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/*
* 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.geom;
import java.util.Comparator;
/**
* Compares two {@link CoordinateSequence}s.
* For sequences of the same dimension, the ordering is lexicographic.
* Otherwise, lower dimensions are sorted before higher.
* The dimensions compared can be limited; if this is done
* ordinate dimensions above the limit will not be compared.
*
* If different behaviour is required for comparing size, dimension, or
* coordinate values, any or all methods can be overridden.
*
*/
public class CoordinateSequenceComparator
implements Comparator
{
/**
* Compare two doubles, allowing for NaN values.
* NaN is treated as being less than any valid number.
*
* @param a a double
* @param b a double
* @return -1, 0, or 1 depending on whether a is less than, equal to or greater than b
*/
public static int compare(double a, double b)
{
if (a < b) return -1;
if (a > b) return 1;
if (Double.isNaN(a)) {
if (Double.isNaN(b)) return 0;
return -1;
}
if (Double.isNaN(b)) return 1;
return 0;
}
/**
* The number of dimensions to test
*/
protected int dimensionLimit;
/**
* Creates a comparator which will test all dimensions.
*/
public CoordinateSequenceComparator()
{
dimensionLimit = Integer.MAX_VALUE;
}
/**
* Creates a comparator which will test only the specified number of dimensions.
*
* @param dimensionLimit the number of dimensions to test
*/
public CoordinateSequenceComparator(int dimensionLimit)
{
this.dimensionLimit = dimensionLimit;
}
/**
* Compares two {@link CoordinateSequence}s for relative order.
*
* @param o1 a {@link CoordinateSequence}
* @param o2 a {@link CoordinateSequence}
* @return -1, 0, or 1 depending on whether o1 is less than, equal to, or greater than o2
*/
public int compare(Object o1, Object o2)
{
CoordinateSequence s1 = (CoordinateSequence) o1;
CoordinateSequence s2 = (CoordinateSequence) o2;
int size1 = s1.size();
int size2 = s2.size();
int dim1 = s1.getDimension();
int dim2 = s2.getDimension();
int minDim = dim1;
if (dim2 < minDim)
minDim = dim2;
boolean dimLimited = false;
if (dimensionLimit <= minDim) {
minDim = dimensionLimit;
dimLimited = true;
}
// lower dimension is less than higher
if (! dimLimited) {
if (dim1 < dim2) return -1;
if (dim1 > dim2) return 1;
}
// lexicographic ordering of point sequences
int i = 0;
while (i < size1 && i < size2) {
int ptComp = compareCoordinate(s1, s2, i, minDim);
if (ptComp != 0) return ptComp;
i++;
}
if (i < size1) return 1;
if (i < size2) return -1;
return 0;
}
/**
* Compares the same coordinate of two {@link CoordinateSequence}s
* along the given number of dimensions.
*
* @param s1 a {@link CoordinateSequence}
* @param s2 a {@link CoordinateSequence}
* @param i the index of the coordinate to test
* @param dimension the number of dimensiosn to test
* @return -1, 0, or 1 depending on whether s1[i] is less than, equal to, or greater than s2[i]
*/
protected int compareCoordinate(CoordinateSequence s1, CoordinateSequence s2, int i, int dimension)
{
for (int d = 0; d < dimension; d++) {
double ord1 = s1.getOrdinate(i, d);
double ord2 = s2.getOrdinate(i, d);
int comp = compare(ord1, ord2);
if (comp != 0) return comp;
}
return 0;
}
}