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/* avl.c - routines to implement an avl tree */
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/* $OpenLDAP: pkg/ldap/libraries/liblutil/avl.c,v 1.9.2.3 2008/02/11 23:26:42 kurt Exp $ */
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/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
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* Copyright 1998-2008 The OpenLDAP Foundation.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted only as authorized by the OpenLDAP
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* A copy of this license is available in the file LICENSE in the
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* top-level directory of the distribution or, alternatively, at
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* <http://www.OpenLDAP.org/license.html>.
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/* Portions Copyright (c) 1993 Regents of the University of Michigan.
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* All rights reserved.
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* Redistribution and use in source and binary forms are permitted
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* provided that this notice is preserved and that due credit is given
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* to the University of Michigan at Ann Arbor. The name of the University
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* may not be used to endorse or promote products derived from this
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* software without specific prior written permission. This software
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* is provided ``as is'' without express or implied warranty.
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* This work was originally developed by the University of Michigan
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* (as part of U-MICH LDAP). Additional significant contributors
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* Hallvard B. Furuseth
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#include <ac/stdlib.h>
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#define ber_memalloc malloc
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#define ber_memrealloc realloc
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#define ber_memfree free
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static const int avl_bfs[] = {LH, RH};
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* avl_insert -- insert a node containing data data into the avl tree
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* with root root. fcmp is a function to call to compare the data portion
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* of two nodes. it should take two arguments and return <, >, or == 0,
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* depending on whether its first argument is <, >, or == its second
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* argument (like strcmp, e.g.). fdup is a function to call when a duplicate
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* node is inserted. it should return 0, or -1 and its return value
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* will be the return value from avl_insert in the case of a duplicate node.
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* the function will be called with the original node's data as its first
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* argument and with the incoming duplicate node's data as its second
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* argument. this could be used, for example, to keep a count with each
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* NOTE: this routine may malloc memory
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avl_insert( Avlnode ** root, void *data, AVL_CMP fcmp, AVL_DUP fdup )
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Avlnode *t, *p, *s, *q, *r;
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if ( *root == NULL ) {
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if (( r = (Avlnode *) ber_memalloc( sizeof( Avlnode ))) == NULL ) {
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r->avl_link[0] = r->avl_link[1] = NULL;
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/* find insertion point */
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cmp = fcmp( data, p->avl_data );
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return (*fdup)( p->avl_data, data );
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if (( q = (Avlnode *) ber_memalloc( sizeof( Avlnode ))) == NULL ) {
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q->avl_link[0] = q->avl_link[1] = NULL;
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p->avl_link[cmp] = q;
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} else if ( q->avl_bf ) {
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/* adjust balance factors */
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cmp = fcmp( data, s->avl_data ) > 0;
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r = p = s->avl_link[cmp];
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cmp = fcmp( data, p->avl_data ) > 0;
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p->avl_bf = avl_bfs[cmp];
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p = p->avl_link[cmp];
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/* checks and balances */
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if ( s->avl_bf == EH ) {
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} else if ( s->avl_bf == -a ) {
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} else if ( s->avl_bf == a ) {
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if ( r->avl_bf == a ) {
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/* single rotation */
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s->avl_link[cmp] = r->avl_link[ncmp];
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r->avl_link[ncmp] = s;
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} else if ( r->avl_bf == -a ) {
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/* double rotation */
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p = r->avl_link[ncmp];
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r->avl_link[ncmp] = p->avl_link[cmp];
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p->avl_link[cmp] = r;
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s->avl_link[cmp] = p->avl_link[ncmp];
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p->avl_link[ncmp] = s;
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if ( p->avl_bf == a ) {
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} else if ( p->avl_bf == -a ) {
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else if ( s == t->avl_right )
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avl_delete( Avlnode **root, void* data, AVL_CMP fcmp )
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Avlnode *p, *q, *r, *top;
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int side, side_bf, shorter, nside;
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Avlnode *pptr[sizeof(void *)*8];
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unsigned char pdir[sizeof(void *)*8];
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side = fcmp( data, p->avl_data );
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p = p->avl_link[side];
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/* If this node has two children, swap so we are deleting a node with
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if ( p->avl_link[0] && p->avl_link[1] ) {
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/* find the immediate predecessor <q> */
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while (q->avl_link[1]) {
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p->avl_link[0] = q->avl_link[0];
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q->avl_link[1] = p->avl_link[1];
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p->avl_link[1] = NULL;
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q->avl_bf = p->avl_bf;
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/* fix stack positions: old parent of p points to q */
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r->avl_link[pdir[side-1]] = q;
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/* new parent of p points to p */
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if ( depth-side > 1 ) {
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/* now <p> has at most one child, get it */
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q = p->avl_link[0] ? p->avl_link[0] : p->avl_link[1];
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/* set the child into p's parent */
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p->avl_link[side] = q;
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side_bf = avl_bfs[side];
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/* case 1: height unchanged */
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if ( p->avl_bf == EH ) {
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/* Tree is now heavier on opposite side */
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p->avl_bf = avl_bfs[nside];
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} else if ( p->avl_bf == side_bf ) {
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/* case 2: taller subtree shortened, height reduced */
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/* case 3: shorter subtree shortened */
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top = pptr[depth-1]; /* p->parent; */
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/* set <q> to the taller of the two subtrees of <p> */
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q = p->avl_link[nside];
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if ( q->avl_bf == EH ) {
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/* case 3a: height unchanged, single rotate */
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p->avl_link[nside] = q->avl_link[side];
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q->avl_link[side] = p;
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p->avl_bf = (- side_bf);
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} else if ( q->avl_bf == p->avl_bf ) {
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/* case 3b: height reduced, single rotate */
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p->avl_link[nside] = q->avl_link[side];
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q->avl_link[side] = p;
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/* case 3c: height reduced, balance factors opposite */
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r = q->avl_link[side];
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q->avl_link[side] = r->avl_link[nside];
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r->avl_link[nside] = q;
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p->avl_link[nside] = r->avl_link[side];
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r->avl_link[side] = p;
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if ( r->avl_bf == side_bf ) {
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q->avl_bf = (- side_bf);
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} else if ( r->avl_bf == (- side_bf)) {
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/* a rotation has caused <q> (or <r> in case 3c) to become
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* the root. let <p>'s former parent know this.
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} else if (top->avl_link[0] == p) {
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top->avl_link[0] = q;
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top->avl_link[1] = q;
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} /* end while(shorter) */
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avl_inapply( Avlnode *root, AVL_APPLY fn, void* arg, int stopflag )
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return( AVL_NOMORE );
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if ( root->avl_left != 0 )
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if ( avl_inapply( root->avl_left, fn, arg, stopflag )
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if ( (*fn)( root->avl_data, arg ) == stopflag )
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if ( root->avl_right == 0 )
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return( AVL_NOMORE );
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return( avl_inapply( root->avl_right, fn, arg, stopflag ) );
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avl_postapply( Avlnode *root, AVL_APPLY fn, void* arg, int stopflag )
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return( AVL_NOMORE );
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if ( root->avl_left != 0 )
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if ( avl_postapply( root->avl_left, fn, arg, stopflag )
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if ( root->avl_right != 0 )
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if ( avl_postapply( root->avl_right, fn, arg, stopflag )
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return( (*fn)( root->avl_data, arg ) );
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avl_preapply( Avlnode *root, AVL_APPLY fn, void* arg, int stopflag )
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return( AVL_NOMORE );
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if ( (*fn)( root->avl_data, arg ) == stopflag )
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if ( root->avl_left != 0 )
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if ( avl_preapply( root->avl_left, fn, arg, stopflag )
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if ( root->avl_right == 0 )
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return( AVL_NOMORE );
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return( avl_preapply( root->avl_right, fn, arg, stopflag ) );
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* avl_apply -- avl tree root is traversed, function fn is called with
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* arguments arg and the data portion of each node. if fn returns stopflag,
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* the traversal is cut short, otherwise it continues. Do not use -6 as
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* a stopflag, as this is what is used to indicate the traversal ran out
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avl_apply( Avlnode *root, AVL_APPLY fn, void* arg, int stopflag, int type )
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return( avl_inapply( root, fn, arg, stopflag ) );
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return( avl_preapply( root, fn, arg, stopflag ) );
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return( avl_postapply( root, fn, arg, stopflag ) );
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fprintf( stderr, "Invalid traversal type %d\n", type );
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* avl_prefixapply - traverse avl tree root, applying function fprefix
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* to any nodes that match. fcmp is called with data as its first arg
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* and the current node's data as its second arg. it should return
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* 0 if they match, < 0 if data is less, and > 0 if data is greater.
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* the idea is to efficiently find all nodes that are prefixes of
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* some key... Like avl_apply, this routine also takes a stopflag
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* and will return prematurely if fmatch returns this value. Otherwise,
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* AVL_NOMORE is returned.
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return( AVL_NOMORE );
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cmp = (*fcmp)( data, root->avl_data /* , carg */);
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if ( (*fmatch)( root->avl_data, marg ) == stopflag )
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if ( root->avl_left != 0 )
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if ( avl_prefixapply( root->avl_left, data, fmatch,
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marg, fcmp, carg, stopflag ) == stopflag )
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if ( root->avl_right != 0 )
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return( avl_prefixapply( root->avl_right, data, fmatch,
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marg, fcmp, carg, stopflag ) );
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return( AVL_NOMORE );
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} else if ( cmp < 0 ) {
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if ( root->avl_left != 0 )
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return( avl_prefixapply( root->avl_left, data, fmatch,
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marg, fcmp, carg, stopflag ) );
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if ( root->avl_right != 0 )
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return( avl_prefixapply( root->avl_right, data, fmatch,
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marg, fcmp, carg, stopflag ) );
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return( AVL_NOMORE );
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* avl_free -- traverse avltree root, freeing the memory it is using.
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* the dfree() is called to free the data portion of each node. The
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* number of items actually freed is returned.
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avl_free( Avlnode *root, AVL_FREE dfree )
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if ( root->avl_left != 0 )
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nleft = avl_free( root->avl_left, dfree );
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if ( root->avl_right != 0 )
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nright = avl_free( root->avl_right, dfree );
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(*dfree)( root->avl_data );
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return( nleft + nright + 1 );
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* avl_find -- search avltree root for a node with data data. the function
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* cmp is used to compare things. it is called with data as its first arg
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* and the current node data as its second. it should return 0 if they match,
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* < 0 if arg1 is less than arg2 and > 0 if arg1 is greater than arg2.
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avl_find2( Avlnode *root, const void *data, AVL_CMP fcmp )
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while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
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root = root->avl_link[cmp];
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avl_find( Avlnode *root, const void* data, AVL_CMP fcmp )
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while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
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root = root->avl_link[cmp];
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return( root ? root->avl_data : 0 );
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* avl_find_lin -- search avltree root linearly for a node with data data.
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* the function cmp is used to compare things. it is called with data as its
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* first arg and the current node data as its second. it should return 0 if
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* they match, non-zero otherwise.
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avl_find_lin( Avlnode *root, const void* data, AVL_CMP fcmp )
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if ( (*fcmp)( data, root->avl_data ) == 0 )
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return( root->avl_data );
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if ( root->avl_left != 0 )
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if ( (res = avl_find_lin( root->avl_left, data, fcmp ))
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if ( root->avl_right == 0 )
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return( avl_find_lin( root->avl_right, data, fcmp ) );
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/* NON-REENTRANT INTERFACE */
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static void* *avl_list;
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static int avl_maxlist;
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static int avl_nextlist;
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#define AVL_GRABSIZE 100
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avl_buildlist( void* data, void* arg )
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if ( avl_list == (void* *) 0 ) {
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avl_list = (void* *) ber_memalloc(AVL_GRABSIZE * sizeof(void*));
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slots = AVL_GRABSIZE;
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} else if ( avl_maxlist == slots ) {
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slots += AVL_GRABSIZE;
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avl_list = (void* *) ber_memrealloc( (char *) avl_list,
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(unsigned) slots * sizeof(void*));
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avl_list[ avl_maxlist++ ] = data;
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* avl_getfirst() and avl_getnext() are provided as alternate tree
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* traversal methods, to be used when a single function cannot be
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* provided to be called with every node in the tree. avl_getfirst()
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* traverses the tree and builds a linear list of all the nodes,
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* returning the first node. avl_getnext() returns the next thing
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* on the list built by avl_getfirst(). This means that avl_getfirst()
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* can take a while, and that the tree should not be messed with while
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* being traversed in this way, and that multiple traversals (even of
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* different trees) cannot be active at once.
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avl_getfirst( Avlnode *root )
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ber_memfree( (char *) avl_list);
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avl_list = (void* *) 0;
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(void) avl_apply( root, avl_buildlist, (void*) 0, -1, AVL_INORDER );
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return( avl_list[ avl_nextlist++ ] );
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if ( avl_nextlist == avl_maxlist ) {
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ber_memfree( (void*) avl_list);
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avl_list = (void* *) 0;
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return( avl_list[ avl_nextlist++ ] );
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/* end non-reentrant code */
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avl_dup_error( void* left, void* right )
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avl_dup_ok( void* left, void* right )
added
removed
libraries/liblutil/avl.c
