Delphi to C#

Question

Delphi

Good afternoon!

I ran into a problem that arose in the process of translating a program from Delphi to C#.

There is the following Delphi code:

procedure  TForm1 . FormCreate ( Sender :  TObject ) ;
var  pFD  :  pChar ;
begin
  fMH  : =  CreateFileMapping ( INVALID_HANDLE_VALUE ,  nil ,  PAGE_READWRITE ,  0 ,  sizeof ( longint ) ,  'MM_MAP' ) ;
  if  ( fMH <>  0 )  then
  begin
    pFD  : =  MapViewOfFile (fMH ,  FILE_MAP_WRITE ,  0 ,  0 ,  0 ) ;
    if  Assigned ( pFD )  then
    try
      pLongint ( pFD ) ^ : =  Self . handle ;
    finally
      UnmapViewOfFile ( pFD ) ;
    end ;
  end ;
end ;

I am not a big connoisseur of C#, so I can not figure out what the problem is. My code:

private  const  int  WM_COPYDATA  =  0x4A ;
private  IntPtr INVALID_HANDLE_VALUE  =  new  IntPtr ( - 1 ) ;
 
private  void  Form1_Load ( object  sender, EventArgs e )
{
  fh  =  Win32API. CreateFileMapping ( INVALID_HANDLE_VALUE, IntPtr. Zero , Win32API. FileMapProtection . PageReadWrite ,  0 , Int32. MaxValue ,  "MM_MAP" ) ;
  if  ( fh  !=  IntPtr. Zero )
  {
    IntPtr fd  =  ( IntPtr ) Win32API. MapViewOfFile ( fh, Win32API. FileMapAccess . FileMapWrite ,  0 ,  0 ,  0 ) ;
    if  ( fd  !=  IntPtr. Zero )
      try
      {
        Marshal. WriteIntPtr ( fd,  this . Handle ) ;
      }
      finally
      {
        Win32 API. UnmapViewOfFile ( fd ) ;
      }
  }
}

The actual task of the program is as follows: when starting, write your descriptor to memory (if I didn’t mess up anything in the terminology), and then receive the WM_COPYDATA system messages, which need to be processed.

Potentially, I see three problem areas:

• the INVALID_HANDLE_VALUE value is incorrectly set, but then I could not find how to do it correctly ...
• Marshal.WriteIntPtr(fd, this.Handle); does not work adequately, in the sense that the result does not correspond to the Denf variant pLongint(pFD)^:= Self.Handle;
• WM_COPYDATA value is set incorrectly, although msdn says so.

Can anyone suggest what could be wrong and how to solve the problem?

Answer 1

sizeof(longint) and Int32.MaxValue? sizeof in Delphi returns the size of the used memory under a variable? It's just that Int32.MaxValue is two billion kopecks.

Answer 2

Try using the standard System.IO.MemoryMappedFiles.MemoryMappedFile class , and just write this.Handle to the BinaryWriter from the example.
The WM_COPYDATA value is not used anywhere in the code, by the way.