DLL Callback

12 Jul 2006 2:51 AM

Nigel Walton

I am trying to read some data from a dll via a callback. I have a
deligate and all imformation is correct except for an array.

This is the original struct in c:

typedef void (*PutSampProc)(short samples[], int arraylen, int
nrsamples,void *userData);

This does not work:

<StructLayout(LayoutKind.Sequential)> _
Public Structure PutSampProc2
    <MarshalAs(UnmanagedType.ByValArray,SizeConst:=1024)> _
        Dim Samples() As Short
        Dim ArrayLen As Integer
        Dim NrSamples As Integer
        Dim Userdata As Byte
End Structure

This gives the correct data for ArrayLen, NrSamples and Userdata, but
just a value for the Samples():

<StructLayout(LayoutKind.Sequential)> _
Public Structure PutSampProc
        Dim Samples As Integer
        Dim ArrayLen As Integer
        Dim NrSamples As Integer
        Dim Userdata As Byte
End Structure

What am I doing wrong????

Please help

Nigel

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12 Jul 2006 6:09 AM

Mattias Sjögren

Nigel,

>This is the original struct in c:
>
>typedef void (*PutSampProc)(short samples[], int arraylen, int
>nrsamples,void *userData);

This is not a struct declaration, it's a function pointer type.

Mattias

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Mattias Sjögren [C# MVP] mattias @ mvps.org
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27 Jul 2006 1:34 PM

Nigel Devon

I now have it working like this:

Private Sub SampProc(ByVal Samples As Integer, ByVal ArrayLen As
Integer, ByVal NrSamples As Integer, ByVal UserData As Byte)
ReDim MySamples((NrSamples * 2) - 1)
Marshal.Copy(Samples, MySamples, 0, NrSamples * 2)

Is it possible to receive 'Samples' as an array. Do I have to add some
marshalling code to my delegate?

Nigel

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