Passing an Excel Range object to C++ DLL

  • Thread starter Thread starter Martin
  • Start date Start date
M

Martin

Hello,
I want to pass an excel selection to a C++ dll in order to get a result
an display it in a cell.
I could allready do it by copying the content of the Range object into
a Double array that is passed by reference to the dll.
Now I would like to avoid the copy, and pass the Range object by
reference to the C++ dll.

Is there a corresponding C++ type (and associated utility functions)
for maniuplating the Range object?

Any link to detailed documentation/example would be appreciated (I do
know really few concerning COM).

Thanks in advance
Martin
 
Martin,
You can call Windows API functions directly from the worksheet, so make your
VBA Declare statement something similar. So it would be a standard DLL, not
ActiveX.
Need to be able to handle Unicode, or at least calling the APIs this way
needs the W version not the A version.

NickHK
 
Hello Nick,
Thanks for replying! I actually allready have the VBA functions that
call the C++. I'm binding C++ to VBA with the following statment:

Private Declare Sub alterMatrix Lib "TheDLL.dll" Alias
"_alter_matrix@12" (ByRef dTab As Double, ByVal lines As Long, ByVal
col As Long)

And my macro is using it this way:

Private Function ModifyDataset(ByRef theCells As Range)
Dim dataset() As Double

' Get range dimension
nCol = theCells.Columns.Count
nRow = theCells.Rows.Count

' Transform the range object into a dataset
ReDim dataset(nRow - 1, nCol - 1) ' ?????????????????
For r = 0 To nRow - 1
For c = 0 To nCol - 1
' Check datatype
cellVal = theCells(r + 1, c + 1).Value
Select Case VarType(cellVal)
Case Is = vbInteger
dataset(r, c) = CDbl(cellVal)
Case Is = vbLong
dataset(r, c) = CDbl(cellVal)
Case Is = vbSingle
dataset(r, c) = CDbl(cellVal)
Case Is = vbDouble
dataset(r, c) = CDbl(cellVal)
Case Else
MsgBox "The field " & r + 1 & "," & c + 1 & " contains
non numeric data: " & cellVal
dataset(r, c) = 0
End Select
Next
Next

' Call the DLL
alterMatrix dataset(0, 0), nRow, nCol

' Get the data back
For r = 0 To nRow - 1
For c = 0 To nCol - 1
theCells(r + 1, c + 1).Value = dataset(r, c)
Next
Next

End Function

As you may notice, I copy the Range object content (the selected cells)
into an array of double. It works perfectly for my C lib that simply
consider it as a double*. I also made tests that allow to pass strings,
integers to my dll.

I now would like to pass the RANGE object, and read it in the C dll in
order to avoid copying data...

Any advice? I'm trying to read some documentation concerning OLE, but
it's lot of readings for a single object information!

Martin
 
Martin,
I don't use C++, but..
I assume your DLL does not have a reference to the Excel library. Hence it
has no idea what a Range object and no way to access the values.
So it would seem easiest to pass an array of values, either as you are doing
or a variant (Set varArray=theCells ) if your DLL can accept that.

However, what happens if you pass a range to the DLL that is expecting a
variant or an array ? Do you get automatic conversion of the range to an
array of value ?

But if you are going to check for valid numeric data in VBA, before passing
to the DLL, do you need to change it anyway ?

NickHK
 
NickHK said:
Martin,
I don't use C++, but..
I assume your DLL does not have a reference to the Excel library. Hence it
has no idea what a Range object and no way to access the values.
So it would seem easiest to pass an array of values, either as you are doing
or a variant (Set varArray=theCells ) if your DLL can accept that.
Click to expand...

I know it's easier, since this works :) My goal is to minimize COPY of
data. I thus would like to know which Lib, functions, and object I
should use to directly control the Range content.
However, what happens if you pass a range to the DLL that is expecting a
variant or an array ? Do you get automatic conversion of the range to an
array of value ?
Click to expand...

There are no automatic stuffs with c++ :)
But if you are going to check for valid numeric data in VBA, before passing
to the DLL, do you need to change it anyway ?
Click to expand...

Don't get what you mean!? If there are non numeric values, I display an
error message before calling the DLL.
 
Martin,
From my limited knowledge, it seems that you DLL needs reference to Excel,
so then passing a range would not be a problem.
But I thought you were trying to avoid that.

NickHK
 
The easiest way to do this is to use RapidXLL_NET. You can then write
native C / C++ library automatically interface it with both Excel and
..NET with a one liner.

This tool uses the Excel C/C++ API. It is very fast and works around a
union object called an XLOPPER. The original api was created for Excel
95 and has been upgraded a couple of times (newest update for 2007) but
has ALWAYS remained backward compatible. You can look for Excel SDK or
Excel 95 Framework.

Try it free at http://www.RapidXLL.net

Sincerely,

The RapidXLL Team
 
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