Using virtual classes in VB.NET from DLL

[lkd]

Hi, Im running into a problem when trying to use class interfaces from this library called Audiere. The library was written in C++ as virtual functions that were COM compatible. To use the interface you call a function in the DLL that returns a pointer to the interface (Factory?). They are bindings for Purebasic and Delphi that use the interfaces directly. I made a binding for the D language using interfaces that inherited from the IUnknown interface and it worked. Since .NET supports COM interop I thought this should work easily. I created the interfaces and marshaled them as IUnknown(I had to inherit from IUnknown to get it to work in D). I declared the functions in the DLL and had it return the interface. I tried to run it but it gives me a fatal error code. I tried to marshal the return type as UnmanagedType.IUnknown and UnmanagedType.Interface but it still fails. Is the interface code in .NET using a non standard vtable or something? Ive included the code.


VB Audiere Header
-----------------
audiere.vb

Imports System.Runtime.InteropServices

Module Audiere

<ComVisible(True), ComImport()> _
Interface RefCounted
Sub ref() int
Sub unref() int
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface File : Inherits RefCounted
Function read(ByVal pbuffer As Integer, ByVal size As Integer) As Integer int
Function seek(ByVal position As Integer, ByVal SeekMode As Integer) As Boolean bool
Function tell() As Integer int
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface SampleBuffer : Inherits RefCounted
Sub getFormat(ByVal channel_count As Integer, ByVal sample_rate As Integer, ByVal lsample_format As Integer) Sub
Function getLength() As Integer int
Function getSamples() As Integer int
Function openStream() As SampleSource pSampleSource
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface SampleSource : Inherits RefCounted
Sub getFormat(ByVal v As Integer, ByVal v2 As Integer) Sub
Function Read(ByVal v As Integer, ByVal v2 As Integer) As Integer int
Sub reset() Sub
Function isSeekable() As Boolean bool
Function getLength() As Integer int
Sub setPosition(ByVal v As Integer) Sub
Function getPosition() As Integer int
Function getRepeat() As Boolean bool
Sub setRepeat(ByVal v As Integer) Sub
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface LoopPointSource : Inherits SampleSource
Sub addLoopPoint(ByVal location As Integer, ByVal target As Integer, ByVal loopCount As Integer) Sub
Sub removeLoopPoint(ByVal index As Integer) Sub
Function getLoopPointCount() As Integer int
Function getLoopPoint(ByVal index As Integer, ByVal plocation As Integer, ByVal ptarget As Integer, ByVal ploopCount As Integer) As Boolean bool
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface OutputStream : Inherits RefCounted
Function play() As Boolean
Function _stop() As Boolean bool
Function isPlaying() As Boolean bool
Sub reset() Sub
Sub setRepeat(ByVal v As Boolean) Sub
Function getRepeat() As Boolean bool
Sub setVolume(ByVal v As Single) Sub
Function getVolume() As Single float
Sub setPan(ByVal v As Single) Sub
Function getPan() As Single float
Sub setPitchShift(ByVal v As Single) Sub
Function getPitchShift() As Single float
Function isSeekable() As Boolean bool
Function getLength() As Integer int
Sub setPosition(ByVal v As Integer) Sub
Function getPosition() As Integer int
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface AudioDevice : Inherits RefCounted
Sub update() Sub
Function openStream(ByVal pSampleSource As SampleSource) As OutputStream OutputStream pAudOutputStream
Function openBuffer(ByRef pSamples As IntPtr, ByVal frame_count As Integer, ByVal channel_count As Integer, ByVal sample_rate As Integer, ByVal sample_format As Integer) As OutputStream pAudOutputStream
Function getName() As String char.l
End Interface

<InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
Interface SoundEffect : Inherits RefCounted
Sub play() Sub
Sub _stop() Sub
Sub setVolume(ByVal volume As Single) Sub
Function getVolume() As Single float
Sub setPan(ByVal pan As Single) Sub
Function getPan() As Single float
Sub setPitchShift(ByVal shift As Single) Sub
Function getPitchShift() As Single float
End Interface


Enum SampleFormat
SF_U8 unsigned 8-bit integer [0,255]
SF_S16 signed 16-bit integer in host end Interface ianness [-32768,32767]
End Enum

Enum FileFormat
FF_AUTODETECT
FF_WAV
FF_OGG
FF_FLAC
FF_MP3
FF_MOD
FF_AIFF
End Enum

Enum SoundEffectType

SE_SINGLE
SE_MULTIPLE
End Enum

Enum SeekMode

SM_Begin
SM_Current
SM_end
End Enum

Functions
char* AdrGetVersion()

char* AdrGetSupportedFileFormats()

char* AdrGetSupportedAudioDevices()
Declare Function GetSupportedAudioDevices Lib "audiere" Alias "_AdrGetSupportedAudioDevices@0" () As String
int AdrGetSampleSize(SampleFormat format)

AudioDevice AdrOpenDevice(char* name = null, char* parameters = null)
Declare Function OpenDevice Lib "audiere" Alias "_AdrOpenDevice@8" (Optional ByVal name As String = Nothing, Optional ByVal parameters As String = Nothing) As AudioDevice

SampleSource AdrOpenSampleSource(char* filename, FileFormat file_format)

SampleSource AdrOpenSampleSourceFromFile(File file, FileFormat file_format)

SampleSource AdrCreateTone(double frequency)

SampleSource AdrCreateSquareWave(double frequency)

SampleSource AdrCreateWhiteNoise()

SampleSource AdrCreatePinkNoise()

LoopPointSource AdrCreateLoopPointSource(SampleSource source)

OutputStream AdrOpenSound(AudioDevice device, SampleSource source, bool streaming)

SampleBuffer AdrCreateSampleBuffer(Sub* samples, int frame_count, int channel_count, int sample_rate, SampleFormat sample_format)

SampleBuffer AdrCreateSampleBufferFromSource(SampleSource source)

SoundEffect AdrOpenSoundEffect(AudioDevice device, SampleSource source, SoundEffectType type)

File AdrOpenFile(char* name, bool writeable)

File AdrCreateMemoryFile(Sub* buffer, int size)
End Module

--------------------

VB Test Code
--------------------
main.vb

Module Main

Sub Main()
Dim dev As AudioDevice = OpenDevice() fatal error when initializing interface
dev.getName()
Inkey()

End Sub

End Module