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