lib/rbtree.c

   1 /*
   2   Red Black Trees
   3   (C) 1999  Andrea Arcangeli <andrea@suse.de>
   4   (C) 2002  David Woodhouse <dwmw2@infradead.org>
   5
   6   This program is free software; you can redistribute it and/or modify
   7   it under the terms of the GNU General Public License as published by
   8   the Free Software Foundation; either version 2 of the License, or
   9   (at your option) any later version.
  10
  11   This program 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
  14   GNU General Public License for more details.
  15
  16   You should have received a copy of the GNU General Public License
  17   along with this program; if not, write to the Free Software
  18   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19
  20   linux/lib/rbtree.c
  21 */
  22
  23 #include <linux/rbtree.h>
  24 #include <linux/export.h>
  25
  26 #define RB_RED          0
  27 #define RB_BLACK        1
  28
  29 #define rb_color(r)   ((r)->__rb_parent_color & 1)
  30 #define rb_is_red(r)   (!rb_color(r))
  31 #define rb_is_black(r) rb_color(r)
  32 #define rb_set_red(r)  do { (r)->__rb_parent_color &= ~1; } while (0)
  33 #define rb_set_black(r)  do { (r)->__rb_parent_color |= 1; } while (0)
  34
  35 static inline void rb_set_parent(struct rb_node *rb, struct rb_node *p)
  36 {
  37         rb->__rb_parent_color = rb_color(rb) | (unsigned long)p;
  38 }
  39 static inline void rb_set_color(struct rb_node *rb, int color)
  40 {
  41         rb->__rb_parent_color = (rb->__rb_parent_color & ~1) | color;
  42 }
  43
  44 static void __rb_rotate_left(struct rb_node *node, struct rb_root *root)
  45 {
  46         struct rb_node *right = node->rb_right;
  47         struct rb_node *parent = rb_parent(node);
  48
  49         if ((node->rb_right = right->rb_left))
  50                 rb_set_parent(right->rb_left, node);
  51         right->rb_left = node;
  52
  53         rb_set_parent(right, parent);
  54
  55         if (parent)
  56         {
  57                 if (node == parent->rb_left)
  58                         parent->rb_left = right;
  59                 else
  60                         parent->rb_right = right;
  61         }
  62         else
  63                 root->rb_node = right;
  64         rb_set_parent(node, right);
  65 }
  66
  67 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
  68 {
  69         struct rb_node *left = node->rb_left;
  70         struct rb_node *parent = rb_parent(node);
  71
  72         if ((node->rb_left = left->rb_right))
  73                 rb_set_parent(left->rb_right, node);
  74         left->rb_right = node;
  75
  76         rb_set_parent(left, parent);
  77
  78         if (parent)
  79         {
  80                 if (node == parent->rb_right)
  81                         parent->rb_right = left;
  82                 else
  83                         parent->rb_left = left;
  84         }
  85         else
  86                 root->rb_node = left;
  87         rb_set_parent(node, left);
  88 }
  89
  90 void rb_insert_color(struct rb_node *node, struct rb_root *root)
  91 {
  92         struct rb_node *parent, *gparent;
  93
  94         while (true) {
  95                 /*
  96                  * Loop invariant: node is red
  97                  *
  98                  * If there is a black parent, we are done.
  99                  * Otherwise, take some corrective action as we don't
 100                  * want a red root or two consecutive red nodes.
 101                  */
 102                 parent = rb_parent(node);
 103                 if (!parent) {
 104                         rb_set_black(node);
 105                         break;
 106                 } else if (rb_is_black(parent))
 107                         break;
 108
 109                 gparent = rb_parent(parent);
 110
 111                 if (parent == gparent->rb_left)
 112                 {
 113                         {
 114                                 register struct rb_node *uncle = gparent->rb_right;
 115                                 if (uncle && rb_is_red(uncle))
 116                                 {
 117                                         rb_set_black(uncle);
 118                                         rb_set_black(parent);
 119                                         rb_set_red(gparent);
 120                                         node = gparent;
 121                                         continue;
 122                                 }
 123                         }
 124
 125                         if (parent->rb_right == node) {
 126                                 __rb_rotate_left(parent, root);
 127                                 parent = node;
 128                         }
 129
 130                         rb_set_black(parent);
 131                         rb_set_red(gparent);
 132                         __rb_rotate_right(gparent, root);
 133                         break;
 134                 } else {
 135                         {
 136                                 register struct rb_node *uncle = gparent->rb_left;
 137                                 if (uncle && rb_is_red(uncle))
 138                                 {
 139                                         rb_set_black(uncle);
 140                                         rb_set_black(parent);
 141                                         rb_set_red(gparent);
 142                                         node = gparent;
 143                                         continue;
 144                                 }
 145                         }
 146
 147                         if (parent->rb_left == node) {
 148                                 __rb_rotate_right(parent, root);
 149                                 parent = node;
 150                         }
 151
 152                         rb_set_black(parent);
 153                         rb_set_red(gparent);
 154                         __rb_rotate_left(gparent, root);
 155                         break;
 156                 }
 157         }
 158 }
 159 EXPORT_SYMBOL(rb_insert_color);
 160
 161 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 162                              struct rb_root *root)
 163 {
 164         struct rb_node *other;
 165
 166         while ((!node || rb_is_black(node)) && node != root->rb_node)
 167         {
 168                 if (parent->rb_left == node)
 169                 {
 170                         other = parent->rb_right;
 171                         if (rb_is_red(other))
 172                         {
 173                                 rb_set_black(other);
 174                                 rb_set_red(parent);
 175                                 __rb_rotate_left(parent, root);
 176                                 other = parent->rb_right;
 177                         }
 178                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 179                             (!other->rb_right || rb_is_black(other->rb_right)))
 180                         {
 181                                 rb_set_red(other);
 182                                 node = parent;
 183                                 parent = rb_parent(node);
 184                         }
 185                         else
 186                         {
 187                                 if (!other->rb_right || rb_is_black(other->rb_right))
 188                                 {
 189                                         rb_set_black(other->rb_left);
 190                                         rb_set_red(other);
 191                                         __rb_rotate_right(other, root);
 192                                         other = parent->rb_right;
 193                                 }
 194                                 rb_set_color(other, rb_color(parent));
 195                                 rb_set_black(parent);
 196                                 rb_set_black(other->rb_right);
 197                                 __rb_rotate_left(parent, root);
 198                                 node = root->rb_node;
 199                                 break;
 200                         }
 201                 }
 202                 else
 203                 {
 204                         other = parent->rb_left;
 205                         if (rb_is_red(other))
 206                         {
 207                                 rb_set_black(other);
 208                                 rb_set_red(parent);
 209                                 __rb_rotate_right(parent, root);
 210                                 other = parent->rb_left;
 211                         }
 212                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 213                             (!other->rb_right || rb_is_black(other->rb_right)))
 214                         {
 215                                 rb_set_red(other);
 216                                 node = parent;
 217                                 parent = rb_parent(node);
 218                         }
 219                         else
 220                         {
 221                                 if (!other->rb_left || rb_is_black(other->rb_left))
 222                                 {
 223                                         rb_set_black(other->rb_right);
 224                                         rb_set_red(other);
 225                                         __rb_rotate_left(other, root);
 226                                         other = parent->rb_left;
 227                                 }
 228                                 rb_set_color(other, rb_color(parent));
 229                                 rb_set_black(parent);
 230                                 rb_set_black(other->rb_left);
 231                                 __rb_rotate_right(parent, root);
 232                                 node = root->rb_node;
 233                                 break;
 234                         }
 235                 }
 236         }
 237         if (node)
 238                 rb_set_black(node);
 239 }
 240
 241 void rb_erase(struct rb_node *node, struct rb_root *root)
 242 {
 243         struct rb_node *child, *parent;
 244         int color;
 245
 246         if (!node->rb_left)
 247                 child = node->rb_right;
 248         else if (!node->rb_right)
 249                 child = node->rb_left;
 250         else
 251         {
 252                 struct rb_node *old = node, *left;
 253
 254                 node = node->rb_right;
 255                 while ((left = node->rb_left) != NULL)
 256                         node = left;
 257
 258                 if (rb_parent(old)) {
 259                         if (rb_parent(old)->rb_left == old)
 260                                 rb_parent(old)->rb_left = node;
 261                         else
 262                                 rb_parent(old)->rb_right = node;
 263                 } else
 264                         root->rb_node = node;
 265
 266                 child = node->rb_right;
 267                 parent = rb_parent(node);
 268                 color = rb_color(node);
 269
 270                 if (parent == old) {
 271                         parent = node;
 272                 } else {
 273                         if (child)
 274                                 rb_set_parent(child, parent);
 275                         parent->rb_left = child;
 276
 277                         node->rb_right = old->rb_right;
 278                         rb_set_parent(old->rb_right, node);
 279                 }
 280
 281                 node->__rb_parent_color = old->__rb_parent_color;
 282                 node->rb_left = old->rb_left;
 283                 rb_set_parent(old->rb_left, node);
 284
 285                 goto color;
 286         }
 287
 288         parent = rb_parent(node);
 289         color = rb_color(node);
 290
 291         if (child)
 292                 rb_set_parent(child, parent);
 293         if (parent)
 294         {
 295                 if (parent->rb_left == node)
 296                         parent->rb_left = child;
 297                 else
 298                         parent->rb_right = child;
 299         }
 300         else
 301                 root->rb_node = child;
 302
 303  color:
 304         if (color == RB_BLACK)
 305                 __rb_erase_color(child, parent, root);
 306 }
 307 EXPORT_SYMBOL(rb_erase);
 308
 309 static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data)
 310 {
 311         struct rb_node *parent;
 312
 313 up:
 314         func(node, data);
 315         parent = rb_parent(node);
 316         if (!parent)
 317                 return;
 318
 319         if (node == parent->rb_left && parent->rb_right)
 320                 func(parent->rb_right, data);
 321         else if (parent->rb_left)
 322                 func(parent->rb_left, data);
 323
 324         node = parent;
 325         goto up;
 326 }
 327
 328 /*
 329  * after inserting @node into the tree, update the tree to account for
 330  * both the new entry and any damage done by rebalance
 331  */
 332 void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data)
 333 {
 334         if (node->rb_left)
 335                 node = node->rb_left;
 336         else if (node->rb_right)
 337                 node = node->rb_right;
 338
 339         rb_augment_path(node, func, data);
 340 }
 341 EXPORT_SYMBOL(rb_augment_insert);
 342
 343 /*
 344  * before removing the node, find the deepest node on the rebalance path
 345  * that will still be there after @node gets removed
 346  */
 347 struct rb_node *rb_augment_erase_begin(struct rb_node *node)
 348 {
 349         struct rb_node *deepest;
 350
 351         if (!node->rb_right && !node->rb_left)
 352                 deepest = rb_parent(node);
 353         else if (!node->rb_right)
 354                 deepest = node->rb_left;
 355         else if (!node->rb_left)
 356                 deepest = node->rb_right;
 357         else {
 358                 deepest = rb_next(node);
 359                 if (deepest->rb_right)
 360                         deepest = deepest->rb_right;
 361                 else if (rb_parent(deepest) != node)
 362                         deepest = rb_parent(deepest);
 363         }
 364
 365         return deepest;
 366 }
 367 EXPORT_SYMBOL(rb_augment_erase_begin);
 368
 369 /*
 370  * after removal, update the tree to account for the removed entry
 371  * and any rebalance damage.
 372  */
 373 void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data)
 374 {
 375         if (node)
 376                 rb_augment_path(node, func, data);
 377 }
 378 EXPORT_SYMBOL(rb_augment_erase_end);
 379
 380 /*
 381  * This function returns the first node (in sort order) of the tree.
 382  */
 383 struct rb_node *rb_first(const struct rb_root *root)
 384 {
 385         struct rb_node  *n;
 386
 387         n = root->rb_node;
 388         if (!n)
 389                 return NULL;
 390         while (n->rb_left)
 391                 n = n->rb_left;
 392         return n;
 393 }
 394 EXPORT_SYMBOL(rb_first);
 395
 396 struct rb_node *rb_last(const struct rb_root *root)
 397 {
 398         struct rb_node  *n;
 399
 400         n = root->rb_node;
 401         if (!n)
 402                 return NULL;
 403         while (n->rb_right)
 404                 n = n->rb_right;
 405         return n;
 406 }
 407 EXPORT_SYMBOL(rb_last);
 408
 409 struct rb_node *rb_next(const struct rb_node *node)
 410 {
 411         struct rb_node *parent;
 412
 413         if (RB_EMPTY_NODE(node))
 414                 return NULL;
 415
 416         /* If we have a right-hand child, go down and then left as far
 417            as we can. */
 418         if (node->rb_right) {
 419                 node = node->rb_right;
 420                 while (node->rb_left)
 421                         node=node->rb_left;
 422                 return (struct rb_node *)node;
 423         }
 424
 425         /* No right-hand children.  Everything down and left is
 426            smaller than us, so any 'next' node must be in the general
 427            direction of our parent. Go up the tree; any time the
 428            ancestor is a right-hand child of its parent, keep going
 429            up. First time it's a left-hand child of its parent, said
 430            parent is our 'next' node. */
 431         while ((parent = rb_parent(node)) && node == parent->rb_right)
 432                 node = parent;
 433
 434         return parent;
 435 }
 436 EXPORT_SYMBOL(rb_next);
 437
 438 struct rb_node *rb_prev(const struct rb_node *node)
 439 {
 440         struct rb_node *parent;
 441
 442         if (RB_EMPTY_NODE(node))
 443                 return NULL;
 444
 445         /* If we have a left-hand child, go down and then right as far
 446            as we can. */
 447         if (node->rb_left) {
 448                 node = node->rb_left;
 449                 while (node->rb_right)
 450                         node=node->rb_right;
 451                 return (struct rb_node *)node;
 452         }
 453
 454         /* No left-hand children. Go up till we find an ancestor which
 455            is a right-hand child of its parent */
 456         while ((parent = rb_parent(node)) && node == parent->rb_left)
 457                 node = parent;
 458
 459         return parent;
 460 }
 461 EXPORT_SYMBOL(rb_prev);
 462
 463 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 464                      struct rb_root *root)
 465 {
 466         struct rb_node *parent = rb_parent(victim);
 467
 468         /* Set the surrounding nodes to point to the replacement */
 469         if (parent) {
 470                 if (victim == parent->rb_left)
 471                         parent->rb_left = new;
 472                 else
 473                         parent->rb_right = new;
 474         } else {
 475                 root->rb_node = new;
 476         }
 477         if (victim->rb_left)
 478                 rb_set_parent(victim->rb_left, new);
 479         if (victim->rb_right)
 480                 rb_set_parent(victim->rb_right, new);
 481
 482         /* Copy the pointers/colour from the victim to the replacement */
 483         *new = *victim;
 484 }
 485 EXPORT_SYMBOL(rb_replace_node);