Enum GrfErrorType
        GE_SUCCESS
        GE_BADARGS
        GE_INVALID
        GE_CORRUPTED
        GE_NSUP
        GE_NOTFOUND
        GE_INDEX
        GE_ERRNO
        GE_ZLIB
        GE_ZLIBFILE
        GE_NODATA
        GE_BADMODE
        GE_NOTIMPLEMENTED
    End Enum
 
    Public Structure GrfError
        Public type As GrfErrorType
        Public line As Integer
        Public name As String
        Public func As String
        Public extra As Int64
    End Structure
 
    Public Structure GrfFile
        Public compressed_len_aligned As Integer
        Public compressed_len As Integer
        Public real_len As Integer
        Public flags As Int16
        Public hash As Integer
        Public name As String
        Public data As String
    End Structure
 
    Public Structure Grf
        Public filename As String
        Public len As Integer
        Public type As Integer
        Public version As Integer
        Public nfiles As Integer
        Public files() As GrfFile
        Public first As GrfFile
        Public last As GrfFile
 
        Public allowCrypt As Int16
        Public f As System.IO.File
        Public allowWrite As Int16
        Public zbuf As Object ' void
    End Structure
 
    Public Structure GrfOpenCallback
        Public file As GrfFile
        Public mError As GrfError
    End Structure
 
    ' GRF Library (grf.dll) functions
    Public Declare Function GrfOpen Lib "grf.dll" Alias "grf_open" (ByVal fname _
      As String, ByVal mode As String, ByVal mError As GrfError, ByVal callback _
      As GrfOpenCallback) As Grf
    'Public Declare Function GrfOpen Lib "grf.dll" Alias "grf_open_callback" ( 
    ' ByVal fname As String, ByVal mode As String, ByVal mError As GrfError, 
    ' ByVal callback As IntPtr) As Grf
    Public Declare Function GrfExtract Lib "grf.dll" Alias "grf_extract" (ByVal _
      grf As Grf, ByVal grfname As String, ByVal file As String, ByVal mError _
      As GrfError) As Integer
    Public Declare Function GrfClose Lib "grf.dll" Alias "grf_close" (ByVal grf _
    As Grf)
    Public Declare Function GrfFree Lib "grf.dll" Alias "grf_free" (ByVal grf _
    As Grf)
 
    Sub Main()
        Try
            Dim grf As Grf
            Dim err As GrfError
            Dim cb As GrfOpenCallback
            grf = GrfOpen("data.gpf", "rb", err, grf)
        Catch ex As Exception
            Console.WriteLine(ex.ToString)
        End Try
    End Sub