I have written a couple simple C functions I would like to be able to call from a perl program. I used h2xs to convert the header file into XS and everything worked fine, I was able to run make and make test. I started writing a few tests to make sure everything was working properly, but I ran into a problem, my program uses several C structs. For the most part h2xs seems to have done a good job of converting the structs. I can use all of the structs in Perl except for one which contains a pointer to an array of structs.

This is what my structs look like in C:

typedef struct {
    double longitude;
    double latitude;
} vertex_t;

typedef struct {
    vertex_t v1;
    vertex_t v2;
} edge_t;

typedef struct {
    int edge_count;
    edge_t *edges;
} polygon_t;

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So using the first two structs in Perl is intuitive I can create them using:

my $vertex1 = vertex_t->new();
my $vertex1_obj = $vertex1->_to_ptr();
$vertex1_obj->longitude(-123.1411461547873);
$vertex1_obj->latitude(49.29515081299949);

my $vertex2 = vertex_t->new();
my $vertex2_obj = $vertex2->_to_ptr();
$vertex2_obj->longitude(-123.1502664432874);
$vertex2_obj->latitude(49.29191311233952);

my $edge = edge_t->new();
my $edge_obj = $edge->_to_ptr();
$edge_obj->v1($vertex1);
$edge_obj->v2($vertex2);

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My problem is I cannot figure out how to create a polygon_t in perl, I can get this far: 

my $polygon = polygon_t->new();
my $polygon_obj = $polygon->_to_ptr();
$polygon_obj->edge_count(8);

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I think the XS generated for the polygon_t type probably has no idea that in my code I use edges_t *edges as an array of edge_t types not just a pointer to an edge_t type, because this works: $polygon_obj->edges($edge_obj) but what I really want to do is pass an array of edge objects from Perl. Can anyone tell me how to modify the XS to achieve this ?

In reply to Need help with Perl XS and C Structs by stilton

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