typemap for integer matrix?

[Aaron J Mackey]

I'm really not an XS guru, so I love the way I can do fast things in C
with Inline.  Here's a much simplified version of today's problem:

#!/usr/bin/perl

use Inline C => 'DATA';

$n = 100;                        # int i, n = 100;

                                 # int **matrix = calloc(n, sizeof(int *));
@matrix = ( [ (0) x $n ] ) x $n; # matrix[0] = calloc(n*n, sizeof(int));
                                 # for(i = 1 ; i < n ; i++) {
                                 #   matrix[i] = matrix[0] + (i * n);
                                 # }

# do other stuff to fill up @matrix with real, non-zero values.

invert(@matrix, $n);             # invert(&matrix, n)

__DATA__

void invert(int ***matrix, n) {

  int i, j;
  for(i = 0 ; i < n ; i++) {
    for(j = 0 ; j < i ; j++) {
      *matrix[i][j] = *matrix[j][i];
    }
  }
}

Now, obviously this doesn't work quite right ("Warning. No Inline C
functions bound to Perl") since I don't have a typemap for int *** ... but
is it worse than that?  Am I going to have to pollute my C code with lots
of SV* manipulations?

Thanks for what I'm sure is a FAQ (but isn't in the Cookbook - how do I
make my own typemaps?)

-Aaron