Converting c++ struct to c# struct

Question

Can anybody tell me how do I convert the following struct to c#

typedef struct DES_ks
{
    union
    {
        DES_cblock cblock;
        /* make sure things are correct size on machines with
         * 8 byte longs */
        DES_LONG deslong[2];
    } ks[16];
} DES_key_schedule

Well, you could tell us what type DES_cblock is. I'm assuming DES_LONG is a simple integral type, but it would be helpful if you could tell us what that is too. — Rook
– Rook, Commented Jun 24, 2012 at 14:51
Oops..sorry typedef unsigned char DES_cblock[8] is DES_cblock and DES_LONG is unsigned long — user1177586
– user1177586, Commented Jun 25, 2012 at 13:19

Michael Edenfield · Accepted Answer · 2012-06-24 14:55:42Z

You will need to look up the typedef's for DES_cblock and DES_LONG to translate this. However, to get you started, you'll want to read up on StructLayoutAttribute. The way to translate C unions into C# is to use an explicit layout structure:

[StructLayout(LayoutKind.Explicit)]
public struct DES_ks
{
  [FieldOffset(0)]
  public DES_cblock cblock;
  [FieldOffset(0)]
  [MarshalAs(UnmanagedType.ByValArray, SizeConst = 2)]
  public DES_LONG[] deslong;
}

Thanks to @Konrad for fixing my temporary insanity; because you want to produce a union, you need all of the fields to overlap in memory. This is achieved in C# by telling the compiler to lay them out at the same offset, in this case 0.

Antimony · Accepted Answer · 2012-06-24 14:54:22Z

0

C# does not have unions.. The closest you can come is using FieldOffset. However, if your struct isn't being passed directly to external functions, you're likely better off using a more OO approach. I'd suggest just creating a struct with arrays of both types and set the one you aren't using to null.

answered Jun 24, 2012 at 14:54

Antimony

39.8k13 gold badges103 silver badges115 bronze badges

2 Comments

Hans Passant Over a year ago

This is not accurate, [LayoutKind] works just fine in regular C# code as well.

Rook Over a year ago

I wouldn't go as far as saying it worked "fine", but it does work.

Collectives™ on Stack Overflow

Converting c++ struct to c# struct

2 Answers 2

Comments

2 Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

2 Comments

Related