Visual Basic, Passing Multi-Dimension Arrays from VB to DLL

Craig
#1 / 5

Passing Multi-Dimension Arrays from VB to DLL

Probably been asked before but...

I'm coding an app in VB 6 with all the math intensive
stuff handled by a C++ Builder 4 DLL The problem is I
can't figure out how to pass multi dimension arrays by
reference between the two.

Single dimension arrays are no problem -

Declare function foo lib "mylib.dll" (byref gk as single) as long
Dim gk(4) as single
i = foo( gk(0) )

long __stdcall foo ( float *gk )
{ // do calcs with it
gk[1] += 10;
etc...

So how do you go about passing a Dim gk(4,4) to it ?

I know the solution's gonna be something simple...
like me ;-)

TIA,

Mon, 19 Jul 2004 03:07:36 GMT

Neila Nes
#2 / 5

Passing Multi-Dimension Arrays from VB to DLL

Hi Craig,
This should get the juices going...
I usually dim starting at 0 but using 1 in this case is easier to
illustrate the memory mapping of one_dim to multi_dim arrays.
HTH, Neila

Option Explicit
Private Declare Sub CopyMemory _
Lib "kernel32" _
Alias "RtlMoveMemory" _
(Destination As Any, _
Source As Any, _
ByVal Length As Long)

Private Sub Private Sub ooo________ooo________ooo()
Dim MDArray() As Double
Dim OneDArray() As Double
Dim i As Long
Dim j As Long
Dim k As Long
Dim lCopySize As Long
ReDim MDArray(1 To 3, 1 To 3, 1 To 3) '27 elements
ReDim OneDArray(1 To 27)
For i = 1 To 3
For j = 1 To 3
For k = 1 To 3
MDArray(i, j, k) = i * 100 + j * 10 + k
Next 'k
Next 'j
Next 'i
lCopySize = 27 * LenB(OneDArray(0))
Call CopyMemory(OneDArray(1), MDArray(1, 1, 1), ByVal lCopySize)
For i = 1 To 27
Debug.Print OneDArray(i)
Next
End Sub
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Quote:

> Probably been asked before but...

> I'm coding an app in VB 6 with all the math intensive
> stuff handled by a C++ Builder 4 DLL The problem is I
> can't figure out how to pass multi dimension arrays by
> reference between the two.

> Single dimension arrays are no problem -

> Declare function foo lib "mylib.dll" (byref gk as single) as long
> Dim gk(4) as single
> i = foo( gk(0) )

> long __stdcall foo ( float *gk )
> { // do calcs with it
> gk[1] += 10;
> etc...

> So how do you go about passing a Dim gk(4,4) to it ?

> I know the solution's gonna be something simple...
> like me ;-)

> TIA,

Mon, 19 Jul 2004 09:49:37 GMT

Brad Pan
#3 / 5

Passing Multi-Dimension Arrays from VB to DLL

As you have found out VB and VC have opposite array ordering, one is
Row, Column and the other is Column, Row. When I passed a 2
dimensional routine I spent quite a few days working on a routine to
get them back in the same order, and I ended up padding the array out
with each dimension the same 10X10 to get it to work right.

Instead of spending days working this out, I would pass the array one
dimension at a time and just do multiple calls. You may also want to
check out SafeArrays which "I think" may support this better.

Quote:

> Hi Craig,
> This should get the juices going...
> I usually dim starting at 0 but using 1 in this case is easier to
> illustrate the memory mapping of one_dim to multi_dim arrays.
> HTH, Neila

> Option Explicit
> Private Declare Sub CopyMemory _
> Lib "kernel32" _
> Alias "RtlMoveMemory" _
> (Destination As Any, _
> Source As Any, _
> ByVal Length As Long)

> Private Sub Private Sub ooo________ooo________ooo()
> Dim MDArray() As Double
> Dim OneDArray() As Double
> Dim i As Long
> Dim j As Long
> Dim k As Long
> Dim lCopySize As Long
> ReDim MDArray(1 To 3, 1 To 3, 1 To 3) '27 elements
> ReDim OneDArray(1 To 27)
> For i = 1 To 3
> For j = 1 To 3
> For k = 1 To 3
> MDArray(i, j, k) = i * 100 + j * 10 + k
> Next 'k
> Next 'j
> Next 'i
> lCopySize = 27 * LenB(OneDArray(0))
> Call CopyMemory(OneDArray(1), MDArray(1, 1, 1), ByVal lCopySize)
> For i = 1 To 27
> Debug.Print OneDArray(i)
> Next
> End Sub
> 111
> 211
> 311
> 121
> 221
> 321
> 131
> 231
> 331
> 112
> 212
> 312
> 122
> 222
> 322
> 132
> 232
> 332
> 113
> 213
> 313
> 123
> 223
> 323
> 133
> 233
> 333

> > Probably been asked before but...

> > I'm coding an app in VB 6 with all the math intensive
> > stuff handled by a C++ Builder 4 DLL The problem is I
> > can't figure out how to pass multi dimension arrays by
> > reference between the two.

> > Single dimension arrays are no problem -

> > Declare function foo lib "mylib.dll" (byref gk as single) as long
> > Dim gk(4) as single
> > i = foo( gk(0) )

> > long __stdcall foo ( float *gk )
> > { // do calcs with it
> > gk[1] += 10;
> > etc...

> > So how do you go about passing a Dim gk(4,4) to it ?

> > I know the solution's gonna be something simple...
> > like me ;-)

> > TIA,

Mon, 19 Jul 2004 22:32:26 GMT

Craig
#4 / 5

Passing Multi-Dimension Arrays from VB to DLL

Quote:

> This should get the juices going...
> I usually dim starting at 0 but using 1 in this case is easier to
> illustrate the memory mapping of one_dim to multi_dim arrays.
> HTH, Neila
> Option Explicit
> Private Declare Sub CopyMemory _
> Lib "kernel32" _
> Alias "RtlMoveMemory" _

<snip>

Hi, I managed to convert some of my code to use this
technique. Unfortunately, there's just too much overhead and
the array indexing slows it up by quite a bit, it looks as tho'
I'm gonna have to seriously re-think the code :-(.

Anyway, many thanks for the reply, much appreciated :)

Wed, 21 Jul 2004 03:32:39 GMT

J Fren
#5 / 5

Passing Multi-Dimension Arrays from VB to DLL

On Fri, 1 Feb 2002 19:32:39 -0000, "Craig W"
_

Quote:

><snip>

>Hi, I managed to convert some of my code to use this
>technique. Unfortunately, there's just too much overhead and
>the array indexing slows it up by quite a bit, it looks as tho'
>I'm gonna have to seriously re-think the code :-(.

>Anyway, many thanks for the reply, much appreciated :)

I assume that you are using the CPP DLL for speed, and that the VB bit
is, well not so speed critical.

An array is just a block of memory - you could 'front' your VB Array
with properties that access a block of memory in the CPP format.

That way you appear to have a VB array - in VB format

If you pre-calculate the offsets and hold them in an array of Longs
then there should be little overhead at the VB end.

Of course this pre-supposes that you make minor changes to the VB
Array and repeatedly call the CPP DLL to recalculate.

An even better method would be, assuming you have the source of the
DLL, to 'embed' the VB array in the CPP DLL - or maybe a 'driver' DLL

Wed, 21 Jul 2004 17:04:53 GMT