Help: "ByRef argument type mismatch"

[altf4]

Ok When I try to test my code here I get a

Compile error:
ByRef argument type mismatch


Here is the code:

Private Type ANSI_STRING
       Length           As Long
       MaximumLength    As Long
       Buffer           As Long
End Type

Private Type UNICODE_STRING
       Length           As Long
       MaximumLength    As Long
       Buffer           As Long
End Type

Private Declare Function RtlAnsiStringToUnicodeString Lib "ntdll.dll" (DestinationString As UNICODE_STRING, SourceString As ANSI_STRING, ByVal AllocateDestinationString As Boolean) As Long

'_____________________________________________________________

Private Sub Command1_Click()

    Dim UString     As UNICODE_STRING
    Dim AString     As ANSI_STRING
    Dim sKeyPath    As String
   
    sKeyPath = "\Registry\Machine\SOFTWARE"

    'Initialize ANSI_STRING:
    AString.Buffer = StrPtr(sKeyPath)
    AString.Length = LenB(sKeyPath)
    AString.MaximumLength = LenB(AString.Buffer)
    
    Dim pMem As Long: pMem = VarPtr(AString)    'get pointer of ANSI_STRING
    
    'Convert ANSI_STRING to UNICODE_STRING:
    'lStatus = RtlAnsiStringToUnicodeString(UString, ByVal VarPtr(AString), False)      'not work (ByRef Mismatch)
    lStatus = RtlAnsiStringToUnicodeString(UString, pMem, False)                        'not work (ByRef Mismatch)
    
    'Return Status:
        MsgBox GetSysMsg(lStatus)

End Sub

Note: GetSysMsg is a custom function in a module to return an status string based on any API's Return Value (Works for both STATUS and NTSTATUS)


Ok so here is the problem:
When ever I try to perform this, I get an error saying:

Compile error:
ByRef argument type mismatch

and it highlights pMem. Well I am a bit confused here to why it is saying this. So I attempted to pass it ByVal and it then says:

Compile error:
User-defined type may not be passed ByVal

so how am I supposed to pass this pointer to the API ??? I mean you would just think "Oh.. pass the structure not the pointer" in which it will execute then, but when it does, it will give a return status of "Invalid Pointer".

The API wants the pointer, I just need to know how to give it to it without VB giving an error.

Thanks for your help.



Here are the links to MSDN for the API and Structures:

RtlAnsiStringToUnicodeString Function:
http://msdn2.microsoft.com/en-us/library/ms648413.aspx

UNICODE_STRING:
http://msdn2.microsoft.com/en-us/library/aa491546.aspx

ANSI_STRING:
http://msdn2.microsoft.com/en-us/library/aa492030.aspx

[minor28]

you need to initiate the string with RtlInitString.

This is an assembler snippet to create a process

;Initilize and count the string. Store in pEXEansi string structure
invoke RtlInitString,addr pEXEansi,addr szEXE
;Convert the string to a unicode string and count. Store in pEXEuni string structure
invoke RtlAnsiStringToUnicodeString,addr pEXEuni,addr pEXEansi,TRUE 
;Convert full path to a unicode string. Stor in dospath
invoke RtlDosPathNameToNtPathName_U,pEXEuni.buffer,addr dospath,0,addr ntpath
invoke RtlCreateProcessParameters,addr ProcPar,addr dospath,0,0,0,0,0,0,0,0

where szEXE is the ansistring and pEXEansi is the string structure for ansi and pEXEuni for unicode. You better leave VB and goto assembler if you are going to mess with ntdll.dll

[altf4]

you need to initiate the string with RtlInitString.

This is an assembler snippet to create a process

;Initilize and count the string. Store in pEXEansi string structure
invoke RtlInitString,addr pEXEansi,addr szEXE
;Convert the string to a unicode string and count. Store in pEXEuni string structure
invoke RtlAnsiStringToUnicodeString,addr pEXEuni,addr pEXEansi,TRUE 
;Convert full path to a unicode string. Stor in dospath
invoke RtlDosPathNameToNtPathName_U,pEXEuni.buffer,addr dospath,0,addr ntpath
invoke RtlCreateProcessParameters,addr ProcPar,addr dospath,0,0,0,0,0,0,0,0

where szEXE is the ansistring and pEXEansi is the string structure for ansi and pEXEuni for unicode. You better leave VB and goto assembler if you are going to mess with ntdll.dll

Well ASM is way over my head so I am not touching that until I take some classes in it. My solution would be to use C++ but problem is I do not know C++ and I am highly familiar with VB6

So are you basically saying that Unicode strings in VB6 are impossible to do?

[altf4]

Nevermind I figured it out.

[penagate]

VB6 strings are natively Unicode. There is no need to do this.

You better leave VB and goto assembler if you are going to mess with ntdll.dll

I don't see why.

[minor28]

Unicode and BSTR are not the same. It's not primary the string problem but all underlying code in VB that's hard to control in lower level programming.