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+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/*
+ * Copyright (C) 2008 Apple Inc. All rights reserved.
+ *
+ * Based on Abstract AVL Tree Template v1.5 by Walt Karas
+ * <http://geocities.com/wkaras/gen_cpp/avl_tree.html>.
+ *
+ * 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.
+ * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ * its contributors may be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS 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 APPLE OR ITS 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.
+ */
+
+#ifndef CONTENT_BROWSER_INDEXED_DB_LEVELDB_AVLTREE_H_
+#define CONTENT_BROWSER_INDEXED_DB_LEVELDB_AVLTREE_H_
+
+#include "base/logging.h"
+#include "content/browser/indexed_db/leveldb/fixed_array.h"
+
+namespace content {
+
+// Here is the reference class for BSet.
+//
+// class BSet
+// {
+// public:
+//
+// class ANY_bitref
+// {
+// public:
+// operator bool ();
+// void operator = (bool b);
+// };
+//
+// // Does not have to initialize bits.
+// BSet();
+//
+// // Must return a valid value for index when 0 <= index < maxDepth
+// ANY_bitref operator [] (unsigned index);
+//
+// // Set all bits to 1.
+// void set();
+//
+// // Set all bits to 0.
+// void reset();
+// };
+
+template <unsigned maxDepth> class AVLTreeDefaultBSet {
+ public:
+ bool& operator[](unsigned i) {
+#if defined(ADDRESS_SANITIZER)
+ CHECK(i < maxDepth);
+#endif
+ return m_data[i];
+ }
+ void set() {
+ for (unsigned i = 0; i < maxDepth; ++i)
+ m_data[i] = true;
+ }
+ void reset() {
+ for (unsigned i = 0; i < maxDepth; ++i)
+ m_data[i] = false;
+ }
+
+ private:
+ FixedArray<bool, maxDepth> m_data;
+};
+
+// How to determine maxDepth:
+// d Minimum number of nodes
+// 2 2
+// 3 4
+// 4 7
+// 5 12
+// 6 20
+// 7 33
+// 8 54
+// 9 88
+// 10 143
+// 11 232
+// 12 376
+// 13 609
+// 14 986
+// 15 1,596
+// 16 2,583
+// 17 4,180
+// 18 6,764
+// 19 10,945
+// 20 17,710
+// 21 28,656
+// 22 46,367
+// 23 75,024
+// 24 121,392
+// 25 196,417
+// 26 317,810
+// 27 514,228
+// 28 832,039
+// 29 1,346,268
+// 30 2,178,308
+// 31 3,524,577
+// 32 5,702,886
+// 33 9,227,464
+// 34 14,930,351
+// 35 24,157,816
+// 36 39,088,168
+// 37 63,245,985
+// 38 102,334,154
+// 39 165,580,140
+// 40 267,914,295
+// 41 433,494,436
+// 42 701,408,732
+// 43 1,134,903,169
+// 44 1,836,311,902
+// 45 2,971,215,072
+//
+// E.g., if, in a particular instantiation, the maximum number of nodes in a
+// tree instance is 1,000,000, the maximum depth should be 28.
+// You pick 28 because MN(28) is 832,039, which is less than or equal to
+// 1,000,000, and MN(29) is 1,346,268, which is strictly greater than 1,000,000.
+
+template <class Abstractor,
+ unsigned maxDepth = 32,
+ class BSet = AVLTreeDefaultBSet<maxDepth> >
+class AVLTree {
+ public:
+ typedef typename Abstractor::key key;
+ typedef typename Abstractor::handle handle;
+ typedef typename Abstractor::size size;
+
+ enum SearchType {
+ EQUAL = 1,
+ LESS = 2,
+ GREATER = 4,
+ LESS_EQUAL = EQUAL | LESS,
+ GREATER_EQUAL = EQUAL | GREATER
+ };
+
+ Abstractor& abstractor() { return abs; }
+
+ inline handle insert(handle h);
+
+ inline handle search(key k, SearchType st = EQUAL);
+ inline handle search_least();
+ inline handle search_greatest();
+
+ inline handle remove(key k);
+
+ inline handle subst(handle new_node);
+
+ void purge() { abs.root = null(); }
+
+ bool is_empty() { return abs.root == null(); }
+
+ AVLTree() { abs.root = null(); }
+
+ class Iterator {
+ public:
+ // Initialize depth to invalid value, to indicate iterator is
+ // invalid. (Depth is zero-base.)
+ Iterator() { depth = ~0U; }
+
+ void start_iter(AVLTree& tree, key k, SearchType st = EQUAL) {
+ // Mask of high bit in an int.
+ const int kMaskHighBit = (int) ~((~(unsigned) 0) >> 1);
+
+ // Save the tree that we're going to iterate through in a
+ // member variable.
+ tree_ = &tree;
+
+ int cmp, target_cmp;
+ handle h = tree_->abs.root;
+ unsigned d = 0;
+
+ depth = ~0U;
+
+ if (h == null()) {
+ // Tree is empty.
+ return;
+ }
+
+ if (st & LESS) {
+ // Key can be greater than key of starting node.
+ target_cmp = 1;
+ } else if (st & GREATER) {
+ // Key can be less than key of starting node.
+ target_cmp = -1;
+ } else {
+ // Key must be same as key of starting node.
+ target_cmp = 0;
+ }
+
+ for (;;) {
+ cmp = cmp_k_n(k, h);
+ if (cmp == 0) {
+ if (st & EQUAL) {
+ // Equal node was sought and found as starting node.
+ depth = d;
+ break;
+ }
+ cmp = -target_cmp;
+ } else if (target_cmp != 0) {
+ if (!((cmp ^ target_cmp) & kMaskHighBit)) {
+ // cmp and target_cmp are both negative or both positive.
+ depth = d;
+ }
+ }
+ h = cmp < 0 ? get_lt(h) : get_gt(h);
+ if (h == null())
+ break;
+ branch[d] = cmp > 0;
+ path_h[d++] = h;
+ }
+ }
+
+ void start_iter_least(AVLTree& tree) {
+ tree_ = &tree;
+
+ handle h = tree_->abs.root;
+
+ depth = ~0U;
+
+ branch.reset();
+
+ while (h != null()) {
+ if (depth != ~0U)
+ path_h[depth] = h;
+ depth++;
+ h = get_lt(h);
+ }
+ }
+
+ void start_iter_greatest(AVLTree& tree) {
+ tree_ = &tree;
+
+ handle h = tree_->abs.root;
+
+ depth = ~0U;
+
+ branch.set();
+
+ while (h != null()) {
+ if (depth != ~0U)
+ path_h[depth] = h;
+ depth++;
+ h = get_gt(h);
+ }
+ }
+
+ handle operator*() {
+ if (depth == ~0U)
+ return null();
+
+ return depth == 0 ? tree_->abs.root : path_h[depth - 1];
+ }
+
+ void operator++() {
+ if (depth != ~0U) {
+ handle h = get_gt(**this);
+ if (h == null()) {
+ do {
+ if (depth == 0) {
+ depth = ~0U;
+ break;
+ }
+ depth--;
+ } while (branch[depth]);
+ } else {
+ branch[depth] = true;
+ path_h[depth++] = h;
+ for (;;) {
+ h = get_lt(h);
+ if (h == null())
+ break;
+ branch[depth] = false;
+ path_h[depth++] = h;
+ }
+ }
+ }
+ }
+
+ void operator--() {
+ if (depth != ~0U) {
+ handle h = get_lt(**this);
+ if (h == null()) {
+ do {
+ if (depth == 0) {
+ depth = ~0U;
+ break;
+ }
+ depth--;
+ } while (!branch[depth]);
+ } else {
+ branch[depth] = false;
+ path_h[depth++] = h;
+ for (;;) {
+ h = get_gt(h);
+ if (h == null())
+ break;
+ branch[depth] = true;
+ path_h[depth++] = h;
+ }
+ }
+ }
+ }
+
+ void operator++(int) { ++(*this); }
+ void operator--(int) { --(*this); }
+
+ protected:
+
+ // Tree being iterated over.
+ AVLTree* tree_;
+
+ // Records a path into the tree. If branch[n] is true, indicates
+ // take greater branch from the nth node in the path, otherwise
+ // take the less branch. branch[0] gives branch from root, and
+ // so on.
+ BSet branch;
+
+ // Zero-based depth of path into tree.
+ unsigned depth;
+
+ // Handles of nodes in path from root to current node (returned by *).
+ handle path_h[maxDepth - 1];
+
+ int cmp_k_n(key k, handle h) { return tree_->abs.compare_key_node(k, h); }
+ int cmp_n_n(handle h1, handle h2) {
+ return tree_->abs.compare_node_node(h1, h2);
+ }
+ handle get_lt(handle h) { return tree_->abs.get_less(h); }
+ handle get_gt(handle h) { return tree_->abs.get_greater(h); }
+ handle null() { return tree_->abs.null(); }
+ };
+
+ template <typename fwd_iter> bool build(fwd_iter p, size num_nodes) {
+ if (num_nodes == 0) {
+ abs.root = null();
+ return true;
+ }
+
+ // Gives path to subtree being built. If branch[N] is false, branch
+ // less from the node at depth N, if true branch greater.
+ BSet branch;
+
+ // If rem[N] is true, then for the current subtree at depth N, it's
+ // greater subtree has one more node than it's less subtree.
+ BSet rem;
+
+ // Depth of root node of current subtree.
+ unsigned depth = 0;
+
+ // Number of nodes in current subtree.
+ size num_sub = num_nodes;
+
+ // The algorithm relies on a stack of nodes whose less subtree has
+ // been built, but whose right subtree has not yet been built. The
+ // stack is implemented as linked list. The nodes are linked
+ // together by having the "greater" handle of a node set to the
+ // next node in the list. "less_parent" is the handle of the first
+ // node in the list.
+ handle less_parent = null();
+
+ // h is root of current subtree, child is one of its children.
+ handle h, child;
+
+ for (;;) {
+ while (num_sub > 2) {
+ // Subtract one for root of subtree.
+ num_sub--;
+ rem[depth] = !!(num_sub & 1);
+ branch[depth++] = false;
+ num_sub >>= 1;
+ }
+
+ if (num_sub == 2) {
+ // Build a subtree with two nodes, slanting to greater.
+ // I arbitrarily chose to always have the extra node in the
+ // greater subtree when there is an odd number of nodes to
+ // split between the two subtrees.
+
+ h = *p;
+ p++;
+ child = *p;
+ p++;
+ set_lt(child, null());
+ set_gt(child, null());
+ set_bf(child, 0);
+ set_gt(h, child);
+ set_lt(h, null());
+ set_bf(h, 1);
+ } else { // num_sub == 1
+ // Build a subtree with one node.
+
+ h = *p;
+ p++;
+ set_lt(h, null());
+ set_gt(h, null());
+ set_bf(h, 0);
+ }
+
+ while (depth) {
+ depth--;
+ if (!branch[depth]) {
+ // We've completed a less subtree.
+ break;
+ }
+
+ // We've completed a greater subtree, so attach it to
+ // its parent (that is less than it). We pop the parent
+ // off the stack of less parents.
+ child = h;
+ h = less_parent;
+ less_parent = get_gt(h);
+ set_gt(h, child);
+ // num_sub = 2 * (num_sub - rem[depth]) + rem[depth] + 1
+ num_sub <<= 1;
+ num_sub += 1 - rem[depth];
+ if (num_sub & (num_sub - 1)) {
+ // num_sub is not a power of 2
+ set_bf(h, 0);
+ } else {
+ // num_sub is a power of 2
+ set_bf(h, 1);
+ }
+ }
+
+ if (num_sub == num_nodes) {
+ // We've completed the full tree.
+ break;
+ }
+
+ // The subtree we've completed is the less subtree of the
+ // next node in the sequence.
+
+ child = h;
+ h = *p;
+ p++;
+ set_lt(h, child);
+
+ // Put h into stack of less parents.
+ set_gt(h, less_parent);
+ less_parent = h;
+
+ // Proceed to creating greater than subtree of h.
+ branch[depth] = true;
+ num_sub += rem[depth++];
+
+ } // end for (;;)
+
+ abs.root = h;
+
+ return true;
+ }
+
+ protected:
+
+ friend class Iterator;
+
+ // Create a class whose sole purpose is to take advantage of
+ // the "empty member" optimization.
+ struct abs_plus_root : public Abstractor {
+ // The handle of the root element in the AVL tree.
+ handle root;
+ };
+
+ abs_plus_root abs;
+
+ handle get_lt(handle h) { return abs.get_less(h); }
+ void set_lt(handle h, handle lh) { abs.set_less(h, lh); }
+
+ handle get_gt(handle h) { return abs.get_greater(h); }
+ void set_gt(handle h, handle gh) { abs.set_greater(h, gh); }
+
+ int get_bf(handle h) { return abs.get_balance_factor(h); }
+ void set_bf(handle h, int bf) { abs.set_balance_factor(h, bf); }
+
+ int cmp_k_n(key k, handle h) { return abs.compare_key_node(k, h); }
+ int cmp_n_n(handle h1, handle h2) { return abs.compare_node_node(h1, h2); }
+
+ handle null() { return abs.null(); }
+
+ private:
+
+ // Balances subtree, returns handle of root node of subtree
+ // after balancing.
+ handle balance(handle bal_h) {
+ handle deep_h;
+
+ // Either the "greater than" or the "less than" subtree of
+ // this node has to be 2 levels deeper (or else it wouldn't
+ // need balancing).
+
+ if (get_bf(bal_h) > 0) {
+ // "Greater than" subtree is deeper.
+
+ deep_h = get_gt(bal_h);
+
+ if (get_bf(deep_h) < 0) {
+ handle old_h = bal_h;
+ bal_h = get_lt(deep_h);
+
+ set_gt(old_h, get_lt(bal_h));
+ set_lt(deep_h, get_gt(bal_h));
+ set_lt(bal_h, old_h);
+ set_gt(bal_h, deep_h);
+
+ int bf = get_bf(bal_h);
+ if (bf != 0) {
+ if (bf > 0) {
+ set_bf(old_h, -1);
+ set_bf(deep_h, 0);
+ } else {
+ set_bf(deep_h, 1);
+ set_bf(old_h, 0);
+ }
+ set_bf(bal_h, 0);
+ } else {
+ set_bf(old_h, 0);
+ set_bf(deep_h, 0);
+ }
+ } else {
+ set_gt(bal_h, get_lt(deep_h));
+ set_lt(deep_h, bal_h);
+ if (get_bf(deep_h) == 0) {
+ set_bf(deep_h, -1);
+ set_bf(bal_h, 1);
+ } else {
+ set_bf(deep_h, 0);
+ set_bf(bal_h, 0);
+ }
+ bal_h = deep_h;
+ }
+ } else {
+ // "Less than" subtree is deeper.
+
+ deep_h = get_lt(bal_h);
+
+ if (get_bf(deep_h) > 0) {
+ handle old_h = bal_h;
+ bal_h = get_gt(deep_h);
+ set_lt(old_h, get_gt(bal_h));
+ set_gt(deep_h, get_lt(bal_h));
+ set_gt(bal_h, old_h);
+ set_lt(bal_h, deep_h);
+
+ int bf = get_bf(bal_h);
+ if (bf != 0) {
+ if (bf < 0) {
+ set_bf(old_h, 1);
+ set_bf(deep_h, 0);
+ } else {
+ set_bf(deep_h, -1);
+ set_bf(old_h, 0);
+ }
+ set_bf(bal_h, 0);
+ } else {
+ set_bf(old_h, 0);
+ set_bf(deep_h, 0);
+ }
+ } else {
+ set_lt(bal_h, get_gt(deep_h));
+ set_gt(deep_h, bal_h);
+ if (get_bf(deep_h) == 0) {
+ set_bf(deep_h, 1);
+ set_bf(bal_h, -1);
+ } else {
+ set_bf(deep_h, 0);
+ set_bf(bal_h, 0);
+ }
+ bal_h = deep_h;
+ }
+ }
+
+ return bal_h;
+ }
+
+};
+
+template <class Abstractor, unsigned maxDepth, class BSet>
+inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
+AVLTree<Abstractor, maxDepth, BSet>::insert(handle h) {
+ set_lt(h, null());
+ set_gt(h, null());
+ set_bf(h, 0);
+
+ if (abs.root == null()) {
+ abs.root = h;
+ } else {
+ // Last unbalanced node encountered in search for insertion point.
+ handle unbal = null();
+ // Parent of last unbalanced node.
+ handle parent_unbal = null();
+ // Balance factor of last unbalanced node.
+ int unbal_bf;
+
+ // Zero-based depth in tree.
+ unsigned depth = 0, unbal_depth = 0;
+
+ // Records a path into the tree. If branch[n] is true, indicates
+ // take greater branch from the nth node in the path, otherwise
+ // take the less branch. branch[0] gives branch from root, and
+ // so on.
+ BSet branch;
+
+ handle hh = abs.root;
+ handle parent = null();
+ int cmp;
+
+ do {
+ if (get_bf(hh) != 0) {
+ unbal = hh;
+ parent_unbal = parent;
+ unbal_depth = depth;
+ }
+ cmp = cmp_n_n(h, hh);
+ if (cmp == 0) {
+ // Duplicate key.
+ return hh;
+ }
+ parent = hh;
+ hh = cmp < 0 ? get_lt(hh) : get_gt(hh);
+ branch[depth++] = cmp > 0;
+ } while (hh != null());
+
+ // Add node to insert as leaf of tree.
+ if (cmp < 0)
+ set_lt(parent, h);
+ else
+ set_gt(parent, h);
+
+ depth = unbal_depth;
+
+ if (unbal == null()) {
+ hh = abs.root;
+ } else {
+ cmp = branch[depth++] ? 1 : -1;
+ unbal_bf = get_bf(unbal);
+ if (cmp < 0)
+ unbal_bf--;
+ else // cmp > 0
+ unbal_bf++;
+ hh = cmp < 0 ? get_lt(unbal) : get_gt(unbal);
+ if ((unbal_bf != -2) && (unbal_bf != 2)) {
+ // No rebalancing of tree is necessary.
+ set_bf(unbal, unbal_bf);
+ unbal = null();
+ }
+ }
+
+ if (hh != null()) {
+ while (h != hh) {
+ cmp = branch[depth++] ? 1 : -1;
+ if (cmp < 0) {
+ set_bf(hh, -1);
+ hh = get_lt(hh);
+ } else { // cmp > 0
+ set_bf(hh, 1);
+ hh = get_gt(hh);
+ }
+ }
+ }
+
+ if (unbal != null()) {
+ unbal = balance(unbal);
+ if (parent_unbal == null()) {
+ abs.root = unbal;
+ } else {
+ depth = unbal_depth - 1;
+ cmp = branch[depth] ? 1 : -1;
+ if (cmp < 0)
+ set_lt(parent_unbal, unbal);
+ else // cmp > 0
+ set_gt(parent_unbal, unbal);
+ }
+ }
+ }
+
+ return h;
+}
+
+template <class Abstractor, unsigned maxDepth, class BSet>
+inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
+AVLTree<Abstractor, maxDepth, BSet>::search(
+ key k,
+ typename AVLTree<Abstractor, maxDepth, BSet>::SearchType st) {
+ const int kMaskHighBit = (int) ~((~(unsigned) 0) >> 1);
+
+ int cmp, target_cmp;
+ handle match_h = null();
+ handle h = abs.root;
+
+ if (st & LESS)
+ target_cmp = 1;
+ else if (st & GREATER)
+ target_cmp = -1;
+ else
+ target_cmp = 0;
+
+ while (h != null()) {
+ cmp = cmp_k_n(k, h);
+ if (cmp == 0) {
+ if (st & EQUAL) {
+ match_h = h;
+ break;
+ }
+ cmp = -target_cmp;
+ } else if (target_cmp != 0) {
+ if (!((cmp ^ target_cmp) & kMaskHighBit)) {
+ // cmp and target_cmp are both positive or both negative.
+ match_h = h;
+ }
+ }
+ h = cmp < 0 ? get_lt(h) : get_gt(h);
+ }
+
+ return match_h;
+}
+
+template <class Abstractor, unsigned maxDepth, class BSet>
+inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
+AVLTree<Abstractor, maxDepth, BSet>::search_least() {
+ handle h = abs.root, parent = null();
+
+ while (h != null()) {
+ parent = h;
+ h = get_lt(h);
+ }
+
+ return parent;
+}
+
+template <class Abstractor, unsigned maxDepth, class BSet>
+inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
+AVLTree<Abstractor, maxDepth, BSet>::search_greatest() {
+ handle h = abs.root, parent = null();
+
+ while (h != null()) {
+ parent = h;
+ h = get_gt(h);
+ }
+
+ return parent;
+}
+
+template <class Abstractor, unsigned maxDepth, class BSet>
+inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
+AVLTree<Abstractor, maxDepth, BSet>::remove(key k) {
+ // Zero-based depth in tree.
+ unsigned depth = 0, rm_depth;
+
+ // Records a path into the tree. If branch[n] is true, indicates
+ // take greater branch from the nth node in the path, otherwise
+ // take the less branch. branch[0] gives branch from root, and
+ // so on.
+ BSet branch;
+
+ handle h = abs.root;
+ handle parent = null(), child;
+ int cmp, cmp_shortened_sub_with_path = 0;
+
+ for (;;) {
+ if (h == null()) {
+ // No node in tree with given key.
+ return null();
+ }
+ cmp = cmp_k_n(k, h);
+ if (cmp == 0) {
+ // Found node to remove.
+ break;
+ }
+ parent = h;
+ h = cmp < 0 ? get_lt(h) : get_gt(h);
+ branch[depth++] = cmp > 0;
+ cmp_shortened_sub_with_path = cmp;
+ }
+ handle rm = h;
+ handle parent_rm = parent;
+ rm_depth = depth;
+
+ // If the node to remove is not a leaf node, we need to get a
+ // leaf node, or a node with a single leaf as its child, to put
+ // in the place of the node to remove. We will get the greatest
+ // node in the less subtree (of the node to remove), or the least
+ // node in the greater subtree. We take the leaf node from the
+ // deeper subtree, if there is one.
+
+ if (get_bf(h) < 0) {
+ child = get_lt(h);
+ branch[depth] = false;
+ cmp = -1;
+ } else {
+ child = get_gt(h);
+ branch[depth] = true;
+ cmp = 1;
+ }
+ depth++;
+
+ if (child != null()) {
+ cmp = -cmp;
+ do {
+ parent = h;
+ h = child;
+ if (cmp < 0) {
+ child = get_lt(h);
+ branch[depth] = false;
+ } else {
+ child = get_gt(h);
+ branch[depth] = true;
+ }
+ depth++;
+ } while (child != null());
+
+ if (parent == rm) {
+ // Only went through do loop once. Deleted node will be replaced
+ // in the tree structure by one of its immediate children.
+ cmp_shortened_sub_with_path = -cmp;
+ } else {
+ cmp_shortened_sub_with_path = cmp;
+ }
+
+ // Get the handle of the opposite child, which may not be null.
+ child = cmp > 0 ? get_lt(h) : get_gt(h);
+ }
+
+ if (parent == null()) {
+ // There were only 1 or 2 nodes in this tree.
+ abs.root = child;
+ } else if (cmp_shortened_sub_with_path < 0) {
+ set_lt(parent, child);
+ } else {
+ set_gt(parent, child);
+ }
+
+ // "path" is the parent of the subtree being eliminated or reduced
+ // from a depth of 2 to 1. If "path" is the node to be removed, we
+ // set path to the node we're about to poke into the position of the
+ // node to be removed.
+ handle path = parent == rm ? h : parent;
+
+ if (h != rm) {
+ // Poke in the replacement for the node to be removed.
+ set_lt(h, get_lt(rm));
+ set_gt(h, get_gt(rm));
+ set_bf(h, get_bf(rm));
+ if (parent_rm == null()) {
+ abs.root = h;
+ } else {
+ depth = rm_depth - 1;
+ if (branch[depth])
+ set_gt(parent_rm, h);
+ else
+ set_lt(parent_rm, h);
+ }
+ }
+
+ if (path != null()) {
+ // Create a temporary linked list from the parent of the path node
+ // to the root node.
+ h = abs.root;
+ parent = null();
+ depth = 0;
+ while (h != path) {
+ if (branch[depth++]) {
+ child = get_gt(h);
+ set_gt(h, parent);
+ } else {
+ child = get_lt(h);
+ set_lt(h, parent);
+ }
+ parent = h;
+ h = child;
+ }
+
+ // Climb from the path node to the root node using the linked
+ // list, restoring the tree structure and rebalancing as necessary.
+ bool reduced_depth = true;
+ int bf;
+ cmp = cmp_shortened_sub_with_path;
+ for (;;) {
+ if (reduced_depth) {
+ bf = get_bf(h);
+ if (cmp < 0)
+ bf++;
+ else // cmp > 0
+ bf--;
+ if ((bf == -2) || (bf == 2)) {
+ h = balance(h);
+ bf = get_bf(h);
+ } else {
+ set_bf(h, bf);
+ }
+ reduced_depth = (bf == 0);
+ }
+ if (parent == null())
+ break;
+ child = h;
+ h = parent;
+ cmp = branch[--depth] ? 1 : -1;
+ if (cmp < 0) {
+ parent = get_lt(h);
+ set_lt(h, child);
+ } else {
+ parent = get_gt(h);
+ set_gt(h, child);
+ }
+ }
+ abs.root = h;
+ }
+
+ return rm;
+}
+
+template <class Abstractor, unsigned maxDepth, class BSet>
+inline typename AVLTree<Abstractor, maxDepth, BSet>::handle
+AVLTree<Abstractor, maxDepth, BSet>::subst(handle new_node) {
+ handle h = abs.root;
+ handle parent = null();
+ int cmp, last_cmp;
+
+ // Search for node already in tree with same key.
+ for (;;) {
+ if (h == null()) {
+ // No node in tree with same key as new node.
+ return null();
+ }
+ cmp = cmp_n_n(new_node, h);
+ if (cmp == 0) {
+ // Found the node to substitute new one for.
+ break;
+ }
+ last_cmp = cmp;
+ parent = h;
+ h = cmp < 0 ? get_lt(h) : get_gt(h);
+ }
+
+ // Copy tree housekeeping fields from node in tree to new node.
+ set_lt(new_node, get_lt(h));
+ set_gt(new_node, get_gt(h));
+ set_bf(new_node, get_bf(h));
+
+ if (parent == null()) {
+ // New node is also new root.
+ abs.root = new_node;
+ } else {
+ // Make parent point to new node.
+ if (last_cmp < 0)
+ set_lt(parent, new_node);
+ else
+ set_gt(parent, new_node);
+ }
+
+ return h;
+}
+
+} // namespace content
+
+#endif // CONTENT_BROWSER_INDEXED_DB_LEVELDB_AVLTREE_H_
generated by cgit v1.1 at 2025-03-31 07:12:07 +0000