[DUG] Re: DLL's

[Ross Levis]

Nevermind, I think I've worked it out!  I was doing it backwards.  I should be defining a GetMyNumber function and then assigning the address of my function to the DLL GetNumber function, so the DLL knows where my function is located.

Cheers,
Ross.
  ----- Original Message ----- 
  From: Ross Levis 
  To: NZ Borland Developers Group - Delphi List 
  Sent: Saturday, July 02, 2005 12:58 PM
  Subject: DLL's


  I have a DLL which defines a structure for passing information 2 ways.
  I need to define some functions and procedures that will be called from a 3rd party DLL that I'm loading.  I've successfully loaded the DLL and can call the functions & procedures in the DLL, but I'm not sure how to set up the reverse situation where the DLL requests information from my program.

  Here is an example DLL structure and what I've done so far.

  type
    PSomeDLL = ^TSomeDLL;
    TSomeDLL = record
      Init : procedure; cdecl;
      Quit : procedure; cdecl;
      GetNumber : function(FileName:PChar):Integer; cdecl;
    end;

    TDLLStruct = function: PSomeDLL; cdecl;
  ....
  var
    DLLStruct: TDLLStruct;  
  begin
    @DLLStruct := GetProcAddress(...
    DLLStruct.Init;
    ...

  This is working and I can successfully call DLLStruct.Init and DLLStruct.Quit from my program, but GetNumber is actually called by the DLL, so I need to supply the result of the function.  How do I go about that?

  I thought I would have to do something like this:

  type
    TGenNumber = function(FileName:PChar):Integer; cdecl;

  var
    GetGenNumber: TGenNumber;
  ...
  GetGenNumber := DLLStruct.GetNumber;
  ...
  function GetGenNumber(FileName:PChar):Integer;
    Result := 1; // something
  end;

  This compiles but the function GetGenNumber above is not compiled into my executable because it doesn't think it's being called.  It isn't being called within my program, the DLL will be calling it, but the compiler doesn't know that.  What as I missing?

  Thanks,
  Ross.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://ns3.123.co.nz/pipermail/delphi/attachments/20050702/4bf57580/attachment.html