Pascal DLL that I can use with VBA

Delphi 4 (but I want to write them in my favorite text editor) and pascal compiler from freepascal.org.

Thanks,
TNC

Here's a simple .dll source (from borland pascal help):


library MinMax;

function min (x, y : integer) : integer; export;
begin
if x < y then min := x else min := y;
end;

function max (x, y : integer) : integer; export;
begin
if x > y then max := x else max := y;
end;

exports
  min index 1,
  max index 2;

begin
end.

Thanks ZhaawZ,

     The only problem with that example is that I cannot reference it from VBA (nor VB even).  Do you have an example that works with Win 32?

Thanks again,
TNC

Hmm.. Haven't work with dlls from VB (VBA). Haven't work with VB at all for a long time :) I can get only some examples how to work with dlls in delphi/pascal...

Btw, that 'export' clause - it can be also look like this:

exports
  min name 'min_function',
  max name 'max';

or

exports
  min index 1 name 'min_function',
  max index 2 name 'max';


It should depend on the way you want to call functions from these dlls

Did you solve the problem?

No ZhaawZ,

     That's all well and good if I want to call the DLL from another pascal program, but that dosen't make the library a valid win32 dll.  That's what I'd like to accomplish.

Thanks,
TNC

Pascal (at least - Delphi) makes a valid library file.
Here's an example of a library file in pascal and a source from VBA (haven't coded in VB for a long time so there can be some imperfections, but it works as it should).
Notice that there's 'smallint' in library file, but 'integer' in vba source. That's because integer in vba is 16bit value, but in delphi it is 32bit value, so I used smallint (this is 16bit value in delphi).
Hope this will help.

----- ----- ----- ----- ----- ----- Project2.dpr:
library minmax;

function min (n1, n2 : smallint) : smallint; stdcall; /// didn't work without 'stdcall'
begin
if n1 < n2 then result := n1 else result := n2;
end;

function max (n1, n2 : smallint) : smallint; stdcall;
begin
if n1 > n2 then result := n1 else result := n2;
end;

exports
  min name 'func1',
  max name 'func2';

begin
end.


----- ----- ----- ----- ----- ----- VBA source (tested in MS Word 2000 VB Editor):
Private Declare Function min_f Lib "C:\Program Files\Borland\Delphi6\Bin\Project2.dll" Alias "func1" (ByVal n1 As Integer, ByVal n2 As Integer) As Integer
Private Declare Function max_f Lib "C:\Program Files\Borland\Delphi6\Bin\Project2.dll" Alias "func2" (ByVal n1 As Integer, ByVal n2 As Integer) As Integer

Private Sub CommandButton1_Click()
Dim n1 As Integer
Dim n2 As Integer
Dim n As Integer
'On Error Resume Next
n1 = CInt(TextBox1.Text)
n2 = CInt(TextBox2.Text)
n = min_f(n1, n2)
MsgBox n
End Sub

Private Sub CommandButton2_Click()
Dim n1 As Integer
Dim n2 As Integer
Dim n As Integer
On Error Resume Next
n1 = CInt(TextBox1.Text)
n2 = CInt(TextBox2.Text)
n = max_f(n1, n2)
MsgBox n
End Sub

ZhaawZ,

     I figured out how to return integers, bytes, etc., but I can't return strings.  Do you know where I can find a vbapi unit for delphi?  Do you know another way around the string quandry?

Thanks,
TNC

Now comes a problem. As I have heard, it's unadvised to use pascal strings in dll - use PChar (null-terminated string; it is a sequence of chars followed by #0) or ShortString instead of String.
I'll try to write some example for you.

Here's an example of passing string as a parameter in function/procedure.


------ ------ ------ VBA source:
Private Declare Function example Lib "C:\Program Files\Borland\Delphi6\Bin\Project1.dll" (ByRef s As String) As Long

Private Sub CommandButton1_Click()
MsgBox example("one")
MsgBox example("two")
End Sub

------ ------ ------ Delphi source:
library sample;

uses
  windows;

function example(var s : pchar) : integer; stdcall;
begin
if s = 'one' then result := 1 else
if s = 'two' then result := 2 else
result := 0;
end;

exports
  example;

begin
end.




Tryin' to find/make any example of returning strings...

Hmm... Have you worked with pointers in VB?

Is this what you need?

I'm going to check that out this morning ZhaawZ.  Where did you find that code?

Thanks,
TNC

I didn't find that code, I just wrote it :)

ZhaawZ,

     Thanks for your help so far.  That seems to work until I try to convert an integer to a string and return it.  Here's my test code:

library sixOneThree;

  uses
    Windows, SysUtils;

  function tryInteger(var test:integer):pchar; export; stdcall;
   var
    testString:string;
    testLen:integer;
    testStringP:pchar;

   begin
    str(test, testString);
    testStringP := pchar(testString);
    testLen := strLen(testStringP);
    getMem(result, testLen);
    result := testStringP;
   end;

  exports
    tryInteger index 1;

end.

What gives?

Thanks,
TNC

Actually,

      I fixed that problem.  What I've discovered is that for some reason, I have to pass the first variable byref and each other variable by val.  Why do you suppose that is?

TNC

Okay,

    Now, the only functinal problem that I have is that the strings that are returned are too long.  For some reason, it adds about 8 chars to the end.  Sometimes, there is junk in those chars.  The same funciton doesn't do that if I run it in console.  It must be on the VB side.  Any ideas on how to fix that?

Thanks again,
TNC

//from your source
   var
    testString:string;
    testLen:integer;
    testStringP:pchar;

   begin
    str(test, testString);
    testStringP := pchar(testString);
    testLen := strLen(testStringP);
    getMem(result, testLen);
    result := testStringP;
   end;


There's no need to use getMem when you assign to a value some pchar(string) or a any variable of type PChar (as it is in this case).
Brrr... Actualy I'm totally confused from all of this... Now it works also without GetMem...

A very short example of converting an integer to a string:

----
Private Declare Function example _
    Lib "C:\Program Files\Borland\Delphi6\Bin\Project1.dll" _
    Alias "tryInteger" _
    (ByVal n As Long) _
    As String

Private Sub CommandButton1_Click()
MsgBox example(987)
End Sub


-----
library sixOneThree;

uses
  sysutils;

function tryInteger (n : integer) : pchar; stdcall; export;
begin
result := pchar(format('%d', [n]));
end;

exports
  tryInteger;

end.

Didn't actually understand that problem you wrote some minutes ago.. Could you give an example of vba and dll source so I'd be able to see the problem?