Ho to extract an C array from Mex function (pointer to pointer to pointer ; double ***)

Dear Community,

I've got this problem where I need to interface an old C-algorithm into my new Matlab program.

This C-function needs as one input a double*** array. I allacoate some memory inside the mexFunction via:

        double ***rv_solve;
        rv_solve = (double ***)mxCalloc(X_SIZE, sizeof(double *));

        for (i = 0 ;  i < X_SIZE; i++) {
            rv_solve[i] = (double **)mxCalloc(Y_SIZE, sizeof(double *));

            for (j = 0; j < Y_SIZE; j++)
                rv_solve[i][j] = (double *)mxCalloc(Z_SIZE, sizeof(double *));
        }

The C-function manipulates this 3D array and I want this array back into my Matlab workspace.

The output gets assigned by

           rv_solve_out    = (double *)mxGetPr(plhs[2]);

How do I now associate double*** rv_solve with double* rv_solve_out ?

All I found on the web and the documantation is about 1-Dim arrays. I would love to use just 1-Dim arrays and use superindexing, but I need this C-function and it is complicated enough not to rewrite it for 1-Dim inputs.

And probably there is an easy solution, as most times, but I'm just to stupid to find or recognize it.

Thanks in advance.

Cheers Achim

Answer 1

[Achim]

I found a workaround, which was to obvious for me... Just transform the 3D array into a 1D array via superindexing.

 for (i = 0 ; i < dims[0] ; i++) {
        for (j = 0 ; j < dims[1] ; j++) {
            for (k = 0 ; k < dims[2] ; k++) {
                rv_solve_out[k*dims[0]*dims[1] + j*dims[1] + i]=rv_solve[i][j][k];
            }
        }
    }