将C ++结构转换为C＃结构

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

Answer 1

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.

Answer 2

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.