private void ComputeSelect(Envelope searchEnv, int start0, int end0,
MonotoneChainSelectAction mcs)
{
Coordinate p0 = pts[start0];
Coordinate p1 = pts[end0];
mcs.tempEnv1.Initialize(p0, p1);
// terminating condition for the recursion
if (end0 - start0 == 1)
{
mcs.Select(this, start0);
return;
}
// nothing to do if the envelopes don't overlap
if (!searchEnv.Intersects(mcs.tempEnv1))
{
return;
}
// the chains overlap, so split each in half and iterate (binary search)
int mid = (start0 + end0) / 2;
// Assert: mid != start or end (since we checked above for end - start <= 1)
// check terminating conditions before recursing
if (start0 < mid)
{
ComputeSelect(searchEnv, start0, mid, mcs);
}
if (mid < end0)
{
ComputeSelect(searchEnv, mid, end0, mcs);
}
}
/// <summary>
/// Determine all the line segments in the chain whose envelopes overlap
/// the searchEnvelope, and process them
/// </summary>
public void Select(Envelope searchEnv, MonotoneChainSelectAction mcs)
{
ComputeSelect(searchEnv, start, end, mcs);
}