LPCSTR marshalling to unmanaged dll

[John Lucas]

I wish to call an unmanaged function from vb delacred as so:

#define DllExport __declspec(dlle xport)
DllExport int WINAPI DllAlcWrite(HAN DLE, LPCSTR, int);


I have tried:

1.)
Private Declare Ansi Function DllAlcWrite Lib "alcsapi" (ByVal hConn
As Long, ByVal strGWOutgoing As String, ByVal intStringLength As
Integer) As Integer

<VBFixedString( 255)> Private strOutgoingBuff er As String
strOutgoingBuff er ="FOO"
intReturn = DllAlcWrite(m_H andle, strOutgoingBuff er, 3)

2.)
<DllImport("alc sapi.dll")> _
Private Shared Function DllAlcWrite(ByV al hConn As Long, ByVal
strGWOutgoing As String, ByVal intStringLength As Integer) As Integer
End Function
<VBFixedString( 255)> Private strOutgoingBuff er As String
strOutgoingBuff er ="FOO"
intReturn = DllAlcWrite(m_H andle, strOutgoingBuff er, 3)

3.)
<DllImport("alc sapi.dll", CharSet:=CharSe t.Ansi,
CallingConventi on:=CallingConv ention.Cdecl)> _
Private Shared Function DllAlcWrite(ByV al hConn As Long, ByVal
strGWOutgoing As String, ByVal intStringLength As Integer) As Integer
End Function
<VBFixedString( 255)> Private strOutgoingBuff er As String
strOutgoingBuff er ="FOO"
intReturn = DllAlcWrite(m_H andle, strOutgoingBuff er, 3)

( i know the handle is long, but it is working for other functions in
this dll)

I have also tried setting the string length (3rd parm)to 255
I am able to call other functions in this dll ok
=============== =============== ===

All of them generate the NullReference exception. Is there a way to
properly marshal LPCSTR?

Help!

[Mattias Sjögren]

Re: LPCSTR marshalling to unmanaged dll

[color=blue]
>( i know the handle is long, but it is working for other functions in
>this dll)[/color]

Did you mean to say that it isn't a Long? Because it isn't, and you
should replace it with IntPtr or Integer.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[John Lucas]

Re: LPCSTR marshalling to unmanaged dll

Mattias,

It doesn't seem to matter, I still get a nullreference exception with
this:

<DllImport("alc sapi.dll", CharSet:=CharSe t.Ansi,
CallingConventi on:=CallingConv ention.Cdecl)> _
Private Shared Function DllAlcWrite(ByV al hConn As Long, ByVal
strGWOutgoing As String, ByVal intStringLength As Integer) As Integer
End Function
<DllImport("alc sapi.dll")> _
Private Shared Function DllInitAlc(ByVa l Board As Integer, ByVal
lngLine As Integer, _
ByVal GWName As String, ByVal IA As Integer, ByVal TA As Integer) As
IntPtr
End Function

Dim m_handle as IntPtr
m_Handle=DllIni tAlc(CInt(lngBo ard), CInt(lngLine), strServer,
lngIAHex, lngTAHex)
'(got a non zero handle)


<VBFixedString( 255)> Private strOutgoingBuff er As String
strOutgoingBuff er ="FOO"

intReturn = DllAlcWrite(m_H andle, strOutgoingBuff er, 3)
'(exception)





Mattias Sjögren <mattias.dont.w ant.spam@mvps.o rg> wrote in message news:<eOvr0yePE HA.2820@TK2MSFT NGP10.phx.gbl>. ..[color=blue][color=green]
> >( i know the handle is long, but it is working for other functions in
> >this dll)[/color]
>
> Did you mean to say that it isn't a Long? Because it isn't, and you
> should replace it with IntPtr or Integer.
>
>
>
> Mattias[/color]

[Mattias Sjögren]

Re: LPCSTR marshalling to unmanaged dll

John,
[color=blue]
><DllImport("al csapi.dll", CharSet:=CharSe t.Ansi,
>CallingConvent ion:=CallingCon vention.Cdecl)> _
>Private Shared Function DllAlcWrite(ByV al hConn As Long, ByVal
>strGWOutgoin g As String, ByVal intStringLength As Integer) As Integer
>End Function[/color]

Did you change anything? hConn is still declared as Long.



Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

[John Lucas]

Re: LPCSTR marshalling to unmanaged dll

I changed it to intPtr and stilll have the same problem.


Mattias Sjögren <mattias.dont.w ant.spam@mvps.o rg> wrote in message news:<eRg314oPE HA.556@tk2msftn gp13.phx.gbl>.. .[color=blue]
> John,
>[color=green]
> ><DllImport("al csapi.dll", CharSet:=CharSe t.Ansi,
> >CallingConvent ion:=CallingCon vention.Cdecl)> _
> >Private Shared Function DllAlcWrite(ByV al hConn As Long, ByVal
> >strGWOutgoin g As String, ByVal intStringLength As Integer) As Integer
> >End Function[/color]
>
> Did you change anything? hConn is still declared as Long.
>
>
>
> Mattias[/color]

[Tom Shelton]

Re: LPCSTR marshalling to unmanaged dll

On 19 May 2004 14:48:51 -0700, John Lucas wrote:
[color=blue]
> I wish to call an unmanaged function from vb delacred as so:
>
> #define DllExport __declspec(dlle xport)
> DllExport int WINAPI DllAlcWrite(HAN DLE, LPCSTR, int);
>
>
> I have tried:
>
> 1.)
> Private Declare Ansi Function DllAlcWrite Lib "alcsapi" (ByVal hConn
> As Long, ByVal strGWOutgoing As String, ByVal intStringLength As
> Integer) As Integer[/color]


Private Declare Ansi Function DllAlcWrite Lib "alcsapi.dl l" _
(ByVal hConn As IntPtr, _
ByVal strGWOutgoing As String, _
ByVal intStringLength As Integer) As Integer

' air code :)
Dim buffer As String = new String(vbNullCh ar, 255)
DllAlcWrite (hConn, buffer, buffer.Length)

HTH
--
Tom Shelton [MVP]

[John Lucas]

Re: LPCSTR marshalling to unmanaged dll

Tom,

That was it! Null termination character.

Here's what I ended up with.

Dim buffer As String
buffer = strSendThis
buffer.PadRight (255, vbNullChar)
intReturn = DllAlcWrite(m_S abreHandle, buffer, buffer.Length)


THANK YOU.
-john

Tom Shelton <tom@YOUKNOWTHE DRILLmtogden.co m> wrote in message news:<1294ovn4y 9q94$.ldmzatpna 8tc$.dlg@40tude .net>...[color=blue]
> On 19 May 2004 14:48:51 -0700, John Lucas wrote:
>[color=green]
> > I wish to call an unmanaged function from vb delacred as so:
> >
> > #define DllExport __declspec(dlle xport)
> > DllExport int WINAPI DllAlcWrite(HAN DLE, LPCSTR, int);
> >
> >
> > I have tried:
> >
> > 1.)
> > Private Declare Ansi Function DllAlcWrite Lib "alcsapi" (ByVal hConn
> > As Long, ByVal strGWOutgoing As String, ByVal intStringLength As
> > Integer) As Integer[/color]
>
>
> Private Declare Ansi Function DllAlcWrite Lib "alcsapi.dl l" _
> (ByVal hConn As IntPtr, _
> ByVal strGWOutgoing As String, _
> ByVal intStringLength As Integer) As Integer
>
> ' air code :)
> Dim buffer As String = new String(vbNullCh ar, 255)
> DllAlcWrite (hConn, buffer, buffer.Length)
>
> HTH[/color]