VectorGridXZ.java

package org.osm2world.core.math;

import static java.lang.Math.*;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

import org.apache.commons.collections.iterators.ArrayIterator;
import org.apache.commons.collections.iterators.IteratorChain;

/**
 * regular grid of {@link VectorXZ}.
 * 
 * Individual points are created only when they are first accessed,
 * so no memory is wasted on unused points.
 */
public class VectorGridXZ implements Iterable<VectorXZ> {
	
	private static final VectorXZ[][] EMPTY_GRID = new VectorXZ[0][0];
	
	private final VectorXZ[][] grid;
	
	private final double sampleDistance;
	
	private final int startX;
	private final int startZ;

	/**
	 * returns a regular grid of points within a bounding box.
	 */
	public VectorGridXZ(AxisAlignedBoundingBoxXZ box, double sampleDistance) {
		
		this.sampleDistance = sampleDistance;
		
		startX = (int)ceil((box.minX + 0.01) / sampleDistance);
		startZ = (int)ceil((box.minZ + 0.01) / sampleDistance);
		
		int endX = (int)floor((box.maxX - 0.01) / sampleDistance);
		int endZ = (int)floor((box.maxZ - 0.01) / sampleDistance);
		
		int numSamplesX = endX - startX + 1;
		int numSamplesZ = endZ - startZ + 1;
		
		if (numSamplesX <= 0 || numSamplesZ <= 0) {
			
			grid = EMPTY_GRID;
			
		} else {
			
			grid = new VectorXZ[numSamplesX][numSamplesZ];
			
		}
		
	}
	
	public int size() {
		return sizeX() * sizeZ();
	}
	
	public int sizeX() {
		return grid.length;
	}
	
	public int sizeZ() {
		return grid == EMPTY_GRID ? 0 : grid[0].length;
	}
	
	public boolean isEmpty() {
		return grid == EMPTY_GRID;
	}

	public VectorXZ get(int indexX, int indexZ) {
		
		createIfNecessary(indexX, indexZ);
		
		return grid[indexX][indexZ];
		
	}

	@Override
	@SuppressWarnings("unchecked")
	public Iterator<VectorXZ> iterator() {
		
		if (isEmpty()) {
		    return Collections.EMPTY_LIST.iterator();
		} else {
			
			List<Iterator<VectorXZ>> columnIterators =
					new ArrayList<Iterator<VectorXZ>>(sizeX());
			
			for (int x = 0; x < sizeX(); x++) {
				
				for (int z = 0; z < sizeZ(); z++) {
					createIfNecessary(x, z);
				}
				
				columnIterators.add(new ArrayIterator(grid[x]));
				
			}
			
			return new IteratorChain(columnIterators);
			
		}
		
	}
	
	private void createIfNecessary(int indexX, int indexZ) {
		
		if (grid[indexX][indexZ] == null) {
			
			grid[indexX][indexZ] = new VectorXZ(
					(startX + indexX) * sampleDistance,
					(startZ + indexZ) * sampleDistance);
			
		}
		
	}
	
	@Override
	public String toString() {
		
		if (isEmpty()) {
			
			return "{0*0}";
			
		} else {
			
			return "{" + sizeX() + "*" + sizeZ() + ", start " + get(0,0) + "}";
			
		}
		
	}
	
}