/*
* 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.bintree;
import org.locationtech.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);
}
}