Exploring faces and edges in an IGES file

Hello,

I've been trying to solve a problem for almost 2 months now and figured it was worth posting here to see if anyone could help.

I'm trying to write an IGES reader for a mesher. All I need to do is write functions to read the file, list all the surfaces and curves, do some parametric conversions, and then relate the curves to the surfaces.

To debug my code I've made a cube in solid works and saved it as an IGES file.

It's easiest to explain my problems with my code so here it goes...

class OCCT_FLITE
{
//This class contains functions to communicate between //OCCT and FLITE
private:
IGESControl_Reader reader;
Standard_Integer nshapes;
Standard_Integer ncurves;
Standard_Integer nsurfaces;

TopTools_IndexedMapOfShape edgemap, facemap;

public:

void OCCT_LoadGeom(Standard_CString filename)
{
//This function reads the geometry file and translates to //OCCT

//reads file
IFSelect_ReturnStatus stat = reader.ReadFile(filename);

//check file
IFSelect_PrintCount mode = IFSelect_ItemsByEntity;
reader.PrintCheckLoad(Standard_False,mode);

//Translate to OCCT
reader.TransferRoots();

//Store these in a single compound shape
TopoDS_Shape shape;
shape = reader.OneShape();
BRepTools::Clean(shape);
//Split into two indexed maps, edgemap and facemap
//edgemap(i) gives the ith edge
TopExp::MapShapes(shape,TopAbs_EDGE,edgemap); TopExp::MapShapes(shape,TopAbs_FACE,facemap);

};

The above function reads the file, then I have two functions (below) to report number of surfaces and curves...

Standard_Integer OCCT_GetNumCurves(void)
{
ncurves = edgemap.Extent();
return ncurves;
};

Standard_Integer OCCT_GetNumSurfaces(void)
{
nsurfaces = facemap.Extent();
return nsurfaces;
};

Problem 1: When I read in the cube file I get 6 surfaces (correct) but 24 edges. Really I only want the 12 edges defining the cube, I thought this may have been because each edge was being counted twice (two different orientations), but I don't think this should happen using IndexedMapOfShape?

In the meshing code we need to know which curves are part of given surface. I wrote this function to do this...

Standard_Integer* OCCT_GetSurfaceCurves(Standard_Integer surfNum, Standard_Integer &numCurves)

{
// Returns the number of curves in a suface and their identifiers in
// list

TopoDS_Face anFace = TopoDS::Face(facemap(surfNum));

// Create indexed map of edges
TopTools_IndexedMapOfShape localmap;
TopExp::MapShapes(anFace,TopAbs_EDGE,localmap);

numCurves = localmap.Extent();

Standard_Integer* list;
list = (Standard_Integer*) calloc((numCurves),sizeof(Standard_Integer ));

// Now need to find the indices of curves in this local //map in the
// global map

//NOTE: Irritatingly indices in C++ start at 0 and in //OPENCascade they
//start at 1

int count = 0;
for (count =0; count {

//Get the edge
TopoDS_Edge anEdge = TopoDS::Edge(edgemap(count+1));

list[count] = edgemap.FindIndex(anEdge);
//cout

};

return list;

};

Problem 2: Whatever value I give surfNum in the above function I always get 4 edges, and the indices returned are always 1,2,3,4

I have a feeling my problem is something to do with topology vs geometry, but I'm struggling to find documentation or examples to help me. If anyone could help I would really appricate it. I hope I've included enough information. I've attached my C++ source file to the post.