src/avl/avl.c

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/*
 * $Id: avl.c,v 1.11 2005/04/30 03:03:05 fabio Exp $
 *
 */
/* LINTLIBRARY */


#include <stdio.h>

#ifndef PACKAGE
#include "util.h"
#endif

#include "avl.h"

#ifdef PACKAGE
extern char *malloc();
#ifdef ultrix
extern void free();
#endif

#define MAX(a,b)        ((a) > (b) ? (a) : (b))

#define NIL(type)               \
    ((type *) 0)
#define ALLOC(type, num)        \
    ((type *) malloc(sizeof(type) * (num)))
#define REALLOC(type, obj, num) \
    ((type *) realloc((char *) obj, sizeof(type) * (num)))
#define FREE(obj)               \
    free((char *) (obj))
#endif


#define HEIGHT(node) (node == NIL(avl_node) ? -1 : (node)->height)
#define BALANCE(node) (HEIGHT((node)->right) - HEIGHT((node)->left))

#define compute_height(node) {                          \
    int x=HEIGHT(node->left), y=HEIGHT(node->right);    \
    (node)->height = MAX(x,y) + 1;                      \
}

#define COMPARE(key, nodekey, compare)                  \
    ((compare == avl_numcmp) ?                          \
        (long) key - (long) nodekey :                   \
        (*compare)(key, nodekey))


#define STACK_SIZE      50

static avl_node *new_node(char *key, char *value);
static avl_node *find_rightmost(avl_node **node_p);
static void do_rebalance(avl_node ***stack_nodep, int stack_n); 
static int rotate_left(avl_node **node_p);
static int rotate_right(avl_node **node_p);
static int do_check_tree(avl_node *node, int (*compar)(const void *, const void *), int *error);

avl_tree *
avl_init_table(int (*compar)(const void *, const void *))
{
    avl_tree *tree;

    tree = ALLOC(avl_tree, 1);
    tree->root = NIL(avl_node);
    tree->compar = compar;
    tree->num_entries = 0;
    return tree;
}


int
avl_lookup(avl_tree *tree, const void *key, void *value_p)
{
    avl_node *node;
    int (*compare)(const void *, const void *) = tree->compar, diff;

    node = tree->root;
    while (node != NIL(avl_node)) {
        diff = COMPARE(key, node->key, compare);
        if (diff == 0) {
            /* got a match */
            if (value_p != NULL) *(char **)value_p = node->value;
            return 1;
        }
        node = (diff < 0) ? node->left : node->right;
    }
    return 0;
}

int
avl_first(avl_tree *tree, char **key_p, char **value_p)
{
    register avl_node *node;

    if (tree->root == 0) {
        return 0;               /* no entries */
    } else {
        /* walk down the tree; stop at leftmost leaf */
        for(node = tree->root; node->left != 0; node = node->left) {
        }
        if (key_p != NIL(char *)) *key_p = node->key;
        if (value_p != NIL(char *)) *value_p = node->value;
        return 1;
    }
}

int
avl_last(avl_tree *tree, char **key_p, char **value_p)
{
    register avl_node *node;

    if (tree->root == 0) {
        return 0;               /* no entries */
    } else {
        /* walk down the tree; stop at rightmost leaf */
        for(node = tree->root; node->right != 0; node = node->right) {
        }
        if (key_p != NIL(char *)) *key_p = node->key;
        if (value_p != NIL(char *)) *value_p = node->value;
        return 1;
    }
}

int
avl_insert(avl_tree *tree, void *key, void *value)
{
    avl_node **node_p, *node;
    int stack_n = 0;
    int (*compare)(const void *, const void *) = tree->compar;
    avl_node **stack_nodep[STACK_SIZE];
    int diff, status;

    node_p = &tree->root;

    /* walk down the tree (saving the path); stop at insertion point */
    status = 0;
    while ((node = *node_p) != NIL(avl_node)) {
        stack_nodep[stack_n++] = node_p;
        diff = COMPARE(key, node->key, compare);
        if (diff == 0) status = 1;
        node_p = (diff < 0) ? &node->left : &node->right;
    }

    /* insert the item and re-balance the tree */
    *node_p = new_node((char *)key, (char *)value);
    do_rebalance(stack_nodep, stack_n);
    tree->num_entries++;
    tree->modified = 1;
    return status;
}


int
avl_find_or_add(avl_tree *tree, char *key, char ***slot_p)
{
    register avl_node **node_p, *node;
    register int stack_n = 0;
    register int (*compare)(const void *, const void *) = tree->compar;
    avl_node **stack_nodep[STACK_SIZE];
    int diff;

    node_p = &tree->root;

    /* walk down the tree (saving the path); stop at insertion point */
    while ((node = *node_p) != NIL(avl_node)) {
        stack_nodep[stack_n++] = node_p;
        diff = COMPARE(key, node->key, compare);
        if (diff == 0) {
            if (slot_p != 0) *slot_p = &node->value;
            return 1;           /* found */
        }
        node_p = (diff < 0) ? &node->left : &node->right;
    }

    /* insert the item and re-balance the tree */
    *node_p = new_node(key, NIL(char));
    if (slot_p != 0) *slot_p = &(*node_p)->value;
    do_rebalance(stack_nodep, stack_n);
    tree->num_entries++;
    tree->modified = 1;
    return 0;                   /* not already in tree */
}

int
avl_delete(avl_tree *tree, void *key_p, void *value_p)
{
    avl_node **node_p, *node, *rightmost;
    int stack_n = 0;
    char *key = *(char **) key_p;
    int (*compare)(const void *, const void *) = tree->compar, diff;
    avl_node **stack_nodep[STACK_SIZE];

    node_p = &tree->root;

    /* Walk down the tree saving the path; return if not found */
    while ((node = *node_p) != NIL(avl_node)) {
        diff = COMPARE(key, node->key, compare);
        if (diff == 0) goto delete_item;
        stack_nodep[stack_n++] = node_p;
        node_p = (diff < 0) ? &node->left : &node->right;
    }
    return 0;           /* not found */

    /* prepare to delete node and replace it with rightmost of left tree */
delete_item:
    *(char **) key_p = node->key;
    if (value_p != NULL) *(char **)value_p = node->value;
    if (node->left == NIL(avl_node)) {
        *node_p = node->right;
    } else {
        rightmost = find_rightmost(&node->left);
        rightmost->left = node->left;
        rightmost->right = node->right;
        rightmost->height = -2;         /* mark bogus height for do_rebal */
        *node_p = rightmost;
        stack_nodep[stack_n++] = node_p;
    }
    FREE(node);

    /* work our way back up, re-balancing the tree */
    do_rebalance(stack_nodep, stack_n);
    tree->num_entries--;
    tree->modified = 1;
    return 1;
}

static void 
avl_record_gen_forward(avl_node *node, avl_generator *gen)
{
    if (node != NIL(avl_node)) {
        avl_record_gen_forward(node->left, gen);
        gen->nodelist[gen->count++] = node;
        avl_record_gen_forward(node->right, gen);
    }
}


static void 
avl_record_gen_backward(avl_node *node, avl_generator *gen)
{
    if (node != NIL(avl_node)) {
        avl_record_gen_backward(node->right, gen);
        gen->nodelist[gen->count++] = node;
        avl_record_gen_backward(node->left, gen);
    }
}


avl_generator *
avl_init_gen(avl_tree *tree, int dir)
{
    avl_generator *gen;

    /* what a hack */
    gen = ALLOC(avl_generator, 1);
    gen->tree = tree;
    gen->nodelist = ALLOC(avl_node *, avl_count(tree));
    gen->count = 0;
    if (dir == AVL_FORWARD) {
        avl_record_gen_forward(tree->root, gen);
    } else {
        avl_record_gen_backward(tree->root, gen);
    }
    gen->count = 0;

    /* catch any attempt to modify the tree while we generate */
    tree->modified = 0;
    return gen;
}


int
avl_gen(avl_generator *gen, char **key_p, char **value_p)
{
    avl_node *node;

    if (gen->count == gen->tree->num_entries) {
        return 0;
    } else {
        node = gen->nodelist[gen->count++];
        if (key_p != NIL(char *)) *key_p = node->key;
        if (value_p != NIL(char *)) *value_p = node->value;
        return 1;
    }
}


void
avl_free_gen(avl_generator *gen)
{
    FREE(gen->nodelist);
    FREE(gen);
}


static avl_node *
find_rightmost(avl_node **node_p)
{
    register avl_node *node;
    register int stack_n = 0;
    avl_node **stack_nodep[STACK_SIZE];

    node = *node_p;
    while (node->right != NIL(avl_node)) {
        stack_nodep[stack_n++] = node_p;
        node_p = &node->right;
        node = *node_p;
    }
    *node_p = node->left;

    do_rebalance(stack_nodep, stack_n);
    return node;
}


static void
do_rebalance(avl_node ***stack_nodep, int stack_n)
{
    register avl_node **node_p, *node;
    register int hl, hr;
    int height;

    /* work our way back up, re-balancing the tree */
    while (--stack_n >= 0) {
        node_p = stack_nodep[stack_n];
        node = *node_p;
        hl = HEIGHT(node->left);                /* watch for NIL */
        hr = HEIGHT(node->right);               /* watch for NIL */
        if ((hr - hl) < -1) {
            rotate_right(node_p);
        } else if ((hr - hl) > 1) {
            rotate_left(node_p);
        } else {
            height = MAX(hl, hr) + 1;
            if (height == node->height) break;
            node->height = height;
        }
    }
}

static int
rotate_left(avl_node **node_p)
{
    register avl_node *old_root = *node_p, *new_root, *new_right;

    if (BALANCE(old_root->right) >= 0) {
        *node_p = new_root = old_root->right;
        old_root->right = new_root->left;
        new_root->left = old_root;
    } else {
        new_right = old_root->right;
        *node_p = new_root = new_right->left;
        old_root->right = new_root->left;
        new_right->left = new_root->right;
        new_root->right = new_right;
        new_root->left = old_root;
        compute_height(new_right);
    }
    compute_height(old_root);
    compute_height(new_root);

    return 0;
}


static int
rotate_right(avl_node **node_p)
{
    register avl_node *old_root = *node_p, *new_root, *new_left;

    if (BALANCE(old_root->left) <= 0) {
        *node_p = new_root = old_root->left;
        old_root->left = new_root->right;
        new_root->right = old_root;
    } else {
        new_left = old_root->left;
        *node_p = new_root = new_left->right;
        old_root->left = new_root->right;
        new_left->right = new_root->left;
        new_root->left = new_left;
        new_root->right = old_root;
        compute_height(new_left);
    }
    compute_height(old_root);
    compute_height(new_root);

    return 0;
}

static void 
avl_walk_forward(avl_node *node, void (*func)(const void *, const void *))
{
    if (node != NIL(avl_node)) {
        avl_walk_forward(node->left, func);
        (*func)(node->key, node->value);
        avl_walk_forward(node->right, func);
    }
}


static void 
avl_walk_backward(avl_node *node, void (*func)(const void *, const void *))
{
    if (node != NIL(avl_node)) {
        avl_walk_backward(node->right, func);
        (*func)(node->key, node->value);
        avl_walk_backward(node->left, func);
    }
}


void
avl_foreach(
  avl_tree *tree,
  void (*func)(const void *, const void *),
  int direction)
{
    if (direction == AVL_FORWARD) {
        avl_walk_forward(tree->root, func);
    } else {
        avl_walk_backward(tree->root, func);
    }
}


static void
free_entry(
  avl_node *node,
  void (*key_free)(char *),
  void (*value_free)(char *))
{
    if (node != NIL(avl_node)) {
        free_entry(node->left, key_free, value_free);
        free_entry(node->right, key_free, value_free);
        if (key_free != 0) (*key_free)(node->key);
        if (value_free != 0) (*value_free)(node->value);
        FREE(node);
    }
}
   

void 
avl_free_table(
  avl_tree *tree,
  void (*key_free)(char *),
  void (*value_free)(char *))
{
    free_entry(tree->root, key_free, value_free);
    FREE(tree);
}


int 
avl_count(avl_tree *tree)
{
    return tree->num_entries;
}


static avl_node *
new_node(char *key, char *value)
{
    register avl_node *newn;

    newn = ALLOC(avl_node, 1);
    newn->key = key;
    newn->value = value;
    newn->height = 0;
    newn->left = newn->right = NIL(avl_node);
    return newn;
}


int 
avl_numcmp(const void *x, const void *y)
{
    return (long) x - (long) y;
}

int
avl_check_tree(avl_tree *tree)
{
    int error = 0;
    (void) do_check_tree(tree->root, tree->compar, &error);
    return error;
}


static int
do_check_tree(
  avl_node *node,
  int (*compar)(const void *, const void *),
  int *error)
{
    int l_height, r_height, comp_height, bal;
    
    if (node == NIL(avl_node)) {
        return -1;
    }

    r_height = do_check_tree(node->right, compar, error);
    l_height = do_check_tree(node->left, compar, error);

    comp_height = MAX(l_height, r_height) + 1;
    bal = r_height - l_height;
    
    if (comp_height != node->height) {
        (void) printf("Bad height for 0x%p: computed=%d stored=%d\n",
            (void *) node, comp_height, node->height);
        ++*error;
    }

    if (bal > 1 || bal < -1) {
        (void) printf("Out of balance at node 0x%p, balance = %d\n", 
            (void *) node, bal);
        ++*error;
    }

    if (node->left != NIL(avl_node) && 
                    (*compar)(node->left->key, node->key) > 0) {
        (void) printf("Bad ordering between 0x%p and 0x%p", 
            (void *) node, (void *) node->left);
        ++*error;
    }
    
    if (node->right != NIL(avl_node) && 
                    (*compar)(node->key, node->right->key) > 0) {
        (void) printf("Bad ordering between 0x%p and 0x%p", 
            (void *) node, (void *) node->right);
        ++*error;
    }

    return comp_height;
}

---