Question

I have the following struct in a C DLL:

struct foo
{
      double *x;
      short  *y;
}

The c# app that calls the DLL:

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)]
public class foo
{
        public ? x;
        public ? y;
}

I understand that I should use IntPtr if I have an int*, but can’t find equivalent for short* and double *.

On the C side, I am using the short * to allocate an array of shorts, the double * for array of doubles.

Answer 1

Actually, all unmanaged pointers in C# are represented using IntPtr. It’s called IntPtr not because it’s an analogue to int *, but rather because it is an integer of “pointer” size (in contrast to Int32 and Int64, which are integers of 32- and 64-bits respectively). Its size is platform dependent.

To get the value of x[0], for example, you’d do

double[] arr = new double[1];
Marshal.Copy(f.x, arr, 0, 1);

To read *y, you’d do

short val = Marshal.ReadInt16(f.y);