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gecko-dev/memory/build/rb.h
Mike Hommey a28cf3044f Bug 1613011 - Clear node links when removing it from a RedBlackTree. r=njn 
The assert that was added in bug 1610720 assumed the node links were
reset when a node is removed from a RedBlackTree, but that wasn't the
case. We can either remove the assert, or clear node links. We pick the
latter.

Differential Revision: https://phabricator.services.mozilla.com/D61515

--HG--
extra : moz-landing-system : lando
2020-02-04 02:05:19 +00:00

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
// Portions of this file were originally under the following license:
//
// Copyright (C) 2008 Jason Evans <jasone@FreeBSD.org>.
// All rights reserved.
//
// 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(s), this list of conditions and the following disclaimer
// unmodified other than the allowable addition of one or more
// copyright notices.
// 2. Redistributions in binary form must reproduce the above copyright
// notice(s), 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 HOLDER(S) ``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 HOLDER(S) 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.
//
// ****************************************************************************
//
// C++ template implementation of left-leaning red-black trees.
//
// All operations are done non-recursively. Parent pointers are not used, and
// color bits are stored in the least significant bit of right-child pointers,
// thus making node linkage as compact as is possible for red-black trees.
//
// The RedBlackTree template expects two type arguments: the type of the nodes,
// containing a RedBlackTreeNode, and a trait providing two methods:
// - a GetTreeNode method that returns a reference to the RedBlackTreeNode
// corresponding to a given node with the following signature:
// static RedBlackTreeNode<T>& GetTreeNode(T*)
// - a Compare function with the following signature:
// static Order Compare(T* aNode, T* aOther)
// ^^^^^
// or aKey
//
// Interpretation of comparision function return values:
//
// Order::eLess: aNode < aOther
// Order::eEqual: aNode == aOther
// Order::eGreater: aNode > aOther
//
// In all cases, the aNode or aKey argument is the first argument to the
// comparison function, which makes it possible to write comparison functions
// that treat the first argument specially.
//
// ***************************************************************************
#ifndef RB_H_
#define RB_H_
#include "mozilla/Alignment.h"
#include "mozilla/Assertions.h"
#include "Utils.h"
enum NodeColor {
Black = 0,
Red = 1,
};
// Node structure.
template <typename T>
class RedBlackTreeNode {
T* mLeft;
// The lowest bit is the color
T* mRightAndColor;
public:
T* Left() { return mLeft; }
void SetLeft(T* aValue) { mLeft = aValue; }
T* Right() {
return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(mRightAndColor) &
uintptr_t(~1));
}
void SetRight(T* aValue) {
mRightAndColor = reinterpret_cast<T*>(
(reinterpret_cast<uintptr_t>(aValue) & uintptr_t(~1)) | Color());
}
NodeColor Color() {
return static_cast<NodeColor>(reinterpret_cast<uintptr_t>(mRightAndColor) &
1);
}
bool IsBlack() { return Color() == NodeColor::Black; }
bool IsRed() { return Color() == NodeColor::Red; }
void SetColor(NodeColor aColor) {
mRightAndColor = reinterpret_cast<T*>(
(reinterpret_cast<uintptr_t>(mRightAndColor) & uintptr_t(~1)) | aColor);
}
};
// Tree structure.
template <typename T, typename Trait>
class RedBlackTree {
public:
void Init() { mRoot = nullptr; }
T* First(T* aStart = nullptr) { return First(TreeNode(aStart)).Get(); }
T* Last(T* aStart = nullptr) { return Last(TreeNode(aStart)).Get(); }
T* Next(T* aNode) { return Next(TreeNode(aNode)).Get(); }
T* Prev(T* aNode) { return Prev(TreeNode(aNode)).Get(); }
T* Search(T* aKey) { return Search(TreeNode(aKey)).Get(); }
// Find a match if it exists. Otherwise, find the next greater node, if one
// exists.
T* SearchOrNext(T* aKey) { return SearchOrNext(TreeNode(aKey)).Get(); }
void Insert(T* aNode) { Insert(TreeNode(aNode)); }
void Remove(T* aNode) { Remove(TreeNode(aNode)); }
// Helper class to avoid having all the tree traversal code further below
// have to use Trait::GetTreeNode and do manual null pointer checks, adding
// visual noise. Practically speaking TreeNode(nullptr) acts as a virtual
// sentinel, that loops back to itself for Left() and Right() and is always
// black.
class TreeNode {
public:
constexpr TreeNode() : mNode(nullptr) {}
MOZ_IMPLICIT TreeNode(T* aNode) : mNode(aNode) {}
TreeNode& operator=(TreeNode aOther) {
mNode = aOther.mNode;
return *this;
}
TreeNode Left() {
return TreeNode(mNode ? Trait::GetTreeNode(mNode).Left() : nullptr);
}
void SetLeft(TreeNode aNode) {
MOZ_RELEASE_ASSERT(mNode);
Trait::GetTreeNode(mNode).SetLeft(aNode.mNode);
}
TreeNode Right() {
return TreeNode(mNode ? Trait::GetTreeNode(mNode).Right() : nullptr);
}
void SetRight(TreeNode aNode) {
MOZ_RELEASE_ASSERT(mNode);
Trait::GetTreeNode(mNode).SetRight(aNode.mNode);
}
NodeColor Color() {
return mNode ? Trait::GetTreeNode(mNode).Color() : NodeColor::Black;
}
bool IsRed() { return Color() == NodeColor::Red; }
bool IsBlack() { return Color() == NodeColor::Black; }
void SetColor(NodeColor aColor) {
MOZ_RELEASE_ASSERT(mNode);
Trait::GetTreeNode(mNode).SetColor(aColor);
}
T* Get() { return mNode; }
MOZ_IMPLICIT operator bool() { return !!mNode; }
bool operator==(TreeNode& aOther) { return mNode == aOther.mNode; }
private:
T* mNode;
};
private:
// Ideally we'd use a TreeNode for mRoot, but we need RedBlackTree to stay
// a POD type to avoid a static initializer for gArenas.
T* mRoot;
TreeNode First(TreeNode aStart) {
TreeNode ret;
for (ret = aStart ? aStart : mRoot; ret.Left(); ret = ret.Left()) {
}
return ret;
}
TreeNode Last(TreeNode aStart) {
TreeNode ret;
for (ret = aStart ? aStart : mRoot; ret.Right(); ret = ret.Right()) {
}
return ret;
}
TreeNode Next(TreeNode aNode) {
TreeNode ret;
if (aNode.Right()) {
ret = First(aNode.Right());
} else {
TreeNode rbp_n_t = mRoot;
MOZ_ASSERT(rbp_n_t);
ret = nullptr;
while (true) {
Order rbp_n_cmp = Trait::Compare(aNode.Get(), rbp_n_t.Get());
if (rbp_n_cmp == Order::eLess) {
ret = rbp_n_t;
rbp_n_t = rbp_n_t.Left();
} else if (rbp_n_cmp == Order::eGreater) {
rbp_n_t = rbp_n_t.Right();
} else {
break;
}
MOZ_ASSERT(rbp_n_t);
}
}
return ret;
}
TreeNode Prev(TreeNode aNode) {
TreeNode ret;
if (aNode.Left()) {
ret = Last(aNode.Left());
} else {
TreeNode rbp_p_t = mRoot;
MOZ_ASSERT(rbp_p_t);
ret = nullptr;
while (true) {
Order rbp_p_cmp = Trait::Compare(aNode.Get(), rbp_p_t.Get());
if (rbp_p_cmp == Order::eLess) {
rbp_p_t = rbp_p_t.Left();
} else if (rbp_p_cmp == Order::eGreater) {
ret = rbp_p_t;
rbp_p_t = rbp_p_t.Right();
} else {
break;
}
MOZ_ASSERT(rbp_p_t);
}
}
return ret;
}
TreeNode Search(TreeNode aKey) {
TreeNode ret = mRoot;
Order rbp_se_cmp;
while (ret && (rbp_se_cmp = Trait::Compare(aKey.Get(), ret.Get())) !=
Order::eEqual) {
if (rbp_se_cmp == Order::eLess) {
ret = ret.Left();
} else {
ret = ret.Right();
}
}
return ret;
}
TreeNode SearchOrNext(TreeNode aKey) {
TreeNode ret = nullptr;
TreeNode rbp_ns_t = mRoot;
while (rbp_ns_t) {
Order rbp_ns_cmp = Trait::Compare(aKey.Get(), rbp_ns_t.Get());
if (rbp_ns_cmp == Order::eLess) {
ret = rbp_ns_t;
rbp_ns_t = rbp_ns_t.Left();
} else if (rbp_ns_cmp == Order::eGreater) {
rbp_ns_t = rbp_ns_t.Right();
} else {
ret = rbp_ns_t;
break;
}
}
return ret;
}
void Insert(TreeNode aNode) {
// rbp_i_s is only used as a placeholder for its RedBlackTreeNode. Use
// AlignedStorage2 to avoid running the TreeNode base class constructor.
mozilla::AlignedStorage2<T> rbp_i_s;
TreeNode rbp_i_g, rbp_i_p, rbp_i_c, rbp_i_t, rbp_i_u;
Order rbp_i_cmp = Order::eEqual;
rbp_i_g = nullptr;
rbp_i_p = rbp_i_s.addr();
rbp_i_p.SetLeft(mRoot);
rbp_i_p.SetRight(nullptr);
rbp_i_p.SetColor(NodeColor::Black);
rbp_i_c = mRoot;
// Iteratively search down the tree for the insertion point,
// splitting 4-nodes as they are encountered. At the end of each
// iteration, rbp_i_g->rbp_i_p->rbp_i_c is a 3-level path down
// the tree, assuming a sufficiently deep tree.
while (rbp_i_c) {
rbp_i_t = rbp_i_c.Left();
rbp_i_u = rbp_i_t.Left();
if (rbp_i_t.IsRed() && rbp_i_u.IsRed()) {
// rbp_i_c is the top of a logical 4-node, so split it.
// This iteration does not move down the tree, due to the
// disruptiveness of node splitting.
//
// Rotate right.
rbp_i_t = RotateRight(rbp_i_c);
// Pass red links up one level.
rbp_i_u = rbp_i_t.Left();
rbp_i_u.SetColor(NodeColor::Black);
if (rbp_i_p.Left() == rbp_i_c) {
rbp_i_p.SetLeft(rbp_i_t);
rbp_i_c = rbp_i_t;
} else {
// rbp_i_c was the right child of rbp_i_p, so rotate
// left in order to maintain the left-leaning invariant.
MOZ_ASSERT(rbp_i_p.Right() == rbp_i_c);
rbp_i_p.SetRight(rbp_i_t);
rbp_i_u = LeanLeft(rbp_i_p);
if (rbp_i_g.Left() == rbp_i_p) {
rbp_i_g.SetLeft(rbp_i_u);
} else {
MOZ_ASSERT(rbp_i_g.Right() == rbp_i_p);
rbp_i_g.SetRight(rbp_i_u);
}
rbp_i_p = rbp_i_u;
rbp_i_cmp = Trait::Compare(aNode.Get(), rbp_i_p.Get());
if (rbp_i_cmp == Order::eLess) {
rbp_i_c = rbp_i_p.Left();
} else {
MOZ_ASSERT(rbp_i_cmp == Order::eGreater);
rbp_i_c = rbp_i_p.Right();
}
continue;
}
}
rbp_i_g = rbp_i_p;
rbp_i_p = rbp_i_c;
rbp_i_cmp = Trait::Compare(aNode.Get(), rbp_i_c.Get());
if (rbp_i_cmp == Order::eLess) {
rbp_i_c = rbp_i_c.Left();
} else {
MOZ_ASSERT(rbp_i_cmp == Order::eGreater);
rbp_i_c = rbp_i_c.Right();
}
}
// rbp_i_p now refers to the node under which to insert.
aNode.SetLeft(nullptr);
aNode.SetRight(nullptr);
aNode.SetColor(NodeColor::Red);
if (rbp_i_cmp == Order::eGreater) {
rbp_i_p.SetRight(aNode);
rbp_i_t = LeanLeft(rbp_i_p);
if (rbp_i_g.Left() == rbp_i_p) {
rbp_i_g.SetLeft(rbp_i_t);
} else if (rbp_i_g.Right() == rbp_i_p) {
rbp_i_g.SetRight(rbp_i_t);
}
} else {
rbp_i_p.SetLeft(aNode);
}
// Update the root and make sure that it is black.
TreeNode root = TreeNode(rbp_i_s.addr()).Left();
root.SetColor(NodeColor::Black);
mRoot = root.Get();
}
void Remove(TreeNode aNode) {
// rbp_r_s is only used as a placeholder for its RedBlackTreeNode. Use
// AlignedStorage2 to avoid running the TreeNode base class constructor.
mozilla::AlignedStorage2<T> rbp_r_s;
TreeNode rbp_r_p, rbp_r_c, rbp_r_xp, rbp_r_t, rbp_r_u;
Order rbp_r_cmp;
rbp_r_p = TreeNode(rbp_r_s.addr());
rbp_r_p.SetLeft(mRoot);
rbp_r_p.SetRight(nullptr);
rbp_r_p.SetColor(NodeColor::Black);
rbp_r_c = mRoot;
rbp_r_xp = nullptr;
// Iterate down the tree, but always transform 2-nodes to 3- or
// 4-nodes in order to maintain the invariant that the current
// node is not a 2-node. This allows simple deletion once a leaf
// is reached. Handle the root specially though, since there may
// be no way to convert it from a 2-node to a 3-node.
rbp_r_cmp = Trait::Compare(aNode.Get(), rbp_r_c.Get());
if (rbp_r_cmp == Order::eLess) {
rbp_r_t = rbp_r_c.Left();
rbp_r_u = rbp_r_t.Left();
if (rbp_r_t.IsBlack() && rbp_r_u.IsBlack()) {
// Apply standard transform to prepare for left move.
rbp_r_t = MoveRedLeft(rbp_r_c);
rbp_r_t.SetColor(NodeColor::Black);
rbp_r_p.SetLeft(rbp_r_t);
rbp_r_c = rbp_r_t;
} else {
// Move left.
rbp_r_p = rbp_r_c;
rbp_r_c = rbp_r_c.Left();
}
} else {
if (rbp_r_cmp == Order::eEqual) {
MOZ_ASSERT(aNode == rbp_r_c);
if (!rbp_r_c.Right()) {
// Delete root node (which is also a leaf node).
if (rbp_r_c.Left()) {
rbp_r_t = LeanRight(rbp_r_c);
rbp_r_t.SetRight(nullptr);
} else {
rbp_r_t = nullptr;
}
rbp_r_p.SetLeft(rbp_r_t);
} else {
// This is the node we want to delete, but we will
// instead swap it with its successor and delete the
// successor. Record enough information to do the
// swap later. rbp_r_xp is the aNode's parent.
rbp_r_xp = rbp_r_p;
rbp_r_cmp = Order::eGreater; // Note that deletion is incomplete.
}
}
if (rbp_r_cmp == Order::eGreater) {
if (rbp_r_c.Right().Left().IsBlack()) {
rbp_r_t = rbp_r_c.Left();
if (rbp_r_t.IsRed()) {
// Standard transform.
rbp_r_t = MoveRedRight(rbp_r_c);
} else {
// Root-specific transform.
rbp_r_c.SetColor(NodeColor::Red);
rbp_r_u = rbp_r_t.Left();
if (rbp_r_u.IsRed()) {
rbp_r_u.SetColor(NodeColor::Black);
rbp_r_t = RotateRight(rbp_r_c);
rbp_r_u = RotateLeft(rbp_r_c);
rbp_r_t.SetRight(rbp_r_u);
} else {
rbp_r_t.SetColor(NodeColor::Red);
rbp_r_t = RotateLeft(rbp_r_c);
}
}
rbp_r_p.SetLeft(rbp_r_t);
rbp_r_c = rbp_r_t;
} else {
// Move right.
rbp_r_p = rbp_r_c;
rbp_r_c = rbp_r_c.Right();
}
}
}
if (rbp_r_cmp != Order::eEqual) {
while (true) {
MOZ_ASSERT(rbp_r_p);
rbp_r_cmp = Trait::Compare(aNode.Get(), rbp_r_c.Get());
if (rbp_r_cmp == Order::eLess) {
rbp_r_t = rbp_r_c.Left();
if (!rbp_r_t) {
// rbp_r_c now refers to the successor node to
// relocate, and rbp_r_xp/aNode refer to the
// context for the relocation.
if (rbp_r_xp.Left() == aNode) {
rbp_r_xp.SetLeft(rbp_r_c);
} else {
MOZ_ASSERT(rbp_r_xp.Right() == (aNode));
rbp_r_xp.SetRight(rbp_r_c);
}
rbp_r_c.SetLeft(aNode.Left());
rbp_r_c.SetRight(aNode.Right());
rbp_r_c.SetColor(aNode.Color());
if (rbp_r_p.Left() == rbp_r_c) {
rbp_r_p.SetLeft(nullptr);
} else {
MOZ_ASSERT(rbp_r_p.Right() == rbp_r_c);
rbp_r_p.SetRight(nullptr);
}
break;
}
rbp_r_u = rbp_r_t.Left();
if (rbp_r_t.IsBlack() && rbp_r_u.IsBlack()) {
rbp_r_t = MoveRedLeft(rbp_r_c);
if (rbp_r_p.Left() == rbp_r_c) {
rbp_r_p.SetLeft(rbp_r_t);
} else {
rbp_r_p.SetRight(rbp_r_t);
}
rbp_r_c = rbp_r_t;
} else {
rbp_r_p = rbp_r_c;
rbp_r_c = rbp_r_c.Left();
}
} else {
// Check whether to delete this node (it has to be
// the correct node and a leaf node).
if (rbp_r_cmp == Order::eEqual) {
MOZ_ASSERT(aNode == rbp_r_c);
if (!rbp_r_c.Right()) {
// Delete leaf node.
if (rbp_r_c.Left()) {
rbp_r_t = LeanRight(rbp_r_c);
rbp_r_t.SetRight(nullptr);
} else {
rbp_r_t = nullptr;
}
if (rbp_r_p.Left() == rbp_r_c) {
rbp_r_p.SetLeft(rbp_r_t);
} else {
rbp_r_p.SetRight(rbp_r_t);
}
break;
}
// This is the node we want to delete, but we
// will instead swap it with its successor
// and delete the successor. Record enough
// information to do the swap later.
// rbp_r_xp is aNode's parent.
rbp_r_xp = rbp_r_p;
}
rbp_r_t = rbp_r_c.Right();
rbp_r_u = rbp_r_t.Left();
if (rbp_r_u.IsBlack()) {
rbp_r_t = MoveRedRight(rbp_r_c);
if (rbp_r_p.Left() == rbp_r_c) {
rbp_r_p.SetLeft(rbp_r_t);
} else {
rbp_r_p.SetRight(rbp_r_t);
}
rbp_r_c = rbp_r_t;
} else {
rbp_r_p = rbp_r_c;
rbp_r_c = rbp_r_c.Right();
}
}
}
}
// Update root.
mRoot = TreeNode(rbp_r_s.addr()).Left().Get();
aNode.SetLeft(nullptr);
aNode.SetRight(nullptr);
aNode.SetColor(NodeColor::Black);
}
TreeNode RotateLeft(TreeNode aNode) {
TreeNode node = aNode.Right();
aNode.SetRight(node.Left());
node.SetLeft(aNode);
return node;
}
TreeNode RotateRight(TreeNode aNode) {
TreeNode node = aNode.Left();
aNode.SetLeft(node.Right());
node.SetRight(aNode);
return node;
}
TreeNode LeanLeft(TreeNode aNode) {
TreeNode node = RotateLeft(aNode);
NodeColor color = aNode.Color();
node.SetColor(color);
aNode.SetColor(NodeColor::Red);
return node;
}
TreeNode LeanRight(TreeNode aNode) {
TreeNode node = RotateRight(aNode);
NodeColor color = aNode.Color();
node.SetColor(color);
aNode.SetColor(NodeColor::Red);
return node;
}
TreeNode MoveRedLeft(TreeNode aNode) {
TreeNode node;
TreeNode rbp_mrl_t, rbp_mrl_u;
rbp_mrl_t = aNode.Left();
rbp_mrl_t.SetColor(NodeColor::Red);
rbp_mrl_t = aNode.Right();
rbp_mrl_u = rbp_mrl_t.Left();
if (rbp_mrl_u.IsRed()) {
rbp_mrl_u = RotateRight(rbp_mrl_t);
aNode.SetRight(rbp_mrl_u);
node = RotateLeft(aNode);
rbp_mrl_t = aNode.Right();
if (rbp_mrl_t.IsRed()) {
rbp_mrl_t.SetColor(NodeColor::Black);
aNode.SetColor(NodeColor::Red);
rbp_mrl_t = RotateLeft(aNode);
node.SetLeft(rbp_mrl_t);
} else {
aNode.SetColor(NodeColor::Black);
}
} else {
aNode.SetColor(NodeColor::Red);
node = RotateLeft(aNode);
}
return node;
}
TreeNode MoveRedRight(TreeNode aNode) {
TreeNode node;
TreeNode rbp_mrr_t;
rbp_mrr_t = aNode.Left();
if (rbp_mrr_t.IsRed()) {
TreeNode rbp_mrr_u, rbp_mrr_v;
rbp_mrr_u = rbp_mrr_t.Right();
rbp_mrr_v = rbp_mrr_u.Left();
if (rbp_mrr_v.IsRed()) {
rbp_mrr_u.SetColor(aNode.Color());
rbp_mrr_v.SetColor(NodeColor::Black);
rbp_mrr_u = RotateLeft(rbp_mrr_t);
aNode.SetLeft(rbp_mrr_u);
node = RotateRight(aNode);
rbp_mrr_t = RotateLeft(aNode);
node.SetRight(rbp_mrr_t);
} else {
rbp_mrr_t.SetColor(aNode.Color());
rbp_mrr_u.SetColor(NodeColor::Red);
node = RotateRight(aNode);
rbp_mrr_t = RotateLeft(aNode);
node.SetRight(rbp_mrr_t);
}
aNode.SetColor(NodeColor::Red);
} else {
rbp_mrr_t.SetColor(NodeColor::Red);
rbp_mrr_t = rbp_mrr_t.Left();
if (rbp_mrr_t.IsRed()) {
rbp_mrr_t.SetColor(NodeColor::Black);
node = RotateRight(aNode);
rbp_mrr_t = RotateLeft(aNode);
node.SetRight(rbp_mrr_t);
} else {
node = RotateLeft(aNode);
}
}
return node;
}
// The iterator simulates recursion via an array of pointers that store the
// current path. This is critical to performance, since a series of calls to
// rb_{next,prev}() would require time proportional to (n lg n), whereas this
// implementation only requires time proportional to (n).
//
// Since the iterator caches a path down the tree, any tree modification may
// cause the cached path to become invalid. Don't modify the tree during an
// iteration.
// Size the path arrays such that they are always large enough, even if a
// tree consumes all of memory. Since each node must contain a minimum of
// two pointers, there can never be more nodes than:
//
// 1 << ((sizeof(void*)<<3) - (log2(sizeof(void*))+1))
//
// Since the depth of a tree is limited to 3*lg(#nodes), the maximum depth
// is:
//
// (3 * ((sizeof(void*)<<3) - (log2(sizeof(void*))+1)))
//
// This works out to a maximum depth of 87 and 180 for 32- and 64-bit
// systems, respectively (approximately 348 and 1440 bytes, respectively).
public:
class Iterator {
TreeNode mPath[3 * ((sizeof(void*) << 3) - (LOG2(sizeof(void*)) + 1))];
unsigned mDepth;
public:
explicit Iterator(RedBlackTree<T, Trait>* aTree) : mDepth(0) {
// Initialize the path to contain the left spine.
if (aTree->mRoot) {
TreeNode node;
mPath[mDepth++] = aTree->mRoot;
while ((node = mPath[mDepth - 1].Left())) {
mPath[mDepth++] = node;
}
}
}
template <typename Iterator>
class Item {
Iterator* mIterator;
T* mItem;
public:
Item(Iterator* aIterator, T* aItem)
: mIterator(aIterator), mItem(aItem) {}
bool operator!=(const Item& aOther) const {
return (mIterator != aOther.mIterator) || (mItem != aOther.mItem);
}
T* operator*() const { return mItem; }
const Item& operator++() {
mItem = mIterator->Next();
return *this;
}
};
Item<Iterator> begin() {
return Item<Iterator>(this,
mDepth > 0 ? mPath[mDepth - 1].Get() : nullptr);
}
Item<Iterator> end() { return Item<Iterator>(this, nullptr); }
T* Next() {
TreeNode node;
if ((node = mPath[mDepth - 1].Right())) {
// The successor is the left-most node in the right subtree.
mPath[mDepth++] = node;
while ((node = mPath[mDepth - 1].Left())) {
mPath[mDepth++] = node;
}
} else {
// The successor is above the current node. Unwind until a
// left-leaning edge is removed from the path, of the path is empty.
for (mDepth--; mDepth > 0; mDepth--) {
if (mPath[mDepth - 1].Left() == mPath[mDepth]) {
break;
}
}
}
return mDepth > 0 ? mPath[mDepth - 1].Get() : nullptr;
}
};
Iterator iter() { return Iterator(this); }
};
#endif // RB_H_
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