Calling a Dynamic Link Library from Visual Basic, VB - assembler integration through a DLL

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sachin22

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Member No.: 1319
Joined: 9-June 05

Hello everybody,

I am still learning MASM32, I am trying to return a string in my .DLL but I get and "out of memory" error in Visual Basic.
The GetNewTempFile proc is causing problems for me.

Could you help me please?

Thank you.

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shoorick
Extremely Active Member Group: Admins Posts: 2301 Member No.: 160 Joined: 22-June 04	Hi! The aforementioned procedure works without any problems in the code you attached. I dont have Visual Basic, and never worked with it, so i can't help you more with this. Regards! Attached File ( Number of downloads: 24 ) Login or Register to download


swallon
New Member Group: Members Posts: 7 Member No.: 1120 Joined: 17-March 05	Visual Basic does not support pointers.


akyprian
Administrator Group: Admins Posts: 2307 Member No.: 1 Joined: 12-May 04	Pointers can be used in Visual Basic, but this is an advanced (and tricky) topic. I guess, this is not exactly what sachin22 asks... Try ByRef (not ByVal) when you make the call from Visual Basic. If you still have problems, upload a VERY small .dll WinAsm Studio project and a Visual Basic executable project, so that I can quickly help you solve the problem. Antonis

sachin22

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Group: Members
Posts: 5
Member No.: 1319
Joined: 9-June 05

Hi guys,

Thanks a lot for your response.
I was able to return a string by using SysAllocString to be used as:

CODE

dim x as string

x=asmReturnAString()

This works fine, as for passing by reference is concerned, I was only able to copy from parameter 1 to parameter2 as follows in MASM32:

CODE

asmStringByRef proc lpString:LPCTSTR,lpRetByRef:LPCTSTR

; Proc works if lpString is declared as LPSTR/LPCTSTR/DWORD and
; lpRetByRef declared as ptr dword/dword/LPSTR,even LPCTSTR

mov esi, dword ptr [lpString]
mov edi, dword ptr [lpRetByRef]

@label:

mov al, [esi]
inc esi
mov byte ptr [edi],al
inc edi
cmp al,0
jne @label

Ret

asmStringByRef EndP

...in Visual Basic:

CODE

Private Declare Sub asmStringByRef Lib "C:\asmICLogix.dll" (sVal As String, sRef As String) ' As Long

'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' asmStringByRef test results
' p1 -> p2: byRef->ByRef
'
' p1 : DWORD/LPSTR/LPCTSTR
' p2: ptr dword/dword/LPSTR,even LPCTSTR
'
' Quotes accepted on p1 for asmStringByRef
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Private Sub Test ()

Dim s As String, z As String

z = "ICLrpt1.tmp"
Call asmStringByRef(z, s)
MsgBox s

End Sub

My asmGetNewTempFile proc does not return the string in parameter strNewFileName:

CODE

asmGetNewTempFile proc strPrefix :DWORD, strNewFileName:BYTE

; strPrefix was originally LPCTSTR, works even if DWORD
; param1:DWORD, param2:PTR DWORD works, param1:LPSTR,param2:PTR DWORD works

;; pass LPCTSTR directly

local strFullPath[256]:byte
invoke GetTempPath, 256, addr strFullPath; contains path only
invoke lstrcat, addr strFullPath,strPrefix

invoke CreateFile, addr strFullPath, GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ or FILE_SHARE_WRITE,\
NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL or FILE_FLAG_DELETE_ON_CLOSE, NULL

lea eax,strFullPath
mov edx,0

@label:

mov al,byte ptr [strFullPath+edx]
mov byte ptr [strNewFileName+edx],al
inc edx
cmp al,0
jne @label
ret

asmGetNewTempFile EndP

I would like to know what changes are needed to support byVal in vb and how to make strNewFileName return a string by reference.

I am still learning, so your help will be much appreciated, even on the other procs contained in the project.

Kindly test the dll for me, I hope it is not heavily bugged.
Thanks a lot for your help, keep the good job going.

Sachin.

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