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395 lines
11 KiB
C++
395 lines
11 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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*
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* The contents of this file are subject to the Netscape Public
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* License Version 1.1 (the "License"); you may not use this file
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* except in compliance with the License. You may obtain a copy of
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* the License at http://www.mozilla.org/NPL/
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*
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* Software distributed under the License is distributed on an "AS
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* IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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* implied. See the License for the specific language governing
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* rights and limitations under the License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is Netscape
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* Communications Corporation. Portions created by Netscape are
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* Copyright (C) 1998 Netscape Communications Corporation. All
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* Rights Reserved.
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*
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* Contributor(s):
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*/
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#include "Tree.h"
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// ----------------------------------------------------------------------------
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// TreeNodeImpl
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//
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// Copy the link data from the src node to this node. On entry this node must not
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// be linked to a tree, while src must be linked to a tree; on exit the opposite
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// will be true.
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//
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// CAUTION: Do not call this directly; call TreeImpl::substitute or one of its
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// derivatives instead.
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//
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inline void TreeNodeImpl::move(TreeNodeImpl &src)
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{
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assert(!linked && src.linked);
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*this = src;
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src.unlink();
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}
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//
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// Let s be the subtree with this node as the root. Return the first (if right
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// is false) or last (if right is true) node of this subtree.
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//
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TreeNodeImpl &TreeNodeImpl::extremeNode(bool right)
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{
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TreeNodeImpl *p;
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TreeNodeImpl *subtree = this;
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while ((p = subtree->getChild(right)) != 0)
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subtree = p;
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return *subtree;
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}
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//
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// Return the node in the tree immediately before this node or nil if this
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// node is the first in the tree.
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//
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TreeNodeImpl *TreeNodeImpl::prev()
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{
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TreeNodeImpl *child = getChild(false);
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if (child)
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return &child->extremeNode(true);
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TreeNodeImpl *node = this;
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while (node && node->isLeft())
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node = node->getParent();
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if (node)
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node = node->getParent();
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return node;
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}
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//
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// Return the node in the tree immediately after this node or nil if this
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// node is the last in the tree.
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//
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TreeNodeImpl *TreeNodeImpl::next()
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{
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TreeNodeImpl *child = getChild(true);
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if (child)
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return &child->extremeNode(false);
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TreeNodeImpl *node = this;
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while (node && node->isRight())
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node = node->getParent();
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if (node)
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node = node->getParent();
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return node;
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}
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// ----------------------------------------------------------------------------
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// TreeImpl
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//
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// Link a node to its new parent on the right side (if right is true) or left side
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// if (right is false), replacing the parent's previous child link, if any, on that
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// side. A nil node indicates that the parent's previous child link should be cleared.
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// A nil parent represents the root, in which case right is ignored.
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//
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void TreeImpl::linkNode(TreeNodeImpl *node, TreeNodeImpl *parent, bool right)
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{
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if (node) {
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node->setParent(parent);
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if (parent)
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node->setRight(right);
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else
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node->setLeft();
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}
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if (parent)
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parent->setChild(right, node);
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else
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root = node;
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}
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//
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// Rotate a node pair to the right (if right is true) or left (if right is false)
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// without changing their colors. The given node starts at the parent of its
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// partner and ends as the child of its partner.
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//
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void TreeImpl::rotate(TreeNodeImpl &node, bool right)
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{
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TreeNodeImpl *partner = node.getChild(!right);
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assert(partner);
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linkNode(partner->getChild(right), &node, !right);
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linkNode(partner, node.getParent(), node.isRight());
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linkNode(&node, partner, right);
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}
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//
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// Attach a new red node and link it with the parent on the right side (if right is
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// true) or left side if (right is false). The given node must not be already linked
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// into a tree.
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// A nil parent represents the root.
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//
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void TreeImpl::addNode(TreeNodeImpl &node, TreeNodeImpl *parent, bool right)
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{
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assert(!(parent ? parent->getChild(right) : root));
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node.link();
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node.setRed();
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node.setChild(false, 0);
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node.setChild(true, 0);
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linkNode(&node, parent, right);
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nNodes++;
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}
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//
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// Make node be the right (if right is true) or left (if right is false) child of
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// parent, which must be in the tree. That child must be currently nil.
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// If where is nil, the tree must be currently empty, and in this case make node
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// be the new root, ignoring the value of right.
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// Rebalance the tree as needed. node should not be part of any tree on entry.
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//
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void TreeImpl::attach(TreeNodeImpl &node, TreeNodeImpl *parent, bool right)
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{
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addNode(node, parent, right);
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// Rebalance the tree to make sure that we don't have two red nodes in a row.
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TreeNodeImpl *p = &node;
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while (true) {
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// If we are the root, we make this node black and we're done.
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if (!parent) {
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p->setBlack();
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break;
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}
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// If we're black, we're done.
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if (parent->isBlack())
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break;
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// Otherwise we need a more complex rebalance.
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right = p->isRight();
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TreeNodeImpl *grandparent = parent->getParent();
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assert(grandparent);
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bool parentRight = parent->isRight();
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TreeNodeImpl *uncle = grandparent->getChild(!parentRight);
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if (uncle && uncle->isRed()) {
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parent->setBlack();
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uncle->setBlack();
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grandparent->setRed();
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p = grandparent;
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} else {
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if (right != parentRight) {
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rotate(*parent, parentRight);
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p = parent;
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parent = p->getParent();
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}
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parent->setBlack();
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grandparent->setRed();
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rotate(*grandparent, !parentRight);
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break;
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}
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parent = p->getParent();
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}
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}
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//
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// Insert node into the tree after node where. If where is nil, make node be the first
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// node in the tree. Rebalance the tree as needed.
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// node should not be part of any tree on entry.
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//
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void TreeImpl::insertAfter(TreeNodeImpl &node, TreeNodeImpl *where)
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{
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TreeNodeImpl *child = where ? where->getChild(true) : root;
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if (child)
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attach(node, &child->extremeNode(false), false);
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else
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attach(node, where, true);
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}
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//
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// Insert node into the tree before node where. If where is nil, make node be the last
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// node in the tree. Rebalance the tree as needed.
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// node should not be part of any tree on entry.
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//
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void TreeImpl::insertBefore(TreeNodeImpl &node, TreeNodeImpl *where)
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{
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TreeNodeImpl *child = where ? where->getChild(false) : root;
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if (child)
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attach(node, &child->extremeNode(true), true);
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else
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attach(node, where, false);
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}
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//
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// Remove the node from the tree, rebalancing the tree as needed.
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//
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void TreeImpl::remove(TreeNodeImpl &node)
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{
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// If the node has both children, exchange node with node's predecessor
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// in the tree ordering, which is guaranteed not to have a right child.
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if (node.getChild(false) && node.getChild(true)) {
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TreeNodeImpl &prev = node.getChild(false)->extremeNode(true);
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// Exchange the link fields of prev and node.
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TreeNodeImpl nodeCopy = node;
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TreeNodeImpl prevCopy = prev;
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node.setRed(prevCopy.isRed());
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prev.setRed(nodeCopy.isRed());
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if (prevCopy.getParent() == &node)
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linkNode(&node, &prev, false);
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else {
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linkNode(&node, prevCopy.getParent(), prevCopy.isRight());
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linkNode(nodeCopy.getChild(false), &prev, false);
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}
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linkNode(&prev, nodeCopy.getParent(), nodeCopy.isRight());
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linkNode(nodeCopy.getChild(true), &prev, true);
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linkNode(prevCopy.getChild(false), &node, false);
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node.setChild(true, 0);
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// Quiet the assert about a linked node being deleted.
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nodeCopy.unlink();
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prevCopy.unlink();
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}
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// At this point node has no more than one child. Let p be that child
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// or nil if node has no children.
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assert(!(node.getChild(false) && node.getChild(true)));
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TreeNodeImpl *p = node.getChild(false);
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if (!p)
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p = node.getChild(true);
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// Link node's child directly to node's parent, bypassing node.
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bool red = node.isRed();
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bool right = node.isRight();
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TreeNodeImpl *parent = node.getParent();
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linkNode(p, parent, right);
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nNodes--;
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node.unlink();
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// If we just deleted a black node, we need to rebalance the tree.
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if (!red) {
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while (!p || p->isBlack()) {
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if (!parent)
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break;
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TreeNodeImpl *brother = parent->getChild(!right);
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assert(brother);
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if (brother->isRed()) {
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brother->setRed(parent->isRed());
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parent->setRed();
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rotate(*parent, right);
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brother = parent->getChild(!right);
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}
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TreeNodeImpl *cousin = brother->getChild(!right);
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if (cousin && cousin->isRed()) {
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cousin->setBlack();
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brother->setRed(parent->isRed());
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parent->setBlack();
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rotate(*parent, right);
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break;
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}
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cousin = brother->getChild(right);
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if (cousin && cousin->isRed()) {
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brother->setRed();
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cousin->setBlack();
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rotate(*brother, !right);
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} else {
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brother->setRed();
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p = parent;
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right = p->isRight();
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parent = p->getParent();
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}
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}
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if (p)
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p->setBlack();
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}
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}
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//
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// Splice newNode into oldNode's position in the tree. oldNode is removed from
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// the tree.
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//
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void TreeImpl::substitute(TreeNodeImpl &newNode, TreeNodeImpl &oldNode)
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{
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if (&newNode != &oldNode) {
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newNode.move(oldNode);
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// Change the parent's pointer from oldNode to newNode
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TreeNodeImpl *parent = newNode.getParent();
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if (parent)
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parent->setChild(newNode.isRight(), &newNode);
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else
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root = &newNode;
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// Change the children's parent pointers from oldNode to newNode
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TreeNodeImpl *child = newNode.getChild(false);
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if (child)
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child->setParent(&newNode);
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child = newNode.getChild(true);
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if (child)
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child->setParent(&newNode);
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}
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}
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#ifdef DEBUG
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//
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// Verify the integrity of a subtree rooted at the given node. Assert if
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// anything wrong is found.
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// Increment nNodes by the number of nodes encountered in the subtree.
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// Return the number of non-nil black nodes encountered on any path from node
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// to a leaf (this number must be constant regardless of the path and leaf
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// chosen) in blackDepth. Return true if this node is red.
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//
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bool TreeImpl::verifySubtree(TreeNodeImpl *node, TreeNodeImpl *parent, bool rightChild, Uint32 &nNodes, Uint32 &blackDepth)
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{
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if (node) {
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nNodes++;
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assert(node->getParent() == parent && node->isRight() == rightChild);
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Uint32 leftChildDepth;
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Uint32 rightChildDepth;
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bool red = node->isRed();
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bool hasRedChild = verifySubtree(node->getChild(false), node, false, nNodes, leftChildDepth);
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hasRedChild |= verifySubtree(node->getChild(true), node, true, nNodes, rightChildDepth);
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assert(leftChildDepth == rightChildDepth);
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if (red)
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assert(!hasRedChild);
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else
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leftChildDepth++;
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blackDepth = leftChildDepth;
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return red;
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} else {
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blackDepth = 0;
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return false;
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}
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}
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//
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// Verify that the tree is internally consistent. Assert if anything wrong is found.
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//
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void TreeImpl::verify() const
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{
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Uint32 n = 0;
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Uint32 blackDepth;
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bool rootIsRed = verifySubtree(root, 0, false, n, blackDepth);
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assert(!rootIsRed && n == nNodes);
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}
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#endif
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