Visual Basic - Calling DLL in VB6

Author

Calling DLL in VB6

NEK

2004-03-29, 9:31 pm

Dear all...

I have a question about calling a DLL (which should be developed by VC) in
VB6.

The function call from the DLL like this:

int WINAPI testReadData( const char *IpAddress, unsigned char Flag, const
unsigned char *StartRecord, unsigned int *NoOfRecord, unsigned char
*RecordData);

Then, I try to declare the function call in VB6 like the following, except,
I have no idea on those parameters.

Private Declare Function testReadData Lib "abc.dll" ( ???? ) As Long

Kindly please help!!!

Million thanks.

Ayaz Ahmed

2004-03-30, 1:30 am

Hello,

all you add your Dll in your references and call function and procedure
as well.

Thanks,

Warm Regards,

Ayaz Ahmed
Software Engineer & Web Developer
Creative Chaos (Pvt.) Ltd.
"Managing Your Digital Risk"
http://www.csquareonline.com
Karachi, Pakistan
Mobile +92 300 2280950
Office +92 21 455 2414

*** Sent via Developersdex http://www.developersdex.com ***
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NEK

2004-03-30, 2:30 am

thanks for reply

in fact, i can declare and call the function (i mean, the function can be
found in the DLL without error)
however, i have no idea on the data type or what variable should be passed
as parameters.

such as const char* in C lanuage, what should I implement a compatible
variable to pass to the DLL function call as "const char*" in VB?

thanks again.

"Ayaz Ahmed" <ayaz@csquareonline.com> wrote in message
news:udH6nfhFEHA.1272@TK2MSFTNGP12.phx.gbl...
> Hello,
>
> all you add your Dll in your references and call function and procedure
> as well.
>
> Thanks,
>
>
> Warm Regards,
>
> Ayaz Ahmed
> Software Engineer & Web Developer
> Creative Chaos (Pvt.) Ltd.
> "Managing Your Digital Risk"
> http://www.csquareonline.com
> Karachi, Pakistan
> Mobile +92 300 2280950
> Office +92 21 455 2414
>
> *** Sent via Developersdex http://www.developersdex.com ***
> Don't just participate in USENET...get rewarded for it!

J French

2004-03-30, 5:30 am

On Tue, 30 Mar 2004 14:23:20 +0800, "NEK" <nek> wrote:

>thanks for reply
>
>in fact, i can declare and call the function (i mean, the function can be
>found in the DLL without error)
>however, i have no idea on the data type or what variable should be passed
>as parameters.
>
>such as const char* in C lanuage, what should I implement a compatible
>variable to pass to the DLL function call as "const char*" in VB?

I'm afraid Ayaz Ahmed thought you were building an ActiveX DLL
- which you obviously are not

A 'C' programmer will probably pop up soon, but this should start you
off.

const char*
is a 4 byte pointer on the stack that points to a buffer of bytes

In VB that is: TheCall( ByVal S As String,

int WINAPI testReadData(
const char *IpAddress,
unsigned char Flag, ByRef B As Byte ??
const unsigned char *StartRecord,
unsigned int *NoOfRecord, ByRef N As Long
unsigned char* RecordData ByRef S As String

I am not sure about 'ByRef S As String'
That puts a 4 byte pointer on the stack that points to another 4 byte
pointer containing the address of a buffer

You need to make sure that all buffers are pre-formatted when they are
sent to the DLL
- also you must not change their length or move them in the DLL

Realistically the last parameter should be:
Const unsigned char* RecordData

I am also not sure about this,
unsigned char Flag,

Should it not be a Const ?

NEK

2004-03-30, 5:30 am

Thanks J French.

You are right that the DLL is not an ActiveX one and which I cannot put any
modification on it.

Actually, I don't familiar with the C language and just browsing and finding
and trying any solution.
So far, still can't access the function call with success. HEADACHE!

again, thanks all the help here ;)

"J French" <erewhon@nowhere.com> wrote in message
news:4069348f.87317999@news.btclick.com...
> On Tue, 30 Mar 2004 14:23:20 +0800, "NEK" <nek> wrote:
>
passed[color=darkred]
>
> I'm afraid Ayaz Ahmed thought you were building an ActiveX DLL
> - which you obviously are not
>
> A 'C' programmer will probably pop up soon, but this should start you
> off.
>
> const char*
> is a 4 byte pointer on the stack that points to a buffer of bytes
>
> In VB that is: TheCall( ByVal S As String,
>
> int WINAPI testReadData(
> const char *IpAddress,
> unsigned char Flag, ByRef B As Byte ??
> const unsigned char *StartRecord,
> unsigned int *NoOfRecord, ByRef N As Long
> unsigned char* RecordData ByRef S As String
>
> I am not sure about 'ByRef S As String'
> That puts a 4 byte pointer on the stack that points to another 4 byte
> pointer containing the address of a buffer
>
> You need to make sure that all buffers are pre-formatted when they are
> sent to the DLL
> - also you must not change their length or move them in the DLL
>
> Realistically the last parameter should be:
> Const unsigned char* RecordData
>
> I am also not sure about this,
> unsigned char Flag,
>
> Should it not be a Const ?
>
>

Bob O`Bob

2004-03-30, 1:30 pm

NEK wrote:
>
> You are right that the DLL is not an ActiveX one and which I cannot put any
> modification on it.
>
> Actually, I don't familiar with the C language and just browsing and finding
> and trying any solution.
> So far, still can't access the function call with success. HEADACHE!

There is, unfortunately, a significant chance that you never will.

<http://www.google.com/groups?as_q=s...oft.public.vb.*>

Bob
--

J French

2004-03-31, 5:30 am

On Tue, 30 Mar 2004 09:13:28 -0800, Bob O`Bob
<filterbob@yahoogroups.com> wrote:

>NEK wrote:
>
>There is, unfortunately, a significant chance that you never will.
>
><http://www.google.com/groups?as_q=s...oft.public.vb.*>

He is declaring it as WINAPI - is that not an alias for StdCall ?

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