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/module.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         if (root->augment_cb) {
  49                 root->augment_cb(node);
  50                 root->augment_cb(right);
  51         }
  52 }
  53
  54 static void __rb_rotate_right(struct rb_node *node, struct rb_root *root)
  55 {
  56         struct rb_node *left = node->rb_left;
  57         struct rb_node *parent = rb_parent(node);
  58
  59         if ((node->rb_left = left->rb_right))
  60                 rb_set_parent(left->rb_right, node);
  61         left->rb_right = node;
  62
  63         rb_set_parent(left, parent);
  64
  65         if (parent)
  66         {
  67                 if (node == parent->rb_right)
  68                         parent->rb_right = left;
  69                 else
  70                         parent->rb_left = left;
  71         }
  72         else
  73                 root->rb_node = left;
  74         rb_set_parent(node, left);
  75
  76         if (root->augment_cb) {
  77                 root->augment_cb(node);
  78                 root->augment_cb(left);
  79         }
  80 }
  81
  82 void rb_insert_color(struct rb_node *node, struct rb_root *root)
  83 {
  84         struct rb_node *parent, *gparent;
  85
  86         if (root->augment_cb)
  87                 root->augment_cb(node);
  88
  89         while ((parent = rb_parent(node)) && rb_is_red(parent))
  90         {
  91                 gparent = rb_parent(parent);
  92
  93                 if (parent == gparent->rb_left)
  94                 {
  95                         {
  96                                 register struct rb_node *uncle = gparent->rb_right;
  97                                 if (uncle && rb_is_red(uncle))
  98                                 {
  99                                         rb_set_black(uncle);
 100                                         rb_set_black(parent);
 101                                         rb_set_red(gparent);
 102                                         node = gparent;
 103                                         continue;
 104                                 }
 105                         }
 106
 107                         if (parent->rb_right == node)
 108                         {
 109                                 register struct rb_node *tmp;
 110                                 __rb_rotate_left(parent, root);
 111                                 tmp = parent;
 112                                 parent = node;
 113                                 node = tmp;
 114                         }
 115
 116                         rb_set_black(parent);
 117                         rb_set_red(gparent);
 118                         __rb_rotate_right(gparent, root);
 119                 } else {
 120                         {
 121                                 register struct rb_node *uncle = gparent->rb_left;
 122                                 if (uncle && rb_is_red(uncle))
 123                                 {
 124                                         rb_set_black(uncle);
 125                                         rb_set_black(parent);
 126                                         rb_set_red(gparent);
 127                                         node = gparent;
 128                                         continue;
 129                                 }
 130                         }
 131
 132                         if (parent->rb_left == node)
 133                         {
 134                                 register struct rb_node *tmp;
 135                                 __rb_rotate_right(parent, root);
 136                                 tmp = parent;
 137                                 parent = node;
 138                                 node = tmp;
 139                         }
 140
 141                         rb_set_black(parent);
 142                         rb_set_red(gparent);
 143                         __rb_rotate_left(gparent, root);
 144                 }
 145         }
 146
 147         rb_set_black(root->rb_node);
 148 }
 149 EXPORT_SYMBOL(rb_insert_color);
 150
 151 static void __rb_erase_color(struct rb_node *node, struct rb_node *parent,
 152                              struct rb_root *root)
 153 {
 154         struct rb_node *other;
 155
 156         while ((!node || rb_is_black(node)) && node != root->rb_node)
 157         {
 158                 if (parent->rb_left == node)
 159                 {
 160                         other = parent->rb_right;
 161                         if (rb_is_red(other))
 162                         {
 163                                 rb_set_black(other);
 164                                 rb_set_red(parent);
 165                                 __rb_rotate_left(parent, root);
 166                                 other = parent->rb_right;
 167                         }
 168                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 169                             (!other->rb_right || rb_is_black(other->rb_right)))
 170                         {
 171                                 rb_set_red(other);
 172                                 node = parent;
 173                                 parent = rb_parent(node);
 174                         }
 175                         else
 176                         {
 177                                 if (!other->rb_right || rb_is_black(other->rb_right))
 178                                 {
 179                                         rb_set_black(other->rb_left);
 180                                         rb_set_red(other);
 181                                         __rb_rotate_right(other, root);
 182                                         other = parent->rb_right;
 183                                 }
 184                                 rb_set_color(other, rb_color(parent));
 185                                 rb_set_black(parent);
 186                                 rb_set_black(other->rb_right);
 187                                 __rb_rotate_left(parent, root);
 188                                 node = root->rb_node;
 189                                 break;
 190                         }
 191                 }
 192                 else
 193                 {
 194                         other = parent->rb_left;
 195                         if (rb_is_red(other))
 196                         {
 197                                 rb_set_black(other);
 198                                 rb_set_red(parent);
 199                                 __rb_rotate_right(parent, root);
 200                                 other = parent->rb_left;
 201                         }
 202                         if ((!other->rb_left || rb_is_black(other->rb_left)) &&
 203                             (!other->rb_right || rb_is_black(other->rb_right)))
 204                         {
 205                                 rb_set_red(other);
 206                                 node = parent;
 207                                 parent = rb_parent(node);
 208                         }
 209                         else
 210                         {
 211                                 if (!other->rb_left || rb_is_black(other->rb_left))
 212                                 {
 213                                         rb_set_black(other->rb_right);
 214                                         rb_set_red(other);
 215                                         __rb_rotate_left(other, root);
 216                                         other = parent->rb_left;
 217                                 }
 218                                 rb_set_color(other, rb_color(parent));
 219                                 rb_set_black(parent);
 220                                 rb_set_black(other->rb_left);
 221                                 __rb_rotate_right(parent, root);
 222                                 node = root->rb_node;
 223                                 break;
 224                         }
 225                 }
 226         }
 227         if (node)
 228                 rb_set_black(node);
 229 }
 230
 231 void rb_erase(struct rb_node *node, struct rb_root *root)
 232 {
 233         struct rb_node *child, *parent;
 234         int color;
 235
 236         if (!node->rb_left)
 237                 child = node->rb_right;
 238         else if (!node->rb_right)
 239                 child = node->rb_left;
 240         else
 241         {
 242                 struct rb_node *old = node, *left;
 243                 int old_parent_cb = 0;
 244                 int successor_parent_cb = 0;
 245
 246                 node = node->rb_right;
 247                 while ((left = node->rb_left) != NULL)
 248                         node = left;
 249
 250                 if (rb_parent(old)) {
 251                         old_parent_cb = 1;
 252                         if (rb_parent(old)->rb_left == old)
 253                                 rb_parent(old)->rb_left = node;
 254                         else
 255                                 rb_parent(old)->rb_right = node;
 256                 } else
 257                         root->rb_node = node;
 258
 259                 child = node->rb_right;
 260                 parent = rb_parent(node);
 261                 color = rb_color(node);
 262
 263                 if (parent == old) {
 264                         parent = node;
 265                 } else {
 266                         successor_parent_cb = 1;
 267                         if (child)
 268                                 rb_set_parent(child, parent);
 269
 270                         parent->rb_left = child;
 271
 272                         node->rb_right = old->rb_right;
 273                         rb_set_parent(old->rb_right, node);
 274                 }
 275
 276                 node->rb_parent_color = old->rb_parent_color;
 277                 node->rb_left = old->rb_left;
 278                 rb_set_parent(old->rb_left, node);
 279
 280                 if (root->augment_cb) {
 281                         /*
 282                          * Here, three different nodes can have new children.
 283                          * The parent of the successor node that was selected
 284                          * to replace the node to be erased.
 285                          * The node that is getting erased and is now replaced
 286                          * by its successor.
 287                          * The parent of the node getting erased-replaced.
 288                          */
 289                         if (successor_parent_cb)
 290                                 root->augment_cb(parent);
 291
 292                         root->augment_cb(node);
 293
 294                         if (old_parent_cb)
 295                                 root->augment_cb(rb_parent(old));
 296                 }
 297
 298                 goto color;
 299         }
 300
 301         parent = rb_parent(node);
 302         color = rb_color(node);
 303
 304         if (child)
 305                 rb_set_parent(child, parent);
 306
 307         if (parent) {
 308                 if (parent->rb_left == node)
 309                         parent->rb_left = child;
 310                 else
 311                         parent->rb_right = child;
 312
 313                 if (root->augment_cb)
 314                         root->augment_cb(parent);
 315
 316         } else {
 317                 root->rb_node = child;
 318         }
 319
 320  color:
 321         if (color == RB_BLACK)
 322                 __rb_erase_color(child, parent, root);
 323 }
 324 EXPORT_SYMBOL(rb_erase);
 325
 326 /*
 327  * This function returns the first node (in sort order) of the tree.
 328  */
 329 struct rb_node *rb_first(const struct rb_root *root)
 330 {
 331         struct rb_node  *n;
 332
 333         n = root->rb_node;
 334         if (!n)
 335                 return NULL;
 336         while (n->rb_left)
 337                 n = n->rb_left;
 338         return n;
 339 }
 340 EXPORT_SYMBOL(rb_first);
 341
 342 struct rb_node *rb_last(const struct rb_root *root)
 343 {
 344         struct rb_node  *n;
 345
 346         n = root->rb_node;
 347         if (!n)
 348                 return NULL;
 349         while (n->rb_right)
 350                 n = n->rb_right;
 351         return n;
 352 }
 353 EXPORT_SYMBOL(rb_last);
 354
 355 struct rb_node *rb_next(const struct rb_node *node)
 356 {
 357         struct rb_node *parent;
 358
 359         if (rb_parent(node) == node)
 360                 return NULL;
 361
 362         /* If we have a right-hand child, go down and then left as far
 363            as we can. */
 364         if (node->rb_right) {
 365                 node = node->rb_right;
 366                 while (node->rb_left)
 367                         node=node->rb_left;
 368                 return (struct rb_node *)node;
 369         }
 370
 371         /* No right-hand children.  Everything down and left is
 372            smaller than us, so any 'next' node must be in the general
 373            direction of our parent. Go up the tree; any time the
 374            ancestor is a right-hand child of its parent, keep going
 375            up. First time it's a left-hand child of its parent, said
 376            parent is our 'next' node. */
 377         while ((parent = rb_parent(node)) && node == parent->rb_right)
 378                 node = parent;
 379
 380         return parent;
 381 }
 382 EXPORT_SYMBOL(rb_next);
 383
 384 struct rb_node *rb_prev(const struct rb_node *node)
 385 {
 386         struct rb_node *parent;
 387
 388         if (rb_parent(node) == node)
 389                 return NULL;
 390
 391         /* If we have a left-hand child, go down and then right as far
 392            as we can. */
 393         if (node->rb_left) {
 394                 node = node->rb_left;
 395                 while (node->rb_right)
 396                         node=node->rb_right;
 397                 return (struct rb_node *)node;
 398         }
 399
 400         /* No left-hand children. Go up till we find an ancestor which
 401            is a right-hand child of its parent */
 402         while ((parent = rb_parent(node)) && node == parent->rb_left)
 403                 node = parent;
 404
 405         return parent;
 406 }
 407 EXPORT_SYMBOL(rb_prev);
 408
 409 void rb_replace_node(struct rb_node *victim, struct rb_node *new,
 410                      struct rb_root *root)
 411 {
 412         struct rb_node *parent = rb_parent(victim);
 413
 414         /* Set the surrounding nodes to point to the replacement */
 415         if (parent) {
 416                 if (victim == parent->rb_left)
 417                         parent->rb_left = new;
 418                 else
 419                         parent->rb_right = new;
 420         } else {
 421                 root->rb_node = new;
 422         }
 423         if (victim->rb_left)
 424                 rb_set_parent(victim->rb_left, new);
 425         if (victim->rb_right)
 426                 rb_set_parent(victim->rb_right, new);
 427
 428         /* Copy the pointers/colour from the victim to the replacement */
 429         *new = *victim;
 430 }
 431 EXPORT_SYMBOL(rb_replace_node);