/*
* Copyright (c) 2016 Vivid Solutions.
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
*
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.locationtech.jts.index.sweepline;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* A sweepline implements a sorted index on a set of intervals.
* It is used to compute all overlaps between the interval in the index.
*
* @version 1.7
*/
public class SweepLineIndex {
List events = new ArrayList();
private boolean indexBuilt;
// statistics information
private int nOverlaps;
public SweepLineIndex() {
}
public void add(SweepLineInterval sweepInt)
{
SweepLineEvent insertEvent = new SweepLineEvent(sweepInt.getMin(), null, sweepInt);
events.add(insertEvent);
events.add(new SweepLineEvent(sweepInt.getMax(), insertEvent, sweepInt));
}
/**
* Because Delete Events have a link to their corresponding Insert event,
* it is possible to compute exactly the range of events which must be
* compared to a given Insert event object.
*/
private void buildIndex()
{
if (indexBuilt) return;
Collections.sort(events);
for (int i = 0; i < events.size(); i++ )
{
SweepLineEvent ev = (SweepLineEvent) events.get(i);
if (ev.isDelete()) {
ev.getInsertEvent().setDeleteEventIndex(i);
}
}
indexBuilt = true;
}
public void computeOverlaps(SweepLineOverlapAction action)
{
nOverlaps = 0;
buildIndex();
for (int i = 0; i < events.size(); i++ )
{
SweepLineEvent ev = (SweepLineEvent) events.get(i);
if (ev.isInsert()) {
processOverlaps(i, ev.getDeleteEventIndex(), ev.getInterval(), action);
}
}
}
private void processOverlaps(int start, int end, SweepLineInterval s0, SweepLineOverlapAction action)
{
/**
* Since we might need to test for self-intersections,
* include current insert event object in list of event objects to test.
* Last index can be skipped, because it must be a Delete event.
*/
for (int i = start; i < end; i++ ) {
SweepLineEvent ev = (SweepLineEvent) events.get(i);
if (ev.isInsert()) {
SweepLineInterval s1 = ev.getInterval();
action.overlap(s0, s1);
nOverlaps++;
}
}
}
}