bundles/common/org.eclipse.apogy.common.math.quickhull3d/src/org/eclipse/apogy/common/math/quickhull3d/VertexList.java

package org.eclipse.apogy.common.math.quickhull3d;

/********************************************************************************
 * Copyright (c) 2018 Agence spatiale canadienne / Canadian Space Agency
 * Contributors: Pierre Allard (Pierre.Allard@canada.ca), Regent L'Archeveque
 * (Regent.Larcheveque@canada.ca), Sebastien Gemme (Sebastien.Gemme@canada.ca),
 * Canadian Space Agency (CSA) - Initial API and implementation
 * 
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 1.0 which is available at
 * http://www.eclipse.org/legal/epl-v10.html.
 * 
 * SPDX-License-Identifier: EPL-1.0
 ********************************************************************************/

class VertexList {
	private Vertex head;
	private Vertex tail;

	/**
	 * Clears this list.
	 */
	public void clear() {
		this.head = this.tail = null;
	}

	/**
	 * Adds a vertex to the end of this list.
	 */
	public void add(Vertex vtx) {
		if (this.head == null) {
			this.head = vtx;
		} else {
			this.tail.next = vtx;
		}
		vtx.prev = this.tail;
		vtx.next = null;
		this.tail = vtx;
	}

	/**
	 * Adds a chain of vertices to the end of this list.
	 */
	public void addAll(Vertex vtx) {
		if (this.head == null) {
			this.head = vtx;
		} else {
			this.tail.next = vtx;
		}
		vtx.prev = this.tail;
		while (vtx.next != null) {
			vtx = vtx.next;
		}
		this.tail = vtx;
	}

	/**
	 * Deletes a vertex from this list.
	 */
	public void delete(Vertex vtx) {
		if (vtx.prev == null) {
			this.head = vtx.next;
		} else {
			vtx.prev.next = vtx.next;
		}
		if (vtx.next == null) {
			this.tail = vtx.prev;
		} else {
			vtx.next.prev = vtx.prev;
		}
	}

	/**
	 * Deletes a chain of vertices from this list.
	 */
	public void delete(Vertex vtx1, Vertex vtx2) {
		if (vtx1.prev == null) {
			this.head = vtx2.next;
		} else {
			vtx1.prev.next = vtx2.next;
		}
		if (vtx2.next == null) {
			this.tail = vtx1.prev;
		} else {
			vtx2.next.prev = vtx1.prev;
		}
	}

	/**
	 * Inserts a vertex into this list before another specificed vertex.
	 */
	public void insertBefore(Vertex vtx, Vertex next) {
		vtx.prev = next.prev;
		if (next.prev == null) {
			this.head = vtx;
		} else {
			next.prev.next = vtx;
		}
		vtx.next = next;
		next.prev = vtx;
	}

	/**
	 * Returns the first element in this list.
	 */
	public Vertex first() {
		return this.head;
	}

	/**
	 * Returns true if this list is empty.
	 */
	public boolean isEmpty() {
		return this.head == null;
	}
}