C / C++ / MFC

Passing LPCSTR from C++ Dll to VB

7-Jan-08 4:23

hanlei0000000009 wrote:
"why does c==-96 but not equals 160?"

because -96 and 160 are quite different numbers.
Big Grin | :-D

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Re: int change to char

Eytukan7-Jan-08 6:58

Eytukan

7-Jan-08 6:58

OK,. what country just started work for the day ? The ASP.NET forum is flooded with retarded questions. -Christian Graus

Best wishes to Rexx[^]

Re: int change to char

Maxwell Chen7-Jan-08 7:16

Maxwell Chen

7-Jan-08 7:16

ROTFLMAO

Maxwell Chen

CrocodileBuck7-Jan-08 1:58

CrocodileBuck

7-Jan-08 1:58

Hi,

i'm trying to pass a LPCSTR from a C++ Dll to a VB Code.
I'm getting no Error Message but the String will not appear in the Msg Box of the VB code ! I'm really drivin Crazy with this. Confused | :confused:

Here are some lines of the code:
VB

<br />
Option Explicit<br />
<br />
Private Declare Function fnWin32DLL02 Lib "Win32DLL02.dll" () As Integer<br />
<br />
Private Sub Form_Load()<br />
    <br />
    Dim x As String<br />
    <br />
    x = Space$(3)<br />
    x = fnWin32DLL02()<br />
    MsgBox "X ist: " & x<br />
    <br />
End Sub<br />

Cpp:

<br />
WIN32DLL02_API LPCSTR fnWin32DLL02(void)<br />
{<br />
		LPCSTR s = "abc";<br />
	<br />
		return s;<br />
}<br />

Many Thx for your answers,
Best Regards
Croc

Matthew Faithfull7-Jan-08 2:23

Matthew Faithfull

7-Jan-08 2:23

Strings in VB are a little more involved underneath than strings in C++. Try changing the Dll end to return a BSTR allocated with SysAllocString or a related API. If BSTRs (BeeStings Smile | :)

) just seem way to awkward ATL provides the very useful CComBSTR class which deals with many of the painful bits for you. BSTRs have the length written into 2 bytes on the front of the string followed by the string which may or may not be NULL or even double NULL terminated.
This is what VB does for you when you use it's friendly string type.

Nothing is exactly what it seems but everything with seems can be unpicked.

image processing toolkits | batch image processing

C^hris L^osinger7-Jan-08 7:25

C^hris L^osinger

7-Jan-08 7:25

Matthew Faithfull wrote:
BeeStings

Beasters!

Maxwell Chen7-Jan-08 7:45

Maxwell Chen

7-Jan-08 7:45

Matthew Faithfull wrote:
BSTRs (BeeStings

Bastard ...

Maxwell Chen

CPallini7-Jan-08 2:53

7-Jan-08 2:53

AFAIK you also have to use __stdcall calling convention.
Does your WIN32DLL02_API already contain it?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

CrocodileBuck7-Jan-08 3:14

CrocodileBuck

7-Jan-08 3:14

Hi Pallini,

jap you are right __stdcall is in WIN32DLL02_API but i could not manage this, is it possible for you to insert the lines in the code ?
I know that is not a "rent a coder", but i have the worst prob with this Dll since ... !!!
When I use This Code I get an "a" not "abc" and i culd not pass a Strin parameter to the function fnWin32Dll02(void), when I try it(shure with a LPCSTR or a BSTR param. in the function interface) i get an Error, pleeeese help me it's horror !

<br />
WIN32DLL02_API BSTR fnWin32DLL02(void)<br />
{<br />
<br />
		BSTR s;<br />
	<br />
		 s = SysAllocString(L"abc");<br />
<br />
		return s;<br />
}<br />

<br />
Option Explicit<br />
<br />
Private Declare Function fnWin32DLL02 Lib "E:\WORKING\OMRON\GDT\EigeneDLL\Übergabe eines Strings aus C++ Dll\Win32DLL02.dll" () As String<br />
<br />
<br />
Private Sub Form_Load()<br />
    <br />
    Dim x As String<br />
    <br />
    x = Space$(6)<br />
    x = fnWin32DLL02()<br />
    MsgBox "X ist: " & x<br />
    <br />
End Sub<br />
<br />

Many thx hopefully and best regards
Croc

I got it!

CPallini7-Jan-08 11:12

7-Jan-08 11:12

I'm a tenacious guy... Eventually I was able to make some test using VB and VC++6.

The code:
DLL header

#ifdef DLLSIMPLE_EXPORTS
#define DLLSIMPLE_API __declspec(dllexport)
#else
#define DLLSIMPLE_API __declspec(dllimport)
#endif

#ifdef __cplusplus
extern "C"
{
#endif

DLLSIMPLE_API  BSTR __stdcall fnHello(void);
#ifdef __cplusplus
}
#endif

DLL source (.cpp)

#include "stdafx.h"
#include "oleauto.h"
#include "DLLSimple.h"

// DllMain stuff...

DLLSIMPLE_API BSTR __stdcall  fnHello(void)
{	
	LPCSTR pChar = "hello VB!"; 
	BSTR bstr = SysAllocStringByteLen(pChar, strlen(pChar));
	return bstr;
}

VB source

Private Declare Function fnHello Lib "DLLSimple.dll" Alias "_fnHello@0" () As String

Private Sub Form_Load()
  Dim s As String
  s = fnHello
  MsgBox s
End Sub

Hope that helps

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Chris Meech7-Jan-08 7:59

Chris Meech

7-Jan-08 7:59

What I usually do in these cases is 'force' my VB brethren to use strings and counters.

<br />
<br />
Public Declare Function fnWin32DLL02 lib "whatever.DLL" ( ByRef SomeString as String, ByVal SomeLength as Long ) As Long<br />
<br />
Dim  x  As  String<br />
DIM  y  As  Long<br />
Dim  z  As  Long<br />
<br />
x  =  Space$(3)<br />
y  =  3<br />
z  =  fnWin32DLL02(x,y)<br />

Then the C interface becomes

<br />
long __stdcall fnWin32DLL02(char** pbuffer, long nBufferCount)<br />

Just make sure you space fill the buffer up to nBufferCount.

Chris Meech
I am Canadian. [heard in a local bar]
Donate to help Conquer Cancer[^]

CrocodileBuck8-Jan-08 0:07

CrocodileBuck

8-Jan-08 0:07

Thx Pallini and Chis,

it works, but i had to change the ByRef to Byval Chris !

Thx a lot
Croc

Memory Table

Programm3r7-Jan-08 1:20

Programm3r

7-Jan-08 1:20

Hi all,

I would like to know whether there is a way that one can keep a table in memory, so that there is no need to read from a db table.

Thanks in advance
Regards,

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

Nishad S7-Jan-08 1:58

Nishad S

7-Jan-08 1:58

Is CMap useful?

- NS -
[ODBaseBtn]

Programm3r7-Jan-08 2:24

Programm3r

7-Jan-08 2:24

thanks for the response I'll have a look

Regards,

The only programmers that are better that C programmers are those who code in 1's and 0's Green Alien | [Alien]

Programm3r
My Blog: ^_^

toxcct7-Jan-08 3:10

toxcct

7-Jan-08 3:10

isn't what a CResultset made for ?

by the way, keep in mind that your database datas may be modified by another process (i consider the common case when the DB is remote, with several clients querying on it). so if one client stores its query result, without ever refreshing them by times, you may have not synchronized data.

[VisualCalc][Binary Guide][CommDialogs] | [Forums Guidelines]

CPallini7-Jan-08 9:09

7-Jan-08 9:09

toxcct wrote:
isn't what a CResultset made for ?

DataTables are made for. (Un)fortunately they belongs to the managed realm.
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Combo box issue

Chandrasekharan P7-Jan-08 1:02

7-Jan-08 1:02

I have 3 combo boxes in my application. and this 3 combo boxws indicate opening a folder and logging the data. the existing system is like whenever the appliaction is opened, it starts loggin in the data. i dont want to do that. now what i want to do is when i check one of the check box it should start loggin in in one folder and it has to be done during runtime. what can be done for this?

CPallini7-Jan-08 1:51

7-Jan-08 1:51

And what is the problem, aren't you able to handle check boxes events?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Chandrasekharan P7-Jan-08 21:42

7-Jan-08 21:42

i am sorry for not completing the query. i am initiating a socket. when i enable the socket a message gets passed to a folder. this is already there in the application. now i need to log this message whenever i need. for this i am using a check box. if i click the check box the message should get logged in. if i dont check the check box the message should not get logged in. and i should be able to do this when the socket is on. i need to know how can it be done. i hope the problem is clear now.

CPallini7-Jan-08 22:00

7-Jan-08 22:00

In fact the scenario is clear now. But I still don't know

(1) How the logging (and reading) is actually performed by the code (e.g. have you threads, what object manages logging, and so on)
(2) What is your difficulty.

Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Chandrasekharan P7-Jan-08 22:35

7-Jan-08 22:35

cool... its a button which helps to activate the socket and the same way to deactivate the socket. so when its activated and deacticated it will send a message. and its gets logged into a folder. i want to do it dynamically...

i am not being able to loggin the data to the folder.

CPallini7-Jan-08 22:54

7-Jan-08 22:54

I think you'll need to post some code.
Anyway, why don't you bind the logging message to the checkbox (removing it from the socket activation routine)?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

[my articles]

Chandrasekharan P7-Jan-08 23:16