Thanks!!! Re: call c/c++ function from VB

[Chris]

Mark

thanks for your help!!
much appreciated, but I was receiving inconsistent results,
probably more to do with the changes I made to the code you supplied me!

anyway I cut my losses and wrote another small C function called
format_postcode_A that calls the original function, ie

int __stdcall format_postcode_A(char * the_post_code,
char * post_code_two, char * the_post_code_three,
char * area, char * dist, char * sect, char * unit)

so that I can pass strings individually! makes more sense this way.
this now works and I am a happy chap!

thanks for the time you put in, you have increased my understanding of
VB a little bit more!!!!

regards

chris


"Mark Alexander Bertenshaw" <mark.bertenshaw@virgin.net> wrote:
>"Chris" <vb.@127.0.0.1> wrote in message news:3d51042c$1@10.1.10.29...
>>
>> Hi all,
>> I know this is not really a win32 question, but you are the
>> group who will be most likely able to answer the question for me!!!
>>
>> How would I declare and call the following C/c++ function ithin VB,
>> the function lives in one of my own dll's and has only needed to be called
>> from C but there is now a need for it to be called from VB.
>>
>> int __stdcall format_postcode(char the_strings[7][20])
>>
>> As a C/c++ programmer, and only a novice VB programmer this is something
>> that is new to me.
>> any help would be much appreciated.
>>
>
>Try the following. It is not very efficient, since 2D C byte arrays are
not
>compatible with 1D VB string arrays. Well, that's what I assume that you
>want to do.
>
>----------------------------------------------------------------------------
>--------------------------------------
>
>Private Sub Function CopyMemory Lib "Kernel32.dll" Alias "RtlMoveMemory"
( _
> ByRef dest As Any, _
> ByRef src As Any, _
> ByVal copied As Long _
>)
>
>Private Declare Function FormatPostcode Lib "<yourDLL.dll>" Alias
>"format_postcode" ( _
> ByRef the_strings As Byte _
>) As Long
>
>Sub Test(ByRef asStrings())
>' Actually, this could be very wrong, since I am not sure which dimension
is
>referenced first.
>' If it is not this way, then reverse the order of the dimensions, and all
>code that relies on it.
>' Actually ... might be more complicated .. oh well.
>Dim abytStrings(0 To 6, 0 To 19) As Byte
>Dim lIndex As Long
>Dim sTemp As String
>
> ' Convert the 1D VB string array into a 2D array of bytes.
> ' Note the explicit Unicode -> ANSI translation.
> For lIndex = 0 To 6
> sTemp = StrConv(asStrings(lIndex), vbFromUnicode)
> CopyMemory abytStrings(lIndex, 0), ByVal StrPtr(sTemp), LenB(sTemp)
> Next lIndex
>
> ' Send a pointer to the first byte of the 2D array.
> FormatPostcode abytString(0, 0)
>
> ' Copy byte array back into string array.
> ' Note the explicit ANSI -> Unicode translation.
> For lIndex = 0 To 6
> sTemp = Space$(10) ' Half of 20
> CopyMemory ByVal StrPtr(sTemp), abytStrings(lIndex, 0), LenB(sTemp)
> asStrings(lIndex) = StrConv(sTemp, vbUnicode)
> Next lIndex
>
>End Sub
>
>----------------------------------------------------------------------------
>-----------------------------------------
>
>HTH
>
>--
>Mark Alexander Bertenshaw
>Programmer/Analyst
>Chordiant Software, Inc.
>Brentford
>UK
>
>

[Mark Alexander Bertenshaw]

"Chris" <vb.@127.0.0.1> wrote in message news:3d525e19$1@10.1.10.29...
>
> Mark
>
> thanks for your help!!
> much appreciated, but I was receiving inconsistent results,
> probably more to do with the changes I made to the code you supplied me!
>
> anyway I cut my losses and wrote another small C function called
> format_postcode_A that calls the original function, ie
>
> int __stdcall format_postcode_A(char * the_post_code,
> char * post_code_two, char * the_post_code_three,
> char * area, char * dist, char * sect, char * unit)
>
> so that I can pass strings individually! makes more sense this way.
> this now works and I am a happy chap!
>
> thanks for the time you put in, you have increased my understanding of
> VB a little bit more!!!!

Chris -

That's good to hear. But I wasn't really expecting it to work straight
away - it was more of theoretical thing. As I said, I think that VB
multidimensional arrays are implemented in a different way to C
multidimensional arrays.
Not all this is trial and error. It's a combination of MSDN Library, and a
number of very good VB books. I suppose I really ought to mention "Advanced
Visual Basic 6" by Matthew Curland ... again. But it is truly the best VB
book for programmers who are not scared to get into the guts of VB and COM.
The chapter on Arrays and the chapter on Strings is worth the price alone.

--
Mark Alexander Bertenshaw
Programmer/Analyst
Chordiant Software, Inc.
Brentford
UK