H3Error h3SetToVertexGraph()

in h3_algos.c [1078:1120]

• 33 lines of code
• 7 McCabe index (conditional complexity)

H3Error h3SetToVertexGraph(const H3Index *h3Set, const int numHexes,
                           VertexGraph *graph) {
    CellBoundary vertices;
    LatLng *fromVtx;
    LatLng *toVtx;
    VertexNode *edge;
    if (numHexes < 1) {
        // We still need to init the graph, or calls to destroyVertexGraph will
        // fail
        initVertexGraph(graph, 0, 0);
        return E_SUCCESS;
    }
    int res = H3_GET_RESOLUTION(h3Set[0]);
    const int minBuckets = 6;
    // TODO: Better way to calculate/guess?
    int numBuckets = numHexes > minBuckets ? numHexes : minBuckets;
    initVertexGraph(graph, numBuckets, res);
    // Iterate through every hexagon
    for (int i = 0; i < numHexes; i++) {
        H3Error boundaryErr = H3_EXPORT(cellToBoundary)(h3Set[i], &vertices);
        if (boundaryErr) {
            // Destroy vertex graph as caller will not know to do so.
            destroyVertexGraph(graph);
            return boundaryErr;
        }
        // iterate through every edge
        for (int j = 0; j < vertices.numVerts; j++) {
            fromVtx = &vertices.verts[j];
            toVtx = &vertices.verts[(j + 1) % vertices.numVerts];
            // If we've seen this edge already, it will be reversed
            edge = findNodeForEdge(graph, toVtx, fromVtx);
            if (edge != NULL) {
                // If we've seen it, drop it. No edge is shared by more than 2
                // hexagons, so we'll never see it again.
                removeVertexNode(graph, edge);
            } else {
                // Add a new node for this edge
                addVertexNode(graph, fromVtx, toVtx);
            }
        }
    }
    return E_SUCCESS;
}