/*
* The JTS Topology Suite is a collection of Java classes that
* implement the fundamental operations required to validate a given
* geo-spatial data set to a known topological specification.
*
* Copyright (C) 2001 Vivid Solutions
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* For more information, contact:
*
* Vivid Solutions
* Suite #1A
* 2328 Government Street
* Victoria BC V8T 5G5
* Canada
*
* (250)385-6040
* www.vividsolutions.com
*/
package com.vividsolutions.jts.index.bintree;
import com.vividsolutions.jts.index.quadtree.DoubleBits;
/**
* A Key is a unique identifier for a node in a tree.
* It contains a lower-left point and a level number. The level number
* is the power of two for the size of the node envelope
*
* @version 1.7
*/
public class Key {
public static int computeLevel(Interval interval)
{
double dx = interval.getWidth();
//int level = BinaryPower.exponent(dx) + 1;
int level = DoubleBits.exponent(dx) + 1;
return level;
}
// the fields which make up the key
private double pt = 0.0;
private int level = 0;
// auxiliary data which is derived from the key for use in computation
private Interval interval;
public Key(Interval interval)
{
computeKey(interval);
}
public double getPoint() { return pt; }
public int getLevel() { return level; }
public Interval getInterval() { return interval; }
/**
* return a square envelope containing the argument envelope,
* whose extent is a power of two and which is based at a power of 2
*/
public void computeKey(Interval itemInterval)
{
level = computeLevel(itemInterval);
interval = new Interval();
computeInterval(level, itemInterval);
// MD - would be nice to have a non-iterative form of this algorithm
while (! interval.contains(itemInterval)) {
level += 1;
computeInterval(level, itemInterval);
}
}
private void computeInterval(int level, Interval itemInterval)
{
double size = DoubleBits.powerOf2(level);
//double size = pow2.power(level);
pt = Math.floor(itemInterval.getMin() / size) * size;
interval.init(pt, pt + size);
}
}