NodeBase.java

/*
 * 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 java.util.ArrayList;
import java.util.Collection;
import java.util.List;



/**
 * The base class for nodes in a {@link Bintree}.
 *
 * @version 1.7
 */
public abstract class NodeBase {

  /**
   * Returns the index of the subnode that wholely contains the given interval.
   * If none does, returns -1.
   */
  public static int getSubnodeIndex(Interval interval, double centre)
  {
    int subnodeIndex = -1;
    if (interval.min >= centre) subnodeIndex = 1;
    if (interval.max <= centre) subnodeIndex = 0;
    return subnodeIndex;
  }

  protected List items = new ArrayList();

  /**
   * subnodes are numbered as follows:
   *
   *  0 | 1
   */
  protected Node[] subnode = new Node[2];

  public NodeBase() {
  }

  public List getItems() { return items; }

  public void add(Object item)
  {
    items.add(item);
  }
  public List addAllItems(List items)
  {
    items.addAll(this.items);
    for (int i = 0; i < 2; i++) {
      if (subnode[i] != null) {
        subnode[i].addAllItems(items);
      }
    }
    return items;
  }
  protected abstract boolean isSearchMatch(Interval interval);

  /**
   * Adds items in the tree which potentially overlap the query interval
   * to the given collection.
   * If the query interval is <tt>null</tt>, add all items in the tree.
   * 
   * @param interval a query interval, or null
   * @param resultItems the candidate items found
   */
  public void addAllItemsFromOverlapping(Interval interval, Collection resultItems)
  {
    if (interval != null && ! isSearchMatch(interval))
      return;

    // some of these may not actually overlap - this is allowed by the bintree contract
    resultItems.addAll(items);

    if (subnode[0] != null) subnode[0].addAllItemsFromOverlapping(interval, resultItems);
    if (subnode[1] != null) subnode[1].addAllItemsFromOverlapping(interval, resultItems);
  }

  /**
   * Removes a single item from this subtree.
   *
   * @param itemInterval the envelope containing the item
   * @param item the item to remove
   * @return <code>true</code> if the item was found and removed
   */
  public boolean remove(Interval itemInterval, Object item)
  {
    // use interval to restrict nodes scanned
    if (! isSearchMatch(itemInterval))
      return false;

    boolean found = false;
    for (int i = 0; i < 2; i++) {
      if (subnode[i] != null) {
        found = subnode[i].remove(itemInterval, item);
        if (found) {
          // trim subtree if empty
          if (subnode[i].isPrunable())
            subnode[i] = null;
          break;
        }
      }
    }
    // if item was found lower down, don't need to search for it here
    if (found) return found;
    // otherwise, try and remove the item from the list of items in this node
    found = items.remove(item);
    return found;
  }

  public boolean isPrunable()
  {
    return ! (hasChildren() || hasItems());
  }

  public boolean hasChildren()
  {
    for (int i = 0; i < 2; i++) {
      if (subnode[i] != null)
        return true;
    }
    return false;
  }

  public boolean hasItems() { return ! items.isEmpty(); }

  int depth()
  {
    int maxSubDepth = 0;
    for (int i = 0; i < 2; i++) {
      if (subnode[i] != null) {
        int sqd = subnode[i].depth();
        if (sqd > maxSubDepth)
          maxSubDepth = sqd;
      }
    }
    return maxSubDepth + 1;
  }

  int size()
  {
    int subSize = 0;
    for (int i = 0; i < 2; i++) {
      if (subnode[i] != null) {
        subSize += subnode[i].size();
      }
    }
    return subSize + items.size();
  }

  int nodeSize()
  {
    int subSize = 0;
    for (int i = 0; i < 2; i++) {
      if (subnode[i] != null) {
        subSize += subnode[i].nodeSize();
      }
    }
    return subSize + 1;
  }

}