[RESOLVED] [2005] PInvoke on a function declared with __declspec

[agent]

I'm getting this exception when I try to get the address of a function in a dll written in vc++ 6.0. The dll is a compiled winamp plugin and I can't change the plugin source.

System.Runtime.InteropServices.MarshalDirectiveException was unhandled
  Message="Method's type signature is not PInvoke compatible."
  Source="Winamp Plugin Host"
  StackTrace:
       at Winamp_Plugin_Host.OutputPlugin.GetProcAddress(Int32 hModule, String& lpProcName)
       at Winamp_Plugin_Host.OutputPlugin..ctor(String FromFile) in C:\Documents and Settings\Jack Schitt\Desktop\design\programming\Winamp Plugin Host\PluginClasses.vb:line 76

Is there any way in vb.net 2005 to call a function declared as:

__declspec( dllexport ) Out_Module * winampGetOutModule()

...hopefully using LoadLibraryEX, GetProcAddress, and FreeLibrary...

[penagate]

<DllImport("dll_name", CallingConvention:=CallingConvention.Cdecl)> _
Private Function WinampGetOutModule() As [...]
End Function 

[agent]

Originally Posted by penagate

<DllImport("dll_name", CallingConvention:=CallingConvention.Cdecl)> _
Private Function WinampGetOutModule() As [...]
End Function 

I was using the LoadLibrary, GetProcAddress, and FreeLibrary functions before as they allow me to dynamically specify the dll. (The dll to load varies and there are multiple dlls to load).

Can this be done with either DllImport or Declare?

[penagate]

Dynamic DLLImport

Hope you can convert C# to VB.

[agent]

Originally Posted by penagate

Dynamic DLLImport

Hope you can convert C# to VB.

It looks a little complicated for what I'm trying to do and seems to apply to .Net 1.x.

I'm including the unfinished class I'm working on. If you have winamp, create a new instance of the class and provide the full path to any dll file in the plugins folder of winamp who's filename begins with "OUT".

The test in this case would be to run the About method of the class and see if you get an 'About This Plugin...' type window. I haven't been able to test any of the delegates in the OutModule structure as the problem I'm having occures before this is returned.

You can get winamp free at winamp.com. The sdk is available free at http://www.winamp.com/nsdn/winamp/sdk/index.php

Public Class OutputPlugin
    Implements IDisposable

    Private Declare Function LoadLibraryEx Lib "kernel32.dll" Alias "LoadLibraryExA" (ByVal lpLibFileName As String, ByVal hFile As Int32, ByVal dwFlags As Int32) As Int32
    Private Declare Function FreeLibrary Lib "kernel32.dll" (ByVal hLibModule As Integer) As Integer
    Private Declare Function GetProcAddress Lib "kernel32.dll" (ByVal hModule As Integer, ByVal lpProcName As String) As ptrwinampGetOutModule

    Private Const LOAD_WITH_ALTERED_SEARCH_PATH As Int32 = &H8

    'Main delegate. The declare above for GetProcAddress returns this type
    Private Delegate Function ptrwinampGetOutModule() As OutModule

    Private _Lib As Integer 'holds HMODULE for dll file
    Private _OutModule As OutModule 'holds the plugin info

    Sub New(ByVal FromFile As String)
        MyBase.New()

        'load the library. FreeLibrary is called in Dispose
        _Lib = LoadLibraryEx(FromFile, 0, LOAD_WITH_ALTERED_SEARCH_PATH)

        'Get the address for function winampGetOutModule...
        Dim tmp As ptrwinampGetOutModule = GetProcAddress(_Lib, "winampGetOutModule")

        '...and call it
        _OutModule = tmp.Invoke

    End Sub

#Region " IDisposable Support "
    Private disposedValue As Boolean = False        ' To detect redundant calls

    ' IDisposable
    Protected Overridable Sub Dispose(ByVal disposing As Boolean)
        If Not Me.disposedValue Then
            If disposing Then
                ' TODO: free unmanaged resources when explicitly called
            End If

            ' TODO: free shared unmanaged resources
            FreeLibrary(_Lib)
        End If
        Me.disposedValue = True
    End Sub

    ' This code added by Visual Basic to correctly implement the disposable pattern.
    Public Sub Dispose() Implements IDisposable.Dispose
        ' Do not change this code.  Put cleanup code in Dispose(ByVal disposing As Boolean) above.
        Dispose(True)
        GC.SuppressFinalize(Me)
    End Sub
#End Region

#Region "OutModule Structure"
    '"Slightly" modified def of the structure. See OUT.H in the sdk for the original version
    <StructLayout(LayoutKind.Sequential)> _
    Public Structure OutModule
        Public version As Integer               '// module version (OUT_VER)
        Public description As String            '// description of module, with version string
        Public id As Integer                    '// module id. each input module gets its own. non-nullsoft modules should
        '// be >= 65536. 

        Public hMainWindow As Integer           '// winamp's main window (filled in by winamp)
        Public hDllInstance As Integer         '// DLL instance handle (filled in by winamp)

        Public Delegate Sub ptrConfig(ByVal hwndParent As Integer)
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Config As ptrConfig '(HWND hwndParent); '// configuration dialog 

        Public Delegate Sub ptrAbout(ByVal hwndParent As Integer)
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public About As ptrAbout '(HWND hwndParent);  '// about dialog

        Public Delegate Sub ptrInit()
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Init As ptrInit '();    '// called when loaded

        Public Delegate Sub ptrQuit()
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Quit As ptrQuit '();    '// called when unloaded

        Public Delegate Function ptrOpen(ByVal SampleRate As Integer, ByVal NumChannels As Integer, ByVal BitsPerSamp As Integer, ByVal BufferLenMS As Integer, ByVal PreBufferMS As Integer) As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Open As ptrOpen '(int samplerate, int numchannels, int bitspersamp, int bufferlenms, int prebufferms); 
        '// returns >=0 on success, <0 on failure
        '// NOTENOTENOTE: bufferlenms and prebufferms are ignored in most if not all output plug-ins. 
        '//    ... so don't expect the max latency returned to be what you asked for.
        '// returns max latency in ms (0 for diskwriters, etc)
        '// bufferlenms and prebufferms must be in ms. 0 to use defaults. 
        '// prebufferms must be <= bufferlenms

        Public Delegate Sub ptrClose()
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Close As ptrClose '();   '// close the ol' output device.

        Public Delegate Function ptrWrite(ByRef buf As Byte(), ByVal len As Integer) As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Write As ptrWrite '(char *buf, int len); 
        '// 0 on success. Len == bytes to write (<= 8192 always). buf is straight audio data. 
        '// 1 returns not able to write (yet). Non-blocking, always.

        Public Delegate Function ptrCanWrite() As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public CanWrite As ptrCanWrite '(); '// returns number of bytes possible to write at a given time. 
        '// Never will decrease unless you call Write (or Close, heh)

        Public Delegate Function ptrIsPlaying() As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public IsPlaying As ptrIsPlaying '(); '// non0 if output is still going or if data in buffers waiting to be
        '// written (i.e. closing while IsPlaying() returns 1 would truncate the song

        Public Delegate Function ptrPause(ByVal Pause As Integer) As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Pause As ptrPause '(int pause); '// returns previous pause state

        Public Delegate Sub ptrSetVolume(ByVal volume As Integer)
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public SetVolume As ptrSetVolume '(int volume); '// volume is 0-255

        Public Delegate Sub ptrSetPan(ByVal pan As Integer)
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public SetPan As ptrSetPan '(int pan); '// pan is -128 to 128

        Public Delegate Sub ptrFlush(ByVal t As Integer)
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public Flush As ptrFlush '(int t);  '// flushes buffers and restarts output at time t (in ms) 
        '// (used for seeking)

        Public Delegate Function ptrGetOutputTime() As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public GetOutputTime As ptrGetOutputTime '(); '// returns played time in MS

        Public Delegate Function ptrGetWrittenTime() As Integer
        <MarshalAs(UnmanagedType.FunctionPtr)> _
        Public GetWrittenTime As ptrGetWrittenTime '(); '// returns time written in MS (used for synching up vis stuff)
    End Structure
#End Region

#Region "Methods"
    'these call the pointers to the various functions of the plugin.
    'Note: this section is not yet complete

    'Plugin loads settings, etc.
    Public Sub Init()
        _OutModule.Init()
    End Sub

    'Plugin saves settings, closes devices
    Public Sub Quit()
        _OutModule.Quit()
    End Sub

    'Show the about window
    Public Sub About(ByVal Owner As Form)
        _OutModule.About(Owner.Handle)
    End Sub

    'Show the config window
    Public Sub Config(ByVal Owner As Form)
        _OutModule.Config(Owner.Handle)
    End Sub
#End Region

End Class 

[agent]

Not for the faint at heart...

I took my previous code and added a dynamic binder as suggested by penagate. Everything, including the dynamic binding works un until the point where it calls the function in the dll. Then I get the same exception (signature not PInvoke compatible).

This is the entire contents of the plugin file... (The exception occurs on the bolded line near the bottom)
The second code section is the function template I'm using. This file should have its build action set to none. Additionally, add it as a resource via the resource manager. The resource should be named 'Template'

WinampPluginClasses.vb

Imports System.Runtime.InteropServices
Imports System.CodeDom

Public Class OutputPlugin
    'function name = winampGetOutModule

    'Main delegate. The declare above for GetProcAddress returns this type
    Private Delegate Function ptrwinampGetOutModule() As OutModule

    Private _OutModule As OutModule 'holds the plugin info

    Sub New(ByVal FromFile As String)
        MyBase.New()

        _OutModule = DynamicBinding(Of OutModule).CallFunction(FromFile, "winampGetOutModule")

    End Sub

#Region "Methods"
    'these call the pointers to the various functions of the plugin.
    'Note: this section is not yet complete

    'Plugin loads settings, etc.
    Public Sub Init()
        _OutModule.Init()
    End Sub

    'Plugin saves settings, closes devices
    Public Sub Quit()
        _OutModule.Quit()
    End Sub

    'Show the about window
    Public Sub About(ByVal Owner As Form)
        _OutModule.About(Owner.Handle)
    End Sub

    'Show the config window
    Public Sub Config(ByVal Owner As Form)
        _OutModule.Config(Owner.Handle)
    End Sub
#End Region

End Class

#Region "OutModule Structure"
'"Slightly" modified def of the structure. See OUT.H in the sdk for the original version
<StructLayout(LayoutKind.Sequential)> _
Public Structure OutModule
    Public version As Integer               '// module version (OUT_VER)
    Public description As String            '// description of module, with version string
    Public id As Integer                    '// module id. each input module gets its own. non-nullsoft modules should
    '// be >= 65536. 

    Public hMainWindow As Integer           '// winamp's main window (filled in by winamp)
    Public hDllInstance As Integer         '// DLL instance handle (filled in by winamp)

    Public Delegate Sub ptrConfig(ByVal hwndParent As Integer)
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Config As ptrConfig '(HWND hwndParent); '// configuration dialog 

    Public Delegate Sub ptrAbout(ByVal hwndParent As Integer)
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public About As ptrAbout '(HWND hwndParent);  '// about dialog

    Public Delegate Sub ptrInit()
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Init As ptrInit '();    '// called when loaded

    Public Delegate Sub ptrQuit()
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Quit As ptrQuit '();    '// called when unloaded

    Public Delegate Function ptrOpen(ByVal SampleRate As Integer, ByVal NumChannels As Integer, ByVal BitsPerSamp As Integer, ByVal BufferLenMS As Integer, ByVal PreBufferMS As Integer) As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Open As ptrOpen '(int samplerate, int numchannels, int bitspersamp, int bufferlenms, int prebufferms); 
    '// returns >=0 on success, <0 on failure
    '// NOTENOTENOTE: bufferlenms and prebufferms are ignored in most if not all output plug-ins. 
    '//    ... so don't expect the max latency returned to be what you asked for.
    '// returns max latency in ms (0 for diskwriters, etc)
    '// bufferlenms and prebufferms must be in ms. 0 to use defaults. 
    '// prebufferms must be <= bufferlenms

    Public Delegate Sub ptrClose()
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Close As ptrClose '();   '// close the ol' output device.

    Public Delegate Function ptrWrite(ByRef buf As Byte(), ByVal len As Integer) As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Write As ptrWrite '(char *buf, int len); 
    '// 0 on success. Len == bytes to write (<= 8192 always). buf is straight audio data. 
    '// 1 returns not able to write (yet). Non-blocking, always.

    Public Delegate Function ptrCanWrite() As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public CanWrite As ptrCanWrite '(); '// returns number of bytes possible to write at a given time. 
    '// Never will decrease unless you call Write (or Close, heh)

    Public Delegate Function ptrIsPlaying() As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public IsPlaying As ptrIsPlaying '(); '// non0 if output is still going or if data in buffers waiting to be
    '// written (i.e. closing while IsPlaying() returns 1 would truncate the song

    Public Delegate Function ptrPause(ByVal Pause As Integer) As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Pause As ptrPause '(int pause); '// returns previous pause state

    Public Delegate Sub ptrSetVolume(ByVal volume As Integer)
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public SetVolume As ptrSetVolume '(int volume); '// volume is 0-255

    Public Delegate Sub ptrSetPan(ByVal pan As Integer)
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public SetPan As ptrSetPan '(int pan); '// pan is -128 to 128

    Public Delegate Sub ptrFlush(ByVal t As Integer)
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public Flush As ptrFlush '(int t);  '// flushes buffers and restarts output at time t (in ms) 
    '// (used for seeking)

    Public Delegate Function ptrGetOutputTime() As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public GetOutputTime As ptrGetOutputTime '(); '// returns played time in MS

    Public Delegate Function ptrGetWrittenTime() As Integer
    <MarshalAs(UnmanagedType.FunctionPtr)> _
    Public GetWrittenTime As ptrGetWrittenTime '(); '// returns time written in MS (used for synching up vis stuff)
End Structure
#End Region

Friend Class DynamicBinding(Of ReturnStructure As Structure)
    'replacements in template
    Private Const DLLName As String = "DLLName"
    Private Const [Structure] As String = "Integer"
    Private Const FunctionName As String = "FunctionName"

    'name of module
    Private Const ClassName As String = "CallDll"

    Public Shared Function CallFunction(ByVal DLL As String, ByVal Funct As String) As ReturnStructure
        'Code is loaded from a resource. see Template.VB
        Dim TemplateCode As String = My.Resources.Template

        'Replace parts of the code with the constants above
        TemplateCode = Replace(TemplateCode, DLLName, DLL)
        TemplateCode = Replace(TemplateCode, FunctionName, Funct)
        TemplateCode = Replace(TemplateCode, [Structure], GetType(ReturnStructure).FullName)

        'Compile the code
        Dim CompileUnit As New CodeSnippetCompileUnit(TemplateCode)
        Dim TemplateCodeArray As String() = {TemplateCode}
        Dim Params As New Compiler.CompilerParameters()

        With Params
            .GenerateExecutable = False
            .GenerateInMemory = True
            .IncludeDebugInformation = False
            .ReferencedAssemblies.Add(Application.ExecutablePath)
        End With

        Dim CodeProvider As New Microsoft.VisualBasic.VBCodeProvider()

        'this is the line that compiles it
        Dim CompilerResaults As Compiler.CompilerResults = CodeProvider.CompileAssemblyFromSource(Params, TemplateCodeArray)

        'if there are errors, let me see what they are
        If CompilerResaults.Errors.Count > 0 Then
            Dim ce As Object = CompilerResaults.Errors
            Dim item As Object

            For Each item In ce
                'cheap and simple way of debugging compiler errors:
                'hover the mouse over 'item' in the code window while stopped
                'it will tell you what error occured.
                Stop
            Next
        End If

        'now it should be compiled, use relfection to call the code
        Dim Assembly As System.Reflection.Assembly = CompilerResaults.CompiledAssembly
        Dim [class] As System.Type = Assembly.GetType(ClassName)
        Dim method As Reflection.MethodInfo = [class].GetMethod(Funct, Reflection.BindingFlags.Static Or Reflection.BindingFlags.Public Or Reflection.BindingFlags.FlattenHierarchy)

        [b]Return DirectCast(method.Invoke(Nothing, Nothing), ReturnStructure)[/b]

    End Function
End Class 

Template.vb

Public Class CallDll
    <System.Runtime.InteropServices.DllImport("DLLName", CallingConvention:=System.Runtime.InteropServices.CallingConvention.StdCall)> _
    Public Shared Function FunctionName() As Integer
    End Function
End Class 

[agent]

Looks like I got it working. I'll post the working code after optimizing it a bit. I knew dynamically compiling code was a little overkill. I'm switching it back to LoadLibrary, GetProcAddress, and FreeLibrary.

The problem was that (apparently) you can't PInvoke something if the return value isn't something standard (i.e. a number or a boolean.)

Now, I simply take the number returned and use that as the first param of Marshal.PtrToStructure

Now the test works properly and it looks like I don't need to compile code from my program.

(If you found this post by doing a search for compiling code or executing scripts from your app, the above source code does do that, btw)