convert a C++ class to a vb.NET class

Question

i am trying to convert a c++ class to the correct vb.NET class :

this is the c++ class :

class ImageCodecInfo
{
public:          
    CLSID Clsid;
    GUID  FormatID;
    const WCHAR* CodecName;
    const WCHAR* DllName;
    const WCHAR* FormatDescription;
    const WCHAR* FilenameExtension;
    const WCHAR* MimeType;
    DWORD Flags;
    DWORD Version;
    DWORD SigCount;
    DWORD SigSize;
    const BYTE* SigPattern;
    const BYTE* SigMask;
};

my convertion is :

<StructLayout(LayoutKind.Explicit)>
    Public Class ImageCodecInfo
       

       
        <FieldOffset(?)>
         Public Clsid As IntPtr
       
        <FieldOffset(?)>
         Public FormatID As IntPtr

        <FieldOffset(?)>
        Public DllName As IntPtr
        
        <FieldOffset(32)>
        Public CodecName As IntPtr ' i am correct here
        
         <FieldOffset(?)>
         Public Version As Integer
     
        <FieldOffset(44)>
        Public FilenameExtension As IntPtr ' i am correct here
       
        <FieldOffset(48)>
        Public MimeType As IntPtr ' i am correct here

       
        <FieldOffset(?)>
        Public Flags As Integer 
      
        <FieldOffset(40)>
        Public FormatDescription As IntPtr ' i am correct here
     
        <FieldOffset(?)>
        Public SigCount As Integer
     
        <FieldOffset(?)>
        'Public SigSize As Integer

       
        <FieldOffset(?)>
        Public SigPattern As Byte
       
        <FieldOffset(?)>
        Public SigMask As IntPtr
    End Class

i need the complete informations.

Answer 1

This class already exists in .NET : System.Drawing.Imaging.ImageCodecInfo

Answer 2

i want that convertion for studying and learning.

Answer 3

As it exists, just copy-paste it from  Namespace System.Drawing.Imaging...

Answer 4

i want to learn how do the FieldOffset attribute works.

Answer 5

There is no need for 'StructLayout' or 'FieldOffset' - these can be useful for strict conversions of a C 'union', but are not related to the conversion of C++ 'class' or 'struct'.

The closest conversion I can give you for your C++ code is:

Public Class ImageCodecInfo
	Public Clsid As New CLSID()
	Public FormatID As New GUID()
	Public ReadOnly CodecName As String
	Public ReadOnly DllName As String
	Public ReadOnly FormatDescription As String
	Public ReadOnly FilenameExtension As String
	Public ReadOnly MimeType As String
	Public Flags As UInteger
	Public Version As UInteger
	Public SigCount As UInteger
	Public SigSize As UInteger
'C++ TO VB CONVERTER TODO TASK: VB does not have an equivalent to pointers to value types:
'ORIGINAL LINE: const Byte* SigPattern;
	Public ReadOnly SigPattern As Byte
'C++ TO VB CONVERTER TODO TASK: VB does not have an equivalent to pointers to value types:
'ORIGINAL LINE: const Byte* SigMask;
	Public ReadOnly SigMask As Byte
End Class

As you see the pointer to Byte is a problem.  In C++, the intent of pointers to Byte is unclear without examining the usage of these fields.  These may be arrays.

Even the conversion of 'WCHAR*' may be unclear without examining the usage, but these usually convert to strings.  Since they're 'const' pointers, the VB equivalent are ReadOnly fields.

C++ is the only major language where the declaration alone is often insufficient to determine the meaning - this is usually the case where pointers are involved.

---

Convert between VB, C#, C++, & Java (http://www.tangiblesoftwaresolutions.com)
Instant C# - VB to C# Converter
Instant VB - C# to VB Converter

Answer 6

i have encountered problem like this and i fixed it using the correct Offset of the FieldOffset attribute

Answer 7

new updates:

____________________________________________

fields.                                                 its offset.

____________________________________________

Clsid                                                        ?

FormatID                                                16

CodecName                                             32

DllName                                                  36

FormatDescription                                   40

FilenameExtension                                   44

MimeType                                                48

Version                                                    ?

SigCount                                                 56

SigSize                                                    60

SigPattern                                               68

SigMask                                                  72

Flags                                                       52

Answer 8

But why are you trying to re-invent the wheel ?

Copy-paste :

Public NotInheritable Class ImageCodecInfo
   Public Property Clsid As Guid
   Public Property CodecName As String
   Public Property DllName As String
   Public Property FilenameExtension As String
   Public Property Flags As ImageCodecFlags
   Public Property FormatDescription As String
   Public Property FormatID As Guid
   Public Property MimeType As String
   Public Property SignatureMasks As Byte()()
   Public Property SignaturePatterns As Byte()()
   Public Property Version As Integer
End Class

Answer 9

to Castorix31:

you are write