auto import from //depot/cupcake/@135843

1 files changed, 958 insertions, 0 deletions

diff --git a/JavaScriptCore/wtf/AVLTree.h b/JavaScriptCore/wtf/AVLTree.h
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+++ b/JavaScriptCore/wtf/AVLTree.h
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+/*
+ * 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 KJS_AVL_TREE_H_
+#define KJS_AVL_TREE_H_
+
+#include "Assertions.h"
+
+namespace JSC {
+
+// 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) { ASSERT(i < maxDepth); 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:
+    bool m_data[maxDepth];
+};
+
+// 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 MASK_HIGH_BIT = (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) & MASK_HIGH_BIT))
+                        // 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 MASK_HIGH_BIT = (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) & MASK_HIGH_BIT))
+                // 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;
+
+    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, false) : get_gt(h, false);
+    }
+
+    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, false));
+        set_gt(h, get_gt(rm, false));
+        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, false));
+    set_gt(new_node, get_gt(h, false));
+    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;
+}
+
+
+}
+
+#endif