common/isc/tree.c

#ifndef LINT
static const char rcsid[] = "$Id: tree.c,v 1.4 2005/04/27 04:56:39 sra Exp $";
#endif

/*%
 * tree - balanced binary tree library
 *
 * vix 05apr94 [removed vixie.h dependencies; cleaned up formatting, names]
 * vix 22jan93 [revisited; uses RCS, ANSI, POSIX; has bug fixes]
 * vix 23jun86 [added delete uar to add for replaced nodes]
 * vix 20jun86 [added tree_delete per wirth a+ds (mod2 v.) p. 224]
 * vix 06feb86 [added tree_mung()]
 * vix 02feb86 [added tree balancing from wirth "a+ds=p" p. 220-221]
 * vix 14dec85 [written]
 */

/*%
 * This program text was created by Paul Vixie using examples from the book:
 * "Algorithms & Data Structures," Niklaus Wirth, Prentice-Hall, 1986, ISBN
 * 0-13-022005-1.  Any errors in the conversion from Modula-2 to C are Paul
 * Vixie's.
 */

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Portions Copyright (c) 1996-1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*#define       DEBUG   "tree"*/

#include "port_before.h"

#include <stdio.h>
#include <stdlib.h>

#include "port_after.h"

#include <isc/memcluster.h>
#include <isc/tree.h>

#ifdef DEBUG
static int  debugDepth = 0;
static char *debugFuncs[256];
# define ENTER(proc) { \
            debugFuncs[debugDepth] = proc; \
            fprintf(stderr, "ENTER(%d:%s.%s)\n", \
                debugDepth, DEBUG, \
                debugFuncs[debugDepth]); \
            debugDepth++; \
        }
# define RET(value) { \
            debugDepth--; \
            fprintf(stderr, "RET(%d:%s.%s)\n", \
                debugDepth, DEBUG, \
                debugFuncs[debugDepth]); \
            return (value); \
        }
# define RETV { \
            debugDepth--; \
            fprintf(stderr, "RETV(%d:%s.%s)\n", \
                debugDepth, DEBUG, \
                debugFuncs[debugDepth]); \
            return; \
        }
# define MSG(msg)   fprintf(stderr, "MSG(%s)\n", msg);
#else
# define ENTER(proc)    ;
# define RET(value) return (value);
# define RETV       return;
# define MSG(msg)   ;
#endif

#ifndef TRUE
# define TRUE       1
# define FALSE      0
#endif

static tree *   sprout(tree **, tree_t, int *, int (*)(), void (*)());
static int  delete(tree **, int (*)(), tree_t, void (*)(), int *, int *);
static void del(tree **, int *, tree **, void (*)(), int *);
static void bal_L(tree **, int *);
static void bal_R(tree **, int *);

void
tree_init(tree **ppr_tree) {
    ENTER("tree_init")
    *ppr_tree = NULL;
    RETV
}

tree_t
tree_srch(tree **ppr_tree, int (*pfi_compare)(tree_t, tree_t), tree_t   p_user) {
    ENTER("tree_srch")

    if (*ppr_tree) {
        int i_comp = (*pfi_compare)(p_user, (**ppr_tree).data);

        if (i_comp > 0)
            RET(tree_srch(&(**ppr_tree).right,
                      pfi_compare,
                      p_user))

        if (i_comp < 0)
            RET(tree_srch(&(**ppr_tree).left,
                      pfi_compare,
                      p_user))

        /* not higher, not lower... this must be the one.
         */
        RET((**ppr_tree).data)
    }

    /* grounded. NOT found.
     */
    RET(NULL)
}

tree_t
tree_add(tree **ppr_tree, int (*pfi_compare)(tree_t, tree_t),
     tree_t p_user, void (*pfv_uar)())
{
    int i_balance = FALSE;

    ENTER("tree_add")
    if (!sprout(ppr_tree, p_user, &i_balance, pfi_compare, pfv_uar))
        RET(NULL)
    RET(p_user)
}

int
tree_delete(tree **ppr_p, int (*pfi_compare)(tree_t, tree_t),
        tree_t p_user, void (*pfv_uar)())
{
    int i_balance = FALSE, i_uar_called = FALSE;

    ENTER("tree_delete");
    RET(delete(ppr_p, pfi_compare, p_user, pfv_uar,
           &i_balance, &i_uar_called))
}

int
tree_trav(tree **ppr_tree, int (*pfi_uar)(tree_t)) {
    ENTER("tree_trav")

    if (!*ppr_tree)
        RET(TRUE)

    if (!tree_trav(&(**ppr_tree).left, pfi_uar))
        RET(FALSE)
    if (!(*pfi_uar)((**ppr_tree).data))
        RET(FALSE)
    if (!tree_trav(&(**ppr_tree).right, pfi_uar))
        RET(FALSE)
    RET(TRUE)
}

void
tree_mung(tree **ppr_tree, void (*pfv_uar)(tree_t)) {
    ENTER("tree_mung")
    if (*ppr_tree) {
        tree_mung(&(**ppr_tree).left, pfv_uar);
        tree_mung(&(**ppr_tree).right, pfv_uar);
        if (pfv_uar)
            (*pfv_uar)((**ppr_tree).data);
        memput(*ppr_tree, sizeof(tree));
        *ppr_tree = NULL;
    }
    RETV
}

static tree *
sprout(tree **ppr, tree_t p_data, int *pi_balance,
       int (*pfi_compare)(tree_t, tree_t), void (*pfv_delete)(tree_t))
{
    tree *p1, *p2, *sub;
    int cmp;

    ENTER("sprout")

    /* are we grounded?  if so, add the node "here" and set the rebalance
     * flag, then exit.
     */
    if (!*ppr) {
        MSG("grounded. adding new node, setting h=true")
        *ppr = (tree *) memget(sizeof(tree));
        if (*ppr) {
            (*ppr)->left = NULL;
            (*ppr)->right = NULL;
            (*ppr)->bal = 0;
            (*ppr)->data = p_data;
            *pi_balance = TRUE;
        }
        RET(*ppr);
    }

    /* compare the data using routine passed by caller.
     */
    cmp = (*pfi_compare)(p_data, (*ppr)->data);

    /* if LESS, prepare to move to the left.
     */
    if (cmp < 0) {
        MSG("LESS. sprouting left.")
        sub = sprout(&(*ppr)->left, p_data, pi_balance,
                 pfi_compare, pfv_delete);
        if (sub && *pi_balance) {   /*%< left branch has grown */
            MSG("LESS: left branch has grown")
            switch ((*ppr)->bal) {
            case 1:
                /* right branch WAS longer; bal is ok now */
                MSG("LESS: case 1.. bal restored implicitly")
                (*ppr)->bal = 0;
                *pi_balance = FALSE;
                break;
            case 0:
                /* balance WAS okay; now left branch longer */
                MSG("LESS: case 0.. balnce bad but still ok")
                (*ppr)->bal = -1;
                break;
            case -1:
                /* left branch was already too long. rebal */
                MSG("LESS: case -1: rebalancing")
                p1 = (*ppr)->left;
                if (p1->bal == -1) {        /*%< LL */
                    MSG("LESS: single LL")
                    (*ppr)->left = p1->right;
                    p1->right = *ppr;
                    (*ppr)->bal = 0;
                    *ppr = p1;
                } else {            /*%< double LR */
                    MSG("LESS: double LR")

                    p2 = p1->right;
                    p1->right = p2->left;
                    p2->left = p1;

                    (*ppr)->left = p2->right;
                    p2->right = *ppr;

                    if (p2->bal == -1)
                        (*ppr)->bal = 1;
                    else
                        (*ppr)->bal = 0;

                    if (p2->bal == 1)
                        p1->bal = -1;
                    else
                        p1->bal = 0;
                    *ppr = p2;
                } /*else*/
                (*ppr)->bal = 0;
                *pi_balance = FALSE;
            } /*switch*/
        } /*if*/
        RET(sub)
    } /*if*/

    /* if MORE, prepare to move to the right.
     */
    if (cmp > 0) {
        MSG("MORE: sprouting to the right")
        sub = sprout(&(*ppr)->right, p_data, pi_balance,
                 pfi_compare, pfv_delete);
        if (sub && *pi_balance) {
            MSG("MORE: right branch has grown")

            switch ((*ppr)->bal) {
            case -1:
                MSG("MORE: balance was off, fixed implicitly")
                (*ppr)->bal = 0;
                *pi_balance = FALSE;
                break;
            case 0:
                MSG("MORE: balance was okay, now off but ok")
                (*ppr)->bal = 1;
                break;
            case 1:
                MSG("MORE: balance was off, need to rebalance")
                p1 = (*ppr)->right;
                if (p1->bal == 1) {     /*%< RR */
                    MSG("MORE: single RR")
                    (*ppr)->right = p1->left;
                    p1->left = *ppr;
                    (*ppr)->bal = 0;
                    *ppr = p1;
                } else {            /*%< double RL */
                    MSG("MORE: double RL")

                    p2 = p1->left;
                    p1->left = p2->right;
                    p2->right = p1;

                    (*ppr)->right = p2->left;
                    p2->left = *ppr;

                    if (p2->bal == 1)
                        (*ppr)->bal = -1;
                    else
                        (*ppr)->bal = 0;

                    if (p2->bal == -1)
                        p1->bal = 1;
                    else
                        p1->bal = 0;

                    *ppr = p2;
                } /*else*/
                (*ppr)->bal = 0;
                *pi_balance = FALSE;
            } /*switch*/
        } /*if*/
        RET(sub)
    } /*if*/

    /* not less, not more: this is the same key!  replace...
     */
    MSG("FOUND: Replacing data value")
    *pi_balance = FALSE;
    if (pfv_delete)
        (*pfv_delete)((*ppr)->data);
    (*ppr)->data = p_data;
    RET(*ppr)
}

static int
delete(tree **ppr_p, int (*pfi_compare)(tree_t, tree_t), tree_t p_user,
       void (*pfv_uar)(tree_t), int *pi_balance, int *pi_uar_called)
{
    tree *pr_q;
    int i_comp, i_ret;

    ENTER("delete")

    if (*ppr_p == NULL) {
        MSG("key not in tree")
        RET(FALSE)
    }

    i_comp = (*pfi_compare)((*ppr_p)->data, p_user);
    if (i_comp > 0) {
        MSG("too high - scan left")
        i_ret = delete(&(*ppr_p)->left, pfi_compare, p_user, pfv_uar,
                   pi_balance, pi_uar_called);
        if (*pi_balance)
            bal_L(ppr_p, pi_balance);
    } else if (i_comp < 0) {
        MSG("too low - scan right")
        i_ret = delete(&(*ppr_p)->right, pfi_compare, p_user, pfv_uar,
                   pi_balance, pi_uar_called);
        if (*pi_balance)
            bal_R(ppr_p, pi_balance);
    } else {
        MSG("equal")
        pr_q = *ppr_p;
        if (pr_q->right == NULL) {
            MSG("right subtree null")
            *ppr_p = pr_q->left;
            *pi_balance = TRUE;
        } else if (pr_q->left == NULL) {
            MSG("right subtree non-null, left subtree null")
            *ppr_p = pr_q->right;
            *pi_balance = TRUE;
        } else {
            MSG("neither subtree null")
            del(&pr_q->left, pi_balance, &pr_q,
                pfv_uar, pi_uar_called);
            if (*pi_balance)
                bal_L(ppr_p, pi_balance);
        }
        if (!*pi_uar_called && pfv_uar)
            (*pfv_uar)(pr_q->data);
        /* Thanks to wuth@castrov.cuc.ab.ca for the following stmt. */
        memput(pr_q, sizeof(tree));
        i_ret = TRUE;
    }
    RET(i_ret)
}

static void
del(tree **ppr_r, int *pi_balance, tree **ppr_q,
    void (*pfv_uar)(tree_t), int *pi_uar_called)
{
    ENTER("del")

    if ((*ppr_r)->right != NULL) {
        del(&(*ppr_r)->right, pi_balance, ppr_q,
            pfv_uar, pi_uar_called);
        if (*pi_balance)
            bal_R(ppr_r, pi_balance);
    } else {
        if (pfv_uar)
            (*pfv_uar)((*ppr_q)->data);
        *pi_uar_called = TRUE;
        (*ppr_q)->data = (*ppr_r)->data;
        *ppr_q = *ppr_r;
        *ppr_r = (*ppr_r)->left;
        *pi_balance = TRUE;
    }

    RETV
}

static void
bal_L(tree **ppr_p, int *pi_balance) {
    tree *p1, *p2;
    int b1, b2;

    ENTER("bal_L")
    MSG("left branch has shrunk")

    switch ((*ppr_p)->bal) {
    case -1:
        MSG("was imbalanced, fixed implicitly")
        (*ppr_p)->bal = 0;
        break;
    case 0:
        MSG("was okay, is now one off")
        (*ppr_p)->bal = 1;
        *pi_balance = FALSE;
        break;
    case 1:
        MSG("was already off, this is too much")
        p1 = (*ppr_p)->right;
        b1 = p1->bal;
        if (b1 >= 0) {
            MSG("single RR")
            (*ppr_p)->right = p1->left;
            p1->left = *ppr_p;
            if (b1 == 0) {
                MSG("b1 == 0")
                (*ppr_p)->bal = 1;
                p1->bal = -1;
                *pi_balance = FALSE;
            } else {
                MSG("b1 != 0")
                (*ppr_p)->bal = 0;
                p1->bal = 0;
            }
            *ppr_p = p1;
        } else {
            MSG("double RL")
            p2 = p1->left;
            b2 = p2->bal;
            p1->left = p2->right;
            p2->right = p1;
            (*ppr_p)->right = p2->left;
            p2->left = *ppr_p;
            if (b2 == 1)
                (*ppr_p)->bal = -1;
            else
                (*ppr_p)->bal = 0;
            if (b2 == -1)
                p1->bal = 1;
            else
                p1->bal = 0;
            *ppr_p = p2;
            p2->bal = 0;
        }
    }
    RETV
}

static void
bal_R(tree **ppr_p, int *pi_balance) {
    tree *p1, *p2;
    int b1, b2;

    ENTER("bal_R")
    MSG("right branch has shrunk")
    switch ((*ppr_p)->bal) {
    case 1:
        MSG("was imbalanced, fixed implicitly")
        (*ppr_p)->bal = 0;
        break;
    case 0:
        MSG("was okay, is now one off")
        (*ppr_p)->bal = -1;
        *pi_balance = FALSE;
        break;
    case -1:
        MSG("was already off, this is too much")
        p1 = (*ppr_p)->left;
        b1 = p1->bal;
        if (b1 <= 0) {
            MSG("single LL")
            (*ppr_p)->left = p1->right;
            p1->right = *ppr_p;
            if (b1 == 0) {
                MSG("b1 == 0")
                (*ppr_p)->bal = -1;
                p1->bal = 1;
                *pi_balance = FALSE;
            } else {
                MSG("b1 != 0")
                (*ppr_p)->bal = 0;
                p1->bal = 0;
            }
            *ppr_p = p1;
        } else {
            MSG("double LR")
            p2 = p1->right;
            b2 = p2->bal;
            p1->right = p2->left;
            p2->left = p1;
            (*ppr_p)->left = p2->right;
            p2->right = *ppr_p;
            if (b2 == -1)
                (*ppr_p)->bal = 1;
            else
                (*ppr_p)->bal = 0;
            if (b2 == 1)
                p1->bal = -1;
            else
                p1->bal = 0;
            *ppr_p = p2;
            p2->bal = 0;
        }
    }
    RETV
}

/*! \file */