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 2005-2007 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, *top;
 189         int side, side_bf, shorter, nside = -1;
 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                 side = depth;
 224                 pdir[depth++] = 0;
 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 links */
 231                 r = p->avl_link[0];
 232                 p->avl_link[0] = q->avl_link[0];
 233                 q->avl_link[0] = r;
 234
 235                 q->avl_link[1] = p->avl_link[1];
 236                 p->avl_link[1] = q;
 237
 238                 p->avl_bits[0] = q->avl_bits[0];
 239                 p->avl_bits[1] = q->avl_bits[1];
 240                 q->avl_bits[0] = q->avl_bits[1] = AVL_CHILD;
 241
 242                 q->avl_bf = p->avl_bf;
 243
 244                 /* fix stack positions: old parent of p points to q */
 245                 pptr[side] = q;
 246                 if ( side ) {
 247                         r = pptr[side-1];
 248                         r->avl_link[pdir[side-1]] = q;
 249                 } else {
 250                         *root = q;
 251                 }
 252                 /* new parent of p points to p */
 253                 if ( depth-side > 1 ) {
 254                         r = pptr[depth-1];
 255                         r->avl_link[1] = p;
 256                 } else {
 257                         q->avl_link[0] = p;
 258                 }
 259
 260                 /* fix right subtree: successor of p points to q */
 261                 r = q->avl_link[1];
 262                 while ( r->avl_bits[0] == AVL_CHILD && r->avl_link[0] )
 263                         r = r->avl_link[0];
 264                 r->avl_link[0] = q;
 265         }
 266
 267         /* now <p> has at most one child, get it */
 268         if ( p->avl_link[0] && p->avl_bits[0] == AVL_CHILD ) {
 269                 q = p->avl_link[0];
 270                 /* Preserve thread continuity */
 271                 r = p->avl_link[1];
 272                 nside = 1;
 273         } else if ( p->avl_link[1] && p->avl_bits[1] == AVL_CHILD ) {
 274                 q = p->avl_link[1];
 275                 r = p->avl_link[0];
 276                 nside = 0;
 277         } else {
 278                 q = NULL;
 279                 if ( depth > 0 )
 280                         r = p->avl_link[pdir[depth-1]];
 281                 else
 282                         r = NULL;
 283         }
 284
 285         ber_memfree( p );
 286
 287         /* Update child thread */
 288         if ( q ) {
 289                 for ( ; q->avl_bits[nside] == AVL_CHILD && q->avl_link[nside];
 290                         q = q->avl_link[nside] ) ;
 291                 q->avl_link[nside] = r;
 292         }
 293
 294         if ( !depth ) {
 295                 *root = q;
 296                 return data;
 297         }
 298
 299         /* set the child into p's parent */
 300         depth--;
 301         p = pptr[depth];
 302         side = pdir[depth];
 303         p->avl_link[side] = q;
 304
 305         if ( !q ) {
 306                 p->avl_bits[side] = AVL_THREAD;
 307                 p->avl_link[side] = r;
 308         }
 309
 310         top = NULL;
 311         shorter = 1;
 312
 313         while ( shorter ) {
 314                 p = pptr[depth];
 315                 side = pdir[depth];
 316                 nside = !side;
 317                 side_bf = avl_bfs[side];
 318
 319                 /* case 1: height unchanged */
 320                 if ( p->avl_bf == EH ) {
 321                         /* Tree is now heavier on opposite side */
 322                         p->avl_bf = avl_bfs[nside];
 323                         shorter = 0;
 324
 325                 } else if ( p->avl_bf == side_bf ) {
 326                 /* case 2: taller subtree shortened, height reduced */
 327                         p->avl_bf = EH;
 328                 } else {
 329                 /* case 3: shorter subtree shortened */
 330                         if ( depth )
 331                                 top = pptr[depth-1]; /* p->parent; */
 332                         else
 333                                 top = NULL;
 334                         /* set <q> to the taller of the two subtrees of <p> */
 335                         q = p->avl_link[nside];
 336                         if ( q->avl_bf == EH ) {
 337                                 /* case 3a: height unchanged, single rotate */
 338                                 if ( q->avl_bits[side] == AVL_THREAD ) {
 339                                         q->avl_bits[side] = AVL_CHILD;
 340                                         p->avl_bits[nside] = AVL_THREAD;
 341                                 } else {
 342                                         p->avl_link[nside] = q->avl_link[side];
 343                                         q->avl_link[side] = p;
 344                                 }
 345                                 shorter = 0;
 346                                 q->avl_bf = side_bf;
 347                                 p->avl_bf = (- side_bf);
 348
 349                         } else if ( q->avl_bf == p->avl_bf ) {
 350                                 /* case 3b: height reduced, single rotate */
 351                                 if ( q->avl_bits[side] == AVL_THREAD ) {
 352                                         q->avl_bits[side] = AVL_CHILD;
 353                                         p->avl_bits[nside] = AVL_THREAD;
 354                                 } else {
 355                                         p->avl_link[nside] = q->avl_link[side];
 356                                         q->avl_link[side] = p;
 357                                 }
 358                                 shorter = 1;
 359                                 q->avl_bf = EH;
 360                                 p->avl_bf = EH;
 361
 362                         } else {
 363                                 /* case 3c: height reduced, balance factors opposite */
 364                                 r = q->avl_link[side];
 365                                 if ( r->avl_bits[nside] == AVL_THREAD ) {
 366                                         r->avl_bits[nside] = AVL_CHILD;
 367                                         q->avl_bits[side] = AVL_THREAD;
 368                                 } else {
 369                                         q->avl_link[side] = r->avl_link[nside];
 370                                         r->avl_link[nside] = q;
 371                                 }
 372
 373                                 if ( r->avl_bits[side] == AVL_THREAD ) {
 374                                         r->avl_bits[side] = AVL_CHILD;
 375                                         p->avl_bits[nside] = AVL_THREAD;
 376                                         p->avl_link[nside] = r;
 377                                 } else {
 378                                         p->avl_link[nside] = r->avl_link[side];
 379                                         r->avl_link[side] = p;
 380                                 }
 381
 382                                 if ( r->avl_bf == side_bf ) {
 383                                         q->avl_bf = (- side_bf);
 384                                         p->avl_bf = EH;
 385                                 } else if ( r->avl_bf == (- side_bf)) {
 386                                         q->avl_bf = EH;
 387                                         p->avl_bf = side_bf;
 388                                 } else {
 389                                         q->avl_bf = EH;
 390                                         p->avl_bf = EH;
 391                                 }
 392                                 r->avl_bf = EH;
 393                                 q = r;
 394                         }
 395                         /* a rotation has caused <q> (or <r> in case 3c) to become
 396                          * the root.  let <p>'s former parent know this.
 397                          */
 398                         if ( top == NULL ) {
 399                                 *root = q;
 400                         } else if (top->avl_link[0] == p) {
 401                                 top->avl_link[0] = q;
 402                         } else {
 403                                 top->avl_link[1] = q;
 404                         }
 405                         /* end case 3 */
 406                         p = q;
 407                 }
 408                 if ( !depth )
 409                         break;
 410                 depth--;
 411         } /* end while(shorter) */
 412
 413         return data;
 414 }
 415
 416 /*
 417  * tavl_free -- traverse avltree root, freeing the memory it is using.
 418  * the dfree() is called to free the data portion of each node.  The
 419  * number of items actually freed is returned.
 420  */
 421
 422 int
 423 tavl_free( Avlnode *root, AVL_FREE dfree )
 424 {
 425         int     nleft, nright;
 426
 427         if ( root == 0 )
 428                 return( 0 );
 429
 430         nleft = tavl_free( avl_lchild( root ), dfree );
 431
 432         nright = tavl_free( avl_rchild( root ), dfree );
 433
 434         if ( dfree )
 435                 (*dfree)( root->avl_data );
 436         ber_memfree( root );
 437
 438         return( nleft + nright + 1 );
 439 }
 440
 441 /*
 442  * tavl_find -- search avltree root for a node with data data.  the function
 443  * cmp is used to compare things.  it is called with data as its first arg
 444  * and the current node data as its second.  it should return 0 if they match,
 445  * < 0 if arg1 is less than arg2 and > 0 if arg1 is greater than arg2.
 446  */
 447
 448 /*
 449  * tavl_find2 - returns Avlnode instead of data pointer.
 450  * tavl_find3 - as above, but returns Avlnode even if no match is found.
 451  *                              also return the last comparison result in ret.
 452  */
 453 Avlnode *
 454 tavl_find3( Avlnode *root, const void *data, AVL_CMP fcmp, int *ret )
 455 {
 456         int     cmp, dir;
 457         Avlnode *prev;
 458
 459         while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
 460                 prev = root;
 461                 dir = cmp > 0;
 462                 root = avl_child( root, dir );
 463         }
 464         *ret = cmp;
 465         return root ? root : prev;
 466 }
 467
 468 Avlnode *
 469 tavl_find2( Avlnode *root, const void *data, AVL_CMP fcmp )
 470 {
 471         int     cmp;
 472
 473         while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
 474                 cmp = cmp > 0;
 475                 root = avl_child( root, cmp );
 476         }
 477         return root;
 478 }
 479
 480 void*
 481 tavl_find( Avlnode *root, const void* data, AVL_CMP fcmp )
 482 {
 483         int     cmp;
 484
 485         while ( root != 0 && (cmp = (*fcmp)( data, root->avl_data )) != 0 ) {
 486                 cmp = cmp > 0;
 487                 root = avl_child( root, cmp );
 488         }
 489
 490         return( root ? root->avl_data : 0 );
 491 }
 492
 493 /* Return the leftmost or rightmost node in the tree */
 494 Avlnode *
 495 tavl_end( Avlnode *root, int dir )
 496 {
 497         if ( root ) {
 498                 while ( root->avl_bits[dir] == AVL_CHILD )
 499                         root = root->avl_link[dir];
 500         }
 501         return root;
 502 }
 503
 504 /* Return the next node in the given direction */
 505 Avlnode *
 506 tavl_next( Avlnode *root, int dir )
 507 {
 508         if ( root ) {
 509                 int c = root->avl_bits[dir];
 510
 511                 root = root->avl_link[dir];
 512                 if ( c == AVL_CHILD ) {
 513                         dir ^= 1;
 514                         while ( root->avl_bits[dir] == AVL_CHILD )
 515                                 root = root->avl_link[dir];
 516                 }
 517         }
 518         return root;
 519 }