H3Error _gridDiskDistancesInternal()

in src/h3lib/lib/algos.c [272:311]

• 28 lines of code
• 10 McCabe index (conditional complexity)

H3Error _gridDiskDistancesInternal(H3Index origin, int k, H3Index *out,
                                   int *distances, int64_t maxIdx, int curK) {
    // Put origin in the output array. out is used as a hash set.
    int64_t off = origin % maxIdx;
    while (out[off] != 0 && out[off] != origin) {
        off = (off + 1) % maxIdx;
    }

    // We either got a free slot in the hash set or hit a duplicate
    // We might need to process the duplicate anyways because we got
    // here on a longer path before.
    if (out[off] == origin && distances[off] <= curK) return E_SUCCESS;

    out[off] = origin;
    distances[off] = curK;

    // Base case: reached an index k away from the origin.
    if (curK >= k) return E_SUCCESS;

    // Recurse to all neighbors in no particular order.
    for (int i = 0; i < 6; i++) {
        int rotations = 0;
        H3Index nextNeighbor;
        H3Error neighborResult = h3NeighborRotations(origin, DIRECTIONS[i],
                                                     &rotations, &nextNeighbor);
        if (neighborResult != E_PENTAGON) {
            // E_PENTAGON is an expected case when trying to traverse off of
            // pentagons.
            if (neighborResult != E_SUCCESS) {
                return neighborResult;
            }
            neighborResult = _gridDiskDistancesInternal(
                nextNeighbor, k, out, distances, maxIdx, curK + 1);
            if (neighborResult) {
                return neighborResult;
            }
        }
    }
    return E_SUCCESS;
}