package com.github.quickhull3d;
/*
* #%L
* A Robust 3D Convex Hull Algorithm in Java
* %%
* Copyright (C) 2004 - 2014 John E. Lloyd
* %%
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* #L%
*/
/**
* Maintains a double-linked list of vertices for use by QuickHull3D
*/
class VertexList {
private Vertex head;
private Vertex tail;
/**
* Clears this list.
*/
public void clear() {
head = tail = null;
}
/**
* Adds a vertex to the end of this list.
*/
public void add(Vertex vtx) {
if (head == null) {
head = vtx;
} else {
tail.next = vtx;
}
vtx.prev = tail;
vtx.next = null;
tail = vtx;
}
/**
* Adds a chain of vertices to the end of this list.
*/
public void addAll(Vertex vtx) {
if (head == null) {
head = vtx;
} else {
tail.next = vtx;
}
vtx.prev = tail;
while (vtx.next != null) {
vtx = vtx.next;
}
tail = vtx;
}
/**
* Deletes a vertex from this list.
*/
public void delete(Vertex vtx) {
if (vtx.prev == null) {
head = vtx.next;
} else {
vtx.prev.next = vtx.next;
}
if (vtx.next == null) {
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) {
head = vtx2.next;
} else {
vtx1.prev.next = vtx2.next;
}
if (vtx2.next == null) {
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) {
head = vtx;
} else {
next.prev.next = vtx;
}
vtx.next = next;
next.prev = vtx;
}
/**
* Returns the first element in this list.
*/
public Vertex first() {
return head;
}
/**
* Returns true if this list is empty.
*/
public boolean isEmpty() {
return head == null;
}
}