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 ((parent = rb_parent(node)) && rb_is_red(parent))
  95         {
  96                 gparent = rb_parent(parent);
  97
  98                 if (parent == gparent->rb_left)
  99                 {
 100                         {
 101                                 register struct rb_node *uncle = gparent->rb_right;
 102                                 if (uncle && rb_is_red(uncle))
 103                                 {
 104                                         rb_set_black(uncle);
 105                                         rb_set_black(parent);
 106                                         rb_set_red(gparent);
 107                                         node = gparent;
 108                                         continue;
 109                                 }
 110                         }
 111
 112                         if (parent->rb_right == node) {
 113                                 __rb_rotate_left(parent, root);
 114                                 parent = node;
 115                         }
 116
 117                         rb_set_black(parent);
 118                         rb_set_red(gparent);
 119                         __rb_rotate_right(gparent, root);
 120                         break;
 121                 } else {
 122                         {
 123                                 register struct rb_node *uncle = gparent->rb_left;
 124                                 if (uncle && rb_is_red(uncle))
 125                                 {
 126                                         rb_set_black(uncle);
 127                                         rb_set_black(parent);
 128                                         rb_set_red(gparent);
 129                                         node = gparent;
 130                                         continue;
 131                                 }
 132                         }
 133
 134                         if (parent->rb_left == node) {
 135                                 __rb_rotate_right(parent, root);
 136                                 parent = node;
 137                         }
 138
 139                         rb_set_black(parent);
 140                         rb_set_red(gparent);
 141                         __rb_rotate_left(gparent, root);
 142                         break;
 143                 }
 144         }
 145
 146         rb_set_black(root->rb_node);
 147 }
 148 EXPORT_SYMBOL(rb_insert_color);
 149
 150 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 151                              struct rb_root *root)
 152 {
 153         struct rb_node *other;
 154
 155         while ((!node || rb_is_black(node)) && node != root->rb_node)
 156         {
 157                 if (parent->rb_left == node)
 158                 {
 159                         other = parent->rb_right;
 160                         if (rb_is_red(other))
 161                         {
 162                                 rb_set_black(other);
 163                                 rb_set_red(parent);
 164                                 __rb_rotate_left(parent, root);
 165                                 other = parent->rb_right;
 166                         }
 167                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 168                             (!other->rb_right || rb_is_black(other->rb_right)))
 169                         {
 170                                 rb_set_red(other);
 171                                 node = parent;
 172                                 parent = rb_parent(node);
 173                         }
 174                         else
 175                         {
 176                                 if (!other->rb_right || rb_is_black(other->rb_right))
 177                                 {
 178                                         rb_set_black(other->rb_left);
 179                                         rb_set_red(other);
 180                                         __rb_rotate_right(other, root);
 181                                         other = parent->rb_right;
 182                                 }
 183                                 rb_set_color(other, rb_color(parent));
 184                                 rb_set_black(parent);
 185                                 rb_set_black(other->rb_right);
 186                                 __rb_rotate_left(parent, root);
 187                                 node = root->rb_node;
 188                                 break;
 189                         }
 190                 }
 191                 else
 192                 {
 193                         other = parent->rb_left;
 194                         if (rb_is_red(other))
 195                         {
 196                                 rb_set_black(other);
 197                                 rb_set_red(parent);
 198                                 __rb_rotate_right(parent, root);
 199                                 other = parent->rb_left;
 200                         }
 201                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 202                             (!other->rb_right || rb_is_black(other->rb_right)))
 203                         {
 204                                 rb_set_red(other);
 205                                 node = parent;
 206                                 parent = rb_parent(node);
 207                         }
 208                         else
 209                         {
 210                                 if (!other->rb_left || rb_is_black(other->rb_left))
 211                                 {
 212                                         rb_set_black(other->rb_right);
 213                                         rb_set_red(other);
 214                                         __rb_rotate_left(other, root);
 215                                         other = parent->rb_left;
 216                                 }
 217                                 rb_set_color(other, rb_color(parent));
 218                                 rb_set_black(parent);
 219                                 rb_set_black(other->rb_left);
 220                                 __rb_rotate_right(parent, root);
 221                                 node = root->rb_node;
 222                                 break;
 223                         }
 224                 }
 225         }
 226         if (node)
 227                 rb_set_black(node);
 228 }
 229
 230 void rb_erase(struct rb_node *node, struct rb_root *root)
 231 {
 232         struct rb_node *child, *parent;
 233         int color;
 234
 235         if (!node->rb_left)
 236                 child = node->rb_right;
 237         else if (!node->rb_right)
 238                 child = node->rb_left;
 239         else
 240         {
 241                 struct rb_node *old = node, *left;
 242
 243                 node = node->rb_right;
 244                 while ((left = node->rb_left) != NULL)
 245                         node = left;
 246
 247                 if (rb_parent(old)) {
 248                         if (rb_parent(old)->rb_left == old)
 249                                 rb_parent(old)->rb_left = node;
 250                         else
 251                                 rb_parent(old)->rb_right = node;
 252                 } else
 253                         root->rb_node = node;
 254
 255                 child = node->rb_right;
 256                 parent = rb_parent(node);
 257                 color = rb_color(node);
 258
 259                 if (parent == old) {
 260                         parent = node;
 261                 } else {
 262                         if (child)
 263                                 rb_set_parent(child, parent);
 264                         parent->rb_left = child;
 265
 266                         node->rb_right = old->rb_right;
 267                         rb_set_parent(old->rb_right, node);
 268                 }
 269
 270                 node->__rb_parent_color = old->__rb_parent_color;
 271                 node->rb_left = old->rb_left;
 272                 rb_set_parent(old->rb_left, node);
 273
 274                 goto color;
 275         }
 276
 277         parent = rb_parent(node);
 278         color = rb_color(node);
 279
 280         if (child)
 281                 rb_set_parent(child, parent);
 282         if (parent)
 283         {
 284                 if (parent->rb_left == node)
 285                         parent->rb_left = child;
 286                 else
 287                         parent->rb_right = child;
 288         }
 289         else
 290                 root->rb_node = child;
 291
 292  color:
 293         if (color == RB_BLACK)
 294                 __rb_erase_color(child, parent, root);
 295 }
 296 EXPORT_SYMBOL(rb_erase);
 297
 298 static void rb_augment_path(struct rb_node *node, rb_augment_f func, void *data)
 299 {
 300         struct rb_node *parent;
 301
 302 up:
 303         func(node, data);
 304         parent = rb_parent(node);
 305         if (!parent)
 306                 return;
 307
 308         if (node == parent->rb_left && parent->rb_right)
 309                 func(parent->rb_right, data);
 310         else if (parent->rb_left)
 311                 func(parent->rb_left, data);
 312
 313         node = parent;
 314         goto up;
 315 }
 316
 317 /*
 318  * after inserting @node into the tree, update the tree to account for
 319  * both the new entry and any damage done by rebalance
 320  */
 321 void rb_augment_insert(struct rb_node *node, rb_augment_f func, void *data)
 322 {
 323         if (node->rb_left)
 324                 node = node->rb_left;
 325         else if (node->rb_right)
 326                 node = node->rb_right;
 327
 328         rb_augment_path(node, func, data);
 329 }
 330 EXPORT_SYMBOL(rb_augment_insert);
 331
 332 /*
 333  * before removing the node, find the deepest node on the rebalance path
 334  * that will still be there after @node gets removed
 335  */
 336 struct rb_node *rb_augment_erase_begin(struct rb_node *node)
 337 {
 338         struct rb_node *deepest;
 339
 340         if (!node->rb_right && !node->rb_left)
 341                 deepest = rb_parent(node);
 342         else if (!node->rb_right)
 343                 deepest = node->rb_left;
 344         else if (!node->rb_left)
 345                 deepest = node->rb_right;
 346         else {
 347                 deepest = rb_next(node);
 348                 if (deepest->rb_right)
 349                         deepest = deepest->rb_right;
 350                 else if (rb_parent(deepest) != node)
 351                         deepest = rb_parent(deepest);
 352         }
 353
 354         return deepest;
 355 }
 356 EXPORT_SYMBOL(rb_augment_erase_begin);
 357
 358 /*
 359  * after removal, update the tree to account for the removed entry
 360  * and any rebalance damage.
 361  */
 362 void rb_augment_erase_end(struct rb_node *node, rb_augment_f func, void *data)
 363 {
 364         if (node)
 365                 rb_augment_path(node, func, data);
 366 }
 367 EXPORT_SYMBOL(rb_augment_erase_end);
 368
 369 /*
 370  * This function returns the first node (in sort order) of the tree.
 371  */
 372 struct rb_node *rb_first(const struct rb_root *root)
 373 {
 374         struct rb_node  *n;
 375
 376         n = root->rb_node;
 377         if (!n)
 378                 return NULL;
 379         while (n->rb_left)
 380                 n = n->rb_left;
 381         return n;
 382 }
 383 EXPORT_SYMBOL(rb_first);
 384
 385 struct rb_node *rb_last(const struct rb_root *root)
 386 {
 387         struct rb_node  *n;
 388
 389         n = root->rb_node;
 390         if (!n)
 391                 return NULL;
 392         while (n->rb_right)
 393                 n = n->rb_right;
 394         return n;
 395 }
 396 EXPORT_SYMBOL(rb_last);
 397
 398 struct rb_node *rb_next(const struct rb_node *node)
 399 {
 400         struct rb_node *parent;
 401
 402         if (RB_EMPTY_NODE(node))
 403                 return NULL;
 404
 405         /* If we have a right-hand child, go down and then left as far
 406            as we can. */
 407         if (node->rb_right) {
 408                 node = node->rb_right;
 409                 while (node->rb_left)
 410                         node=node->rb_left;
 411                 return (struct rb_node *)node;
 412         }
 413
 414         /* No right-hand children.  Everything down and left is
 415            smaller than us, so any 'next' node must be in the general
 416            direction of our parent. Go up the tree; any time the
 417            ancestor is a right-hand child of its parent, keep going
 418            up. First time it's a left-hand child of its parent, said
 419            parent is our 'next' node. */
 420         while ((parent = rb_parent(node)) && node == parent->rb_right)
 421                 node = parent;
 422
 423         return parent;
 424 }
 425 EXPORT_SYMBOL(rb_next);
 426
 427 struct rb_node *rb_prev(const struct rb_node *node)
 428 {
 429         struct rb_node *parent;
 430
 431         if (RB_EMPTY_NODE(node))
 432                 return NULL;
 433
 434         /* If we have a left-hand child, go down and then right as far
 435            as we can. */
 436         if (node->rb_left) {
 437                 node = node->rb_left;
 438                 while (node->rb_right)
 439                         node=node->rb_right;
 440                 return (struct rb_node *)node;
 441         }
 442
 443         /* No left-hand children. Go up till we find an ancestor which
 444            is a right-hand child of its parent */
 445         while ((parent = rb_parent(node)) && node == parent->rb_left)
 446                 node = parent;
 447
 448         return parent;
 449 }
 450 EXPORT_SYMBOL(rb_prev);
 451
 452 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 453                      struct rb_root *root)
 454 {
 455         struct rb_node *parent = rb_parent(victim);
 456
 457         /* Set the surrounding nodes to point to the replacement */
 458         if (parent) {
 459                 if (victim == parent->rb_left)
 460                         parent->rb_left = new;
 461                 else
 462                         parent->rb_right = new;
 463         } else {
 464                 root->rb_node = new;
 465         }
 466         if (victim->rb_left)
 467                 rb_set_parent(victim->rb_left, new);
 468         if (victim->rb_right)
 469                 rb_set_parent(victim->rb_right, new);
 470
 471         /* Copy the pointers/colour from the victim to the replacement */
 472         *new = *victim;
 473 }
 474 EXPORT_SYMBOL(rb_replace_node);