src/lib/rbtree.c

   1 /*
   2  * rbtree.c     Red-black balanced binary trees.
   3  *
   4  * Version:     $Id$
   5  *
   6  *   This library is free software; you can redistribute it and/or
   7  *   modify it under the terms of the GNU Lesser General Public
   8  *   License as published by the Free Software Foundation; either
   9  *   version 2.1 of the License, or (at your option) any later version.
  10  *
  11  *   This library is distributed in the hope that it will be useful,
  12  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14  *   Lesser General Public License for more details.
  15  *
  16  *   You should have received a copy of the GNU Lesser General Public
  17  *   License along with this library; if not, write to the Free Software
  18  *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  19  *
  20  *  Copyright 2004,2006  The FreeRADIUS server project
  21  */
  22
  23 #include <freeradius-devel/ident.h>
  24 RCSID("$Id$")
  25
  26 #include <freeradius-devel/libradius.h>
  27
  28 /* red-black tree description */
  29 typedef enum { Black, Red } NodeColor;
  30
  31 struct rbnode_t {
  32     rbnode_t    *Left;          /* left child */
  33     rbnode_t    *Right;         /* right child */
  34     rbnode_t    *Parent;        /* parent */
  35     NodeColor   Color;          /* node color (black, red) */
  36     void        *Data;          /* data stored in node */
  37 };
  38
  39 #define NIL &Sentinel           /* all leafs are sentinels */
  40 static rbnode_t Sentinel = { NIL, NIL, NULL, Black, NULL};
  41
  42 struct rbtree_t {
  43 #ifndef NDEBUG
  44         uint32_t magic;
  45 #endif
  46         rbnode_t *Root;
  47         int     num_elements;
  48         int (*Compare)(const void *, const void *);
  49         int replace_flag;
  50         void (*freeNode)(void *);
  51 };
  52 #define RBTREE_MAGIC (0x5ad09c42)
  53
  54 /*
  55  *      Walks the tree to delete all nodes.
  56  *      Does NOT re-balance it!
  57  */
  58 static void FreeWalker(rbtree_t *tree, rbnode_t *X)
  59 {
  60         if (X->Left != NIL) FreeWalker(tree, X->Left);
  61         if (X->Right != NIL) FreeWalker(tree, X->Right);
  62
  63         if (tree->freeNode) tree->freeNode(X->Data);
  64         free(X);
  65 }
  66
  67 void rbtree_free(rbtree_t *tree)
  68 {
  69         if (!tree) return;
  70
  71         /*
  72          *      Walk the tree, deleting the nodes...
  73          */
  74         if (tree->Root != NIL) FreeWalker(tree, tree->Root);
  75
  76 #ifndef NDEBUG
  77         tree->magic = 0;
  78 #endif
  79         tree->Root = NULL;
  80         free(tree);
  81 }
  82
  83 /*
  84  *      Create a new red-black tree.
  85  */
  86 rbtree_t *rbtree_create(int (*Compare)(const void *, const void *),
  87                         void (*freeNode)(void *),
  88                         int replace_flag)
  89 {
  90         rbtree_t        *tree;
  91
  92         if (!Compare) return NULL;
  93
  94         tree = malloc(sizeof(*tree));
  95         if (!tree) return NULL;
  96
  97         memset(tree, 0, sizeof(*tree));
  98 #ifndef NDEBUG
  99         tree->magic = RBTREE_MAGIC;
 100 #endif
 101         tree->Root = NIL;
 102         tree->Compare = Compare;
 103         tree->replace_flag = replace_flag;
 104         tree->freeNode = freeNode;
 105
 106         return tree;
 107 }
 108
 109
 110 static void RotateLeft(rbtree_t *tree, rbnode_t *X)
 111 {
 112         /**************************
 113          *  rotate Node X to left *
 114          **************************/
 115
 116         rbnode_t *Y = X->Right;
 117
 118         /* establish X->Right link */
 119         X->Right = Y->Left;
 120         if (Y->Left != NIL) Y->Left->Parent = X;
 121
 122         /* establish Y->Parent link */
 123         if (Y != NIL) Y->Parent = X->Parent;
 124         if (X->Parent) {
 125                 if (X == X->Parent->Left)
 126                         X->Parent->Left = Y;
 127                 else
 128                         X->Parent->Right = Y;
 129         } else {
 130                 tree->Root = Y;
 131         }
 132
 133         /* link X and Y */
 134         Y->Left = X;
 135         if (X != NIL) X->Parent = Y;
 136 }
 137
 138 static void RotateRight(rbtree_t *tree, rbnode_t *X)
 139 {
 140         /****************************
 141          *  rotate Node X to right  *
 142          ****************************/
 143
 144         rbnode_t *Y = X->Left;
 145
 146         /* establish X->Left link */
 147         X->Left = Y->Right;
 148         if (Y->Right != NIL) Y->Right->Parent = X;
 149
 150         /* establish Y->Parent link */
 151         if (Y != NIL) Y->Parent = X->Parent;
 152         if (X->Parent) {
 153                 if (X == X->Parent->Right)
 154                         X->Parent->Right = Y;
 155                 else
 156                         X->Parent->Left = Y;
 157         } else {
 158                 tree->Root = Y;
 159         }
 160
 161         /* link X and Y */
 162         Y->Right = X;
 163         if (X != NIL) X->Parent = Y;
 164 }
 165
 166 static void InsertFixup(rbtree_t *tree, rbnode_t *X)
 167 {
 168         /*************************************
 169          *  maintain red-black tree balance  *
 170          *  after inserting node X           *
 171          *************************************/
 172
 173         /* check red-black properties */
 174         while (X != tree->Root && X->Parent->Color == Red) {
 175                 /* we have a violation */
 176                 if (X->Parent == X->Parent->Parent->Left) {
 177                         rbnode_t *Y = X->Parent->Parent->Right;
 178                         if (Y->Color == Red) {
 179
 180                                 /* uncle is red */
 181                                 X->Parent->Color = Black;
 182                                 Y->Color = Black;
 183                                 X->Parent->Parent->Color = Red;
 184                                 X = X->Parent->Parent;
 185                         } else {
 186
 187                                 /* uncle is black */
 188                                 if (X == X->Parent->Right) {
 189                                         /* make X a left child */
 190                                         X = X->Parent;
 191                                         RotateLeft(tree, X);
 192                                 }
 193
 194                                 /* recolor and rotate */
 195                                 X->Parent->Color = Black;
 196                                 X->Parent->Parent->Color = Red;
 197                                 RotateRight(tree, X->Parent->Parent);
 198                         }
 199                 } else {
 200
 201                         /* mirror image of above code */
 202                         rbnode_t *Y = X->Parent->Parent->Left;
 203                         if (Y->Color == Red) {
 204
 205                                 /* uncle is red */
 206                                 X->Parent->Color = Black;
 207                                 Y->Color = Black;
 208                                 X->Parent->Parent->Color = Red;
 209                                 X = X->Parent->Parent;
 210                         } else {
 211
 212                                 /* uncle is black */
 213                                 if (X == X->Parent->Left) {
 214                                         X = X->Parent;
 215                                         RotateRight(tree, X);
 216                                 }
 217                                 X->Parent->Color = Black;
 218                                 X->Parent->Parent->Color = Red;
 219                                 RotateLeft(tree, X->Parent->Parent);
 220                         }
 221                 }
 222         }
 223
 224         tree->Root->Color = Black;
 225 }
 226
 227
 228 /*
 229  *      Insert an element into the tree.
 230  */
 231 int rbtree_insert(rbtree_t *tree, void *Data)
 232 {
 233         rbnode_t *Current, *Parent, *X;
 234
 235         /***********************************************
 236          *  allocate node for Data and insert in tree  *
 237          ***********************************************/
 238
 239         /* find where node belongs */
 240         Current = tree->Root;
 241         Parent = NULL;
 242         while (Current != NIL) {
 243                 int result;
 244
 245                 /*
 246                  *      See if two entries are identical.
 247                  */
 248                 result = tree->Compare(Data, Current->Data);
 249                 if (result == 0) {
 250                         /*
 251                          *      Don't replace the entry.
 252                          */
 253                         if (tree->replace_flag == 0) {
 254                                 return 0;
 255                         }
 256
 257                         /*
 258                          *      Do replace the entry.
 259                          */
 260                         if (tree->freeNode) tree->freeNode(Current->Data);
 261                         Current->Data = Data;
 262                         return 1;
 263                 }
 264
 265                 Parent = Current;
 266                 Current = (result < 0) ? Current->Left : Current->Right;
 267         }
 268
 269         /* setup new node */
 270         if ((X = malloc (sizeof(*X))) == NULL) {
 271                 exit(1);        /* FIXME! */
 272         }
 273
 274         X->Data = Data;
 275         X->Parent = Parent;
 276         X->Left = NIL;
 277         X->Right = NIL;
 278         X->Color = Red;
 279
 280         /* insert node in tree */
 281         if (Parent) {
 282                 if (tree->Compare(Data, Parent->Data) <= 0)
 283                         Parent->Left = X;
 284                 else
 285                         Parent->Right = X;
 286         } else {
 287                 tree->Root = X;
 288         }
 289
 290         InsertFixup(tree, X);
 291
 292         tree->num_elements++;
 293
 294         return 1;
 295 }
 296
 297 static void DeleteFixup(rbtree_t *tree, rbnode_t *X, rbnode_t *Parent)
 298 {
 299         /*************************************
 300          *  maintain red-black tree balance  *
 301          *  after deleting node X            *
 302          *************************************/
 303
 304         while (X != tree->Root && X->Color == Black) {
 305                 if (X == Parent->Left) {
 306                         rbnode_t *W = Parent->Right;
 307                         if (W->Color == Red) {
 308                                 W->Color = Black;
 309                                 Parent->Color = Red; /* Parent != NIL? */
 310                                 RotateLeft(tree, Parent);
 311                                 W = Parent->Right;
 312                         }
 313                         if (W->Left->Color == Black && W->Right->Color == Black) {
 314                                 if (W != NIL) W->Color = Red;
 315                                 X = Parent;
 316                                 Parent = X->Parent;
 317                         } else {
 318                                 if (W->Right->Color == Black) {
 319                                         if (W->Left != NIL) W->Left->Color = Black;
 320                                         W->Color = Red;
 321                                         RotateRight(tree, W);
 322                                         W = Parent->Right;
 323                                 }
 324                                 W->Color = Parent->Color;
 325                                 if (Parent != NIL) Parent->Color = Black;
 326                                 if (W->Right->Color != Black) {
 327                                         W->Right->Color = Black;
 328                                 }
 329                                 RotateLeft(tree, Parent);
 330                                 X = tree->Root;
 331                         }
 332                 } else {
 333                         rbnode_t *W = Parent->Left;
 334                         if (W->Color == Red) {
 335                                 W->Color = Black;
 336                                 Parent->Color = Red; /* Parent != NIL? */
 337                                 RotateRight(tree, Parent);
 338                                 W = Parent->Left;
 339                         }
 340                         if (W->Right->Color == Black && W->Left->Color == Black) {
 341                                 if (W != NIL) W->Color = Red;
 342                                 X = Parent;
 343                                 Parent = X->Parent;
 344                         } else {
 345                                 if (W->Left->Color == Black) {
 346                                         if (W->Right != NIL) W->Right->Color = Black;
 347                                         W->Color = Red;
 348                                         RotateLeft(tree, W);
 349                                         W = Parent->Left;
 350                                 }
 351                                 W->Color = Parent->Color;
 352                                 if (Parent != NIL) Parent->Color = Black;
 353                                 if (W->Left->Color != Black) {
 354                                         W->Left->Color = Black;
 355                                 }
 356                                 RotateRight(tree, Parent);
 357                                 X = tree->Root;
 358                         }
 359                 }
 360         }
 361         X->Color = Black;
 362 }
 363
 364 /*
 365  *      Delete an element from the tree.
 366  */
 367 void rbtree_delete(rbtree_t *tree, rbnode_t *Z)
 368 {
 369         rbnode_t *X, *Y;
 370         rbnode_t *Parent;
 371
 372         /*****************************
 373          *  delete node Z from tree  *
 374          *****************************/
 375
 376         if (!Z || Z == NIL) return;
 377
 378         if (Z->Left == NIL || Z->Right == NIL) {
 379                 /* Y has a NIL node as a child */
 380                 Y = Z;
 381         } else {
 382                 /* find tree successor with a NIL node as a child */
 383                 Y = Z->Right;
 384                 while (Y->Left != NIL) Y = Y->Left;
 385         }
 386
 387         /* X is Y's only child */
 388         if (Y->Left != NIL)
 389                 X = Y->Left;
 390         else
 391                 X = Y->Right;   /* may be NIL! */
 392
 393         /* remove Y from the parent chain */
 394         Parent = Y->Parent;
 395         if (X != NIL) X->Parent = Parent;
 396
 397         if (Parent)
 398                 if (Y == Parent->Left)
 399                         Parent->Left = X;
 400                 else
 401                         Parent->Right = X;
 402         else
 403                 tree->Root = X;
 404
 405         if (Y != Z) {
 406                 /*
 407                  *      Move the child's data to here, and then
 408                  *      re-balance the tree.
 409                  */
 410                 if (tree->freeNode) tree->freeNode(Z->Data);
 411                 Z->Data = Y->Data;
 412                 Y->Data = NULL;
 413         } else if (tree->freeNode) {
 414                 tree->freeNode(Z->Data);
 415         }
 416
 417         if (Y->Color == Black && X != NIL)
 418                 DeleteFixup(tree, X, Parent);
 419
 420         free(Y);
 421
 422         tree->num_elements--;
 423 }
 424
 425 /*
 426  *      Delete a node from the tree, based on given data, which MUST
 427  *      have come from rbtree_finddata().
 428  */
 429 int rbtree_deletebydata(rbtree_t *tree, const void *data)
 430 {
 431         rbnode_t *node = rbtree_find(tree, data);
 432
 433         if (!node) return 0;    /* false */
 434
 435         rbtree_delete(tree, node);
 436
 437         return 1;
 438 }
 439
 440
 441 /*
 442  *      Find an element in the tree, returning the data, not the node.
 443  */
 444 rbnode_t *rbtree_find(rbtree_t *tree, const void *Data)
 445 {
 446         /*******************************
 447          *  find node containing Data  *
 448          *******************************/
 449
 450         rbnode_t *Current = tree->Root;
 451
 452         while (Current != NIL) {
 453                 int result = tree->Compare(Data, Current->Data);
 454
 455                 if (result == 0) {
 456                         return Current;
 457                 } else {
 458                         Current = (result < 0) ?
 459                                 Current->Left : Current->Right;
 460                 }
 461         }
 462         return NULL;
 463 }
 464
 465 /*
 466  *      Find the user data.
 467  */
 468 void *rbtree_finddata(rbtree_t *tree, const void *Data)
 469 {
 470         rbnode_t *X;
 471
 472         X = rbtree_find(tree, Data);
 473         if (!X) return NULL;
 474
 475         return X->Data;
 476 }
 477
 478 /*
 479  *      Walk the tree, Pre-order
 480  *
 481  *      We call ourselves recursively for each function, but that's OK,
 482  *      as the stack is only log(N) deep, which is ~12 entries deep.
 483  */
 484 static int WalkNodePreOrder(rbnode_t *X,
 485                             int (*callback)(void *, void *), void *context)
 486 {
 487         int rcode;
 488
 489         rcode = callback(context, X->Data);
 490         if (rcode != 0) return rcode;
 491
 492         if (X->Left != NIL) {
 493                 rcode = WalkNodePreOrder(X->Left, callback, context);
 494                 if (rcode != 0) return rcode;
 495         }
 496
 497         if (X->Right != NIL) {
 498                 rcode = WalkNodePreOrder(X->Right, callback, context);
 499                 if (rcode != 0) return rcode;
 500         }
 501
 502         return 0;               /* we know everything returned zero */
 503 }
 504
 505 /*
 506  *      Inorder
 507  */
 508 static int WalkNodeInOrder(rbnode_t *X,
 509                            int (*callback)(void *, void *), void *context)
 510 {
 511         int rcode;
 512
 513         if (X->Left != NIL) {
 514                 rcode = WalkNodeInOrder(X->Left, callback, context);
 515                 if (rcode != 0) return rcode;
 516         }
 517
 518         rcode = callback(context, X->Data);
 519         if (rcode != 0) return rcode;
 520
 521         if (X->Right != NIL) {
 522                 rcode = WalkNodeInOrder(X->Right, callback, context);
 523                 if (rcode != 0) return rcode;
 524         }
 525
 526         return 0;               /* we know everything returned zero */
 527 }
 528
 529
 530 /*
 531  *      PostOrder
 532  */
 533 static int WalkNodePostOrder(rbnode_t *X,
 534                              int (*callback)(void *, void*), void *context)
 535 {
 536         int rcode;
 537
 538         if (X->Left != NIL) {
 539                 rcode = WalkNodeInOrder(X->Left, callback, context);
 540                 if (rcode != 0) return rcode;
 541         }
 542
 543         if (X->Right != NIL) {
 544                 rcode = WalkNodeInOrder(X->Right, callback, context);
 545                 if (rcode != 0) return rcode;
 546         }
 547
 548         rcode = callback(context, X->Data);
 549         if (rcode != 0) return rcode;
 550
 551         return 0;               /* we know everything returned zero */
 552 }
 553
 554 /*
 555  *      Walk the entire tree.  The callback function CANNOT modify
 556  *      the tree.
 557  *
 558  *      The callback function should return 0 to continue walking.
 559  *      Any other value stops the walk, and is returned.
 560  */
 561 int rbtree_walk(rbtree_t *tree, RBTREE_ORDER order,
 562                 int (*callback)(void *, void *), void *context)
 563 {
 564         switch (order) {
 565         case PreOrder:
 566                 return WalkNodePreOrder(tree->Root, callback, context);
 567         case InOrder:
 568                 return WalkNodeInOrder(tree->Root, callback, context);
 569         case PostOrder:
 570                 return WalkNodePostOrder(tree->Root, callback, context);
 571
 572         default:
 573                 break;
 574         }
 575
 576         return -1;
 577 }
 578
 579 int rbtree_num_elements(rbtree_t *tree)
 580 {
 581         if (!tree) return 0;
 582
 583         return tree->num_elements;
 584 }
 585
 586
 587 /*
 588  *      Given a Node, return the data.
 589  */
 590 void *rbtree_node2data(rbtree_t *tree, rbnode_t *node)
 591 {
 592         tree = tree;            /* -Wunused */
 593
 594         if (!node) return NULL;
 595
 596         return node->Data;
 597 }