ret1ArgDelegate));
	
        uint n = (uint)0xFFFFFFFC;
        n = del(n);
        Console.WriteLine("{0:x}", n);
         
        VirtualFree(executableMemory, UIntPtr.Zero, FreeType.DECOMMIT);
    }
}