/* Produced by texiweb from libavl.w. */

/* libavl - library for manipulation of binary trees.
 Copyright (C) 1998-2002, 2004 Free Software Foundation, Inc.

 This program is free software; you can redistribute it and/or
 modify it under the terms of the GNU General Public License as
 published by the Free Software Foundation; either version 2 of the
 License, or (at your option) any later version.

 This program is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 See the GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program; if not, write to the Free Software
 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 02111-1307, USA.

 The author may be contacted at <blp@gnu.org> on the Internet, or
 write to Ben Pfaff, Stanford University, Computer Science Dept., 353
 Serra Mall, Stanford CA 94305, USA.
 */

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "avl.h"
#include "fastCMaths.h"
#include "sonLibGlobalsInternal.h"

/* Creates and returns a new table
 with comparison function |compare| using parameter |param|
 and memory allocator |allocator|.
 Returns |NULL| if memory allocation failed. */
struct avl_table *
avl_create(avl_comparison_func *compare, void *param,
        struct libavl_allocator *allocator) {
    struct avl_table *tree;

    assert (compare != NULL);

    if (allocator == NULL)
        allocator = &avl_allocator_default;

    tree = allocator->libavl_malloc(allocator, sizeof *tree);
    assert(tree != NULL);
    if (tree == NULL)
        return NULL;

    tree->avl_root = NULL;
    tree->avl_compare = compare;
    tree->avl_param = param;
    tree->avl_alloc = allocator;
    tree->avl_count = 0;
    tree->avl_generation = 0;

    return tree;
}

/* Search |tree| for an item matching |item|, and return it if found.
 Otherwise return |NULL|. */
void *
avl_find(const struct avl_table *tree, const void *item) {
    const struct avl_node *p;

    assert (tree != NULL && item != NULL);
    for (p = tree->avl_root; p != NULL;) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);

        if (cmp < 0)
            p = p->avl_link[0];
        else if (cmp > 0)
            p = p->avl_link[1];
        else
            /* |cmp == 0| */
            return p->avl_data;
    }

    return NULL;
}

/* Search in |tree| for the object minimally less than |item|, and return it if found.
 Otherwise return |NULL| if no object less than |item| */
void *
avl_find_lessThan(const struct avl_table *tree, const void *item) {
    const struct avl_node *p;

    assert (tree != NULL && item != NULL);
    void *lessThan = NULL;
    for (p = tree->avl_root; p != NULL;) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);

        if (cmp <= 0) {
            p = p->avl_link[0];
        } else { // cmp > 0
            lessThan = p->avl_data;
            p = p->avl_link[1];
        }
    }

    return lessThan;
}

/* Search in |tree| for the object minimally less than |item|, and return it if found.
 Otherwise return |NULL| if no object less than |item| */
void *
avl_find_lessThanOrEqual(const struct avl_table *tree, const void *item) {
    const struct avl_node *p;

    assert (tree != NULL && item != NULL);
    void *lessThan = NULL;
    for (p = tree->avl_root; p != NULL;) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);

        if (cmp < 0) {
            p = p->avl_link[0];
        } else if(cmp > 0) {
            lessThan = p->avl_data;
            p = p->avl_link[1];
        }
        else {
            return p->avl_data;
        }
    }

    return lessThan;
}

/* Search in |tree| for the object minimally greater than |item|, and return it if found.
 Otherwise return |NULL|. */
void *
avl_find_greaterThan(const struct avl_table *tree, const void *item) {
    const struct avl_node *p;

    assert (tree != NULL && item != NULL);
    void *greaterThan = NULL;
    for (p = tree->avl_root; p != NULL;) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);

        if (cmp >= 0) {
            p = p->avl_link[1];
        } else { // cmp < 0
            greaterThan = p->avl_data;
            p = p->avl_link[0];
        }
    }

    return greaterThan;
}

/* Search in |tree| for the object equal or minimally greater than |item|, and return it if found.
 Otherwise return |NULL|. */
void *
avl_find_greaterThanOrEqual(const struct avl_table *tree, const void *item) {
    const struct avl_node *p;

    assert (tree != NULL && item != NULL);
    void *greaterThan = NULL;
    for (p = tree->avl_root; p != NULL;) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);

        if (cmp > 0) {
            p = p->avl_link[1];
        } else if(cmp < 0) {
            greaterThan = p->avl_data;
            p = p->avl_link[0];
        }
        else {
            return p->avl_data;
        }
    }

    return greaterThan;
}

/* Inserts |item| INT_32o |tree| and returns a poINT_32er to |item|'s address.
 If a duplicate item is found in the tree,
 returns a poINT_32er to the duplicate without inserting |item|.
 Returns |NULL| in case of memory allocation failure. */
void **
avl_probe(struct avl_table *tree, void *item) {
    struct avl_node *y, *z; /* Top node to update balance factor, and parent. */
    struct avl_node *p, *q; /* Iterator, and parent. */
    struct avl_node *n; /* Newly inserted node. */
    struct avl_node *w; /* New root of rebalanced subtree. */
    int32_t dir; /* Direction to descend. */

    unsigned char da[AVL_MAX_HEIGHT]; /* Cached comparison results. */
    int32_t k = 0; /* Number of cached results. */

    assert (tree != NULL && item != NULL);

    z = (struct avl_node *) &tree->avl_root;
    y = tree->avl_root;
    dir = 0;
    for (q = z, p = y; p != NULL; q = p, p = p->avl_link[dir]) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);
        if (cmp == 0)
            return &p->avl_data;

        if (p->avl_balance != 0)
            z = q, y = p, k = 0;
        da[k++] = dir = cmp > 0;
    }

    n = q->avl_link[dir] = tree->avl_alloc->libavl_malloc(tree->avl_alloc,
            sizeof *n);
    if (n == NULL)
        return NULL;

    tree->avl_count++;
    n->avl_data = item;
    n->avl_link[0] = n->avl_link[1] = NULL;
    n->avl_balance = 0;
    if (y == NULL)
        return &n->avl_data;

    for (p = y, k = 0; p != n; p = p->avl_link[da[k]], k++)
        if (da[k] == 0)
            p->avl_balance--;
        else
            p->avl_balance++;

    if (y->avl_balance == -2) {
        struct avl_node *x = y->avl_link[0];
        if (x->avl_balance == -1) {
            w = x;
            y->avl_link[0] = x->avl_link[1];
            x->avl_link[1] = y;
            x->avl_balance = y->avl_balance = 0;
        } else {
            assert (x->avl_balance == +1);
            w = x->avl_link[1];
            x->avl_link[1] = w->avl_link[0];
            w->avl_link[0] = x;
            y->avl_link[0] = w->avl_link[1];
            w->avl_link[1] = y;
            if (w->avl_balance == -1)
                x->avl_balance = 0, y->avl_balance = +1;
            else if (w->avl_balance == 0)
                x->avl_balance = y->avl_balance = 0;
            else
                /* |w->avl_balance == +1| */
                x->avl_balance = -1, y->avl_balance = 0;
            w->avl_balance = 0;
        }
    } else if (y->avl_balance == +2) {
        struct avl_node *x = y->avl_link[1];
        if (x->avl_balance == +1) {
            w = x;
            y->avl_link[1] = x->avl_link[0];
            x->avl_link[0] = y;
            x->avl_balance = y->avl_balance = 0;
        } else {
            assert (x->avl_balance == -1);
            w = x->avl_link[0];
            x->avl_link[0] = w->avl_link[1];
            w->avl_link[1] = x;
            y->avl_link[1] = w->avl_link[0];
            w->avl_link[0] = y;
            if (w->avl_balance == +1)
                x->avl_balance = 0, y->avl_balance = -1;
            else if (w->avl_balance == 0)
                x->avl_balance = y->avl_balance = 0;
            else
                /* |w->avl_balance == -1| */
                x->avl_balance = +1, y->avl_balance = 0;
            w->avl_balance = 0;
        }
    } else
        return &n->avl_data;
    z->avl_link[y != z->avl_link[0]] = w;

    tree->avl_generation++;
    return &n->avl_data;
}

/* Inserts |item| INT_32o |table|.
 Returns |NULL| if |item| was successfully inserted
 or if a memory allocation error occurred.
 Otherwise, returns the duplicate item. */
void *
avl_insert(struct avl_table *table, void *item) {
    void **p = avl_probe(table, item);
    return p == NULL || *p == item ? NULL : *p;
}

/* Inserts |item| INT_32o |table|, replacing any duplicate item.
 Returns |NULL| if |item| was inserted without replacing a duplicate,
 or if a memory allocation error occurred.
 Otherwise, returns the item that was replaced. */
void *
avl_replace(struct avl_table *table, void *item) {
    void **p = avl_probe(table, item);
    if (p == NULL || *p == item)
        return NULL;
    else {
        void *r = *p;
        *p = item;
        return r;
    }
}

/* Deletes from |tree| and returns an item matching |item|.
 Returns a null poINT_32er if no matching item found. */
void *
avl_delete(struct avl_table *tree, const void *item) {
    /* Stack of nodes. */
    struct avl_node *pa[AVL_MAX_HEIGHT]; /* Nodes. */
    unsigned char da[AVL_MAX_HEIGHT]; /* |avl_link[]| indexes. */
    int32_t k; /* Stack poINT_32er. */

    struct avl_node *p; /* Traverses tree to find node to delete. */
    int32_t cmp; /* Result of comparison between |item| and |p|. */

    assert (tree != NULL && item != NULL);

    k = 0;
    p = (struct avl_node *) &tree->avl_root;
    for (cmp = -1; cmp != 0; cmp = tree->avl_compare(item, p->avl_data,
            tree->avl_param)) {
        int32_t dir = cmp > 0;

        pa[k] = p;
        da[k++] = dir;

        p = p->avl_link[dir];
        if (p == NULL)
            return NULL;
    }
    item = p->avl_data;

    if (p->avl_link[1] == NULL)
        pa[k - 1]->avl_link[da[k - 1]] = p->avl_link[0];
    else {
        struct avl_node *r = p->avl_link[1];
        if (r->avl_link[0] == NULL) {
            r->avl_link[0] = p->avl_link[0];
            r->avl_balance = p->avl_balance;
            pa[k - 1]->avl_link[da[k - 1]] = r;
            da[k] = 1;
            pa[k++] = r;
        } else {
            struct avl_node *s;
            int32_t j = k++;

            for (;;) {
                da[k] = 0;
                pa[k++] = r;
                s = r->avl_link[0];
                if (s->avl_link[0] == NULL)
                    break;

                r = s;
            }

            s->avl_link[0] = p->avl_link[0];
            r->avl_link[0] = s->avl_link[1];
            s->avl_link[1] = p->avl_link[1];
            s->avl_balance = p->avl_balance;

            pa[j - 1]->avl_link[da[j - 1]] = s;
            da[j] = 1;
            pa[j] = s;
        }
    }

    tree->avl_alloc->libavl_free(tree->avl_alloc, p);

    assert (k> 0);
    while (--k > 0) {
        struct avl_node *y = pa[k];

        if (da[k] == 0) {
            y->avl_balance++;
            if (y->avl_balance == +1)
                break;
            else if (y->avl_balance == +2) {
                struct avl_node *x = y->avl_link[1];
                if (x->avl_balance == -1) {
                    struct avl_node *w;
                    assert (x->avl_balance == -1);
                    w = x->avl_link[0];
                    x->avl_link[0] = w->avl_link[1];
                    w->avl_link[1] = x;
                    y->avl_link[1] = w->avl_link[0];
                    w->avl_link[0] = y;
                    if (w->avl_balance == +1)
                        x->avl_balance = 0, y->avl_balance = -1;
                    else if (w->avl_balance == 0)
                        x->avl_balance = y->avl_balance = 0;
                    else
                        /* |w->avl_balance == -1| */
                        x->avl_balance = +1, y->avl_balance = 0;
                    w->avl_balance = 0;
                    pa[k - 1]->avl_link[da[k - 1]] = w;
                } else {
                    y->avl_link[1] = x->avl_link[0];
                    x->avl_link[0] = y;
                    pa[k - 1]->avl_link[da[k - 1]] = x;
                    if (x->avl_balance == 0) {
                        x->avl_balance = -1;
                        y->avl_balance = +1;
                        break;
                    } else
                        x->avl_balance = y->avl_balance = 0;
                }
            }
        } else {
            y->avl_balance--;
            if (y->avl_balance == -1)
                break;
            else if (y->avl_balance == -2) {
                struct avl_node *x = y->avl_link[0];
                if (x->avl_balance == +1) {
                    struct avl_node *w;
                    assert (x->avl_balance == +1);
                    w = x->avl_link[1];
                    x->avl_link[1] = w->avl_link[0];
                    w->avl_link[0] = x;
                    y->avl_link[0] = w->avl_link[1];
                    w->avl_link[1] = y;
                    if (w->avl_balance == -1)
                        x->avl_balance = 0, y->avl_balance = +1;
                    else if (w->avl_balance == 0)
                        x->avl_balance = y->avl_balance = 0;
                    else
                        /* |w->avl_balance == +1| */
                        x->avl_balance = -1, y->avl_balance = 0;
                    w->avl_balance = 0;
                    pa[k - 1]->avl_link[da[k - 1]] = w;
                } else {
                    y->avl_link[0] = x->avl_link[1];
                    x->avl_link[1] = y;
                    pa[k - 1]->avl_link[da[k - 1]] = x;
                    if (x->avl_balance == 0) {
                        x->avl_balance = +1;
                        y->avl_balance = -1;
                        break;
                    } else
                        x->avl_balance = y->avl_balance = 0;
                }
            }
        }
    }

    tree->avl_count--;
    tree->avl_generation++;
    return (void *) item;
}

/* Refreshes the stack of parent poINT_32ers in |trav|
 and updates its generation number. */
static void trav_refresh(struct avl_traverser *trav) {
    assert (trav != NULL);

    trav->avl_generation = trav->avl_table->avl_generation;

    if (trav->avl_node != NULL) {
        avl_comparison_func *cmp = trav->avl_table->avl_compare;
        void *param = trav->avl_table->avl_param;
        struct avl_node *node = trav->avl_node;
        struct avl_node *i;

        trav->avl_height = 0;
        for (i = trav->avl_table->avl_root; i != node;) {
            assert (trav->avl_height < AVL_MAX_HEIGHT);
            assert (i != NULL);

            trav->avl_stack[trav->avl_height++] = i;
            i = i->avl_link[cmp(node->avl_data, i->avl_data, param) > 0];
        }
    }
}

/* Initializes |trav| for use with |tree|
 and selects the null node. */
void avl_t_init(struct avl_traverser *trav, struct avl_table *tree) {
    trav->avl_table = tree;
    trav->avl_node = NULL;
    trav->avl_height = 0;
    trav->avl_generation = tree->avl_generation;
}

/* Initializes |trav| for |tree|
 and selects and returns a poINT_32er to its least-valued item.
 Returns |NULL| if |tree| contains no nodes. */
void *
avl_t_first(struct avl_traverser *trav, struct avl_table *tree) {
    struct avl_node *x;

    assert (tree != NULL && trav != NULL);

    trav->avl_table = tree;
    trav->avl_height = 0;
    trav->avl_generation = tree->avl_generation;

    x = tree->avl_root;
    if (x != NULL)
        while (x->avl_link[0] != NULL) {
            assert (trav->avl_height < AVL_MAX_HEIGHT);
            trav->avl_stack[trav->avl_height++] = x;
            x = x->avl_link[0];
        }
    trav->avl_node = x;

    return x != NULL ? x->avl_data : NULL;
}

/* Initializes |trav| for |tree|
 and selects and returns a poINT_32er to its greatest-valued item.
 Returns |NULL| if |tree| contains no nodes. */
void *
avl_t_last(struct avl_traverser *trav, struct avl_table *tree) {
    struct avl_node *x;

    assert (tree != NULL && trav != NULL);

    trav->avl_table = tree;
    trav->avl_height = 0;
    trav->avl_generation = tree->avl_generation;

    x = tree->avl_root;
    if (x != NULL)
        while (x->avl_link[1] != NULL) {
            assert (trav->avl_height < AVL_MAX_HEIGHT);
            trav->avl_stack[trav->avl_height++] = x;
            x = x->avl_link[1];
        }
    trav->avl_node = x;

    return x != NULL ? x->avl_data : NULL;
}

/* Searches for |item| in |tree|.
 If found, initializes |trav| to the item found and returns the item
 as well.
 If there is no matching item, initializes |trav| to the null item
 and returns |NULL|. */
void *
avl_t_find(struct avl_traverser *trav, struct avl_table *tree, void *item) {
    struct avl_node *p, *q;

    assert (trav != NULL && tree != NULL && item != NULL);
    trav->avl_table = tree;
    trav->avl_height = 0;
    trav->avl_generation = tree->avl_generation;
    for (p = tree->avl_root; p != NULL; p = q) {
        int32_t cmp = tree->avl_compare(item, p->avl_data, tree->avl_param);

        if (cmp < 0)
            q = p->avl_link[0];
        else if (cmp > 0)
            q = p->avl_link[1];
        else /* |cmp == 0| */
        {
            trav->avl_node = p;
            return p->avl_data;
        }

        assert (trav->avl_height < AVL_MAX_HEIGHT);
        trav->avl_stack[trav->avl_height++] = p;
    }

    trav->avl_height = 0;
    trav->avl_node = NULL;
    return NULL;
}

/* Attempts to insert |item| INT_32o |tree|.
 If |item| is inserted successfully, it is returned and |trav| is
 initialized to its location.
 If a duplicate is found, it is returned and |trav| is initialized to
 its location.  No replacement of the item occurs.
 If a memory allocation failure occurs, |NULL| is returned and |trav|
 is initialized to the null item. */
void *
avl_t_insert(struct avl_traverser *trav, struct avl_table *tree, void *item) {
    void **p;

    assert (trav != NULL && tree != NULL && item != NULL);

    p = avl_probe(tree, item);
    if (p != NULL) {
        trav->avl_table = tree;trav->avl_node =
        ((struct avl_node *)
                ((char *) p - offsetof (struct avl_node, avl_data)));
        trav->avl_generation = tree->avl_generation - 1;
        return *p;
    } else {
        avl_t_init(trav, tree);
        return NULL;
    }
}

/* Initializes |trav| to have the same current node as |src|. */
void *
avl_t_copy(struct avl_traverser *trav, const struct avl_traverser *src) {
    assert (trav != NULL && src != NULL);

    if (trav != src) {
        trav->avl_table = src->avl_table;
        trav->avl_node = src->avl_node;
        trav->avl_generation = src->avl_generation;
        if (trav->avl_generation == trav->avl_table->avl_generation) {
            trav->avl_height = src->avl_height;
            memcpy(trav->avl_stack, (const void *) src->avl_stack,
                    sizeof *trav->avl_stack * trav->avl_height);
        }
    }

    return trav->avl_node != NULL ? trav->avl_node->avl_data : NULL;
}

/* Returns the next data item in inorder
 within the tree being traversed with |trav|,
 or if there are no more data items returns |NULL|. */
void *
avl_t_next(struct avl_traverser *trav) {
    struct avl_node *x;

    assert (trav != NULL);

    if (trav->avl_generation != trav->avl_table->avl_generation)
        trav_refresh(trav);

    x = trav->avl_node;
    if (x == NULL) {
        return avl_t_first(trav, trav->avl_table);
    } else if (x->avl_link[1] != NULL) {
        assert (trav->avl_height < AVL_MAX_HEIGHT);
        trav->avl_stack[trav->avl_height++] = x;
        x = x->avl_link[1];

        while (x->avl_link[0] != NULL) {
            assert (trav->avl_height < AVL_MAX_HEIGHT);
            trav->avl_stack[trav->avl_height++] = x;
            x = x->avl_link[0];
        }
    } else {
        struct avl_node *y;

        do {
            if (trav->avl_height == 0) {
                trav->avl_node = NULL;
                return NULL;
            }

            y = x;
            x = trav->avl_stack[--trav->avl_height];
        } while (y == x->avl_link[1]);
    }
    trav->avl_node = x;

    return x->avl_data;
}

/* Returns the previous data item in inorder
 within the tree being traversed with |trav|,
 or if there are no more data items returns |NULL|. */
void *
avl_t_prev(struct avl_traverser *trav) {
    struct avl_node *x;

    assert (trav != NULL);

    if (trav->avl_generation != trav->avl_table->avl_generation)
        trav_refresh(trav);

    x = trav->avl_node;
    if (x == NULL) {
        return avl_t_last(trav, trav->avl_table);
    } else if (x->avl_link[0] != NULL) {
        assert (trav->avl_height < AVL_MAX_HEIGHT);
        trav->avl_stack[trav->avl_height++] = x;
        x = x->avl_link[0];

        while (x->avl_link[1] != NULL) {
            assert (trav->avl_height < AVL_MAX_HEIGHT);
            trav->avl_stack[trav->avl_height++] = x;
            x = x->avl_link[1];
        }
    } else {
        struct avl_node *y;

        do {
            if (trav->avl_height == 0) {
                trav->avl_node = NULL;
                return NULL;
            }

            y = x;
            x = trav->avl_stack[--trav->avl_height];
        } while (y == x->avl_link[0]);
    }
    trav->avl_node = x;

    return x->avl_data;
}

/* Returns |trav|'s current item. */
void *
avl_t_cur(struct avl_traverser *trav) {
    assert (trav != NULL);

    return trav->avl_node != NULL ? trav->avl_node->avl_data : NULL;
}

/* Replaces the current item in |trav| by |new| and returns the item replaced.
 |trav| must not have the null item selected.
 The new item must not upset the ordering of the tree. */
void *
avl_t_replace(struct avl_traverser *trav, void *new) {
    void *old;

    assert (trav != NULL && trav->avl_node != NULL && new != NULL);
    old = trav->avl_node->avl_data;
    trav->avl_node->avl_data = new;
    return old;
}

/* Destroys |new| with |avl_destroy (new, destroy)|,
 first setting right links of nodes in |stack| within |new|
 to null poINT_32ers to avoid touching uninitialized data. */
static void copy_error_recovery(struct avl_node **stack, int32_t height,
        struct avl_table *new, avl_item_func *destroy) {
    assert (stack != NULL && height >= 0 && new != NULL);

    for (; height > 2; height -= 2)
        stack[height - 1]->avl_link[1] = NULL;
    avl_destroy(new, destroy);
}

/* Copies |org| to a newly created tree, which is returned.
 If |copy != NULL|, each data item in |org| is first passed to |copy|,
 and the return values are inserted INT_32o the tree,
 with |NULL| return values taken as indications of failure.
 On failure, destroys the partially created new tree,
 applying |destroy|, if non-null, to each item in the new tree so far,
 and returns |NULL|.
 If |allocator != NULL|, it is used for allocation in the new tree.
 Otherwise, the same allocator used for |org| is used. */
struct avl_table *
avl_copy(const struct avl_table *org, avl_copy_func *copy,
        avl_item_func *destroy, struct libavl_allocator *allocator) {
    struct avl_node *stack[2 * (AVL_MAX_HEIGHT + 1)];
    int32_t height = 0;

    struct avl_table *new;
    const struct avl_node *x;
    struct avl_node *y;

    assert (org != NULL);
    new = avl_create(org->avl_compare, org->avl_param,
            allocator != NULL ? allocator : org->avl_alloc);
    if (new == NULL)
        return NULL;
    new->avl_count = org->avl_count;
    if (new->avl_count == 0)
        return new;

    x = (const struct avl_node *) &org->avl_root;
    y = (struct avl_node *) &new->avl_root;
    for (;;) {
        while (x->avl_link[0] != NULL) {
            assert (height < 2 * (AVL_MAX_HEIGHT + 1));

            y->avl_link[0] = new->avl_alloc->libavl_malloc(new->avl_alloc,
                    sizeof *y->avl_link[0]);
            if (y->avl_link[0] == NULL) {
                if (y != (struct avl_node *) &new->avl_root) {
                    y->avl_data = NULL;
                    y->avl_link[1] = NULL;
                }

                copy_error_recovery(stack, height, new, destroy);
                return NULL;
            }

            stack[height++] = (struct avl_node *) x;
            stack[height++] = y;
            x = x->avl_link[0];
            y = y->avl_link[0];
        }
        y->avl_link[0] = NULL;

        for (;;) {
            y->avl_balance = x->avl_balance;
            if (copy == NULL)
                y->avl_data = x->avl_data;
            else {
                y->avl_data = copy(x->avl_data, org->avl_param);
                if (y->avl_data == NULL) {
                    y->avl_link[1] = NULL;
                    copy_error_recovery(stack, height, new, destroy);
                    return NULL;
                }
            }

            if (x->avl_link[1] != NULL) {
                y->avl_link[1] = new->avl_alloc->libavl_malloc(new->avl_alloc,
                        sizeof *y->avl_link[1]);
                if (y->avl_link[1] == NULL) {
                    copy_error_recovery(stack, height, new, destroy);
                    return NULL;
                }

                x = x->avl_link[1];
                y = y->avl_link[1];
                break;
            } else
                y->avl_link[1] = NULL;

            if (height <= 2)
                return new;

            y = stack[--height];
            x = stack[--height];
        }
    }
    return 0;
}

/* Frees storage allocated for |tree|.
 If |destroy != NULL|, applies it to each data item in inorder. */
void avl_destroy(struct avl_table *tree, avl_item_func *destroy) {
    struct avl_node *p, *q;

    assert (tree != NULL);

    for (p = tree->avl_root; p != NULL; p = q)
        if (p->avl_link[0] == NULL) {
            q = p->avl_link[1];
            if (destroy != NULL && p->avl_data != NULL)
                destroy(p->avl_data, tree->avl_param);
            tree->avl_alloc->libavl_free(tree->avl_alloc, p);
        } else {
            q = p->avl_link[0];
            p->avl_link[0] = q->avl_link[1];
            q->avl_link[1] = p;
        }

    tree->avl_alloc->libavl_free(tree->avl_alloc, tree);
}

/* Allocates |size| bytes of space using |malloc()|.
 Returns a null poINT_32er if allocation fails. */
void *
avl_malloc(struct libavl_allocator *allocator, size_t size) {
    assert (allocator != NULL && size> 0);
    return st_malloc(size);
}

/* Frees |block|. */
void avl_free(struct libavl_allocator *allocator, void *block) {
    assert (allocator != NULL && block != NULL);
    free(block);
}

/* Default memory allocator that uses |malloc()| and |free()|. */
struct libavl_allocator avl_allocator_default = { avl_malloc, avl_free };

#undef NDEBUG
#include <assert.h>

/* Asserts that |avl_insert()| succeeds at inserting |item| INT_32o |table|. */
void( avl_assert_insert)(struct avl_table *table, void *item) {
    void **p = avl_probe(table, item);
    assert (p != NULL && *p == item);
}

/* Asserts that |avl_delete()| really removes |item| from |table|,
 and returns the removed item. */
void *
( avl_assert_delete)(struct avl_table *table, void *item) {
    void *p = avl_delete(table, item);
    assert (p != NULL);
    return p;
}

