mariadb/ft/omt-tmpl.h

/* -*- mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
// vim: ft=cpp:expandtab:ts=8:sw=4:softtabstop=4:
#if !defined(OMT_TMPL_H)
#define OMT_TMPL_H

#ident "$Id$"
#ident "Copyright (c) 2007-2012 Tokutek Inc.  All rights reserved."
#ident "The technology is licensed by the Massachusetts Institute of Technology, Rutgers State University of New Jersey, and the Research Foundation of State University of New York at Stony Brook under United States of America Serial No. 11/760379 and to the patents and/or patent applications resulting from it."

#include <toku_portability.h>
#include <toku_assert.h>
#include <memory.h>
#include <stdint.h>
#include <stdbool.h>
#include <errno.h>
#include <db.h>

#if defined(__ICL) || defined(__ICC) || defined(__clang__)
# define static_assert(foo, bar) // nothing
#else
# include <type_traits>
#endif

namespace toku {

template<typename omtdata_t,
         typename omtdataout_t=omtdata_t>
struct omt {
    /**
     * 
     */
    void create(void)
    {
        this->create_internal(2);
    }

    /**
     * 
     */
    void create_no_array(void)
    {
        this->create_internal_no_array(0);
    }

    /**
     * 
     */
    void create_from_sorted_array(const omtdata_t *const values, const uint32_t numvalues)
    {
        this->create_internal(numvalues);
        memcpy(this->d.a.values, values, numvalues * (sizeof values[0]));
        this->d.a.num_values = numvalues;
    }

    /**
     * 
     */
    __attribute__((nonnull))
    void create_steal_sorted_array(omtdata_t **const values, const uint32_t numvalues, const uint32_t new_capacity)
    {
        invariant_notnull(values);
        this->create_internal_no_array(new_capacity);
        this->d.a.num_values = numvalues;
        this->d.a.values = *values;
        *values = nullptr;
    }

    /**
     * 
     */
    __attribute__((nonnull))
    int split_at(omt *const newomt, const uint32_t idx) {
        invariant_notnull(newomt);
        if (idx > this->size()) { return EINVAL; }
        this->convert_to_array();
        const uint32_t newsize = this->size() - idx;
        newomt->create_from_sorted_array(&this->d.a.values[this->d.a.start_idx + idx], newsize);
        this->d.a.num_values = idx;
        this->maybe_resize_array();
        return 0;
    }

    /**
     * 
     */
    __attribute__((nonnull))
    void merge(omt *const leftomt, omt *const rightomt) {
        invariant_notnull(leftomt);
        invariant_notnull(rightomt);
        const uint32_t leftsize = leftomt->size();
        const uint32_t rightsize = rightomt->size();
        const uint32_t newsize = leftsize + rightsize;

        if (leftomt->is_array) {
            if (leftomt->capacity - (leftomt->d.a.start_idx + leftomt->d.a.num_values) >= rightsize) {
                this->create_steal_sorted_array(leftomt->d.a.values, leftomt->d.a.num_values, leftomt->capacity);
                this->d.a.start_idx = leftomt->d.a.start_idx;
            } else {
                this->create_internal(newsize);
                memcpy(&this->d.a.values[0],
                       &leftomt->d.a.values[leftomt->d.a.start_idx],
                       leftomt->d.a.num_values * (sizeof this->d.a.values[0]));
            }
        } else {
            this->create_internal(newsize);
            leftomt->fill_array_with_subtree_values(&this->d.a.values[0], leftomt->d.t.root);
        }
        leftomt->destroy();
        this->d.a.num_values = leftsize;

        if (rightomt->is_array) {
            memcpy(&this->d.a.values[this->d.a.start_idx + this->d.a.num_values],
                   &rightomt->d.a.values[rightomt->d.a.start_idx],
                   rightomt->d.a.num_values * (sizeof this->d.a.values[0]));
        } else {
            rightomt->fill_array_with_subtree_values(&this->d.a.values[this->d.a.start_idx + this->d.a.num_values],
                                                     rightomt->d.t.root);
        }
        rightomt->destroy();
        this->d.a.num_values += rightsize;
        invariant(this->size() == newsize);
    }

    /**
     * 
     */
    void clone(const omt &src)
    {
        this->create_internal(src.size());
        if (src.is_array) {
            memcpy(&this->d.a.values[0], &src.d.a.values[src.d.a.start_idx], src.d.a.num_values * (sizeof this->d.a.values[0]));
        } else {
            src.fill_array_with_subtree_values(&this->d.a.values[0], src.d.t.root);
        }
        this->d.a.num_values = src.size();
    }

    /**
     * 
     */
    void deep_clone(const omt &src)
    {
        this->create_internal(src.size());
        int r = src.iterate<omt, deep_clone_iter>(this);
        lazy_assert_zero(r);
        this->d.a.num_values = src.size();
    }

    /**
     * 
     */
    void clear(void)
    {
        if (this->is_array) {
            this->d.a.start_idx = 0;
            this->d.a.num_values = 0;
        } else {
            this->d.t.root = NODE_NULL;
            this->d.t.free_idx = 0;
        }
    }

    /**
     * 
     */
    void destroy(void)
    {
        this->clear();
        this->capacity = 0;
        if (this->is_array) {
            if (this->d.a.values != nullptr) {
                toku_free(this->d.a.values);
            }
            this->d.a.values = nullptr;
        } else {
            if (this->d.t.nodes != nullptr) {
                toku_free(this->d.t.nodes);
            }
            this->d.t.nodes = nullptr;
        }
    }

    /**
     * 
     */
    inline uint32_t size(void) const
    {
        if (this->is_array) {
            return this->d.a.num_values;
        } else {
            return this->nweight(this->d.t.root);
        }
    }

    /**
     * 
     */
    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    int insert(const omtdata_t &value, const omtcmp_t &v, uint32_t *const idx)
    {
        int r;
        uint32_t insert_idx;

        r = this->find_zero<omtcmp_t, h>(v, nullptr, &insert_idx);
        if (r==0) {
            if (idx) *idx = insert_idx;
            return DB_KEYEXIST;
        }
        if (r != DB_NOTFOUND) return r;

        if ((r = this->insert_at(value, insert_idx))) return r;
        if (idx) *idx = insert_idx;

        return 0;
    }

    /**
     * 
     */
    int insert_at(const omtdata_t &value, const uint32_t idx)
    {
        if (idx > this->size()) { return EINVAL; }
        this->maybe_resize_or_convert(this->size() + 1);
        if (this->is_array && idx != this->d.a.num_values &&
            (idx != 0 || this->d.a.start_idx == 0)) {
            this->convert_to_tree();
        }
        if (this->is_array) {
            if (idx == this->d.a.num_values) {
                this->d.a.values[this->d.a.start_idx + this->d.a.num_values] = value;
            }
            else {
                this->d.a.values[--this->d.a.start_idx] = value;
            }
            this->d.a.num_values++;
        }
        else {
            node_idx *rebalance_idx = nullptr;
            this->insert_internal(&this->d.t.root, value, idx, &rebalance_idx);
            if (rebalance_idx != nullptr) {
                this->rebalance(rebalance_idx);
            }
        }
        return 0;
    }

    /**
     * 
     */
    int set_at(const omtdata_t &value, const uint32_t idx)
    {
        if (idx >= this->size()) { return EINVAL; }
        if (this->is_array) {
            this->set_at_internal_array(value, idx);
        } else {
            this->set_at_internal(this->d.t.root, value, idx);
        }
        return 0;
    }

    /**
     * 
     */
    int delete_at(const uint32_t idx)
    {
        if (idx >= this->size()) { return EINVAL; }
        this->maybe_resize_or_convert(this->size() - 1);
        if (this->is_array && idx != 0 && idx != this->d.a.num_values - 1) {
            this->convert_to_tree();
        }
        if (this->is_array) {
            //Testing for 0 does not rule out it being the last entry.
            //Test explicitly for num_values-1
            if (idx != this->d.a.num_values - 1) {
                this->d.a.start_idx++;
            }
            this->d.a.num_values--;
        } else {
            node_idx *rebalance_idx = nullptr;
            this->delete_internal(&this->d.t.root, idx, nullptr, &rebalance_idx);
            if (rebalance_idx != nullptr) {
                this->rebalance(rebalance_idx);
            }
        }
        return 0;
    }

    /**
     * 
     */
    template<typename iterate_extra_t,
             int (*f)(const omtdata_t &, const uint32_t, iterate_extra_t *const)>
    int iterate(iterate_extra_t *const iterate_extra) const {
        return this->iterate_on_range<iterate_extra_t, f>(0, this->size(), iterate_extra);
    }

    /**
     * 
     */
    template<typename iterate_extra_t,
             int (*f)(const omtdata_t &, const uint32_t, iterate_extra_t *const)>
    int iterate_on_range(const uint32_t left, const uint32_t right, iterate_extra_t *const iterate_extra) const {
        if (right > this->size()) { return EINVAL; }
        if (this->is_array) {
            return this->iterate_internal_array<iterate_extra_t, f>(left, right, iterate_extra);
        }
        return this->iterate_internal<iterate_extra_t, f>(left, right, this->d.t.root, 0, iterate_extra);
    }

    /**
     * 
     */
    template<typename iterate_extra_t,
             int (*f)(omtdata_t *, const uint32_t, iterate_extra_t *const)>
    void iterate_ptr(iterate_extra_t *const iterate_extra) {
        if (this->is_array) {
            this->iterate_ptr_internal_array<iterate_extra_t, f>(0, this->size(), iterate_extra);
        } else {
            this->iterate_ptr_internal<iterate_extra_t, f>(0, this->size(), this->d.t.root, 0, iterate_extra);
        }
    }

    void free_items(void) {
        this->iterate_ptr<void, free_items_iter>(nullptr);
    }

    /**
     * 
     */
    int fetch(const uint32_t idx, omtdataout_t *const value) const
    {
        if (idx >= this->size()) { return EINVAL; }
        if (this->is_array) {
            this->fetch_internal_array(idx, value);
        } else {
            this->fetch_internal(this->d.t.root, idx, value);
        }
        return 0;
    }

    /**
     * 
     */
    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    int find_zero(const omtcmp_t &extra, omtdataout_t *const value, uint32_t *const idxp) const
    {
        uint32_t tmp_index;
        uint32_t *const child_idxp = (idxp != nullptr) ? idxp : &tmp_index;
        int r;
        if (this->is_array) {
            r = this->find_internal_zero_array<omtcmp_t, h>(extra, value, child_idxp);
        }
        else {
            r = this->find_internal_zero<omtcmp_t, h>(this->d.t.root, extra, value, child_idxp);
        }
        return r;
    }

    /**
     * 
     */
    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    int find(const omtcmp_t &extra, int direction, omtdataout_t *const value, uint32_t *const idxp) const
    {
        uint32_t tmp_index;
        uint32_t *const child_idxp = (idxp != nullptr) ? idxp : &tmp_index;
        if (direction == 0) {
            abort();
        } else if (direction < 0) {
            if (this->is_array) {
                return this->find_internal_minus_array<omtcmp_t, h>(extra, value, child_idxp);
            } else {
                return this->find_internal_minus<omtcmp_t, h>(this->d.t.root, extra, value, child_idxp);
            }
        } else {
            if (this->is_array) {
                return this->find_internal_plus_array<omtcmp_t, h>(extra, value, child_idxp);
            } else {
                return this->find_internal_plus<omtcmp_t, h>(this->d.t.root, extra, value, child_idxp);
            }
        }
    }

    /**
     * 
     */
    size_t memory_size(void) {
        if (this->is_array) {
            return (sizeof *this) + this->capacity * (sizeof this->d.a.values[0]);
        }
        return (sizeof *this) + this->capacity * (sizeof this->d.t.nodes[0]);
    }

private:
    typedef uint32_t node_idx;
    enum {
        NODE_NULL = UINT32_MAX
    };

    struct omt_node {
        uint32_t weight;
        node_idx left;
        node_idx right;
        omtdata_t value;
    } __attribute__((__packed__));

    struct omt_array {
        uint32_t start_idx;
        uint32_t num_values;
        omtdata_t *values;
    };

    struct omt_tree {
        node_idx root;
        node_idx free_idx;
        struct omt_node *nodes;
    };

    bool is_array;
    uint32_t capacity;
    union {
        struct omt_array a;
        struct omt_tree t;
    } d;


    void create_internal_no_array(const uint32_t new_capacity) {
        this->is_array = true;
        this->capacity = new_capacity;
        this->d.a.start_idx = 0;
        this->d.a.num_values = 0;
        this->d.a.values = nullptr;
    }

    void create_internal(const uint32_t new_capacity) {
        this->create_internal_no_array(new_capacity);
        XMALLOC_N(this->capacity, this->d.a.values);
    }

    inline uint32_t nweight(const node_idx idx) const {
        if (idx == NODE_NULL) {
            return 0;
        } else {
            return this->d.t.nodes[idx].weight;
        }
    }

    inline node_idx node_malloc(void) {
        invariant(this->d.t.free_idx < this->capacity);
        return this->d.t.free_idx++;
    }

    inline void node_free(const node_idx idx) {
        invariant(idx < this->capacity);
    }

    inline void maybe_resize_array(const uint32_t n) {
        const uint32_t new_size = n<=2 ? 4 : 2*n;
        const uint32_t room = this->capacity - this->d.a.start_idx;

        if (room < n || this->capacity / 2 >= new_size) {
            omtdata_t *XMALLOC_N(new_size, tmp_values);
            memcpy(tmp_values, &this->d.a.values[this->d.a.start_idx],
                   this->d.a.num_values * (sizeof tmp_values[0]));
            this->d.a.start_idx = 0;
            this->capacity = new_size;
            toku_free(this->d.a.values);
            this->d.a.values = tmp_values;
        }
    }

    __attribute__((nonnull))
    inline void fill_array_with_subtree_values(omtdata_t *const array, const node_idx tree_idx) const {
        if (tree_idx==NODE_NULL) return;
        const omt_node &tree = this->d.t.nodes[tree_idx];
        this->fill_array_with_subtree_values(&array[0], tree.left);
        array[this->nweight(tree.left)] = tree.value;
        this->fill_array_with_subtree_values(&array[this->nweight(tree.left) + 1], tree.right);
    }

    inline void convert_to_array(void) {
        if (!this->is_array) {
            const uint32_t num_values = this->size();
            uint32_t new_size = 2*num_values;
            new_size = new_size < 4 ? 4 : new_size;

            omtdata_t *XMALLOC_N(new_size, tmp_values);
            this->fill_array_with_subtree_values(tmp_values, this->d.t.root);
            toku_free(this->d.t.nodes);
            this->is_array       = true;
            this->capacity       = new_size;
            this->d.a.num_values = num_values;
            this->d.a.values     = tmp_values;
            this->d.a.start_idx  = 0;
        }
    }

    __attribute__((nonnull))
    inline void rebuild_from_sorted_array(node_idx *const n_idxp, const omtdata_t *const values, const uint32_t numvalues) {
        if (numvalues==0) {
            *n_idxp = NODE_NULL;
        } else {
            const uint32_t halfway = numvalues/2;
            const node_idx newidx = this->node_malloc();
            omt_node *const newnode = &this->d.t.nodes[newidx];
            newnode->weight = numvalues;
            newnode->value = values[halfway];
            *n_idxp = newidx; // update everything before the recursive calls so the second call can be a tail call.
            this->rebuild_from_sorted_array(&newnode->left,  &values[0], halfway);
            this->rebuild_from_sorted_array(&newnode->right, &values[halfway+1], numvalues - (halfway+1));
        }
    }

    inline void convert_to_tree(void) {
        if (this->is_array) {
            const uint32_t num_nodes = this->size();
            uint32_t new_size  = num_nodes*2;
            new_size = new_size < 4 ? 4 : new_size;

            omt_node *XMALLOC_N(new_size, new_nodes);
            omtdata_t *const values = this->d.a.values;
            omtdata_t *const tmp_values = &values[this->d.a.start_idx];
            this->is_array = false;
            this->d.t.nodes = new_nodes;
            this->capacity = new_size;
            this->d.t.free_idx = 0;
            this->d.t.root = NODE_NULL;
            this->rebuild_from_sorted_array(&this->d.t.root, tmp_values, num_nodes);
            toku_free(values);
        }
    }

    inline void maybe_resize_or_convert(const uint32_t n) {
        if (this->is_array) {
            this->maybe_resize_array(n);
        } else {
            const uint32_t new_size = n<=2 ? 4 : 2*n;
            const uint32_t num_nodes = this->nweight(this->d.t.root);
            if ((this->capacity/2 >= new_size) ||
                (this->d.t.free_idx >= this->capacity && num_nodes < n) ||
                (this->capacity<n)) {
                this->convert_to_array();
            }
        }
    }

    inline bool will_need_rebalance(const node_idx n_idx, const int leftmod, const int rightmod) const {
        if (n_idx==NODE_NULL) { return false; }
        const omt_node &n = this->d.t.nodes[n_idx];
        // one of the 1's is for the root.
        // the other is to take ceil(n/2)
        const uint32_t weight_left  = this->nweight(n.left)  + leftmod;
        const uint32_t weight_right = this->nweight(n.right) + rightmod;
        return ((1+weight_left < (1+1+weight_right)/2)
                ||
                (1+weight_right < (1+1+weight_left)/2));
    }

    __attribute__((nonnull))
    inline void insert_internal(node_idx *const n_idxp, const omtdata_t &value, const uint32_t idx, node_idx **const rebalance_idx) {
        if (*n_idxp == NODE_NULL) {
            invariant_zero(idx);
            const node_idx newidx = this->node_malloc();
            omt_node *const newnode = &this->d.t.nodes[newidx];
            newnode->weight = 1;
            newnode->left = NODE_NULL;
            newnode->right = NODE_NULL;
            newnode->value = value;
            *n_idxp = newidx;
        } else {
            const node_idx thisidx = *n_idxp;
            omt_node *const n = &this->d.t.nodes[thisidx];
            n->weight++;
            if (idx <= this->nweight(n->left)) {
                if (*rebalance_idx == nullptr && this->will_need_rebalance(thisidx, 1, 0)) {
                    *rebalance_idx = n_idxp;
                }
                this->insert_internal(&n->left, value, idx, rebalance_idx);
            } else {
                if (*rebalance_idx == nullptr && this->will_need_rebalance(thisidx, 0, 1)) {
                    *rebalance_idx = n_idxp;
                }
                const uint32_t sub_index = idx - this->nweight(n->left) - 1;
                this->insert_internal(&n->right, value, sub_index, rebalance_idx);
            }
        }
    }

    inline void set_at_internal_array(const omtdata_t &value, const uint32_t idx) {
        this->d.a.values[this->d.a.start_idx + idx] = value;
    }

    inline void set_at_internal(const node_idx n_idx, const omtdata_t &value, const uint32_t idx) {
        invariant(n_idx != NODE_NULL);
        omt_node *const n = &this->d.t.nodes[n_idx];
        const uint32_t leftweight = this->nweight(n->left);
        if (idx < leftweight) {
            this->set_at_internal(n->left, value, idx);
        } else if (idx == leftweight) {
            n->value = value;
        } else {
            this->set_at_internal(n->right, value, idx - leftweight - 1);
        }
    }

    inline void delete_internal(node_idx *const n_idxp, const uint32_t idx, omt_node *const copyn, node_idx **const rebalance_idx) {
        invariant_notnull(n_idxp);
        invariant_notnull(rebalance_idx);
        invariant(*n_idxp != NODE_NULL);
        omt_node *const n = &this->d.t.nodes[*n_idxp];
        const uint32_t leftweight = this->nweight(n->left);
        if (idx < leftweight) {
            n->weight--;
            if (*rebalance_idx == nullptr && this->will_need_rebalance(*n_idxp, -1, 0)) {
                *rebalance_idx = n_idxp;
            }
            this->delete_internal(&n->left, idx, copyn, rebalance_idx);
        } else if (idx == leftweight) {
            if (n->left == NODE_NULL) {
                const uint32_t oldidx = *n_idxp;
                *n_idxp = n->right;
                if (copyn != nullptr) {
                    copyn->value = n->value;
                }
                this->node_free(oldidx);
            } else if (n->right == NODE_NULL) {
                const uint32_t oldidx = *n_idxp;
                *n_idxp = n->left;
                if (copyn != nullptr) {
                    copyn->value = n->value;
                }
                this->node_free(oldidx);
            } else {
                if (*rebalance_idx == nullptr && this->will_need_rebalance(*n_idxp, 0, -1)) {
                    *rebalance_idx = n_idxp;
                }
                // don't need to copy up value, it's only used by this
                // next call, and when that gets to the bottom there
                // won't be any more recursion
                n->weight--;
                this->delete_internal(&n->right, 0, n, rebalance_idx);
            }
        } else {
            n->weight--;
            if (*rebalance_idx == nullptr && this->will_need_rebalance(*n_idxp, 0, -1)) {
                *rebalance_idx = n_idxp;
            }
            this->delete_internal(&n->right, idx - leftweight - 1, copyn, rebalance_idx);
        }
    }

    template<typename iterate_extra_t,
             int (*f)(const omtdata_t &, const uint32_t, iterate_extra_t *const)>
    inline int iterate_internal_array(const uint32_t left, const uint32_t right,
                                      iterate_extra_t *const iterate_extra) const {
        int r;
        for (uint32_t i = left; i < right; ++i) {
            r = f(this->d.a.values[this->d.a.start_idx + i], i, iterate_extra);
            if (r != 0) {
                return r;
            }
        }
        return 0;
    }

    template<typename iterate_extra_t,
             int (*f)(omtdata_t *, const uint32_t, iterate_extra_t *const)>
    inline void iterate_ptr_internal(const uint32_t left, const uint32_t right,
                                     const node_idx n_idx, const uint32_t idx,
                                     iterate_extra_t *const iterate_extra) {
        if (n_idx != NODE_NULL) { 
            omt_node *const n = this->d.t.nodes[n_idx];
            const uint32_t idx_root = idx + this->nweight(n->left);
            if (left < idx_root) {
                this->iterate_ptr_internal<iterate_extra_t, f>(left, right, n->left, idx, iterate_extra);
            }
            if (left <= idx_root && idx_root < right) {
                int r = f(&n->value, idx_root, iterate_extra);
                lazy_assert_zero(r);
            }
            if (idx_root + 1 < right) {
                this->iterate_ptr_internal<iterate_extra_t, f>(left, right, n->right, idx_root + 1, iterate_extra);
            }
        }
    }

    template<typename iterate_extra_t,
             int (*f)(omtdata_t *, const uint32_t, iterate_extra_t *const)>
    inline void iterate_ptr_internal_array(const uint32_t left, const uint32_t right,
                                           iterate_extra_t *const iterate_extra) {
        for (uint32_t i = left; i < right; ++i) {
            int r = f(&this->d.a.values[this->d.a.start_idx + i], i, iterate_extra);
            lazy_assert_zero(r);
        }
    }

    template<typename iterate_extra_t,
             int (*f)(const omtdata_t &, const uint32_t, iterate_extra_t *const)>
    inline int iterate_internal(const uint32_t left, const uint32_t right,
                                const node_idx n_idx, const uint32_t idx,
                                iterate_extra_t *const iterate_extra) const {
        if (n_idx == NODE_NULL) { return 0; }
        int r;
        const omt_node &n = this->d.t.nodes[n_idx];
        const uint32_t idx_root = idx + this->nweight(n.left);
        if (left < idx_root) {
            r = this->iterate_internal<iterate_extra_t, f>(left, right, n.left, idx, iterate_extra);
            if (r != 0) { return r; }
        }
        if (left <= idx_root && idx_root < right) {
            r = f(n.value, idx_root, iterate_extra);
            if (r != 0) { return r; }
        }
        if (idx_root + 1 < right) {
            return this->iterate_internal<iterate_extra_t, f>(left, right, n.right, idx_root + 1, iterate_extra);
        }
        return 0;
    }

    inline void fetch_internal_array(const uint32_t i, omtdataout_t *value) const {
        if (value != nullptr) {
            copyout(value, &this->d.a.values[this->d.a.start_idx + i]);
        }
    }

    inline void fetch_internal(const node_idx idx, const uint32_t i, omtdataout_t *value) const {
        omt_node *const n = &this->d.t.nodes[idx];
        const uint32_t leftweight = this->nweight(n->left);
        if (i < leftweight) {
            this->fetch_internal(n->left, i, value);
        } else if (i == leftweight) {
            if (value != nullptr) {
                copyout(value, n);
            }
        } else {
            this->fetch_internal(n->right, i - leftweight - 1, value);
        }
    }

    __attribute__((nonnull))
    inline void fill_array_with_subtree_idxs(node_idx *const array, const node_idx tree_idx) const {
        if (tree_idx != NODE_NULL) {
            const omt_node &tree = this->d.t.nodes[tree_idx];
            this->fill_array_with_subtree_idxs(&array[0], tree.left);
            array[this->nweight(tree.left)] = tree_idx;
            this->fill_array_with_subtree_idxs(&array[this->nweight(tree.left) + 1], tree.right);
        }
    }

    __attribute__((nonnull))
    inline void rebuild_subtree_from_idxs(node_idx *const n_idxp, const node_idx *const idxs, const uint32_t numvalues) {
        if (numvalues==0) {
            *n_idxp = NODE_NULL;
        } else {
            uint32_t halfway = numvalues/2;
            *n_idxp = idxs[halfway];
            //node_idx newidx = idxs[halfway];
            omt_node *const newnode = &this->d.t.nodes[*n_idxp];
            newnode->weight = numvalues;
            // value is already in there.
            this->rebuild_subtree_from_idxs(&newnode->left,  &idxs[0], halfway);
            this->rebuild_subtree_from_idxs(&newnode->right, &idxs[halfway+1], numvalues-(halfway+1));
            //n_idx = newidx;
        }
    }

    __attribute__((nonnull))
    inline void rebalance(node_idx *const n_idxp) {
        node_idx idx = *n_idxp;
        if (idx==this->d.t.root) {
            //Try to convert to an array.
            //If this fails, (malloc) nothing will have changed.
            //In the failure case we continue on to the standard rebalance
            //algorithm.
            this->convert_to_array();
        } else {
            const omt_node &n = this->d.t.nodes[idx];
            node_idx *tmp_array;
            size_t mem_needed = n.weight * (sizeof tmp_array[0]);
            size_t mem_free = (this->capacity - this->d.t.free_idx) * (sizeof this->d.t.nodes[0]);
            bool malloced;
            if (mem_needed<=mem_free) {
                //There is sufficient free space at the end of the nodes array
                //to hold enough node indexes to rebalance.
                malloced = false;
                tmp_array = reinterpret_cast<node_idx *>(&this->d.t.nodes[this->d.t.free_idx]);
            }
            else {
                malloced = true;
                XMALLOC_N(n.weight, tmp_array);
            }
            this->fill_array_with_subtree_idxs(tmp_array, idx);
            this->rebuild_subtree_from_idxs(n_idxp, tmp_array, n.weight);
            if (malloced) toku_free(tmp_array);
        }
    }

    __attribute__((nonnull))
    static inline void copyout(omtdata_t *const out, const omt_node *const n) {
        *out = n->value;
    }

    __attribute__((nonnull))
    static inline void copyout(omtdata_t **const out, omt_node *const n) {
        *out = &n->value;
    }

    __attribute__((nonnull))
    static inline void copyout(omtdata_t *const out, const omtdata_t *const stored_value_ptr) {
        *out = *stored_value_ptr;
    }

    __attribute__((nonnull))
    static inline void copyout(omtdata_t **const out, omtdata_t *const stored_value_ptr) {
        *out = stored_value_ptr;
    }

    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    inline int find_internal_zero_array(const omtcmp_t &extra, omtdataout_t *value, uint32_t *const idxp) const {
        invariant_notnull(idxp);
        uint32_t min = this->d.a.start_idx;
        uint32_t limit = this->d.a.start_idx + this->d.a.num_values;
        uint32_t best_pos = NODE_NULL;
        uint32_t best_zero = NODE_NULL;

        while (min!=limit) {
            uint32_t mid = (min + limit) / 2;
            int hv = h(this->d.a.values[mid], extra);
            if (hv<0) {
                min = mid+1;
            }
            else if (hv>0) {
                best_pos  = mid;
                limit     = mid;
            }
            else {
                best_zero = mid;
                limit     = mid;
            }
        }
        if (best_zero!=NODE_NULL) {
            //Found a zero
            if (value != nullptr) {
                copyout(value, &this->d.a.values[best_zero]);
            }
            *idxp = best_zero - this->d.a.start_idx;
            return 0;
        }
        if (best_pos!=NODE_NULL) *idxp = best_pos - this->d.a.start_idx;
        else                     *idxp = this->d.a.num_values;
        return DB_NOTFOUND;
    }

    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    inline int find_internal_zero(const node_idx n_idx, const omtcmp_t &extra, omtdataout_t *value, uint32_t *const idxp) const {
        invariant_notnull(idxp);
        if (n_idx==NODE_NULL) {
            *idxp = 0;
            return DB_NOTFOUND;
        }
        omt_node *const n = &this->d.t.nodes[n_idx];
        int hv = h(n->value, extra);
        if (hv<0) {
            int r = this->find_internal_zero<omtcmp_t, h>(n->right, extra, value, idxp);
            *idxp += this->nweight(n->left)+1;
            return r;
        } else if (hv>0) {
            return this->find_internal_zero<omtcmp_t, h>(n->left, extra, value, idxp);
        } else {
            int r = this->find_internal_zero<omtcmp_t, h>(n->left, extra, value, idxp);
            if (r==DB_NOTFOUND) {
                *idxp = this->nweight(n->left);
                if (value != nullptr) {
                    copyout(value, n);
                }
                r = 0;
            }
            return r;
        }
    }

    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    inline int find_internal_plus_array(const omtcmp_t &extra, omtdataout_t *value, uint32_t *const idxp) const {
        invariant_notnull(idxp);
        uint32_t min = this->d.a.start_idx;
        uint32_t limit = this->d.a.start_idx + this->d.a.num_values;
        uint32_t best = NODE_NULL;

        while (min != limit) {
            const uint32_t mid = (min + limit) / 2;
            const int hv = h(this->d.a.values[mid], extra);
            if (hv > 0) {
                best = mid;
                limit = mid;
            } else {
                min = mid + 1;
            }
        }
        if (best == NODE_NULL) { return DB_NOTFOUND; }
        if (value != nullptr) {
            copyout(value, &this->d.a.values[best]);
        }
        *idxp = best - this->d.a.start_idx;
        return 0;
    }

    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    inline int find_internal_plus(const node_idx n_idx, const omtcmp_t &extra, omtdataout_t *value, uint32_t *const idxp) const {
        invariant_notnull(idxp);
        if (n_idx==NODE_NULL) {
            return DB_NOTFOUND;
        }
        omt_node *const n = &this->d.t.nodes[n_idx];
        int hv = h(n->value, extra);
        int r;
        if (hv > 0) {
            r = this->find_internal_plus<omtcmp_t, h>(n->left, extra, value, idxp);
            if (r == DB_NOTFOUND) {
                *idxp = this->nweight(n->left);
                if (value != nullptr) {
                    copyout(value, n);
                }
                r = 0;
            }
        } else {
            r = this->find_internal_plus<omtcmp_t, h>(n->right, extra, value, idxp);
            if (r == 0) {
                *idxp += this->nweight(n->left) + 1;
            }
        }
        return r;
    }

    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    inline int find_internal_minus_array(const omtcmp_t &extra, omtdataout_t *value, uint32_t *const idxp) const {
        invariant_notnull(idxp);
        uint32_t min = this->d.a.start_idx;
        uint32_t limit = this->d.a.start_idx + this->d.a.num_values;
        uint32_t best = NODE_NULL;

        while (min != limit) {
            const uint32_t mid = (min + limit) / 2;
            const int hv = h(this->d.a.values[mid], extra);
            if (hv < 0) {
                best = mid;
                min = mid + 1;
            } else {
                limit = mid;
            }
        }
        if (best == NODE_NULL) { return DB_NOTFOUND; }
        if (value != nullptr) {
            copyout(value, &this->d.a.values[best]);
        }
        *idxp = best - this->d.a.start_idx;
        return 0;
    }

    template<typename omtcmp_t,
             int (*h)(const omtdata_t &, const omtcmp_t &)>
    inline int find_internal_minus(const node_idx n_idx, const omtcmp_t &extra, omtdataout_t *value, uint32_t *const idxp) const {
        invariant_notnull(idxp);
        if (n_idx==NODE_NULL) {
            return DB_NOTFOUND;
        }
        omt_node *const n = &this->d.t.nodes[n_idx];
        int hv = h(n->value, extra);
        if (hv < 0) {
            int r = this->find_internal_minus<omtcmp_t, h>(n->right, extra, value, idxp);
            if (r == 0) {
                *idxp += this->nweight(n->left) + 1;
            } else if (r == DB_NOTFOUND) {
                *idxp = this->nweight(n->left);
                if (value != nullptr) {
                    copyout(value, n);
                }
                r = 0;
            }
            return r;
        } else {
            return this->find_internal_minus<omtcmp_t, h>(n->left, extra, value, idxp);
        }
    }

    __attribute__((nonnull))
    static inline int deep_clone_iter(const omtdata_t &value, const uint32_t idx, omt *const dest) {
        static_assert(std::is_pointer<omtdata_t>::value, "omtdata_t isn't a pointer, can't do deep clone");
        invariant_notnull(dest);
        invariant(idx == dest->d.a.num_values);
        invariant(idx < dest->capacity);
        XMEMDUP(dest->d.a.values[dest->d.a.num_values++], value);
        return 0;
    }

    static inline int free_items_iter(omtdata_t *value, const uint32_t UU(idx), void *const UU(unused)) {
        static_assert(std::is_pointer<omtdata_t>::value, "omtdata_t isn't a pointer, can't do free items");
        invariant_notnull(*value);
        toku_free(*value);
        return 0;
    }
};

};

#endif  /* #ifndef OMT_TMPL_H */