I can't run a test on this here right now, but what happens if you
modify your DLL to return the value of NULL?
>Hi,
>
>Thanks for your answer Joe,sorry to say it doesn't work.
>
>To investigate the problem I have now created a small dll in eVC with
>the following code :
>----------------------
>DWORD WINAPI fnTest (DWORD *lpTest)
>{
> if (lpTest == NULL)
> {
> return 0;
> }
> else
> {
> return 1;
> }
>}
>-----------------------
>So the function simply checks if the value (a pointer to a long) is
>NULL and in that case returns 0, else 1
>
>Then I call this function from eVB or NSB with the following code :
>
>-----------------------
>Option Explicit
>Declare Function fnTest Lib "test.DLL" (ByRef lpTest As Long) As Long
>
>Private Sub Command1_Click()
>Dim testlng
> testlng = CLng(0)
> On Error Resume Next
> MsgBox "test 1 :" & fnTest(0)
> MsgBox "test 2 :" & fnTest(testlng)
> MsgBox "test 3 :" & fnTest(Null)
> MsgBox "test 4 :" & fnTest(vbNull)
> MsgBox "test 5 :" & fnTest(vbNullString)
> MsgBox "test 6 :" & fnTest(vbnullptr)
>End Sub
>------------------------
>
>Result is that ONLY the last msgbox (test6) returns 0 in eVB, all
>other calls return 1.
>That means that the vbNullPtr constant is needed to give the lpTest
>parameter the value NULL as recognized by C.
>
>There seems to be no way to get this result in NS Basic as there is
>no vbnullptr constant there.
>
>As I have lots and lots of APIs and DLL functions to use in my
>planned project, and some parameters are required to be NULL, is
>there any chance of enhancing NS Basic to be able to do this ?
>
>If someone wants to test I can post the above DLL.
>
>Thanks for your help...
> Jingjok
>
>
>
>--- In [email protected], "joespan123" <j...@...> wrote:
>>
>> I searched google and can not really find anything but snippets of
>> what vbNullPtr is supposed to be used for, that is:
>>
>> "vbNullPtr Constant: The constant vbNullPtr should be used only for
>> ByRef parameters."
>>
>> Given that a variable to a subroutine is a ByRef by default, that
>is a
>> pointer, see if the following code snippet may work.
>>
>> Public Const vbNullPtrDef = 0
>>
>> Sub RZipInitWrapper(ByVal FirstArg, ByRef vbNullPtrVar)
>>
>> Call RZipInit(FirstArg, vbNullPtrVar)
>>
>> End Sub
>>
>> Call RZipInitWrapper(57236465, vbNullPtrDef)
>>
>> or try
>>
>> Dim MyLong
>> MyLong = CLong(0)
>>
>> Call RZipInitWrapper(57236465, MyLong)
>>
>> I do not know if this will work or not as I do not have a DLL to
>test
>> it on.
>>
>> Regards
>> Joe
>>
>>
>> --- In [email protected], "jingjok67" <jingjok67@> wrote:
>> >
>> > Hi,
>> >
>> > No, that does not work either. It seems nothing (I tried in eVB,
>too)
>> > except vbNullPtr works. Looks like anything else is still a
>variant
>> > and vbNullPtr is converted by eVB into something special.
>> >
>> > It looks like the function I am trying to call is badly written
>and
>> > does not accept 0 instead of NULL. This problem hopefully does not
>> > occur with APIs as they accept 0 instead of NULL ? Does anyone
>have
>> > experience with this ?
>> >
>> > The only workaround I can think of is to write a C DLL to wrap the
>> > functions that use null pointers, which is quite ugly and I do not
>> > really want to do that.
>> >
>> > Any chance to include vbNullPtr in NS Basic ?
>> >
>> > In the meantime - is there any other ZIP compression library that
>> > works with NS Basic ?
>> >
>> > Thanks for your help.
>> >
>> >
>> >
>> > --- In [email protected], "George Henne" <gh@> wrote:
>> > >
>> > > Can you give this a try?
>> > >
>> > > vbNullPtr = clng(0)
>> > > Call RZipInit (57236465, vbNullPtr)
>> > >
>> > > I have no idea if this will work, but the first line forces the
>> subtype
>> > > of vbNullPtr to be a long, which may help.
>> > >
>> > > >Hello George,
>> > > >
>> > > >That is strange, if I try the line
>> > > >
>> > > >Msgbox typename(vbNullPtr) & " " & vbNullPtr
>> > > >
>> > > >in eVB and run the code I get an error that variable vbNullPtr
>is not
>> > > >defined. But then when I use the vbNullPtr in a declared
>function
>> > > >call, it works ! I have triple-checked and did not make a
>writing
>> > mistake.
>> > > >
>> > > >It looks like eVB is only accepting this constant as a
>parameter for
>> > > >declared functions.
>> > > >
>> > > >What I am trying to do is to use the Resco ZIP DLL, here is the
>> sample
>> > > >code (NS Basic) :
>> > > >
>> > > >Option Explicit
>> > > >
>> > > >Declare "Sub RZipInit Lib ""RZip.dll"" (ByVal uCode As Long,
>ByRef
>> > > >lpCallbackFunc As Long)"
>> > > >
>> > > >Call RZipInit (57236465, vbNullPtr)
>> > > >
>> > > >This code works fine in eVB but NS Basic gives me an error that
>> > > >vbNullPtr is not defined.
>> > > >
>> > > >I have then done further testing in eVB and NS Basic and found
>that I
>> > > >cannot substitute vbNullPtr with anything else, i.e. Null,
>nothing,
>> > > >vbNull, 0, vbNullString, vbNullChar. In that case the code
>runs but
>> > > >the function fails. ONLY vbNullPtr works. I guess that is the
>reason
>> > > >why Microsoft added the vbNullPtr in the first place.
>> > > >
>> > > >It looks like the code in the RZipInit dll checks this
>parameter for
>> > > >NULL (as in C++), i.e.
>> > > >if (param2 == NULL) DoSomething
>> > > >The dll call obviously converts anything except vbNullPtr to
>> something
>> > > >else than NULL (as defined in C)
>> > > >
>> > > >
>> > > >Then... is there any way to use or substitute vbNullPtr in NS
>> Basic or
>> > > >any other trick to make this work ?
>> > > >
>> > > >Thanks for your help.
>> > > >
>> > > >
>> > > >
>> > > >
>> > > >--- In [email protected], "George Henne" <gh@> wrote:
>> > > >>
>> > > >> My copy of eVB has decided it does not want to work anymore,
>so I
>> > can't
>> > > >> try this here at the moment.
>> > > >>
>> > > >> Write a short eVB program that does
>> > > >>
>> > > >> Msgbox typename(vbNullPtr) & " " & vbNullPtr
>> > > >>
>> > > >> Hopefully, that will give the answer. Let us know, so we can
>add
>> > this to
>> > > >> the Tech Note.
>> > > >>
>> > > >> >Hi,
>> > > >> >
>> > > >> >I need to call an function in a dll with a vbNullPtr (this
>is
>> > > >> >pre-defined in eVB) value in a parameter. What is the
>> substitute for
>> > > >> >vbNullPtr in NS Basic ? I tried Null but that did not work.
>> > > >> >
>> > > >> >Thanks !
>> > > >> >
>> > > >> >
>> > > >> >------------------------------------
>> > > >> >
>> > > >> >Yahoo! Groups Links
>> > > >> >
>> > > >> >
>> > > >> >
>> > > >>
>> > > >
>> > > >
>> > > >
>> > > >------------------------------------
>> > > >
>> > > >Yahoo! Groups Links
>> > > >
>> > > >
>> > > >
>> > >
>> >
>>
>
>
>
>------------------------------------
>
>Yahoo! Groups Links
>
>
>
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