Question

I have struct which is defined in c++ Win32 DLL like the following:

typedef struct matrix
{
  double** data;
  int m;
  int n;
} Matrix;

And there is a function:

Matrix getMatrix(void);

Matrix getMatrix()
{
    Matrix mat;

    mat.m = 2;
    mat.n = 2;

    mat.data    = (double**)  malloc (sizeof(double*) * 4);

    mat.data[0] = (double* )  malloc (sizeof(double) * 2);
    mat.data[1] = (double* )  malloc (sizeof(double) * 2);

    mat.data [0][0]=1;
    mat.data [0][1]=2;
    mat.data [1][0]=3;
    mat.data [1][1]=4;

    return mat;
}

How can I capture the return value of this function If I’m using P/Invoke from a C# Application

Answer 1

I am not sure if it works, but from memory: Declare data as IntPtr and use this
:

static double[][] FromNative (IntPtr data, int m,int n)
{
   var matrix=new double[m][];

   for(int i=0;i<m;i++)
   {
       matrix[i]=new double[n];
       Marshal.Copy(Marshal.ReadIntPtr(data),matrix[i],0,n);
       data =(IntPtr)(data.ToInt64()+IntPtr.Size);
   }

   return matrix;
}