git.sur5r.net Git - openldap/blob - libraries/liblutil/tavl.c

   1 /* avl.c - routines to implement an avl tree */
   2 /* $OpenLDAP$ */
   3 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
   4  *
   5  * Copyright 2005 The OpenLDAP Foundation.
   6  * Portions Copyright (c) 2005 by Howard Chu, Symas Corp.
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted only as authorized by the OpenLDAP
  11  * Public License.
  12  *
  13  * A copy of this license is available in the file LICENSE in the
  14  * top-level directory of the distribution or, alternatively, at
  15  * <http://www.OpenLDAP.org/license.html>.
  16  */
  17 /* ACKNOWLEDGEMENTS:
  18  * This work was initially developed by Howard Chu for inclusion
  19  * in OpenLDAP software.
  20  */
  21
  22 #include "portable.h"
  23
  24 #include <stdio.h>
  25 #include <ac/stdlib.h>
  26
  27 #ifdef CSRIMALLOC
  28 #define ber_memalloc malloc
  29 #define ber_memrealloc realloc
  30 #define ber_memfree free
  31 #else
  32 #include "lber.h"
  33 #endif
  34
  35 #define AVL_INTERNAL
  36 #include "avl.h"
  37
  38 static const int avl_bfs[] = {LH, RH};
  39
  40 /*
  41  * Threaded AVL trees - for fast in-order traversal of nodes.
  42  */
  43 /*
  44  * tavl_insert -- insert a node containing data data into the avl tree
  45  * with root root.  fcmp is a function to call to compare the data portion
  46  * of two nodes.  it should take two arguments and return <, >, or == 0,
  47  * depending on whether its first argument is <, >, or == its second
  48  * argument (like strcmp, e.g.).  fdup is a function to call when a duplicate
  49  * node is inserted.  it should return 0, or -1 and its return value
  50  * will be the return value from avl_insert in the case of a duplicate node.
  51  * the function will be called with the original node's data as its first
  52  * argument and with the incoming duplicate node's data as its second
  53  * argument.  this could be used, for example, to keep a count with each
  54  * node.
  55  *
  56  * NOTE: this routine may malloc memory
  57  */
  58 int
  59 tavl_insert( Avlnode ** root, void *data, AVL_CMP fcmp, AVL_DUP fdup )
  60 {
  61     Avlnode *t, *p, *s, *q, *r;
  62     int a, cmp, ncmp;
  63
  64         if ( *root == NULL ) {
  65                 if (( r = (Avlnode *) ber_memalloc( sizeof( Avlnode ))) == NULL ) {
  66                         return( -1 );
  67                 }
  68                 r->avl_link[0] = r->avl_link[1] = NULL;
  69                 r->avl_data = data;
  70                 r->avl_bf = EH;
  71                 r->avl_bits[0] = r->avl_bits[1] = AVL_THREAD;
  72                 *root = r;
  73
  74                 return( 0 );
  75         }
  76
  77     t = NULL;
  78     s = p = *root;
  79
  80         /* find insertion point */
  81     while (1) {
  82                 cmp = fcmp( data, p->avl_data );
  83                 if ( cmp == 0 )
  84                         return (*fdup)( p->avl_data, data );
  85
  86                 cmp = (cmp > 0);
  87                 q = avl_child( p, cmp );
  88                 if (q == NULL) {
  89                         /* insert */
  90                         if (( q = (Avlnode *) ber_memalloc( sizeof( Avlnode ))) == NULL ) {
  91                                 return( -1 );
  92                         }
  93                         q->avl_link[cmp] = p->avl_link[cmp];
  94                         q->avl_link[!cmp] = p;
  95                         q->avl_data = data;
  96                         q->avl_bf = EH;
  97                         q->avl_bits[0] = q->avl_bits[1] = AVL_THREAD;
  98
  99                         p->avl_link[cmp] = q;
 100                         p->avl_bits[cmp] = AVL_CHILD;
 101                         break;
 102                 } else if ( q->avl_bf ) {
 103                         t = p;
 104                         s = q;
 105                 }
 106                 p = q;
 107     }
 108
 109     /* adjust balance factors */
 110     cmp = fcmp( data, s->avl_data ) > 0;
 111         r = p = s->avl_link[cmp];
 112         a = avl_bfs[cmp];
 113
 114         while ( p != q ) {
 115                 cmp = fcmp( data, p->avl_data ) > 0;
 116                 p->avl_bf = avl_bfs[cmp];
 117                 p = p->avl_link[cmp];
 118         }
 119
 120         /* checks and balances */
 121
 122         if ( s->avl_bf == EH ) {
 123                 s->avl_bf = a;
 124                 return 0;
 125         } else if ( s->avl_bf == -a ) {
 126                 s->avl_bf = EH;
 127                 return 0;
 128     } else if ( s->avl_bf == a ) {
 129                 cmp = (a > 0);
 130                 ncmp = !cmp;
 131                 if ( r->avl_bf == a ) {
 132                         /* single rotation */
 133                         p = r;
 134                         if ( r->avl_bits[ncmp] == AVL_THREAD ) {
 135                                 r->avl_bits[ncmp] = AVL_CHILD;
 136                                 s->avl_bits[cmp] = AVL_THREAD;
 137                         } else {
 138                                 s->avl_link[cmp] = r->avl_link[ncmp];
 139                                 r->avl_link[ncmp] = s;
 140                         }
 141                         s->avl_bf = 0;
 142                         r->avl_bf = 0;
 143                 } else if ( r->avl_bf == -a ) {
 144                         /* double rotation */
 145                         p = r->avl_link[ncmp];
 146                         if ( p->avl_bits[cmp] == AVL_THREAD ) {
 147                                 p->avl_bits[cmp] = AVL_CHILD;
 148                                 r->avl_bits[ncmp] = AVL_THREAD;
 149                         } else {
 150                                 r->avl_link[ncmp] = p->avl_link[cmp];
 151                                 p->avl_link[cmp] = r;
 152                         }
 153                         if ( p->avl_bits[ncmp] == AVL_THREAD ) {
 154                                 p->avl_bits[ncmp] = AVL_CHILD;
 155                                 s->avl_link[cmp] = p;
 156                                 s->avl_bits[cmp] = AVL_THREAD;
 157                         } else {
 158                                 s->avl_link[cmp] = p->avl_link[ncmp];
 159                                 p->avl_link[ncmp] = s;
 160                         }
 161                         if ( p->avl_bf == a ) {
 162                                 s->avl_bf = -a;
 163                                 r->avl_bf = 0;
 164                         } else if ( p->avl_bf == -a ) {
 165                                 s->avl_bf = 0;
 166                                 r->avl_bf = a;
 167                         } else {
 168                                 s->avl_bf = 0;
 169                                 r->avl_bf = 0;
 170                         }
 171                         p->avl_bf = 0;
 172                 }
 173                 /* Update parent */
 174                 if ( t == NULL )
 175                         *root = p;
 176                 else if ( s == t->avl_right )
 177                         t->avl_right = p;
 178                 else
 179                         t->avl_left = p;
 180     }
 181
 182   return 0;
 183 }
 184
 185 void*
 186 tavl_delete( Avlnode **root, void* data, AVL_CMP fcmp )
 187 {
 188         Avlnode *p, *q, *r, *s, *top;
 189         int side, side_bf, shorter, nside;
 190
 191         /* parent stack */
 192         Avlnode *pptr[sizeof(void *)*8];
 193         unsigned char pdir[sizeof(void *)*8];
 194         int depth = 0;
 195
 196         if ( *root == NULL )
 197                 return NULL;
 198
 199         p = *root;
 200
 201         while (1) {
 202                 side = fcmp( data, p->avl_data );
 203                 if ( !side )
 204                         break;
 205                 side = ( side > 0 );
 206                 pdir[depth] = side;
 207                 pptr[depth++] = p;
 208
 209                 if ( p->avl_bits[side] == AVL_THREAD )
 210                         return NULL;
 211                 p = p->avl_link[side];
 212         }
 213         data = p->avl_data;
 214
 215         /* If this node has two children, swap so we are deleting a node with
 216          * at most one child.
 217          */
 218         if ( p->avl_bits[0] == AVL_CHILD && p->avl_bits[1] == AVL_CHILD &&
 219                 p->avl_link[0] && p->avl_link[1] ) {
 220
 221                 /* find the immediate predecessor <q> */
 222                 q = p->avl_link[0];
 223                 pdir[depth] = 0;
 224                 pptr[depth++] = p;
 225                 while (q->avl_bits[1] == AVL_CHILD && q->avl_link[1]) {
 226                         pdir[depth] = 1;
 227                         pptr[depth++] = q;
 228                         q = q->avl_link[1];
 229                 }
 230                 /* swap */
 231                 p->avl_data = q->avl_data;
 232                 p = q;
 233         }
 234
 235         /* now <p> has at most one child, get it */
 236         if ( p->avl_link[0] && p->avl_bits[0] == AVL_CHILD ) {
 237                 q = p->avl_link[0];
 238                 /* Preserve thread continuity */
 239                 r = p->avl_link[1];
 240                 nside = 1;
 241         } else if ( p->avl_link[1] && p->avl_bits[1] == AVL_CHILD ) {
 242                 q = p->avl_link[1];
 243                 r = p->avl_link[0];
 244                 nside = 0;
 245         } else {
 246                 q = NULL;
 247                 if ( depth > 0 )
 248                         r = p->avl_link[pdir[depth-1]];
 249                 else
 250                         r = NULL;
 251         }
 252
 253         ber_memfree( p );
 254
 255         if ( !depth ) {
 256                 *root = q;
 257                 return data;
 258         }
 259
 260         /* set the child into p's parent */
 261         depth--;
 262         p = pptr[depth];
 263         side = pdir[depth];
 264         p->avl_link[side] = q;
 265
 266         /* Update child thread */
 267         if ( q ) {
 268                 for ( ; q->avl_bits[nside] == AVL_CHILD && q->avl_link[nside];
 269                         q = q->avl_link[nside] ) ;
 270                 q->avl_link[nside] = r;
 271         } else {
 272                 p->avl_bits[side] = AVL_THREAD;
 273                 p->avl_link[side] = r;
 274         }
 275
 276         top = NULL;
 277         shorter = 1;
 278
 279         while ( shorter ) {
 280                 p = pptr[depth];
 281                 side = pdir[depth];
 282                 nside = !side;
 283                 side_bf = avl_bfs[side];
 284
 285                 /* case 1: height unchanged */
 286                 if ( p->avl_bf == EH ) {
 287                         /* Tree is now heavier on opposite side */
 288                         p->avl_bf = avl_bfs[nside];
 289                         shorter = 0;
 290
 291                 } else if ( p->avl_bf == side_bf ) {
 292                 /* case 2: taller subtree shortened, height reduced */
 293                         p->avl_bf = EH;
 294                 } else {
 295                 /* case 3: shorter subtree shortened */
 296                         if ( depth )
 297                                 top = pptr[depth-1]; /* p->parent; */
 298                         else
 299                                 top = NULL;
 300                         /* set <q> to the taller of the two subtrees of <p> */
 301                         q = p->avl_link[nside];
 302                         if ( q->avl_bf == EH ) {
 303                                 /* case 3a: height unchanged, single rotate */
 304                                 if ( q->avl_bits[side] == AVL_THREAD ) {
 305                                         q->avl_bits[side] = AVL_CHILD;
 306                                         p->avl_bits[nside] = AVL_THREAD;
 307                                 } else {
 308                                         p->avl_link[nside] = q->avl_link[side];
 309                                         q->avl_link[side] = p;
 310                                 }
 311                                 shorter = 0;
 312                                 q->avl_bf = side_bf;
 313                                 p->avl_bf = (- side_bf);
 314
 315                         } else if ( q->avl_bf == p->avl_bf ) {
 316                                 /* case 3b: height reduced, single rotate */
 317                                 if ( q->avl_bits[side] == AVL_THREAD ) {
 318                                         q->avl_bits[side] = AVL_CHILD;
 319                                         p->avl_bits[nside] = AVL_THREAD;
 320                                 } else {
 321                                         p->avl_link[nside] = q->avl_link[side];
 322                                         q->avl_link[side] = p;
 323                                 }
 324                                 shorter = 1;
 325                                 q->avl_bf = EH;
 326                                 p->avl_bf = EH;
 327
 328                         } else {
 329                                 /* case 3c: height reduced, balance factors opposite */
 330                                 r = q->avl_link[side];
 331                                 if ( r->avl_bits[nside] == AVL_THREAD ) {
 332                                         r->avl_bits[nside] = AVL_CHILD;
 333                                         q->avl_bits[side] = AVL_THREAD;
 334                                 } else {
 335                                         q->avl_link[side] = r->avl_link[nside];
 336                                         r->avl_link[nside] = q;
 337                                 }
 338
 339                                 if ( r->avl_bits[side] == AVL_THREAD ) {
 340                                         r->avl_bits[side] = AVL_CHILD;
 341                                         p->avl_bits[nside] = AVL_THREAD;
 342                                         p->avl_link[nside] = r;
 343                                 } else {
 344                                         p->avl_link[nside] = r->avl_link[side];
 345                                         r->avl_link[side] = p;
 346                                 }
 347
 348                                 if ( r->avl_bf == side_bf ) {
 349                                         q->avl_bf = (- side_bf);
 350                                         p->avl_bf = EH;
 351                                 } else if ( r->avl_bf == (- side_bf)) {
 352                                         q->avl_bf = EH;
 353                                         p->avl_bf = side_bf;
 354                                 } else {
 355                                         q->avl_bf = EH;
 356                                         p->avl_bf = EH;
 357                                 }
 358                                 r->avl_bf = EH;
 359                                 q = r;
 360                         }
 361                         /* a rotation has caused <q> (or <r> in case 3c) to become
 362                          * the root.  let <p>'s former parent know this.
 363                          */
 364                         if ( top == NULL ) {
 365                                 *root = q;
 366                         } else if (top->avl_link[0] == p) {
 367                                 top->avl_link[0] = q;
 368                         } else {
 369                                 top->avl_link[1] = q;
 370                         }
 371                         /* end case 3 */
 372                         p = q;
 373                 }
 374                 if ( !depth )
 375                         break;
 376                 depth--;
 377         } /* end while(shorter) */
 378
 379         return data;
 380 }
 381
 382 /*
 383  * tavl_free -- traverse avltree root, freeing the memory it is using.
 384  * the dfree() is called to free the data portion of each node.  The
 385  * number of items actually freed is returned.
 386  */
 387
 388 int
 389 tavl_free( Avlnode *root, AVL_FREE dfree )
 390 {
 391         int     nleft, nright;
 392
 393         if ( root == 0 )
 394                 return( 0 );
 395
 396         nleft = tavl_free( avl_lchild( root ), dfree );
 397
 398         nright = tavl_free( avl_rchild( root ), dfree );
 399
 400         if ( dfree )
 401                 (*dfree)( root->avl_data );
 402         ber_memfree( root );
 403
 404         return( nleft + nright + 1 );
 405 }
 406
 407 /*
 408  * tavl_find -- search avltree root for a node with data data.  the function
 409  * cmp is used to compare things.  it is called with data as its first arg
 410  * and the current node data as its second.  it should return 0 if they match,
 411  * < 0 if arg1 is less than arg2 and > 0 if arg1 is greater than arg2.
 412  */
 413
 414 Avlnode *
 415 tavl_find2( Avlnode *root, const void *data, AVL_CMP fcmp )
 416 {
 417         int     cmp;
 418
 419         while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
 420                 cmp = cmp > 0;
 421                 root = avl_child( root, cmp );
 422         }
 423         return root;
 424 }
 425
 426 void*
 427 tavl_find( Avlnode *root, const void* data, AVL_CMP fcmp )
 428 {
 429         int     cmp;
 430
 431         while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
 432                 cmp = cmp > 0;
 433                 root = avl_child( root, cmp );
 434         }
 435
 436         return( root ? root->avl_data : 0 );
 437 }
 438
 439 /* Return the leftmost or rightmost node in the tree */
 440 Avlnode *
 441 tavl_end( Avlnode *root, int dir )
 442 {
 443         if ( root ) {
 444                 while ( root->avl_bits[dir] == AVL_CHILD )
 445                         root = root->avl_link[dir];
 446         }
 447         return root;
 448 }
 449
 450 /* Return the next node in the given direction */
 451 Avlnode *
 452 tavl_next( Avlnode *root, int dir )
 453 {
 454         if ( root ) {
 455                 int c = root->avl_bits[dir];
 456
 457                 root = root->avl_link[dir];
 458                 if ( c == AVL_CHILD ) {
 459                         dir ^= 1;
 460                         while ( root->avl_bits[dir] == AVL_CHILD )
 461                                 root = root->avl_link[dir];
 462                 }
 463         }
 464         return root;
 465 }