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 rbnode_t *rbtree_insertnode(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 NULL;
 255                         }
 256
 257                         /*
 258                          *      Do replace the entry.
 259                          */
 260                         if (tree->freeNode) tree->freeNode(Current->Data);
 261                         Current->Data = Data;
 262                         return Current;
 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 X;
 295 }
 296
 297 int rbtree_insert(rbtree_t *tree, void *Data)
 298 {
 299         if (rbtree_insertnode(tree, Data)) return 1;
 300         return 0;
 301 }
 302
 303 static void DeleteFixup(rbtree_t *tree, rbnode_t *X, rbnode_t *Parent)
 304 {
 305         /*************************************
 306          *  maintain red-black tree balance  *
 307          *  after deleting node X            *
 308          *************************************/
 309
 310         while (X != tree->Root && X->Color == Black) {
 311                 if (X == Parent->Left) {
 312                         rbnode_t *W = Parent->Right;
 313                         if (W->Color == Red) {
 314                                 W->Color = Black;
 315                                 Parent->Color = Red; /* Parent != NIL? */
 316                                 RotateLeft(tree, Parent);
 317                                 W = Parent->Right;
 318                         }
 319                         if (W->Left->Color == Black && W->Right->Color == Black) {
 320                                 if (W != NIL) W->Color = Red;
 321                                 X = Parent;
 322                                 Parent = X->Parent;
 323                         } else {
 324                                 if (W->Right->Color == Black) {
 325                                         if (W->Left != NIL) W->Left->Color = Black;
 326                                         W->Color = Red;
 327                                         RotateRight(tree, W);
 328                                         W = Parent->Right;
 329                                 }
 330                                 W->Color = Parent->Color;
 331                                 if (Parent != NIL) Parent->Color = Black;
 332                                 if (W->Right->Color != Black) {
 333                                         W->Right->Color = Black;
 334                                 }
 335                                 RotateLeft(tree, Parent);
 336                                 X = tree->Root;
 337                         }
 338                 } else {
 339                         rbnode_t *W = Parent->Left;
 340                         if (W->Color == Red) {
 341                                 W->Color = Black;
 342                                 Parent->Color = Red; /* Parent != NIL? */
 343                                 RotateRight(tree, Parent);
 344                                 W = Parent->Left;
 345                         }
 346                         if (W->Right->Color == Black && W->Left->Color == Black) {
 347                                 if (W != NIL) W->Color = Red;
 348                                 X = Parent;
 349                                 Parent = X->Parent;
 350                         } else {
 351                                 if (W->Left->Color == Black) {
 352                                         if (W->Right != NIL) W->Right->Color = Black;
 353                                         W->Color = Red;
 354                                         RotateLeft(tree, W);
 355                                         W = Parent->Left;
 356                                 }
 357                                 W->Color = Parent->Color;
 358                                 if (Parent != NIL) Parent->Color = Black;
 359                                 if (W->Left->Color != Black) {
 360                                         W->Left->Color = Black;
 361                                 }
 362                                 RotateRight(tree, Parent);
 363                                 X = tree->Root;
 364                         }
 365                 }
 366         }
 367         X->Color = Black;
 368 }
 369
 370 /*
 371  *      Delete an element from the tree.
 372  */
 373 void rbtree_delete(rbtree_t *tree, rbnode_t *Z)
 374 {
 375         int fixup = 0;
 376         rbnode_t *X, *Y;
 377         rbnode_t *Parent;
 378
 379         /*****************************
 380          *  delete node Z from tree  *
 381          *****************************/
 382
 383         if (!Z || Z == NIL) return;
 384
 385         if (Z->Left == NIL || Z->Right == NIL) {
 386                 /* Y has a NIL node as a child */
 387                 Y = Z;
 388         } else {
 389                 /* find tree successor with a NIL node as a child */
 390                 Y = Z->Right;
 391                 while (Y->Left != NIL) Y = Y->Left;
 392         }
 393
 394         /* X is Y's only child */
 395         if (Y->Left != NIL)
 396                 X = Y->Left;
 397         else
 398                 X = Y->Right;   /* may be NIL! */
 399
 400         /* remove Y from the parent chain */
 401         Parent = Y->Parent;
 402         if (X != NIL) X->Parent = Parent;
 403
 404         if (Parent)
 405                 if (Y == Parent->Left)
 406                         Parent->Left = X;
 407                 else
 408                         Parent->Right = X;
 409         else
 410                 tree->Root = X;
 411
 412         if (Y != Z) {
 413                 if (tree->freeNode) tree->freeNode(Z->Data);
 414                 Z->Data = Y->Data;
 415                 Y->Data = NULL;
 416
 417                 if (Y->Color == Black && X != NIL)
 418                         DeleteFixup(tree, X, Parent);
 419
 420                 /*
 421                  *      The user structure in Y->Data MAY include a
 422                  *      pointer to Y.  In that case, we CANNOT delete
 423                  *      Y.  Instead, we copy Z (which is now in the
 424                  *      tree) to Y, and fix up the parent/child
 425                  *      pointers.
 426                  */
 427                 memcpy(Y, Z, sizeof(*Y));
 428
 429                 if (!Y->Parent) {
 430                         tree->Root = Y;
 431                 } else {
 432                         if (Y->Parent->Left == Z) Y->Parent->Left = Y;
 433                         if (Y->Parent->Right == Z) Y->Parent->Right = Y;
 434                 }
 435                 if (Y->Left->Parent == Z) Y->Left->Parent = Y;
 436                 if (Y->Right->Parent == Z) Y->Right->Parent = Y;
 437
 438                 free(Z);
 439
 440         } else {
 441                 if (tree->freeNode) tree->freeNode(Y->Data);
 442
 443                 if (Y->Color == Black && X != NIL)
 444                         DeleteFixup(tree, X, Parent);
 445
 446                 free(Y);
 447         }
 448
 449         tree->num_elements--;
 450 }
 451
 452 /*
 453  *      Delete a node from the tree, based on given data, which MUST
 454  *      have come from rbtree_finddata().
 455  */
 456 int rbtree_deletebydata(rbtree_t *tree, const void *data)
 457 {
 458         rbnode_t *node = rbtree_find(tree, data);
 459
 460         if (!node) return 0;    /* false */
 461
 462         rbtree_delete(tree, node);
 463
 464         return 1;
 465 }
 466
 467
 468 /*
 469  *      Find an element in the tree, returning the data, not the node.
 470  */
 471 rbnode_t *rbtree_find(rbtree_t *tree, const void *Data)
 472 {
 473         /*******************************
 474          *  find node containing Data  *
 475          *******************************/
 476
 477         rbnode_t *Current = tree->Root;
 478
 479         while (Current != NIL) {
 480                 int result = tree->Compare(Data, Current->Data);
 481
 482                 if (result == 0) {
 483                         return Current;
 484                 } else {
 485                         Current = (result < 0) ?
 486                                 Current->Left : Current->Right;
 487                 }
 488         }
 489         return NULL;
 490 }
 491
 492 /*
 493  *      Find the user data.
 494  */
 495 void *rbtree_finddata(rbtree_t *tree, const void *Data)
 496 {
 497         rbnode_t *X;
 498
 499         X = rbtree_find(tree, Data);
 500         if (!X) return NULL;
 501
 502         return X->Data;
 503 }
 504
 505 /*
 506  *      Walk the tree, Pre-order
 507  *
 508  *      We call ourselves recursively for each function, but that's OK,
 509  *      as the stack is only log(N) deep, which is ~12 entries deep.
 510  */
 511 static int WalkNodePreOrder(rbnode_t *X,
 512                             int (*callback)(void *, void *), void *context)
 513 {
 514         int rcode;
 515
 516         rcode = callback(context, X->Data);
 517         if (rcode != 0) return rcode;
 518
 519         if (X->Left != NIL) {
 520                 rcode = WalkNodePreOrder(X->Left, callback, context);
 521                 if (rcode != 0) return rcode;
 522         }
 523
 524         if (X->Right != NIL) {
 525                 rcode = WalkNodePreOrder(X->Right, callback, context);
 526                 if (rcode != 0) return rcode;
 527         }
 528
 529         return 0;               /* we know everything returned zero */
 530 }
 531
 532 /*
 533  *      Inorder
 534  */
 535 static int WalkNodeInOrder(rbnode_t *X,
 536                            int (*callback)(void *, void *), void *context)
 537 {
 538         int rcode;
 539
 540         if (X->Left != NIL) {
 541                 rcode = WalkNodeInOrder(X->Left, callback, context);
 542                 if (rcode != 0) return rcode;
 543         }
 544
 545         rcode = callback(context, X->Data);
 546         if (rcode != 0) return rcode;
 547
 548         if (X->Right != NIL) {
 549                 rcode = WalkNodeInOrder(X->Right, callback, context);
 550                 if (rcode != 0) return rcode;
 551         }
 552
 553         return 0;               /* we know everything returned zero */
 554 }
 555
 556
 557 /*
 558  *      PostOrder
 559  */
 560 static int WalkNodePostOrder(rbnode_t *X,
 561                              int (*callback)(void *, void*), void *context)
 562 {
 563         int rcode;
 564
 565         if (X->Left != NIL) {
 566                 rcode = WalkNodeInOrder(X->Left, callback, context);
 567                 if (rcode != 0) return rcode;
 568         }
 569
 570         if (X->Right != NIL) {
 571                 rcode = WalkNodeInOrder(X->Right, callback, context);
 572                 if (rcode != 0) return rcode;
 573         }
 574
 575         rcode = callback(context, X->Data);
 576         if (rcode != 0) return rcode;
 577
 578         return 0;               /* we know everything returned zero */
 579 }
 580
 581 /*
 582  *      Walk the entire tree.  The callback function CANNOT modify
 583  *      the tree.
 584  *
 585  *      The callback function should return 0 to continue walking.
 586  *      Any other value stops the walk, and is returned.
 587  */
 588 int rbtree_walk(rbtree_t *tree, RBTREE_ORDER order,
 589                 int (*callback)(void *, void *), void *context)
 590 {
 591         switch (order) {
 592         case PreOrder:
 593                 return WalkNodePreOrder(tree->Root, callback, context);
 594         case InOrder:
 595                 return WalkNodeInOrder(tree->Root, callback, context);
 596         case PostOrder:
 597                 return WalkNodePostOrder(tree->Root, callback, context);
 598
 599         default:
 600                 break;
 601         }
 602
 603         return -1;
 604 }
 605
 606 int rbtree_num_elements(rbtree_t *tree)
 607 {
 608         if (!tree) return 0;
 609
 610         return tree->num_elements;
 611 }
 612
 613
 614 /*
 615  *      Given a Node, return the data.
 616  */
 617 void *rbtree_node2data(rbtree_t *tree, rbnode_t *node)
 618 {
 619         tree = tree;            /* -Wunused */
 620
 621         if (!node) return NULL;
 622
 623         return node->Data;
 624 }
 625
 626 /*
 627  *      Return left-most child.
 628  */
 629 void *rbtree_min(rbtree_t *tree)
 630 {
 631         rbnode_t *Current;
 632
 633         if (!tree || !tree->Root) return NULL;
 634
 635         Current = tree->Root;
 636         while (Current->Left != NIL) Current = Current->Left;
 637
 638         return Current->Data;
 639 }